Event-related potentials in patients with multiple lacunar infarcts.

We studied event-related potentials (ERPs) occurring in response to attended and unattended stimuli in 31 patients with multiple lacunar infarcts. ERPs were recorded during the performance of visual discrimination tasks using three kinds of stimuli. Each component of P300 response to infrequent nontarget stimuli and P300 response to infrequent target stimuli was defined as non-target P3 or target P3. The non-target P3 latency in patients with multiple lacunar infarcts was significantly longer than in 15 age-equivalent normal subjects, while no significant differences could be found in target P3 latency between patients and normal subjects. From the controlled/automatic standpoint these results suggest that multiple lacunar infarcts are related to impairment of automatic processing reflected by non-target P3, although controlled processing reflected by target P3, is less impaired.     

Visual Event-Related Potentials in Cirrhotic Patients Without Overt Encephalopathy: The Effects of Flumazenil

The P300 complex was derived from the electroencephalogram (EEG) as subjects mentally counted infrequent large checkerboard visual stimuli, presented randomly among frequent small checkerboard stimuli. Use of low contrast (10%) stimuli and four midline scalp electrodes, facilitated separation of cognitive and sensory components and enabled the P300 complex to be resolved into three distinct components—N200, P3a, and P3b. In 20 healthy adult subjects normative data were established and the P3a and P3b components were shown to depend on cognitive function. In 19 age-matched cirrhotic patients without overt hepatic encephalopathy (HE) the EEG and visual evoked potentials (VEPs) were normal, but latencies of P3a and/or P3b were prolonged in 9. Prolonged latencies were not associated with an abnormal number connection test. Ten additional age-matched cirrhotic patients without overt HE, who were alcohol, drug, and caffeine free, were randomized to receive flumazenil (1 mg) and placebo intravenously, double-blind. After flumazenil or placebo, latencies of P3a and P3b and psychometric test results did not change significantly. These findings suggest that in cirrhotic patients without overt HE (i) impaired cognitive sensory function may occur in the absence of abnormalities of a standard psychometric test, the EEG, or VEPs, and (ii) increased latencies of P3a and P3b may constitute a component of subclinical HE, which is not mediated by increased brain levels of central benzodiazepine receptor agonist ligands.     

Visual evoked potentials in Alzheimer's and Parkinson disease]

Harding et al. suggested at first that an increase of P2 latency in flash VEP without an increase of P2 latency in pattern reversal VEP may be a diagnostic marker of Alzheimer's disease. Up to now there is no convincing evidence for this hypothesis. The purpose of the present study was to examine this hypotheses in an extended group of patients with Alzheimer's disease (n = 36). In addition, a group of patients with Parkinson's disease (n = 8) without dementia syndrome and a group of healthy elderly controls (n = 46) was investigated in order to determine the sensitivity and specificity of these VEP parameters. The results confirmed significant group differences between patients with Alzheimer's disease and healthy controls concerning the increase of Flash P2 latency and unchanged latency of P2 in the pattern reversal VEP. No significant correlations were found between duration of illness and mental test scores. The group differences of P2 latency in the flash VEP for patients with Parkinson's disease and healthy controls were also significant. Therefore, the increase of flash P2 latency in VEP does not seem to be specific for Alzheimer's disease nor for dementia syndrome. The pathological mechanism causing the flash P2 latency increase in a remarkable number of neuropsychiatric patients should be elucidated in further experimental investigations.     

Alzheimer's dementia and binding to alpha 2 adrenoreceptors in platelets

Seventy-five patients with probable Alzheimer's disease were screened for binding of alpha 2 receptors (A2R) to their platelet membranes; the results were compared with 51 age- and sex-matched controls. Receptor binding assays were performed using [3H] Yohimbine as the radioligand. The results showed a higher binding capacity in the demented population as compared to the control group (2.18 +/- 0.15 fmol/mg protein, as compared to 1.73 +/- 0.13, P less than 0.03). This increased binding to platelets in the demented patients was more prominent in demented females: 34% higher binding as compared with female controls (2.06 +/- 0.5 vs 1.54 +/- 0.04). The difference between demented and normal males was less (2.34 +/- 0.05 vs 1.88 +/- 0.05). The results indicate an involvement of the A2R system, either primarily or secondarily, in the disease process. Since there is an overlap between results from the patients with Alzheimer's disease and the normal subjects, A2R may serve as only a supportive marker for Alzheimer's disease.     

