Dissociation between recognition of familiar scenes and of faces in patients with very mild Alzheimer disease: An event-related potential study

ObjectiveWe used event-related potentials (ERPs) to examine the recognition of familiar faces and scenes in patients with very mild Alzheimer disease (VMAD).MethodsTwo types of stimuli, FACEs and SCENEs, and two versions of each type, FAMILIAR and NOVEL, were presented. Three ERPs were compared between VMAD and normal control (NC): (1) P100 to examine basic visual processing, (2) N170 structural encoding, and (3) N250r familiarity.ResultsA prominent N170 was elicited by FACEs in P8 and the largest N170 by SCENEs in P3 and P4. Participants had more errors when judging pictures of SCENEs as familiar or not than that of FACEs. In P3 and P4, NC produced larger N170 than VMAD. From N250r in F3, the familiarity effect was absent in VMAD when familiar scenes were provided. This deficit was not seen in processing familiar faces.ConclusionsThis study shows that different neural regions are responsible for the early visual processing in the structural encoding of scenes and faces. The pattern of P100 and that of N170 suggest that VMAD patients maintain basic visual processing and structural encoding abilities. A conflict between behavioral and physiological responses may play a role in VMAD patients’ risk of getting lost in familiar environments.SignificanceScene recognition is impaired earlier than face recognition in the course of Alzheimer disease.     

Spatiotemporal properties modulate intermodal influences on early somatosenory processing during sensory-guided movement

ObjectivesSomatosensory evoked potentials (SEPs) were used to (1) investigate intermodal influences upon somatosensory processing in primary somatosensory cortex (S1), (2) determine the influence of spatiotemporal relationships between bimodal stimuli in S1 and (3) observe behavioral changes associated with intermodal modulation.MethodsMedian nerve SEPs were elicited from electrical stimulation and recorded from scalp electrodes during continuous tracking of one of two simultaneously presented stimuli (vibrotactile/visual). In Experiment 1, spatial relationship was manipulated by placing the visual stimulus in the same/opposite hemi-field as the vibrotactile stimulus. In Experiment 2, temporal synchrony was manipulated by altering the pattern of intensity changes such that they followed identical/different patterns.ResultsFor Experiment 1, greater spatial relationship reduced the amplitude of the P27 SEP component whereas in Experiment 2 greater temporal synchrony increased the amplitude of the P27 SEP component. Temporal synchrony increased P50 amplitude only during vibrotactile tracking. Tracking performance mirrored early SEP amplitude changes. In Experiment 2, task-relevance was associated with increased N140 amplitude.ConclusionsThe changes in P27 amplitude observed in Experiments 1 and 2 reflect an intermodal mechanism of somatosensory gating dependent upon spatiotemporal properties of bimodal stimulation whereas the P50 reflects multisensory aspects of somatosensory processing. Changes in behavior may reflect the importance of these early influences to sensorimotor transformations.SignificanceModulation of the P27 component reflects an intermodal sensory gating in somatosensory processing.     

Sparing of attentional relative to mnemonic function in a subgroup of patients with dementia of the Alzheimer type

Patients with dementia of the Alzheimer type (DAT) received two tests of visual selective attention, together with tests of spatial and visual recognition memory and visuospatial conditional learning previously used to show deficits early in the course of DAT. One set of attentional tests compared visual discrimination learning along intra- and extra-dimensional shifts, using a "total change" design. In the 12 DAT patients capable of attempting the extra-dimensional shift (subgroup 1), performance was equivalent to that of controls. This subgroup was also unimpaired at simple and compound discrimination learning and reversal and an intra-dimensional shift. They were as accurate as controls on a visual search task requiring matching of stimuli on two dimensions with variable numbers of alternatives, but were significantly impaired in the tests of recognition memory and learning. By contrast, the other 13 patients showed marked impairments in the attentional tasks. This subgroup was also significantly worse than subgroup 1 in performance on the visual recognition and conditional learning tasks, and showed greater severity on most of the clinical ratings of dementia. The sparing of attentional shifting in patients early in the course of DAT is contrasted with the impairments previously described in patients with Parkinson's disease with only mild or absent memory loss. The implications of this double dissociation of deficits for understanding the neural bases of the cognitive deficits in these two neurodegenerative diseases are discussed and their significance for the staging of DAT is considered.     

