DEVICE FOR DETERMINING THE ELECTRICAL POTENTIAL OF THE BRAIN

Description

Domaine technique

[0001] The invention relates to the field of devices for determining a physiological or psychic state of a mammal, in particular devices for determining such a state by measuring an electroencephalogram (EEG) signal. Arrière-plan technologique

[0002] An intra-aural device for measuring human biological data is known, such as the one described in US 2018 / 0235540. This device includes an interchangeable part designed to be inserted into an ear canal, equipped on its outer surface with electrodes intended to detect an electrical signal from the heart. The device also includes a housing, on which is mounted an external electrode designed to receive a finger of the user to establish a reference potential.

[0003] Replacing the interchangeable part of these devices is cumbersome and complex. Finally, the detection of electrical signals by the electrodes can lack precision.

[0004] US2798210A discloses a sliding ring assembly for transmitting electric current between rotating components. US2019192077A1 discloses a detection system for detecting electrical signals in accordance with the preamble of claim 1. Résumé

[0005] One idea behind this invention is to provide a biological data measurement device that is easier to operate and more likely to provide more accurate signals.

[0006] To this end, the invention proposes a device allowing, for example, the determination of a physiological or psychological state of a mammal.

[0007] A device according to the invention conforms to independent claim 1 or to independent claim 6.

[0008] According to advantageous embodiments, such a device may have one or more of the following characteristics.

[0009] According to the invention, each of the first electrical tracks, or each of the second electrical tracks, has an annular shape having as its axis said axis of revolution and is arranged in electrical contact with one of said first electrical tracks, or one of said second electrical tracks, independently of the orientation of the tip around said axis of revolution, and said first or second annular electrical tracks being spaced along said axis of revolution.

[0010] Such a device is advantageous because it allows the electrode tip to be removed and replaced with another tip in any circumferential orientation without requiring guide wires to connect the electrodes to the processing unit. This makes the device less complex to operate. Another advantage of using circular tracks is that they allow the electrodes to rotate around the axis of revolution. The tip's orientation can therefore be easily adjusted, if necessary, so that one or more electrodes are directed towards a specific area around the ear canal. The signals captured by the electrodes can thus be more targeted, allowing for a more precise determination of the mammal's physiological or psychological state.

[0011] The electrodes of the device can be made in many ways. In one embodiment, at least one electrode has an external portion extending longitudinally, in the direction of the axis of revolution, from the outer surface of the tip. In another embodiment, the electrodes are spaced circumferentially around the axis of revolution.

[0012] According to one embodiment, at least one electrode has a length equal to or slightly less than the length of the tip.

[0013] According to at least one embodiment, an electrode has an internal part extending over a part of the cylindrical channel to form a first electrical track.

[0014] According to one embodiment, the electrodes are spaced apart from each other in a circumferential direction by a constant distance.

[0015] In one embodiment, each of the second electrical tracks is annular, and each of the first electrical tracks is configured to make contact with a respective second annular electrical track. In one embodiment, the first electrical tracks extend in an arc around the inner part of the cylindrical channel around the axis of revolution. In one embodiment, the first electrical tracks form a metallic deposit on the cylindrical channel of the tip.

[0016] In another embodiment, each of the first electrical tracks is annular, and each of the second electrical tracks forms a contact pad configured to make contact with a respective first annular electrical track. In one embodiment, the contact pad extends along an arc of the cylindrical portion of the main body around the axis of revolution. In an alternative embodiment, the contact pad has a rectangular, hemispherical, annular, or semi-annular shape. In one embodiment, the contact pad is a metallic deposit on the outer surface of the cylindrical portion or channel of the nozzle.

[0017] The device tips can be made in different configurations. In one embodiment, the tip is made of elastic material configured to adapt to a dimension, in particular a circumference, of the ear canal so as to ensure contact between the electrodes and the internal surface of the ear canal.

[0018] According to one embodiment, the tip comprises a polymer material and at least one electrode comprises a conductive fabric embedded or embedded in the polymer material of the tip.

[0019] According to an alternative embodiment, the tip comprises a polymer material and at least one electrode comprises a conductive material selected from conductive polymers and nanoparticle-doped silicone, embedded or embedded in the polymer material of the tip.

[0020] According to another embodiment, the tip comprises a polymer material including a plurality of electrically insulated conductive parts forming the electrodes.

[0021] According to one embodiment, the device includes means for locking the tip onto the cylindrical part of the main body.

[0022] According to one embodiment, these locking means comprise a groove and / or a rib and / or a stop arranged in the cylindrical part of the main body and / or in the end piece.

[0023] In one embodiment, the device comprises processing means including a measuring apparatus for measuring physical quantities in the electrical signals captured by the reference electrode and at least one measuring electrode. These physical quantities are, for example, the intensity or voltage of the signals captured by the electrodes.

[0024] In one embodiment, the processing means are configured to amplify the electrical signals captured by the electrodes before transmission to the measuring device. In another embodiment, this amplification is achieved using an impedance matching device.

[0025] According to the invention, the calculation means is configured to determine the physiological or psychological state based on at least one difference between the electrical signal captured by one of the measuring electrodes and the electrical signal captured by the reference electrode. In one embodiment, any artifacts present on these signals are removed using a multi-channel artifact removal method, for example, independent component analysis. In another embodiment, the difference(s) between the electrical signal captured by one of the measuring electrodes and the electrical signal captured by the reference electrode are quantified as a potential difference. In yet another embodiment, the calculation means determines this potential difference from the signal voltage measured by the measuring device.

[0026] In one embodiment, the measuring device allows for the measurement of physical quantities in the electrical signal received by the reference electrode, thanks to at least one first resistor through which flows a current corresponding to the sum of a current corresponding to the electrical signal received by the reference electrode and a current from a reference generator having known characteristics. In one embodiment, the at least one resistor may be a single resistor or an electrical circuit consisting of several resistors. In another embodiment, the electrical circuit of several resistors may be a series circuit. The physical characteristics of the electrical signal received by the reference electrode can be determined by applying Ohm's law to the resistor if it is a single resistor, or by applying a voltage divider formula if considering an electrical circuit of resistors.In this embodiment, the value of the resistance or resistances used is known.

