Brain regions associated with retrieval of structurally coherent visual information

Abstract

An object's global, three-dimensional structure may be represented by a specialized brain system involving regions of inferior temporal cortex. This system's role in object representation can be understood by experiments in which people study drawings of novel objects with possible or impossible three-dimensional structures, and later make either possible/impossible object decisions or old/new recognition decisions about briefly flashed studied and non-studied objects. Although object decisions about possible objects are facilitated by prior study, there is no corresponding facilitation for impossible objects, thereby implicating a system that is specifically involved in the representation of structurally coherent visual objects. Here we show, by positron emission tomography (PET), that increases in blood flow in inferior temporal regions are associated with object decisions about possible but not impossible objects, and that there are increases in the vicinity of the hippocampal formation associated with episodic recognition of possible objects.

Global familiarity of visual stimuli affects repetition-related neural plasticity but not repetition priming

“…This interpretation would be consistent with the component process model's proposal that RE reflects the formation of new memory representations. Importantly, this study also demonstrates that RE effects for U stimuli need not be of a perceptual nature, as suggested by prior studies (Fiebach, et al, 2005;Henson, et al, 2000;Schacter et al, 1995;Thiel, et al, 2002), but may reflect the learning of more abstract (i.e., lexical) information. It is unclear, however, from the current data set, whether these RE (and RS) effects directly contributed to the observed behavioral priming effects or simply cooccurred with them.…”

“…This finding has implications for prior studies that have postulated a laterality difference in the functional organization of occipital-temporal cortex, particularly fusiform gyrus (Koutstaal, et al, 2001; Marsolek, 1999;Simons et al, 2003;Vuilleumier et al, 2002). In this view, the left fusiform is specialized for representing more abstract visual form and lexical/semantic information and shows neural plasticity only for F objects, whereas the right fusiform gyrus is specialized for representing form-specific visual properties and shows neural plasticity for both F and U objects (Fiebach et al, 2005;Schacter et al, 1995;Vuilleumier et al, 2002). In the present study, the dominant latent spatial pattern contributed a similar RS effect for both object types in left and right fusiform gyrus for F and U objects ( Figure 6).…”

“…Other studies examining repetition priming of unfamiliar stimuli have reported increases in neural activity, or repetition enhancement (RE), in occipital-temporal cortex for repeated stimuli, including unfamiliar faces (Henson, Shallice, & Dolan, 2000;Thiel, Henson, & Dolan, 2002), meaningless symbols (Henson et al, 2000), line drawings of novel 3D objects (Schacter et al, 1995), and pseudowords (Fiebach, Gruber, & Supp, 2005). At least two of these studies (Fiebach et al, 2005;Schacter et al, 1995) only found RE and no RS in occipital-temporal Henson et al (2000) and Thiel et al (2002) did not report whether there were any regions that showed RS for the unfamiliar stimuli.Interestingly, both those studies finding RS and those finding RE for unfamiliar stimuli have reported fewer locations of significant neural repetition effects (either RS or RE) for unfamiliar stimuli compared to familiar ones. Thus, those studies reporting RS for both familiar and unfamiliar stimuli within the same task (van Turennout et al, 2000;Vuilleumier et al, 2002) have found that RS for unfamiliar objects was confined to more posterior regions of occipitaltemporal cortex, whereas RS for familiar stimuli encompassed both posterior and anterior of occipital-temporal regions as well as inferior frontal regions.…”

“…Consistent with the view that RS is a general mechanism that mediates repetition priming of all stimulus types, independent of stimulus familiarity, several studies have demonstrated repetition priming accompanied by RS in occipital-temporal cortex for non-sense (i.e., nonnameable) objects (Habeck, et al, 2006;van Turennout et al, 2000;Vuilleumier et al, 2002) and unfamiliar faces (Pourtois, Schwartz, Seghier, Lazeyras, & Vuilleumier, 2005). Other studies examining repetition priming of unfamiliar stimuli have reported increases in neural activity, or repetition enhancement (RE), in occipital-temporal cortex for repeated stimuli, including unfamiliar faces (Henson, Shallice, & Dolan, 2000;Thiel, Henson, & Dolan, 2002), meaningless symbols (Henson et al, 2000), line drawings of novel 3D objects (Schacter et al, 1995), and pseudowords (Fiebach, Gruber, & Supp, 2005). At least two of these studies (Fiebach et al, 2005;Schacter et al, 1995) only found RE and no RS in occipital-temporal cortex for the unfamiliar stimuli, while Henson et al (2000) and Thiel et al (2002) did not report whether there were any regions that showed RS for the unfamiliar stimuli.…”

Neurophysiological evidence for two processing times for visual object identification

“…We speculate that the neuroanatomical locus of the neural processes indexed by the N350 identification effect is in occipitotemporal and mid-fusiform regions [13] implicated in shape representation and identification functions that may be consciously assessable [12,[16][17][18]22,24,25,28,32,38,44,49,57], as the related Ncl has been localized to these areas. Many brain regions seem to contribute to LPC effects [19], such as temporal regions linked to object knowledge and naming processes [12].…”