Applications of magnetoencephalography to the study of cognition.
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Brain↗
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Results for “Contingent Negative Variation”
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Evoked potential correlates of auditory signal detection.
A long-latency comnponent of the averaged evoked potential recorded from the human scalp varied in close relationship with subjects' perceptual reports in an auditory signal detection task. Detected signals evoked potentials several times larger than did undetected signals, falsely reported signals, or correctly reported nonsignals. The threshold signal intensity at which detection perfornmance exceeded chance levels was identical with concurrently obtained electro-physiological measures of threshold.
Auditory Perception↗
Presence of Bereitschaftspotential preceding psychogenic myoclonus: clinical application of jerk-locked back averaging.
The method of jerk-locked back averaging was applied to six patients with clinically diagnosed psychogenic myoclonus. Five patients had a slow negative EEG shift corresponding to Bereitschaftspotential at the central region starting 0.7 to 2.1 seconds before the onset of the myoclonic jerk. One patient had no potential preceding the myoclonic jerk, whereas a small negative potential preceded the voluntary movement mimicking the jerk. The demonstration of Bereitschaftspotential before an apparently involuntary myoclonic jerk helps the clinical diagnosis of psychogenic myoclonus, although the absence of Bereitschaftspotential does not necessarily indicate that the movement is involuntary. Jerk-locked back averaging is clinically useful as a specific laboratory examination in this condition.
Adult↗
Movement related desynchronisation pattern preceding voluntary movement in untreated Parkinson's disease.
OBJECTIVE: To study planning of movement in Parkinson's disease. METHODS: The spatiotemporal pattern of movement related desynchronisation (MRD) preceding a self paced voluntary wrist flexion was compared between two groups of 10 untreated right and left hemiparkinsonian patients receiving no treatment and 10 control subjects. The MRD was computed in the 9 to 11 Hz frequency band from 11 source derivations covering the frontocentral, central, and parietocentral areas, during two successive left and right experimental conditions. RESULTS: In the two patient groups the desynchronisation appeared over the primary sensorimotor area contralateral to the affected side with a shorter latency (750 ms before movement onset for the right hemiparkinsonian group and 875 ms for the left hemiparkinsonian group) than in the control group (1750 ms), only when the movements were performed with the akinetic hand. For the non-affected hand, the same latency as in the control group was noted (1750 ms). CONCLUSION: The delay of appearance of MRD in Parkinson's disease confirmed that the programming of movement is affected, thus partially explaining akinesia.
Aged↗
Higher functions of the nervous system.
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Animals↗
Role of primary sensorimotor cortex and supplementary motor area in volitional swallowing: a movement-related cortical potential study.
We investigated the role of the cerebral cortex, particularly the face/tongue area of the primary sensorimotor (SMI) cortex (face/tongue) and supplementary motor area (SMA), in volitional swallowing by recording movement-related cortical potentials (MRCPs). MRCPs with swallowing and tongue protrusion were recorded from scalp electrodes in eight normal right-handed subjects and from implanted subdural electrodes in six epilepsy patients. The experiment by scalp EEG in normal subjects revealed that premovement Bereitschaftspotentials (BP) activity for swallowing was largest at the vertex and lateralized to either hemisphere in the central area. The experiment by epicortical EEG in patients confirmed that face/tongue SMI and SMA were commonly involved in swallowing and tongue protrusion with overlapping distribution and interindividual variability. BP amplitude showed no difference between swallowing and tongue movements, either at face/tongue SMI or at SMA, whereas postmovement potential (PMP) was significantly larger in tongue protrusion than in swallowing only at face/tongue SMI. BP occurred earlier in swallowing than in tongue protrusion. Comparison between face/tongue SMI and SMA did not show any difference with regard to BP and PMP amplitude or BP onset time in either task. The preparatory role of the cerebral cortex in swallowing was similar to that in tongue movement, except for earlier activation in swallowing. Postmovement processing of swallowing was lesser than that of tongue movement in face/tongue SMI; probably suggesting that the cerebral cortex does not play a significant role in postmovement processing of swallowing. SMA plays a supplementary role to face/tongue SMI both in swallowing and tongue movements.
Adult↗
Mismatch negativity: clinical and other applications.
