Biology subjects

Broday-Dvir, R.

Publications and source records attributed to Broday-Dvir, R..

4 recordsLinked to original sources

bioRxiv2024

The organization of high-level visual cortex is aligned with visual rather than abstract linguistic information

A fundamental question dominating the study of human visual cortex is whether it is organized along visual or semantic information. This question is unresolved, and the controversy has been rekindled by the recent report that surprisingly, revealed that the representations of textual description of images by linguistic artificial networks successfully predict the response of high-level visual cortex to visual images. These findings appear to support a linguistic, abstract, organizing principle of human visual cortex. Here, using iEEG recordings from high level visual cortex in patients, we contributed to this debate, by testing the hypothesis that this linguistic alignment is restricted to textual descriptions of the visual content of the images (visual text) and does not extend to abstract textual descriptions (abstract text). We selected images that depict familiar faces and places, as these images allow for the best dissociation between these two types of text and generated their visual and abstract (e.g., name and biography of a person) textual descriptions. We then predicted the relational structures of the iEEG response to the images using their textual representations based on a large language model and the image representation based on a convolutional neural network. Neural relational-structures in high-level visual cortex were similarly predicted by images and visual-text but not abstract-text representations. Abstract text best predicted responses of the fronto-parietal cortex to the images. These results demonstrate that visual-language alignment in high-level visual cortex is limited to visually grounded language.

neuroscience↗

bioRxiv2024

Text-related functionality of visual human pre-frontal activations revealed through neural network convergence

The functional role of visual activations of human pre-frontal cortex remains a deeply debated question. Its significance extends to fundamental issues of functional localization and global theories of consciousness. Here we addressed this question by comparing, dynamically, the potential parallels between the relational structure of prefrontal visual activations and visual and textual-trained deep neural networks (DNNs). The frontal visual relational structures were revealed in intra-cranial recordings of human patients, conducted for clinical purposes, while the patients viewed familiar images of faces and places. Our results reveal that visual relational structures in frontal cortex were, surprisingly, predicted by text and not visual DNNs. Importantly, the temporal dynamics of these correlations showed striking differences, with a rapid decline over time for the visual component, but persistent dynamics including a significant image offset response for the text component. The results point to a dynamic text-related function of visual prefrontal responses in the human brain.

neuroscience↗

bioRxiv2022

Perceptual stability reflected in neuronal pattern similarities in human visual cortex

The magnitude of neuronal activation is commonly considered a critical factor for conscious perception of visual content. However, this dogma contrasts with the phenomenon of rapid adaptation, in which the magnitude of neuronal activation drops dramatically in a rapid manner, while the visual stimulus and the conscious experience it elicits remain stable. Here we report that the profiles of multi-site activation patterns and their relational geometry -i.e. the similarity distances between activation patterns, as revealed using iEEG recordings, are sustained during extended stimulation despite the major magnitude decrease. These results are compatible with the hypothesis that conscious perceptual content is associated with the neuronal pattern profiles and their similarity distances, rather than by the overall activation magnitude, in human visual cortex.

neuroscience↗

bioRxiv2020

Resting state fluctuations underlie free and creative verbal behaviors in the human brain

Internally generated (free) ideas and creative thoughts constitute a fundamentally important aspect of the human experience, yet the neuronal mechanism driving these behaviors remains elusive. Here we examined the hypothesis that the common mechanism underlying free verbal behaviors is the ultra-slow activity fluctuations (termed "resting state fluctuations") that emerge spontaneously in the human brain. In our experiment, participants were asked to perform three voluntary verbal tasks: a verbal fluency task, a verbal creativity task (alternative uses of everyday objects) and a divergent thinking task (instances of common concepts), during fMRI scanning. BOLD-activity during these tasks was contrasted with a control-deterministic verbal task, in which the behavior was fully determined by external stimuli. Our results reveal that in all three voluntary tasks, the verbal-generation responses displayed a gradual anticipatory buildup that preceded the deterministic control-related responses by [~]2 seconds. Importantly, variance analysis ruled out a time-jittered step-function response confound. Critically, the waveforms of the anticipatory buildups, as reflected in their time-frequency dynamics, were significantly correlated to the dynamics of resting state fluctuations, measured during a rest period prior to the tasks. Specifically, the amplitude of low frequency fluctuations (fALFF) of the resting state time-course and the voluntary verbal responses in the left inferior frontal gyrus (LH IFG), a central hub engaged in these tasks, were correlated across individual participants. This correlation was not a general BOLD-related or verbal-response related result, as it was not found during the externally-determined verbal control condition. Furthermore, it was specific to brain regions known to be involved in language production. These results indicate that the slow buildup preceding voluntary behaviors is linked to resting state fluctuations. Thus, these ubiquitous brain fluctuations may constitute a common neural mechanism underlying the generation of free and creative behaviors in the human brain.

neuroscience↗