The observation that correlations with the audio envelope decrease from early to higher order auditory processing areas is consistent with hierarchical models of auditory processing in which early auditory areas encode the lower level acoustic properties while higher order areas extract more abstract information (Chevillet et al., 2011; Hickok and Poeppel, 2004; Pallier et al., 2011). Previous work suggests that the capacity to accumulate information over time increases gradually from early sensory areas to higher

order perceptual and cognitive areas (Hasson et al., 2008; Lerner et al., 2011). Therefore, the gradient of weakening audio correlations within the STG should correspond to a gradient NVP-BKM120 clinical trial of lengthening temporal receptive windows (TRWs). To examine this relationship in our data, we defined the “TRW index” of each electrode as the difference of its repeat reliability for the intact and fine-scrambled movie clips. Thus, TRW(i) = rINTACT(i) − rFINE(i) where rINTACT(i) and rFINE(i) are the repeat reliability of the i-th electrode in the intact and fine-scrambled conditions ( Figure 4A, bottom inset). Within the STG, areas with longer TRWs exhibited RG7204 datasheet smaller audio correlations (Figures 4A–4C). A strong and significant anticorrelation was found between the TRW index of each electrode in the STG and the strength

of its coupling to the intact movie soundtrack (Figure 4B, black dashed line; r = −0.62,

p = 0.010, n = 16) and scrambled movie soundtrack (Figure 4B, green dashed line; r = −0.51, p = 0.04, n = 16). These results support the existence of a hierarchy of progressively longer TRWs within the STG. Areas nearer primary auditory cortex have shorter TRWs and are more sensitive to instantaneous transients of the stimulus, while areas with longer TRWs respond less to instantaneous stimulus transients, and more to the long-range temporal structure that is needed to follow the meaning of the story. Within the cerebral cortex as a whole, TRW values tended to be smaller in the vicinity of early sensory cortices and larger in higher order brain regions. Thus, by and large, the broadband response reliability in early auditory and Calpain visual regions was high at all scrambling levels (Figure 4C, blue). By contrast, in higher order areas nearer the anterior fusiform gyrus, the angular gyrus and frontal cortex (Figure 4C, red), the response reliability to the intact clip was larger than the reliability to the scrambled clips. Three visual electrodes exhibited significantly greater reliability for the scrambled movie than for the intact movie clip, possibly because the discontinuous fine-scrambled condition provided more opportunities to respond to the onset of a preferred stimulus. We confirmed the presence of a TRW gradient by clustering electrodes into regions of interest (ROIs) based on their anatomical location (Figure 5A).