Mapping memory-guided saccade population receptive fields reveals principles of cortical organization along the human intraparietal sulcus

Abstract

The intraparietal sulcus is a central hub for motor planning and sensorimotor integration. Its responses are known to support coordinate transformations across reference frames and modalities--for example, eye-position gain fields that convert retinotopic, fovea-centred signals into head-centred representations. In the oculomotor domain, the human intraparietal sulcus is sensitive to eye-movement planning and has been extensively studied using memory-guided saccade paradigms. These classic approaches have revealed topographic organization and contralateral sensitivity for preferred direction in saccade planning and execution. However, such designs provide detailed information about preferred direction; they do not probe tuning width: how narrowly or broadly a given cortical location responds around its preferred direction. At present, it remains unclear whether and how tuning width is organized along the human intraparietal sulcus. Critically, neurophysiological studies in non-human primates do not offer systematic and extensive measurements of tuning width. Moreover, the relationship between tuning width and preferred direction at the population level in human intraparietal cortex is unknown. Here, we address these questions using a forward-modelling approach combined with high-field (7-Tesla) functional MRI. We observe contralateral preference for preferred direction in saccade planning and execution, as well as a novel large-scale organization of preferred saccade tuning width, in vivo, in humans. Highlightssaccade planning and execution tuning width is arranged topographically along human early visual cortex and human intraparietal sulcus; specificity of voxel-level saccade planning and execution decreases along the visual hierarchy; specificity of population-level saccade planning and execution increases along the visual hierarchy; forward modelling applied to memory-guided saccade paradigm outperforms the standard phase-encoding approach;