| PurposeWe observed and analysed the attention components of event related potentials (ERPs) evoked by various stimulus modalities in patients with subcortical ischemic vascular cognitive impairments (SIVCI) and the clinical neuropsychological test, in order to find neuroelectrophysiological indeces to reflect attention impairment in earlier period of vascular cognitive impairment for improving its diagnostic quality. We studied the relationship between diseased region and brain electrical source analysis of event related potentials, in order to investigate the influence on attention nerve loop by ischemic impairment from small subcortical vessel lesion, and enhance the understanding for the pathomechanism of subcortical ischemic vascular impairment .MethodsThe subjects included 30 patients with vascular cognitive impairment no dementia (SIVCIND), 15 patients with subcortical ischemic vascular dementia (SIVD) and 15 age, sex, and education-matched normal control. The general cognitive functions of the subjects were assessed by Montreal cognitive assessment (MoCA) Beijing Version and mini-mental state examination (MMSE), attention functions were assessed by continuous performance task (CPT), stroop test and Dual task. The event related potentials different wave P20-50, Novelty P3a and contingent negative variation (CNV) of the subjects evoked by dichotic listening, novelty stimulus Oddball mode and order-command signal two-stimulus paradigm were recorded.We locate the source position of ERPs component by brain electrical source analysis (BESA) and draw cortical current source density (CSD) and analysis cortical functional transactivation domain for investigating electrophysiological variation characteristics of cortical attention functional zones.Results 1. The general assessment of cognitive functional of patients with SIVDSIVD patients had obvious cognitive disorder in visuospatial and executive function, attention, delayed memory, abstract and orientation (P<0.05), and no cognitive disorder in naming and verbalization compared with NC (P>0.05). SIVCIND patients had obvious cognitive disorder in visuospatial and executive function, attention and delayed memory(P<0.05), and no cognitive disorder in abstract, orientation, naming and verbalization compared with NC(P>0.05).2. The neuropsychological assessment of attention(1)Continuous performance task (CPT) ---a computer-assisted test for assessing sustained attentionReaction time of CPT had significantly prolonged and omission rate of CPT had increased in SIVD patients(P<0.05)compared with NC. Reaction time in CPT had no significantly prolonged (P>0.05) and omission rate had increased in SIVD patients(P<0.05)compared with NC(P <0.01).(2) Stroop test ----a computer-assisted test for assessing selective attentionIn stroop test, reaction time under conflict condition had significantly prolonged(P<0.01), reaction time under neutral condition condition as well as RT stroop effect under conflict and neutral conditions had not prolonged (P>0.05) ,and error rate under conflict and neutral conditions had significantly increased(P<0.01), interfered effects of error rate under conflict and neutral conditions had not increased (P>0.05) in SIVCIND patients compared with NC. Reaction time, error rate and their interfered effect had obviously increased in SIVD patients compared with NC (P<0.01).(3)Dual task -----for assessing divided attentionSIVCIND group did as well as the normal control in the Dual task test (P>0.05). SIVD group did worse in dual task than control subjects (P<0.01).3. Detection of attention component of event related potentials(1) Scalp distribution of CNV, difference wave P20-50 and Novelty P3a in normal controlTwelve channels of EEG (F3, Fz, F4, C3, Cz, C4, P3, Pz, P4, O1, Oz, O2) were divided four electrode sites including frontal region ( F3, Fz, F4),central region (C3, Cz, C4),parietal region (P3, Pz, P4) and occipital region (O1, Oz, O2). ANOVA results indicated a significant difference in CNV average amplitude across four electrode sites (F(3,57)=8.11,P<0.01). Average amplitude of central region is highest (16.83±2.89μv ) (SNK, P<0.05). No significant differences in latency variation across electrode zones were observed (P>0.05).ANOVA results indicated a significant difference in CNV areas across electrode sites (F (3,57)=43.66,P<0.01), CNV areas in central region (19966.40±1105.9μV * ms) was highest (SNK, P<0.05).ANOVA results indicated a significant difference in difference wave P20-50 amplitude across electrode sites (F (3,57)=5.33, P<0.01). Amplitude of occipital region which was lowest (1.23士1.30μv), No significant differences in latency variations across electrode zones were observed (SNK, P>0.05).ANOVA results indicated a significant difference in Novelty P3a amplitude across electrode sites (F(3,57)= 7.31,P<0.01), Novelty P3a amplitude in frontal-central region were higher than occipital–parietal region (SNK, P<0.05).No significant differences in latency across electrode zones were observed (F(3,57)=1.81, P>0.05).