FR3096252A1 - Robust detection of evoked potentials via a direct neural interface - Google Patents

Abstract

The invention relates to a measure of potential evoked by a user. In particular, we generate a sensory stimulation signal (SIGN) intended to induce an evoked potential with the user, and we collect a measurement of the evoked potential, to compare the evoked potential with the generated signal (SIGN). The sensory stimulation signal (SIGN) is variable in frequency (f1, f2, f3) according to a predetermined variation sequence, such as a pseudo-random sequence. Abstract figure: Figure 3

Description

Description Title of the invention: Robust detection of evoked potentials via a direct neural interface Technical field

The present description relates to the detection of so-called “evoked potential” signals.

[0002] Evoked potentials are reactions of the nervous system of a user reacting to a specific sensory stimulation (or stimulus (a sensory organ).

These evoked potentials are in the form of electrical potentials detectable on an electroencephalogram (EEG).

[0003] The external stimuli can be: visual, auditory, somatosensory (pressure, heat, pain, etc.), or other.

[0004] To evoke these potentials, sources of sensory stimulation emit stimuli at a given frequency.

The user's brain reacting to these stimuli (via an appropriate sensory organ) generates a wave signal corresponding to an encephalogram electrical potential, hereinafter referred to as “EEG” (for electroencephalogram).

It is usually observed that the wave of this EEG signal has a frequency corresponding to that of the stimulus (provided of course that the sensory organ can detect this stimulus frequency: below retinal persistence for sight, in the band audible frequency for hearing, etc.).

100051 In fact, the user's nervous system emits electrical signals of frequencies equivalent to the frequencies of variation of the stimuli, which attest to the reception of the stimuli and the user's reaction to these stimuli.

Possible areas of application for this technology include medical diagnostics and brain-machine control interfaces.

Prior technique

[0006] The current solution consists in specific detection equipment (for example a BCI - Brain-Computer Interface helmet connected to a processing unit) making it possible to detect in EEG signals a fixed frequency emitted by a source of sensory output.

[0007] For example in the case of visual stimulation, a light source can be controlled to flash at a fixed frequency (in steady state).

The blinking causes the generation of an electrical signal detectable by EEG in an occipital lobe of the user.

This same fixed frequency of the light source can then be found in the EEG signal.

[0008] In the state of the art, concerning visual stimulations, this approach is called 2 SSEVP” (for “Steady State Visual Evoked Potential”: visual evoked potential in steady state).

[0009] Similar approaches also exist for evoked potentials for other sensory organs: SSEAP (Stcady State Auditory Evocked Potential), for hearing; -SSSEP (Steady State Somatosensory Evockcd Potential), for the somatosensory system; -SSLEP (Stcady State LASER Evockcd Potential), for sensations relating to pain and heat in response to laser excitation, and which are transmitted by a sub-part of the somatosensory system.

[0010] This solution is tedious to implement because the EEG signals vary greatly from one person to another and vary widely depending on parameters such as fatigue, context, concentration, and others.

In practice, a calibration phase must be used for each user in order to make the detection of evoked potentials robust.

This calibration can last a few minutes and must be repeated in the event of a variation in the experimental conditions (fatigue, context, concentration, etc.).

This calibration phase considerably reduces the interest of the prior art.

[0011] In addition, these solutions require the user to concentrate on the steady-state stimulation for a long time (typically a few seconds) to guarantee that the frequency of the detected signal does not correspond to an artifact, a noise, or a contextual disturbance. .

[0012] Furthermore, this type of detection can be used to form a user interface (typically strongly paralyzed), so that he concentrates his attention on a target flashing at a certain predetermined frequency among several targets flashing at different frequencies. .

Thus, the search for this frequency in his EEG gives the indication of the target watched and, from there, makes it possible to pilot (like a click on an icon) an action corresponding to the watched target.

However, as mentioned above, the user must concentrate on the target for a long time to ensure that the detection of the frequency of the EEG signal is not disturbed by artifact noise or the like.

Summary

The invention improves the situation.

[0014] A method implemented by computer means is proposed, in which at least one sensory stimulation signal is generated intended to induce an evoked potential in a user.

A measurement of the evoked potential is collected, to compare the evoked potential to the generated signal.

[0015] In particular, the sensory stimulation signal is variable in frequency according to a predetermined variation sequence.

