Abstract
The role of the intraparietal sulcus (IPS) in working memory (WM) remains a topic of considerable debate and divergent findings within the literature have made this an even more complex problem. Functional magnetic resonance imaging (fMRI) studies using foveally presented object arrays report bilateral IPS activity corresponding to the number of items held within working memory. Conversely, the electroencephalography (EEG) literature, measuring the slow wave component of the EEG signal often referred to as the contralateral delay activity, report greater activity for stimuli presented contralaterally compared to those presented ipsilaterally. Recent work has tried to rectify these findings by applying more stringent constraints on the hemifield of stimulus presentation. For example, presenting stimuli in both hemifields allows for the differentiation of WM-related activity from that of perceptual activity. Here, we attempt to resolve this discrepancy using a similar approach. Using fMRI and a region-of-interest analysis, we manipulated stimulus type (verbal, visuospatial) and cued hemifield in order to understand the contributions of each region of the IPS to WM. Our data show a significant contralateral bias across all IPS ROIs regardless of stimulus type. There is also a weaker stimulus driven bias in the left hemisphere for verbal stimuli and in the right hemisphere for visuospatial stimuli regardless of hemifield. Overall, these results are consistent with the EEG literature, and a contralateral bias in IPS regions. The results also support theoretical perspectives linking the IPS with a material general role in maintaining information in WM.
Meeting abstract presented at VSS 2016