Neurophysiological Evidence for the Time Course of Activation of Global Shape, Part, and Local Contour Representations during Visual Object Categorization and Memory

Abstract

Abstract& Categorization of visual objects entails matching a percept to long-term representations of structural knowledge. This object model selection is central to theories of human visual cognition, but the representational format(s) is largely unknown. To characterize these neural representations, eventrelated brain potentials (ERPs) to fragmented objects during an indirect memory test were compared when only local contour features, but not global shapes of the object and its parts, differed between encoding and retrieval experiences. The ERP effects revealed that the format of object representations varies across time according to the particular neural processing and memory system currently engaged. An occipitotemporal P2(00) showed implicit memory modulation to items that repeatedly engaged similar perceptual grouping processes but not items that merely reinstantiated visual features. After 500 msec, memory modulation of a late positive complex, indexing secondary categorization and/or explicit recollection processes, was sensitive to local contour changes. In between, a frontocentral N350, indexing the model selection and an implicit perceptual memory system, showed reactivation of object representations whenever the same global shapes were reactivated, despite local feature differences. These and prior N350 findings provide direct neurophysiological evidence that the neural representations supporting object categorization include knowledge beyond local contours and about higher-order perceptual structures, such as the global shapes of the object and its parts, that can differ between object views. The N350 is proposed to index a second state of interactive, recurrent, and feedback processing in occipital and ventral temporal neocortex supporting higherorder cognitive abilities and phenomenological awareness with objects. &

Neurophysiological evidence for transfer appropriate processing of memory: Processing versus feature similarity

“…By contrast, priming of RTs and later ERPs in both experiments (see Schendan & Kutas, 2007) suggest that the impact of feature overlap on memory-related processes occurs after 300 msec. All studied objects show some RT priming, with the most for same fragments, as was previously reported for objects spontaneously categorized correctly (Snodgrass et al, 1996), as were those herein.…”

At your own peril: An ERP study of voluntary task set selection processes in the medial frontal cortex

“…The target evoked a series of ERP components that differed in amplitude between choice and no-choice conditions, including the N210-P210-that is, a posterior lateral N210 and its polarity reversed fronto-central P210 (Joyce & Rossion, 2005;Schendan & Kutas, 2007)-and a centro-parietal P3 component. There is broad evidence that both components are involved in target-related processing (e.g., Kok, 2001).…”

“…There is broad evidence that both components are involved in target-related processing (e.g., Kok, 2001). The N210-P210 complex has been argued to reflect early sensory-perceptual processing (Schendan & Kutas, 2007). For example, Schendan and Kutas have provided evidence that the N210-P210 reflects an initial processing stage (i.e., a fast feedforward sweep that supports lower order image classification abilities) during which object parts are activated.…”

Electrophysiological evidence for colour effects on the naming of colour diagnostic and noncolour diagnostic objects

“…Based on our previous findings, we predicted that the ERP associated with black-and-white, compared to color, stimuli would elicit a more positive P1 and a more negative N1 response over occipital sites for both color and non-color diagnostic objects during object recognition. Schendan and Kutas (2007a) proposed a two-state interactive account for visual object knowledge. First, a system supporting lower-order visual image classification, indexed by the N1 component, is activated.…”