Here, the term “sensory stimulation signal” typically means a stimulus whose intensity varies over time.

[0016] Such a method makes it possible, independently of the context of the measurement, to identify in the user evoked potentials resulting from the stimuli induced by following the aforementioned sequence.

This identification is implemented in particular thanks to the frequency characteristics of the predefined sequence of the sensory stimulation signal.

These characteristics are in fact found in the measured signal of the evoked potential in the user.

Thus, an alternating stimulation signal (of the sinusoidal type, in slots or other, as illustrated in FIG. 3 commented on in detail below), has a frequency which changes over time.

These temporal variations of the frequency are found in the same order in the measurement signal of the evoked potential.

[0017] The temporal variation characteristics of the frequency sequence can be modulated to describe a code.

It is then possible to generate a large number of sequences making it possible to code as many distinct stimulation signals, and possibly thus as many human/machine interface commands for example, where the state of the art (SSEVP, or other ) allows only a limited number of stimuli.

[0018] In addition, thanks to such an embodiment, it is possible to discriminate, in the evoked potential measurement signal, the sequence of the stimulation signal, among noise and other artefacts altering the measurement signal.

It is no longer necessary to calibrate a measuring device for each user, or each time the context (fatigue, context, concentration, etc.) changes, which makes it much more acceptable for the user.

[0019]According to one embodiment, the aforementioned sensory stimulation signal follows in particular a pseudo-random sequence.

By "pseudo-random" is meant the fact that the successive frequencies in the stimulation signal are chosen arbitrarily (as well as the duration taken for each frequency in the stimulation signal), but nevertheless, this sequence is kept in memory in order to be subsequently compared with the evoked potential measurement signal Thus, the method comprises: - storage in memory at least of the aforementioned sequence, - determination of a variation in frequency in the measurement of the evoked potential with the user, for estimate a sequence of frequency variation in the evoked potential, and - a comparison of the stored sequence with the estimated sequence.

Such a signal with pseudo-random variations can be identified more easily (for example by correlation or autocorrelation) than a signal comprising a single fixed frequency.

Such a signal is distinguishable from undesirable disturbances, because it is expected to follow a characteristic variation that the disturbances have statistically little chance of following.

[0021] According to one embodiment, an alert signal can be generated in the event of a difference observed between the stored sequence and the estimated sequence, during the aforementioned comparison.

This embodiment makes it possible, in the case of a medical application in particular, to draw the attention of a practitioner to, for example, a dysfunction of the user's body, and thus to assist the practitioner. who must make a diagnosis of this malfunction.

The alert signal can be generated when at least part of the estimated sequence is different from the stored sequence, notwithstanding user concentration on a source generating the stimulation signal.

[0023] In one embodiment, a plurality of sensory stimulation signals are generated from a plurality of respective sensory stimulation sources, and these sensory stimulation signals are variable in frequency according to respective sequences, dc variation each predetermined.

[0024] It is thus possible to have as many sequences as there are sources emitting the stimulation signals.

The advantage of a plurality of sources is to simultaneously present different stimuli to the user.

Such an embodiment is advantageous in the case of an application to a man/machine control interface described below.

However, in a medical application, it can also make it possible to discriminate between different stimuli and to quantify the reactions of the user to each of these stimuli.

It is thus possible to take advantage of the plurality of sources to carry out different tests, for example displaying several squares flashing at different frequencies and especially according to different frequency sequences on a screen simultaneously, and thus evaluating the laterality of the field of vision of a patient after a stroke.

[0026] In the case of a man-machine interface, each source can for example be a flashing light source on which the user can choose to concentrate.

Each light source being linked to a command, the user selects a command associated with a source simply by looking at it.

[0027] In such an embodiment, each sequence is pseudo-random, and the method comprises: -a storage in memory at least of each sequence, -a determination of a variation in frequency in the measurement of the potential evoked from the user, to estimate a sequence of frequency variation in the evoked potential, - a comparison of each stored sequence with the estimated sequence, and - an identification of a stored sequence among the stored sequences as corresponding to the estimated sequence.

Thus, as all the sequences emitted by a plurality of sources are stored in memory, it is possible to determine whether or not a sequence estimated from the measurement of the evoked potential is similar to one of the stored sequences.

It is also possible to know which stored sequence has been detected in this way.

