EFFECTS OF EXERCISE ON VISUAL EVOKED POTENTIALS

The aim of this study was to investigate the effects of acute or habitual exercise on visual evoked potentials (VEP). The study group consisted of 9 female and 7 male volleyball players and the control group contained 9 female and 7 male students who were not involved in any sportive activity. The N75, P100, and N145 latency and amplitudes were measured before and after exercise. Intragroup comparison was made to evaluate the acute effects and intergroup comparison for the chronic effects of exercise. Significant differences were noted between athletes and the sedentary subjects in terms of pre-exercise left-N145 latencies and amplitudes and left -P100 amplitudes. Right-eye N145 latencies of inactive female subjects obtained before and after exercise were also statistically different. The results suggest that acute and habitual exercise affects the VEP responses independent from the body temperature and other physiological parameters. Small sized pre-exercise P100 amplitudes in the athletes can be attributed to the effect of rapid visual-activity-demanding sports on the central nervous system. Visual evoked potentials maybe used as neurophysiological criteria in defining the performance of an athlete.     

EFFECTS OF EXERCISE ON SOMATOSENSORY-EVOKED POTENTIALS

The aim of this study was to investigate the effect of acute and regular exercise on somatosensory-evoked potentials (SEP). The study group was designed as 9 female and 7 male volleyball players, and the control group as 9 female and 7 male sedentary students. The P1 and P2 latency and amplitude values were measured by tibial nerve stimulation on both lower extremities in the study groups before and after exercise on a treadmill. Intra-group comparison was made to evaluate the acute effects of exercise, and inter-group comparison for the chronic effects of it. Statistically significant difference was determined in pre-exercise right P2 amplitudes and post-exercise left P2 latencies of female volleyball players and sedentary girls. There was significant difference between only the pre-exercise left P2 latency when comparison was made between the sportsmen and sedentary male subject groups. There were significant differences between the pre-exercise left P1 and P2 latency values of sportswomen and right P2 amplitudes of sedentary female subjects. There was no significant difference between left P2 latency values of sportsmen and sedentary male subjects. In conclusion, it was determined that acute and regular exercise shortened the latency of sensory-evoked potentials while decreasing their amplitudes. When evaluating the sensory-evoked potentials in electrophysiology laboratories, the exercise capacity and physical activity levels of the subjects should be considered.     

Effects of exercise on somatosensory-evoked potentials

The aim of this study was to investigate the effect of acute and regular exercise on somatosensory-evoked potentials (SEP). The study group was designed as 9 female and 7 male volleyball players, and the control group as 9 female and 7 male sedentary students. The P1 and P2 latency and amplitude values were measured by tibial nerve stimulation on both lower extremities in the study groups before and after exercise on a treadmill. Intra-group comparison was made to evaluate the acute effects of exercise, and inter-group comparison for the chronic effects of it. Statistically significant difference was determined in pre-exercise right P2 amplitudes and post-exercise left P2 latencies of female volleyball players and sedentary girls. There was significant difference between only the pre-exercise left P2 latency when comparison was made between the sportsmen and sedentary male subject groups. There were significant differences between the pre-exercise left P1 and P2 latency values of sportswomen and right P2 amplitudes of sedentary female subjects. There was no significant difference between left P2 latency values of sportsmen and sedentary male subjects. In conclusion, it was determined that acute and regular exercise shortened the latency of sensory-evoked potentials while decreasing their amplitudes. When evaluating the sensory-evoked potentials in electrophysiology laboratories, the exercise capacity and physical activity levels of the subjects should be considered.     