[0027] In one embodiment, the generator is a current generator. In an alternative embodiment, the generator is a voltage generator. The physical characteristics of the electrical signal captured by the reference electrode can be determined by applying Ohm's law to the resistor. In one embodiment, the generator supplying the resistor delivers a voltage current that is considerably high (in absolute value) compared to the expected voltage variations in the signal captured by the reference electrode. An advantage of this embodiment is the ability to detect the presence of outliers. This embodiment is particularly advantageous for calculating the potential difference between a signal captured by a measuring electrode and a signal captured by the reference electrode, according to the embodiment below.

[0028] In an advantageous embodiment, the measuring device allows for the measurement of physical quantities in the electrical signal received by at least one measuring electrode, thanks to at least one second resistor through which flows a current corresponding to the sum of a current corresponding to the electrical signal received by the at least one measuring electrode and a current from a second generator having known characteristics and delivering a voltage higher than that delivered by the reference generator. In one embodiment, the at least one resistor may be a single resistor or an electrical circuit consisting of several resistors. In another embodiment, the electrical circuit of several resistors may be a series circuit.The physical characteristics of the electrical signal captured by the reference electrode can be determined by applying Ohm's law to the resistance if it is a single resistor, or by applying a voltage divider formula if considering an electrical circuit of resistors. In one embodiment, the voltage delivered by the second generator is positive and considerably higher than the voltage variations expected in the signal from a measuring electrode.

[0029] This advantageous embodiment makes it easy to identify outliers. Indeed, in this embodiment, it is expected that the potential difference between the voltage of the signal measured by a measuring electrode and the voltage of the signal measured by the reference electrode will fluctuate very little around half the sum of the voltage supplying at least one resistor used to measure the voltage of the signal captured by the measuring electrode and the voltage supplying at least one resistor used to measure the voltage of the signal captured by the reference electrode.For example, if the resistor (or series resistor) used to measure the voltage of the signal picked up by the measuring electrode is supplied with a voltage of 2.4 V, and if the resistor (or series resistor) used to measure the voltage of the signal picked up by the measuring electrode is supplied with a voltage close to 0 V (for example, on the order of 0.1 V), and if the voltage fluctuation in the signal picked up by the electrodes is expected to be around 1 µV, the resulting potential difference should be around 1.2 V, with fluctuations on the order of 1 µV. Any measurement that deviates significantly from this value, for example by a few mV, can be considered an outlier.

[0030] In one embodiment, the tip is designed to make contact with a specific part of the ear canal when inserted into the ear canal, and the ground electrode is located on a portion of the tip in contact with this specific part of the ear canal in order to capture an electrical signal from said specific part of the ear canal. In one embodiment, the specific part of the ear canal is the tragus of a mammal. In the case of a human, the tragus is a cartilage of the ear located at the entrance to the ear canal.

[0031] In one embodiment, noise reduction is achieved using a common-mode rejection circuit. This embodiment is advantageous because it allows for the reduction of noise originating from disturbances external to the mammal's body.

[0032] In the device according to claim 6, the ground electrode is connected to a potential corresponding to half the sum of the voltages delivered by two voltage generators, for example, the two generators of the measuring instrument. This embodiment is advantageous because it allows for a uniform zero potential to be defined throughout the entire circuit.

[0033] According to one embodiment, the processing means comprise a first resistor connected to a first voltage generator and arranged to receive the electrical signal captured by the reference electrode and a second resistor connected to a second voltage generator and arranged to receive the electrical signal captured by at least one measuring electrode, the second voltage generator delivering a voltage higher than that delivered by the first voltage generator.

[0034] In the embodiment involving a ground electrode, the reference electrode and the measuring electrodes can be chosen from electrodes other than the ground electrode.

[0035] In one embodiment, particularly in the absence of a ground electrode, one of the electrical signals is a reference electrical signal; preferably, this is a substantially stable electrical signal. In other words, the reference electrode is defined as the one receiving a substantially stable electrical signal.

[0036] In one embodiment, the reference electrical signal is measured by an electrode, namely the reference electrode, which is intended to be directed towards a bony part near the mammal's auditory canal. In particular, this bony part is a mastoid.

[0037] One advantage of such an arrangement is to obtain a stable reference signal, i.e. one that fluctuates little, without requiring the use of an external electrode to the tip.

[0038] In one embodiment, the tip has a marking configured to visually identify the reference electrode. In another embodiment, the reference electrode is connected to a predefined potential.

[0039] In one embodiment, the predefined potential corresponds to half the sum of the voltages delivered by the two aforementioned voltage generators. In another embodiment, the reference electrode, thus connected, is placed on the tip so as to be in contact with the surface of the mammal's ear canal. This embodiment is advantageous because it allows the skin to be artificially electrified by transmitting to it the potential to which the reference electrode is connected (since the reference electrode is connected to a certain potential and is also adhered to the surface of the ear canal). This increases the stability of the signal captured by the reference electrode at the surface of the ear canal where it is attached. Indeed, the signal from this part of the ear canal is then expected to fluctuate slightly around this potential, while remaining considerably stable.

[0040] In some embodiments, the earpiece includes means for determining the reference electrical signal. In one embodiment, the earpiece has a marking, preferably on its outer surface, configured to point towards the mammal's mastoid process when the earpiece is inserted into the mammal's ear canal, such that one of the electrodes is directed towards the mammal's mastoid process. In other words, this marking indicates how to orient one of the electrodes towards a bony part near the mammal's ear canal, in particular, the mastoid process.

[0041] According to an alternative embodiment, the reference signal is automatically detected by means of a selector. In particular, the selector is configured to receive the electrical signals from the electrodes and to detect a reference electrode, said reference electrode being selected as the electrode emitting the electrical signal having the most stable electrical potential, that is to say the one exhibiting the fewest fluctuations, among the electrical signals received by the electrodes.