[0029] In addition, the method may comprise, in particular in the application to a man/machine control interface: -a query of a correspondence table between, on the one hand, stored sequences and, on the other hand, command identifiers of at least one piece of equipment, and the sending of a command to at least one piece of equipment, the command sent having an identifier corresponding to the sequence identified from among the stored sequences.

When a stored sequence is identified in an estimated sequence, it is possible to refer to a correspondence table to find the command identifier associated with this sequence.

The command having this identifier is sent to a device to then control its operation.

In a more general embodiment, the comparison of the stored sequence with the estimated sequence can be carried out by correlation (in particular when the sequence is pseudo-random).

The comparison between the estimated sequence and the stored sequence can in fact be carried out to seek, for example, points of resemblance, and therefore statistical correlations (and not a strict equality between the two sequences).

[0032]According to one embodiment, the generated sensory stimulation signal is emitted repeatedly by a source.

In particular, its sequence is successively repeated.

This repetition reduces the risk of false detection compared to a sequence transmitted only once.

In fact, the probability of disturbances affecting all of the transmitted sequences is reduced.

[0034] In addition to the previous embodiment, a guard interval can be provided before repeating a sequence.

The guard interval limits the risk of false detection of another sequence which would be falsely identified, due to a circular permutation between its beginning and its end.

According to another aspect, the invention relates to a computer device comprising a processing circuit configured to implement the method according to any one of the preceding embodiments.

This device can be a medical device as described above.

Alternatively, it may be a man/machine control interface device as also described above.

[0039] The sensory stimulation signal can be a flashing light signal at a variable frequency according to the aforementioned sequence, and the processing circuit comprises a 6 processor configured to drive a display of an icon on a screen with a flashing at a frequency flash that follows this sequence.

The processing circuit may include a signal input interface from at least one neuronal potential signal sensor.

According to another aspect, the invention relates to a computer program comprising instructions for implementing the method, when these instructions are executed by a processor of a processing circuit.

According to another aspect, the invention relates to a non-transitory recording medium readable by a computer on which is recorded a program for the implementation of the method when this program is executed by a processing circuit.

Brief description of the drawings

[0043] Other characteristics, details and advantages will appear on reading the detailed description below, and on analyzing the appended drawings, in which: FIG. 1

[0044] [fig.1] shows a presentation of at least one source of sensory stimulation (here several sources SS1, SS2, SSi.

SSn) according to an exemplary embodiment, in a commonly used environment associated with elements allowing the implementation of the above method.

Fig. 2

[0045] [fig.2] shows different steps of a method according to one embodiment allowing a user UT to transmit at least one OPTi command for action, to a TRD equipment to be controlled, by focusing his attention on the source of SSi sensory stimulation.

Fig. 3

[0046] [fig.3] shows a power signal from a sensory stimulation source SSi according to one embodiment.

Fig. 4

[0047] [fig.4] shows a remote control device DIS according to one embodiment comprising a processing circuit CT and for example an ECR screen containing SSi sources here emitting visual stimuli.

Fig. 5

[0048] shows a medical device according to one embodiment comprising a CT processing circuit and a screen containing at least one SS source emitting visual stimuli for example.

Description of embodiments

Reference is now made to Figure 1 which shows a SYST system according to the invention.

It may comprise a dc processing circuit CT connecting at least: 7 - here, a plurality of SSi sources of sensory stimulation in an application of the device of the invention as a control interface for TRD equipment, - at least one BCI neuronal electrical signal sensor (for example EEG or even MEG for “magnet encephalogram”), and the TRD equipment to be controlled (for example a television set, an installation of window blinds, and/or others).

The user UT here carries at least one neuronal electrical signal sensor BCI.

Nevertheless, preferably the user wears a set of BCI sensors, for example in the form of a helmet placed on the surface of the scalp (helmet called "BCI" for "Brain to Computer Interface" - from the brain to a computer interface) .

[0051] Stimulation of a sensory organ of the user UT, for example a light flash aimed at his eyes, induces a physiological reaction that can be detected by the neuronal electrical signal sensor BCI.

Following the example of a stimulation of the eye of the user UT, it would be a detectable electric potential at the level of the occipital lobe of the user UT (zone of a few centimeters with current technologies).