多巴胺转运蛋白基因可变数目重复序列多态性对健康成人认知电位冲突信息处理过程的影响

背景 多巴胺转运蛋白基因的一段可变数目重复序列多态性与基因的表达及转运蛋白的结合能力有关从而影响细胞外多巴胺浓度。目前关于该基因多态性对认知功能的影响的研究很少且结论很不一致。事件相关电位技术具有较高的时间分辨率, 是研究认知功能的重要手段。其中负波N270被认为是反应人脑处理冲突信息的电活动。 目的 通过比较两组具有不同多巴胺转运蛋白基因可变数目重复序列多态性的健康成人的事件相关电位来了解该多态性对大脑处理冲突信息的影响。 设计,时间,地点 DNA分析于2007年7月至2007年10月在协和医科大学分子生物学国家实验室完成。ERP测试于2007年11月至2008年4月在首都医科大学神经内科完成。 材料 Taq DNA 聚合酶购于上海博彩生物科技有限公司。ERP的采集和分析采用美国NeuroScan公司的多导脑电诱发工作站4.0版本。 方法 162名健康成人参加了多巴胺转运蛋白基因多态性的筛查,最后28人（10/10 基因型14人;10/9 基因型14人）参加了ERP测试。在ERP测试中受试者完成一个视觉比较任务：在匹配状态下一对刺激图中的第二个刺激(S2)与第一个刺激(S1)完全相同;在冲突状态下第二个刺激(S2)与第一个刺激(S1)完全不同。要求受试者在匹配状态下按一个键,在冲突状态下按另一个键。ERP在受试者进行比较任务时同步记录。 主要结果测量指标 行为学数据（反应时间和正确率）和ERP数据（ERP成分的波幅和潜伏期）。 结果 在匹配状态中,S2诱发出P300。在冲突状态中,在P300前S2还诱发出另一成分N270。无论是在匹配还是冲突状态,10/10基因型受试者的反应时间均显著快于10/9基因型受试者。10/10基因型受试者的N270潜伏期显著短于10/9基因型受试者。 结论 多巴胺转运蛋白基因可变数目重复序列多态性影响健康成人的冲突信息处理过程。     

Memory impairment and auditory evoked potential gating deficit in schizophrenia

Impaired sensory gating and memory function were reported in a study of 10 schizophrenic patients and 10 age- and sex-matched normal subjects. The P50 component of the auditory evoked potential was used as an index of gating. Explicit memory was tested with the Wechsler Memory Scale and implicit memory by artificial grammar learning. The schizophrenic patients showed deficits in both verbal paired associate and visual reproduction tasks. They demonstrated impaired implicit learning in color patterns but not letter strings. They also showed impaired P50 sensory gating. Three-dimensional brain mapping revealed a differential distribution of brain potentials in the processing of S1 and S2 at either P50 or N100 in both groups. However, the group difference was not statistically confirmed. In the controls, both implicit letter-string learning and explicit verbal paired associates were positively correlated with N100 gating, suggesting an association of the early attentive component with lexicons. In the schizophrenic patients, color-pattern implicit learning was positively correlated with P50 gating. The modality-specific impairment of implicit learning in schizophrenia may reflect a failure of adaptive filtering on the flooding input from color patterns.     

Early sensory–perceptual processing deficits for affectively valenced inputs are more pronounced in schizophrenia patients with a history of violence than in their non-violent peers

Individuals with schizophrenia are more prone to violent behaviors than the general population. It is increasingly recognized that processing of emotionally valenced stimuli is impaired in schizophrenia, a deficit that may play a role in aggressive behavior. Our goal was to establish whether patients with a history of violence would show more severe deficits in processing emotionally valenced inputs than non-violent patients. Using event-related potentials, we measured how early during processing of emotional valence, evidence of aberrant function was observed. A total of 42 schizophrenia patients (21 with history of violence; 21 without) and 28 healthy controls were tested. Participants performed an inhibitory control task, making speeded responses to pictorial stimuli. Pictures occasionally repeated twice and participants withheld responses to these repeats. Valenced pictures from the International Affective Picture System were presented. Results in controls showed modulations during the earliest phases of sensory processing (<100 ms) for negatively valenced pictures. A cascade of modulations ensued, involving sensory and perceptual processing stages. In contrast, neither schizophrenia group showed early differentiation. Non-violent patients showed earliest modulations beginning ∼150 ms. For violent patients, however, earliest modulations were further delayed and highly attenuated. The current study reveals sensory–perceptual processing dysfunction for negatively valenced inputs, which is particularly pronounced in aggressive patients.     

Event-related potential in Alzheimer disease

Auditory event - related potentials were studied in 20 patients with SDAT and 20 age and sex matched normal controls. Patients with SDAT showed prolonged latencies of N200 and P300 components. The mean amplitudes of N200 and P300 were lower in the SDAT group. This reflects the impairment of the speed of neural processing in patients with SDAT. There were no significant correlations of the progression of P300 latencies from mild to severe dementia according to global dementia scales.     

