Laboratory of Psychophysiology MSU: EEG as a tool reverse engineering the brain and brain-computer interface

(Katya connect to the matrix 32 EEG channels with active electrodes) i>

As "Pacman guzzle nonexistent square" which part of the brain generates the illusion of color figures as psychophysiologists handle multidimensional signals and whether it can lead to reverse-engineer the brain.

Under the cut surface description of the device, a little bit about signal processing and research about those who spend a psycho young scientists, neuroscientists, and what challenges there are for programmers who want to study the brain and / or work in a project to study the brain.



Conveniently located in a chair, sit back and take a deep breath



EEG helmet with a system of ActiChamp Brainproducts ™ is equipped with active biosensors (up to 128 channels) that capture the smallest changes in the electrical signals from the brain of a person with extremely high sampling rate - up to 100 kHz!

256 channels



256 channels



Active, as opposed to passive electrodes are equipped with the built-in microchips - preamps, which digitizes the analog signal and transmits it with the least distortion.

The electrodes are mounted above all important for the analysis of brain regions and synchronously transmit a signal to the amplifier unit or by using the loop or on wi-fi - 32 in the flow channel with a bandwidth of 1000 Hz band and a sampling frequency of 5000 Hz up to 500 Hz, in contrast to some of the medical EEG, not to mention neyrogarniturah).


Wi-fi module



Once signals are sent to amplifier units (noise level ≤ 2 μVpp), their path is not terminated. Then they are transferred to a double fiber optic cable to the USB-adapter, which also receives and external signals (triggers) to synchronize with external devices, such as EyeTracker'om (it was in the trail. Time). USB-adapter serves as a connector to the PC.



The main objective of all elements of intermediaries to minimize distortion and delay in the signal, whose power is measured only tens of microvolts





Additional blocks for the registration of so-called peripheral indicators that reflect autonomic processes, such as heart rate, vascular tone, respiration, temperature, movement, muscle activity, etc., up to 128 additional channels.

Sensors


Skin resistance, temperature sensor, an accelerometer, a heart rate monitor optical



Here on whom measurements were made when no students

Software and Signal Processing h4> Software for processing and analysis of the EEG has broad functionality with the ability to integrate data MRI for localization of electrical signals given individual constitution of the brain of the individual. Actually the system itself has a module called "low-resolution tomography» (LORETA) (* this is not about the technical realization - magnetic or positron emission, and the principle of visualization and mapping of the brain).

One of the main problems for accuracy - are artifacts. This term refers to distortion by external or internal factors, whether eye movements or aiming at 100 Hz from the fluorescent lamp.

Despite the seeming perfection of EEG technology, shortcomings are still present. Perhaps foremost among them - the necessity of using an electrically conductive paste or gel to reduce the resistance between the electrodes and the scalp. Technology in general is not a self-sufficient, and recent trend converges to a combination of different methods. Already using electrodes that operate in a magnetic field tomography (about 10 Tesla).



Dotted line - it is an external stimulus. Fagment EEG signal (left) attempts to locate a source of three-dimensional space (in the middle) and in the projection onto the scalp (right)



A fragment of the recorded EEG



That's such krivulkami our brain sees the world. But seriously, this is the MSS (potentials related to events), which reflect the net (specially recorded and filtered) groups of neurons response to a particular stimulus. Here they are all together on all leads. Potential and so far (if at all) unsolvable problem is the opposite: to restore what is seen / heard / was / touch people at this moment?



Bottom - MSS, but not all together, and the way they were recorded in different leads.



Map subelectrode localization activity per second - Image to Image



3d-view



The Fourier transform of the signal recorded at different electrodes.



Continuous wavelet transform EEG. (The first rule psychophysiologists - not to tell anyone about the wavelet. Joke.) Wavelet we need to look at the frequency component of the EEG (different rhythms consist of different frequencies and reflect different states of persons) and consider it all in time on th term.

People h4>

Warning h5> Vyacheslav Lebedev , employee and graduate student psychophysiology MSU. MV University, co-founder of NeuroFuture , physiologist:
"The essence of my scientific work - study of the role of attention in the process of cross-modal integration.
Explanation: The information coming from the external environment, usually consists of signals of different modalities (auditory, visual, etc.). Processing of multisensory information requires synchronous collaboration brain structures involved in obrabtke signals a certain modality. Modern studies on the level of individual neurons indicate the existence of neurons in different areas and levels of the brain whose function is to treat it multisensor information. But the question remains open system combining these multi-level structures in the process stream processing multisensory information as well as the role of an arbitrary (initiated by the man himself) and involuntary (caused by external events) attention in the process. EEG - one of the most informative methods for studying the dynamics of this process. »



(Find a dog) i>

Illusion h5> Ilya Zakharov , graduate student psychophysiology MSU. MV University, co-founder of NeuroFuture , physiologist:
"Psychophysiology trying to tie the perfect (psychology and" soul "if there is one) and material (that you can explore the natural-scientific methods). Obtained with varying degrees of success, but it is interesting



There are such things - an illusion. What happens in the brain when we see them? Is there a universal pattern of brain activity, the same for all people, which is characteristic only for those moments when we see the visual illusion? And what if we look at a loved one, and we suddenly appears this pattern?



