Возможные механизмы взаимозависимого участия базальных ганглиев и мозжечка в функционировании двигательных и сенсорных систем

Abstract

The article describes a mechanism of functioning of the neural network that includes the neocortex, basal ganglia, cerebellum, and thalamus. This mechanism explains the role of the cerebellum in the performance of tasks previously associated with the basal ganglia and neocortex. Rules for long-term modifications of the efficacy of synaptic inputs to cerebellar neurons and spiny cells of the striatum, an input nucleus of the basal ganglia, have been formulated. These rules differ from those generally accepted. It follows from the proposed modulation rules that the activation of D1 receptors promotes the induction of LTP in synapses formed by mossy fibers carrying sensory information to cerebellar granule cells as well as neurons of the deep cerebellar nuclei (providing that they are inhibited by Purkinje cells). This results in the enhanced disynaptic (through the thalamic nuclei) excitation of the cerebellum target cells in the neocortex, striatum and dopaminergic structures. An increase in thalamo-striatal excitation, as well as the activation of D1 receptors on striatonigral cells and D2 receptors on striatopallidal cells, promotes the induction of LTP and LTD of the efficacy of cortical inputs to these neurons, respectively. As a consequence, synergistic disinhibition via the direct and indirect pathways through the basal ganglia is facilitated for those thalamic cells and associated neocortical neurons that were initially strongly activated by sensory stimuli. Simultaneously, the inhibition of the activity of remaining thalamic and neocortical neurons by the basal ganglia must be increased. The mechanism of functioning is similar for diverse the neuronal networks, each of which includes topographically connected areas of the neocortex, thalamus and basal ganglia. Since cerebellar granule cells as well as dopaminergic neurons respond to a conditioned sensory signal and reinforcing stimulus, it follows from the proposed mechanism that the cerebellum, together with the basal ganglia, may form the patterns of neuronal activity in neocortical areas determining sensory perception and choice of action.