Dr. Kazuyuki Samejima, Brain Science Institute, Tamagawa University
This seminar is internal, for OIST members only.
Date & Time: October 3rd, 2011(Monday) 11:00
Venue: Campus, Meeting Room (D015 -D Floor, L1 Bldg)
Speaker: Dr. Kazuyuki Samejima
Brain Science Institute, Tamagawa University.
Title: The neural activities in the rostral-striatum during the
Comparing reward values of multiple options and selecting the best one
among them is a fundamental process for decision-making. Recent
neurophysiological studies suggested that frontal cortex-basal ganglia
circuit is involved in a value-based decision-making process. However,
little is known about how and where the value comparison and action
selection processes are implemented in the neural circuits. One of the
difficulties in a traditional task paradigm is to distinguish the
decision-making process, in which the values of possible options are
compared, from the motor preparation immediately following a decision.
In this talk, we report activities of striatum neurons in macaques
performing a button press/release choice task, in which we could
temporally dissociate cognitive decision and motor decision. In the
choice task, the monkey had to choose one of two stimuli (choice-cue)
and remembered it until responding by button release when the chosen
stimulus appeared again as target stimulus. The amount of juice reward
was associated with the chosen stimulus. After the choice-cue onset, the
monkeys could evaluate offered-stimuli and compare them cognitively;
however they had difficulty selecting motor-output, i.e. whether to
release or keep the button pressed, until the first target stimulus was
To elucidate striatum contribution in the decision-making process, we
compared the neuronal activities in the choice task with those in the
instruction task as a non-choice control task in which we used an
instruction cue of a visual stimulus instead of two different choice cue
stimuli. In the cue period, we observed similar proportions of the
choice-preferred neurons (15%) and instruction-preferred neurons (13%).
In the delay period, the proportions of the choice-preferred neurons
were increased (20.6%), whereas those of the instruction-preferred
neurons were remained unchanged (10%). Mutual information analysis
revealed that the cue-related activities encode the possible options of
the cue stimuli in the cue-period, whereas the activities encode
information about the chosen stimuli during the delay-period. These
results suggest that the rostral part of the striatum is involved in not
only action selection for choosing a concrete motor-output but also the
cognitive selection for choosing an “abstract action”.
We look forward to seeing many of you there.
Neural Computation Unit, Okinawa Institute of Science and Technology
1919-1 Tancha, Onna, Okinawa 904-0412, Japan
Phone: +81-98-966-8594; Fax: +81-98-966-8613