Patients with right parietal lesions, but without symptoms of neglect, were tested in a spatial probe task, in an object probe task, and in a conjunction task, namely a task that requires to judge whether a particular probe stimulus had been located in that particular position ( Berryhill and Olson, 2008). (2006) found that damage to the right PPC impairs both object and spatial memory, suggesting an attentional, rather than a mnemonic, role of this region.
This result suggests that there is a dissociation between spatial and object STM and that right parietal damage impairs spatial STM but not object performance. Memory for color and shape does not seem to be affected, suggesting that a parietal lesion specifically affects the maintenance of spatial representations ( Pisella et al., 2004). These memory deficits were not found in right-brain-damaged patients with left neglect and a nonparietal lesion, and concerned coding spatial location independently from the horizontal position ( Pisella et al., 2004). Neglect patients show a poor performance in vertical versions of the Corsi block span, but also when a single location is probed requiring a verbal response (yes/no), and poor performance in this last task correlates with severity of neglect in cancellation tasks moreover, the lesion associated with the worst memory performance appears to be primarily localized to the white matter underlying the supramarginal gyrus ( Malhotra et al., 2005). Indeed, in patients with left spatial neglect right PPC damage is associated with failures to remember previously searched locations in cancellation tasks, and previously encountered targets are treated as new ones ( Malhotra et al., 2004, 2005 Mannan et al., 2005). More specifically, it has been suggested that deficits in spatial STM may contribute to neglect symptoms. Patients with right parietal damage had a significantly worse performance not only as compared with patients with left parietal damage, but also with the rest of the right-hemisphere group, pointing to a role of the right parietal cortex as opposed to the temporal cortex, which had been suggested as the critical site in previous studies ( Kimura, 1963).ĭeficits in visuospatial STM, measured by means of the Corsi block span, have been found after lesions involving the right parietal lobe ( De Renzi and Nichelli, 1975), and several studies have shown that these deficits are associated with left unilateral spatial neglect ( De Renzi et al., 1977 Husain et al., 2001). A seminal study performed in 1967 by Warrington and James tested visual retention using nonrepresentational material, namely a visual pattern made up of five block squares variously positioned on a four-by-four white ground. Studies on brain-damaged patients have demonstrated the role of the lateral prefrontal cortex and the PPC in spatial STM.
In analogy with the phonologic loop, the activity of visuospatial STM (also termed visuospatial sketchpad) relies on different subregions controlling specific processes, such as the temporal storage of spatial information and the retention of visual features. Costanza Papagno, in Handbook of Clinical Neurology, 2018 Visuospatial STM
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