Improving Neglect by TMS

Hemispatial neglect refers to the defective ability of patients to explore or act upon the side of space contralateral to the lesion and to attend to stimuli presented in that portion of space. Evidence from animal models suggests that many of the behavioural sequelae associated with visual neglect may result not solely from the size of the lesion, but also from a pathological state of increased inhibition exerted on the damaged hemisphere by the contralesional hemisphere. On the basis of these potential mechanisms underlying neglect, in this review we discuss therapeutic approaches, focusing particularly on recent research using transcranial magnetic stimulation (TMS). This technique, besides representing an ideal tool to investigate visuo-spatial attentive mechanisms in humans, has shown promising beneficial effects that might have an impact on clinical practice

SPATIAL HEMINEGLECT IN BACK SPACE

The subjective location of the mid-sagittal plane was assessed by a free-field auditory localization task in the front and in the back half-spaces in 11 right brain-damaged patients with spatial hemineglect, 10 right brain-damaged patients without spatial hemineglect and 11 normal control subjects. In patients with hemineglect the subjective mid-sagittal plane was found to be displaced rightwards in both half-spaces. Both patients without hemineglect and controls, in contrast, made a minor error and showed a greater displacement towards the left side in the back half-space. In four right brain-damaged patients the rightward displacement was confined either to the front, or to the back half-space. This pattern of impairment may be explained by a rightward, ipsilesional, pathological translation of an egocentric coordinate system, rather than by a rotation around the vertical axis of the body

Beyond unilateral neglect

When required to set the endpoints of an imaginary horizontal line of a given length on the basis of its midpoint printed on a sheet of paper, left neglect patients more frequently misplaced endpoints leftwards. Through giving rise to the very same disproportion usually found with these patients on canonical line bisection tasks, this behaviour cannot be accommodated by current explanations of unilateral neglect. When the task was executed during leftward optokinetic stimulation (OKS), a manoeuver known temporarily to improve neglect symptoms, the disproportion increased instead of vanishing. We therefore suggest the unilateral neglect is a manifestation of a disorder primarily implying a horizontal anisometry of space representation and that manipulations such as OKS may remove neglect without normalizing the representational medium itself