Dysfunction Of Cognition In Patients With Hypertension By Event-related Potentials

Background Hypertension is one of the most common disease in old people, and even theimportant risk factor for the onset of strokes. It is universally acknowledged that stroke isassociated with cognitive dysfunction and dementia. However, a majority of studies havefound that before the onset of cerebral apoplexy, cognitive function in patients withhypertension has been damaged to a certain extent. Cognitive function is the importantcontent of higher cortical brain, including memory, attention, calculation, time and spatialorientation, executive capacity, language comprehension and expression, application, and soon. Hence, cognitive function is of great significance to people’s life, study and work.At present our country about200million patients with hypertension, every10adults have2people, accounting for about20%of the world’s total number of high blood pressure.Therefore, the effective control of blood pressure, then improving cognitive function inpatients with hypertension is critical. Cognitive dysfunction in patients with hypertension hasits uniqueness, main show is attention disorders, memory disorders, disorientation, executivedysfunction and communication disorders, etc., especially in the significant impact onmemory and attention.Event-related potentials (ERPs) was produced in the late1950s, has become a uniquemethod for the research of neuroscience, and widely used in cognitive neuroscience andclinical research. What’s more, it has been hailed as a "window on advanced functions of thebrain", providing a more sensitive and objective indicators to observe brain cognitive function. Using the event-related potentials(ERPs) to investigate the characteristics and neuralmechanisms of cognition dysfunction in patients with hypertension.Experiment1Dysfunction of attention in patients with hypertension by event-relatedpotentialsObjective To investigate the characteristics and neural mechanisms of visual attentiondysfunction in patients with hypertension.Methods Visual oddball pattern was adopted to analysis P3a and P3b components of25essential hypertension patients and25normotensives. T he standard st imulus was smaller dis,probability80%; target st imulus was larger disk, proba bility10%; novel st imulus w ascheckerboard, probability10%. Subjects were asked to count larger disk and ignore otherstimuli. In addition, all the participants were submitted to cognitive assessment byMini-Mental-State-Examination (MMSE).Results Novelty stimulus: The mean amplitude of N2[(1.46±1.16)μV] in hypertensivepatients [(1.46±1.16)μV] was decreased than normal controls [(-2.28±1.16)μV,(P<0.05)],particularly at forehead-central sites (P<0.05). In addition, the amplitude of P3a ofhypertensive patients [(6.37±1.00)μV] was different from normal controls [(7.10±1.00)μV],but there was no statistical significance (P>0.05). The latency of visual P3a was significantlylonger in hypertensive group [(430.86±8.25)ms] than in control group [(401.03±8.25)ms,P>0.05)]; Target stimulus: Compared to contral group [(6.78±0.91)μV], visual P3b amplitudein hypertensive group [(4.09±0.91)μV] was significantly declined (P<0.05). Besides, thelatency of visual P3b of hypertensive patients [(440.75±6.46)ms] was different from normalcontrols [(436.97±6.46)ms], but there was no statistical significance (P>0.05); Compared withcontrol group (27.33±1.23), the MMSE score of patients with hypertension (24.58±2.43) wasdecreased (P<0.05). The amplitude of visual P3b was positively correlated with MMSEscores in parietal region (r=0.51, P<0.05).Conclusions The ability of visual involuntary attention and voluntary attention wasdamaged in patients with hypertension, what’s more, the impact degree of hypertension ontwo kinds of attention and the neural mechanisms were different. Moreover, there was asignificant positive correlation between the amplitude of visual P3b and MMSE, whichprompted that visual P3b for clinical early assessment of attention in patients with hypertension provided more objective neurophysiological basis. Experiment2Impairment in pre-attentive processing among patients with hypertensionrevealed by visual mismatch negativityObjective To investigate the characteristics and neural mechanisms of pre-attentiveinformation processing dysfunction in patients with hypertension.Methods We compared visual mismatch negativity (vMMN) between25hypertensivepatients and25aged-matched healthy controls, which was elicited by the change of visualduration randomly presented on both peripheral visual fields. In addition, the global cognitivefunction for all participants was assessed with Mini-Mental State Examination (MMSE).Results Compared with control group (27.33±1.23), the MMSE score of patients withhypertension (24.58±2.43) was decreased (P<0.05). The vMMN in deviant-standardcomparison was observed at occipital-temporal regions. Compared with normal healthycontrols, the amplitude of vMMN was significantly decreased in hypertensive patients (P <0.05). Meanwhile, the vMMN peak latency was delayed in the hypertensive group (P <0.05).But, there was no significant correlation between the mean amplitude of vMMN and MMSEin hypertensive individuals.Conclusions These data indicate dysfunction of automatically change detection processingin patients with hypertension.