It is thus possible that serotonin and/or norepinephrine are responsible for producing different directions of rate and excitability changes during waking and REM, PF-06463922 datasheet especially because these neuromodulators have been shown to strongly affect long-term synaptic plasticity (Bliss et al., 1983) and REM sleep deprivation results in impaired synaptic plasticity (McDermott et al., 2006).

Another unexpected observation in our experiments was the parallel changes of decreased global firing rates and increased synchrony during sharp-wave ripples across sleep (Diekelmann et al., 2011). Increased firing rates are typically accompanied by spurious increases in synchrony measures (Perkel et al., 1967). However, in the hippocampus, large, nonlinear increases in population synchrony are brought about by ripples (Buzsáki et al., 1992), and increased synchrony in our experiments occurred almost exclusively during hippocampal ripples. In fact, within non-REM episodes, firing rates between ripples decreased in parallel with the increased participation of neurons in ripples. We hypothesize that the two types of changes, i.e., decreasing firing rates and increased synchrony during the course Dabrafenib nmr of sleep, are due to the same mechanism(s)

since both changes were significantly correlated with the power of theta oscillations during REM episodes. It remains to be demonstrated whether the described sleep-related

firing pattern changes are unique to the hippocampal CA1 region or can be generalized to other cortical regions. According to a current influential model, the most important role of non-REM sleep is to decrease firing rates (Tononi and Cirelli, 2006). Since this prediction is opposite to the present observations in the hippocampus, one potential outcome is that firing rate regulations in the neocortex and hippocampus follow different rules. Another alternative much is that downscaling of neocortical firing rates is also brought about by the intervening REM episodes, as observed in the hippocampus. In either case, the present findings imply a fundamental physiological role for REM sleep. LFP and unit firing were recorded by multiple-shank silicon probes (Mizuseki et al., 2009) from the septal third of hippocampal CA1 region in five male rats. Histological localization of the electrodes, criteria for clustering of single units, and separation of pyramidal cells and interneurons in these animals have been described in detail previously (Mizuseki et al., 2009, 2011). Recordings were carried out in the home cage of the animal during sleep, including several epochs of REM and non-REM episodes, while the behavior of the rat and LFPs from several channels were monitored by the experimenter (Montgomery et al., 2008). Head movements were detected by LEDs mounted on the head stage and recorded by a video camera.