A Study On Mechanism Of Theta Oscillations Absence Of Working Memory Disorder In Cerebral Small Vessel Disease

Objective:The behavioral and electroencephalograph(EEG)oscillation data of visual object working memory(WM)in patients with cerebral small vessel disease(CSVD)and normal controls were compared to investigate the mechanism of WM theta oscillation absence and provide a new thought and technology for clinical treatmen in CSVD.Methods:The number of CSVD and the normal controls were 17 respectively.They were asked to perform a visual object WM task(memory load of 4)using delayed matching-to-sample task(DMS),record the behavioral data(the accuracy and response time)and the 21-channel EEGs.The original 21-channel EEGs were pretreated.Short-term Fourier transform(STFT)was applied to calculate the average energy density of 3s delay period in each frequency band,and the average time-frequency map of 1-21 channels were drawn,the frequency band with the maximum energy density of the normal control group was selected as the characteristic frequency band of WM.Drawing the space distribution map of the average energy density of the two groups in the characteristic frequency band and the brain region with the maximum energy density of the normal control group was selected as the characteristic brain region of WM.The WM behavioral data and frequency and space distribution of the two groups were statistically analyzed.Result:1.The demographic and clinical data of the subjects: The number of CSVD and the normal control group were 17 respectively(including 247 experiments in CSVD,and 234 experiments in the controls).Both groups showed no statistical significance in age,sex and education years(P > 0.05).The MMSE and MoCA scores of the CSVD group were lower than those in the normal control group(P < 0.01).2.The CSVD had statistical significance in WM behavioral results,showing that the response time was prolonged and the accuracy was decreased(P < 0.001).3.The average energy density in the whole frequency band of the Fp2 channel is highest,suggesting that Fp2 channel may be the characteristic channel and the characteristic brain area is the forehead area of WM.4.The time-frequency map in the Fp2 channel of the control suggest that the critical memory period of WM is the 3s delay period,and the characteristic frequency band is theta frequency band(4-8Hz).In addition,the energy density in the 3s delay period of Fp2 channel in the CSVD group was lower than that in the control group.5.The energy density of the theta frequency band in control was higher than that of other frequencies(LSD-t test,P < 0.001).In addition,the energy density of the theta frequency band was lower than that in control(P < 0.001).6.The space distribution map of the theta frequency band in the 3s delay period of control suggest that the energy density in theta frequency band is mainly distributed in the frontal region,especially the right frontal area.Compared with the control,the energy density in the CSVD group was significantly reduced in the frontal region.7.The energy density in 3s delay period of the frontal region in control was higher than that of other areas(LSD-t test,P < 0.001).The energy density of the frontal region in the CSVD group was lower than that in control(P < 0.001).8.The energy density of the right frontal region in the CSVD group and the control was higher than that in the left and the middle frontal area(LSD-t test,P <0.001).Conclusion:1.There were WM behavior disorders in CSVD patients: the response time was prolonged and the accuracy was decreased.2.The characteristic frequency band of the visual object WM is the theta band,and the characteristic brain area is the forehead area,and the right hemisphere may be the dominant hemisphere of the visual object WM;3.The weakness or absence of theta oscillation is the possible neural mechanism of WM disorder and can provide a new thought and technology for clinical treatment in CSVD.