In the example of Figure 1, the user UT can select a functionality of a TRD equipment (for example increase the sound volume of a television set, change TV channel, etc.), such as a man-machine control interface.

By focusing his attention on a sensory emission source SSi, the user UT commands the functionality OPTi associated with the sequence SEQi emitted by the source SSi.

[0053] Alternatively, following the detection of the EEG signal, it is possible in medical applications: to analyze the received EEG signal and in particular to determine the frequency response of this signal relative to the signal of the stimulus, in order to characterize the functioning (or malfunction) of a part of the UT user's organism.

The EEG signal is thus analyzed relative to the source signal SSi by the processing circuit CT and in this example the equipment TRD can be a medical computing device powered by the processing circuit CT to obtain frequency or frequency deviation data analyzed by the TRD medical device.

Such an embodiment will be described later with reference to Figure 5.

In the example of FIG. 1, for the application of the system to a control interface of TRD equipment, the SSi sources emit sensory stimulations controlled by the processing circuit CT.

The frequency of these sensory stimulations each follows a predetermined and unique periodic sequence SEQi, which can be associated with a command identifier OPTi.

For example, in an embodiment comprising visual stimulation, each source SSi can be a zone 8 of pixels of an ECR screen (of a tablet, smartphone, or other) flashing according to the frequency sequence SEQi.

This zone is associated with an OPTi order identifier.

Alternatively, it is possible to provide LED diodes (“light-ernitting diode”, for light-emitting diode) serving as sources for the visual stimulations.

The user UT receives the stimuli thus generated.

These stimuli produce, in the user UT, a physiological reaction which consists of neuronal electrical signals emitted in the form of potentials by the nervous system of the user UT.

In particular, it is usually observed on a healthy UT user that the frequency of these electrical signals is the same as that of the stimuli.

These electrical signals are commonly referred to as "evoked potentials".

Referring again to the embodiment of Figure 1, the user UT is equipped with a BCI sensor of neural electrical signals (for example a helmet placed on the head).

The sensor BCI measures the evoked potentials of the user, provoked by the stimuli, and delivers measurement signals corresponding to the processing circuit CT.

These measurement signals are referred to below as “EEG signals”.

Each measured signal can indeed be represented by an electroencephalogram.

For this purpose, the sensor can be connected to the processing circuit CT by a wired or wireless connection.

The processing circuit CT then makes it possible to establish the correspondence between the measured EEG signals and for example one of the sequences SEQi emitted by one of the sources SSi of sensory stimulation.

From then on, it is possible to know the SSi source on which the user has focused his attention, and from there, drive an OPTi command corresponding to this source.

For example, a quadriplegic user can simply "pilot" a control interface by brain by focusing his attention on a particular icon of an ECR screen (for example the SSi source), flashing at a frequency or, here according to a sequence of frequencies, well determined.

This frequency (or sequence of frequencies) is recognized by the circuit CT in the EEG signals and the circuit CT sends a corresponding command OPTi to the equipment TRD.

Reference is now made to FIG. 2 to detail the generation of the sources SSi of the stimuli detected by the sensors BCI, and interpreted by the processing circuit CT with a view to controlling the operation of the equipment TRD.

The method below refers to the equipment illustrated in Figure 1 by way of example.

Nevertheless, it is understood that this method can alternatively be implemented by equipment other than that illustrated in figure I.

In step Si, the equipment TRD is in a given state STA, for example a television set receiving a channel CH.

A number of control options are possible for the TRD equipment in the STA state (as illustrated in Figure 4), such as increasing or decreasing the sound volume (respectively SS4 and 9 SS5), incrementing or decrementing the chains received (SS1 and SS2), turn the set on or off (SS3, SS6), etc.

The equipment TRD communicates a message representative of its current state STA to the processing circuit CT.

The circuit CT deduces therefrom possible options, and their respective identifiers OPT1, OPTi, OPTn, to animate a man/machine interface based on the attention of the user UT, for example his gaze.

In step S2 the circuit CT determines for each identifier OPTi a unique sequence SEQi, pscudo-random variable in frequency, as described in detail later with reference to FIG. 3.

Each sequence is predetermined and recorded in a memory MEM of the processing circuit CT.

Each sequence SEQi forms an associated code, in a correspondence table that this memory MEM can also store, with a command identifier OPTi.

