Abstract
The capacity of visual short-term memory (VSTM) is highly limited, but it does vary substantially across individuals, ranging from 1.5 to 5 objects (Vogel et al., 2001). Individual differences in VSTM capacity seem to be imposed by processing bottlenecks in the intraparietal sulcus (IPS) and lateral occipital complex (LOC) as BOLD activity in these areas mirrors behavioral estimates of VSTM capacity (Todd & Marois, 2004; Xu & Chun, 2006). Moreover, it seems that the filtering efficiency of the IPS is controlled on a trial-to-trial basis by the prefrontal cortex and the basal ganglia (McNab & Klingberg, 2007). Here, we report a study employing voxel-based morphometry (VBM) that focuses on the relation between VSTM capacity and grey matter volume in the IPS, the LOC and the basal ganglia. We acquired anatomical scans of 53 healthy subjects, who additionally performed a standard VSTM task (see Luck and Vogel, 1997; only oriented rectangles were used). We found that people with high VSTM capacity had increased grey matter volume in the IPS (bilateral), the LOC (bilateral) and the basal ganglia (bilateral, but more prominently in the right hemisphere) in addition to a few more brain areas. Noteworthy is that people with high VSTM capacity also had increased grey matter volume in the right superior frontal gyrus. Altogether, it seems that individual differences in VSTM capacity are driven by anatomical differences in the LOC, the IPS, the basal ganglia and the prefrontal cortex that in turn give rise to the functional differences that were evident in previous studies (Todd & Marois, 2004; Xu & Chun, 2006; McNab & Klingberg, 2007).