fMRI investigation of disinhibition in cognitively impaired patients with multiple sclerosis

Although deficits in executive functioning are well known cognitive sequelae of multiple sclerosis (MS), less is known about patients' performance on response inhibition tasks in particular. Behavioural observation of cognitively impaired MS patients often reveals impulsivity. However, knowledge about associated neural activity during response inhibition measurable with functional magnetic resonance imaging (fMRI) is lacking. In the current study the performance and fMRI activation patterns of patients with MS on a response inhibition task (Go/No-Go) were investigated.

Ten cognitively impaired patients with MS (with little or no physical disability) and 10 sex-, age- and education-matched healthy controls performed a Go/No-Go task while in the MR scanner.

MS patients had significantly more commission errors than controls but did not demonstrate longer reaction times. Controlling for this difference, whole brain random effects analyses revealed that patients demonstrated more activation than controls in the fusiform gyrus, cingulate gyrus (including the anterior cingulate gyrus), cerebellum and putamen. Patients demonstrated less activity than controls in the supramarginal gyrus.

MS patients exhibited significant neural compensation during response inhibition when compared with controls. The specific results provide new insight into the neural processing underlying the impulsivity often observed in cognitively impaired individuals with MS.