Pattern reversal visual evoked potentials in minor head injury

Pattern reversal visual evoked potentials (PR-VEPs) have been recorded in 50 patients with minor head injury (MHI) on days 1 and 30 after trauma and the data compared to 20 normals. None of the patients had visual complaints. The aim was to investigate a possible visual pathway affection in MHI and test the usefulness of PR-VEPs as an objective noninvasive tool in the detection of a possible subclinical affection of the visual system in MHI. P100 latency and amplitude had no significant difference compared to normals. Comparison of patient data on days 1 and 30 after trauma showed a significant latency decrease and amplitude increase on day 30, compared to day 1. These alterations were not age dependent. Our data suggest affection of the human visual pathway in MHI. PR-VEP recording seems to be a useful, objective, noninvasive tool, helping to identify possible subclinical affections of the visual pathway in MHI.     

Memory processes and evoked potentials.

Reviews research on memory and evoked potentials (EPs) and presents new experimental data in which a storage component of the EP was identified. In Exp I, Ss performed information-processing operations on number and letter comparison tasks under 16 conditions varying stimulus, position, and relevance while EEGs were taken. In Exp II, 52 Ss were tested for short-term recall under the same 16 conditions. From Exp I, an EP storage component with a poststimulus maximum about 250 msec was found to be related to the storage of stimulus information in short-term memory. The storage component results led to a memory prediction that was substantiated in Exp II. Recall was not as closely related to 2 other, orthogonal EP components (P??? and CNV). Retrieval from and storage in short-term memory are discussed. Memory scanning rate derived from P??? latency changes with memory set size are faster than, but comparable to, RT estimates. An EP experiment dealing with levels of processing and memory is discussed, and a schematic model of some aspects of EPs that may be related to memory processes is presented. (French abstract) (26 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Evoked cortical potentials and measurement of human abilities.

Studied visual averaged evoked potentials (AEPs) recorded from the frontoparietal scalp of 108 16-68 yr. old Ss. Ss also completed a battery of 16 ability measures. A consistent pattern of reliable correlations of the order of from -.15 to -.32 was found between intelligence and AEPs. Measures of fluid and crystallized intelligence correlated to about the same magnitude with AEPs. There were significant correlations between measures representing simple cognitive processes (e.g., motor-perceptual speed) and evoked potential latency. The average size of ability-latency correlations as well as the number of significant correlations increased as conditions of evoked potential testing which tend to impose alertness on Ss were relaxed. (34 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Evoked potential abnormality scores are a useful measure of disease burden in relapsing-remitting multiple sclerosis

OBJECTIVES: To identify the incidence and the success of endourologic therapy for symptomatic bladder-related calculi in simultaneous kidney-pancreas (SPK) transplant patients with bladder drainage. METHODS: A retrospective review of 300 SPK transplant patients with bladder drainage, treated at the University of Wisconsin, Madison from December 1985 to November 1995, is presented. A 3% incidence of bladder calculi was identified. All patients underwent cystolitholapaxy using electrohydraulic lithotripsy and endoscopic suture removal. Follow-up ranged from 15 to 86 months. RESULTS: A 100% stone-free rate was achieved after cystolitholapaxy and endoscopic suture removal. Two patients (22%) developed postprocedural urinary tract infections. No pancreaticoduodenocystotomy leaks or further complications were identified. CONCLUSIONS: SPK transplant patients with nonabsorbable sutures used for the duodenocystotomy anastomosis are at an increased risk for bladder calculi. Cystolitholapaxy with electrohydraulic lithotripsy is a safe and effective treatment for these suture-related stones.     

Hypnotic hallucination alters evoked potentials.

Studied whether the amplitude of the visual EP is reduced during hypnotic hallucination in which the S is instructed to perceive visual stimuli as diminished in brightness or obstructed from view. The visual EP responses of 6 high- and 6 low-hypnotizable Ss (aged 18–33 yrs) and of 6 undergraduate controls were compared in 3 hypnotic conditions: stimulus enhancement, stimulus diminution, and stimulus elimination (obstructive hallucination). ANOVA revealed that high-hypnotizable Ss demonstrated significant suppression of the later components of the EP response (N? and P?) while experiencing obstructive hallucinations, indicating a change in information processing. This effect was significantly greater in the right, as compared to the left, occipital region. (35 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Brainstem auditory evoked potentials and visually evoked potentials in young patients with IDDM

