Year: 2020
Type: dissertation
Abstract: Previous work indicates that the infralimbic cortex (IL) mediates extinction learning and actively suppresses cocaine-seeking during reinstatement, following cocaine self-administration. Despite extensive work supporting this role for IL activity, how and under exactly which conditions the IL negatively modulates cocaine-seeking behavior remains unclear. The present experiments utilized optogenetics and in vivo electrophysiology to probe the role of the IL in modulating cocaine seeking following cocaine self-administration. Rats underwent 6 h-access cocaine self-administration followed by home-cage withdrawal or extinction training. Optogenetic manipulations were employed during cocaine seeking sessions and reinstatement. In vivo electrophysiological recordings were conducted during self-administration, extinction and reinstatement. Results indicated that optogenetic potentiation of IL activity did not alter cocaine seeking following home-cage withdrawal. However, following extinction training, the same manipulation attenuated cocaine seeking. These results suggested that the ability of the IL to attenuate cocaine seeking depends, at least in part, on rats previously having undergone extinction training. Electrophysiological recordings revealed that theta rhythms dominated IL local field potential activity during all experimental stages. During extinction, theta power was lower in trials when cocaine-seeking behaviors were expressed, compared to trials when cocaine seeking was suppressed. These data are consistent with the possibility that IL theta power reflects cognitive control processes, and that lever pressing during extinction is related to diminished cognitive control. Results further indicated heterogeneity in IL single unit activity, including IL pre-motor units the activity of which is predictive of lever pressing or the inhibition thereof. In the context of the existing literature, the present results indicate that inhibiting cocaine seeking is indeed one of the functions of the IL, however this capacity depends on the animal’s learning history and task demands. Furthermore, electrophysiological results suggest modularity in IL activity, which may help explain the inconsistencies observed regarding IL function in relation to different tasks demands.
DOI: 10.17077/etd.005390
Language: English
Subfield: Cellular and Molecular Neuroscience
Field: Neuroscience
Domain: Life Sciences
Open Access status: green
OpenAlex ID: W4248046899