The panoply of field-dependent behavior in 1436 stroke patients. The mirror neuron system uncoupled and the consequences of loss of personal autonomy

Evaluation of the multifaceted nature of frontal network syndromes is uniquely challenging and rarely tested in the acute/sub-acute stroke period. Field-dependent behavior such as imitation behavior, utilization behavior, and environmental dependency syndrome, as a component of altered environmental autonomy, may be a reliable bedside test. This research focused on the frequency of field-dependent behavior in stroke, the subtypes and relation to frontal lobe lesion location and stroke etiology. A validated frontal network score incorporating a 10-point imitation behavior scale was applied to alert patients without significant aphasia, encephalopathy, dementia, or substance abuse. Discriminative validity assessment with magnetic resonance imaging, diffusion weight imaging (MRI-DWI brain) was performed and correlational validity was established using standard neuropsychological tests. Of the stroke patients (n = 1436), those with frontal network symptoms (335/1203; 28%) were analyzed further. In the 73 patients with lesions restricted to the frontal lobes or the frontal subcortical circuits, 56 complied with the 10-point imitation behavior scale testing. Forty-five of 56 (80%) demonstrated imitation behavior (sensitivity 73% and specificity 94%). Correlational validity testing with four commonly used frontal lobe neuropsychological tests was good. The stroke etiology included 26 (59%) "other" causes, 9 (20%) intracerebral hemorrhages, 3 (7%) cardioembolic causes, 3 (7%) large vessel disease, 2 (4%) small vessel disease, and 2 (4%) unknown etiology. Field-dependent behaviour subtypes included imitation behavior (n = 45), utilization behavior (n = 9), environmental dependency syndrome (n = 4), and complex other forms of environmental dependence syndrome (n = 5). It was concluded that imitation behavior is a relatively common occurrence with lesions in the frontal lobes in the acute/sub-acute stroke period and is associated predominantly with non-mainstream (other) stroke causes and intracerebral hemorrhage.