Mapping of event-related potentials to auditory and visual odd-ball paradigms in controls.

The paper reports the results of recordings and maps of event-related potentials (ERPs) obtained in normal subjects. ERPs were recorded from 19 scalp electrode derivations using both visual and acoustic paradigms. In normal subjects, topographical distribution of all ERP components is described in detail. Our findings in normals suggest that the early modulation of stimulus-related potentials could be located in primary associative areas, and that N2, P3a, P3b, and SW have different distributions.

N70 and P100 can be independently affected in multiple sclerosis.

We have studied the relationship between N70 and P100 of the pattern visual evoked potential in 98 patients with multiple sclerosis and in 59 controls. In patients with multiple sclerosis, P100 was either absent or had prolonged latency in 121 eyes (61.7%), while N70 was absent or prolonged in 97 eyes (49.5%). The total number of eyes with either N70 and/or P100 abnormalities was 137 (69.9%). Eighty eyes (40.8%) had abnormal latency of both P100 and N70, while 41 eyes showed P100 delays without corresponding N70 changes. Seventeen eyes had abnormal N70, but normal P100 latency. N70 and P100 appear to be more often absent in the definite rather than in the possible multiple sclerosis group. These data show that N70 and P100 can be independently affected in patients with MS.

Mapping of event-related potentials to auditory and visual odd-ball paradigms.

This paper reports the results of recordings and maps of event-related potentials (ERPs) obtained in normal subjects, patients with Alzheimer's disease (AD), progressive supranuclear palsy, confusional states, and in subjects with homonymous hemianopsia. ERPs were recorded from 19 scalp electrode derivations using both visual and acoustic paradigms. In normal subjects, the topographical distribution of all ERP components is described in detail. In 45% of AD patients, ERPs were normal; in 35%, although present, ERP components were delayed, while in the other 20% the N2 and P3 peaks could not be recorded. In patients with progressive supranuclear palsy, the normal ERP sequence was not identified. Our findings in normals and in hemianopic patients suggest that the early modulation of stimulus-related potentials could be located in primary associative areas, and that N2, P3a, P3b, SW should have different origins.

Spatial frequency-dependent abnormalities of the pattern electroretinogram and visual evoked potentials in a parkinsonian monkey model.

The pattern visual evoked potential (PVEP) and pattern electroretinogram (PERG) were studied in 5 cynomolgus monkeys before and during the development of a parkinsonian syndrome induced by MPTP. The stimuli were vertical bars of four spatial frequencies (0.5, 1.2, 2.5 and 3.5 cycles/degree (cpd) modulated at temporal rates of 1, 4, 6, and 8 Hz. Following MPTP administration, all monkeys developed parkinsonian signs accompanied by changes in the amplitude and latency of the PVEP and PERG. Sinemet L-dopat carbi olopa administration produced temporary recovery of both PVEP and PERG. Two of the monkeys were followed for a prolonged period: 30-40 days after MPTP, the parkinsonian signs showed partial recovery; the PVEP latency and amplitude to 2.5 and 3.5 cpd stimuli and the latency to 1.2 cpd showed improvement but remained abnormal. The latencies of PERGs were normal, but the amplitudes were significantly reduced when stimuli of 2.5 and 3.5 cpd were used. Both PVEP and PERG to 0.5 cpd stimuli returned to normal. No further modifications were seen in the recordings performed 6 months and 1 year later. This study demonstrates (1) that spatial frequency-dependent electrophysiological abnormalities occur in the MPTP-treated monkey, a result previously found in human Parkinson's disease, and (2) that dopamine has a specific function in neurotransmission in the visual system of primates.

Scalp distribution of pattern visual evoked potentials in normal and hemianopic monkeys.

We examined the hemispheric distribution of the pattern visual evoked potential in 3 Cynomolgus monkeys, before and after right optic tractotomy or left occipital lobectomy. The stimuli were vertical gratings of 4 spatial frequencies, presented using counterphase and on-off modulation at 1 and 8 Hz. In the normal monkey, the amplitude and latency of the PVEPs elicited by 1 Hz stimulation were similar across all electrode sites. While no differences were found in the phase of the PVEP elicited by 8 Hz stimulation across the different derivations, PVEP amplitude generally decreased over the lateral electrodes. Once experimental hemianopia was created, PVEPs recorded over the midline and the intact hemisphere were normal. However, partially polarity-inverted PVEPs of smaller amplitude were recorded over the deafferented hemisphere. In addition, the interhemispheric phase difference became more prominent in the PVEP recorded over the deafferented hemisphere as the spatial frequency was increased.

P300-like potentials in the normal monkey using classical conditioning and an auditory 'oddball' paradigm.

Endogenous components of evoked potentials resembling P300 in humans were sequentially studied in 3 cynomolgus monkeys (Macaca fascicularis) using an auditory 'oddball' paradigm. The two different auditory stimuli were 500 Hz and 4000 Hz tones, designated as the 'frequent' and 'rare' stimuli, respectively. The probability of 'rare' tone presentation was initially 0.2. We further used probabilities of 0.1, 0.3 and 0.5. The 'rare' stimulus was reinforced by electrical stimulation, which followed the onset of the high tone by 700 msec. After 3-5 training sessions, a late positive wave was observed following the 'rare' tone. The latency of this P300-like signal was 314 +/- 16.2 msec, and the amplitude was 23.6 +/- 3.14 microV. The amplitude of this potential was modified by changes in stimulus presentation probability and by withholding reinforcement.