Electrophysiology of taste, feeding and reward in lateral hypothalamus of rabbit

Single-unit responses of LH cells and oral reaction were studied in food-deprived animals to intraoral injections of rewarding and aversive tastants differentially cued by tonal stimuli. Correlative tests were carried out with microstimulation. Classification and statistical analysis of task-related neurons in different AP regions of LH revealed two functionally disparate, anatomically segregated groups of cells that may play a role in hedonic reactions to tastants. A rostral group showed strong "excitatory" response to aversive test stimuli and divergent "inhibitory" or minimal response to rewarding test stimuli. More caudal cells displayed maximal excitatory response to rewarding test stimuli, which, in some cases, related to oral behavior. Microstimulation of caudal sites also evoked rhythmical oral movement. Phasic and/or tonic reactivity to taste stimuli were common among LH neurons, but most cells responded differentially to both conditioned stimuli and tastants. Only a few cells reacted selectively to the fluid stimuli.