Intracranial markers of conscious face perception in humans

Abstract

Investigations of the neural basis of consciousness have greatly benefited from protocols that involve the presentation of stimuli at perceptual threshold, enabling the assessment of the patterns of brain activity that correlate with conscious perception, independently of any changes in sensory input. However, the comparison between perceived and unperceived trials would be expected to reveal not only the core neural substrate of a particular conscious perception, but also aspects of brain activity that facilitate, hinder or tend to follow conscious perception. We take a step towards the resolution of these confounds by combining an analysis of neural responses observed during the presentation of faces partially masked by Continuous Flash Suppression, and those responses observed during the unmasked presentation of faces and other images in the same subjects. We employed multidimensional classifiers to decode physical properties of stimuli or perceptual states from spectrotemporal representations of electrocorticographic signals (1071 channels in 5 subjects). Neural activity in certain face responsive areas located in both the fusiform gyrus and in the lateral-temporal/inferior-parietal cortex discriminated seen vs. unseen faces in the masked paradigm and upright faces vs. other categories in the unmasked paradigm. However, only the former discriminated upright vs. inverted faces in the unmasked paradigm. Our results suggest a prominent role for the fusiform gyrus in the configural perception of faces, and possibly other objects that are holistically processed. More generally, we advocate comparative analysis of neural recordings obtained during different, but related, experimental protocols as a promising direction towards elucidating the functional specificities of the patterns of neural activation that accompany our conscious experiences.

Reduced Dynamic Complexity of BOLD Signals Differentiates Mild Cognitive Impairment From Normal Aging

“…The FG is located in the ventral portion of the temporal lobe and under the parahippocampal gyrus. Although the function of the FG is unclear, it has been associated with object recognition and face perception (Baroni et al, 2017;Weiner et al, 2018). Probably limited by small sample sizes and their methods of measuring entropy that considered only the ranks of the samples and not their metrics (Bandt and Pompe, 2002), previous studies failed to find meaningful alterations in the EMCI or LMCI group compared with the NC group.…”

Conscious Perception as Integrated Information Patterns in Human Electrocorticography

“…While such decoding analyses have their own advantages in the search for NCCs (as in the same data set presented in this paper; cf. Baroni et al, 2017), there is an important caveat in such an approach: the assumption of the decoder. Even if one can perfectly identify conscious perception based on patterns of neuronal activity, the interpretation of a vector of regression weights, for example, is entirely dependent on the presence of a decoder, usually a tool in the hands of the experimenter.…”

“…Completed trial counts for all included subjects are listed in Table 1. More detailed analyses of the tasks (CFS and unmasked tasks) are described elsewhere (Baroni et al, 2017). …”

Mathematics and the Brain: A Category Theoretical Approach to Go Beyond the Neural Correlates of Consciousness

“…Under such an anatomical assumption, a pattern of neural activity in a specific anatomical location over a certain temporal period is usually considered to be content-specific NCC. An example of a face-related NCC is the extended neural activation infusiform gyrus in the right hemisphere [ 44 , 45 , 46 , 47 ]. If the activity in this area is transiently lost due to electrical stimulation, face perception gets disrupted without affecting other types of percept [ 48 ].…”