The perspectives of application of the mismatch negativity (MMN), generated by the brain's automatic response to change in auditory stimulation, are discussed. In light of the fact that the MMN (and its magnetic equivalent MMNm) currently provides the only objective measure of the accuracy of the central auditory function, these perspectives appear very promising. The MMN can be measured in the absence of attention and task requirements, which makes it particularly suitable for testing different clinical populations and infants. Furthermore, the MMN enables one to evaluate the accuracy of auditory discrimination separately for any acoustic feature, such as frequency, intensity and duration, and for learned categories, such as the phonemes of a particular language. In addition, by measuring the decay of the MMN amplitude as a function of the interstimulus interval, it is possible to estimate the duration of sensory (echoic) memory.
Adult↗
Mismatch negativity: different water in the same river.
The mismatch negativity (MMN) is a frontal negative deflection in the human event-related potential that typically occurs when a repeating auditory stimulus changes in some manner. The MMN can be elicited by many kinds of stimulus change, varying from simple changes in a single stimulus feature to abstract changes in the relationship between stimuli. The main intracerebral sources for the MMN are located in the auditory cortices of the temporal lobe. Since it occurs whether or not stimuli are being attended, the MMN represents an automatic cerebral process for detecting change. The MMN is clinically helpful in terms of demonstrating disordered sensory processing or disordered memory in groups of patients. Improvements in the techniques for measuring the MMN and in the paradigms for eliciting it will be needed before the MMN can become clinically useful as an objective measurement of such disorders in individual patients.
Animals↗
Speech sound representation in the brain.
Biologic processes underlying speech sound perception and learning have been addressed using the mismatch negativity (MMN) evoked response. First is a consideration of how the acoustic properties of the signal affect the neural mechanisms and brain regions engaged. Because the MMN differs depending on the acoustic characteristics of the stimuli used to elicit the response, it has been used to probe mechanisms underlying the neural representation of stimuli along the auditory pathway. Second is a consideration of neurophysiologic correlates of speech sound perception and learning. Detailed is a 'behavioral-neurophysiologic, acoustic-phonetic approach', used to link perception with underlying physiologic processes in humans. The focus here is on children and what has been learned about normal maturation of speech sound perception and its disruption in certain children with learning disorders. The last topic is a consideration of central nervous system changes with perceptual learning. This includes long-term experience with one's native language and short-term auditory training in the laboratory. Limitations and future challenges are discussed.
Auditory Pathways↗
Involuntary attention and distractibility as evaluated with event-related brain potentials.
This article reviews recent event-related brain potential (ERP) studies of involuntary attention and distractibility in response to novelty and change in the acoustic environment. These studies show that the mismatch negativity, N(1) and P(3a) ERP components elicited by deviant or novel sounds in an unattended sequence of repetitive stimuli index different processes along the course to involuntary attention switch to distracting stimuli. These studies used new auditory-auditory and auditory-visual distraction paradigms, which enable one to assess objectively abnormal distractibility in several clinical patient groups, such as those suffering from closed-head injuries or chronic alcoholism.
Attention↗
Maturation of the mismatch negativity: effects of profound deafness and cochlear implant use.
The use of cochlear implants to restore auditory sensation in deaf children is increasing, with a trend toward earlier implantation. However, little is known about how auditory deprivation and subsequent cochlear implant use affect the maturing human central auditory system. Our previous studies have demonstrated that the obligatory auditory evoked potentials (AEPs) of implanted children are very different from those of normal-hearing children. Unlike the obligatory potentials, which primarily reflect neural responses to stimulus onset, the mismatch negativity (MMN) provides a neurophysiological measure of auditory short-term memory and discrimination processes. The purpose of this investigation is to review our studies of the effects of auditory deprivation due to profound deafness and cochlear implant use on the maturation of the MMN in children, placed in the context of overall age-related changes in the AEPs. The development and application of a statistical technique to assess the MMN in individuals is also reviewed. Results show that although the morphology of the obligatory AEPs is substantially altered by the absence of a normal N(1) peak, the MMN is robustly present in a group of implanted children who have good spoken language perception through their device. Differences exist in the scalp distribution of the MMN between implanted and normal-hearing children. Specifically, the MMN appears to be more symmetrical in amplitude over both hemispheres, whereas it is initially much larger over the contralateral hemisphere in normal-hearing children. These findings suggest that, compared to N(1), the MMN is a better measure of basic auditory processes necessary for the development of spoken language perception skills in profoundly deaf children and adults who use a cochlear implant.
Adult↗
Coma outcome prediction using event-related potentials: P(3) and mismatch negativity.
