PubMed · 7517591
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H P Robinson. 1994. Conductance injection.. https://doi.org/10.1016/0166-2236(94)90088-4
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Animals acquire information about sensory stimuli around them and encode it using an analogue or a pulse-based code. Behaviourally relevant features need to be extracted from this representation for further processing. In the electrosensory system of weakly electric fish, single P-type electroreceptor afferents accurately encode the time course of random modulations in electric-field amplitude. We applied a stimulus estimation method and a signal-detection method to both P-receptor afferents and their targets, the pyramidal cells in the electrosensory lateral-line lobe. We found that although pyramidal cells do not accurately convey detailed information about the time course of the stimulus, they reliably encode up- and downstrokes of random modulations in electric-field amplitude. The presence of such temporal features is best signalled by short bursts of spikes, probably caused by dendritic processing, rather than by isolated spikes. Furthermore, pyramidal cells outperform P-receptor afferents in signalling the presence of temporal features in the stimulus waveform. We conclude that the sensory neurons are specialized to acquire information accurately with little processing, whereas the following stage extracts behaviourally relevant features, thus performing a nonlinear pattern-recognition task.
The spontaneously hypertensive rat model has been used to show that hypertension is an important pathophysiological risk factor in age-related hearing loss. In the present study, compound action potential (CAP), electrochemical potential (ECP), and potassium concentration (CK+) measurements were taken from the cochlea of genetically predisposed, spontaneously hypertensive rats (SHR) and from normotensive Wistar-Kyoto (WKY) rats. In the SHR model, as the duration of hypertension increased with the animal's age (from 3 to 8 months), CAP thresholds increased, ECP increased in marginal cells only, and CK+ increased in both endolymph and marginal cells. Collectively, the data suggest that ionic alternations of cellular potentials are involved in hearing changes in the hypertensive state. Ultimately, such data may assist in understanding hearing loss in individuals who are diagnosed with hypertension.