Figure 3.

Hypothetical model of functional connectivity alterations in association with executive eye movement control in Parkinson’s disease (PD). The model results from correlations between functional connectivity data and eye movement impairment in early and advanced patients with PD (63). Neural damage due to the ongoing PD-associated pathological process from (A) healthy or premotor to (B) clinically manifest disease status paradoxically results in increased functionally connectivity early in the course of the disease upon a critical cell loss is reached. During this phase, executive oculomotor function gradually worsens as evidenced from visually guided reactive saccade performance (lower row)—remarkably, neuropsychological assessment in these patients revealed cognitively unimpaired “normal” performance (67). (C) In the final stages of PD, patients most patients met the criteria of PD-associated dementia and have developed a function disconnection syndrome (decreased functional connectivity) that is associated with a pattern of severely impaired eye movement control (right lower panel).