3/2/2023 0 Comments Artmatic 4.7![]() ![]() Support of domain specificity from the human neuroimaging literature has been inconsistent. On the basis of primate working memory studies using single-cell recordings, the model states that ventrolateral PFC (BA 12 and 45) is involved in working memory for nonspatial material, whereas dorsolateral PFC (BA 46) is involved in working memory for spatial information ( Goldman-Rakic, 1995 Wilson, Scalaidhe, & Goldman-Rakic, 1993). The domain specificity model is an extension of primate studies linking object identification (“what”) with a ventral occipitotemporal pathway and spatial perception (“where”) with a dorsal occipitoparietal pathway ( Ungerleider & Haxby, 1994 Ungerleider & Mishkin, 1982). Investigators have also tried to delineate prefrontal regions on the basis of stimulus domain. Thus, it appears that the dorsolateral PFC is not only involved in executive processes, such as the manipulation and monitoring of information, but also may work in concert with the ventrolateral PFC during active maintenance. Similarly, D’Esposito, Postle, and Rympa (2000) found sustained activation in both aspects of the PFC for tasks requiring maintenance only and for tasks involving maintenance plus manipulation. These authors concluded that dorsolateral PFC is involved in both maintenance and manipulation. This was inconsistent with the assumption that executive processes are transient. ![]() (1997) examined the temporal dynamics of working memory with fMRI and found that dorsolateral PFC activation increased with working memory load and did not decrease over time. However, this functional dissociation appears to be relative rather than absolute. maintenance plus monitoring and manipulation) and generally find that ventrolateral PFC mediates maintenance of verbal and non-verbal information and that dorsolateral PFC is involved in executive components of monitoring and manipulation ( Berman, Austin-Lane, Esposito, Van Horn, & Weinberger, 1996 Klingberg, O’Sullivan, & Roland, 1997 Manoach et al., 1997 Salmon et al., 1996 Stern et al., 2000 Tsukiura et al., 2001). These studies contrast specific functions (e.g., maintenance vs. This model is broadly supported by reviews of human imaging studies of working memory ( D’Esposito et al., 1998 Owen, 1997). According to the model, ventrolateral prefrontal cortex (PFC Brodmann’s area 44, 45, and 47) is responsible for maintenance of information in the visuospatial and phonological stores, and dorsolateral PFC (BA 9 and 46) is required for CES processes of monitoring and manipulation ( Petrides, 1994). The process specificity model attempts to parse prefrontal regions mediating different components of working memory. Demonstrating similar effects of working memory load on the two tasks provides initial evidence for the construct validity of the new task. The goal of the current functional magnetic resonance imaging (fMRI) study is to use a parametric n-back paradigm ( Awh et al., 1996 Braver et al., 1997 Cohen et al., 1994, 1997 Gervins & Cutillo, 1993 Smith, Jonides, & Koeppe, 1996) to contrast the effect of working memory load on regional brain function during a standard letter n-back task versus an n-back task using complex geometric objects that have not been previously studied. Much of the research on working memory has focused on anatomically dissociating these multiple processes. The visuospatial sketch pad maintains visuospatial information in a temporary visuospatial store, and the phonological loop maintains verbal material in a phonological store through an articulatory rehearsal process. The CES allocates attentional resources and is responsible for coordination of top–down processes permitting monitoring and manipulation of information within the short-term store (e.g., temporal sequencing). Working memory is conceptualized as having several components including a central executive system (CES) and two modality-specific slave systems: the visuospatial sketch pad and the phonological loop ( Baddeley, 1986, 1992 Baddeley & Hitch, 1974). Working memory refers to a limited capacity system responsible for temporary maintenance and online manipulation of information required for guidance of subsequent behavior. ![]()
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