Aspects of “ImPulsivity” （“衝動性”の諸相）

　ICP2016のために来日するJose E. Burgos 教授（University of Guadalajara） 及びGregory J. Madden 教授 (Utah State University) をお招きして、本研究室准訪問研究員の八賀を加えて、公開シンポジウムを開催します。ご興味のある方々のご参加をお待ちしております（予約不要・無料）。（シンポジウム終了後、海外からのお二人を囲んでささやかな懇親の場を設けたいと考えております。参加希望の方は人数見積もりの関係上、事前にご連絡をいただければ幸甚です）

記

• 日時：2016年7月23日（土曜日）14時30分〜17時00分
  
  
• 慶應義塾大学三田キャンパス　研究室棟１F A・B会議室
  
  
• 司会：山口 哲生（東邦大学）
• 演者・演題・摘要
  • 八賀 洋介（慶應義塾大学）"Preference Pulses and an Induction Account"

    Preference pulse is a phenomenon that, in choice situation, preference to the just-reinforced alternative is elevated for a brief period of time and the preference diminishes as a function of time since reinforcement. Rats were exposed to concurrent Variable-Ratio (VR) 20 Extinction (EXT) schedules, under which assignment of VR reinforcement to left or right lever location randomly changed after each reinforcer delivery. It resulted to emerge the preference pulses to the EXT lever and has proposed an account where reinforcement briefly induces responses to the just-reinforced lever (Hachiga, Sakagami, and Silberberg, 2014). In a next experiment, two groups of rats responded to the same schedule but the ratio sizes was manipulated either increasingly as 8, 16, and 48 or decreasingly as 32, 16, and 4, respectively. Here I pit the induction account against an operant account which argues the responses to the EXT lever can be regarded as an operant, when just interpreting subjects change their discriminative stimulus from a just-reinforced location to the cue lights as a function of time since reinforcement. The prediction by the induction account got a support from the obtained results over the one by the operant account.

    
    
  • Jose Burgos (University of Guadalajara)"Autoshaped Impulsivity in a Neural-Network Model and Pigeons"
    

    Autoshaped impulsivity is the preference for a cue previously paired with small reward after a short delay, over a cue previously paired with a large reward after a long delay. As in autoshaping, the reward is independent of, and does not elicit, the response. This phenomenon was simulated in a feedforward artificial neural network with two hidden layers. The cues and reward were simulated as separate input activations. Reinforced trials of the two cues were randomly intermixed. The reward did not depend on the output activations, which simulated response-independent reinforcement. The network had two unconnected output units, one for each cue, to simulate two mutually compatible responses. The reward activated neither output unit. An output unit could be activated (via the hidden layers) only by its corresponding cue after learning (weight gain by the appropriate connections). In nonreinforced choice test trials of the two cues presented concurrently, the network preferred the cue that had been paired with the small reward after a short delay. To test this prediction with animals, six pigeons received an analogous procedure. The results confirmed the simulation, suggesting that Pavlovian contingencies could contribute to operant impulsivity.

    
    
  • Gregory Madden (Utah State University)"Experimental Manipulations of Delay Discounting"
    

    Steeply discounting the value of delayed outcomes is robustly correlated with addictions and poor health decision-making. Longitudinal studies suggest that this form of impulsivity precedes and predicts acquisition of substance use, and animal studies reveal a similar pattern. Although delay discounting shows trait-like stability and generality, it is also clear that acute and chronic manipulations can influence this form of impulsive choice. This presentation will summarize the efforts of our lab to experimentally reduce impulsive choice in rodents. The short- and long-term effects of these manipulations will be discussed, as will the potential of these manipulations to reduce drug self-administration.

    
    
• 指定討論：丹野 貴行（明星大学）
  
  
  
• 企画：　坂上貴之（慶應義塾大学）、山口哲生（東邦大学）、八賀洋介（慶應義塾大学）
• 連絡先：　八賀 洋介　yosuke_hachiga at hotmail.com （at を@ に変換してください）

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