001 ± 0.041 SEM; Vcarb/tail = 0.096 ± 0.031; Vamph = 0.031 ± 0.019; V ureth = −0.032 ± 0.09; pureth = 0.9; pcarb/tail = 0.025; pamph = 0.043; pMK = 0.7; t test). With EV, we observed significant replay after stimulation only in the amphetamine condition Adriamycin manufacturer (p < 0.05; paired t test), although EV had a tendency to have higher values than the control data (reverse EV)

for other experimental conditions (see Figures S6B–S6E). It should be noted that EV is insensitive to fine-scale temporal spiking patterns and thus provides different information from that obtained with latency measures or template matching. Memory formation is one of the most important processes in the brain, yet the neuronal dynamics underlying this process are only beginning to be understood, partly due to the technical

difficulty of recording from large neuronal populations in behaving animals. Here, we report that the hallmarks of memory formation and memory replay—stimulus-induced sequential activity patterns that reactivate spontaneously—can also be observed in urethane-anesthetized rats. In this preparation, AG-014699 mw population recordings and other brain manipulations can be more easily performed, thus providing a convenient model for electrophysiological study of mechanisms, leading to formation of sequential patterns implicated in memory processes. Furthermore, we found similar replay in both somatosensory and auditory cortices, suggesting this may be a general mechanism in the cortex. Although previous studies using voltage-sensitive dye imaging in anesthetized animals have shown that ongoing Mephenoxalone spontaneous activity can reflect stimulus-evoked spatial patterns on a coarse spatial scale (Han et al., 2008 and Kenet et al., 2003), our findings provide a major refinement of these results by demonstrating replay of fine-scale sequential spiking patterns (Figures 2 and 3) that is more analogous to sequential spiking patterns observed during memory replay in freely moving animals

(Euston et al., 2007, Hoffman and McNaughton, 2002, Kudrimoti et al., 1999, Skaggs and McNaughton, 1996 and Wilson and McNaughton, 1994). In addition, our study indicates the importance of brain state during stimulus presentation. Although multiple studies show that most memory replay occurs during synchronized states (e.g., during slow wave sleep; Battaglia et al., 2004 and Xu et al., 2012), the importance of the brain state during encoding is not clear. It is known that electrically evoked LTP is suppressed in this state ( Leonard et al., 1987), so there is a precedent for our current finding that presentation of stimuli during a desynchronized state as compared to the synchronized state is significantly more effective in inducing lasting reorganization of temporal patterns ( Figures 2 and 6), which subsequently results in stronger spontaneous replay of stimulus-induced patterns.