Faculty Bibliography

Eight patients with malignant gliomas were monitored with clinical examinations to study the effects of the combination of intravenous administration of carmustine and infraophthalmic intra-arterial administration of cisplatin on retinal and optic nerve function. Three patients developed a severe macular retinal pigment abnormality in the eye ipsilateral to the intra-arterial infusion. Electrophysiologic studies disclosed no evidence of a generalized disturbance in the photoreceptors, middle retinal layers, or retinal pigment epithelium. In contrast to previous studies involving patients whose visual loss was caused by vaso-occlusive lesions in the retina and optic nerve, our study involved patients with clinically significant maculopathy, that was not vascular in origin and that developed after treatment with carmustine and cisplatin. We suggest that the deficit may result from a localized retinal pigment disturbance in the macula

Human cortical visual evoked potentials (VEPs) were retrieved in real time (without averaging). The stimuli were sinusoidal gratings whose contrast was temporally modulated about some mean value. Electrophysiologically determined contrast modulation thresholds were measured at standing contrast over the range from 2.5% to 50%, defining an increment threshold function. Increment threshold functions were obtained under two different spatio-temporal stimulus conditions identified as 'sustained' (4 c/deg grating modulated at 1.5 Hz) and 'transient' (1 c/deg grating modulated at 20 Hz). Under each of these conditions, threshold responses were retrieved at both the fundamental and second harmonic of the contrast modulation frequency. Under 'sustained' conditions log increment threshold responses and the fundamental the second harmonic of the modulation frequency were similar to those at the fundamental except for a saturation effect (i.e., above a mean contrast of 25% there was little further reduction in modulation sensitivity). There was no contrast gain control under 'transient' stimulus conditions. In other words, the same absolute amount of contrast change produced threshold responses for all mean levels up to 25%. This was true at both the fundamental and second harmonic of the modulation frequency. Stimulus differences produce striking differences in the electrophysiologically inferred increment threshold function for grating contrast, but fundamental and second harmonic evoked responses reflect processes with similar increment threshold behavior

Patterns of refuge use and daily movement were recorded for Sesarma cinereum over two monthly observation periods. A total of 1,588 crabs were marked and released in this study and of these 576 were recaptured. Most individuals established relatively permanent shelters immediately after release and the site of each crab's shelter changed little throughout the study period. The choice of shelter location did not reflect a return to the home area since there was no correlation with the original capture area. Although a few individuals were observed to undertake long migrations along the marsh edge, most animals were consistently observed within 3 m of their refuge. The terrestrial habitat, patchy availability of shelters, and daily foraging combine to determine the nature of refuge use

1. Strabismic and anisometropic amblyopes typically have elevated contrast thresholds. Despite these threshold losses, previous research has shown that some amblyopic observers demonstrate normal suprathreshold contrast matching. 2. One explanation for these contrasting results is a differential impairment of independent contrast mechanisms. 3. We used a swept visual evoked potential threshold technique to electrophysiologically isolate and compare absolute and suprathreshold contrast mechanisms in a group of strabismic and anisometropic amblyopes. 4. For both groups of amblyopes, the sensitivities of the absolute and the suprathreshold mechanisms were equally elevated. 5. These results indicate that, in these amblyopes, both threshold and suprathreshold mechanisms of the VEP are impaired