Impaired decision-making and diffusion orientational complexity in people with multiple sclerosis

This study looked at cortical grey matter using a new measure of the number of diffusion orientations on diffusion MRI ‘diffusion orientation complexity (DOC)’ in areas known to be associated with performance on the Cambridge Gambling Task (CGT) in 105 people with MS and 36 healthy controls. The CGT was used to assess decision making. Grey matter regions associated with decision-making including the caudate, hippocampus, middle frontal gyrus, anterior cingulate and the medial prefrontal cortex were masked using the Oxford-Harvard template. The mean DOC was measured in these regions.

The researchers found that people with MS showed less adjustment of bets to account for the level of risk and were significantly slower at making decisions on the CGT. DOC was lower in the caudate, middle frontal gyrus, anterior cingulate and the medial prefrontal cortex, and significantly higher in the hippocampus in people with MS when compared to controls. Also in people with MS, risk correlated with hippocampal DOC, the medial prefrontal correlated with the length of deliberation, and the anterior cingulate correlated with the quality of the decision making.

This study demonstrates that impaired decision making in people with MS relates to problems in adjusting to levels of risk rather than increased impulsivity. The changes seen in DOC in grey matter regions, which was associated with decision-making functions, suggest a relationship between abnormal grey matter microstructure.

Authors: Muhlert N, Sethi V
Source: J Neurol Neurosurg Psychiatry. 2013 Sep;84(9):e1. doi: 10.1136/jnnp-2013-306103.21.

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