[The mechanisms of interdependent influence of prefrontal cortex, hippocampus and amygdala on the basal ganglia functioning and selection of behaviour].

The hypothetical mechanism of functioning of neural networks that include limbic structures, neocortex and basal ganglia is proposed. A hypothesis is based on known data that the hippocampus, amygdala and prefrontal cortex interreact with each other, that their efferents converge on spiny cells of nucleus accumbens, that these inputs are topically organised and could be modified. Since GABAergic spiny cells of nucleus accumbens innervate neurons in the output basal ganglia nuclei which inhibit excitatory transmission through the thalamic nuclei into limbic structures and neocortex, the degree of activation of neurones in mentioned structures and, hence, a behaviour selection essentially depends on the character of responses of spiny cells.

[Investigation of features of EEG changes at psychomotor disturbanses associated with microsleep].

We tested our earlier suggested hypothesis that one of mechanisms for failures of performance of behavioural tasks during microsleep is a spontaneous generation of ponto-geniculo-occipital (PGO) waves that suppress transmission of visual information from the retina via lateral geniculate nucleus to primary visual cortical areas and the striatum, and therefore significantly impair visual perception and attention. Experiments were done during the nighttime. Monotonic testing during performance of the two-alternative psychomotor test invoked participants into a state defined as a microsleep with open eyes.

[Possible mechanisms of learning, memory and attention impairment in consequence of sleep deprivation].

We proposed that impairment of learning, memory, and attention evoked by sleep deprivation could be a consequence of following changes in neuromodulator concentrations and intracellular processes that influence synaptic plasticity and functioning of the hippocampal formation and cortico--basal ganglia--thalamocortical loops. Firstly, a decrease in Ca2+ concentration and NMDA-receptor expression prevents induction of LTP of efficacy of synaptic transmissions in the neocortex and hippocampus. Secondly, a decrease in orexin concentration also worsens conditions for LTP induction and suppresses transmission of excitation in trisynaptic pathway through the hippocampus, thus worsening a creation of neural representations of "object-place" associations.

[Possible mechanisms for orexin effects on the functioning of the hippocampus and spatial learning (analytical review)].

We analyzed possible mechanisms for the influence of the "wakening hormone" orexin on spatial learning acting via changes in the functioning of the hippocampus and connected structures. The literature data point out that, firstly, orexin can directly potentiate excitation of neurons in different hippocampal areas by acting on Gq/11-protein-coupled postsynaptic OX1 and OX2 receptors. Due to facilitation of induction of the long-term potentiation of excitatory transmission at each stage of trisynaptic pathway through the hippocampus, orexin can promote transduction of information through this structure and formation of neural representations of object-place associations.

[Generation of Ponto-Geniculo-Occipital (PGO) waves as a possible reason of disturbances in visual perception in microsleep].

A hypothesis is put forward that one of the reasons for disturbances in visual perception during microsleep could be a spontaneous generation of Ponto-Geniculo-Occipital (PGO) waves. If the PGO waves are generated in microsleep, they could propagate into different thalamic nuclei conveying visual infomation. Consequently, a propagation of visual infonnation from the retina (if the eyes are opened) to visual neocortical areas and to input basal ganglia nucleus, striatum could be impaired.