Bimodal evoked potentials during long-term therapy with conventional or slow release preparations of carbamazepine and valproic acid in children and adolescents with epilepsy

The measurement of evoked potentials (EPs) may be particularly useful in clinical neuropharmacology for investigation of drug effects of afferent nerve conduction within CNS. The study aims at estimating the long term effects of conventional or slow release formulation (CR) of carbamazepine (CBZ) and valproid acid (VPA) on visual (VPA) and brainstem auditory (BAEP) evoked potentials. Investigation covered 125 patients 8 to 18 years old to whom both formulations of CBZ or VPA were administered in monotherapy. Everyone received a drug dosage which gave an adequate therapeutic plasma concentration and satisfactory seizure control. Antiepileptic drugs (AEDs) plasma levels were measured by means of fluorescence polarization immunoassay method aided of TDx Analyzer (Abbott, Diagnostic). EPs were registered by means of Multiliner (Toennies, Germany). A pattern of reversal stimulation for VEP was used. The latencies of N75, P100, N145 as well as interpeak amplitudes of N75/P100, P100/N145 were evaluated. The following BAEP parameters were considered: morphology of the potential, absolute latencies of waves I, III, V and I-III, III-V, I-V. EP were always performed in the same conditions and with the same equipment for the epileptic and control groups. The obtained values were compared with age-matched control group. The following BAEP abnormalities were observed: prolonged absolute latencies of waves I, III, V as well as prolonged IPLs I-III. The BAEP V/I amplitude ratio and morphology of the waves were normal in all patients. The VEPs abnormalities manifested as prolongation of P100 or N145 latencies and reduction of amplitudes N75/P100, P100/N145. Results of these electrophysiological studies with CBZ and VPA demonstrate that EP are sensitive, noninvasive reflectors of AEDs effects within the CNS.     

Migraine patients exhibit abnormalities in the visual evoked potential.

An experiment is described which compared visual evoked potential (VEP) amplitudes and latencies in normal subjects and migraine patients. Several VEP abnormalities were found: at vertex and to a lesser extent at temporal sites, P100-N120 amplitudes were larger in patients; at vertex and temporal sites N120 amplitudes were larger in patients; at temporal sites patents had larger N120-P200 amplitudes but smaller P100 amplitudes. Peak latencies of the VEP were also found to be abnormal in patients. At vertex, patients had delayed N120 peak latencies while at temporal sites delays were found in the P200 latencies. Patients were subdivided according to side of headache. Right-sided headache patients showed larger temporal P100 amplitudes and larger left temporal P100-N120 amplitudes than bilateral headache patients.     

Changes in the latencies of visual-evoked potentials in people undergoing tennis training——Dynamic comparison before and after 8 weeks training

BACKGROUND： Some previous studies have shown that exercise is an important factor that affects the latencies of visual-evoked potentials （VEPs）. OBJECTIVE： To investigate the effects of spending a period of time undergoing tennis training on the latencies of VEPs by comparing the latencies of VEPs before tennis training with those after 8 weeks of tennis training. DESIGN, TIME AND SETTING： The non-randomly concurrent controlled experiment was performed in the Department of Human Movement Sciences, Physical Education College, Shandong Normal University from April to June 2007. PARTICIPANTS： In total, 45 healthy volunteers from Shandong Normal University were selected as subjects, including 31 students majoring in physical education （11 males and 5 females participated in the tennis training plan for 8 weeks）, and 14 students from other subjects. Informed consent was obtained. According to whether they were majoring in physical education or not, and whether or not they took part in tennis training, the students were divided into 3 groups： a tennis group of physical education students （n = 16） a non-tennis group of physical education students （n =15） and a non-tennis group of non-physical education students （n = 14）. METHODS： The subjects in the tennis group took part in a regular tennis training plan of 2 hours a day and 3 days per week, for 8 weeks, while the subjects in two non-tennis groups were not in the tennis training plan The NDI-200 neural electricity tester （Shanghai Haishen Medical Electronic Instrument Co., Ltd.） was used to measure VEPs before and after the experiment in all three groups, and to compare the latencies of VEPs recorded before training with those recorded after training. MAIN OUTCOME MEASURES： Comparison of the changes in latencies of VEPs before and after 8 weeks of tennis training. RESULTS： All 45 subjects finished the test and datas from all were included in the statistical analysis. There were no significant differences among all the three group     

Visual and auditory evoked potentials during long-term vigabatrin treatment in children and adolescents with epilepsy.

