Authors:

Gould, R.L., Brown, R.G., Ffytche, D.H., Howard, R.J. & , OWEN, A.M

Reference:

Year of publication:

2003

CBU number:

5836

Abstract:

Functional magnetic resonance imaging (fMRI) was used to assess cortical activations associated with increasing task difficulty (TD) in a visuospatial paired associates learning task. Encoding and retrieval were examined when 100% successful retrieval of 3, 4 or 6 object-location pairs had been attained (thus ensuring that performance was matched across subjects). As memory load increased, in general, the number of attempts taken to achieve 100% successful retrieval increased, while the number of trials correctly completed on the 1st attempt decreased. Comparisons between levels of memory load (6 vs 3, 6 vs 4 and 4 vs 3) during retrieval revealed load-dependent activations in occipito-parietal cortices (including the inferior parietal lobule and middle occipital gyrus) and the cerebellum. Significant signal changes in the left DLPFC and anterior cingulate were only found in the contrast between 6 versus 3 items, while right inferior frontal and left middle frontal gyri were found when comparing 6 or 4 items versus 3 items. During encoding, a similar pattern of cortical activation was evinced, though only in the comparison between 6 versus 3 items. The cortical response to increasing cognitive demands or TD appears to involve the same network of occipital-parietal regions "working harder", coupled with the recruitment of additional "compensatory" frontal regions.