Nakamura K, Ono T, Tamura R, Indo M, Takashima Y, Kawasaki M
Department of Physiology, Faculty of Medicine, Toyama Medical and Pharmaceutical University, Japan.
Brain Res. 1989 Jul 3;491(1):15-32. doi: 10.1016/0006-8993(89)90084-x.
Single unit activity in the lateral hypothalamus (LHA) of the rat was recorded while the animal learned to discriminate cue signals. Normally preferred potables (glucose, orange, or grape solution) or intracranial self-stimulation (ICSS) were used as rewards. Electric shock or tail pinch were used as aversive stimuli. The same behavior, licking, was the response required to either obtain the rewarding stimuli or avoid the aversive ones. For positive reinforcement a rat was rewarded with fluid or ICSS upon licking a spout presented in front of its mouth. In negative reinforcement experiments, an aversive stimulus, electric shock or tail pinch, was applied if the rat did not lick the spout. Solutions having smell only, taste only, or smell-plus-taste, were prepared from oranges or grape extract. Of 392 neurons analyzed, 256 responded differentially to rewarding and aversive stimuli, and 138 of these were tested with the 3 different solutions. Similar LHA neural responses occurred during actual drinking of the 3 kinds of solutions, as well as on recognition of the cue signal. Responses to smell only had shorter latency than responses to taste only. Neural activity in response to solutions that could be both smelled and tasted was the sum of activity in response to taste-only solutions plus that in response to smell-only solutions. Cue signal responses were rapidly acquired, usually within 2-5 trials, for both taste-only and smell-only solutions. The results indicate the integration of both taste and olfactory information by the same LHA neurons, and these neurons are involved in cue signal learning. Present results of LHA neuronal responses to taste and smell suggest that the intensity of gustation and olfaction may add together to enhance instinctive hedonic sensations. These neurons are involved in the formation of stimulus-reinforcement association in learning, and in elicitation of conditioned emotional responses.
在大鼠学习辨别线索信号的过程中，记录其外侧下丘脑（LHA）的单单位活动。正常情况下，偏好的饮品（葡萄糖、橙汁或葡萄汁溶液）或颅内自我刺激（ICSS）被用作奖励。电击或夹尾被用作厌恶刺激。相同的行为，舔舐，是获取奖励性刺激或避免厌恶刺激所需的反应。对于正强化，大鼠舔舐其嘴前呈现的喷嘴时会得到液体或ICSS奖励。在负强化实验中，如果大鼠不舔舐喷嘴，则施加厌恶刺激，即电击或夹尾。仅具有气味、仅具有味道或兼具气味和味道的溶液由橙子或葡萄提取物制备。在分析的392个神经元中，256个对奖励性和厌恶刺激有不同反应，其中138个用3种不同溶液进行了测试。在实际饮用这3种溶液期间以及识别线索信号时，LHA出现了类似的神经反应。对仅气味的反应潜伏期比对仅味道的反应短。对兼具气味和味道的溶液的神经活动是对仅味道溶液的活动与对仅气味溶液的活动之和。对于仅味道和仅气味的溶液，线索信号反应通常在2至5次试验内迅速习得。结果表明同一LHA神经元整合了味觉和嗅觉信息，并且这些神经元参与线索信号学习。LHA神经元对味觉和嗅觉的当前反应结果表明，味觉和嗅觉的强度可能相加以增强本能的享乐感觉。这些神经元参与学习中刺激 - 强化关联的形成以及条件性情绪反应的引发。