Early visual processing deficits in schizophrenia: impaired P1 generation revealed by high-density electrical mapping.

Integrity of early visual sensory processing in schizophrenia was assessed using the well characterized P1 and N1 components of the visual evoked potential (VEP) as our dependent measures. VEPs were recorded in response to successively less fragmented line drawings of common objects. P1 amplitudes were significantly reduced across all stimulus conditions for patients versus controls. Further, this decrement was relatively greater at parieto-occipital than occipito-temporal electrode sites. No differences in N1 amplitude were found. The finding of P1 deficits in patients, particularly over dorsal scalp, supports the view that schizophrenia is associated with impairment of early dorsal visual stream processing. On the other hand, the finding of normal N1 amplitudes in patients suggests that early stages of ventral stream processing may be relatively more intact. These results imply that the cognitive impairment seen in schizophrenia is not just due to deficits in higher order aspects of cognition but also encompasses significant deficits in early sensory processing.     

Differential relationships of impulsivity or antisocial symptoms on P50, N100, or P200 auditory sensory gating in controls and antisocial personality disorder

Limited information is available on the relationship between antisocial personality disorder (ASPD) and early filtering, or gating, of information, even though this could contribute to the repeatedly reported impairment in ASPD of higher-order information processing. In order to investigate early filtering in ASPD, we compared electrophysiological measures of auditory sensory gating assessed by the paired-click paradigm in males with ASPD (n = 37) to healthy controls (n = 28). Stimulus encoding was measured by P50, N100, and P200 auditory evoked potentials; auditory sensory gating (ASG) was measured by a reduction in amplitude of evoked potentials following click repetition. Effects were studied of co-existing past alcohol or drug use disorders, ASPD symptom counts, and trait impulsivity. Controls and ASPD did not differ in P50, N100, or P200 amplitude or ASG. Past alcohol or drug use disorders had no effect. In controls, impulsivity related to improved P50 and P200 gating. In ASPD, P50 or N100 gating was impaired with more symptoms or increased impulsivity, respectively, suggesting impaired early filtering of irrelevant information. In controls the relationship between P50 and P200 gating and impulsivity was reversed, suggesting better gating with higher impulsivity scores. This could reflect different roles of ASG in behavioral regulation in controls versus ASPD.     

Somatosensory evoked potentials,sensory nerve potentials and sensory nerve conduction in hereditary motor and sensory neuropathy type I

Summary Thirty-nine patients from six families with hereditary motor and sensory neuropathy type I and control subjects were included in this study. A neurological deficit score (NDS) was derived from a neurological examination and compared with neurophysiological test findings. Further, sensory nerve conduction velocities (SNCV) were compared with the motor nerve conduction velocities (MNCV). Five patients whom peaks of N11/N13 complex and N20 of the median nerve sensory evoked potential (SEP) could be recorded showed normal interpeak latency. The interpeak separation P14 N20 measured in six patients was normal. These findings point to the normal function of the central conductive pathways. Erb and cervical potentials of the median nerve SEP could be recorded in 10% and 12% of the patients, respectively. In contrast, about half of the patients showed a scalp N20, while in most of them no SNCV could be measured. In six patients far-field potential P14 of the median nerve SEP was the first detectable potential. Therefore, we argue in view of the anatomical structure of the thalamus, that the first generator for synchronizing and amplification of impulses is probably located in the thalamus. A third of the patients had a cortical sural nerve SEP, while no sural nerve potentials could be recorded. No association was found between the SEP findings and the NDS. There was an inverse correlation between median SNCV and the NDS, but no relationship between the former and sensory deficit alone. In 40% of the patients median SNCV and in 13% sural SNCV could be recorded and considered to be severely decreased. In contrast, the majority of the patients had mild to moderate sensory deficit. Furthermore, patients with measurable SNCVs had higher MNCVs and lower NDS than patients without measurable SNCVs.     