OBJECTIVES: The aim of the study was to estimate the effects of Vigabatrin (VGB) as add-on therapy on visual (VEP) and brain-stem (BAEP) evoked potentials. METHOD: The investigation covered 100 epileptic patients from 8 to 18 years of age. The treatment included therapy with carbamazepine (CBZ) or valproate acid (VPA) using slow release formulations of these AEDs. Combination therapy was administered using add-on VGB in the recommended dose 57.4+/-26.5 mg/kg body mass/day. VEP and BAEP evoked potentials were recorded by means of Multiliner (Toennies, Germany). The obtained values were compared with age matched control group. RESULTS: Compared to control groups, significant differences in epileptic groups emerged in latencies of the peak III, V along with the interpeak intervals I-III of BAEP. Also VEP studies showed the reduction of N75/P100 and P100/N145 amplitudes. CONCLUSIONS: Adding VGB did not significantly increase the percentage of pathological abnormalities observed from EPs. Our electrophysiological studies demonstrate abnormalities in EPs parameters due to subclinical toxicity induced by AEDs. Major alterations produced bitherapy of VPA-SR + VGB and minor SR formulations of CBZ or VPA.     

Effects of rate of repetitive stimulus presentation on the visual evoked brain potentials of young adults with Down's syndrome.

Visual evoked brain potentials (VEP) to repeated stimuli of several interstimulus intervals (ISI) were recorded from young adults with Down's syndrome (DS). The following results were obtained: (i) An ISI effect previously observed in normals: VEP amplitudes increased with increase in ISI; some ISI effect on latency was also observed; (ii) VEP amplitudes of DS subjects were larger than VEP amplitudes of normals; (iii) VEP peak latencies of DS subjects were longer than VEP peak latencies obtained from normals; (iv) ISI had a more pronounced effect on VEP amplitudes of DS than normal subjects. These results are discussed with respect to CNS differences and issues of attention and information processing.     

Effect of check size on the pattern reversal visual evoked potential.

Modifications of the components of pattern-reversal visual evoked potentials (PR-VEP) with changes in check size of the stimulating pattern were studied in 11 healthy subjects. We made use of 8 different check sizes ranging between 10 and 90 min of arc. Changes in the check size modified in different manners the latencies and amplitudes of N75, P100 and N145. Two-step statistical analyses using the polynomial regression analysis method revealed significant modifications of latencies of the 3 components, but non-significant modifications of the amplitudes, except for N75. The latency and amplitude of N75 showed a significant inverse linear relationship with the logarithm of the check size, while the P100 and N145 latencies showed significant curvilinear relationships, with minimal latencies at check sizes around 35 min. These findings suggest different physiological properties of N75 from those of P100 and N145, and hence, the necessity to establish normal values for each check size of stimulation, for application in clinical studies.     

Appropriate stimulation in visual evoked potential to evaluate visual perception state of athletes★

