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R L Zimmern

Publications and source records attributed to R L Zimmern.

5 recordsLinked to original sources
PubMed1999

Genetic testing: a conceptual exploration.

This paper attempts to explore a number of conceptual issues surrounding genetic testing. It looks at the meaning of the terms, genetic information and genetic testing in relation to the definition set out by the Advisory Committee on Genetic Testing in the UK, and by the Task Force on Genetic Testing in the USA. It argues that the special arrangements that may be required for the regulation of genetic tests should not be determined by reference to the nature or technology of the test, but by considering those morally relevant features that justify regulation. Failure to do so will lead to the regulation of genetic tests that need not be regulated, and would fail to cover other tests which should be regulated. The paper also argues that there is little in the nature of the properties of gene tests, using DNA or chromosomes, that in itself justifies a special approach.

Advisory Committees↗
PubMed1983

Transient visually evoked potentials to the pattern reversal and onset of sinusoidal gratings.

Transient visually evoked potentials (VEPs) recorded in response to the contrast reversal and onset of spatially sinusoidal gratings have been investigated. Previous reports of an increase in the latency of the response at higher spatial frequencies have been confirmed but only for spatial frequencies higher than 2 c/deg. At lower spatial frequencies it is suggested that two positive components interact resulting in a departure from a monotonic relationship between latency and spatial frequency. Below 1 c/deg pattern reversal and pattern onset modes of stimulation produced VEPs of similar amplitude and wave form. Above 1 c/deg the amplitude of the pattern onset response peaked at a higher spatial frequency than the response to pattern reversal, and the response was dominated by a negative (N1) rather than a positive component (P1). This distinction has been corroborated by investigating the effect of field size variation. The peak amplitudes shifted to a lower spatial frequency with increase in field size but at all field sizes the N1 component of the pattern onset response peaked at a higher spatial frequency than the other components measured. It is attempted to relate these findings to previous studies of both grating and checkerboard VEPs and to psychophysical studies of contrast sensitivity.

Electroencephalography↗
PubMed1979

Subtle disturbances of vision after optic neuritis elicited by studying contrast sensitivity.

Eight patients with a subjective disorder of vision yet normal Snellen acuities after optic neuritis were shown to have an abnormal contrast sensitivity function in their affected eye. It appears that certain disorders of vision are associated with an abnormality of the contrast sensitivity function in spite of near normal visual acuity. Such an abnormality may affect pattern recognition without having an influence on Snellen acuity because of the high contrast of the latter and its predominant association with the higher spatial frequencies. Contrast sensitivity function is thus the only tool available to study those aspects of vision which have remained impervious to other subjective tests of visual function.

Adult↗