[0064] At step S3, the circuit CT can drive a display screen ECR and more particularly graphic areas of the screen to: - display a command logo in each area (typically an icon) and - make this zone flash according to a pseudo-random frequency sequence, specific to an OPTi command.

This flashing icon then constitutes a source of SSi stimulus.

At step S4, the processing circuit CT recovers the user's EEG signals to compare them with each source SSi sequence SEQi (the sensor BCI continuously transmitting the EEG signals to the processing circuit CT).

For example, in step 55, the processing circuit CT determines a period during which the received EEG signal becomes redundant and can thus determine, for example by autocon-elation, the frequency sequence SEQest present in the EEG signal received.

This sequence SEQest consists of successions of durations at respective frequencies as presented below with reference to FIG. 3.

This sequence SEQest is compared in step S6 with all of the sequences SEQI to SEQn emitted by the respective sources SSi.

When one of the frequency sequences SEQi is identified as corresponding to the EEG sequence SEQest, then it is determined that the user UT has focused his attention on the corresponding source SSi step S7.

Of course, to implement steps 55 and 56, it is possible to provide a pseudo-random sequence search processing in frequency, by correlation on different sequence patterns SEQi, and this in a common step.

It is however possible for a user to pay attention to several sources SSi, SSj.

To avoid changing the determination of the source displayed inadvertently, it is possible to repeat steps S4 to S7 a chosen number Rep of times and condition the transmission of the command OPTi associated with the sequence SEQi recognized a number of times Rec for example (Roc greater than 1 and less than or equal to Rcp).

Typically, a sequence SEQest can be tagged a minimum number of times in a timeslot to be considered tagged at step 54.

A counter can count how many times the sequence SEQest has appeared repeatedly, typically lasting a few seconds.

If the counting reaches a fixed threshold Roc at the end of the given time, the OK condition of step S6 can be validated.

In step S7 the processing circuit CT associates with the sequence SEQest the identifier OPTi corresponding to the identified sequence SEQi.

At step SR, the processing circuit CT transmits the identifier command OPTi to the equipment TRD.

Thus, returning again to step S1, the state STA of the equipment TRD is now modified, and the steps S2 and following can be implemented on this new state.

FIG. 3 here presents a signal SION generated by the processing circuit CT.

This signal SION is alternating, here sinusoidal (possibly also in slots, or in triangle), corresponding to the flashes of the visual source SSi.

However, the frequency of these flashes is variable.

The variation of the frequency here follows a predetermined sequence SEQi: the frequency is fixed for a predetermined duration, and then takes another value, also predetermined, and so on.

For example in the case of a visual stimulation, the source SSi flashes according to the following sequence SEQi: -for a predetermined duration t1 (in milliseconds for example), at a predetermined frequency fi, then -for a duration t2 ms at a frequency of 12, and so on until flashing at frequency fN for tN ms.

The frequencies fic (k=N) can be chosen over the entire range of frequencies allowed by the display ECR used.

For example, if the screen has a refresh rate of 100 frames per second, fi to IN are chosen below 100Hz.

Furthermore, the frequency values are usually between two detection limits of the EEG signal, typically between 5Hz and 40Hz for detection by non-invasive sensors.

The durations tk can be chosen to be equal or different.

In practice, they can be of the order of a few hundred milliseconds in order to obtain a visual evoked potential long enough to be detectable by the processing circuit CT in the EEG signals.

The total number N of frequencies can be modified in the same way according to needs and constraints (signal of total duration, reasonable for the desired application).

[0077] It is preferentially avoided that a sequence SEQi emitted by a source SSi be composed of a succession of frequencies which could be found by circular permutation in another sequence SEQj emitted by a source SSj different from the source SSi.

Alternatively, a guard interval can be provided (for example a fixed black display, or an absence of flashing) before any start of sequence SEQi.

Furthermore, each duration of the signal during which its frequency is fixed is chosen arbitrarily.

Furthermore, the successive frequencies taken by the signal do not necessarily have a link between them and are also chosen arbitrarily, so that the values and the durations of the successive frequencies of this signal follow a so-called “pseudo-random” sequence SEQi.

Here, “pseudo-random” means the fact that these durations and frequency values are generated randomly but that these sequences are stored in memory by the processing circuit CT in order to be able to be identified subsequently in the signals delivered by the sensor Bd.

