Dissociations in the Processing of “What” and “Where” Information in Working Memory: An Event-Related Potential Analysis

Abstract

Based on recent research that suggests that the processing of spatial and object information in the primate brain involves functionally and anatomically different systems, we examined whether the encoding and retention of object and spatial information in working memory are associated with different ERP components. In a study-test procedure subjects were asked to either remember simple geometric objects presented in a 4 by 4 spatial matrix irrespective of their position (object memory task) or to remember spatial positions of the objects irrespective of their forms (spatial memory task). The EEG was recorded from 13 electrodes during the study phase and the test phase. Recognition performance (reaction time and accuracy) was not different for the two memory tasks. PCA analyses suggest that the same four ERP components are evoked in the study phase by both tasks, which could be identified as N100, P200, P300, and slow wave. ERPs started to differ as a function of memory task 225 msec after stimulus onset at the posterior recording sites: An occipital maximal P200 component, lateralized to the right posterior temporal recording site, was observed for the object memory but not for the spatial memory task. Between-tasks differences were also obtained for P300 scalp distribution. Moreover, ERPs evoked by objects that were remembered later were more positive than ERPs to objects that were not remembered, starting at 400 msec postsimulus. The PCA analysis suggest that P300 and a slow wave following P300 at the frontal recordings contribute to these differences. A similar differential effect was not found between positions remembered or not remembered later. Post hoc analyses revealed that the absence of such effects in the spatial memory task could be due to less elaborated mnemonic strategies used in the spatial task compared to the object memory task. In the face of two additional behavioral experiments showing that subjects exclusively encode object features in the object memory task and spatial stimulus features in the spatial memory task, the present data provide evidence that encoding and rehearsal of object and spatial information in working memory are subserved by functionally and anatomically different subsystems.

Differences in EEG power in young and mature healthy adults during an incidental/spatial learning task are related to age and execution efficiency

“…Additionally, because a spatial dimension is essential for episodic memory, some studies have shown changes in the power and coherence of the EEG theta band during visuospatial learning in the central and posterior frontal regions. In fact, higher EEG theta power and coherence, predominantly in the 7.0-7.5-Hz frequency range, have been observed under intentional object position associations (Sato and Yamaguchi 2007) as well as under higher evoked potentials during object context associations (Mecklinger and Muller 1996). Nevertheless, EEG correlates of incidental visuospatial learning have rarely been studied.…”

Working memory as an emergent property of the mind and brain

“…Results from monkey electrophysiology (Wilson, O'Scalaidhe, & Goldman-Rakic, 1993), experimental psychology (Della Sala, Gray, Baddeley, Allamano, & Wilson, 1999;Hecker & Mapperson, 1997;Smith et al, 1995;Tresch, Sinnamon, & Seamon, 1993), neuroimaging (e.g., Smith et al, 1995), human electrophysiology (Mecklinger & Muller, 1996), and human neuropsychology (Owen, Iddon, Hodges, Summers, & Robbins, 1997;Postle, Jonides, Smith, Corkin, & Growdon, 1997) confirmed the validity of this idea. The multiple component model was adjusted accordingly, with the visuospatial sketchpad divided into "visual cache" and "inner scribe" components for representing object and spatiotemporal information, respectively (Baddeley & Logie, 1999;Logie, 1995).…”

Development of cognitive control and executive functions from 4 to 13 years: Evidence from manipulations of memory, inhibition, and task switching

“…Since spatial location was relevant to the correct response they were not pure Simon tasks, but hybrid spatial incompatibility tasks. There is evidence that the neural bases for working memory of object-appearance and spatial-location information are somewhat different (Haxby, Petit, Ungerleider, & Courtney, 2000;Levy & Goldman-Rakic, 2000;Mecklinger & Mueller, 1996) and spatial location is exactly the stimulus property that feeds the spatial-compatibility bias. In standard Simon tasks, subjects would perform better if they could (theoretically) screen out the location of the stimulus, but on our Dots and Arrows tasks information about the location of the stimulus is critical for determining the correct response.…”