Hippocampal gamma oscillations by sucrose instrumental memory retrieval in rats across sleep/wake cycle. (25th September 2020)

• Record Type: Journal Article
• Authors: Padovani, Laura; Tesoriero, Chiara; Vyssotski, Alexei; Bentivoglio, Marina; Chiamulera, Cristiano
• Is Part Of: Neuroscience letters. Volume 736(2020)
• Publication Date: 2020-09-25
• Subjects: Reactivation -- Reconsolidation -- Memory -- Hippocampus -- CA1 -- LFP; Neurology -- Periodicals; Neurology -- Periodicals; Research -- Periodicals; Neurologie -- Périodiques; Neuroanatomie -- Périodiques; Neuropharmacologie -- Périodiques; Neurophysiologie -- Périodiques; Neurology; Periodicals; Electronic journals; 617.48
• DOI: 10.1016/j.neulet.2020.135255
• Languages: English
• ISSNs: 0304-3940

Abstract

Highlights: Appetitive instrumental memories can be reactivated, returning to a labile state. Instrumental memory retrieval may affect CA1 gamma power in awake/sleep phases. CA1 gamma power correlates with reactivation rate of responding during awake phase. CA1 gamma power decreases during instrumental memory retrieval in sleep phase. Hippocampal gamma band changes may be a marker of appetitive memory reactivation. Abstract: Memory reconsolidation is a process allowing previously consolidated memories to be updated. In order for memory reconsolidation to occur, a memory first needs to be reactivated. It has been shown recently that memory retrieval during awake/sleep phases may affect susceptibility to memory reactivation. Given the importance of hippocampal gamma frequencies in memory processes, the purpose of the present research was to study changes in gamma bands power during retrieval of instrumental appetitive memories. Local field potentials were recorded in the CA1 area of dorsal hippocampus of Sprague Dawley rats during retrieval of instrumental appetitive memory performed either during light or dark phases of the circadian cycle. Appetitive memory retrieval was performed by using a protocol of sucrose self-administration in operant chambers equipped with levers (Piva et al., 2018): rats were first trained to self-administer sucrose pellets and, after a 14-days forced abstinence stage, memory retrieval stage consisted in training context exposure. At the retrival stage performed during the light phase, a decreased low-gamma power was observed in CA1 when rats were not lever pressing compared to when they were lever pressing (actual instrumental memory retrieval). Moreover, results showed an inverse correlation between gamma power and rate of responding when retrieval was performed in the dark phase. Our findings suggest that hippocampal gamma power is differently modulated when retrieval is performed during the light phase compared to the dark phase. Further investigations should explore the role of gamma oscillations as potential markers of instrumental appetitive memory reactivation in both light and dark conditions.