OBJECTIVE: To investigate whether young IDDM patients develop central nervous dysfunction and to establish a possible relationship with various disease parameters. RESEARCH DESIGN AND METHODS: Thirty-two patients, aged 13.5 +/- 2 years, with disease duration of 6 +/- 2.6 years and age of onset of 7.7 +/- 3.2 years (group 1), and 21 patients with short-term disease, age 9.7 +/- 3.5 years, duration of disease < 2 years and age of onset of 9.4 +/- 3.3 years (group 2) were compared with age- and sex-matched control subjects. Exclusion criteria were clinical signs of neuropathy, retinopathy, nephropathy, or hearing impairment. Neurophysiological studies included auditory and visually evoked potentials (EPs). RESULTS: Patients in group 1 revealed increased P100 latencies of visually EPs (103.4 +/- 4.5 vs. 96.8 +/- 3.7 ms) and interpeak latencies I-V of auditory EPs (4.16 +/- 0.10 vs. 3.99 +/- 0.09 ms) and had abnormal latencies (values outside 2.5 SD) in 37%. However, short-term patients (group 2) had results within normal limits compared with control subjects. In group 1, longer disease duration and younger age at onset correlated with an increase of P100 latency (P < 0.001) and IPL I-V (P < 0.001). Patients with a history of severe hypoglycemic episodes had increased latencies compared with patients without hypoglycemia (P < 0.05). Furthermore, metabolic control during the last 2 years was related to P100 latencies (P < 0.05). CONCLUSIONS: EPs noninvasively detect subclinical central nervous system involvement in children and adolescents with IDDM. Most important risk factors are duration of disease and frequency of severe hypoglycemia.     

Effect of phenytoin and carbamazepine on evoked potentials in patients with newly diagnosed epilepsy. Part I. Visual evoked potentials

Pattern-reversal visual evoked potentials (VEPs) were recorded in 64 patients with newly diagnosed epilepsy. Before starting medication the patients with partial and primary generalized epilepsy, had prolonged latencies of the VEPs component P100, as compared with controls. VEPs were repeated after 3 months in 43 patients with focal epilepsy, during carbamazepine (22 cases) or phenytoin (21 cases) treatment. The plasma concentration of the drugs were within therapeutic levels. Carbamazepine but not phenytoin, was associated with prolongation of the P100 peak latency and induced increase of its amplitude, as compared with the baseline condition. The VEPs abnormality was most pronounced in patients whose seizures were poorly controlled. We conclude, that administration of carbamazepine or phenytoin, at therapeutic serum level, have minimal effect on the VEPs.     

Acupuncture and cortical evoked potentials

Research works for the effects of acupuncture on cortical evoked potentials were reviewed since 1970 in this article. As a result of the acupuncture anesthesia being applied widely in clinical operation, most of the studies were focused on the evoked potential of somatosensory cortex for elucidating the principle of the analgesic effect of acupuncture, while less observations were reported on the aspects of auditory and visual cortex. The amplitude of the evoked potential was often used as an index in assessing the excitability of the cerebral cortex in the studies of the effect of acupuncture in the past. An increase in the amplitude of evoked potential means an excitory process of the cortex and a decrease means depression. Based on their work, the authors consider that whether the change in the amplitude of cortical evoked potential could be served as an optional index in reflecting the excitability of the cortex is still a problem in neurophysiology remained for further investigation.     

Habituation and the human evoked potential.

Studied habituation of human scalp-recorded cerebral evoked potentials (EPs) in response to auditory and visual repetitive stimuli of different intensities; 26 right-handed 19–32 yr old students were Ss in 2 experiments. Changes in magnitudes of EPs with stimulus repetition were examined according to the parametric characteristics of habituation, generalization, and dishabituation. In addition, tests of the predictors of 2 theories of habituation were made regarding the degree and direction of intensity generalization of habituation. Both auditory and visual EPs exhibited decrements in response magnitudes across the repetitive stimuli consistent with the parametric criteria of habituation. Early EP peak components showed a pattern of intensity generalization of habituation consistent with the predictions of the dual-process theory of habituation. Intensity generalization of late EP peak components occurred in a manner more consistent with the predictions of the stimulus comparator theory of habituation. Results provide further evidence that EPs can be used as electrophysiological indexes of plasticity in humans. (33 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Neuropsychological outcome at 1-year post head injury.

Neuropsychological outcome at 1 year postinjury was examined prospectively in representative groups of 4–6 adult head-injured participants and 121 general-trauma control participants. A comprehensive battery of neuropsychological measures was administered. The head-injured group performed significantly worse than the trauma controls on most measures (p?     

Interpretation of evoked potentials: A neurophysiological perspective.

Discusses 3 aspects of the problem of inferring information about nervous system function from evoked potential (EP) measurements: (1) electrogenesis of EPs, including their relation to the geometry of individual cells and cell groups; (2) effects of recording EPs from the scalp or body surface instead of directly from neural tissue; and (3) quantitative approaches to the problem of EP source localization. Primary emphasis is placed on the intimate relationship between EPs, anatomical structures, and physiological processes that give rise to them, and the properties of potential fields in conductive media. (French abstract) (86 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Spinal cord evoked potentials and edema in the pathophysiology of rat spinal cord injury. Involvement of nitric oxide