By recording the different EEG patterns can be related objectively to register in person perception for a new type of illusion (for example, a new version of the illusion of subjective contour). To do this, use the method of event-related potentials: the allocation of the total EEG signal of the component that appears on presentation of illusions.



Black schedule - just an incentive, red - an illusion, dashed - the moment of stimulus presentation
Right - the brain's response to the presentation of classical type illusions compared to the stimulus when the brain does not need to finish building
Left - response to the presentation of a new type, again, in comparison with when it is not necessary to finish building i>

We see that in the same place (component N170) amplitude of the signal in response to the illusion of more. This response - an objective measure of our perception of the illusion. If we see straight, wavy and illusory contours at the same psychophysiological level, probably in both cases we use the same mechanisms of formation of the image. »

Programming and multidimensional signal processing h5> Kostya Slavnov , programmer
- What is the inner motive spodvig mathematics to work on a project-neyrosayns? I>
- Interest. I was always curious to know how the human brain works. By that time I already knew a lot about the possibilities of the method of data analysis in relation to the brain. All of them are based on multidimensional signal processing. And I had just such a theme of the course work.
As always played a major role accident. I read article about Ilya and decided to write it myself, that I - a mathematician-programmer interested in this topic. And the guys just did not have a man with my skills. And I quickly joined in the work.

Synesthesia h5> Maria Stepanenko , a student at the Department of Psychophysiology MSU. MV University, physiologist, researcher of synesthesia

"Synesthesia - is, roughly speaking, the relationship of different modalities. It is manifested in the form of experience sensations in one modality when offering incentives to another.



Can you quickly find the "color" triangle? I>

Generally, synesthesia - very interesting, but also very scantily phenomenon. There is an incredible variety of different types of it: some synesthetes "see" the color of certain letters / days of the week / month, some of them "feel" smells in pronouncing certain words, someone "feels" the voice texture / smell, "feels" taste names "hears" motion and so on. Moreover, the majority of communication is not shown synesthetes two but a plurality of modalities, and thus exhibit various types sinestezii.

There are many hypotheses about the way in which there are synesthetic experience. In my study of the question of the level at which this process occurs: Is it only perceptual sensations, the processing of which takes place at the lower levels, or a high-level, cognitive process.
Emphasis on audiovisual synaesthesia - namely in touch tones and timbres with different colors. As the subjects act as synesthetes, and people who do not have synesthetic perceptions. In the course of the experiment (- namely, at the time of presentation of the sound stimuli) is recorded EEG, and later - the analysis of the data by comparing the CAP, registered in synesthetes and nesinestetov.

Speaking of the test: if you are interested in this topic, or suddenly you have friends synesthetes, or suddenly, you do find yourself in the presence of suitable species for this study audiovisual synesthesia - feel free to contact me, I'll be glad to see you among our subjects! »

Speech at TED neuroscientists




Test synesthesia "color numbers" (left - how an ordinary person sees the picture on the right - the vision of synesthetes: a triangle of deuces immediately highlighted in a different color, so that synesthetes easily and quickly can point at any deuces in the picture) i>

Processing h5> Andrew Uchaev , student of the Moscow State University of Psychophysiology. MV Lomonosov, psychophysiology:
"My position is to obtain experimental data was well reflected in the words of one of the hero of the game:" ... we just throw science into the wall and see what sticks .. "This suggests that the study I try to get the most out of data that can be squeezed at all of electrophysiological signal.



Now I'm fixated more on the following: on the development of various methods of signal processing, regardless of the task. Help programmers here is enormous. There are various problems: the case that not all methods of treatment are presented in one program, or do not have access to all functionality - you have to dodge, and is not always possible.



And there is another important issue - saving time. Quite often it is necessary to process the data of ten people, using 10-15 different transformations. There would not stop writing scripts that will automate the task. He pressed the button and went home - and in the morning everything is processed. »

Conclusion h4> «neuroscience need programmers." So speak and Russian counterparts, and foreign neuroscientists even turning to the hacker. Because very soon we, God forbid, may be required not only privacy tool message i> from the technical interception, but thought i>.


Asimov wrote that "humanity is left with two puzzles - the depths of space and the mystery of the brain," pleased that the Habr very much welcomes the space program, I hope that the same thing will happen with the study of the brain.

Source: habrahabr.ru/company/neuronspace/blog/235399/