Abstract
Oscillating waves during sleep play an essential role in memory consolidation. The cortical slow wave activity (SWA) and sigma waves during NREM sleep and theta waves during REM sleep increase after a variety of memory tasks including declarative, procedural and associative learning tasks. These oscillatory waves during sleep help to promote neural dialog between circuitries, which possibly plays a causal role in memory consolidation. However, the role of sleep-associated oscillating waves in a complex appetitive-conditioning paradigm is not clear. The parietal cortex and amygdala are involved in the cognitive evaluation of the environmental stimuli, and appetitive conditioning. Here, we have studied the changes in sleep architecture and oscillatory waves during NREM and REM sleep in the parietal cortices and amygdalar-local field potential (A-LFP) after appetitive-conditioning in the rat. We observed that REM sleep increased significantly after appetitive conditioning, which significantly positively correlated with performance on the appetitive-conditioning task. Further, the cortical SWA (0.1–4.5 Hz), and sigma (12–14.25 Hz) waves during NREM sleep, theta (6–9 Hz) waves during REM sleep, the amygdalar SWA (0.1–3.75 Hz) during NREM sleep and theta (6–8.25 Hz) waves during REM sleep significantly increased after appetitive conditioning. Interestingly, the augmented oscillatory waves significantly positively correlated with the performances on the appetitive-conditioning task. Our results suggest that the augmented REM sleep after conditioning may be required for the consolidation of appetitive-conditioned memory. Further, a significant correlation between augmented power in oscillatory waves during sleep and performance suggesting that these waves may be playing a crucial role in the consolidation of appetitive-conditioned memory.
Highlights
The connection between sleep states and memory processes has been of great interest (Maquet et al, 2003)
It has been reasoned that NREM sleep, which appears with spindles and oscillatory waves, possibly offers the neuronal network a favorable state for the induction of synaptic plasticity, which in turn, helps in memory consolidation (Sejnowski and Destexhe, 2000; Steriade and Timofeev, 2003)
We observed that slow wave activity (SWA) and sigma waves during NREM sleep, and theta waves during REM sleep significantly increased in the cortical brain areas after learning the appetitive conditioning task
Summary
The connection between sleep states and memory processes has been of great interest (Maquet et al, 2003). Increase in REM sleep has been observed after learning a variety of tasks, such as, negative and positive reinforcement task, spatial learning task, avoidance task, classic aversive and appetitive conditioning task in rodents (Smith and Rose, 1997; Walker, 2009; Chowdhury et al, 2011; Rasch and Born, 2013; Tripathi and Jha, 2016) and visual discrimination and procedural learning tasks in humans (Stickgold et al, 2000; Peigneux et al, 2003) These studies suggest that NREM and REM sleep may play a distinctive role in the processing of learning information about different tasks. It has been reasoned that NREM sleep, which appears with spindles and oscillatory waves, possibly offers the neuronal network a favorable state for the induction of synaptic plasticity, which in turn, helps in memory consolidation (Sejnowski and Destexhe, 2000; Steriade and Timofeev, 2003)
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