A neural circuit transforming temporal periodicity information into
a rate-based representation in the mammalian auditory system
Acoustical Society of America, (2007)Abstract
Periodic amplitude modulations (AMs) of an acoustic stimulus are presumed
to be encoded in temporal activity patterns of neurons in the cochlear
nucleus. Physiological recordings indicate that this temporal AM
code is transformed into a rate-based periodicity code along the
ascending auditory pathway. The present study suggests a neural circuit
for the transformation from the temporal to the rate-based code.
Due to the neural connectivity of the circuit, bandpass shaped rate
modulation transfer functions are obtained that correspond to recorded
functions of inferior colliculus (IC) neurons. In contrast to previous
modeling studies, the present circuit does not employ a continuously
changing temporal parameter to obtain different best modulation frequencies
(BMFs) of the IC bandpass units. Instead, different BMFs are yielded
from varying the number of input units projecting onto different
bandpass units. In order to investigate the compatibility of the
neural circuit with a linear modulation filterbank analysis as proposed
in psychophysical studies, complex stimuli such as tones modulated
by the sum of two sinusoids, narrowband noise, and iterated rippled
noise were processed by the model. The model accounts for the encoding
of AM depth over a large dynamic range and for modulation frequency
selective processing of complex sounds.