Major depression affects perceptual filling-in.

Background: Major depression disorder is a syndrome that involves impairment of cognitive functions such as memory, attention, and plasticity. In this study, we explored whether depression affects perception as well.

Methods: We used a recently developed paradigm that assesses the filling-in process by probing false-positive reports (false alarm [FA]), hit rates (pHit), sensitivity (d'), and decision criteria (Cr). We used a Yes-No paradigm in a low-level detection task involving a Gabor target, in the presence of collinear flankers, inducing filling-in, with differing target-flanker separations of 3-15 lambda(wavelength). The depressive state of patients was assessed using the Hamilton Depression Rating Scale. Two groups were tested: an experimental group with major depression (n = 27) and a control group (n = 32).

Results: The performances of the control and the experimental groups were not significantly different regarding d'. In contrast, a specific pattern of significant differences between the control group and the hospitalized group was found for the decision criterion, pHit, and pFA, but only for target-flanker separations of 3 lambda, whereas the results for the other separations were insignificant. The differences between the control and the depressed groups are not due to a global cognitive dysfunction in depression.

Conclusions: The results suggest that the filling-in process is deficient, probably because of reduced excitation among neurons. Neural excitation is a key factor in the neural processing involved in memory and decision making. In addition, it is still possible that the patients may be unable to match their internal representation to the changing sensory information.