Faust, Thomas W.. Influence of the neostriatal patch system on the prediction-based coding of midbrain dopaminergic neurons. Retrieved from https://doi.org/doi:10.7282/T3N019KQ
DescriptionDopaminergic neurons of the ventral midbrain signal deviations from expected values, and have profound effects on motivated behavior. It has been hypothesized that these neurons produce these signals by integrating prediction and outcome information from distinct afferent structures, and update representations of prediction by dopamine-dependent synaptic plasticity. I therefore attempted to characterize the coding properties of one of their primary source of synaptic inhibition, the patches of the dorsal striatum, in an attempt to determine whether it could serve to provide prediction information to the dopaminergic neurons. The coding differences between the patch and matrix subpopulations of the dorsal striatum have thus far remained unknown, but due to the recent availability of new transgenic mouse lines targeting these neuronal populations, they can now be investigated. Based on their unique monosynaptic innervation of dopaminergic neurons of the substantia nigra, receipt of dopaminergic innervation from the substantia nigra, and dopamine-dependent synaptic plasticity, I therefore hypothesized that the neurons of the dorsal striatal patches provide the prediction signal by which dopaminergic neurons report deviations in expected value. I used in vitro whole cell recording and optogenetics to determine the synaptic physiology of projections from the patches to dopaminergic neurons, and used in vivo multielectrode recording and optogenetics to characterize the coding properties of striatal patch and matrix neurons. The patches of the dorsal striatum were observed to provide biophysically distinct fast and slow inhibition to the dopaminergic neurons of the substantia nigra, and dorsal striatal patch neurons were observed to encode signals which conform to the notion of a prediction signal. Therefore these results support the hypothesis that dopaminergic neurons encode deviations from predicted outcomes, and that the dorsal striatal patches provide a prediction signal necessary for this type of coding.