Thus, PD-0332991 cell line because the boost in slow fluctuations in the intact-movie is widespread, it may reflect a process in which sensory and higher order areas work together to understand

a temporally complex real-life stimulus. What is the origin of the slow fluctuations of power observed in sensory and higher order cortical regions? One mechanism for lengthening time-constants is to introduce recurrent feedback into a neural circuit (Brody et al., 2003; Durstewitz et al., 2000; Shu et al., 2003; Wang, 2002). Differences in the tuning of recurrent activity could account for the differences in the amplitude of slow fluctuations across brain regions. However, we cannot rule out other causes for slow neural change, such as short-term synaptic plasticity (Zucker and Regehr, 2002) or relaxation processes in membrane excitability (Marom, 1998). In addition, slow fluctuations of power are coupled across brain regions even in the absence of stimulation (Leopold and Maier, 2012; Leopold et al., 2003; Nir et al., 2008; Schölvinck et al.,

2010), which indicates that the dynamic timescale of each region is influenced check details by interregional interactions. Although their mechanistic basis is uncertain, the slow fluctuations of power are reliable across stimulus repetitions (Figure 7A), which immediately suggests that they are not simply noise. In addition, the slow dynamics in response to the intact stimulus were significantly more reliable than those evoked by the scrambled stimulus, which lacks the contextual information structure of a real-life narrative. Finally, the faster fluctuations of broadband power showed a much smaller change in reliability between the intact and scrambled stimuli (Figure 7B). These data suggest a connection between slow fluctuations of neuronal population Terminal deoxynucleotidyl transferase activity and temporally extended information processing. Similarly, it has been proposed that

slow changes in the spatial pattern of high-frequency power reflect a gradually drifting mental context (Manning et al., 2011). If slow fluctuations of power reflect a drifting mental context, this may explain why they are larger and more reliable during the intact movie, whose context shifts gradually as narrative information is accumulated. We have focused on the slow fluctuations that compose the dominant portion of the variance in neural activity (Figure 6, and see Leopold et al., 2003). Firing rates and high-frequency power are not only modulated on these slow timescales: they also vary with the phase of cortical rhythms on the scale of tens to hundreds of milliseconds (Canolty et al., 2006; He et al., 2010; Miller et al., 2010; Murthy and Fetz, 1992; Osipova et al., 2008; Panzeri et al., 2010).

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