[Electrophysiological study of attention mechanisms in depressed patients with characteristics of psychomotor retardation]. / Etude électrophysiologique des mécanismes attentionnels chez des patients déprimés caractérisés par un ralentissement psychomoteur.

ABSTRACT

The ERPs and RTs of 8 drug-free depressed in-patients (mean age 58, with marked psycho-motor retardation) were recorded during a dichotic listening RT task and compared to those of 9 healthy, age-matched controls. The depressed showed significantly longer, more variable RTs than the controls and made more mistakes. Their ERPs for targets in the attended ear differed significantly from those of the controls by the small amplitude (or absence) of the N2 vertex component elicited by the controls in such a situation and by the presence in the same situation of a late frontal slow negativity (LFN) that did not show up in the grand average ERP of the control group. These results were discussed in terms of the two components of the processing negativity described by Näätänen (1982, 1985) and according to resource models whereas the controls would perform quickly this easy task thanks to quasi-automatic matching processes (reflected by the vertex N2), the depressed would need further effortful, controlled processing (reflected by the LFN) in order to perform the same task. The ERPs of 6 of these depressed were recorded a second time, after anti-depressive treatment and clinical improvement. A tendency to improved RTs and ERPs (amplitude decrease of the LFN and increase of N2) was seen in most patients, but these improvements were far from being as marked as the clinical improvement.