The Contribution of Object Shape and Surface Properties to Object Ensemble Representation in Anterior-medial Ventral Visual Cortex

Abstract

Abstract■ Our visual system can extract summary statistics from large collections of objects without forming detailed representations of the individual objects in the ensemble. In a region in ventral visual cortex encompassing the collateral sulcus and the parahippocampal gyrus and overlapping extensively with the sceneselective parahippocampal place area (PPA), we have previously reported fMRI adaptation to object ensembles when ensemble statistics repeated, even when local image features differed across images (e.g., two different images of the same strawberry pile). We additionally showed that this ensemble representation is similar to (but still distinct from) how visual texture patterns are processed in this region and is not explained by appealing to differences in the color of the elements that make up the ensemble. To further explore the nature of ensemble representation in this brain region, here we used PPA as our ROI and investigated in detail how the shape and surface properties (i.e., both texture and color) of the individual objects constituting an ensemble affect the ensemble representation in anterior-medial ventral visual cortex. We photographed object ensembles of stone beads that varied in shape and surface properties. A given ensemble always contained beads of the same shape and surface properties (e.g., an ensemble of star-shaped rose quartz beads). A change to the shape and/or surface properties of all the beads in an ensemble resulted in a significant release from adaptation in PPA compared with conditions in which no ensemble feature changed. In contrast, in the object-sensitive lateral occipital area (LO), we only observed a significant release from adaptation when the shape of the ensemble elements varied, and found no significant results in additional scene-sensitive regions, namely, the retrosplenial complex and occipital place area. Together, these results demonstrate that the shape and surface properties of the individual objects comprising an ensemble both contribute significantly to object ensemble representation in anterior-medial ventral visual cortex and further demonstrate a functional dissociation between object-(LO) and scene-selective (PPA) visual cortical regions and within the broader scene-processing network itself. ■

Perceiving ensemble statistics of novel image sets

“…The neural correlates underlying these processes remain vague. Though the Para-hippocampal Place Area (PPA) was associated with such processes, as found by Cant and Xu (2012, 2017, there is no differentiation of low-and high-level ensemble processing. Moreover, the mechanism of this unique processing is yet to be well understood, and a main question to be investigated in future research ishow and where are different ensembles processed?…”

Differential hemispheric and visual stream contributions to ensemble coding of crowd emotion

“…Much behavioral evidence has been accumulated supporting this notion 6,7,11–15,21,99–103, but see 104 , although only a few recent fMRI studies have compared the neural representations of ensemble coding and individual processing 105–107 . Cant and Xu 105,106 showed that PPA and LO were preferentially engaged in texture perception and object processing, respectively; and Huis in’t Veld and de Gelder 107 showed the greater anticipatory and action preparation activity in the areas including IPL, SPL, SFG, and premotor cortex for interactive body movement of a group of panicked people, compared to an unrelated movement of individuals. However, unlike prior work that used stimuli of simple texture patches and objects 105,106 or that removed the information about facial expression of people from their blurred video clips 107 , the current study examined the distinct neutral substrates underlying the processing of facial crowds with varying emotional expressions compared to the processing of individual emotion expressions, providing evidence for distinct mechanisms supporting them.…”

Ensemble coding of crowd emotion: Differential hemispheric and visual stream contributions

“…Different patterns of hemispheric lateralization for the crowd emotion vs. individual emotion processing suggest that they may rely on qualitatively distinct systems. Much behavioral evidence has been accumulated supporting this notion (e.g., Alvarez & Oliva, 2008;Ariely, 2001;Cant, Sun, & Xu, 2015;Chong et al, 2008;Chong & Evans, 2011;Chong & Treisman, 2005;Choo & Franconeri, 2010;Corbett & Oriet, 2011;Haberman, Brady, & Alvarez, 2015;Haberman & Whitney, 2010;Im & Halberda, 2013;Leib et al, 2012;Parkes et al, 2001, but see Myczek & Simons, 2008, although only a few recent fMRI studies have compared the neural representations of ensemble coding and individual processing (e.g., , 2017Huis in't Veld & de Gelder, 2015). Xu (2015, 2017) showed that PPA and LO were preferentially engaged in texture perception and object processing, respectively; and Huis in't Veld and de Gelder (2015) showed the greater anticipatory and action preparation activity in the areas including IPL, SPL, SFG, and premotor cortex for interactive body movement of a group of panicked people, compared to an unrelated movement of individuals.…”

“…Xu (2015, 2017) showed that PPA and LO were preferentially engaged in texture perception and object processing, respectively; and Huis in't Veld and de Gelder (2015) showed the greater anticipatory and action preparation activity in the areas including IPL, SPL, SFG, and premotor cortex for interactive body movement of a group of panicked people, compared to an unrelated movement of individuals. Because Cant and Xu (2015;2017) used the stimuli of simple texture patches and objects and Huis in't Veld and de Gelder (2015) removed the information about facial expression of people from their blurred video clips, the current study is the first to examine the distinct neutral substrates underlying the processing of facial crowds with varying emotional expressions and the processing individual faces and to show the evidence for distinct mechanisms supporting them.…”