| Background Proton magnetic resonance spectroscopy and cognitive impairment in patients with depression become a research hotspot in recent years, to investigate the correlation between them can help understand the brain functional activity of great significance.Objectives To identify the metabolite levels in frontal lobe and hippocampus in patients with depression by proton magnetic resonance spectroscopy (’H-MRS) and the characteristics of cognitive impairment; to investigate the relationships between the impact factors or cognitive impairment indicators and the neurochemistry metabolite levels.Methods46depressions met with CCMD-3with medicine-free for at least2weeks and46normal controls were assessed in this study. A multi-voxel’H-MRS provided by Siemens Medical Inc, event-related potentials P300and Wisconsin Card Sorting Test (WCST) on the computer provided by Beijing Heisman Development Co. Ltd. were given to all the subjects within24hours when they got in hospital; and the patients were also assessed the severity of clinical symptoms by means of Hamilton Depression Scale (HAMD) by two experienced doctors.’H-MRS were performed on a clinical1.5Tesla MR system. The repeat time (TR) was1500ms and the echo time (TE) was135ms. The region of interest (ROI) were sited in frontal lobe and hippocampus of all subjects, and the single volume was set at10mmx10mmxl5mm. The NAA, Cho and Cr were measured and the ratios of NAA/Cr and Cho/Cr were calculated by the computer automatically. Patient and control groups were given P300inspections and WCST to evaluate their cognitive function, the P300inspections were implemented by a doctor of the neuroelectrophysiological room, the research indicators included amplitude and latency of N2and P3; WCST were implemented by the same professional, the study indicators included the completion of the classification numbers (Cc), the error response numbers (Re), sustained numbers of error (Rpe), the numbers of required response to complete the first category (Rf) and the percentage of conceptualization level response (Rf%). All the data were analyzed by SPSS16.0including the general description, normal test, analysis of variance, with the use of independent-samples t test, Pearson correlation and multiple stepwise regression analysis, and the criterion of significance was set at α=0.05, two-sided test.Results The constituent ratio of sex of the patient and control group was same (χ2=0.044, P>0.05). There were no significant differences in age, educational background and temperature between the two groups (t=0.500,0.640and0.848, P all>0.05).1. Characteristics of1H-MRS:The NAA/Cr of bilateral prefrontal of the patient group (1.77±0.18and1.78±0.23) were lower than the control group (1.87±0.16and1.89±0.15), the differences were significant statistically (t=-2.816and-2.717, P all <0.01); the NAA/Cr of left hippocampus of the patient group (1.75±0.21) was also lower than the control group (1.87±0.27), the difference was significant statistically (t=-2.379, P<0.05); analysis of the laterality index, NAA/Cr ratio of bilateral hippocampus of LINAA/Cr (1.09±0.13) of the control group compared with1.0was significant difference statistically (t=4.695, P<0.01), the rest indicators of the laterality index of the patient and control group showed no significant differences with1.0(P all>0.05).2. Impact factors of H-MRS:Patients with depression of the male group, the later onset group, the short duration group and the first-episode group of the NAA/Cr values of the left frontal lobe were higher than the female group, the early onset group, the long duration group and the recurrent group (1.83±0.19, vs.1.70±0.12,t=2.711, P<0.01;1.86±0.16vs.1.70±0.19, t=3.028, P<0.01;1.83±0.17vs.1.71±0.20,t=2.192, P<0.05;1.83±0.17vs.1.73±0.15, t=2.107, P<0.05), the differences were significant statistically. The correlation analysis revealed that NAA/Cr ratio of the left prefrontal and left hippocampus were positively correlated with the age of onset (r=0.493and0.478, P all<0.01), were negatively correlated with the duration (r=-0.482and-0.470, P all <0.01).3. Cognitive function:The latency of N2and P3of patient group were longer than the control group (307.2±25.2vs.289.3±27.5, t=3.274, P<0.01;352.0±27.4vs.318.1±27.3, t=5.944, P<0.01), the differences were significant statistically; the amplitude of N2and P3were decreased than the control group (2.9±1.4vs.4.1±1.2,t=-4.414;5.6±1.2vs.6.9±1.1, t=-5.416, P<0.01), the differences were significant statistically. The WCST index Re Rpe and Rf of the patient group were higher than the control group (43.17±12.88vs. 28.29±10.67,t=6.034, P<0.01;30.30±14.13vs.14.93±8.06, t=6.713, P<0.01;14.40±5.70vs.11.64±1.96, t=3.106, P<0.01), the differences were significant statistically; the Cc and Rf of patient group were lower than the control group (3.48±1.97vs.4.92±1.17, t=-4.263, P<0.01;58.56±10.32vs.67.90±11.82, t=-5.326, P<0.01), the differences were significant statistically.4. Analysis of correlation showed that:the NAA/Cr of the left anterior frontal lobe of the patient group were positively correlated with the amplitude of P3and Cc, Rf%(r=0.345,0.316and0.335, P all<0.05); were negatively correlated with the latency of P3and Re, Rpe, Rf (r=-0.358,-0.366,-0.371and-0.294, P all<0.05). The NAA/Cr of the left hippocampus of the patient group were positively correlated with the amplitude of P3, Cc and Rf%(r=0.342,0.310and0.332, P all<0.05); showed negative correlation with the latency of P3and Re, Rpe, Rf (r=-0.351,-0.361,-0.369and-0.289, P all<0.05).5. Regression analysis showed that:age of onset, duration of the patient group into the regression equation of the NAA/Cr ratio of the left prefrontal; age of onset of the patient group into the regression equation of the NAA/Cr ratio of the left hippocampus.Conclusions1. Structure and function of neurons are abnormality at the bilateral prefrontal and left hippocampus of the depressions, while the asymmetry of the hippocampal is disappeared.2. Patients with depression are cognitive dysfunction, related to the low expression of the NAA at the left prefrontal cortex and the left hippocampal.3. The level of the neural biochemical metabolites NAA at the left prefrontal and the left hippocampus are affected by the factors of age of onset, duration, whether the first or recurrent depressions and so on. |
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