Early Stage Of Face Perception In Patients With Late-onset Depression: An Event-related Potentials Study

Objective: Late-onset depression (LOD) is one of the most frequent psychiatric disorders in the elderly, being strongly associated with not only aging but also disease-related brain abnormalities. Compared with the younger depressives, genetic factors are generally thought to be less significance in the subjects with late-onset depression. Besides the characterized affective syndrome, the elder depressed adults are often accompanied by cognitive impairment, which may influence social function and interpersonal relationships.Human face processes are becoming a basis of social communication. The cognitive theory of psychopathology highlights the importance of the problematic interpersonal communication in the onset and maintenance of depression. There is ample evidence that the face processing is impaired in the younger depressives. However, whether the LOD patients have a special deficit in the face perception compared with the normal old controls is unclear. Event related potentials (ERPs) provide effective electrophysiological information for the timing of the processing stages. It has been shown that the N170 component, a negative shift occurring between 130-190 ms after stimulus onset at occipito-temporal electrodes, is larger for human faces than other visual stimuli (the N170 effect) and delayed (sometimes increased) by inverted faces (the N170 inversion effect), reflecting the detection of physiognomic information and the configural processing of faces, respectively. The present study was to investigate early stage of face detection and configural analysis in patients with late-onset depression by using ERP method.Methods: Seventeen depressive patients aged at least 60 years (mean age: 70.5±6.2 years; 7 male, 10 female) and 16 nondepressed, age- and gender-equated (mean age: 67.3±5.1 years; 4 male, 12 female) control subjects were recruited for this study. We used 17 items Hamilton Rating Scales of Depression to assess the severity of depressive state. Global cognitive function was assessed to screen for dementia using the Mini-Mental State Examination. All subjects performed a passive paradigm. Stimuli randomly presented in the centre of screen consisted of faces and furniture with upright and inverted equal probability as well as butterflies as targets, and the subjects were instructed to count butterflies (targets) and ignore the non-targets. Thirty two channel electroencephalogram (EEG) was recorded by Neuroscan Nuamps System. After average reference calculation, the peak amplitudes and peak latencies of the P1 in occipital-temporal sites (T5, T6, O1, O2) were measured for individual subjects, as well as the occipital-temporal N170. On the basis of the robust N170 for the face stimuli, we obtained the difference waveforms by subtracting the ERP to furniture from that to faces, and measured the peak values and latencies of the Nd170 at occipital-temporal electrodes. And the amplitudes and latencies of P3 in the frontal (FZ), central (CZ), and parietal (PZ) regions were also measured to test the basic cognitive function for the LOD group. The above components were analyzed using repeated measures analysis of variance (RMANOVA).Results:1,The occipital-temporal P1 and N170 elicited by non-target stimuli were significant decreased in the patient group than that in normal controls, (P<0.02 and P<0.01).2,Across both groups, the N170 elicited by face stimuli was stronger than furniture did (N170 effect) and delayed by inversion (N170 inversion effect). Over the right temporooccipital area (T6) there was an impairment of the N170 effect (P<0.02) not N170 inversion effect (P>0.05) for the LOD patients than for the normal controls.3,P3 was significantly delayed in the patient group than the normal controls (P<0.05).Conclusion:1,The patient group has basic cognitive impairment. 2,The patients with LOD have the generalized abnormality of early visual processing, shown as more slow and poor information processing compared to the normal elder subjects.3,The early stage of face detection not the configural analysis of faces is impaired for patients with late-onset depression.4,Early-stage face processing dysfunction may play a crucial role in poor social interaction in patients with LOD.