(2) Characteristics of ERPs component in patients with SIVCI.ANOVA results indicated a significant difference in CNV expectancy wave amplitude among SIVCIND group, SIVD group and NC groups (F(2,57) =34.34, P<0.01), Post hoc(SNK) analysis revealed that NC group(16.13±2.75μv) > SIVCIND group(9.98±4.10μv)> SIVD group(6.25±1.52μv) (P<0.05). ANOVA results indicated a significant difference in CNV expectancy wave areas among three groups(F(2,57)=48.75, P<0.01), Post hoc(SNK) analysis revealed that NC group(20058.87±1025.95μV*ms)> SIVCIND group(14848.10±3199.16μV*ms) > SIVD group(8474.00±3511.94μV*ms) (P<0.05).No significant differences in CNV expectancy wave latency among three groups were observed(F(2,57)=1.90,P>0.05).ANOVA results indicated a significant difference inP20-50 amplitude among three groups(F(2,55)=2.23,P<0.05). Post hoc(SNK) analysis revealed that SIVD group average amplitude was lower(1.21士0.45μv)than other two groups(P<0.05), and no significant differences were observed between SIVCIND group(2.63士1.28μv)and NC group(3.10士1.49μv) (P>0.05). ANOVA results indicated a significant difference in P20-50 latency among three groups(F(2,57)=8. 70,P<0.01), Post hoc(SNK) analysis revealed that NC group(77.47士28.22ms) < SIVCIND group(60.47士18.0ms)< SIVD group(46.73士13.93ms)(P<0.05).ANOVA results indicated a significant difference in Novelty P3a amplitude among three groups (F(2,55)=2.23,p<0.05).The Post hoc(SNK) analysis revealed that SIVD group has lower average amplitude(1.58士0.68μv)than other two groups(P<0.05), and no significant differences were observed between SIVCIND group(3.37士1.20)and NC group(3.69士1.41μv) (P>0.05). ANOVA results indicated a significant difference in Novelty P3a latency among three groups (F(2,55)=2.23,P<0.05). The Post Hoc(SNK) analysis revealed that SIVD group hasprolonged latency(331.13士37.26 ms)than other two groups(P<0.05), and no significant differences were observed between SIVCIND group(294.40士30.31 ms)and NC group(275.93士35.24 ms) (P>0.05).(3)Relationship between ERPs and neuropsychological data1) Relationship between CNV and CPTPearson correlation\Spearman rank correlation analysis revealed there were significant, positive correlations between EW latency and reaction time of CPT(R=0.748, P<0.01), there were no significant relationships between CPT ommision rate and EW latency(R=0.22, P>0.05),amplitude (R=-0.191, P>0.05), there were significant, negative correlations between EW area and reaction time of CPT(R=-0.718, P<0.01), ommision rate of CPT(R=-0.829, P<0.01), EW amplitude and reaction time of CPT(R=-0.616, P<0.01). Correlation analysis revealed EW area had a good correlation with CPT.2) Relationship between difference wave P20-50 and Stroop testPearson correlation\Spearman rank correlation analysis revealed there were significant, positive correlations between P20-50 latency and interfered effect of reaction time in stroop test(R=0.289, P<0.05), P20-50 latency and interfered effect of error rate(R=0.289, P<0.05). P20-50 amplitude correlated positively with interfered effect of reaction time in stroop test(R=--0.249, P<0.05)and had no correlation with interfered effect of error rate(R=-0.213,P>0.05). Correlation analysis revealed P20-50 latency had a good correlation with stroop test.3) Relationship between Novelty P3a and Dual taskPearson correlation\Spearman rank correlation analysis revealed dual task time difference correlated positively with Novelty P3a latency(R=0.38, P<0.01), and correlated negatively with Novelty P3a amplitude(R=--0.48,P<0.01). Correlation analysis revealed Novelty P3a latency had a good correlation with dual task.4. Brain electrical source analysis of ERPs componentsA principal component analysis was performed on the grand wave of CNV innormal control in -1500ms--0 (S1)time window, which revealed one component explaining 98. 8% of the variance,dipole can be approximately located in the left prefrontal lobe( Talairach: x = -17.6, y =61.5, z =0.6).At the peak point of dipole activity, the configuration can successfully explain the data in the time interview,and have a smallest residual variance(11. 39%).A principal component analysis was performed on the grand wave of P20-50 in normal control in 0-100ms time interval, this which revealed two component explaining 98. 0% of the variance, dipole1can be approximately located in the right superior temporal gyrus (Talairach: x = 22. 0,y = -7.4,z = 16.2)) ,dipole 2 can be approximately located in the right orbitofrontal cortex (Talairach:x = 20.0, y = 21.2,z = 28. 4).At the peak point of dipole activity, the configuration can successfully explain the data in the time window, and have a smallest residualvariance(10. 29%).A principal component analysis was performed on the grand wave of Novelty P3a in 150-350ms time window, which revealed two components explaining 98. 