Environment-driven responses in progressive supranuclear palsy.

The neurological signs and behaviors that accompany degenerative diseases associated with fronto-striatal dysfunction are incompletely described. We observed several novel environmentally-driven behaviors in seven patients with progressive supranuclear palsy (PSP). All patients had cognitive deficits with greatest impairments on tests of frontal lobe function, and frontal lobe cerebral perfusion was significantly reduced in 4 of the 5 who had single photon emission computed tomography (SPECT) brain scans. Visual grasping, in which a patient's gaze was attracted to an incidental object in the environment such as a TV set or mirror, was preeminent. Once fixed, there was inability to release the gaze and shift to another object. In other instances, removing a table placed in front of a patient or unbuckling of his seat belt would make him stand up, which was impossible on command. Similarly, playing music would induce rhythmic foot beating, which was never obtained on command. There were compulsive utilization behaviors, such as repetitively picking up and replacing the telephone for no apparent reason. As expected, there were signs of heightened facial reflexes, grasp reflexes, apraxia of eyelid opening, echolalia and echopraxia. We postulate that these stimuli-oriented behaviors stem from parietal lobe disinhibition due to fronto-striatal dysfunction.