Inhibitory control of saccadic eye movements and cognitive impairment in Alzheimer’s disease

Background This study examined the relationship of inhibitory control and measures of neuropsychological impairment in patients with early Alzheimer’s disease (AD). Four specific questions were addressed: 1) Which error parameters of saccadic inhibition are sensitive to AD? 2) Which inhibitory deficits are related to cognitive measures of impairment? 3) Is the inhibitory impairment in AD dependent on the initiation of a volitional eye movement? 4) How do the effects of saccadic inhibitory control in AD relate to the normal effects of aging? Methods Eighteen patients with probable AD and two control groups (seventeen young, and eighteen old participants) completed a battery of neuropsychological tests and four saccadic eye movement paradigms: pro-saccade, NO-GO, GO/NO-GO and anti-saccade. Results Old controls generated increased inhibition errors in comparison to young controls in the GO/NO-GO paradigm. In comparison to old controls, AD generated normal saccades in the pro-saccade paradigm, but showed a higher proportion of inhibition errors in the NO-GO, GO/NO-GO and anti-paradigms. The frequency of uncorrected errors in the anti-saccade paradigm was positively correlated with cognitive measures of dementia. Conclusions AD patients have an impairment of inhibitory control and error-correction that exceeds the effects of normal aging and is related to the severity of dementia. However, the inhibitory impairment is not contingent on the interaction with a volitional saccade.