Cortical auditory dysfunction in benign rolandic epilepsy

Purpose: To evaluate cortical auditory function, including speech recognition, in children with benign rolandic epilepsy (BRE).
Methods: Fourteen children, seven patients with BRE and seven matched controls, underwent audiometric and behavioral testing, simultaneous EEG recordings, and auditory-evoked potential recordings with speech and tones. Speech recognition was tested under multiple listening conditions.
Results: All participants demonstrated normal speech recognition abilities in quiet, as well as normal peripheral and subcortical auditory function. BRE patients performed significantly worse than controls when speech recognition was tested under adverse listening conditions, including background noise. Five BRE patients who were impaired on two or more tests had centrotemporal spiking on awake EEG. There were no significant group differences in the latency or amplitude of early N100 cortical responses to speech or tones. Conversely, the mismatch negativity, a preattentive index of cortical processing that is elicited passively, was absent or prolonged for speech, but not tones, in BRE patients as compared to controls.
Discussion: Children with BRE demonstrated specific speech recognition impairments. Our evoked potential findings indicate that these behavioral impairments reflect dysfunction of nonprimary auditory cortex and cannot be attributed solely to attention difficulties. A possible association between auditory impairments and centrotemporal spiking (>1/min) on awake EEG was identified. The pattern of speech recognition impairments observed is a known risk factor for academic difficulties in school-age children. Our results underscore the importance of comprehensive auditory testing, using behavioral and electrophysiological measures, in children with BRE.     

Dysnomia in dementia and in stroke patients: different underlying cognitive deficits

The performance of 11 Alzheimer's (DAT) and 8 anomic aphasic stroke patients is contrasted with that of 32 normal elderly subjects on both the Boston Naming Test (BNT) and the Controlled Oral Word Association Test (COW), a letter-category verbal-fluency test. While both tests require phonological processing, only the BNT requires semantic processing (object recognition). Both DAT and anomic aphasic stroke patients were significantly impaired on the BNT, with mean z scores (based on the performance of the normals) of -4.08 and -2.57, respectively; the DAT patients were significantly farther from normal than were the anomic aphasics. Their relative levels of impairment on the COW were reversed: The anomic aphasics' performance (z = 1.79) was worse than that of the DATs (z = -0.66). This pattern of performance on the two tests is consistent with the hypothesis that impaired word finding reflects impaired processing mainly of semantic information for the DAT subjects, mainly of lexical-phonological information for the anomic aphasic subjects.     

Dissociation between knowledge of living and nonliving things in dementia of the Alzheimer type

Patients who survive herpes simplex encephalitis (HSE) sometimes present a category-specific disorder for living things. Since HSE specifically involves the temporolimbic structures of both hemispheres, these structures could play a critical role in processing and storing information about living things. If this were the case, a category-specific disorder for the same items should also be observed in the early stages of dementia of the Alzheimer type (DAT) as the temporolimbic structures are often severely affected in this condition. To test this hypothesis, we administered to 15 DAT patients and to 10 normal controls a confrontation-naming task and a verbal associates recognition task, with both living and nonliving items as stimuli. The hypothesis was confirmed, since DAT patients performed worse with living than with nonliving items, and scored worse than normal controls on the living but not the nonliving items.     

Functional MRI of facial emotion recognition deficits in schizophrenia and their electrophysiological correlates

Empirical evidence suggests impaired facial emotion recognition in schizophrenia. However, the nature of this deficit is the subject of ongoing research. The current study tested the hypothesis that a generalized deficit at an early stage of face-specific processing (i.e. putatively subserved by the fusiform gyrus) accounts for impaired facial emotion recognition in schizophrenia as opposed to the Negative Emotion-specific Deficit Model, which suggests impaired facial information processing at subsequent stages. Event-related potentials (ERPs) were recorded from 11 schizophrenia patients and 15 matched controls while performing a gender discrimination and a facial emotion recognition task. Significant reduction of the face-specific vertex positive potential (VPP) at a peak latency of 165 ms was confirmed in schizophrenia subjects whereas their early visual processing, as indexed by P1, was found to be intact. Attenuated VPP was found to correlate with subsequent P3 amplitude reduction and to predict accuracy when performing a facial emotion discrimination task. A subset of ten schizophrenia patients and ten matched healthy control subjects also performed similar tasks in the magnetic resonance imaging scanner. Patients showed reduced blood oxygenation level-dependent (BOLD) activation in the fusiform, inferior frontal, middle temporal and middle occipital gyrus as well as in the amygdala. Correlation analyses revealed that VPP and the subsequent P 3a ERP components predict fusiform gyrus BOLD activation. These results suggest that problems in facial affect recognition in schizophrenia may represent flow-on effects of a generalized deficit in early visual processing.     

Interpeak latency of auditory event-related potentials (P300) in senile depression and dementia of the Alzheimer type

Most studies on event-related potentials (ERP) in psychiatric illness or dementia have focused on the single-peak latency of ERP components. In the present study, not only peak latencies of ERP components (N1, P2, N2, and P3) but also interpeak latencies (IPL; N1-P2, P2-N2, and N2-P3) were analyzed using the auditory oddball task. Thirty-five senile depressed patients and 34 patients with dementia of the Alzheimer type (DAT) were compared to 39 age-matched healthy volunteers. The mean latencies of P2 and P3 were shorter in patients with senile depression than in controls. In DAT patients, the N2 and P3 latencies were longer. When the IPL was assessed, however, only the mean IPL of N1-P2 was shorter in patients with senile depression, while the P2-N2 IPL were longer in those with DAT. The IPL results suggest that in senile depression the early cognitive process is hastened and in DAT the middle process is disturbed. Based on these results, we conclude that IPL of the auditory ERP might be used to reveal the disturbed steps within the cognitive process.     

