title: Competitor suppresses neuronal representation of food reward in the nucleus accumbens/medial striatum of domestic chicks.
abstract: To investigate the role of social contexts in controlling the neuronal representation of food reward, we recorded single neuron activity in the medial striatum/nucleus accumbens of domestic chicks and examined whether activities differed between two blocks with different contexts. Chicks were trained in an operant task to associate light-emitting diode color cues with three trial types that differed in the type of food reward: no reward (S-), a small reward/short-delay option (SS), and a large reward/long-delay alternative (LL). Amount and duration of reward were set such that both of SS and LL were chosen roughly equally. Neurons showing distinct cue-period activity in rewarding trials (SS and LL) were identified during an isolation block, and activity patterns were compared with those recorded from the same neuron during a subsequent pseudo-competition block in which another chick was allowed to forage in the same area, but was separated by a transparent window. In some neurons, cue-period activity was lower in the pseudo-competition block, and the difference was not ascribed to the number of repeated trials. Comparison at neuronal population level revealed statistically significant suppression in the pseudo-competition block in both SS and LL trials, suggesting that perceived competition generally suppressed the representation of cue-associated food reward. The delay- and reward-period activities, however, did not significantly different between blocks. These results demonstrate that visual perception of a competitive forager per se weakens the neuronal representation of predicted food reward. Possible functional links to impulse control are discussed.
authors.affiliation: Graduate School of Life Science, Hokkaido University, N10-W8, Kita-ku, Sapporo 060-0810, Japan; JSPS Fellow (Japan Society for Promotion of Sciences), Ichiban-cho 8, Chiyoda-ku, Tokyo 102-8471, Japan. Electronic address: amita.hidetoshi@gmail.com.
authors.forename: Hidetoshi
authors.initials: H
authors.lastname: Amita
authors.affiliation: Department of Biology, Faculty of Science, Hokkaido University, N10-W8, Kita-ku, Sapporo 060-0810, Japan. Electronic address: matusima@sci.hokudai.ac.jp.
authors.forename: Toshiya
authors.initials: T
authors.lastname: Matsushima
mesh_terms: D000200:Action Potentials; D000818:Animals; D001070:Appetitive Behavior / Q000502:physiology*; D002645:Chickens / Q000502:physiology*; D002755:Choice Behavior / Q000502:physiology; D003163:Competitive Behavior / Q000502:physiology*; D003216:Conditioning, Operant / Q000502:physiology; D003342:Corpus Striatum / Q000502:physiology*; D003463:Cues; D004567:Electrodes, Implanted; D005247:Feeding Behavior / Q000502:physiology; D005502:Food; D007175:Impulsive Behavior / Q000502:physiology; D009474:Neurons / Q000502:physiology; D009714:Nucleus Accumbens / Q000502:physiology*; D012201:Reward; D013647:Task Performance and Analysis; D013997:Time Factors; D014796:Visual Perception / Q000502:physiology
keywords: Choice; Impulsiveness; Operant latency; Pseudo-competition; Social foraging