Biomedical subjects

T R Tobin

Publications and source records attributed to T R Tobin.

3 recordsLinked to original sources

PubMed1992

Temporal coding of pheromone pulses and trains in Manduca sexta.

We investigated the ability of pheromone-sensitive olfactory receptors of male Manduca sexta to respond to 20-ms pulses of bombykal, the major component of the conspecific pheromonal blend. Isolated pulses of bombykal elicited a burst of activity which decreased exponentially with a time constant of 160-250 ms. Trains of pulses delivered at increasing frequencies (0.5-10 Hz) elicited temporally modulated responses at up to 3 Hz. Concentration of the stimulus (1, 10, 100 ng per odor source) had a marginal effect on the temporal resolution of the receptors. Within a train, the responses to individual pulses remained constant, except for 10-Hz trains (short-term adaptation). A dose-dependent decline of responsiveness was observed during experiments (long-term adaptation). Although individual neurons may not respond faithfully to each pulse of a train, the population of receptors sampled in this study appears to be capable of encoding the onset of odor pulses at frequencies of up to at least 3 Hz.

Adaptation, Physiological↗

PubMed1991

Software filter for detecting spikes superimposed on a fluctuating baseline.

We describe and evaluate a software procedure for detecting and discriminating action potentials superimposed on a fluctuating DC baseline. Using an algorithm implemented in Fortran and Assembly language, spikes are detected by comparing the low-pass filtered first derivative of the signal with a preset threshold constant. This detection algorithm efficiently removes the DC baseline fluctuations usually encountered in sensory receptor recordings. It can function in real-time depending on the specific hardware configuration and program implementation. This approach enables the user to acquire direct DC-amplified signals, minimizing filter distortions of the action potential waveform.

Action Potentials↗

PubMed1991

Conditional withholding of proboscis extension in honeybees (Apis mellifera) during discriminative punishment.

Proboscis extension conditioning of honeybee workers was used to test the ability of bees to respond to appetitive and aversive stimuli while restrained in a harness that allows subjects to move their antennae and mouthparts (Kuwabara, 1957; Menzel, Erber, & Masuhr, 1974). Subjects were conditioned to discriminate between two odors, one associated with sucrose feeding and the other associated with a 10 V AC shock if they responded to the sucrose unconditioned stimulus (US) in the context of that odor. Most Ss readily learned to respond to the odor followed by sucrose feeding and not to the odor associated with sucrose stimulation plus shock. Furthermore, in the context of the odor associated with shock, significantly more subjects withheld or delayed proboscis extension on stimulation with the sucrose US than they did in the context of the odor associated with feeding. Thus, restrained honeybees can readily learn to avoid shock according to an odor context by withholding proboscis extension to a normally powerful releaser. Analysis of individual learning curves revealed that subjects differed markedly in performance on this task. Some learn the discrimination quickly, whereas others show different kinds of response patterns.

Animals↗