Relationship between the P300 auditory event-related potential and automated psychometric tests

Event-related potentials particularly the P3 component have been noted to be abnormal in illnesses affecting cognitive processes, such as dementia. The relationship between the P3 latency and objective tests of mental function in patients with Alzheimer's disease and vascular dementia has been studied. A significant correlation was demonstrated between P3 latency and automated psychometric tests in patients with Alzheimer's disease.     

Correlation of visual evoked potentials with dementia in Parkinson's disease]

There has been some debate regarding abnormalities in visual evoked potentials (VEP) in Parkinson's disease (PD). To elucidate the mechanism causing abnormal VEP, we investigated the relationship between VEP and mental function in PD patients. Pattern reversal VEP was recorded in PD patients (n = 27) and age-matched control subjects (n = 14). PD patients consisted of two subgroups; PD without dementia (nD-PD; n = 17) and PD with dementia (D-PD; n = 10). Dementia was evaluated according to the criteria for dementia assigned in DSM III-R, and mental faculties were estimated by using the mini-mental state examination (MMSE). In pattern VEP recordings, P100 latency and amplitude were measured for each eye stimulated. No patient or control subject had impairment of corrected visual acuity or ophthalmological disease. There was no significant difference in age among the three groups (D-PD, nD-PD and control subjects). D-PD patients showed significantly prolonged P100 latency compared to nD-PD patients and control subjects (p less than 0.05). With respect to P100 amplitude, no significant difference was shown among the three groups. In PD patients, there was a rough correlation between P100 latency and MMSE score. No correlation was found between P100 amplitude and MMSE score. In control subjects, P100 latency did not correlate with advancing age. In PD patients, nD-PD patients showed a significant correlation between P100 latency and age, whereas D-PD patients presented no correlation. Abnormal VEP in PD has been mostly ascribed to dopaminergic deficiency in the retina.(ABSTRACT TRUNCATED AT 250 WORDS)     

Pudendus-SSEP in der Diagnostik anorektaler Funktionsstörungen

Electrophysiological examinations in differential diagnosis of anorectal functional disorders comprise electromyogram of the pelvic floor, pudendal nerve terminal motor latency (PNTML) and evaluation of cortical latency of P 40 (pudendal SSEP). Pudendal SSEP usually is done via penile stimulation, since it is technically easier to carry out than perianal stimulation. In our study we compared latencies of P 40 in penile and perianal pudendal-SSEP. We examined 40 subjects aged 34 to 72 years (mean 52.4 years) without any manifestation of a neurological, urological or proctological disease. The stimulus was administered using penile ring electrodes at the base of the penis and the penile shaft as well as a perianal surface electrode applied at right and left lateral position. Cortical latencies were evoked using the averaging method from 500 stimuli. Cortical latencies of P 40 after perianal stimulation (mean: 36.7 ms from the right, 36.9 from the left) on the average were 4.7 ms shorter than after penile stimulation (mean: 41.5 ms), a correlation to the age of the subjects was not seen. There was also only a low correlation between the latencies of penile and perianal responses within the subjects. In conclusion, our results underline the necessity of separate normal values for penile and perianal pudendal SSEP in the differential diagnosis of anorectal functional disorders. Especially when a lesion of the afferents is assumed, the evaluation of pudendal SSEP may provide valuable additional information in combination with the more common methods such as electromyogram of the anal sphincter and PNTML.     

The relationship between prior knowledge and face recognition memory in normal aging and Alzheimer's disease

Normal older adults (M = 66.1 years) and mildly demented patients with a presumptive diagnosis of Alzheimer's disease (M = 68.0 years) studied a series of dated and contemporary famous faces for purposes of later recognition. In conjunction with the recognition test, subjects were asked to indicate whether they perceived the faces as familiar on the basis of pre-experimental knowledge, and to select the correct name for each face in a four-alternative multiple-choice test. Results showed that both groups of subjects (a) perceived more dated than contemporary faces as familiar, and (b) performed better for dated than for contemporary faces in the name recognition task. This pattern of results indicates an advantage of dated over contemporary information as general knowledge for both groups of subjects. In the episodic face recognition task, normal older adults performed better for dated than for contemporary faces, whereas demented patients performed equally well for both types of faces. The overall pattern of outcome suggests that Alzheimer's disease is associated with a deficit in the ability to utilize task-relevant prior knowledge to enhance episodic remembering.     

Longitudinal P300 latency changes in Alzheimer's disease

A longitudinal study of the changes in latency of the P300 (P3) wave of the auditory event-related brain potential was undertaken in a group of 18 thoroughly screened and diagnosed possible and probable Alzheimer's disease (pAD) patients and 15 normal controls. On initial recording, P3 latency was significantly prolonged in the pAD group by more than 1.5 standard deviations (40 msec) beyond the normal group. Over the course of the next 3 years, the rate of increase in P3 latency was significantly greater for the patient group than for the controls. The rate of change in P3 latency may reflect accelerated senescence in Alzheimer's disease. Development of the auditory P300 as a marker of neurobiological processes in aging and dementia is discussed.     

