Neurophysiological evidence for two processing times for visual object identification

Abstract

Event-related brain potentials (ERPs) were recorded to fragmented pictures of objects that were named correctly or were not to investigate the time course of visual object identification. The first ERP difference distinguishing identified from unidentified pictures estimates the upper limit of the time by which human brain regions have begun to activate long-term memory (LTM) representations specifying the identity of a visual object. Data from 15 young adults indicate that this time varies with the extent to which object parts are recoverable from the visual input, being ∼200 ms earlier with recoverable than unrecoverable parts. Successful identification is evident by ∼300 ms when object parts and overall structural configuration are readily recoverable but not until ∼550 ms when object parts are difficult or impossible to recover (i.e. too poorly specified by the available contours to be recovered). In both cases, successful identification is associated with greater relative positivity. However, unidentified recoverable pictures are associated with an enhanced frontal negativity (N350), linked to object matching operations, not seen for non-recoverable pictures. Taken together, these results implicate two distinct processing sequences in the successful identification of visual objects.

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

“…The N350 marks the first ERP divergence with categorization success, being smaller for correctly categorized than unidentified objects, and is sensitive to the recoverability of perceptual structure (e.g., Schendan & Kutas, 2002;McPherson & Holcomb, 1999). The visual knowledge enabling this categorization ability is a kind of generic memory, that is, explicit memory which is not episodic, such as for recognition and recall tasks, but rather for semantic or nonsemantic (i.e., perceptual) information or facts, regardless of a temporal event context (Hintzman, 1978).…”

“…For example, occipito-temporal activity and the N350, but not the P150-N170, differ substantially between objects that are correctly categorized into a known class (e.g., dog, car, or sofa) relative to unidentified objects and between repeated and new items (e.g., Henson et al, 2004;Schendan & Kutas, 2002, 2003Avidan et al, 2002;Bar et al, 2001;Grill-Spector, Kushnir, Hendler, & Malach, 2000;Grill-Spector et al, 1999;James, Humphrey, Gati, Menon, & Goodale, 1999;Buckner et al, 1998;Schendan et al, 1998). In addition, backward masking, which is thought to disrupt the recurrent neural processes that support phenomenological consciousness (Lamme & Roelfsema, 2000), impairs categorization performance and attenuates the N350 but not the P150-N170 (Bacon-Mace, Mace, Fabre-Thorpe, & Thorpe, 2005;Jeffreys, 1996).…”

“…The LPC is large and broadly distributed across the head, has an extended duration, and multiple intracranial sources reflecting multiple categorization, memory, and response-related processes (Guillem, N'Kaoua, Rougier, & Claverie, 1995). Like the earlier N350, the LPC varies with categorization success, however, unlike the N350, the LPC shows categorization modulations for any image, regardless of part recoverability, and may index a fronto-parietal network for secondary categorization-related processes, such as selection of an appropriate response, including a name (Schendan & Kutas, 2002). Although LPC repetition effects could reflect implicit memory for these later categorization processes, most evidence relates these effects to conscious recollection (Duarte et al, 2004;Paller et al, 1995).…”

“…The hypothesized functional significance of the ERP component modulated can be used to interpret each ERP repetition effect. For the present experiments, the components of interest were: (1) early potentials (300 msec or less) reflecting sensory and perceptual processing, for which the results have been described elsewhere (Schendan & Kutas, in press); (2) the frontocentral N350 between 300 and 400 msec proposed as a neurophysiological marker of the object model selection system and object PRS (Schendan & Kutas, 2002, 2003; (3) the posterior N400 between 400 and 500 msec thought to reflect semantic processing and conceptual implicit memory (Rugg et al, 1998); and (4) a late positive complex (LPC) after 500 msec, encompassing a P600 peak, reflecting secondary categorization-related processes (Schendan & Kutas, 2002) and/or recollection from episodic explicit memory (Duarte, Ranganath, Winward, Hayward, & Knight, 2004;Paller, Kutas, & McIsaac, 1995).…”

Neuroimaging evidence for object model verification theory: Role of prefrontal control in visual object categorization

“…For instance, the human brain responds differently to images of any common object versus any face within 125 ms and to specific instances of correctly classified common objects versus unidentified objects within 200-300 ms (Schendan et al, 1998;Schendan and Kutas, 2002). This remarkable speed of processing has led many theorists to focus on fast bottom-up processes during object categorization, thought to be implemented in neural structures of the ventral visual pathway (Biederman, 1987;Grill-Spector and Malach, 2004;Perrett and Oram, 1993;Poggio and Edelman, 1990;Riesenhuber and Poggio, 2002;Rousselet et al, 2003;Wallis and Rolls, 1997).…”