[0042] In one embodiment, the signal selector is arranged upstream of the computing means and connected to the second electrical tracks. In another embodiment, the selector is connected to an amplifier having a negative input and at least one positive input, and in which the signal selected by the selector is routed to the negative input of the amplifier. In particular, the amplifier is connected to the computing means.

[0043] In one embodiment, the selector consists of a branching mechanism, for example, a reversible connector arranged upstream of the amplifier, and a signal tester arranged downstream of the amplifier. The reversible connector can be capable of connecting each of the second electrical traces to an input of the amplifier, and the signal tester can be configured to determine the sign of the difference(s) between the signal from at least one positive input and the signal from the negative input. The selector can be configured to route the output signals of the amplifier to the computing means upon detection by the signal tester that all the differences are positive.The selector can also be configured to modify the reversible connector configuration so as to connect another of the second tracks to the negative input of the amplifier in response to the signal tester's detection of at least one negative difference among calculated differences. In this embodiment, the most stable electrical signal is the one with the lowest electrical potential.

[0044] According to one embodiment, at least one of the electrodes is oriented towards a temporal lobe of the mammal.

[0045] According to one embodiment, the physiological or psychic state is related to an electrical activity of an organ of the mammal selected from the group consisting of a brain, a heart, a nerve, a muscle and an eye.

[0046] According to one embodiment, the physiological or psychic state is related to an EEG signal determined by the calculation means from at least one electrical signal emitted by an area of ​​the mammalian brain and captured by one or more of the electrodes arranged in the auditory canal.

[0047] According to one embodiment, the physiological or psychological state is mammalian fatigue, mammalian attention level, or mammalian epileptic seizure.

[0048] According to one embodiment, the psychic state is a pre-ictal activity of the brain.

[0049] According to one embodiment, the device includes a means for filtering electrical signals configured to attenuate spurious signals detected by one of said electrodes. Such spurious signals may be generated by movement of the mammal and / or of the tip in the ear canal and / or originate from the environment of the device.

[0050] According to one embodiment, the filtering means includes a bandpass filter having a bandwidth between 0.3 Hz and 50 Hz, in particular between 1 Hz and 40 Hz.

[0051] According to one embodiment, the calculation method is configured to: determine a mammalian electroencephalogram signal based on measured electrical signals, determine an amplitude of at least one brain wave within a predefined frequency range based on said electroencephalogram signal, and determine a mental state based on said amplitude of at least one brain wave by comparing said amplitude to a predetermined threshold.

[0052] One application of the device is the detection of drowsiness in a person and the use of this detection to trigger a wake-up for the person.

[0053] In one embodiment, the main body includes a wired or wireless data transmission means configured to communicate with the computing means. The transmission means is configured to transmit the electrical signals received by the electrodes to the computing means.

[0054] According to one embodiment, the main body is an electrically insulating box comprising the means for transmitting data to the computing means and the means for processing the signal.

[0055] According to one embodiment, the device comprises a single earpiece.

[0056] According to an alternative embodiment, the device comprises two earpieces. The earpieces are either identical or different.

[0057] According to a corresponding embodiment, the device comprises two auricles configured to be arranged respectively in a first auditory canal of the mammal and a second auditory canal of the mammal, and intended to transmit respective electrical signals to a computing means. In particular, the computing means is intended to determine the physiological or psychological state based on a signal measured by an electrode of the auricle arranged in the first auditory canal and a signal measured by an electrode of the auricle arranged in the second auditory canal, notably based on a difference between the two signals.

[0058] Thus, in one embodiment, at least one difference between two signals captured respectively in the auditory canal of a left ear and a right ear of the mammal is exploited.

[0059] According to one embodiment, the computing means is arranged at a distance from the main body.

[0060] According to a corresponding embodiment, the device comprises a single means of calculation.

[0061] According to another embodiment, the computing means is arranged in the main body of an auricle.

[0062] According to a corresponding embodiment, each earpiece includes a computing means. Brève description des figures

[0063] The invention will be better understood, and other objects, details, features and advantages thereof will become more apparent from the following description of several particular embodiments of the invention, given solely by way of illustration and not limitation, with reference to the accompanying drawings. [ fig.1 ] there figure 1 is a side view of a device according to a first embodiment of the invention. fig.2 ] there figure 2 is a view of the inside of the device in the plane of the figure 1 . [ fig. 3 ] THE figures 3a et 3b are respectively a top view and a three-dimensional cross-sectional view of the upper part of a tip of the figure 3a and can be used in the device of the figure 1 . [ fig. 4 ] There figure 4 is a cross-sectional view of a device according to a second embodiment of the invention. fig. 5 ] there figure 5 is a representative diagram of means for processing an electrical signal that can be used in a device according to an embodiment of the invention. fig. 6 ] there figure 6 is a representative diagram of a device according to a third embodiment of the invention. fig. 7 ] there figure 7 is a representative diagram of a data processing method that can be implemented by a computing means of the device according to an embodiment of the invention. fig. 8 ] THE figures 8a et 8b These are representative diagrams of two embodiments of an automatic signal selector. fig. 9 ] There figure 9 is a perspective view of a tip incorporating electrodes according to another embodiment. fig. 10 ] There figure 10 is a top view of the tip of fig 9. fig. 11 ] There figure 11 is a functional electrical diagram of an atrium according to an embodiment connected to the mammalian brain. fig. 12 ] There figure 12 is a functional electrical diagram of an atrium according to another embodiment connected to the mammalian brain. Description des modes de réalisation

[0064] On the figures 1 et 2 , a first embodiment of a device for determining a psychic or physiological state of a mammal, in particular a person, is represented.

[0065] Device 100 is intended for determining electroencephalogram (EEG) data from a person. Device 100 comprises an earpiece, for example, similar in shape and size to an earphone, including a housing 102 and a removable earpiece 104.

