Feasibility of using silicon-substrate recording electrodes within the auditory nerve.

The use of penetrating, silicon-substrate (i.e., "thin-film") probes within a cross-section of a sensory nerve offers the possibility of assessing the pattern and extent of fiber excitation within the nerve. We used acute cat preparations to assess the feasibility of this technique for recordings within the auditory nerve trunk. Four probe configurations fabricated by the University of Michigan Center for Neural Communication Technology were evaluated using acoustic and electric stimuli. Our main concerns were the nature of the recorded potentials and the degree of spatial selectivity provided by these probes. We also made some basic assessments of electrode-tissue compatibility. The recorded potentials were characterized as field potentials with varying degrees of spatial selectivity. In some cases, responses to pure tones demonstrated good spatial selectivity, with unique responses recorded by different electrode sites. When electrode sites were positioned at different longitudinal positions along the nerve trunk, responses with latencies characteristic of each site were recorded. These results indicate that thin-film electrodes are capable of providing spatially specific response information from sensory nerves. However, in the case of feline auditory nerves, place-specific responses were inconsistently observed, making it difficult to use this technique to obtain detailed cochleotopic maps of neural excitation. More productive results may be possible from other peripheral nerves with less complex spatial arrangements of fibers.