The prediction of the outcome from coma is of considerable importance to the patients, their relatives and attendant medical staff, and yet current clinical methods lack sensitivity and specificity. Objective investigations can enhance the accuracy of such predictions and are an important adjuvant when reaching decisions to continue or terminate life support. Of the neurophysiological methods available, electroencephalography and short-latency somatosensory evoked potentials have proved the most useful in the clinical setting. These tests are good predictors of an adverse outcome; however, they tell us only about the ongoing cerebral activity and integrity of the primary somatosensory pathways, respectively. The presence of long-latency event-related potentials has been shown to be a useful predictor of a favourable neurological outcome, and thus their use complements other neurophysiological techniques. Their potential application in clinical practice is reviewed.
Arousal↗
Mismatch negativity and N100 in comatose patients.
Mismatch negativity (MMN) and N100 auditory evoked potential were recorded in 52 healthy subjects and in 128 severely comatose patients. The MMN was present in 33/128 patients and N100 in 84/128. A ratio of 30/33 patients with MMN and 70/84 with N100 regained consciousness in a mean time of 6.3 +/- 4 days after the recording session. Thus, in terms of predicting return to consciousness, the MMN was more specific (90.9%) than the N100 (57.6%), but its sensitivity was lower (31.6% for MMN and 73.7% for N100, respectively). The amplitudes of MMN and N100 in comatose patients were smaller than those of healthy subjects. It is concluded that MMN and N100 can be very useful in predicting whether or not a comatose patient will regain consciousness.
Adolescent↗
Mismatch negativity and N100 monitoring: potential clinical value and methodological advances.
Continuous long-term recording of brainstem (BAEPs), middle-latency (MLAEPs) and long-latency auditory evoked potentials, including the mismatch negativity (MMN), brings additional information on the immediate functional state and the outcome of patients in coma or recovering after surgery, in relation with clinical observations and therapeutics. A recently designed monitoring system is introduced, aimed at the continuous recording of late auditory potentials (N100 and MMN) as well as BAEPs and MLAEPs. Specific methodological aspects are emphasized. Long-term monitoring data from one patient recorded in the recovery room after surgery are displayed, allowing an illustration of the techniques used and of the problems raised.
Adult↗
Intracortical mechanisms of mismatch negativity dysfunction in schizophrenia.
Event-related potentials provide an objective index of neurocognitive dysfunction in schizophrenia. Schizophrenia subjects show a decreased mismatch negativity (MMN) amplitude relative to age- and sex-matched controls, along with a characteristic pattern of MMN dysfunction across conditions. Deficits in MMN generation are accompanied by (1) impaired precision of auditory sensory memory performance and (2) an interstimulus-interval-dependent deficit in auditory N(1) generation. Similar deficits are observed following systemic or local infusion of N-methyl-D-aspartate (NMDA) antagonists, supporting glutamatergic and phencyclidine/NMDA models of the disorder. Deficits in MMN generation may also be seen following focal cortical damage, especially to the dorsolateral prefrontal cortex. MMN thus provides a useful tool for investigating mechanisms underlying brain dysfunction in schizophrenia.
Attention↗
Mismatch negativity in aging and in Alzheimer's and Parkinson's diseases.
Mismatch negativity (MMN) is an auditory event-related potential (ERP) that reflects automatic stimulus discrimination in the human auditory system. By varying the interstimulus intervals (ISIs), the MMN can be used as an index of auditory sensory memory. This paper focuses on MMN findings in aging and in Alzheimer's (AD) and Parkinson's diseases (PD). The accumulated data suggest that MMN to duration deviance, unlike MMN to frequency deviance, is reduced in amplitude in aging at short ISIs. The attenuated MMN to frequency deviance observed at long ISIs in elderly subjects seems to be caused by age-related memory trace decay. Existing results suggest that automatic discrimination for the frequency change is not affected in the early phase of AD, whereas the memory trace seems to decay faster in AD patients. The present findings on PD are not as conclusive, although they tentatively suggest deteriorated automatic change detection. The MMN appears to offer an objective tool for studying auditory processing and memory trace decay in different neurological disorders.
Aged↗
Unilateral neglect after right-hemisphere damage: contributions from event-related potentials.
Unilateral neglect is a frequent sequel of right-hemisphere damage. Patients suffering from neglect may fail to detect, orient to, acknowledge or respond to stimuli on their contralesional side, even in the absence of primary sensory or motor loss. Despite the major clinical significance of the phenomenon and its potential implications for our understanding of human cognition, the underlying cognitive deficits are not well understood. We review the relatively few event-related potential studies that attempted to assess the different parts of the cognitive system in neglect patients. We suggest that theories of neglect, based primarily on performance data, may be refined by incorporating these results, and that this line of research may provide information that is not available using traditional performance measures.
Attention↗