The activity of neurones in the lateral hypothalamus and zona incerta of the sheep responding to the sight or approach of food is modified by learning and satiety and reflects food preference.
Single unit recordings were made from neurones in the lateral hypothalamus and zona incerta of conscious sheep during the static visual presentation of food or visible approach of food towards the animal's mouth. The ability of this population of neurones to modulate their activity as a result of learning and satiety was investigated together with the extent to which their responsiveness reflected individual food preference. These neurones did not respond to either the sight or visible approach of a nonsense object or a food which they would not eat. Further, when the sight or approach of food which the animal desired to eat was not paired with ingestion the neurones rapidly extinguished their response. The magnitude of the neuronal response and the number of trials to extinction was dependent upon the animal's preference for a particular food: the most preferred food evoking the greatest response and being the most resistant to extinction. Following extinction the neuronal response to the sight or approach of food could be re-established after one or two trials with food reinforcement. If the sheep was repeatedly given the same food to eat the magnitude of the neuronal response and the number of trials to extinction gradually declined until no response occurred when the animal refused to eat. These cells could also be induced to respond differentially to the approach of non-food objects dependent upon whether they were associated with a food reward or not. Thus a response could be evoked to the sight or approach of a black bottle if it was associated with a food reward but not to a yellow bottle unassociated with feeding.(ABSTRACT TRUNCATED AT 250 WORDS)
D000818:Animals; D001931:Brain Mapping; D003214:Conditioning, Classical / Q000502:physiology*; D004027:Diencephalon / Q000502:physiology*; D005108:Extinction, Psychological / Q000502:physiology; D005260:Female; D005502:Food; D005518:Food Preferences; D007026:Hypothalamic Area, Lateral / Q000502:physiology; D012527:Satiation / Q000502:physiology*; D012528:Satiety Response / Q000502:physiology*; D012756:Sheep; D014796:Visual Perception / Q000502:physiology*