[0066] In the figure 1 The device is viewed from the side, so the parts located outside of it are visible, while internal or invisible parts are represented by dotted lines. In the figure 2 , the tip 104 is shown in cross-section in the plane of the figure 1 , while the other elements are shown in side view. The elements located inside the housing 102 are shown with dashed lines. The tip 104 comprises a domed portion and a cylindrical channel 112. The domed portion is folded over a cylindrical channel 112, which is only integral with the domed portion at its upper end, as shown in the figure 3b Thus, there is an empty space between the cylindrical channel 112 and the outer surface of the nozzle 104.

[0067] The earpiece 104 is equipped on its outer surface with three electrodes 106 1, 106 2 and 106 3 configured to capture electrical signals in a person's ear canal. The earpiece 104 is a piece of revolution about an axis of revolution 108, and the electrodes are arranged equidistant from each other in a circumferential direction around the earpiece 104. The earpiece 104 is made of an insulating material, for example silicone, and the electrodes 106 are, for example, pieces of conductive fabric embedded in the silicone of the earpiece 104, for example by gluing.

[0068] The dimensions of the 104 tip are designed to fit the ear canal. Furthermore, since the 104 tip is made of silicone, the electrodes 106 are held in contact with the inner wall of the ear canal thanks to the elasticity of the silicone. The 104 tip has a length between 15 mm and 25 mm and a diameter larger than the ear canal diameter, specifically by a percentage between 2% and 5% of the ear canal diameter.

[0069] The housing 102 includes processing means 114 configured to receive the electrical signals captured by the electrodes 106, process these signals, and convert them into digital signals. The processing means 114 are connected to a computing means 115, which can be integrated into the housing 102 or separate from it, to determine EEG data based on the signals processed by the processing means 114. In another embodiment, the processing means 114 can also be arranged outside the housing 102.

[0070] The housing 102 also includes a shaft 110 extending from the housing 102 and having as its axis the axis of revolution 108. The shaft 110 is configured to receive the cylindrical channel 112 formed in the end 104. The shaft 110 is provided with three annular electrical tracks 116 1 , 116 2 and 116 3 respectively connected to the electrodes 106 1 , 106 2 and 106 3. The annular tracks 116 have the axis of revolution 108 as their axis and are arranged at a distance from each other in the direction of the axis of revolution 108. The shaft 110 is made of insulating material, and the electrical tracks 116 are formed by a metallic coating on the shaft 110. The annular tracks 116 are connected to the processing means 114 by electrical wires arranged inside the shaft 110. Each of the annular tracks 1161 and 1163 is connected to an electrode 106 and 1063 by first electrical tracks 1181 and 1183 (the electrical track connecting electrode 1062 to annular track 1162 is not shown in the diagram). figures 1 et 2 ).

[0071] On the figures 3a et 3b , the tip 104 is, respectively, represented according to a top view and a three-dimensional view along a section AA.

[0072] The electrodes 106 extend along the entire length of the tip 104 in the direction of the axis of revolution 108. Furthermore, the electrodes 106 are distributed equidistantly around the axis of revolution 108 on the outer surface of the tip 104. In particular, the electrodes 106 cover approximately 75% of the outer surface of the tip, which is between 50% and 80% of the total outer surface of the tip 104. Other electrode surface distributions are also possible.

[0073] The first electrical tracks 118 are arranged in the tip 104 according to an embodiment shown on the figure 3b The upper part of the tip 104 was shown cut along axis A of the figure 3a Therefore, only two electrodes, 106 1 and 106 2, and two initial electrical tracks, 118 1 and 118 2, are shown. The tip 104 shown in this figure is made using a slide mold, which creates three hollow sections on the convex surface of the tip 104. These hollow sections are designed to receive the electrodes 106, each extending in the form of an initially empty well inside the insulating part of the tip 104. On the figure 3b The wells 1211 and 1212, consisting of a vertical portion extending along a longitudinal part of the cylindrical channel 112 and a horizontal portion extending in an arc, were shown, intended to receive the electrical tracks 1181 and 1182. After molding and solidification of the insulating part, a liquid conductive material is poured into each of these wells 121, thus forming the first electrical tracks 1181, 1182 and 1183, each electrical track then occupying one well 121. The liquid conductive material is poured into the wells until they overflow to fill the hollows on the surface of the domed part of the tip. The liquid conductive material that overflowed into the hollows then solidifies to form the electrodes 106. Since there is no contact between the different hollows and the different wells 121, the respective electrical insulation of the electrodes 106 and the electrical tracks 118 cast inside is ensured.

[0074] Furthermore, the cylindrical channel 112 of the nozzle 104 has on its inner surface a shoulder 120 shown on the figure 3b This one is used to hold the tip on the shaft 110. In one embodiment, this shoulder 120 may be absent.

[0075] In another embodiment not shown in the figures, the first electrical tracks 118 1 , 118 2 and 118 3 are contact pads connected to the electrodes 106 by electrically insulated wires embedded in the surface of the domed part of the tip 104 and on the inner surface of the cylindrical channel 112.

[0076] In particular, the shaft 110 has a diameter slightly smaller than the diameter of the cylindrical channel 112 of the end piece 104, for example smaller by a value between 0.5 mm and 2 mm.

[0077] Since the first electrical tracks 118 are arranged opposite the annular tracks 116, the tip 104 can be rotated around the axis of revolution 108 without risk of interrupting the electrical connection between the electrodes 116 and the processing means 114. Furthermore, replacing the tip 104 is made easier because it is not necessary to use guiding means to ensure the electrical connection when mounting the tip 104 on the shaft 110.

[0078] There figure 4 shows a view similar to the figure 2 according to a second embodiment. Unlike device 100, device 200 of the figure 4 includes a solid tip 220, with a cylindrical channel 112 hollowed inside it. The solid tip 220 further includes three first annular electrical tracks 202 1 , 202 2 and 202 3 arranged in the cylindrical channel 112 and connected to the electrodes 106 1 , 106 2 and 106 3, respectively, by electrically insulated wires embedded in the tip 220, between its surface and the cylindrical channel 112.

