Physiologic theories of emotion suggest that activation is important in the experience of emotion; patients exhibiting “neglect” as a consequence of right parietotemporal dysfunction show flattened affect. We studied arousal in patients with lesions of the right hemisphere who also exhibited emotional indifference, in aphasic patients with lesions of the left hemisphere, and in non-brain-damaged controls, by stimulating the forearm ipsilateral to the side of the brain lesion while recording galvanic skin responses (GSRs) from the fingers on the same side. The group exhibiting neglect had lower GSRs than aphasic patients or non-brain-damaged controls. Aphasic patients had higher GSRs than non-brain-damaged controls. These results suggest that neglect is associated with disturbances in bilateral arousal and that this disorder of arousal may be responsible in part for flattened affect. The heightened GSR in aphasic patients may reflect disinhibition, which might be partly responsible for increased emotionality in these patients. © 1978 American Academy of Neurology.