Neural Substrates of Investigation

Abstract

Social interaction-seeking and food-seeking behaviors are both motivated behaviors that we hypothesize are regulated by overlapping neuronal populations. To test this, we exposed male and female adolescent C57BL/6 mice to either a food stimulus (standard lab chow), a social stimulus (unfamiliar age- and sex- matched mouse), or an empty corral. Before testing, all mice were socially isolated and food-deprived to increase their motivation to investigate the stimuli.

Overall, mice spent more time investigating the food stimulus than the social stimulus, and tended to spend more time investigating the social stimulus than the empty corral. Following the test, the mice were sacrificed and their brains were collected to measure neuronal activation (using Fos induction as a marker) in response to stimulus investigation. We examined activation of orexin neurons in the lateral hypothalamus (LHA) and dopamine neurons in the ventral tegmental area, two neuronal populations shown to regulate motivated behaviors, including social- and food-related behaviors. We observed no significant differences in Fos induction for either neuronal population between groups, suggesting that these populations are not selectively recruited by investigation of social or food stimuli. However, trending positive correlations between medial LHA Fos induction and investigation time in all groups suggests that this population may regulate nonspecific investigation. Examining the same brains, we are currently investigating the activation of another neuronal population implicated in social- and food-related behaviors: oxytocin neurons in the supraoptic and paraventricular hypothalamic nuclei, to continue the search for a neuronal population that regulates social interaction-seeking and food-seeking behaviors.

Click to open in new tab.