Auditory Event-Related Potentials in Fetal Alcohol Syndrome and Down's Syndrome Children

Abnormal or borderline electroencephalograms are commonly observed in cases of gross mental retardation. However, fewer studies have focused on the use of event-related responses to aid in the differential diagnosis of developmental cognitive disorders. Fetal alcohol syndrome (FAS) and Down syndrome represent the most common known causes of mental retardation in the Western world. Although Down syndrome is easily diagnosed with a chromosome assay, FAS can be more difficult to diagnose since the diagnostic features are more subjectively based. The present study is the first to characterize auditory event-related potentials (ERPs) in children with FAS and contrast them to subjects with Down syndrome and controls. A passive auditory "oddball-plus-noise" paradigm was utilized to elicit ERPs. Parietal P300 latencies in response to the noise-burst stimuli for the FAS children were significantly longer, as were the P300s from all cortical sites in Down syndrome subjects in response to the both the infrequent tone and noise-burst stimuli when compared with the controls. Frontal P300s in Down syndrome children were significantly larger in amplitude compared to the controls and FAS children in response to the infrequent tone. A discriminant function analysis also revealed that these children could be correctly classified as being either Down syndrome, FAS, or normal controls using measures of latency and amplitude of the P300. These data suggest that an evaluation of ERP characteristics may provide a better understanding of the differences between FAS and Down syndrome children, and prove to be an aid in the early identification of children with FAS. These results demonstrate neurophysiological differences between FAS and Down syndrome, and suggest that P300 amplitude and latency data collected from a passive ERP task may be helpful in the discrimination of developmental cognitive disorders.     

Postural set for balance control is normal in Alzheimer's but not in Parkinson's disease

BACKGROUND: It has been suggested that patients with dementia of the Alzheimer type have abnormalities in the basal ganglia, and thus, may have similar sensorimotor problems as patients with basal ganglia degeneration from Parkinson's disease. Whether the similarity extends to balance control is unknown. One distinguishing feature of balance disorder in Parkinson's disease is difficulty with changing postural set in terms of adapting the amplitude of leg muscle activity as a function of support condition. We, therefore, tested whether patients with Alzheimer's disease without extrapyramidal signs would show a similar problem in changing postural set as patients with Parkinson's disease. METHODS: The ability to quickly change postural set was measured by comparing leg muscle activity under two conditions of support (free stance, versus grasping a frame, or sitting) during backward surface translations, during toes up surface rotations, and during voluntary rise to toes. Results were compared among 12 healthy adults, 8 nondemented Parkinson's patients on their usual dose of medication, and 11 Alzheimer patients without extrapyramidal signs. RESULTS: Subjects with Alzheimer's, but not Parkinson's, disease performed similarly to the healthy control subjects. They changed postural set immediately, by suppressing leg muscle activity to low levels when supported. Parkinson subjects did not change postural set immediately. They did not suppress the tibialis anterior in voluntary rise to toes when holding, nor the soleus in perturbed sitting as much as the healthy control and Alzheimer subjects in the first trial. Instead, the Parkinson subjects changed set more slowly, over repeated and consecutive trials in both protocols. The onset latencies of soleus responses to backward surface translations and perturbed sitting, as well as tibialis anterior responses to toes up rotations, were the same for all three groups. CONCLUSION: Alzheimer patients without extrapyramidal signs, unlike nondemented Parkinson's disease patients, have no difficulty in quickly changing postural set in response to altered support conditions. Our results, therefore, do not support the hypothesis that Parkinson's and uncomplicated Alzheimer's diseases share common postural set problems that may contribute to disordered balance control.     

Visual Event-Related Potentials in Cirrhotic Patients without Overt Encephalopathy