[0079] The shaft 110 is provided with three non-annular electrical tracks 204 1, 204 2 and 204 3 spaced apart in the direction of the axis of revolution 108. The non-annular electrical tracks are formed by a metallic deposit extending for example in a semicircle of the shaft around the axis of revolution 108 and projecting towards the solid end piece 220. The non-annular electrical tracks 204 are arranged opposite the annular electrical tracks 202 so as to maintain electrical contact with them.

[0080] The shaft 110 has a groove 208 arranged on the side of the housing 102 and configured to receive a collar 206 provided in the cylindrical channel 112 of the end piece 104. This arrangement makes it possible to block the translation of the solid end piece 220 in the direction of the axis of revolution 108. The shaft 110 also includes a stop 210 having a diameter greater than the diameter of the shaft 110 so as to hold the end piece clamped against the stop 210 to stabilize its position during rotation.

[0081] On the figure 5 We have represented 114 processing means that can be used in device 100 or 200.

[0082] The processing means 114 are configured to receive one or more electrical signals picked up by the electrodes 106. The processing means 114 include an amplifier 302 designed to amplify the amplitude of the electrical signal(s). The gain of the amplifier 302 can be from 12 times to 1000 times. In particular, the processing means 114 include a preamplifier not shown in the diagram. figure 5 The amplifier 302 is connected to an analog-to-digital converter (ADC) 304 configured to digitize the electrical signal(s). The ADC 304 is connected to a digital signal processing module 306 configured to attenuate any unwanted signals picked up by the electrodes. These unwanted signals can be caused by head movement, movement of the electrical wires connected to the device, or the device's environment. This digital signal processing module 306 includes a bandpass filter, as well as signal processing functions, notably a function to remove the linear component of the signal. This linear component is present because the reference electrode is placed inside the ear canal without using a ground connection outside the ear canal.The bandwidth of the bandpass filter 306 is further configured to select electrical signals from a predetermined organ, specifically the brain. For example, the bandwidth of the bandpass filter 306 is between 0.3 Hz and 50 Hz, specifically between 1 Hz and 40 Hz. The bandpass filter 306 is connected to a communication module 308 configured to transmit the signals digitized by the ADC 304 and filtered by the bandpass filter 306 to the processing unit 115, either wired or wirelessly. The digital signal processing module may also include other filters, such as a band-stop filter or notch filter.

[0083] The calculation means 115 of device 100 or 200 is configured to determine an electroencephalogram (EEG) signal based on the electrical signals captured by electrodes 106, specifically the difference between these electrical signals. The calculation means 115 is configured to determine an EEG signal from one of two electrode combinations: 1061, 1062, and 1063. One of these electrodes is chosen as the reference electrode, with respect to which the potential will be calculated. The brain potential is calculated by subtracting the signal captured by the reference electrode from the signal captured by the other electrodes.Despite initial processing of the digital signal to eliminate spurious signals, for example by selecting a frequency corresponding to brainwaves using the previously described filter, artifacts may still be present in the signals. If present, they are identified by comparing the differences between the signals from the other two electrodes with the reference electrode. Indeed, the two signals then exhibit the same spurious components. In particular, this comparison is performed using a multi-channel artifact suppression method, preferably independent component analysis (or . Independent component analysis ) .

[0084] The choice of the reference electrode is made upstream of the calculation method, according to the following three examples.

[0085] In a first example, the reference electrode is identified by means of a marking on the tip 104, allowing it to be positioned towards a bony part of the mammal, for example a mastoid, in order to optimize the stability of the signal, i.e. to minimize its fluctuations, to obtain a substantially stable signal, which can then be used as a reference signal to determine an EEG signal of the mammal.

[0086] In the other two examples, shown on the figures 8a et 8b An automatic signal selector allows the reference signal to be determined.

[0087] In a second example, the reference signal is chosen using a signal selector 310 located upstream of the amplifier 302. This selector 310 selects the most stable signal, that is, the one with the fewest fluctuations. The amplifier 302 has one negative input and two positive inputs, the negative input being intended to receive the reference signal. The signal selected as the most stable is then routed to the negative input of the amplifier 302. Thus, the most stable signal is identified and can be used as a reference for calculating the brain potential.

[0088] In a third example, the second electrical traces 118 and 204 are connected to the amplifier 302 via a tap-off mechanism 311, which allows the selection of the electrical trace to be connected to each input of the amplifier 302. The amplifier 302, as in the previous example, has one negative input and two positive inputs. The selector consists of a tap-off mechanism 311, for example, a reversible connector, and a signal tester 312 located downstream of the amplifier 302. The signal tester 312 is configured to determine the signs of the potential differences between the signals from the positive inputs of the amplifier and the signal from the negative input, which is then temporarily selected as the reference. The signal selected for the negative input must be the one with the lowest potential, as it constitutes the potential reference.The lowest potential is assumed to coincide with the most stable signal. If the signal tester 312 determines that the potential differences between the signals from the amplifier's positive inputs and the signal from the negative input t are all positive, then the signal chosen for the negative input is indeed the most stable, and the amplifier output signals can then be routed to the processing means 115 (first passing through the remaining processing means 114). The signal from the amplifier's negative input will be chosen as the potential reference. Otherwise, if at least one of the differences is negative, this means that the signal chosen for the negative input was not the one with the lowest potential. In this case, a feedback loop sends a signal to the branching mechanism 311, which changes the connections of the amplifier inputs 302, and then the test is performed again by the signal tester.The connections are thus modified and the test carried out until the correct configuration, that is to say the one in which the calculated differences are all positive, is found.

[0089] For example, if the electrode chosen as a reference, either manually, according to the first example shown above, or automatically, according to one of the second or third examples shown below, is electrode 106 3, the EEG signal can thus be obtained from signals detected by electrodes 106 1 and 106 3 or electrodes 106 2 and 106 3.

[0090] The earpiece described above can be used alone or in combination with a second earpiece.

