Affiliation:
1. Department of Neurophysiology, Kyoto University, Aichi, Japan.
Abstract
1. Using iontophoretic techniques, we investigated the effects of dopamine (DA) and noradrenaline (NA) on neuronal activity related to a delayed response (DR) task in the prefrontal cortex (PFC) of the Japanese macaque monkeys. The DR task was initiated by rotation of a handle to a central zone and consisted of seven distinct time periods: an initial waiting period of 0.3 s, a precue period of 1 s (a central green lamp), a cue period of 1 s (left or right lamp), a delay period of 4 s, a go period of 1 s (red lamp in the center; rotation of the handle to either the left or right zone), a hold period (holding of the handle in either the left or right zone for 0.3 s), and a final reward period. 2. A total of 116 neurons were DR task related. They showed increases in activity during the precue period (Precue-types, n = 19), during both the cue and go periods (Cue/GO-types, n = 17), the go period (GO-types, n = 16), and during the delay period (Delay-types, n = 64). The Delay-type neurons were further divided into differential neurons (n = 33), for which the magnitude of the delay-related activity differed significantly between left- and right-cue trials, and nondifferential neurons (n = 31). Some of the Delay-type neurons also showed increases in activity during the cue (n = 26), go (n = 27), or both the cue and go periods (n = 11). 3. DA or NA, applied iontophoretically with a current of 50 nA, induced increased or decreased responses in most of the DR task-related neurons. DA increased activity of most of the Cue/GO-(16/17), GO-(13/16), and Delay-type neurons (49/64), and NA decreased activity of most of the Precue- (13/19) and non-differential Delay-type neurons (25/31). Thus different types of DR task-related neurons showed different responses to DA and NA. 4. In Cue/GO-, GO-, and/or Delay-type neurons, DA increased the activity related to the cue, go, and delay periods more strongly than it increased background activity. As a result, the ratio [i.e., signal-to-noise (S/N) ratio] of activity related to the cue, go, and delay periods to background activity was increased. 5. In Precue-type or nondifferential Delay-type neurons, NA decreased background activity more strongly than it decreased activity during the precue or delay period.(ABSTRACT TRUNCATED AT 400 WORDS)
Publisher
American Physiological Society
Subject
Physiology,General Neuroscience
Cited by
151 articles.
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