Asahi, T., Uwano,
T., Eifuku, S., Tamura, R., Endo, S., Ono, T.,
Nishijo, H. Neuronal responses to a delayed-response
delayed-reward go/nogo task in the monkey posterior
insular cortex. Neuroscience 143: 627-639, 2006. [査読有]
Anatomical connections of the
insular cortex suggest its involvement in cognition, emotion, memory, and
behavioral manifestation. However, there have been few neurophysiological
studies on the insular cortex in primates, in relation to such higher cognitive
functions. In the present study, neural activity was recorded from the monkey
insular cortex during performance of a delayed-response delayed-reward go/nogo task. In this task, visual stimuli indicating go or nogo responses associated with reward (reward trials) and
with no reward (no-reward trials) were presented after eye fixation. In the
reward trials, the monkey was required to release a button during presentation
of the 2nd visual stimuli after a delay period (delay 1). Then, a juice reward
was delivered after another delay (delay 2). The results indicated that the
neurons responding in each epoch of the task were topographically localized
within the insular cortex, consistent with the previous anatomical studies
indicating topographical distributions of afferent inputs from other
subcortical and cortical sensory areas. Furthermore, some insular neurons 1)
nonspecifically responded to the visual cues and during fixation; 2) responded
to the visual cues predicting reward and during the delay period before reward
delivery; 3) responded differentially in go/nogo
trials during the delay 2; and 4) responded around button manipulation. The
observed patterns of insular-neuron responses and the correspondence of their
topographical localization to those in previous anatomical studies suggest that
the insular cortex is involved in attention- and reward-related functions and
might monitor and integrate activities of other brain regions during cognition
and behavioral manifestation.