[0091] Thus, device 400 of the figure 6 It comprises two earpieces 402 and 402', similar to the earpiece of device 100 or 200. Each earpiece 402 and 402' is fitted with an ear tip 104 and 104' analogous to the ear tip of device 100 or 200. Each ear tip 104 and 104' is arranged in an ear canal 404 and 404' of the person wearing device 400. Unlike devices 100 and 200, the computing means 115 is arranged remotely from the earpieces 402, and the processing means 114 transmit the electrical signals received by the electrodes 106 to the computing means 115 wirelessly. The computing means 115 can also be incorporated into one of the two earpieces.

[0092] The 104 tips are made of elastic material and are sized to ensure contact between the wall of the ear canals and electrodes 106 and 106' respectively of the 104 and 104' tips.

[0093] The computing means 115 is configured to determine an electroencephalogram (EEG) signal based on the electrical signals captured by a combination of two electrodes chosen from the following combinations: 106₁ and 106₃, 106₂ and 106₃, 106₃ and 106₃, 106₁ and 106₃, 106₂ and 106₃. Specifically, the EEG signal is determined by the difference between the two combined signals. As in the case of single-atrial operation, any remaining artifacts in the signal are removed using a multi-channel artifact removal method, preferably independent component analysis.

[0094] In this two-atrial embodiment, the reference electrode is chosen according to one of the examples presented in the one-atrial operating mode. For example, if the chosen reference electrodes are 106 3 and 106'3, the EEG signal can thus be obtained from signals detected by one of the following electrode combinations: 106 1 and 106 3, 106 2 and 106 3, 106' 1 and 106' 3, 106' 2 and 106' 3, 106 1 and 106' 3, 106 2 and 106' 3, 106' 1 and 106 3, and 106' 2 and 106 3.

[0095] There figure 7 represents the steps performed by the calculation means 115 of device 100, 200 or 400 to determine a level of attention of the person wearing device 100, 200 or 400.

[0096] Calculation method 115 is configured to perform: Step 502 to determine an EEG signal based on the difference between two signals captured by two electrodes of the same atrium or of two atria; step 504 to determine a brainwave based on the frequency of the EEG signal. For example, if the signal frequency is between 5 Hz and 15 Hz, particularly 10 Hz, the brainwave is of type α, and if the signal frequency is between 15 Hz and 25 Hz, particularly 20 Hz, the brainwave is of type β. The brainwave can be determined by any signal processing method, particularly by applying a Fourier transform; and step 506 to determine an attention level based on the brainwave. In particular, the attention level is determined based on the amplitude of the brainwave or the ratio between two amplitudes of two brainwaves.For example, for an alpha brainwave, calculation method 115 determines that a person is inattentive when the alpha wave amplitude is below a first predetermined threshold. For a beta brainwave, calculation method 115 determines that a person is inattentive when the beta wave amplitude is below a second predetermined threshold. In particular, calculation method 115 determines the level of attention by comparing the ratio of alpha and beta wave amplitudes to a third predetermined threshold.

[0097] In one embodiment, the computing means 115 may include a step for triggering a wake-up signal intended to wake up the person wearing the device 100, 200 or 400.

[0098] Furthermore, when replacing the tip 104, the new tip 104 can be mounted in any orientation or in a predetermined orientation around the axis of revolution. The electrical connection between the electrodes 106 and the computing means 115 is ensured by the annular tracks 118 or 202, regardless of the tip's orientation relative to the shaft 110.

[0099] THE figures 9 And 10These represent a 700 tip with three electrodes that can be used in the aforementioned 100, 200, and 400 devices. Electrodes 702 and 703, positioned diametrically opposite each other on either side of the cylindrical portion of the tip, correspond to a measuring electrode and a reference electrode, respectively. Electrode 701, positioned further back than the other two, is a ground electrode. Its recessed position relative to the other electrodes allows it to make contact with the tragus. This is made possible by the convex shape of the tip in the part closest to the entrance of the ear canal. Thus, the three electrodes 701, 702, and 703 can be used to perform a measurement, as described below in reference to the figure 11 .

[0100] It is possible to perform several parallel measurements to increase the accuracy of the measurement. Each additional measurement requires an additional electrode (which will be a measuring electrode). To perform two measurements, it is therefore possible to add a measuring electrode to the cylindrical section spaced circumferentially around electrodes 702 and 703.

[0101] There figure 11 Figure 700 represents a schematic diagram of the device's operation when fitted with the tip 700 during use, in contact with the body 630 of a living mammal. In particular, the electrical circuit used to measure the potential difference between the signal received by a measuring electrode and the signal received by a reference electrode is shown. The signals originate from the mammal's brain 600. The mammal could, for example, be a human being.

[0102] On the figure 11 The body 630 is modeled as follows. The brain of mammal 600 is modeled as a voltage generator with internal resistances. The generated voltage is on the order of 100 µV. The internal resistances here consist of the resistance of the head of individual 601 and the resistance of the skin of individual 602. The resistance of the skin of individual 602 constitutes the most significant resistance. This resistance varies between 5 and 100 MΩ. This resistance depends on several parameters that are more or less controllable. The body 630 also contains noise sources. These noise sources are the body's electrical generators (facial muscles, eyes, etc.), but also external disturbances that can inject current into the circuit from time to time. Internal noise generators are modeled by the internal noise generator 608, and noise sources external to the individual are modeled by the external noise generator 609.The individual's body then acts as an antenna, which can be modeled by a capacitance 610, with a variable capacitance depending on the current injected by the external noise generator 609.

[0103] To determine an individual's physiological or psychological state, it is necessary to measure a potential difference in the brain 600, specifically between the positive and negative terminals of the generator that models the brain. A measuring electrode 702 captures an electrical signal at the positive terminal, and a reference electrode 703 captures an electrical signal at the negative terminal. The voltages of both signals are influenced by the resistances of the individual's head 601 and skin 602, as shown in the diagram. Each of these signals is routed to a measuring device 620 included in the aforementioned processing means 114.

