Biology subjects

Bankson, B. B.

Publications and source records attributed to Bankson, B. B..

4 recordsLinked to original sources

bioRxiv2020

Dynamic Domain Specificity In Human Ventral Temporal Cortex

An enduring neuroscientific debate concerns the extent to which neural representation is restricted to neural populations specialized for particular domains of perceptual input, or distributed outside of highly selective populations as well. A critical level for this debate is the neural representation of the identity of individual images, such as individual-level face or written word recognition. Here, intracranial recordings throughout ventral temporal cortex across 17 human subjects were used to assess the spatiotemporal dynamics of individual word and face processing within and outside regions strongly selective for these categories of visual information. Individual faces and words were first discriminable primarily only in strongly selective areas, beginning at about 150 milliseconds after word or face onset, and then discriminable both within and outside strongly selective areas approximately 170 milliseconds later. Regions of ventral temporal cortex that were and were not strongly selective both contributed non-redundant information to the discrimination of individual images. These results can reconcile previous results endorsing disparate poles of the domain specificity debate by highlighting the temporally segregated contributions of different functionally defined cortical areas to individual level representations. This work supports a dynamic model of neural representation characterized by successive domain-specific and distributed processing stages.

neuroscience↗

bioRxiv2019

Whole-brain MEG decoding of symbolic and non-symbolic number stimuli reveals primarily format-dependent representations

The human brain can rapidly form representations of numerical magnitude, whether presented with symbolic stimuli like digits and words or non-symbolic stimuli like dot displays. Little is known about the relative time course of these symbolic and non-symbolic number representations. We investigated the emergence of number representations for three stimulus formats - digits, words, and dot arrays - by applying multivariate pattern analysis to MEG recordings from 22 participants. We first conducted within-format classification to identify the time course by which individual numbers can be decoded from the MEG signal. Peak classification accuracy for individual numbers in all three formats occurred around 110 ms after stimulus onset. Next, we used between-format classification to determine the time course of shared number representations between stimulus formats. Classification accuracy between formats was much weaker than within format classification, but it was also significant at early time points, around 100 ms for both digit / dot and digit / word comparisons. We then used representational similarity analysis to determine if we could explain variance in the MEG representational geometry using two models: a GIST feature model capturing low-level visual properties and an approximate number model capturing the numerical magnitude of the stimuli. Model RSA results differed between stimulus formats: while the GIST model explained unique variance from 100-300 ms for all number formats, the performance of the approximate number model differed between formats. Together, these results are consistent with the view that distinct, format-specific number representations, moreso than a single \"abstract\" number representation, form the basis of numerical comparison.

neuroscience↗

bioRxiv2017

The temporal evolution of conceptual object representations revealed through models of behavior, semantics and deep neural networks

Visual object representations are commonly thought to emerge rapidly, yet it has remained unclear to what extent early brain responses reflect purely low-level visual features of these objects and how strongly those features contribute to later categorical or conceptual representations. Here, we aimed to estimate a lower temporal bound for the emergence of conceptual representations by defining two criteria that characterize such representations: 1) conceptual object representations should generalize across different exemplars of the same object, and 2) these representations should reflect high-level behavioral judgments. To test these criteria, we compared magnetoencephalography (MEG) recordings between two groups of participants (n = 16 per group) exposed to different exemplar images of the same object concepts. Further, we disentangled low-level from high-level MEG responses by estimating the unique and shared contribution of models of behavioral judgments, semantics, and different layers of deep neural networks of visual object processing. We find that 1) both generalization across exemplars as well as generalization of object-related signals across time increase after 150 ms, peaking around 230 ms; 2) behavioral judgments explain the most unique variance in the response after 150 ms. Collectively, these results suggest a lower bound for the emergence of conceptual object representations around 150 ms following stimulus onset.

neuroscience↗

bioRxiv2017

Representational dynamics of task context and its influence on visual object processing

Despite the importance of an observers goals in determining how a visual object is categorized, surprisingly little is known about how humans process the task context in which objects occur and how it may interact with the processing of objects. Using magnetoencephalography (MEG), functional magnetic resonance imaging (fMRI) and multivariate techniques, we studied the spatial and temporal dynamics of task and object processing. Our results reveal a sequence of separate but overlapping task-related processes spread across frontoparietal and occipitotemporal cortex. Task exhibited late effects on object processing by selectively enhancing task-relevant object features, with limited impact on the overall pattern of object representations. Combining MEG and fMRI data, we reveal a parallel rise in task-related signals throughout the cerebral cortex, with an increasing dominance of task over object representations from early to higher visual areas. Collectively, our results reveal the complex dynamics underlying task and object representations throughout human cortex.

neuroscience↗