Hemineglect (short for "hemispatial neglect") is a condition wherein a patient loses the ability to see, hear, or otherwise sense things occurring to one half of their body. It most commonly occurs after a stroke affecting the right parietal lobe, because this lobe only controls the left side field of vision, while the left lobe controls both fields; thus, it most commonly affects a patient's left side.
Sufferers of hemineglect may only shave half of their face, eat half the food on their plate, and fail to respond to speakers in their damaged line of vision and hearing. It is less a physiological blindness or deafness than a neurological denial that the other space even exists. For example, even after bumping into a wall due to their hemineglect, the person is unable to explain what caused them to fall.
Treatment for this generally consists of violating the "midline" separating their working from non-working side. Examples include throwing a ball back and forth from their left to their right, or having two speakers engage each other from opposite sides of the patient.
Compare to blindsight.