Herrmann B, Henry MJ, Obleser J (2013). Frequency-specific adaptation in human auditory cortex depends on the spectral variance in the acoustic stimulation. Journal of Neurophysiology 109:2086-2096.
A huge problem for any neural system is to be sensitive in multiple environmental contexts without saturating. This study investigated how our auditory system deals with different spectral dynamics in our acoustic environment. Normal hearing young adults passively listened to acoustic sequences. Sequences consisted of tones which randomly varied in frequency. The spectral range was varied in two contexts: Frequencies were either narrowly spaced or widely spaced. (The figure below schematically shows the tone stimulation for narrow and wide spectral ranges).
Electroencephalography (EEG) was recorded while participants listened to the sounds sequences. For each unique tone frequency in each spectral range context, we examined the response magnitude at around 100 ms after tone onset. (The figure on the right top shows response time courses for each unique tone in the sequences.)
The frequency-specific response profile (shown below) was broadened for the wide compared to the narrow spectral range. The data suggest that neural responses dynamically adapt to the acoustic stimulation context. (The figure below shows response magnitudes from around 100 ms and quadratic functions fitted to the data; negative values means larger responses)