Figure 4.

A schematic illustration of the proposed convergence of short-latency phasic inputs to the striatum elicited by an unpredicted visual event. Direct retinal input to the superior colliculus could be re-directed, via branched projections to the intralaminar thalamic nuclei and to the substantia nigra pars compacta. At present, the identities of the neurotransmitters used in branched connections from the superior colliclus are unknown. Consequent, potentially converging phasic inputs to the striatum from intralaminar nuclei (GLU, glutamate) and substantia nigra (DA, dopamine) are likely to play a critical role in reinforcement learning.