Frontal subcortical executive dysfunction and minor hallucinations in Parkinson's disease are linked to sensitivity to somatomotor conflicts.

The human brain’s ability to process and integrate visual information is fundamental to environmental adaptation. In particular, encoding novel visual stimuli upon their initial presentation is critical. Visual information processing is characterized by its speed, precision, and hierarchical distribution. According to the classical visual dual-stream model, visual information reaches the visual cortex via the retina and is then transmitted through two distinct yet interconnected pathways: the dorsal and ventral streams. A large body of research using neuropsychological and neuroimaging methods suggests that, though anatomically distinct, these two pathways work in close coordination. The dorsal “where” pathway, extending from the visual association cortex to the parietal cortex, plays a primary role in spatial awareness and action guidance. In contrast, the ventral “what” stream transmits visual input from primary and association cortices to the inferior and anterior temporal cortex, supporting hierarchical processing and facilitating object recognition by integrating attributes such as color and shape. Modern neuroimaging techniques, particularly those based on blood-oxygenation-level-dependent (BOLD) signals, have provided insight into large-scale visual network function. Interestingly, research using resting-state functional magnetic resonance (rs-fMRI) has revealed that limbic structures are extensively connected to both visual and non-visual cortical regions. However, the limited temporal resolution hinders the ability to observe the millisecond-scale interactions occurring between individual brain regions during visual processing. Recent studies using intracranial electroencephalography (iEEG) have provided novel insights into the rapid, hierarchical processing of visual stimuli in the human brain. Current iEEG research has clearly identified category-specific (e.g., faces, objects, and words) activation patterns in multiple brain regions. For example, the ventral temporal cortex exhibited lateral–medial response biases to visual stimuli, with face-selective activity concentrated in the fusiform gyrus (FG) and place-selective activity localized in the medial parahippocampal gyrus (PHC); among these, the FG displayed a posterior to anterior gradient in face-selectivity activity, consistent with the hierarchical structure of the ventral visual stream. The medial parietal cortex showed category-selective interactions with the medial temporal lobe, exhibiting bilateral preferential responses to places and a right-lateralized response to faces in the subparietal sulcus. It is noteworthy that visual processing was not only observed in the dorsal and ventral visual streams but also widely in higher-order cortical areas (e.g., temporal lobe, frontal cortices) and subcortical regions (e.g., the hippocampus) within the first few hundred milliseconds of stimulus presentation, indicating a distributed brain network involved in visual perception rather than being confined to traditional visual stream regions. However, these iEEG studies provided only limited simultaneous coverage of brain regions; consequently, the propagation patterns and directional functional connectivity among visual regions, higher-order cortices, and limbic structures at the whole-brain scale remains unclear, leaving gaps in our understanding of how perception and higher-level cognition, such as memory systems, interact during novel visual processing.