Ambulant patients with cirrhosis and no clinical evidence of encephalopathy were screened for impaired brain function by neuroelectrophysiological testing dependent on cognitive function. Infrequent large checkerboard visual stimuli were randomly interleaved with frequent small ones to elicit P300 event-related potentials (ERPs). Three ERP components, N200, P3a and P3b, were derived from the electroencephalogram (EEG) by computer averaging. The use of 10% contrast and a minimum of four precisely placed scalp electrodes were found to be necessary for optimal separation of ERPs from sensory evoked potentials. Visual ERPs, onset/offset and pattern-reversal visual evoked potentials (VEPs), the spontaneous EEG and the time taken to complete a standard number connection test (NCT) were obtained from 20 normal adult subjects and 19 age-matched patients with histologically-confirmed cirrhosis and no clinical evidence of encephalopathy. The latencies and amplitudes of evoked potentials and the alpha rhythm of the EEG were determined. In 6 of the 19 patients the latencies of P3a and/or P3b exceeded the corresponding mean for controls+2 standard deviations of that mean. In 4 other patients the NCT was prolonged. In all of the patients the N200, VEPs and alpha rhythm of the EEG were normal. In conclusion: (i) Optimal isolation of ERPs is critically dependent on stimulus contrast and electrode placement; (ii) ERPs appear to be more sensitive than primary sensory evoked potentials or the EEG in detecting impaired brain neuroelectrophysiological function; and (iii) Cirrhotic patients without overt encephalopathy in whom P3a and/or P3b latencies are prolonged may have subclinical hepatic encephalopathy.     

Latency differences of visual evoked potentials in binocular and monocular checkerboard stimulation as well as age and sex dependence

Pattern reversal evoked potentials (VEPs) have been recorded in 100 normal subjects with an average age of 37.6 years (range 11-69). We found significantly shorter latencies of the P 100 for binocular stimulation compared to monocular stimulation. Women under 50 years showed shorter latencies than men for both binocular and monocular stimulation. Men showed no significant latency dependence of age. However, women had a significant latency prolongation above an age of 50 years, indicating a sex specific influence on latencies.     

The impact of age-related changes in event-related P300 potentials on detecting early cognitive dysfunction

Event-related P300 potentials that closely reflect cognitive brain functions show significant age-related latency prolongations. This aging-P300 interaction can best be approximated by third-order polynomial regressions. To delineate the clinical impact this special kind of regression function may have on detecting early cognitive dysfunction, we applied visual P300 potential data of healthy subjects (n = 344; age range, 18-98 years) to nondemented patients with either (i) chronic liver disease (n = 104; age range, 19-74 years) or (ii) cerebral arteriosclerosis (n = 80; age range, 38-80 years). As compared with linear regressions, third-order polynomial regressions for the age-related changes in P300 potential latencies showed a smaller latency increase during middle age, with an accelerating latency prolongation from age 60 onward. In patients with liver cirrhosis, third-order polynomial regressions yielded a rate of abnormal P300 potential latencies exceeding that of linear regressions absolutely by 17-21%, and relatively by 67-71%. Although the rate of P300 abnormalities was much lower in the CAD patients with either regression model, the relative increase in P300 abnormalities due to third-order polynomial regressions was 40-112.5%. In conclusion, normal data for the latencies of P300 potentials based on third-order polynomial regressions result in a higher sensitivity of P300 potentials for detecting early cognitive dysfunction. This gain in diagnostically important information is not offset by a loss in specificity, and may depend on the kind as well as stage of the disease, the age distribution of the patients and the degree of the P300 potential abnormalities.     

Subclinical visual impairment in phenylketonuria. A neurophysiological study (VEP-P) with clinical, biochemical, and neuroradiological (MRI) correlations

During detailed visual function testing, pattern-reversal visual evoked potentials (VEP), generated by different spatial frequencies (3c/d, 1c/d and 0.6c/d) and visual contrasts (100% and 10%) were recorded in 21 adolescent and young adult phenylketonuric (PKU) patients (11 females and 10 males; mean age 14.8 years, range 9–22.8) on and off diet. In 14 of the 21 patients, disease had been detected at neonatal screening and in 7 later. Ten age-matched healthy subjects acted as controls. Recordings in more than 40% of eyes in the whole group and 30% of eyes in the screening subgroup showed a prolonged P100 latency. All visual pattern stimuli elicited a significantly longer P100 latency in PKU patients than in controls. VEP latencies to 3c/d, 1c/d and 1c/d with 10% contrast – but not to 0.6c/d – were longer in patients off diet than in patients on diet. No differences were found between VEP latencies in early- and later-detected subjects. To study the link between biochemical variables and VEP latencies, we envisaged either a linear relationship between recent exposure to phenylalanine (Phe) and VEP abnormalities or a threshold model considering phenylalanine (Phe) concentrations among the factors influencing VEP latencies. The correlation analysis detected an association between plasma Phe concentrations and abnormal VEP latencies, predicting that plasma Phe concentrations >901 mol/L would prolong VEP latencies to 1c/d; concentrations >879 mol/L would prolong latencies to 3c/d; and concentrations >898 mol/L would prolong latencies to 1c/d with 10% contrast. Finally, our data confirmed a lack of correlation between white-matter abnormalities on MRI and abnormal VEP latencies. Our findings suggest that in young patients with PKU, prolonged, late exposure to high plasma Phe concentrations induces subclinical visual dysfunction. Although our findings do not allow us to specify the origin of visual system changes in PKU, they favour impairment of the retinal loop as the responsible mechanism.     

