The neural basis of temporal individuation and its capacity limits in the human brain

Abstract

Individuation refers to individuals' use of spatial and temporal properties to register an object as a distinct perceptual event relative to other stimuli. Although behavioral studies have examined both spatial and temporal individuation, neuroimaging investigations of individuation have been restricted to the spatial domain and at relatively late stages of information processing. In this study we used univariate and multivoxel pattern analyses of functional magnetic resonance imaging data to identify brain regions involved in individuating temporally distinct visual items and the neural consequences that arise when this process reaches its capacity limit (repetition blindness, RB). First, we found that regional patterns of blood oxygen level-dependent activity in a large group of brain regions involved in "lower-level" perceptual and "higher-level" attentional/executive processing discriminated between instances where repeated and nonrepeated stimuli were successfully individuated, conditions that placed differential demands on temporal individuation. These results could not be attributed to repetition suppression, stimulus or response factors, task difficulty, regional activation differences, other capacity-limited processes, or artifacts in the data or analyses. Consistent with the global workplace model of consciousness, this finding suggests that temporal individuation is supported by a distributed set of brain regions, rather than a single neural correlate. Second, conditions that reflect the capacity limit of individuation (instances of RB) modulated the amplitude, rather than spatial pattern, of activity in the left hemisphere premotor cortex. This finding could not be attributed to response conflict/ambiguity and likely reflects a candidate brain region underlying the capacity-limited process that gives rise to RB.

Two scenes or not two scenes: The effects of stimulus repetition and view-similarity on scene categorization from brief displays

“…To our knowledge, there is only one previous study that has investigated RB using scene stimuli. This was an fMRI study conducted by Naughtin, Tamber-Rosenau, and Dux (2013), which looked at the neural correlates of token individuation and used scene stimuli because they are associated with a reliable pattern of brain activation (in the PPA). Naughtin et al (2013) asked participants to report whether a three-target RSVP sequence contained a repeated scene, no repetition, or was a Bcatch^trial on which only two scenes were presented.…”

“…This implies that rapidly changing visual input affects processing of objects and words differently to scenes. Some researchers have speculated that RB reflects a heuristic employed by the visual system to deal with its limited rate of temporal updating (Chun, 1997;Kanwisher, 1987;Naughtin et al, 2013). That is, if two identical stimuli appear in the same spatial location at almost the same time, the system Bassumes^that this is the same object, because under most circumstances that is the case-typically, any temporal discontinuity in perceiving the object is due to the observer looking away or blinking, but the object itself has not moved or changed.…”

Attentional Capacity and Limitations

“…Because the RB and AB can be independently affected by a variety of manipulations (Chun, 1997;Dux & Marois, 2007), it is likely that there are multiple attentional capacity limits or bottlenecks even within the realm of temporal attention. Though to our knowledge the neural bases of RB and AB have not been directly compared in a single paradigm, investigation of the neural basis of RB suggests that its capacity limit may be instantiated in distinct parts of the cortex from the capacity limit underlying the AB and SIB, further supporting the view that there are multiple temporal attentional bottlenecks (Naughtin, Tamber-Rosenau, & Dux, 2014).…”