Population receptive field properties of the human visual claustrum zone

The claustrum is a thin, bilateral sheet of grey matter between the insula and putamen that stands out by its high interconnectivity with almost the entire cortex. Despite continuing research in humans and animals, its functional role remains largely unknown. In the present study, we explored the topographic organization of the recently described human visual claustrum zone. We performed a population receptive field (pRF) analysis on the 7T retinotopy dataset of the Young Adult Human Connectome Project (N = 181, 109 female) comparing the visual claustrum with established visual field properties of the lateral geniculate nucleus, the primary visual cortex, and higher-level topographic maps of the dorsal and the ventral stream. Our results demonstrate for the first time that the human visual claustrum showed several topographic properties typical for visual areas, including a representational bias towards the contralateral visual field, and a pRF size increase with increasing eccentricity. At the same time, the claustrum also exhibited a positive eccentricity gradient along the posterior-anterior axis, an extended representation of the visual periphery compared to other areas and a lack of horizontal meridian bias. These latter two properties highlight the claustrums role as a higher-level nucleus which is less dependent on sensory input. This study is the first to characterize the topographic organization of the visual claustrum zone in humans, highlighting its uniqueness among the known visually responsive regions. Significance StatementThe claustrum is a thin subcortical brain region whose function is still largely unknown. Previous animal studies showing unimodal sensory zones within the nucleus suggest an involvement in sensory processing. The present study focuses on the visual claustrum zone and is the first to characterize its topographic organization in humans. We used population receptive field mapping for functional Magnetic Resonance Imaging on the 7T retinotopy dataset of the human connectome project. We could demonstrate similarities to other visually responsive areas and characteristics that distinguish the visual claustrum. Our study yields important information on the claustrums visuotopic organization that can guide further investigation of its role in visual processing and cognition.