[0104] Before reaching the measuring device 620, each of the two signals is amplified by passing through an impedance matching network 603, which provides an amplification of 10 to 12 times. The voltage of the current output from the amplifier is thus on the order of 10 to 100 µV, while the initial signal has a potential on the order of µV. To measure the voltage of the signal picked up by the measuring electrode 702, or by the reference electrode 703 respectively, the measuring device 620 includes an internal resistor 604, or 605 respectively, with an identical known resistance value (in practice, close to 1 GΩ). In one embodiment, the resistor can be a set of resistors connected in series. The measurement is performed according to the principle of a voltmeter. This resistor is connected to a voltage generator 606 generating a potential Vm+, respectively a voltage generator 607 generating a potential Vm-.In practice, a chosen value for the potentials is, for example, Vm+ = 2.4 V and Vm- = 0 V. The signals thus measured are then routed to an operational amplifier 612. The measuring device 620 can be made using an ADS 1292 component available from Texas Instruments.

[0105] This circuit detects outliers when measuring the potential difference between the positive and negative terminals of the generator modeling the 600 brain. The measured potential difference should fluctuate within 10 or 100 µV around 1.2V. A potential difference deviating significantly from this value is declared an outlier. The 603 impedance adapter also helps limit outliers. If any of the obtained signals exceed the range between Vm- and Vm+, the 603 impedance adapter does not amplify the signal, and the measurement is immediately detected as an outlier.

[0106] When calculating the potential difference, it is also necessary to remove measurement noise. In the embodiment shown in the figure 11 The ground electrode 701 is used to suppress noise from external noise sources to the individual, represented by the generator 609. The solution for suppressing the noise is a common mode rejection circuit 621. For this, the ground electrode 701 is connected to the midpoint 611 between the resistors 604 and 605.

[0107] In the adopted model, the effect of this connection is to short-circuit the capacitor 610 by injecting into the circuit a current identical to that generated by the external noise generator 609. This current corresponds to the signal captured by the ground electrode 701 in contact with a very stable area of ​​the auditory canal, in which variations in the electrical signal correspond to variations in external noise. Such a stable area, which allows the capture of the purest possible external noise, is, for example, the tragus, a cartilage located in the ear at the entrance to the auditory canal. In practice, the common-mode rejection circuit 621 is implemented by connecting the ground electrode 701 to a potential corresponding to half the sum of Vm+ and Vm-, so that the zero potential is defined in the same way throughout the circuit. On the figure 11 , it is the midpoint 611 which corresponds to this potential.

[0108] Indeed, it is necessary that the zero potential corresponding to the current used for noise reduction be the same potential around which the measured potential difference fluctuates. With the values ​​given previously, the potential difference fluctuates around 1.2V, therefore the ground electrode 701 must be connected to this 1.2V potential.

[0109] In the implementation of the figure 12 The plurality of electrodes 106 comprises only one measuring electrode 702 and one reference electrode 703. The ground electrode 701 is eliminated. Noise from the generator 609 is suppressed by connecting the reference electrode 703 to the midpoint 611, corresponding to the half-sum of Vm+ and Vm-. In this embodiment, everything behaves as if there were a virtual ground electrode coinciding with the reference electrode 703.

[0110] The applications of such a device 100, 200, or 400 are numerous, particularly in medicine, including the monitoring of patients with neurological diseases, including epilepsy, the screening and diagnosis of neurological diseases, the screening and monitoring of children with attention disorders, but also for the monitoring of certain professionals, including the monitoring of air traffic controllers or pilots in aviation, the monitoring of athletes, or even to improve daily life for example the development of wellness applications.

[0111] Although the invention has been described in connection with several particular embodiments, it is clearly evident that it is by no means limited to them and that it includes all technical equivalents of the means described as well as their combinations if these fall within the scope of the invention as defined by the claims.

[0112] The use of the verb "comporter", "comprendre" or "include" and its conjugated forms does not exclude the presence of other elements or steps than those stated in a claim.

[0113] In claims, any reference sign in parentheses shall not be interpreted as a limitation of the claim.

Claims

1. A device (100, 200, 400) for determining a physiological or psychological state of a mammal, the device (100, 200, 400) comprising at least one earpiece (402) comprising: - a main body (102) comprising a body of revolution (110) having an axis of revolution (108), and - an endpiece (104, 220, 700) configured to be inserted into an ear canal (404), said endpiece (104, 220) having a cylindrical channel (112) intended to receive the body of revolution (110) for detachably mounting the endpiece (104, 220) on the main body (102), the endpiece (104, 220) being arranged to be movable in rotation about the axis of revolution (108) in order to allow at least one electrode (106) to be oriented toward a zone of the brain of the mammal, and said endpiece (104, 220) comprising a plurality of electrodes (106; 701-703) arranged on an outer surface of the endpiece (104, 220), the plurality of electrodes (106) comprising a reference electrode (703) and at least one measuring electrode (702), each electrode (106; 701-703) being configured to pick up an electrical signal in the ear canal of the mammal, and said device comprising first electrical tracks (118, 202) electrically insulated from each other, arranged in the cylindrical channel (112) of the endpiece (104, 220) and connected to the electrodes (106), and second electrical tracks (116, 204) electrically insulated from each other, arranged in the cylindrical part (110) of the main body (102) and intended to convey the electrical signal, picked up by the electrodes (106), to a calculation means (115), in which each of the first electrical tracks, or each of the second electrical tracks, has an annular shape having as its axis said axis of revolution and is arranged in electrical contact with one of said first electrical tracks (118, 202), or one of said second electrical tracks, independently of the orientation of the endpiece about said axis of revolution, and said first electrical tracks (118, 202) or second electrical tracks (116, 204) of annular shape being spaced along said axis of revolution (108) characterized in that the device further comprises processing means (114, 620) including two voltage generators (606, 607), in which the reference electrode (703) is connected to a potential corresponding to half the sum of the voltages delivered by the two voltage generators (606, 607). the device comprising the calculation means (115) configured to determine a physiological or psychological state of a mammal as a function of a difference between the electrical signal picked up by the measuring electrode (702) and the electrical signal picked up by the reference electrode (703).

2. The device (100, 200, 400) as claimed in claim 1, in which the reference electrode is intended to be oriented toward a mastoid of the mammal upon insertion of the endpiece into the ear canal of the mammal.