1% of the variance, dipole1can be approximately located in the middle of prefrontal lobe ( Talairach:x =9.0, y =27.4,z =8.9), dipole2 can be approximately located in the medianpart of anterior temporal lobe near the median line( Talairach: x =-2.8,y =3.4, z =6.8).At the peak point of dipole activity, the configuration can successfully explain the data in the time window, and have a smallest residual variance(9. 39%).5. Analysis of cortical current source density of ERPsIn normal control, CSD mapping of CNV revealed current density were intensive in bilateral (especially right )superior frontal lobe,bilateral parietal lobe were also activated. In SIVCI group, current density of right parietal lobe and right frontal lobe decreased obviously, right temporal region and central region activated at different degree. The CSD results demonstrated bilateral frontal lobe and parietal lobe participated in sustained attention information processing in physiological condition, when attention dipole source and neurocircuitry was damaged, temporal region and central region may participate in information processing. In normal control, CSD mapping of P20-50 revealed current density were intensive in bilateral temporal lobe, bilateral anterior frontal lobe and left parietal lobe were also activated. in SIVCI group, current density of right temporal lobe and bilateral frontal lobe decreased obviously, occipital region and central region were activated at different degree. The CSD results demonstrated bilateral temporal lobe and frontal lobe participated in selected attention information processing in physiological condition, when dipole source of attentional ERPs and neurocircuitry damaged, occipital region and central region may participate in information processing.In normal control, CSD mapping of Novelty P3a revealed current density were intensive in left superior frontal lobe and right frontal lobe ,left superior lobe and right parietal lobe were also activated, current density was feeble in occipital region .In SIVCI group, current density of frontal lobe decreased obviously, occipital region and left superior lobe activated obviously. The CSD results demonstrated bilateral frontal lobe may be principle cortical function zone of divided attention, when attention dipole source and neurocircuitry was damaged, occipital region and central region may participate in information processing.Conclusion1. SIVCI patients had obvious disorders in general assessment of cognitive function. Executive function, attention and delayed memory were predominant in cognitive impairment of SIVCIND patients, and SIVD patients had obvious cognitive impairment in executive function, attention, delayed memory,abstract and orientation, but no cognitive disorder in naming and verbalization .2.The results of computer-assisted test [CPT(assessing sustained attention function), stroop test(assessing selected attention function)]and dual task(assessing scattered attention.) revealed SIVCIND patients had predominance in sustained attention impairment completely and selective attention impairment partly, SIVD patients had general, obvious disorders in sustained attention, selective attention and divided attention.3.Event related potential P20-50,Novelty P3a and CNV evoked by dichotic listening, novelty stimulus Oddball mode and order-command signal two-stimulus paradigm respectively correlated with CPT, stroop test and dual task, and may be neuroelectrophysiological assistant indeces for assessing attention impairment of patients with SIVCI. Especially EW area, P20-50 latency and Novelty P3a latency may be more accurate to assess impairment of sustained attention, selective attention and divided attention.4.SIVD patients had widely abnormal expectancy wave, P20-50 and Novelty P3a, while only amplitude and area of Expectancy wave, P20-50 latency were abnormal in SIVCIND patients, which indicated expectancy wave, P20-50 latency may be more sensitive to assess attention impairment in earlier period of VCI.5. CNV dipole can be approximately located in the left prefrontal lobe( Talairach: x =-17.6,y =61.5,z =0.6). P20-50 dipole1 can be approximately located in the right superior temporal gyrus (Talairach: x = 22. 0, y = -7.4, z = 16.2), dipole 2 can be approximately located in the right frontal cortex (Talairach:x = 20.0, y = 21.2, z = 28. 4). Novelty P3a dipole1can be approximately located in the middle of prefrontal lobe ( Talairach: x =9.0, y =27.4, z =8.9), dipole 2 can be approximately located in the median part of anterior temporal lobe near the median line( Talairach: x =-2.8, y =3.4, z =6.8).6. Frontal-subcortical attentive circuits were disrupted by lacunar infarcts or deep white matter changes in SIVCI patients, and dipole resource of ERPs attention components were influenced, cortical resource of second domain may be activated and participated in attention information process . |
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