Memory and executive functions in healthy subjects and patients with multiple sclerosis: the role of PET and SPECT

Despite extensive research, the precise role of different brain areas in mo dulating attentional and mnemonic processes is still controversial. Using p ositron emission tomography (PET) or single photon emission computed tomogr aphy (SPECT), we can measure changes which are associated with the level of neuronal activity in normal subjects and in patients. We describe the patt ern of activation in attentional processes, with respect to three basic com ponents: vigilance, selective attention and attentional processing capacity . Furthermore, we underline the predominant role of frontal and temporal co rtices that mediate different activities associated with memory function. Functional techniques have substantially contributed to a better understand ing of the cognitive deficits associated with multiple sclerosis (MS), sugg esting that cortical-subcortical disconnection is the most likely cause of the neuropsychological deficits. The difficulties in attempting to attribut e specific cognitive abnormalities to focal brain pathology in presence of widespread disease such as MS will probably be attenuated by functional neu roimaging studies.