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 AG Basic mechanisms of auditory pattern recognition

 Stimulus-context dependence of auditory-cortex responses

Project description:

 

Figure: The Transient-Reduction-of-Excitability (TREX) model accounts for stimulation-history effects. The model assumes a pool of excitable neurons, of which only a fraction is activated by a stimulus. Following activation, the pool size reduces rapidly, but transiently. When a second stimulus S2 is presented before the pool has fully recovered, the number of neurons that are activated by S2 is smaller than that activated by S1 since P is smaller, although the activated fraction is the same (from Zacharias et al. 2012).

Prominent components of auditory cortical responses to sounds, recorded by means of magnetoencephalograhy (MEG) and electroencephalography (EEG), depend on the history of stimulation. For example, the M100 component of auditory-evoked event-related fields to a given stimulus not only depends on the duration of the interval to the preceding stimulus, but also on the longer-term stimulation history. Furthermore, a sound deviating in its physical characteristics from a preceding stream of identical standard sounds elicits a response which differs from that elicited by the same sound when in a different context. We try to understand these effects, also at the level of single-trials.

Also, stimulus-evoked event-related magnetic fields or electric potential recorded from different subjects, sensors or hemispheres differ such that the variance is not stable over time and grows with the grand mean and that the data are not normally distributed. Consequently, the additive model, generally tacitly assumed in the analysis and comparison of event-related responses in the literature, does not apply. We demonstrated that such data can follow the mixed model instead, with differences in additive terms and in scaling factors between data sets, and derived transformations and their mathematical foundations which transform such data into the additive model, suitable for common parametric statistical analysis.

Collaborators:

Dr. Artur Matysiak, PD Dr. Reinhard König, Dr. Cezary Sielużycki, Norman Zacharias (Special Lab Non-invasive Brain Imaging)
Prof. Wojciech Kordecki (Department of Management, University of Business in Wrocław, Wrocław, Poland)

Funding:

Deutsche Forschungsgemeinschaft Ko1713/10-1 to König R and Heil P: Novel approaches to characterize neural responses to standard and non-standard sounds in humans: A single-trial MEG/EEG study of the auditory mismatch negativity

Some key publications:

Matysiak A, Kordecki W, Sielużycki C, Zacharias N, Heil, P, König R (2013) Variance stabilization for computing grand means in MEG and EEG. Psychophysiology (in press)

Zacharias N, König R, Heil P (2012) Stimulation-history effects on the M100 revealed by its differential dependence on the stimulus onset interval. Psychophysiology 49:909-919.

Zacharias N, Sielużycki C, Kordecki W, König R, Heil P (2011) The M100 component of evoked magnetic fields differs by scaling factors: implications for signal averaging. Psychophysiology 48: 1069-1082.

Zacharias N, Sielużycki C, Matysiak A, König R, Heil P (2010) Relevant observations for averaging stimulus evoked magnetic fields across trials and across subjects. IFBME Proceedings 28: 179-182.

Zacharias N (2013) MEG Untersuchungen zur Varianzstabilität und Kontextabhängigkeit der Stimulusrepräsentation im menschlichen Hörkortex. Dissertation (eingereicht), Otto-von-Guericke-University Magdeburg

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