Biomedical subjects

B Ronacher

Publications and source records attributed to B Ronacher.

4 recordsLinked to original sources

PubMed1992

Pattern recognition in honeybees: multidimensional scaling reveals a city-block metric.

Bees were trained to discriminate ring-patterns which varied in number of rings and in size. Transfer-tests revealed size discrimination to be largely independent of pattern type and vice versa. A multidimensional scaling procedure, using Minkowski metrics as models, was applied in order to determine the bee's "perceptual metric". The city-block metric, and not the Euclidean metric, provided the best description of the data. Apparently, the bee's perceptual system derives the overall dissimilarity of complex ring-patterns additively from the component differences. These results are discussed with regard to "holistic" and "analytic" processing modes postulated for the perception of human subjects.

Animals↗

PubMed1990

Perception of size and lightness of human observers: two criteria for holistic and analytic processing show no correlation in individuals.

Results of a triad-classification task and a multidimensional-scaling (MDS) experiment are compared for individual observers. Both paradigms are designed to reveal whether stimuli are perceived in a holistic or analytic manner (Garner 1974). Subjects differed substantially and consistently in their triad classification pattern. The majority of subjects selected stimuli according to dimensional criteria; this classification type is thought to indicate an analytic stimulus processing. Approximately one third of subjects, however, used a classification according to overall similarity (indicating holistic processing). Except for the very first session, virtually no intermediate classification occurred. This clear separation into two classification types suggests that there actually exist two strongly preferred processing modes. Intraindividual variability between sessions in general was small. In one case, however, a spontaneous switching from a purely dimensional classification to a purely similarity classification occurred. This indicates that the observers have different processing options at their disposal, and are not forced to use a particular processing mode by the stimulus type--as has been supposed in the original concept of integrality/separability of stimuli (Garner 1974). In the MDS experiment also substantial interindividual differences in the "best-fitting" Minkowski metric were found, indicating different processing types. However, for individuals participating in both experiments, there was no correlation between the results of the two experimental paradigms. This is interpreted as a result of the subject's ability to choose between a few perceptual-processing options.

Central Nervous System↗

PubMed1985

Human pattern recognition: individually different strategies in analyzing complex stimuli.

Multidimensional scaling experiments were performed with "size" and "brightness" as parameters. Subjects (ss) had to rate the dissimilarity of pairs of discs differing in size or in brightness only, or in both parameters. It was then attempted to find a rule, by which the dissimilarity judgements of two-dimensional differences can be predicted from judgements given for the one-dimensional components. Minkowski-metrics were chosen as models, since for most of the ss the prerequisites for applying these metrics seem to be fulfilled. A simple procedure is described by which the one metric out of all Minkowski-metrics can be found which gives the best description for the data of a subject (Fig. 4). Although the task and the parameters used were the same for all ss, individually best metrics differed considerably, indicating individually different modes of perceptual analysis: Most ss adhered, roughly, to either the City-block or the Euclidean metric (cf. Fig. 10). (Only City-block metric was to be expected, since "size" and "brightness" are generally thought to be "separable" parameters.) In addition, there were three ss with metrics clearly different from both the City-block and the Euclidean metric (best exponents around 1.4). In view of those substantial differences between individuals one has to be cautious against the practice of averaging data from different ss.

Cybernetics↗

PubMed1985

Spike synchronization of tympanic receptor fibres in a grasshopper (Chorthippus biguttulus L., Acrididae). A possible mechanism for detection of short gaps in model songs.

In recordings from single tympanic receptor fibres in C. biguttulus, the response to synthesized sounds (rectangularly modulated white noise) interrupted by very brief (a few milliseconds) gaps was examined. In behavioral tests, females of the species respond very differently to such 'model syllables' at moderate intensities, depending on the gap width. If the gaps (in a moderate-intensity syllable) are larger than 2 ms, the stimulus fails to elicit a response, whereas stimuli with gaps smaller than 1 ms are as effective as uninterrupted syllables (D. von Helversen 1972; O. von Helversen 1979). Neither the mean spike count nor the interspike-interval distribution of the single receptor response contains the information sufficient to distinguish uninterrupted syllables from syllables with gaps. On the other hand, examination of the temporal distribution of the spikes reveals that gaps (or the pulse onsets following the gaps) cause spike synchronization. An index of synchronization (IS) was defined as a measure of this gap-induced effect. Analysis of the receptor responses based on IS revealed differences that correspond quantitatively to the abrupt abolition of the behavioral response at a gap-width between 1 and 2 ms. From the hypothesis that such brief gaps are detected by the nervous system by way of spike synchronization in the tympanic nerve, one can predict certain features of the behavioral response to high-intensity stimuli. The gap-induced spike synchronization was more pronounced at higher temperatures. This effect was demonstrated in both summated recordings from the tympanic nerve and single fibre recordings. Experiments with primary auditory fibres of Locusta migratoria showed that the receptors in this species respond very similarly to the same stimuli. That is, the receptors of C. biguttulus are not specially adapted for detecting very brief gaps. Synchronization of the spikes in parallel receptor fibres of the tympanal nerve is probably a general feature of acridids; we infer that in C. biguttulus this gap-induced synchronized activity is detected by special processing in higher auditory centres.

Animal Communication↗