Biomedical subjects

H Scheich

Publications and source records attributed to H Scheich.

129 records · Page 8Linked to original sources

PubMedDate not supplied

Trained discrimination of temporal patterns: cochlear implants in gerbils.

The purpose of this study was to establish an animal model for the discrimination of temporal order cues contained in electrical stimuli to the cochlea. Gerbils were deafened and implanted in the right cochlea with a single platinum stimulating electrode. Two groups of animals were trained in a two-way active avoidance shuttle box paradigm to discriminate downward from upward interval-modulated pulse trains (1-100 ms). One group consisted of naive animals. The other group had previously been trained in the same shuttle box (same behavioral meaning) to discriminate identical pulse trains presented acoustically. Significant discrimination performance was found in the group of naive animals. However, over the 6-day training period, animals with previous acoustic experience achieved no significant discrimination performance. This suggests that temporal order cues in pulse trains can be used in cochlear implants to transmit behaviorally relevant information but that this may be in conflict with relevant auditory preexperience.

Animals↗

PubMedDate not supplied

Resolution of single deviant intervals in periodic stimuli by auditory cortex neurons: comparison of intracochlear electric pulse and acoustic click stimulation.

Responses of neurons in the primary auditory cortex were compared in gerbils receiving intracochlear electric or acoustic stimulation. Stimuli were trains of periodic electric pulses or of acoustic clicks. Interspersed between intervals of equal length were single intervals which were longer, by some Delta t. The Delta t and the repetition rate of these prolonged intervals were varied. The degree of synchronization of spikes to the regular occurrences of prolonged intervals was quantified. While thresholds for synchronized responses to Delta t (at Delta t repetition rates of 4--6 Hz) were about a hundredfold higher for electric (about 5--10 ms) than for acoustic stimulation (about 30 s), Delta t repetition rate response functions were similar for both types of stimulation. The results suggest the feasibility of coding brief acoustic transients by prolonged intervals in electric pulse trains with high pulse repetition rates, which could be another useful strategy for cochlear implants.

Acoustic Stimulation↗

PubMedDate not supplied

Bilateral ablation of auditory cortex in Mongolian gerbil affects discrimination of frequency modulated tones but not of pure tones.

This study examines the role of auditory cortex in the Mongolian gerbil in differential conditioning to pure tones and to linearly frequency-modulated (FM) tones by analyzing the effects of bilateral auditory cortex ablation. Learning behavior and performance were studied in a GO/NO-GO task aiming at avoidance of a mild foot shock by crossing a hurdle in a two-way shuttle box. Hurdle crossing as the conditioned response to the reinforced stimulus (CR+), as false alarm in response to the unreinforced stimulus (CR-), intertrial activity, and reaction times were monitored. The analysis revealed no effects of lesion on pure tone discrimination but impairment of FM tone discrimination. In the latter case lesion effects were dependent on timing of lesion relative to FM tone discrimination training. Lesions before training in naive animals led to a reduced CR+ rate and had no effect on CR- rate. Lesions in pretrained animals led to an increased CR- rate without effects on the CR+ rate. The results suggest that auditory cortex plays a more critical role in discrimination of FM tones than in discrimination of pure tones. The different lesion effects on FM tone discrimination before and after training are compatible with both the hypothesis of a purely sensory deficit in FM tone processing and the hypothesis of a differential involvement of auditory cortex in acquisition and retention, respectively.

Animals↗