Advantageously, a signal constructed according to a pseudo-random sequence is easier to detect by correlation (or by autocorrelation, by comparison with a database of possible signal patterns), than a signal at a fixed frequency.

It is therefore easier for the processing circuit CT to distinguish the pscudo-random signal among noise and other artefacts in an EEG signal measured by the sensors BCI.

Thus, each sequence SEQi can be recognized in a measured EEG signal as a code characterizing an associated command OPTi.

It is possible to define as many sequences SEQi as constructions of possible frequency combinations during the total time of a sequence SEQi.

These different sequences SEQi can therefore code as many identifiable commands OPTi as possible to control the equipment TRD.

As indicated above, each of these sequences can be detected by con-elation, the robustness of this detection being higher than the simple detection of a signal at a single frequency (but which can be noisy by artefacts).

If this is not the case (no detection of an SEQi sequence), the measured EEG signal is not taken into account (false detection due to noise, an artefact, or the fact that the attention of the user is requested by another object).

11 is now referred to in FIG. 4 to illustrate a device DIS for controlling TRD equipment or several TRD equipment to be controlled from the same interface.

The functionalities can be for example to launch a particular program, to switch on or off the equipment, or other as presented above.

Respective icons SSI to SS6 are displayed for this purpose on the ECR screen with flashing following a frequency sequence specific to each SSi source.

[0082] In particular, it can be appreciated that the number of icons displayed can be large, it being understood that each icon "blinks" according to a natural frequency sequence and which constitutes a code that can be discriminated in a robust manner by the processing circuit. CT.

The DIS device can be a dedicated remote control, or alternatively a connected terminal of the smartphone, tablet or other type, in which a software application is executed to implement the steps of FIG. 2.

For this purpose the device DIS comprises the aforementioned processing circuit CT, which may typically comprise, as illustrated in the example of FIG. 4: - an input interface IN, to receive at least one EEG signal (from of the sensor BCI), - a memory unit MEM for storing at least the sequences SEQi and the identifiers OPTi of associated commands, as well as instruction data of a computer program within the meaning of the invention, - a processor PROC for : * cooperate with the memory MEM, and thus execute the instructions of the program to implement the method according to at least certain steps (S2 to S8) illustrated in FIG. 2, and * control the display on the screen ECR of the icons flashing (SS1 to SS6), - an OUT output interface for sending a command intended for at least one TRD device.

11 is now referred to Figure 5 to illustrate a separate application of an embodiment of a control interface.

This is a medical device MED here comprising an ECR screen displaying a source of visual stimulation SS on a given area of pixels of the ECR screen.

The source SS flashes following a pseudo-random sequence in frequency SEQ.

Such an embodiment already makes it possible to compare in a robust manner the flashing sequence of the source SS with the frequency sequence of the collected EEG signal.

However, here, it is not expected that the frequency succession of the EEG signal follows exactly that of the flashing of the source SS.

A formal recognition step S6 of the sequence SEQest is therefore not carried out as presented previously with reference to FIG. 2.

In this embodiment, the blinking sequence f(SS) and the sequence of the EEG signal f(EEG) (determined in the EEG signal received from the sensor BCI) are sent by an output interface OUT of the device MED intended for SCR equipment making it possible to display, for example, data from the comparison between the two sequences, for the purposes of medical tests.

Alternatively, the flashing sequence f(SS) and the sequence of the EEG signal f(EEG) are compared by the processing circuit CT and in the event of a difference observed, an alert signal can be generated by the output interface OUT to displaying for example intended for a practitioner user, on the SCR screen, data of this observed difference.

[0086] These medical tests can be used to establish a condition report for the UT user, such as loss of visual acuity after head trauma, or after a stroke or in cases of multiple sclerosis.

Possibly, it can be observed for example that high flashing frequencies are no longer perceived by the user, or even that the user does not react to the entire stimulation sequence or other.

Furthermore, in Figure 5, the same references as those of Figure 4 or Figure 1 denote the same elements or equivalent elements.

Of course, the present invention is not limited to the embodiments described above by way of examples; it extends to other variants.

Thus, for example, in the man-machine control interface application, the pixel areas of a screen forming the aforementioned icons can simply be replaced by flashing LED diodes on a box.

