![]() The V1-substrate propositions are based mainly on the fact that, although most areas in occipital cortex are topographically organized, area V1 has the unique status of being the largest topographic map in the brain, with the highest spatial resolution, in addition to parallel processing of the information from the whole map surface (in contrast to the sequential processing in some other modalities).Īll of these features are critically important for a successful “sketchpad” implementation, which is why previous theoretical as well as neurophysiological studies in non-human primates (e.g., Mumford, 1991, 1996 Lee et al., 1998 Super et al., 2001a, b Lee and Mumford, 2003 Super, 2003) had suggested V1 as the source of the high-resolution visuo-spatial “sketchpad” function: “instead of being the first stage in a feedforward pipeline, V1 is better described as the unique high-resolution buffer in the visual system” ( Lee and Mumford, 2003). Interestingly, the involvement of the early visual cortex, and area V1 in particular, has been a critical issue in discussions both on the neural substrate of the putative visuo-spatial sketchpad and on the nature of imagery. An enhanced version of the multicomponent WM model added an episodic buffer ( Baddeley, 2003). While the visuo-spatial sketchpad is considered to be responsible for the temporarily storage and manipulation of visuo-spatial material, the phonological loop is posited to provide a similar function for verbal material. Initially, the proposed structure included the central executive component and two active storage buffers – the visuo-spatial sketchpad and the articulatory/phonological loop. WM refers to the temporary storage and manipulation of information, and is invoked as the mechanism for information processing during the performance of a wide range of everyday tasks (e.g., Baddeley and Hitch, 1974 Baddeley, 1986, 1992, 2000, 2003 Logie et al., 1989 Logie and Marchetti 1991 Logie 1995 Baddeley and Andrade, 2000). Although each of these major cognitive constructs is defined and treated in various ways across studies, most accept that both imagery and WM involve a type of internal representation available to our awareness in WM, however, there is a further emphasis on goal-oriented, active maintenance and use of this conscious representation to guide voluntary action. Mapping the distinctions and interrelationships between imagery and working memory (WM) remains challenging. The implications of these findings for the debate on the interrelationships between the core cognitive constructs of WM and imagery and the nature of internal representations are evaluated. The sole visual hierarchy activation was isolated to the primary visual area (V1), and accompanied by deactivation of the entire extrastriate cortex, thus ’cutting-off’ any signal propagation from/to V1 through the visual hierarchy. Remarkably, the pattern of cross-modal occipital activation generated by the non-visual memory drawing was essentially the inverse of this typical imagery signature. ![]() If this WM task had been mediated by transfer of the felt spatial configuration to the visual imagery mechanism, the response-profile in visual cortex would be predicted to have the “top-down” signature of propagation of the imagery signal downward through the visual hierarchy. Blindfolded participants were trained through our Cognitive-Kinesthetic Method ( Likova, 2010a, 2012) to draw complex objects guided purely by the memory of felt tactile images. If there is a visuo-spatial “sketchpad” for WM, does imagery involve the same representational buffer? Alternatively, does WM employ an imagery-specific representational mechanism to occupy our awareness? Or do both constructs utilize a more generic “projection screen” of an amodal nature? To address these issues, in a cross-modal fMRI study, I introduce a novel Drawing-Based Memory Paradigm, and conceptualize drawing as a complex behavior that is readily adaptable from the visual to non-visual modalities (such as the tactile modality), which opens intriguing possibilities for investigating cross-modal learning and plasticity. Multicomponent WM models incorporate representational buffers, such as the visuo-spatial sketchpad, plus central executive functions. In WM, there is a further emphasis on goal-oriented, active maintenance, and use of this conscious representation to guide voluntary action. ![]() Although each of these major cognitive constructs is defined and treated in various ways across studies, most accept that both imagery and WM involve a form of internal representation available to our awareness. ![]() ![]() The Smith-Kettlewell Eye Research Institute, San Francisco, CA, USA. ![]()
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