Search for a Hidden Platform in the Morris Water Mazeon the Dopamine Gradient on the Place Cells
A simple model of a search for a hidden platform in the Morris water maze based on past experience is proposed. 1) During the preliminary survey of the basin, a “cognitive map” is formed – the cells of neighboring places exciting with overlap in time are linked together on the basis of dopamine-modulated STDP plasticity. 2) When the rat first finds the platform, a “safety signal” of an opioid nature is generated with SPW-Rs complexes in CA3. Under the influence of opioid inhibition of inhibitory interneurons in the CA3 field, excitation from the safety place cells extends as a damped wave along functionally effective cognitive map connections. 3) Opioid suppression of the inhibitory inputs to the dopamine neurons of the midbrain creates conditions for enhancing excitatory links from place cells to dopamine neurons in inverse relationship to the distance to the platform. 4) Upon repeated entry into the pool in the next trial, the animals select a route according to the dopamine gradient on the place cells: the excitation of dopamine neurons increases the motor activity of the animal towards the hidden platform.