Is space representation distorted in neglect?

It has been argued that neglect of contralateral stimuli following brain damage might be associated with either a compressed or an anisometric neural representation of space along the earth-horizontal axis. Two different models have been put forward. One model proposes a uniform compression of subjective space, while the other envisages an expansion on one side of space and a compression on the other. We tested these models by determining neglect patients' perception of spatial distances in the horizontal plane. The models differ concerning the expected degree of under- vs overestimation of distances in the left and right hemispace. In the first experiment, patients were asked to position ten red LEDs equidistantly along a semicircle, which was located horizontally in front of them at eye level. A second experiment compared the patients' subjective perception of short, medium and long distances extending into left and right hemispace. We found no evidence for any compression or expansion, nor for anisometry along the earth-horizontal axis. These findings argue against a distortion of subjective space along the horizontal axis in patients with neglect which could account for their failure to orient towards and to explore the contralesional parts of space.