Objective: Deficits in executive control and attention are becoming increasingly recognized as a focus of early impairment in Alzheimer’s disease (AD). There is increasing evidence of a strong overlap in the cortical brain areas that control saccadic eye movements and covert attention. Visual attention is most readily indicated by the line of sight. The close relationship between the direction of gaze and attention enables the location of visual attention to be inferred directly from eye movement recordings.
Design: Eighteen dementia patients with clinical diagnosis of Alzheimer’s disease (AD) (thirteen males and five females; mean age 76.7, SD = 4.4, range 70-88 years) at the Memory Clinic of the Directorate of Old Age Psychiatry, Lytham Hospital, England, volunteered for a longitudinal study of eye movements in Alzheimer’s disease.
Materials and Methods: All patients fulfilled the diagnostic criteria for probable AD according to National Institute of Neurological and Communicative Disorders and Stroke (NINCDS) diagnostic criteria. Data from age-matched control volunteers were gathered from eighteen non-demented healthy volunteers (seven males and eleven females; mean age 70.3, SD = 5.9, range 63-86 years). Participants were asked to complete a series of saccadic tasks. Oculomotor performance were compared in two types of tests; the reflexive saccadic eye movements and anti saccade tests. The first test will detect primarily abnormalities due to low-level defects of vision, attention and motor control. The antisaccade test examines the control of response inhibition that involves the cognitive resources of the prefrontal cortex and other cortical areas. Participants returned to the laboratory within a two-week window, to complete a neuropsychological test battery.
Range of Correlates: Standardized Mini Mental State Examination (SMMSE), (Molloy etal, 1991) – brief screening instrument for dementia; European Alzheimer’s Disease Assessment Scale Cognitive Sub-Test (EADAScog) Clinical Dementia Rating Scale (CDR), Neuropsychiatric Inventory (NPI), Alzheimer’s Disease Functional Assessment and Change Scale (ADFACS), Geriatric Depression Scale, National Adult Reading Test (NART), Verbal Fluency Trail Making, Digit Span, executive function, Gibson Spiral Maze, Spatial Span. Analysis of total prosaccadic errors from REFLEXIVE gap and REFLEXIVE overlap paradigms, revealed no significant differences between-groups (see means, Fig. 4). Patients generated significantly more inhibition errors in both Anti GAP and Anti OVERLAP in comparison to further t-tests revealed significant differences between-groups for total errors in both antisaccade paradigms, Anti Gap: (Controls mean =, Patient means = ; t (22.6) = -3.6 p< 0.002 and Anti Overlap task (controls means = , patients mean = ; t (33) = -3.9 p< 0.001). Patient dementia severity was found to be highly correlated with uncorrected errors in the antisaccade gap paradigm, significant (r = 0.83; n = 17; p< 0.001).
Conclusion: These results suggest an attentional deficit in the attentional control of saccadic eye movement in patients with Alzheimer's Disease.
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