3. The device (100, 200, 400) as claimed in claim 1 or 2, in which the endpiece (104, 220) has a marking configured for visually recognizing the reference electrode.

4. The device (100, 200, 400) as claimed in any one of claims 1 to 3, in which the electrodes (106, 702, 703) are spaced apart from each other in a circumferential direction about the axis of revolution (108).

5. The device (400) as claimed in claim 1, in which the device (400) comprises two earpieces (402, 402') respectively including the measuring electrode (702) and the reference electrode (703) and configured to be arranged in a first mammalian ear canal (404) and a second mammalian ear canal (404'), respectively, and intended to convey respective electrical signals to the calculation means (115), said calculation means (115) being suitable for determining the physiological or psychological state as a function of the electrical signal picked up by the measuring electrode (702) of the earpiece (402) arranged in the first ear canal (404) and the electrical signal picked up by the reference electrode (703) of the earpiece (402') arranged in the second ear canal (404'), in particular as a function of a difference between the two signals.

6. A device (100, 200, 400) for determining a physiological or psychological state of a mammal, the device (100, 200, 400) comprising at least one earpiece (402) comprising: - a main body (102) comprising a body of revolution (110) having an axis of revolution (108), and - an endpiece (104, 220, 700) configured to be inserted into an ear canal (404), said endpiece (104, 220) having a cylindrical channel (112) intended to receive the body of revolution (110) for detachably mounting the endpiece (104, 220) on the main body (102), the endpiece (104, 220) being arranged to be movable in rotation about the axis of revolution (108) in order to allow at least one electrode (106) to be oriented toward a zone of the brain of the mammal, and said endpiece (104, 220) comprising a plurality of electrodes (106; 701-703) arranged on an outer surface of the endpiece (104, 220), the plurality of electrodes (106) comprising a reference electrode (703), at least one measuring electrode (702) and a ground electrode (701), said ground electrode being oriented toward a specific part of the ear canal, said specific part of the ear canal making it possible to pick up a stable signal, each electrode (106; 701-703) being configured to pick up an electrical signal in the ear canal of the mammal, and said device comprising first electrical tracks (118, 202) electrically insulated from each other, arranged in the cylindrical channel (112) of the endpiece (104, 220) and connected to the electrodes (106), and second electrical tracks (116, 204) electrically insulated from each other, arranged in the cylindrical part (110) of the main body (102) and intended to convey the electrical signal, picked up by the electrodes (106), to a calculation means (115), in which each of the first electrical tracks, or each of the second electrical tracks, has an annular shape having as its axis said axis of revolution and is arranged in electrical contact with one of said first electrical tracks (118, 202), or one of said second electrical tracks, independently of the orientation of the endpiece about said axis of revolution, and said first electrical tracks (118, 202) or second electrical tracks (116, 204) of annular shape being spaced along said axis of revolution (108) characterized in that the device comprises processing means (114, 620) configured to use the signal picked up by the ground electrode (701) to effect a noise reduction in the signals measured by the reference electrode (703) and the at least one measuring electrode (702), the processing means comprising two voltage generators (606, 607), wherein the ground electrode (701) is connected to a potential corresponding to half the sum of the voltages delivered by the two voltage generators (606, 607), the device comprising the calculation means (115) configured to determine a physiological or psychological state of a mammal as a function of a difference between the electrical signal picked up by the measuring electrode (702) and the electrical signal picked up by the reference electrode (703).

7. The device (100, 200, 400) as claimed in claim 6, in which the endpiece (104, 220, 700) is constructed so as to be able to be in contact with the specific part of the ear canal when inserted into the ear canal, and in which the ground electrode (701) is located on a part of the endpiece (104, 220, 700) in contact with the specific part of the ear canal, in order to pick up an electrical signal on said specific part of the ear canal.

8. The device (100, 200, 400) as claimed in either of claims 6 and 7, in which the specific part of the ear canal is a mammalian tragus.

9. The device (100, 200, 400) as claimed in claim 6, in which the processing means comprise a first resistor (605) connected to a first voltage generator (607) and arranged in such a way as to receive the electrical signal picked up by the reference electrode, and a second resistor (604) connected to a second voltage generator (606) and arranged in such a way as to receive the electrical signal picked up by the at least one measuring electrode, the second voltage generator delivering a voltage greater than that delivered by the first voltage generator.

10. The device (100, 200, 400) as claimed in one of claims 1 through 9, comprising a selector configured to receive the electrical signals from the electrodes, said selector being configured to detect a reference electrode, among the electrodes (106), said reference electrode being selected as the electrode emitting the electrical signal having the most stable electrical potential among the electrical signals picked up by the electrodes (106).

11. The device (100, 200, 400) as claimed in any one of claims 1 through 10, in which the main body (102) comprises wired or wireless data transmission means (308) configured to communicate with the calculation means (115).

12. The device (100, 200, 400) as claimed in any one of claims 1 through 11, in which the device comprises a means for filtering the electrical signals, said means being configured to attenuate parasitic signals detected by one or more of said electrodes, in which the filtering means comprises a band-pass filter (306) having a pass band between 0.3 Hz and 50 Hz, in particular between 1 Hz and 40 Hz.

13. The device (100, 200, 400) as claimed in any one of claims 1 through 12, in which the calculation means is configured to: determine an electroencephalogram signal of the mammal as a function of the electrical signals measured, determine an amplitude of at least one brain wave in a predefined frequency range as a function of said electroencephalogram signal, and determine a psychological state as a function of said amplitude of at least one brain wave by comparing said amplitude with a predetermined threshold.

14. The device (100, 200, 400) as claimed in any one of claims 1 through 13, in which the physiological or psychological state relates to an electrical activity of an organ of the mammal, selected from the group consisting of a brain, a heart, a nerve, a muscle and an eye.

15. The device (100, 200, 400) as claimed in any one of claims 1 through 14, in which the physiological or psychological state is mammalian fatigue, a mammalian attention level or a mammalian epileptic seizure.