BACKGROUND: Several studies have demonstrated that visual evoked potentials can be influenced by sport events. To the best of our knowledge, there are no specific parameters for the most appropriate stimulation for evaluating the functional state of athletes. OBJECTIVE: To investigate the best stimulation in visual evoked potential to apply to functional evaluation of athletes. DESIGN, TIME AND SETTING: Ninety-five, healthy students from the Shandong Normal University took part in an observational, contrast study. PARTICIPANTS: All active participants were male. Sixty-five students majored in physical education, and had participated in exercise for the duration of (4.26 ± 3.08) years. An additional 30 students majored in other subjects. METHODS: The neural electricity tester, NDI-200, was adapted to examine and record visual evoked potential with varying probes using bipolar electrodes attached to the head of all the participants in a dark room. The visual evoked potential values were analyzed transversally. A chessboard pattern reversal method was applied with the following parameters: 2 Hz stimulation frequency, brightness of 90 cdp, 80% contrast, 1–100 Hz bandpass filters, and 10 μV sensitivity; 100 responses were averaged. MAIN OUTCOME MEASURES: latency, peak latencies, and inter-peak latencies were measured in N75, P100, N145 with varying probe stimulations. RESULTS: (1) Comparisons between the little check, middle check, and big check stimulation, demonstrated that the common tendencies in visual evoked potential indexes of the two groups of N75 latency were successively shorter and N145 were longer. P100-N145 peak latency was decreased and each inter-peak latency was longer. (2) Changes of N75, P100, and N145 with different check stimulations in the physical education student group: after compared with the middle check stimulation, N75 latency was significantly longer (P < 0.01), and N75-P100 inter-peak latency (P < 0.05) and N75-N145 inter-peak latency were both shorter (P < 0.05). N75-P100 inter-peak latency was shorter (P < 0.01) in the little check stimulation. When compared with the big check stimulation, N75 latency was significantly longer (P < 0.01) and N145 was shorter (P < 0.01). Compared with the big check stimulation, N145 latency was significantly shorter (P < 0.05). (3) Changes of N75, P100, and N145 with different check stimulations in the normal students: when compared with the big check stimulation, N75 latency was significantly longer (P < 0.05) and N145 latency was shorter (P < 0.05). Each inter-peak latency was shorter (P < 0.05) in the little check stimulation. When comparing the middle check stimulation, N75-N145 inter-peak latency was shorter (P < 0.05). CONCLUSION: Large visual evoked potential differences were observed between students majoring in physical education and other subjects when medium probe stimulation was applied. These results suggest that the use of medium probe stimulation (25 mm×25 mm) should be adopted when evaluating the functional state of athletes. Key Words: visual evoked potential; functional evaluation; probe stimulation     

Multimodality evoked potentials in amyotrophic lateral sclerosis

Visual, brainstem auditory and somatosensory evoked potentials to medial nerve stimulation were recorded in 27 patients affected by amyotrophic lateral sclerosis. VEP N75, P100, N140, N75-P100 latencies and P100 amplitude, BAEP I-III, III-V and I-V interpeak-latencies were within normal limits in all ALS patients. Somatosensory evoked potentials were abnormally delayed in 8 patients: in 3 arms because of a delayed N9-N13 latency, in 9 arms because of a delayed N13-N19 latency.     

The effect of sex differences on event-related potentials in young adults.

Female/male cognitive differences have been studied for some time; however, such differences in Turkish population is unknown. Evoked potentials (EPs) of the brain have been applied as an index of information processing in a wide variety of normal and cognitive impaired subjects. Scalp event-related potentials (ERP) evoked by auditory stimuli were recorded in 20 male and 18 female neurologically and audiologically normal young Turkish subjects of 18-25 years (Av. 20.6) of age. Standard auditory "Oddball" paradigm involving simple discrimination task of concentrating on infrequent (target) stimulus and ignoring frequent (non-target) stimulus was employed. EEG activity was recorded at the Fz, Cz, Pz and Oz electrode sites of the 10-20 system using Ag/AgCl electrodes. Wave forms were collected and averaged off-line by a Pentium 100 computer, which also controlled the stimulus presentation. In general, significant main effects of gender and electrode site on evoked potential components were found. The interpeak amplitudes N1-P2 and N2-P3 were higher in the male subjects than in the female subjects at Cz. N2-P3 were higher in the male subjects than in the female subjects at Oz. The latencies of N1, P2, N2, P3 components were not different between both sex. For both sexes we found that N1-P2 amplitude was higher at Fz and Cz than Pz and Oz. N2-P3 amplitude was higher at Fz than Oz for only female subject. In male subjects, latency of N2 was longer at Fz than Oz. There were no significant differences in the latencies of N1, P2, and P3 components between electrode sites in both sexes. We suggest that ERP components could be affected by sex, electrode site, and cognitive performance.     

