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Reward and Decision Making

開催日 2014/9/12
時間 14:00 - 15:00
会場 Poster / Exhibition(Event Hall B)

Systemic stimulation of α2 adrenergic receptors with clonidine affects oscillatory activity in the rat hippocampus during a spatial decision-making task

  • P2-228
  • 雨宮 誠一朗 / Seiichiro Amemiya:1 Redish A. David / A. David Redish:1 
  • 1:ミネソタ大学 / Dept Neurosci, Univ of Minnesota, Minneapolis, USA 

Hippocampus (HC) oscillatory activity is thought to reflect dynamic cognitive processes in decision making. Noradrenaline (NA) manipulations affect HC oscillations in vitro, and in anesthetized and freely-moving animals. However, few studies have examined NA involvement in HC oscillations during decision making. We recorded local field potentials (LFP) from the CA1, CA3, and fissure regions of HC from rats running a decision-making task, and examined the influence of the α2 adrenergic autoreceptor agonist clonidine. Rats ran a modified Hebb-Williams maze, consisting of a changeable central path, a final decision point, and rewarded return rails leading back to the start. Three reward-contingencies were used: turn left, turn right, or alternate for reward. During the analyzed probe trials, the rewarded rule changed approximately halfway through the session. On this task, particularly after the switch in contingency, rats sometimes pause and orient back and forth at the choice points, a process termed "vicarious trial-and-error" (VTE). To manipulate NA transmission, clonidine (30μg/kg, i.p.) or vehicle was delivered 30 min before behavior. Oscillations in the theta (4-12Hz), beta (14-29Hz), slow gamma (30-55Hz), mid gamma (60-90Hz), and fast gamma (90-140Hz) ranges were examined. Theta asymmetry has been hypothesized to reflect changes in the phase modulation of oscillations. To measure the asymmetry of each theta wave, we calculated the ratio of the ascending (trough to peak) and descending (peak to trough) parts. Consistent with previous studies, clonidine suppressed the occurrence of VTE-like events. Neurophysiologically, clonidine decreased power in all frequency bands. At the final decision point, control sessions showed a decrease of power in beta and slow gamma oscillations and an increase of power in mid gamma oscillations in VTE laps compared to non-VTE laps. These changes were suppressed by clonidine. Theta waves were more symmetric on VTE laps than on non-VTE laps around the choice point, and this difference was decreased by clonidine. Our findings suggest that NA modulates HC processing during decision making.

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