Stimulus-response profile analysis: a comprehensive, quantitative approach to the study of sensory coding and information processing

In order to understand the coding and information processing capabilities of mechanosensory neurons, it is necessary to examine stimulus-response relationships under a wide variety of stimulus conditions, using a comprehensive set of quantitative analytic procedures. We employ the methodology of stimulus-response profile analysis, which is based on 4 principles: (1) the use of a broad-based battery of quantitatively controlled mechanical stimuli; (2) maintenance of comprehensive records of experiments; (3) detailed, quantitative analysis of single-unit responses; and (4) the application of these principles uniformly and consistently to all units studied. In addition to conventional graphical portrayals of single-unit activity, we employ a set of quantitative response indices, each of which represents a particular aspect of a unit's overall responsiveness. The distribution of a response index for the entire sample of neurons examined in a particular population offers insight into the manner in which a specific stimulus feature is represented within that population. The distributions of response indices obtained from different neural populations can be compared statistically in order to evaluate interpopulation differences in stimulus-response relationships. This comprehensive, quantitative approach is capable of demonstrating significant, although subtle, interpopulation differences which are not revealed by more cursory, qualitative methods.