"Early" and Late: Saccadic Abnormalities in Frontotemporal Dementia
Objective: To characterise saccadic eye movements, as a marker of decision-making processes, in frontotemporal dementia (FTD).
Methods: Saccadometry was performed on a cross-section of FTD patients using a portable saccadometer and results were compared to matched control subjects. The Linear Approach to Threshold with Ergodic Rate (LATER) model was used to generate measures of decision-making speed and the incidence of any “early” saccades. Patterns of cortical atrophy were related to decision-making processes using voxel-based morphometry analysis.
Results: 45 subjects (22 FTD; 10 with bvFTD and 12 with PPA, and 23 controls) were studied. A measure of decision-making speed, μ, was reduced in FTD resulting in prolonged mean saccadic latency, despite an increased incidence of “early” saccades compared to controls. In addition, performance on an anti-saccade task was poor in FTD compared to controls. Decision-making speed and the incidence of “early” saccades were independently correlated with atrophy of the left frontal eye field, and decision-making speed also correlated with atrophy of the left cingulate eye field.
Conclusion: Saccades were abnormal in FTD, reflecting reduced decision-making speed, and these abnormalities related to atrophy of the left frontal eye field. In addition, FTD patients had an increased incidence of “early” saccades, which may be due to reduced inhibition of primitive responses.