More generally, as an alternative to the generation of visual stimuli, in particular in the application of a medical device, other types of source SS can be provided, such as for example: - a loudspeaker generating an audio signal with frequency modulation following a pseudo-random sequence, for stimulation of hearing, - a vibrating object for somatosensory stimulation, or electrical impulses, at a frequency following a pseudo-random sequence, - or, for sensation heat/pain, a LASER source (“Light Amplification by Stimulated Emission of Radiation”, light amplification by stimulated emission of radiation at a frequency following a pseudo-random sequence).

14 [Claim 1] [Claim 2] [Claim 3] [Claim 4] [Claim 5] [Claim 6]

Claims (1)

CLAIMS Process implemented by computer means, in which at least one sensory stimulation signal (SIGN) is generated intended to induce an evoked potential from a user (UT), and a measurement of the evoked potential (EEG) is collected, to compare the evoked potential (EEG) with the generated signal (SIGN), characterized in that the sensory stimulation signal (SIGN) is variable in frequency according to a sequence (SEQi) of predetermined variation. Method according to Claim 1, characterized in that the said sequence is pseudo-random and in that the method comprises: - a storage in memory of at least the said sequence (SEQi), - a determination of a variation in frequency in the measurement of the evoked potential to the user, to estimate a sequence (SEQest) of frequency variation in the evoked potential, and - a comparison of the stored sequence (SEQi) with the estimated sequence (SEQest). Method according to Claim 2, characterized in that it comprises generation of an alert signal in the event of a difference between the stored sequence (SEQi) and the estimated sequence (SEQest). Method according to one of the preceding claims, in which a plurality of sensory stimulation signals are generated from a plurality of respective sources (SSi), characterized in that the said sensory stimulation signals are variable in frequency according to respective sequences (SEQi) each predetermined variation. Method according to Claim 4, characterized in that each sequence is pseudo-random and in that the method comprises: - a storage in memory of at least each sequence (SEQi), - a determination of a variation in frequency in the measurement of the evoked potential to the user, to estimate a sequence (SEQest) of frequency variation in the evoked potential, - a comparison of each stored sequence (SEQ1, , SEQn) with the estimated sequence (SEQest), and - an identification of a sequence stored (SEQi) among the sequences stored as corresponding to the estimated sequence (SEQest). Method according to claim 5, characterized in that it further comprises: [Claim 7] [Claim 8] [Claim 9] [Claim 10] [Claim 11] [Claim 12] [Claim 13] [Claim 14] [ Claim 15] - a query of a correspondence table between, on the one hand, stored sequences (SEQi) and, on the other hand, command identifiers (OPTi) of at least one piece of equipment, - and a transmission a command (OPTi) intended for said at least one piece of equipment, the command sent (OPTi) having an identifier corresponding to the sequence (SEQi) identified among the stored sequences. Method according to one of Claims 2, 3, 5 and 6, characterized in that the comparison of the stored sequence (SEQi) with the estimated sequence (SEQest) is carried out by correlation. Method according to one of the preceding claims, characterized in that the signal generated is emitted repeatedly by a source (SSi; SS), the sequence (SEQi) being successively repeated. Method according to Claim 8, characterized in that a guard interval is provided before repeating a sequence (SEQi). Computer device comprising a processing circuit (CT) configured to implement the method according to one of the preceding claims. Device according to Claim 10, characterized in that the processing circuit (CT) is configured for the implementation of the method according to Claim 3, as a medical device. Device according to Claim 10, characterized in that the processing circuit (CT) is configured for implementing the method according to one of Claims 4 to 6, as a man/machine control interface device. Device according to one of Claims 10 to 12, characterized in that the sensory stimulation signal is a light signal flashing at a variable frequency according to the said sequence, and in that the processing circuit (CT) comprises a processor (PROC) configured to drive display of an icon on a screen (ECR) with flashing at a flashing frequency that follows said sequence. Device according to one of Claims 10 to 13, characterized in that the processing circuit (CT) comprises an input interface (IN) for signals (EEG) coming from at least one neuronal potential signal sensor (BCI ). Computer program comprising instructions for implementing the method according to one of Claims 1 to 9, when the said instructions are executed by a processor of a processing circuit 16 [Claim 16] (CT). Non-transitory recording medium readable by a computer on which is recorded a program for implementing the method according to one of Claims 1 to 9 when this program is executed by a processing circuit (CT).