Specific saccade deficits in patients with Alzheimer’s disease at mild to moderate stage and in patients with amnestic mild cognitive impairment

Saccadic impairment in Alzheimer’s disease (AD) was found in horizontal saccades. The present study extends investigation to vertical saccades in a large number of subjects, including AD and amnestic mild cognitive impairment (aMCI). We examined both horizontal and vertical saccades in 30 healthy elderly, 18 aMCI, and 25 AD. Two tasks were used: gap (fixation target extinguishes prior to target onset) and overlap (fixation stays on after target onset). Eye movements were recorded with the Eyeseecam system. (1) Robust gap effect (shorter latencies in gap than in overlap) exists for AD and aMCI patients as for healthy elderly; (2) abnormal long latency of saccades in gap and overlap tasks for AD relative to healthy elderly and aMCI patients; (3) longer latency for aMCI patients than for healthy elderly for the overlap task; (4) significant correlation between scores of Mini-Mental State Examination (MMSE) and latencies of saccades considering the AD group only; (5) higher coefficient of variation in latency for AD patients than for healthy elderly and for aMCI patients; (6) variability of accuracy and speed is abnormally higher in AD patients than in aMCI and healthy elderly. Abnormalities of latency and latency–accuracy–speed variability reflect deficits of cerebral areas involved in the triggering and execution of saccades; latency of saccades can be used as follow-up test for aMCI and AD patients with its significant correlation with the changes of MMSE scores.     

The effects of age on auditory event-related potentials.

The effects of age on event-related potentials (ERPs) elicited during a two-tone discrimination ("oddball") task were examined in 97 normal subjects aged from 17-80 years. Strong relationships were found between age and the latencies of the later ERP components N200 and P300. Furthermore the correlation between age and N200 latency at Pz was marginally higher than that of age and P300 latency. For the entire sample, the increase in P300 latency as a function of age was best described at Cz and Pz by linear regression equations. However, a segmented line model better described the P300/age relationship at Fz--the increase in P300 latency with age in subjects over 61 was five times that of subjects younger than 61 years. In this study the task required button-press identification of the targets--the significance of increased age and a delay in N200 latency is discussed with reference to the possibility of N200 latency indexing the speed of cognitive processing.     

高血压伴腔隙性脑梗死病人的智能评价

目的 对高血压伴腔隙性脑梗死病人进行智能评价。方法 分别对43例高血压伴腔隙性脑梗死(腔梗)病人和34例正常人进行Hachinski缺血指数量表(HIS、Rosen)评分及智能评定(HDS)。结果(1)以正常人为对照,原发性高血压伴腔隙性脑梗死患者的 HIS,Rosen显著升高(分别为 P<0.05,P<0.01),HDS显著降低(P<0.001)。(2)原发性高血压Ⅱ级组的HDS显著低于原发性高血压Ⅰ级组(P<0.01)。原发性高血压患者的平均血压与Rosen呈显著正相关(r=0.318,P<0.05)。(3)血粘度升高患者的HDS显著低于血粘度正常者(P<0.05)。结论 Hachinski缺血指数量表(HIS、Rosen)评分及智能评定(HDS)可作为高血压伴腔隙性脑梗死病人的长期监测指标之一。     

Visual field limitation in the patient with dementia of the Alzheimer's type

This paper investigates the existence of a visual field limitation and its effect on the advanced Alzheimer's patient. The data presented was obtained by testing 12 Alzheimer's and 12 control patients. The control patients were demented from causes secondary to reasons other than Alzheimer's disease. The results indicated that patients demented due to Alzheimer's have visual field losses significantly greater than other demented patients. This significant visual loss is of importance in assisting in differential diagnosis, performing patient cares, and planning patient environments.     

How common is dementia in Parkinson's disease?

Current estimates suggest that about one in three patients with Parkinson's disease will become demented. Critical review of the studies on which this conclusion is based indicate that this figure is inflated. Errors in separating idiopathic Parkinson's disease from other causes of the akinetic-rigid syndrome, in differentiating dementia from confusional states, depression, and even normal ageing, and in defining and assessing dementia itself may have led to overestimation of the prevalence. A more conservative estimate is that one in five patients with Parkinson's disease is demented, but this assertion needs to be put to rigorous examination.