Visual evoked potentials in dementia: a meta-analysis and empirical study of Alzheimer's disease patients

A meta-analytic review of flash and pattern reversal visual evoked potential research indicates that elderly demented patients have longer P100 latencies than age-matched control subjects. In the present empirical research, patients with research diagnoses of probable Alzheimer's disease were compared with sex- and age-matched control subjects using P100 latencies of visual evoked potentials (VEP) elicited by flash and pattern reversal. As compared to control subjects, Alzheimer's disease patients showed significantly longer P100 latencies of the VEP elicited by pattern reversal; the flash P100 only marginally distinguished them. These findings are discussed within the context of VEP recording practices, patient selection, sex and age matching of control subjects, and the visual system.     

Effects of the anticonvulsant benzodiazepine clonazepam on event-related brain potentials in humans.

The effects of the benzodiazepine clonazepam (a drug used as anticonvulsant) on event-related brain potentials were investigated in healthy human subjects. Thirty-six male student volunteers (mean age 30 years) received clonazepam or a placebo in a double-blind setting. VEPs (visual evoked potentials) were obtained from the standard checkerboard reversal procedure; AEPs (auditory evoked potentials) and slow cortical potentials (CNV) were measured during a 2-stimulus reaction time paradigm, in which the quality of the acoustic S1 signalled whether the acoustic S2 would follow after 2 sec or after 6 sec. Each S2 requested a speeded button press. Compared to placebo, clonazepam significantly reduced P100 amplitude of the VEP and the amplitudes of the AEP components N1 and P3. On the other hand, clonazepam boosted the development of a distinct N2 which was not apparent in placebo subjects. The CNV was significantly reduced and reaction time increased under clonazepam compared to placebo. Specific versus non-specific damping effects of the benzodiazepine are discussed, comparing the present result with the pattern of ERP effects of the anticonvulsant carbamazepine that had been obtained using the same experimental paradigms.     

The interaction between sex and click polarity in brain-stem auditory potentials evoked from control subjects of Oriental and Caucasian origin

Brain-stem auditory evoked potentials (BAEPs) were performed on 30 male and 30 female young normal Oriental subjects, using both condensation and rarefaction stimulation. The effects of sex and click polarity on the BAEP latencies and amplitudes were studied. Females had shorter absolute and interpeak latencies and higher absolute amplitudes than the males. These sex-related BAEP differences were independent of the click polarity. Rarefaction clicks produced shorter wave I latency and longer I-III interpeak latency, but the differences were significant in the female only. The polarity-related BAEP amplitude differences were essentially independent of the sex. BAEPs performed on 60 sex- and age-matched young Caucasian subjects produced similar results. The importance of establishing control BAEP values according to the sex and click polarity is emphasised.     

Large check size pattern reversal visual evoked potentials – Full and sectorial field stimulation in multiple sclerosis and controls

Pattern reversal visual evoked potentials have been used to study optic neuritis. Although smaller check size in the central fields are more sensitive, larger check sizes can be advantageous for patient fixation and in poor vision. We compared sectorial central and peripheral hemisurround stimulus with commonly used full- and half- field stimulus using large check sizes (65′) in the context of optic neuritis and multiple sclerosis. Of 19 female and 16 male control subjects studied, females had shorter P100 latencies and larger amplitudes than males. In 9 of the 18 patients with VEP abnormalities, the central field abnormalities were greater than those recorded with the full field response. The results confirm for the first time that central field stimulation using large checks can show a greater extent of abnormality than can be appreciated with large check full field stimulation alone, and could be commonly employed to improve yield in the investigation of optic neuritis. The data suggest that it is necessary to collect separate gender-specific laboratory normal values using this check size.     

