Functional neuroanatomy of delay tasks, delayed response, delayed alternation and object alternation

grantor: University of TorontoThe functional neuroanatomy of human performance on 4 delayed response tasks (spatial/object delayed response [DR-S/DR-O] and spatial/object alternation [DA/OA]) was investigated using functional magnetic resonance imaging. Tasks were presented to 5 healthy participants (Mean age = 20 years; 3 males) in a blocked design while in a 1.5T scanner. Dorsolateral prefrontal activations were noted in Brodmann areas 8, 9, 10, 46 for all tasks. Several areas were specifically correlated with object-based task performance and included Brodmann areas 32, 6, 40 (OA) and the thalamus bilaterally (DR-O). Neither mnemonic domain (Goldman-Rakic, 1987) nor processing (Petrides, 1996) theories of functional specialization for working memory within the prefrontal cortex were supported. Findings were consistent with a model of functional dissociation between memory selection and maintenance processes in prefrontal cortex (Rowe et al., 2000). Anterior cingulate activations during OA are consistent with studies implicating this structure in response inhibition and cognitive control.M.A