Hippocampal gamma rhythms during Y‐maze navigation in the juvenile rat

Abstract

The neurobiology of postnatal hippocampal development in rodents is receiving increased attention as a means to address neurodevelopmental questions and to better understand the neural code(s) for spatial navigation in adulthood. We previously showed that spontaneous alternation (SA) in a Y-maze, which emerges at the end of the third postnatal week, was related to changes in fast glutamatergic synaptic transmission. In adults, oscillations in the hippocampal local field potential (LFP) (i.e., theta, 4-12 Hz; slow gamma, 25-55 Hz; and fast gamma, 65-100 Hz) have been shown to coordinate the activity of spatially tuned cell types in the hippocampus during route planning and execution. Other investigators have shown that theta activity matures during the first month of life. However, relationships between developmental alterations in gamma oscillations and cognitive function have not been investigated in juveniles, and the impact of developmental changes in excitatory synaptic transmission on network activity remains unclear. We implanted rats at postnatal day 14 to record LFPs from the synaptic layer of area CA1 during Y-maze exploration at postnatal Days 18, 19, 23, and 24. The positive allosteric modulator of AMPA receptors, CX614, or vehicle was administered prior to each test. We found that slow gamma peak frequency, but not peak power, remained constant across this age range. Fast gamma event rate increased with increasing age, while peak frequency decreased.AMPA receptor modulation impacted slow and fast gamma differently at different ages. Furthermore, gamma events showed relationships with novelty and movement speed that differed based on gamma sub-band (slow vs. fast). These results support the presence of environmentally-driven gamma oscillations in hippocampal network activity prior to the end of the third postnatal week of development. Differential refinement of slow and fast gamma occurring across the subsequent week supports involvement in the emergence of spatial navigation ability.

Positive modulation of α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors differentially alters spatial learning and memory in juvenile rats younger and older than three weeks

“…Adult-like spatial learning and memory performance likely emerge at the end of three postnatal weeks in rodents due to changes in network operations that result from alterations to synaptic physiology. Cognitively relevant network oscillations in the theta and fast gamma frequency bands have been shown to increase in power (theta; Langston et al, 2010;Wills et al, 2010) or event rate (fast gamma;McHail and Dumas, 2020) with increasing age near the end of three postnatal weeks in rats. When allowed to freely explore a symmetrical Y-maze, CX614 increased fast gamma peak power in animals just under 3 weeks of age and reduced slow gamma event rate in animals just over 3 of age.…”

“…Injection volumes for vehicle control animals (cyclodextrin mixed as described above without drug) were calculated in the same fashion. Drug doses applied in the current experiments were based on those used in our developmental studies (Blair et al ., 2013; McHail and Dumas, 2020). Drug was delivered intraperitoneally with a 28-gauge syringe (U-100, #329461, BD).…”

Dichrocephala integrifolia Aqueous Extract Antagonises Chronic and Binges Ethanol Feeding-Induced Memory Dysfunctions: Insights into Antioxidant and Anti-Inflammatory Mechanisms

“…Murine models and behavioral tests have become increasingly, key tools in the investigation of ethanol-misuses-induced cognitive dysfunctions [10,24,50]. e Y-maze and the novel object recognition tasks are among the tools widely used in neuroscience to understand the role of di erent brain parts, such as the hippocampus, and the prefrontal cortex, in cognitive functions [38,[55][56][57].…”

Behind the scenes: Are latent memories supported by calcium independent plasticity?

“…Moreover, the model may be expanded by examining the impact of nonionotropic activity on hippocampal place cells, which are less numerous and less stable prior to P21 (Baram, Donato, & Holmes, 2019; Langston et al, 2010; Wills, Cacucci, Burgess, & O'Keefe, 2010). Further, analysis of distinct network oscillations that correspond to specific cognitive processes, and their relationship to hippocampal maturation, might also inform the model (Korotkova et al, 2018; McHail & Dumas, 2020; Wills et al, 2010). In vivo physiological recording in juvenile GluN2 chimeric mice during behavior testing will provide direct insight into how ionotropic and nonionotropic plasticity differentially affect hippocampal network activity and cognitive performance.…”