Enhanced Visual Motion Perception in Major Depressive Disorder

In this paper, Golomb et al. use a psychophysical technique developed by Tadin et al (2003) to measure surround-suppressive interactions in visual cortex. However, there is actually very little evidence that thresholds obtained with this technique have anything to do with center-surround antagonism. My colleagues and I published data, concurrently with Golomb et al., which suggest that the paradoxical "impairments" in motion perception in normal subjects (and therefore perceived "improvements" in abnormal populations) are a consequence of how the contrast and size of the stimulus are co-varied (Aaen-Stockdale et al., 2009). We found that motion discrimination thresholds are entirely predictable from the observer's contrast threshold at each stimulus size. These low-level factors can explain the effect reasonably well without any need to invoke center-surround antagonism. It remains to be seen what is causing the difference between normal subjects and recovered depressives, but we suspect that it is not surround suppression. This obviously throws doubt on the speculative connection with degraded GABAergic center-surround mechanisms in the depressed population.

Aaen-Stockdale, C. R., Thompson, B., Huang, P.-C., & Hess, R. F. (2009). Low-level mechanisms may contribute to paradoxical motion percepts. Journal of Vision, 9(5):9, 1-14, http://journalofvision.org/9/5/9/, doi:10.1167/9.5.9.

Tadin, D., Lappin, J. S., Gilroy, L. A., & Blake, R. (2003). Perceptual consequences of centre-surround antagonism in visual motion processing. Nature, 424, 312–315.