Nonvisual and Visual Object Shape Representations in Occipitotemporal Cortex: Evidence from Congenitally Blind and Sighted Adults

Abstract

Knowledge of object shape is primarily acquired through the visual modality but can also be acquired through other sensory modalities. In the present study, we investigated the representation of object shape in humans without visual experience. Congenitally blind and sighted participants rated the shape similarity of pairs of 33 familiar objects, referred to by their names. The resulting shape similarity matrices were highly similar for the two groups, indicating that knowledge of the objects' shapes was largely independent of visual experience. Using fMRI, we tested for brain regions that represented object shape knowledge in blind and sighted participants. Multivoxel activity patterns were established for each of the 33 aurally presented object names. Sighted participants additionally viewed pictures of these objects. Using representational similarity analysis, neural similarity matrices were related to the behavioral shape similarity matrices. Results showed that activity patterns in occipitotemporal cortex (OTC) regions, including inferior temporal (IT) cortex and functionally defined object-selective cortex (OSC), reflected the behavioral shape similarity ratings in both blind and sighted groups, also when controlling for the objects' tactile and semantic similarity. Furthermore, neural similarity matrices of IT and OSC showed similarities across blind and sighted groups (within the auditory modality) and across modality (within the sighted group), but not across both modality and group (blind auditory-sighted visual). Together, these findings provide evidence that OTC not only represents objects visually (requiring visual experience) but also represents objects nonvisually, reflecting knowledge of object shape independently of the modality through which this knowledge was acquired.

Multisensory Part-based Representations of Objects in Human Lateral Occipital Cortex

“…The resulting representational similarity analysis quantifies the similarity of voxel patterns across modalities, comparing every object to every other object as well as to itself. Previous studies have calculated neural similarity matrices separately for each modality and then subsequently correlated those matrices (e.g., Peelen et al, 2014). Such an approach amounts to showing that neural correlations among objects in one modality correlate with the neural correlations among objects in another modality.…”

“…Previous research shows that LOC represents visual information about object shape (Grill-Spector, Kourtzi, & Kanwisher, 2001; Kourtzi & Kanwisher, 2001) and responds to haptic exploration of objects in sighted and congenitally blind individuals (Naumer et al, 2010; Amedi, Jacobson, Hendler, Malach, & Zohary, 2002; James et al, 2002; Amedi, Malach, Hendler, Peled, & Zohary, 2001). Furthermore, neural shape similarity matrices from blind participants are correlated with neural shape similarity matrices from sighted individuals (Peelen, He, Han, Caramazza, & Bi, 2014), suggesting that LOC is biased to represent object shape even if the principal modality of input is not vision.…”

“…Recently, Peelen and colleagues (2014) calculated neural similarity matrices for a set of objects presented visually and verbally to blind and sighted individuals. By measuring the correlations between these neural similarity matrices, Peelen and colleagues (2014) argued that LOC carries a cross-modal shape representation. With respect to our current goals, there are two limitations associated with this study.…”

“…With respect to our current goals, there are two limitations associated with this study. First, Peelen and colleagues (2014) did not measure neural activity in response to haptic stimuli. Second, the correlation between two neural similarity matrices is a measure of second-order relations between two representations.…”

Structural brain aberrations associated with the dissociative subtype of post‐traumatic stress disorder

“…The inferior temporal gyrus is part of the ventral visual stream and subserves shape perception and recognition memory for patterns, faces and objects (43,44). In a previous study, participants reporting greater depersonalization/derealization showed reduced theta activity in the temporal lobe (45).…”