Laboratory of Neurophysiology of Cognitive Processes Main research areas
Institute of Developmental Physiology (RAE)

Main research areas

   Brain functional maturation in human ontogenesis

    EEG signals carry a valuable information about the dynamics of electrical activity in neural networks. EEG depends on the connectivity between neurons and therefore reflects morpho-functional organization of the brain. The morpho-functional organization of the brain changes significantly through lifespan and so does EEG.

 

 
 
 
 
  

For example, it is well known that maturation of the cortex is accompanied by detectable changes in parameters of the most salient EEG oscillatory activity known as alpha-rhythm: During developmental course a dominant frequency of the background alpha-rhythm increases, its waveform becomes more regular, and a topographical distribution of its magnitude alters. However much less is known about what kind of information about maturity of deep subcortical structures can be extracted from EEG.

    In a majority of works that have been done so far in order to assay the brain maturating process, EEG is described in spectral domain. However an electrical activity related to subcortical structures isn't a stationary process. An EEG pattern related to deep brain structures usually takes a form of a lonely wave or a combination of such waves. Those waves may take various shapes and are localized in time, the latter means they surface on EEG trace only for a brief period of time. Because of the brevity of depth-related EEG patterns and their specific shapes it makes more sense to describe them in temporal rather than spectral domain.

 

 

 

 

   One of the reasonable ways (and really not the worst one!) to assess specifics of such localized EEG patterns and degree of their synchronicity among multiple channels is to use a human expert-based visual analysis of EEG traces. In collaboration with our colleagues from Institute of problems of information transmission and from Institute of corrective pedagogics we developed a scheme for the expert-based visual analysis of EEG aimed at qualitative assessment of the functional state of the brain. This assessment scheme is based not on some formal description of EEG (e.g. a list of frequencies and amplitudes of selected rhythms) but rather on an attempt to make a whole description to be a set of meaningful units or block. These blocks relate observed EEG patterns to the state of the cortex as a whole, separate cortical areas, or deep regulatory structures. While developing this analysis scheme we attributed each specific EEG pattern to a particular block based on judgments of human experts as well as the knowledge available from literature. Such a structured description provides sufficiently detailed information about the state of different brain structures therefore making it easer to compare that description against the data obtained from some other source, e.g. neurological or neuropsychological assessment.

 

    The EEG description scheme has been applied for analyzing EEG data records from children of different ages ranged from 5 to 14 years old. By combining EEG descriptions with scores of academic success and neuropsychological assessment in the same children in a joint analysis we worked out several EEG-based criteria of functional maturity of cortex and deep regulatory structures of developing brain.

  • - Not typical for a given age
  • + - Typical for a given age
  • Im - sign of immaturity

 

 

    In our lab the description scheme along with the criteria of functional maturity of the brain are routinely used in practice (as a part of assessment of an overall development level of a child) and in a research work (in order to study neurophysiological mechanisms underlying learning difficulties and deviant behavior in school children).

 

 

 Development of system brain organization of cognitive processes (perception, attention, visuo-spatial and verbal functions) in human ontogenesis

   We study neurophysiological mechanisms underlying cognitive processes in children aged from 3 to 16 years old. We record multichannel EEG from different cortical areas and analyze event-related potentials and rhythmic activity.

   From many studies that have been done in our lab it follows what seems to be a general tendency in the development of the system organization of cognitive functions. Take visual perception as an example. Early in the development of a child, the cortical contribution to visual perception, for the most part, is limited to the visual cortex. Later in the development, the visual perception is characterized by the involvement of multiple cortical areas including associative ones. The distinctive feature of this stage is a lack of apparent specificity of the functional contribution of different cortical areas, thus making the cooperation among cortices "diffusive". In maturity, what underlies visual perception is a functional system of many interacting cortical structures, each making its unique and specific contribution to the functioning of the whole.

In course of development, a similar transition from the nonspecific cooperation of cortical structures to specialized participation of selected cortical areas in the whole functional system is also found when studying the attentional, visuo-spatial and verbal functions.

The series of studies that have been done in our lab make it possible not merely to state that heterochronous maturation of the brain structures affects the functional organization of cognitive processes but emphasize the role of following major factors of such influence: (1) the development of local neuronal connectivity (especially in higher associative cortices), (2) the development of inter-area connectivity, and (3) and the morpho-functional maturation of regulatory brain structures. The leading role in developing of the system brain organization of cognitive functions belongs to the prefrontal cortex and the top-down influence it exerts on the other brain structures.

At present, the major focus of the research work within the lab is on the study of the brain organization of the following of cognitive processes: visual perception, working memory, attention, and cognitive aspects of motor control. The approach we undertake combines the assessment of the cortex maturity based on qualitative analysis of EEG patterns with the quantitative electrophysiological analysis of the brain organization underlying cognitive activities. There is a hope that combining these two kinds of analyses, along with the data of neuropsychological assessment, would be promising for studying how the individual degree of the regulatory systems maturity affects the brain organization underlying cognitive processes in children.

 


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