Christoph Schreiner, MD, PhD

Representation of Complex Signals in the Central Auditory System

Our understanding of the neural bases of the higher brain functions underlying human speech and language is still very limited.  We apply electrophysiological and neuroanatomical methods in combination with psychophysical, behavioral and computational techniques to study the transformation of distributed sound encoding in the central auditory system of carnivores and primates. Behaviorally relevant signals, such as environmental sounds, vocalizations, speech, and music, have a very complex composition of their spectrum that changes rapidly over time. This inherent complexity and variability of sounds has proven to be very challenging for the systematic exploration of the mechanisms underlying signal identification and classification.

To delineate the organizational principles in the central auditory representation of complex signals, we have chosen to analyze advanced spectro-temporal receptive field properties with dynamic noise-like stimuli, animal vocalizations and speech. We compare their distributions in the auditory thalamus and across auditory cortical fields. With this approach we have been able to identify a number of superimposed but independent systematic signal representations, including for frequency modulation, spectral integration, and signal intensity. Based on these identified organizational principles, we can study their neural substrate, contributing local circuitries, and emerging processing properties (such as object formation and robustness in noisy environments).

Further, we utilize the influence of representational cortical plasticity on the central coding of sounds by training animals to attend to specific classes of sounds. From the emerging selective representations of those sound classes in the cortex and the animals behavioral performance we can infer in animal models some of the principles that underlie the central manifestation of well known psychophysical attributes such as pitch, loudness, timbre, as well as that of speech perception attributes, e.g. categorical perception and phoneme recognition.

Current Projects

1. Electrophysiological and optical studies of distributed representations of sounds in auditory cortex of cats and squirrel monkeys
2. Receptive field properties and plasticity of auditory cortical neurons assessed with whole-cell recordings
3. Receptive field transformations between thalamus and cortex and between cortical laminae of cat and squirrel monkey auditory cortex
4. Effect of noise and reverberation on coding of sound in auditory cortex and the perceptual performance of monkeys
5. Neuroanatomical foundation of modular functional organization of auditory cortex
6. Effects of hearing loss on central auditory coding

Lab Members

Lab Website

Academic community service and committee membership:
BioE Graduate Advisor, BioE Exec committee