Visually evoked potentials in respiratory chain disorders

OBJECTIVES: Little is known about the frequency of abnormal visually evoked potentials (VEPs) in patients with respiratory chain disorders (RCDs). We thus wanted to investigate the frequency of abnormal VEPs in RCDs, how often VEPs are abnormal despite normal visual acuity, and which of the VEP variables are most often abnormal. MATERIAL AND METHODS: Reversal checkerboard VEPs of 26 patients with RCDs, aged 32-74 years, were evaluated. RESULTS: VEPs were abnormal in 17 of the 26 cases (65%). The P100 latency was prolonged at least unilaterally in 16 patients. The P100/N145 amplitude was decreased in a single patient. VEPs were abnormal without visual impairment in 9 cases (53%). CONCLUSION: VEPs prove useful to detect clinical or subclinical impairment of the optical tract in patients with RCDs. In the majority of the cases, the P100 latencies are prolonged while the P100/N145 amplitude remains normal.     

Fish oil supplementation improves visual evoked potentials in children with phenylketonuria.

Visual evoked potentials (VEP) were measured in 36 patients with early-treated phenylketonuria (PKU; aged 1 to 11 years) and good metabolic control before and after supplementation with omega-3 long-chain polyunsaturated fatty acids (LC-PUFA) from fish oil. Patients with PKU had significantly longer P100 latencies than 22 age-matched control subjects. After 3 months of LC-PUFA supplementation, VEP latencies improved significantly in PKU patients but did not change in 12 untreated healthy children. The authors conclude that omega-3 LC-PUFA are essential substrates for nervous system function even beyond infancy.     

A study on visual evoked responses in childhood epilepsy with occipital paroxysms.

As some apparently idiopatic epilepsies may occasionally pose diagnostic difficulties in regard to their precise status of etiology, evoked potentials, particularly visual evoked potential (VEP), may contribute to the diagnosis of childhood epilepsy with occipital paroxysms (CEOP) as a subsidiary method of evaluation. This study includes 19 children (10 boys 52.6%; 9 girls 47.4%) ranging in age from 5 to 17 years (mean SD = 9.68 3.28) suffering from CEOP and a control group of 30 normal children, matched for chronological age and sex. Peak amplitudes and latencies of the P100 component for pattern-shift VEP (PVEP) and of major positivity for flash VEP (FVEP) are measured, respectively. The results from this study demonstrate that amplitude and latency values in patients with CEOP differs insignificantly when compared with controls. Although, non-significantly, mean values of amplitudes for both PVEP and FVEP were higher in the patients than in the normal children, whereas latencies in FVEP were somewhat longer. There may be some tendency for the amplitudes to increase and the latencies to be delayed in VEPs in patients with CEOP, when an overall interpretation of our and similar studies are considered. In certain cases of diagnostic difficulty, VEP values may provide further information for the clinician, regarding either a symptomatic or an idiopathic nature of the underlying disorder.     

Changes induced by xylene and alcohol in human evoked potentials

Neurotoxic effects of industrial solvents have recently aroused great interest. Few studies have applied evoked potential methods to test acute or chronic neurotoxicity of solvents or alcohol. Eight young healthy male volunteers were exposed for 4 h to about 1200 or 700 mg/m3 of xylene alone or in combination with alcohol 0.8 g/kg. Single doses of 0.4 g/kg and 0.8 g/kg alcohol were also used as test substances, and the subjects stayed for 4 h in the exposure chamber also during 3 control days. Tests were conducted single-blind and the subjects acted as their own controls. Visual (VEPs) and somatosensory (SEPs) evoked potentials as well as electroretinograms (ERGs) were recorded in the mornings before the exposure and in the afternoons immediately after exposure stopped. A single dose of alcohol 4 h prior to recording increased the latencies of P50, N60, P115 and N155 of VEP dose-dependently. Alcohol alone did not change significantly the amplitude of VEP, but xylene 1200 mg/m3 in combination with alcohol 0.8 g/kg decreased significantly the amplitude of N60-P115. The lower concentration of xylene in combination with alcohol as well as xylene 1200 mg/m3 alone tended to have similar effects. Concerning the latency changes simultaneous xylene exposure tended to counteract the effect of alcohol. No significant effects on ERGs could be shown in any of situations. The effects of SEPs were minor or lacking, and the lower exposure levels were associated with more statistically significant changes than higher exposure levels.