Event-related Potentials On Information Processing During Mental Rotation Tasks In Major Depressive Disorder

Cognitive function defect is a common symptom of depression patients, whichmemory, language intelligence quotient (IQ), operating IQ and executive functiondecreased obviously in patients with depression in the acute phase. Mental rotation (MR)is the ability to rotate mental representations of two dimensional and three dimensionalobjects. This usually refers to imagined rotation of an object from one orientation toanother. Language ability and spatial ability or intelligence is one of the basic ability,which just many scholars confirm MR is often cited as a prototypical higher-levelvisuo-spatial cognitive operation. Relatively previous studies showed the correlates ofimpaired performance for object rotation and psychomotor disturbance in unipolar major depression, showing a progressive slowing with increasing angle of orientation indicatinga specific slowing of MR relative to the controls. This study is to evaluate the change ofelectrophysiological mechanism of MR information processing by the high temporalresolution ERP technology in order to offer theoretical basis for the cognitive model ofhigher-level visuo-spatial information processing of patients with depression, and willprovide a objective laboratory index for its pathogenesis, early clinical diagnosis,rehabilitation and prognosis research.A total o f52depressive disorder (patients group) were recruited for this studyfrom the Center for Mental disease Control and Prevention, Third Hospital of the People’sLiberation Army, Baoji, China, from January2011to December2011and completedmental rotation tasks (object and self rotation tasks). The event-related potentials (ERPs)were recorded when they did tests and the latency and amplitude of P500(400～600ms)was analyzed over the parietal lobe. And we compared the results in patients and thosein50normal healthy subjects (control group) to observe the change ofelectrophysiological mechanism of MR information processing in patients with depression.The experiment is divided into two parts: first, all subjects were asked to makemirror/normal discrimination object rotation tasks by the ERP system to explore theabnormalities of electrophysiological mechanism of object rotation information processing;second, all subjects were asked to make left/right hand discrimination self rotation tasksby the ERP system to explore the abnormalities of electrophysiological mechanism of selfrotation information processing.The main conclusions of the present study are as follows:First, patients with depression present a selective defcit on the brain visuo-spatialelectrophysiological mechanism for object rotation. Importantly, patients’ deficits weremore seriously present specific to normal than mirrored rotation, and in male than female.Indivudals with depression were slower and made more errors in mentally rotating normaland mirrored letters than healthy controls. The P500amplitude was signifcantly lower atparietal site in normal and mirror in patients than controls. And individuals withdepression exhibited a greater difference in response times, error rates, and P500 amplitude in normal than mirrored letters, and in male than female. If compared to thehealthy subjects, the brain activation in patients reveal a weak activation of the bilateralparietal cortex, the bilateral lateral occipito temporal cortex and the bilateralparietal occipital cortex in200～600ms time window. Moreover, the response times andP500amplitudes in normal and mirror were absence of a typical function of orientation inpatients. This study suggests the information processing mechanism of object rotation indepression patients can be damaged, which may provide a objective laboratory index forclinical auxiliary diagnosis.Second, patients with depression present a selective defcit on the brain visuo-spatialelectrophysiological mechanism for self rotation. Importantly, patients’ deficits were moreseriously present specific to right than left hand rotation, and in male than female.Moreover, the larger deficits were observed for hand orientations (180°) for which actualmovements would be more difficult and may reflect the anatomical constraints of realhand movements. Indivudals with depression were slower and made more errors in rightand left hand than healthy controls. The P500amplitude was signifcantly lower, and thelatency was signifcantly longer in right and left hand at parietal site in patients thancontrols. And individuals with depression exhibited a greater difference in response times,error rates, P500amplitude and latency in right than left hand, in male than female, and inbeyond180°rotation than within the scope of the180°rotation angle. There was verylittle activity in the left parietal site or in the region between the left parietal site and theleft occipital site in200～600ms time window, and there was a delay in the activation inthese regions for the hand image in depression patients in comparison to the stronglybilateral activations in the control group. Moreover, the response times and P500amplitudes in right and left hand were absence of a typical function of orientation indepression patients. This study suggests depression patients present lager defcit on theinformation processing mechanism of self than object rotation, which were not onlypresent in information processing speed and extent, but also in the correspondingfunctional areas of the change brain neural cortex which may provide a potentialbiological definition markers for depression.