(Brosch, Selezneva, Oshurkova)

Many behaviorally important sounds consist of a series of discrete acoustic events. In initial studies we used two-tone sequences and found proactive (i.e. effects on the consecutive tone) and retroactive (i.e. effects on the preceding tone) interactions between the responses to the two tones. The effects are either inhibitory or facilitatory and depend on the frequency and time separation of the two tones. In ongoing research we investigate neuronal mechanisms underlying the categorical perception of frequency contours in animals that have learned to discriminate rising from falling contour.

Figure:
Schematics of poststimulatory effects in the auditory cortex. After the presentation of a tone the response of neuron to a consecutive tone can be suppressed (blue) or enhanced (red). The type of poststimulatory effect depends the frequency of the first tone and the time that has elapsed since its onset. The frequency ranges inducing forward inhibition and forward facilitation are related to the receptive field (green) of a neuron.

Key publications

Brosch, M. and Schreiner, C. E. (1997) Time course of forward masking tuning curves in cat primary auditory cortex. J. Neurophysiol. 77: 923-943.

Brosch, M., Schulz, A., and Scheich, H. (1998) Neuronal mechanisms of auditory backward recognition masking in macaque auditory cortex. Neuroreport 9: 2551-2555.

Brosch, M., Schulz, A., and Scheich, H. (1999) Processing of sound sequences in
macaque auditory cortex: response enhancement. J. Neurophysiol. 82: 1542-1559.

Brosch, M. and Scheich, H. (2002) Neural Representation of Sound Patterns in the Auditory Cortex of Monkeys. In: Ghazanfar AA (ed) Primate Audition: Ethology and Neurobiology. CRC Press, Boca Ration, Fl, pp 159-175.

Brosch, M., Selezneva, E., Bucks, C., and Scheich, H. (2004) Macaque monkeys discriminate pitch relationships. Cognition 91: 259-272.

Brosch, M. and Scheich, H. (under review) Tone-sequence Analysis in the Auditory Cortex of Awake Macaque Monkeys.