Moreover, requiring subjects to perform a spatial interference task that disrupts or otherwise occupies this rehearsal component significantly impairs the performance of tests of spatial working memory, but has no effect on nonspatial visual memory tasks ( Cocchini et al., 2002). Baddeley (1986) initially proposed that in the context of spatial memory, covert eye movements can act as a way of revisiting locations in memory and thus operate very much like the articulatory rehearsal process known to be important for the maintenance of verbal information. Although the symmetry between sensory and motor representations of visuospatial information is less obvious than it is in the case of speech, it has been demonstrated that saccadic rehearsal is important for the maintenance of spatial information ( Postle et al., 2005). As with the phonological loop, where articulatory suppression interferes with the maintenance of verbal information, a concurrent processing demand in the visuospatial domain, such as tracking a spot of light moving on a screen, random eye movements, or the presentation of irrelevant visual information during learning, likewise impairs memory performance. Again, as is suggested by the term ‘sketchpad,’ the maintenance of visuospatial imagery in an active state requires top-down, or strategic, processing. The other slave system in the Working Memory model is the visuospatial sketchpad, which is critical for the online retention of object and spatial information. D’Esposito, in Learning and Memory: A Comprehensive Reference, 2008 3.13.2.5 The Visuospatial Sketchpad However, in this chapter we will focus on learning and retrieving everyday memories.ī.R. Other types of learning use other parts of the brain (see Section 8.0). Learning is not limited to the neocortex. Because this is the central theme of this chapter, we begin with a cartoon version in Figure 9.4. That experience – of imagining yesterday's coffee cup – makes use of visual cortex again. We thereby reconstruct some part of the original memory, again using the MTL to integrate memory traces into a coherent conscious experience. When we encounter a reminder of a specific past experience of the coffee cup, the bound memory traces ‘light up’ the corresponding regions of cortex again. Memory is for use in the real world, and retrieval is therefore as important as learning. Notice that visual cortex is involved in perception, learning, and episodic recall. Visual cortex is therefore needed to reconstruct the sight of the coffee cup, which is never identical to the original cup, but rather a plausible recreation of a pattern of visual activation that overlaps with the first one. When the episodic memory – the sight of the coffee cup – is cued the following day, maybe by someone asking, ‘Did you like the way I made the coffee yesterday?’, MTL is once again involved in retrieving and organizing widespread cortical memory traces. Visual features of the cup, like the handle, are also part of the associative complex that becomes activated.
These include semantic associates of the coffee cup, such as the coffee beans in the picture below. In the middle panel, storage is achieved when MTL coordinates widespread memory traces (involving synaptic modification) throughout many parts of cortex. In the left panel, the sight of a coffee cup standing on a table activates visual cortex up to the level of object perception (see Chapter 6). How MTL is believed to help store and retrieve episodic memories.
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