Apparatus for assessing electrical activity of a brain of a subject comprising: (a) stimulus means for generating and applying a repetitive stimulus to the brain comprising a light source (30) and control means (8) for varying the intensity of the light source in a repetitive manner; (b) detection means for distinguishing and detecting a steady state response of the brain to said stimulus, and for detecting a change or changes in said response comprising at least one electrode (1) for application to the head of a subject (3) to detect electrical activity of the brain; (c) signal processing (9) and data acquisition equipment (7) for processing the outputs of the electrodes; and (d) a helmet (2) comprising a substantially rigid outer layer (13), electrical screening layer (14), and an electrically insulating and cushioning layer (15), the helmet being provided with a plurality of bores (10) each bore being provided with locating means (11) for receiving and retaining an electrode in the bore for detecting local electrical activity in the brain of the subject wearing the helmet.
EQUIPMENT FOR TESTING OR MEASURING BRAIN ACTIVITY