We speculate that these neuroanatomical changes could be the reason why spontaneous activity, which propagates through the same cortical circuits as evoked activity,

becomes more similar to previously presented evoked patterns. We also speculate that the reverbatory activity described here may relate to memory formation in behaving animals. Although the mechanisms underlying memory formation processes are still not well Bortezomib order understood, there is a body of theoretical work going back to Hebb (1949) and Marr (1971) that predicts reverberation (Hebb) and/or reactivation (Marr) as fundamental components of memory consolidation. Such phenomena have since been observed in the hippocampus and cortex of behaving animals (Euston et al., 2007 and Wilson and McNaughton, 1994). These observations, like ours, are consistent with the theory see more but do not demonstrate that memory depends on this replay. However, more recent evidence suggests a direct link between replay and memory. In hippocampus, the reverberation (reactivation) is associated with SPWR events, and studies have now shown that memory is impaired when SPWRs are disrupted immediately following training (Girardeau et al.,

2009 and Ego-Stengel and Wilson, 2010). Furthermore, there are individual differences in reactivation and memory performance, and these are correlated (Gerrard et al., 2008). These data suggest that the replay of task-related activity is involved in memory processes. Note also that our experiments follow the same general design as “classic” Mephenoxalone reactivation experiments (Wilson and McNaughton, 1994). We have a control period before an experience, a repetitive experience, followed by a test period. We show that the activity in the test period resembles the activity in the repetitive experience after controlling for any pre-existing similarity. The only difference is that the

animal is not actually behaving but rather under anesthesia. By the fundamental definition of memory as a recapitulation of neural activity evoked by an experience, this is memory. Thus, we suggest that replay of stimulus-evoked patterns observed in desynchronized brain states in urethane-anesthetized rats could be a useful model for studying mechanisms of memory. We used surgery and recording procedures that have been previously described in detail (Luczak et al., 2007 and Schjetnan and Luczak, 2011). Briefly, for somatosensory experiments, 11 Long Evans rats (400–900 g) were anesthetized with urethane (1.5g/kg intraperitoneally [i.p.]). Rats were then placed in a stereotaxic frame, and a window in the skull was prepared over primary somatosensory cortex (S1) hindlimb area (anteroposterior 1 mm; mediolateral 2 mm; dorsoventral 1.5 mm). For auditory experiments, eight Long Evans rats (250–350 g) were anesthetized with urethane (1.5g/kg i.p.) and placed in a nasal restraint that left the ears free. A window in the skull (2 × 3 mm) was prepared over the primary auditory cortex (Luczak et al.