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NEUROPHYSIOLOGICAL EVALUATION OF SENSORY SYSTEMS'
Citation:
Herr, D W. NEUROPHYSIOLOGICAL EVALUATION OF SENSORY SYSTEMS'. Presented at Society of Toxicology, Baltimore, MD, 3/21-25/2004.
Description:
Exposure to many neurotoxic compounds has been shown to produce a sensory system dysfunction. Neurophysiological assessment of sensory function in humans and animal models often uses techniques known as sensory evoked potentials. Because both humans and animals show analogous responses to sensory stimuli, extrapolation of effects from the laboratory to a clinical situation is simplified. Additionally, the methods are amendable to repeated testing, allowing the time-course of changes in sensory system function to be monitored. Furthermore, examination of multiple sensory modalities allows the determination of the specificity of a sensory dysfunction. A change in a sensory evoked potential can often be associated with pathological damage. Auditory system function at the level of the periphery and the brainstem can be assessed using Brainstem Auditory Evoked Responses (BAERs). Decreased amplitudes of the early BAER peaks have been associated with a frequency-dependent loss of cochlear hair cells. In contrast, decreased amplitudes of later BAER peaks have been associated with brainstem lesions. Evoked potentials can also be used to investigate changes in the visual system from the level of the retina to the cortex. Alterations in the early portions of cortical visual evoked potentials have been associated with pathological changes in the retina, thalamus, or cells involved in the early cortical processing of the stimulus. Besides quantifying changes in sensory function produced by neuroanatomical lesions, knowledge of the neuropharmacology of evoked potentials can be used to interpret changes after exposure to substances known to alter specific neurotransmitter systems. This allows the use of evoked potential technology to assess not only undesirable effects, but also to monitor for intended pharmacological actions. This is an abstract of a proposed presentation and does not necessarily reflect EPA policy.