Impaired facial recognition memory in aging and dementia

Young normals, aged normals, and patients with early and advanced probable dementia of the Alzheimer type (DAT) were administered a facial recognition memory task. A continuous recognition paradigm was used, in which subjects were instructed to identify the repeated faces in an ongoing series of faces presented on a video monitor screen. A signal detection analysis of the data revealed that the DAT patients were markedly impaired in their ability to discriminate between new and repeated faces. Multiple presentations of faces improved the recognition accuracy of the early DAT patients only, but their rate of learning was slower than that of the normal subjects. In comparison to the young normals, elderly normals exhibited a mild deficit in recognition memory. All of the elderly subject groups exhibited a more liberal response bias than the young normals, which eliminates the possibility that the impaired memory task performance of the aged subjects could be attributed to a more conservative test-taking strategy. The DAT patients exhibited impaired recognition even when the second presentation of a face immediately followed the first, which perhaps implies that task performance was also sensitive to the effect of DAT on visuoperceptual abilities or psychomotor speed.     

Neural anomalies during sustained attention in first-degree biological relatives of schizophrenia patients.

BACKGROUND: A deficit in sustained attention might serve as an endophenotype for schizophrenia and therefore be a useful tool in understanding the genetic underpinnings of the disorder. We sought to detail functional brain abnormalities associated with sustained attention (i.e., vigilance) in individuals with genetic liability for schizophrenia. METHODS: We gathered electrophysiological data from 23 schizophrenia patients, 28 first-degree biological relatives of schizophrenia patients, and 23 nonpsychiatric control subjects while they performed a degraded-stimulus continuous performance task. Inclusion of sensory control trials allowed separation of target detection and vigilance effects on brain potentials. RESULTS: Schizophrenia patients, but not relatives, showed a behavioral deficit in sustained attention. During target detection, relatives exhibited diminished late positive amplitudes (P3b, i.e., P300) over parietal brain regions and augmented early posterior (P1) and right frontal (anterior N1) potentials. Electrophysiological anomalies were still evident after the exclusion of three relatives with histories of psychosis. CONCLUSIONS: Genetic liability for schizophrenia is associated with augmented early and diminished late brain potentials during sustained attention. Electrophysiological anomalies suggestive of right frontal-posterior parietal dysfunction might represent neural expression of genetic liability for schizophrenia. Electrophysiological indices also seem to be more sensitive than behavioral measures in assessing genetic liability for schizophrenia.     

Early sensory information processes are enhanced on visual oddball and S1-S2 tasks in Parkinson's disease: a visual event-related potentials study

To observe sensory and cognitive information processing in Parkinson's disease (PD), 34 PD patients and 26 controls were investigated. A visual oddball paradigm and an S1–S2 paradigm were employed to record the early (P1, N1, P2) and late (N2, P3) event-related potentials (ERPs) at Cz, Pz and Oz. Results showed: (1) enlarged P1 amplitude at all electrode locations on both tasks, (2) shortened N1 latency and enlarged P2 amplitude at Oz on both tasks, (3) enlarged N1 amplitude at Cz during an oddball paradigm, (4) delayed N2 latency and decreased N2, P3 amplitude on both tasks, and (5) delayed P3 latency and reaction time during the S1–S2 paradigm. Abnormal ERP changes were correlated with worsened scores on Wechsler Adult Intelligence Scale-Revised and motor dysfunction scales in PD. We surmise overactive aspects or failed inhibitory modulation of sensory information processing in the early ERP stage and deficient cognitive information processing during the late ERP stage in PD.     

Temporal segmentation of response speed in depression: neuro-electrophysiological approaches

1. Depressive psychomotor retardation, as observed by delayed reaction times (RT), may be related to a slowing in information processing speed. 2. Two separate studies compared indices of information processing speed in depressed patients and non-clinical controls by segmenting behavioral RT with brain event-related potentials (ERPs) and electromyographic (EMG) responses. 3. In Study I, slower behavioral RTs in depression were concomitant with slower central processing times (CPT) but not motor execution times (MET). 4. In Study II, P165, a putative early cognitive ERP related to 'stimulus evaluation time', was found to be slower but within normal range in depressed patients.