Variable effects of pathologic scotomata on wave form of pattern-reversal visual evoked response

✍ Scribed by L. D. Blumhardt

• Publisher: Springer-Verlag
• Year: 1985
• Tongue: English
• Weight: 512 KB
• Volume: 59
• Category: Article
• ISSN: 0012-4486
• DOI: 10.1007/bf00160607

✦ Synopsis

Further experiments in healthy subjects have confirmed the characteristic but variable differential effect of experimental scotomata on the pattern evoked potentials. While the waveform changes associated with different pathological scotomata also showed considerable variability, certain features common to healthy and abnormal responses could be identified. These non-specific effects of scotomata on component amplitudes and distributions frequently result in spurious delays of wide-field responses and thus have important implications for the pathophysiological interpretation of abnormal responses.

Alterations of apparent latency and amplitude of wide-field pattern evoked responses (VERs) are a common finding in patients with central scotomata associated with a variety of pathologies. These abnormalities may be misinterpreted as having pathological specificity, unless the differential effects of the field defects themselves on the individual hemisphere components (Blumhardt and Halliday, 1979) are understood.

In this paper examples of multichannel recordings of half-field responses reveal that many abnormal features characteristic of pathologic responses are paralleled by the effects of small experimental 'scotomata' on the healthy VER waveform (Blumhardt et al., 1978).

Methods

The methods used in the present study are identical to those described in previous publications, to which the reader is referred for details of stimulation and recording techniques (