The possibility that nitric oxide is somehow involved in the early bioelectrical disturbances following spinal cord injury in relation to the later pathophysiology of the spinal cord was examined in a rat model of spinal cord trauma. A focal trauma to the rat spinal cord was produced by an incision of the right dorsal horn of the T 10-11 segments under urethane anaesthesia. The spinal cord evoked potentials (SCEP) were recorded using epidural electrodes placed over the T9 and T12 segments of the cord following supramaximal stimulation of the right tibial and sural nerves in the hind leg. Trauma to the spinal cord significantly attenuated the SCEP amplitude (about 60%) immediately after injury which persisted up to 1 h. However, a significant increase in SCEP latency was seen at the end of 5 h after trauma. These spinal cord segments exhibited profound upregulation of neuronal nitric oxide synthase (NOS) immunoreactivity, and the development of edema and cell injury. Pretreatment with a serotonin synthesis inhibitor drug p-chlorophenylalanine (p-CPA) or an anxiolytic drug diazepam significantly attenuated the decrease in SCEP amplitude, upregulation of NOS, edema and cell injury. On the other hand, no significant reduction in SCEP amplitude, NOS immunolabelling, edema or cell changes were seen after injury in rats pretreated with L-NAME. These observations suggest that nitric oxide is somehow involved in the early disturbances of SCEP and contribute to the later pathophysiology of spinal cord injury.     

Cerebral evoked potentials and semantic categorization

INTRODUCTION: Cerebral evoked potentials represent variations in the electrical activity of the nervous system, excited by a sensory stimulus and which are recorded on the surface. They may be classified as endogenous or exogenous. Amongst the late endogenous evoked potentials (EEP) we may emphasize N400 which seems to represent the linguistic management wave, particularly for semantics. OBJECTIVE: To observe the EEP recorded throughout the process of carrying out a task involving sequential semantic categorization. PATIENTS AND METHODS: Nine healthy subjects carried out a task based on a paradigm of sequential reaction time (RT), similar to that designed by us in 1994. The data recorded were the RT and EEP at the level of the electrodes Fz, Cz and Pz in five lots of stimuli (in the first four lots the same list of words were repeated and in the fifth and final lot a different, new list appeared). CONCLUSIONS: It was seen that only N400 varied during the procedure. This variation was related to familiarity with the task. That is to say that the amplitude of N400 was reduced when the same words were repeated and increased when new words appeared for semantic classification. The reduction in parallel, although not significant for RT, allowed the reduction in N400 alone to be followed whilst the task was carried out. It may be the electrophysiological marker of the process of learning semantic categorization.     

Evoked potential studies of visual perception

Discusses the use of evoked potentials (EPs) to study the sensory processing of visual information. Two types of response, transient and steady-state, can provide complementary information, and in some situations the steady-state method is speedier. EPs can be treated as objective signs that visual signals have arrived at the cortex. The experimenter can then manipulate stimulus variables (as in psychophysics) and record EPs that are specific to stimulus features (e.g., spatial contrast, color, stereoscopic depth, motion, and flicker). In situations where there is a close correlation between EPs and visual perceptions, EP recording offers a means of (1) extending psychophysical studies on sensory channels to include physiological data, (2) investigating visual processing at super- and subthreshold levels, (3) testing subtle visual functions in infants with eye pathway disorders, (4) monitoring visual maturation in babies, and (5) linking single-cell studies in animals with human psychophysics. (French abstract) (169 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Lack of appetitive arousal effects on auditory evoked potentials.

Click-evoked potentials were recorded from the round window (cochlear microphonic and auditory nerve), cochlear nucleus, and auditory cortex of 6 female cats during periods of food deprivation. At all sites, the amplitude of click-evoked potentials remained constant as deprivation time increased from 0 to 24 hrs. In addition, increased food deprivation time had no systematic effect on EEG activity recorded from the auditory cortex for either the high-voltage/low-frequency (2–20 Hz) or the low-voltage/high-frequency (18–30 Hz) wave patterns. Since the food deprivation procedure used did not produce a state of heightened EEG arousal, the most likely explanation for the lack of effect on auditory evoked potentials was that neural events which may result in attenuation of auditory evoked potentials were not initiated. (17 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Auditory evoked potentials and acoustically-directed behavior of nestlings

Characteristics of auditory evoked potentials (EP) were studied in 1.5 to 7.5 days old Pied Flycatchers nestlings (Ficedula hypoleuca) with chronically implanted electrodes in the field L (analogue of the mammal's auditory cortex). EPs simultaneously with behaviour were recorded in nestlings under conditions similar to natural, in response to "feeding" calls and pure tones of different frequency and intensity. It was found that EP generation thresholds do not depend on the sum total of factors which influence the organization of feeding behaviour. The EP generation threshold is by 13-36 dB (for different frequencies) below that of the appearance of feeding responses in nestling with a maximum high motivation. It is suggested that the realization of inborn behaviour with a signal basis needs not only an integration (formed in the process of embryogenesis) of a definite sensory input with a complex of structures of the "feeding centre", but also the presence of a massive modality-specific inflow.