Stimulus Dependency of Object-Evoked Responses in Human Visual Cortex: An Inverse Problem for Category Specificity

Abstract

Many studies have linked the processing of different object categories to specific event-related potentials (ERPs) such as the face-specific N170. Despite reports showing that object-related ERPs are influenced by visual stimulus features, there is consensus that these components primarily reflect categorical aspects of the stimuli. Here, we re-investigated this idea by systematically measuring the effects of visual feature manipulations on ERP responses elicited by both structure-from-motion (SFM)-defined and luminance-defined object stimuli. SFM objects elicited a novel component at 200–250 ms (N250) over parietal and posterior temporal sites. We found, however, that the N250 amplitude was unaffected by restructuring SFM stimuli into meaningless objects based on identical visual cues. This suggests that this N250 peak was not uniquely linked to categorical aspects of the objects, but is strongly determined by visual stimulus features. We provide strong support for this hypothesis by parametrically manipulating the depth range of both SFM- and luminance-defined object stimuli and showing that the N250 evoked by SFM stimuli as well as the well-known N170 to static faces were sensitive to this manipulation. Importantly, this effect could not be attributed to compromised object categorization in low depth stimuli, confirming a strong impact of visual stimulus features on object-related ERP signals. As ERP components linked with visual categorical object perception are likely determined by multiple stimulus features, this creates an interesting inverse problem when deriving specific perceptual processes from variations in ERP components.

Modulation of the N170 with Classical Conditioning: The Use of Emotional Imagery and Acoustic Startle in Healthy and Depressed Participants

“…Faces are stimuli that are processed in a unique way by the human brain, due to the adaptive importance of rapidly recognizing other humans, and potentially avoiding them in the case of threat. The N170 is an event-related potential (ERP) component that has been found to be strongly associated with facial processing, forming a negative potential at 140–200 ms post-stimulus that is greatest over occipito-temporal sites in the right hemisphere ( Posamentier and Abdi, 2003 ; Graewe et al, 2012 ). The N170 in response to faces has been found to originate from bilateral sources in the posterior superior temporal sulcus, and is thought to be related to supplementary activity specific to facial processing ( Itier and Taylor, 2004 ).…”

Oscillations or Synchrony? Disruption of Neural Synchrony despite Enhanced Gamma Oscillations in a Model of Disrupted Perceptual Coherence

“…This enables the formation of 3-D shape percepts (3-D face). Importantly, shape extraction can only be achieved when dots are moving, because otherwise the shape remains invisible ( Figure 1C; Bernardino et al, 2013;Graewe et al, 2012). In the random dot condition, a set of white dots was randomly moving on a black background ( Figure 1D).…”

“…The epochs for each stimulus type were averaged together, and ERPs were computed. We defined four different clusters of electrodes for further analysis Graewe et al, 2012), namely occipital, temporal, parieto-occipital, and parietal. The occipital cluster included the O1, OZ, and O2 electrodes, the temporal cluster was constituted by the TP7, CP5, P7, P5, PO7, TP8, CP6, P6, P8, and PO8 electrodes, the posterioroccipital cluster comprised the PO5, PO3, POZ, PO4, and PO6 electrodes, and, finally, the parietal cluster included the CP3, CP1, P3, P1, CP2, CP4, P2, and P4 electrodes.…”

“…Previous studies demonstrated impairments in 3-D structure-from-motion (SFM) perception in WS (Bernardino, Castelhano, Farivar, Silva, & Castelo-Branco, 2013;Mendes et al, 2005) or in response to static faces both in autism and WS (Grice et al, 2001), which inspired the combination of all these paradigms in the current study. Perception of SFM stimuli requires dorsal-ventral stream integration of local features into a coherent whole to achieve holistic perception (Graewe, De Weerd, Farivar, & Castelo-Branco, 2012). This paradigm may therefore help elucidate why gamma oscillatory patterns (variation of oscillatory activity over time) are differentially distributed for different subbands in a task-and/or disease-dependent manner (Castelhano, Duarte, Wibral, Rodriguez, & Castelo-Branco, in press;Bernardino et al, 2013) and provide further insights into the hypothesis that synchronization predicts perception (Hipp, Engel, & Siegel, 2011).…”

Functional Reorganization of the Visual Dorsal Stream as Probed by 3-D Visual Coherence in Williams Syndrome

“…An experimental task using videos of SFM-defined faces and chairs with the duration of 980 msec (for further details, see Bernardino et al, 2013;Graewe, De Weerd, Farivar, & Castelo-Branco, 2012;Farivar, Blanke, & Chaudhuri, 2009) was conducted to localize the regions that responded to SFM stimulus in both groups Figure 1A. Face stimuli consisted of 3-D laser-scanned heads from the Max-Planck Face Database, and chair stimuli were selected from a chair model database.…”