Speaker/Affiliation: Okihide Hikosaka M.D. Ph.D.
Senior Researcher Chief Section of Neuronal Networks Laboratory of Sen

sorimotor Research National Eye Institute NIH

When/Location: 10/6/

2008 12:00 PM SEA 4.244

Host: Mary Hayhoe

Title of Talk: ''

Basal ganglia mechanisms of reward-based and instruction-based decision-mak

ing''

Reception with Refreshments at 11:30 AM

Abstract: The b

asal ganglia contain parallel neural circuits: direct indirect and hyperd

irect pathways. A popular hypothesis is that these pathways work in a coord

inated manner to select a desired action while suppressing undesired action

s. However critical evidence to support this hypothesis had been lacking u

ntil recently. Based on our recent experiments using trained monkeys we pr

opose that the direct and indirect pathways select actions based on motivat

ional demands whereas the hyperdirect pathway selects actions based on cog

nitive demands. The direct pathway which consists of two serial inhibitory
connections serves to acquire actions that lead to rewarding outcomes. Th

e indirect pathway which consists of three inhibitory connections serves

to discourage actions that lead to punishing or non-rewarding outcomes. Dop

aminergic inputs to the STR are crucial in implementing motivational values
in the signals transmitted in these pathways. In contrast the hyperdirect
pathway which is mediated by the direct cortical connection to the subtha

lamic nucleus serves to select one action that is in conflict with others
especially for switching from an automatic action to a controlled action.

Inputs from outside the basal ganglia especially those from the lateral ha

benula and the dorsal raphe (including serotonin neurons) fine-tune or mod

ify the operation of the basal ganglia circuits.