The hierarchical organization of visual cortex is such that higher visual areas take time to integrate information relayed from early visual areas (Einhauser et al., 2007, Todd et al., 2011). As such, while a faster stream of novel pictures (e.g. 4 frames/s) increases sensory stimulation and can elicit more activation in higher visual areas, further increasing presentation rate (e.g.

15 frames/s) will result in failure to adequately process complex information, giving rise to an inverted u-shaped temporal response profile. Using this approach, the parahippocampal place area (PPA) and fusiform face areas (FFA) whose response profiles peak at the slower rates relative to earlier visual areas have been identified as bottlenecks for visual processing 11 and 12]. Lowered rate of visual processing in SD is evidenced by a slower peak rate in the temporal SCH772984 chemical structure response profile in the PPA compared to in the well rested state click here [13•]. The PPA and FFA lie in extrastriate visual cortex and are relatively more sensitive to the degradation of top-down control of attention encountered during SD. In contrast, early visual areas where processing is not limited at the presentation frequencies tested

and which are less sensitive to attentional modulation, demonstrate a monotonic increase in activation with presentation rate irrespective of state (Figure 1). Hence, visual areas that serve as potential bottlenecks for visual

processing Idoxuridine in the sleep-deprived state can been identified. Selectivity for object pictures can be measured by examining the difference in PPA responses to attended and unattended house pictures. This index of selectivity is lowered in sleep-deprived persons, when picture stimuli are temporally unpredictable [14]. However, when face and house stimuli appear in a temporally predictable manner, SD results in reduced PPA activation but without an accompanying change in selectivity [15]. This relative improvement in behavioral performance when stimuli are temporally predictable is consistent with similar effects found with vigilance in the well rested state [16]. Reduced spatial selective attention in SD also occurs in the preparatory period preceding stimulus onset and manifests in retinotopically specific visual cortex [17]. The latter indicates that effects of SD manifest in brain areas specifically engaged in the task and are not evident when these areas are not specifically probed. Deficits in attention evidenced by reduced fronto-parietal activation in association with degraded performance are also evident in visual tracking tasks that evaluate deployment of selective attention over a longer period than that spanned by a brief experimental trial 18 and 19•]. These point to a temporally more extensive loss of top-down control of attention than apparent from tests of psychomotor vigilance.