Neural Mechanisms of Natural Visual Perception

National Institute Of Mental Health

Investigators

Linked publications, trials & patents

Abstract

Much of our vision research over the past several years investigates the brain mechanisms underlying how we see individuals, and particularly their faces. Historically, the investigation of vision has derived from experiments in which stimuli are presented alone on a screen. This isolate presentation of simplified stimuli allows for the evaluation of how brain areas are specialized for certain types of visual patterns. This approach has led to a standard view of the visual brain that is hierarchical and modular. In this framework, a specific visual percept is assumed to emerge from the selective activation of some brain areas over others. An important question, however, is whether this framework extends to more natural modes of vision, where the visual environment is complex, immersive, and temporally continuous. At present, we are pursuing experiments inside the immersive dome environment, where it is possible to examine aspects of visual brain activity that are hidden when animals view stimuli on a small screen. In a recent review article, we summarized the results from a growing number of studies that recorded neural activity across the cortex during natural visual behaviors. We concluded that the visual brain, under natural modes of behavior, operates very differently than during the conventional presentation of isolated stimuli (Leopold, 2024). Namely, whereas traditional accounts of the visual brain have neurons or groups of neurons in specified areas representing stimuli in different categories, these experiments suggest that information is broadly distribute across multiple areas, with individual neurons having many roles. In another review article (Leopold and Bourne, 2025), we investigate how the development of the visual cortex depends critically on the thalamus, drawing upon a range of interactive and supportive mechanisms from mid-fetal stages to adulthood. The incorporation of neurodevelopment into the study the cerebral cortex and its many specializations for vision may change the way we view neural systems and networks. While genetic mechanisms can establish the course functional subdivisions of the visual brain, it is only through extensive activity and repeated experience that areas gain their adult level functional expertise. This perspective is central in the newly founded Systems Neurodevelopment Laboratory. One recent study builds on our multiple previous studies, in this case using conventional presentation paradigms, asking how face-selective neurons support recognition. Our previous studies emphasized the embedding of average norms within the visual cortex. These norms allow for the brain to efficiently extract facial features that are distinguishing, inasmuch as they deviate from the average in a particular individual. In a recently published study, we tested whether objects that resemble faces, sometimes called pareidolia objects, would stimulate cells known to be face selective (Koyano et al, 2025). Much to our surprise, we found that the cells did not respond to these objects, despite the compelling perception of faces they elicited. Finally, in a collaborative study, we examined the restorative potential of retinal gene therapy on the visual responses within central brain pathways (Ashtari et al, Brain 2024). In that study, we found that patients suffering from a degenerative retinal disease (Leber’s Congenital Amaurosis) had an inherent imbalance relative processing strength in two central pathways. Namely, fMRI responses indicated that the geniculostriate pathway was weakened while the retinotectal pathway was strengthened compared to human controls. Following restorative gene therapy, we found that the geniculostriate pathway was partially restored whereas the initial strengthening of the retinotectal pathway was unchanged. These findings may spur the development of new tools and rehabilitation strategies to help maximize the use of residual visual abilities and augment experience-dependent plasticity.