Contribution of oxytocin and dopamine to the formation of neural clusters in the neocortex representing multimodal sensory stimuli

Abstract

We have previously proposed a unified mechanism for the formation of contrasted representations of multimodal sensory stimuli in the activity of neocortical neurons. Contrasting is based on the opposite sign of modification of the efficacy of strong and weak excitatory inputs to the spiny cells of the striatum (the input structure of the basal ganglia) and the subsequent dopamine-dependent activity reorganizations in parallel cortico – basal ganglia – thalamocortical loops. Oxytocin and dopamine (through D1 receptors) can improve the contrast of these representations, contributing to the induction of LTP of the efficacy of excitation of cortical, thalamic, and hippocampal neurons innervating spiny cells. In addition, oxytocin and dopamine can improve contrasting enhancement by increasing the signal-to-noise ratio in the neocortex, hippocampus, and striatum. A proposed mechanism for increasing the signal-to-noise ratio is based on the opposite sign of a long-term modification of the efficacy of monosynaptic excitatory and disynaptic inhibitory inputs, simultaneously affecting the postsynaptic neuron. The proposed mechanisms may underlie the contribution of oxytocin and dopamine to improving the formation and long-term maintenance of activity in neuronal groups with similar receptive fields that form columns in the primary visual cortex, a tonotopic map in the primary auditory cortex, a somatotopic map in the sensorimotor cortex, and distributed clusters in the olfactory piriform cortex. These mechanisms differ from the commonly accepted mechanisms of the formation of neuronal clusters in the neocortex with similar RPs, that are based on afferent and lateral excitation and inhibition, which does not allow providing the specificity and duration of effects. Understanding the mechanisms of involvement of oxytocin and dopamine in the processing of multimodal sensory information may be useful for developing treatments for some disorders of social behavior.