The common role of the intraparietal sulcus in mental rotation and antisaccades
IPS activation of antisaccade > baseline (green), mental rotation zero rotation > difficult rotation (red), conjunction of [(antisaccade > baseline)+(zero rotation > difficult rotation)].
A. Papadopoulos, G. Egan, J. Fielding, S. Jamadar
As the functional properties of the Intraparietal sulcus (IPS) are considered similar across human and non-human primates, non-human primate models have been used extensively to understand the role of the IPS in cognitive processes such as attention and working memory. However, despite the great advances in knowledge about the IPS structure and function from non-human primate studies, there remains difficulty in completely mapping the human IPS subregions to match that of non-human primates, as the human parietal cortex is greatly expanded in comparison to non-human primates.
Although there are difficulties completely mapping the human IPS, it is clear that this region contributes to attentional control. A possible way to explore functional segregation of the human IPS is through neuroimaging studies administering tasks such as antisaccade* and mental rotation tasks, which emphasise the role of the IPS in spatial transformation. The aim of this study was to determine if the IPS plays a domain-general role in spatial transformations across tasks, using the antisaccade and mental rotation tasks. Fourteen healthy participants (M= 29.07, SD= 5.85) volunteered in this study. Participants completed the antisaccade and mental rotation tasks while undergoing fMRI scanning (T2*-weighted GRAPPA echo-planar imaging (EPI) sequence, ascending axial acquisition, TR = 2.5sec, TE = 30ms, FOV = 192mm, acquisition matrix = 64 x 64, 44 slices, 3 x 3 x 3 mm voxels). fMRI conjunction analysis of the tasks (antisaccade > baseline; mental rotation zero rotation > difficult rotation) showed overlapping activity within the medial and posterior medial IPS regions, consistent with the argument that these tasks utilise overlapping processes. Our results support the contention that the medial IPS plays a specific role in spatial transformations that is invoked across tasks regardless of cognitive domain.
* A voluntary eye movement made in the direction opposite to the side where a stimulus is presented. The subject is asked to fixate a small dot for some time. A stimulus is then presented to one side and the subject is asked to inhibit a reflex eye movement towards it but to make a saccade in the opposite direction. Analysis of the errors and/or latencies of the antisaccades indicate dysfunction in the frontal lobe, which controls the saccadic eye movements.