CNS*2001 Tenth Annual Computational Neuroscience Meeting San Francisco and Pacific Grove, California, June 30 - July 5, 2001

Research based upon averaged-evoked-responses is bedeviled by waveform overlap. When the ISI (Inter-Stimulus Interval) is less than the length of the evoked response, the early waves of a response overlap the later waves evoked by a preceding stimulus. Such overlap makes measurement or identification of generators in the evoked response difficult or impossible, yet accurate determination of the waveforms of such simultaneously-active generators would be of great importance in the interpretation of evoked-responses for both research and clinical uses. At this time, we are limited in evoked-response studies to only part of the range of stimulus rates encountered in natural situations. In some cases slow stimulation rates may be un-natural!

We will present the first public descriptions of a novel method to recover transient waveforms that have been overlapped due to high rates of stimulation. While the method is linear, it is applicable to responses which are non-linear with respect to stimulation rate, as well as to the non-linear evoked-response itself. Topics to be covered in this session are as follows:

1. The basic phenomenon: Transient responses to high repetition-rate stimuli differ from those driven by low repetition-rate stimuli. Recovery of the transient responses to high rate stimulation (40-90 Hz) allows study of brain responses at rates at and above those hypothesized to be preferential "oscillatory" rates that are thought to involve gestalt "binding" in the CNS. There may be differential sensitivity to stimulation-rate by some cells (or cell types). Such data might be used to develop filter criteria or stimulus parameters that could be used to separate responses from different cell types, e.g., neurons and glia.
2. The effects of attention on the transient response of the auditory system, when investigated using high repetition-rate stimuli, can be demonstrated to occur at earlier neural processing stages than previously supposed.
3. A technical description, including discussion of the relationship of this new method to presently-used techniques. We will present a mathematical description of the methodology, in the context of analysis of linear and non-linear systems. We will also indicate the difficulties that are encountered in practice.

High stimulation-rates are better at detecting pathological conditions in the nervous system. Thus, for diagnostic purposes, high-rate evoked-responses may increase the sensitivity of the testing. Thus, our new technique holds promise as a tool for both research and for clinical testing.

Speakers: Don L. Jewett, Linda Larson-Prior, Bill Baird

Organized by D. J. Jewett and L. J. Larson-Prior.