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Yuri I Arshavsky

Publications and source records attributed to Yuri I Arshavsky.

6 recordsLinked to original sources
PubMed2006

"The seven sins" of the Hebbian synapse: can the hypothesis of synaptic plasticity explain long-term memory consolidation?

Memorizing new facts and events means that entering information produces specific physical changes within the brain. According to the commonly accepted view, traces of memory are stored through the structural modifications of synaptic connections, which result in changes of synaptic efficiency and, therefore, in formations of new patterns of neural activity (the hypothesis of synaptic plasticity). Most of the current knowledge on learning and initial stages of memory consolidation ("synaptic consolidation") is based on this hypothesis. However, the hypothesis of synaptic plasticity faces a number of conceptual and experimental difficulties when it deals with potentially permanent consolidation of declarative memory ("system consolidation"). These difficulties are rooted in the major intrinsic self-contradiction of the hypothesis: stable declarative memory is unlikely to be based on such a non-stable foundation as synaptic plasticity. Memory that can last throughout an entire lifespan should be "etched in stone." The only "stone-like" molecules within living cells are DNA molecules. Therefore, I advocate an alternative, genomic hypothesis of memory, which suggests that acquired information is persistently stored within individual neurons through modifications of DNA, and that these modifications serve as the carriers of elementary memory traces.

Animals↗
PubMed2006

"Scientific roots" of dualism in neuroscience.

Although the dualistic concept is unpopular among neuroscientists involved in experimental studies of the brain, neurophysiological literature is full of covert dualistic statements on the possibility of understanding neural mechanisms of human consciousness. Particularly, the covert dualistic attitude is exhibited in the unwillingness to discuss neural mechanisms of consciousness, leaving the problem of consciousness to psychologists and philosophers. This covert dualism seems to be rooted in the main paradigm of neuroscience that suggests that cognitive functions, such as language production and comprehension, face recognition, declarative memory, emotions, etc., are performed by neural networks consisting of simple elements. I argue that neural networks of any complexity consisting of neurons whose function is limited to the generation of electrical potentials and the transmission of signals to other neurons are hardly capable of producing human mental activity, including consciousness. Based on results obtained in physiological, morphological, clinical, and genetic studies of cognitive functions (mainly linguistic ones), I advocate the hypothesis that the performance of cognitive functions is based on complex cooperative activity of "complex" neurons that are carriers of "elementary cognition." The uniqueness of human cognitive functions, which has a genetic basis, is determined by the specificity of genes expressed by these "complex" neurons. The main goal of the review is to show that the identification of the genes implicated in cognitive functions and the understanding of a functional role of their products is a possible way to overcome covert dualism in neuroscience.

Animals↗
PubMed2005

The role of sensory network dynamics in generating a motor program.

Sensory input plays a major role in controlling motor responses during most behavioral tasks. The vestibular organs in the marine mollusk Clione, the statocysts, react to the external environment and continuously adjust the tail and wing motor neurons to keep the animal oriented vertically. However, we suggested previously that during hunting behavior, the intrinsic dynamics of the statocyst network produce a spatiotemporal pattern that may control the motor system independently of environmental cues. Once the response is triggered externally, the collective activation of the statocyst neurons produces a complex sequential signal. In the behavioral context of hunting, such network dynamics may be the main determinant of an intricate spatial behavior. Here, we show that (1) during fictive hunting, the population activity of the statocyst receptors is correlated positively with wing and tail motor output suggesting causality, (2) that fictive hunting can be evoked by electrical stimulation of the statocyst network, and (3) that removal of even a few individual statocyst receptors critically changes the fictive hunting motor pattern. These results indicate that the intrinsic dynamics of a sensory network, even without its normal cues, can organize a motor program vital for the survival of the animal.

Action Potentials↗
PubMed2003

Experience-dependent expression of terminal deoxynucleotidyl transferase in mouse brain.

Terminal deoxynucleotidyl transferase (TdT), a template-independent DNA polymerase, contributes to antigen receptor diversity in lymphocytes. Using in situ hybridization, we found that tdt is expressed within neurons of the adult mouse brain. tdt mRNA was localized within pyramidal neurons in the hippocampus, granule and polymorphic cells in the dentate gyrus, Purkinje neurons in the cerebellum, and cortical cells. Increased levels of tdt mRNA in the hippocampus, neocortex, and cerebellum were associated with rearing C57BL/6 mice, but not DBA/2 mice, in enriched environments. Unlike wild types (WT), tdt (-/-) mice did not show improvement in spatial learning and memory as a result of rearing in enriched environments. These results suggest that tdt may be involved in learning and memory saving.

Animals↗
PubMed2003

Cellular and network properties in the functioning of the nervous system: from central pattern generators to cognition.

The relation between individual neurons and neuronal networks in performing brain functions is one of the central questions in modern neuroscience. Most of the current literature suggests that the role of individual neurons is negligible and neural networks play a dominant role in the functioning of the nervous system. Individual neurons are usually viewed as network elements whose functions are limited to generating electrical signals and releasing neurotransmitters. Here I summarize experimental evidence that challenges this concept and argue that the unique, intrinsic properties of highly specialized individual neurons are as important for the functioning of the brain as the network properties. I first discuss the studies of relatively 'simple' functions of the nervous system, such as the control of rhythmic 'automatic' movements and generation of circadian rhythm, which indicate that individual neurons may continue performing their functions after being separated from corresponding networks. I then argue that the complex cognitive functions, such as declarative memory, language processing, and face recognition, are likely to be underlain by the properties of groups of highly specialized neurons. These neurons appear to be genetically predisposed to perform cognitive functions and their dysfunctions cannot be compensated by other elements of the nervous system. Under this concept, the electrical signals circulating within and between neural networks are considered to be a means of forming coordinated dynamic ensembles of neurons involved in performing specific functions. While still speculative, this hypothesis may provoke new approaches to studies of neural mechanisms underpinning cognitive functions of the brain.

Animals↗