2004 Fiscal Year Final Research Report Summary
The research on mechanisms of the impulsive behavior
| Project/Area Number |
14510114
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
実験系心理学
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| Research Institution | Tokyo Metropolitan Institute for Neuroscience |
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Principal Investigator |
HIKOSAKA Kazuo Tokyo Metropolitan Institute for Neuroscience, Psychology, Researcher, 東京都神経科学総合研究所, 研究員 (60129004)
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| Project Period (FY) |
2002 – 2004
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| Keywords | Orbitofrontal cortex / Reward expectancy / Primate / Neuronal activity |
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| Research Abstract |
The impulsive behavior is one of severe impairments in goal-directed behavior. To understand the mechanism underlying the impulsive behavior, it is important to investigate differences in reward expectancy or behavior between "getting a preferred reward" and "getting a non-preferred reward". Therefore, I examined pre-instruction, baseline activities of neurons in orbitofrontal cortex (OFC) in relation to reward expectancy during the delayed reaction time task. In this task, an instruction cue indicated whether reward would be present or absent in the trial. Each set of four consecutive trials constituted one block within which three different kinds of rewards and one trial with no reward were given in a fixed order that differed from the monkey's reward preference. I identified two types of OFC neurons with reward expectancy-related pre-instruction activities : Step-type neurons showed stepwise changes (increase or decrease) in pre-instruction activity toward the trial with a particular outcome, which usually was the most or least attractive within a block ; Pref-type neurons showed pre-instruction activity changes according to the monkey's preference for each trial's outcome. I propose that Step- and Pref-type neurons are related to long- and short-range reward expectancies of a particular outcome, respectively. The OFC is considered to play important roles in goal-directed behavior by adjusting the motivational level toward a certain (current or future) outcome of a particular motivational significance based on the two kinds of reward expectancy processes. Impairments in goal-directed behavior, including impulsive behavior, by OFC patients may be caused by a lack of long-range expectancy or by a deficit in compromising between short- and long-range expectancies.
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