The impact of preceding noise on the frequency tuning of rat auditory cortex neurons.
BACKGROUND
In a natural environment, contextual noise frequently occurs with a signal sound for detection or discrimination in a temporal relation. However, the representation of sound frequency by auditory cortical neurons in a noisy environment is not fully understood. Therefore, the purpose of this study was to explore the impact of contextual noise on the cortical tuning to signal sound frequency in order to better understand the mechanism of cortical frequency coding in a complex acoustical environment.


RESULTS
We compared the excitatory frequency-level receptive fields (FLRFs) of neurons in the rat primary auditory cortex determined under both quiet and preceding noise conditions. Based on the changes of minimum threshold and the extent of FLRF of auditory cortical neurons, we found that the FLRFs of a cortical neuron were modulated dynamically by a varying preceding noise. When the interstimulus interval between noise and the probe tone was constant, the modulation of the FLRF increased as the level of noise was increased. If the preceding noise level was constant, the modulation decreased when the interstimulus interval was increased. Preceding noise sharpened the bandwidth of the FLRFs of 47.6% tested neurons. Moreover, preceding noise shifted the CFs of 47.6% neurons by more than 0.25 octaves, while the CFs of the rest of the neurons remained relatively unchanged.


CONCLUSIONS
The results indicate that the cortical representation of sound frequency is dynamically modulated by contextual acoustical environment, and that there are cortical neurons whose characteristic frequencies were resistant to the interference of contextual noise.
Key Laboratory of Brain Functional Genomics, Ministry of Education, Shanghai Key Laboratory of Brain Functional Genomics, Institute of Cognitive Neuroscience, School of Life Science, East China Normal University, Shanghai, China.
Yinting
Y
Peng
Pengpeng
P
Xing
Juan
J
He
Xinde
X
Sun
Jiping
J
Zhang
D000161:Acoustic Stimulation / Q000379:methods; D000200:Action Potentials / Q000502:physiology*; D000704:Analysis of Variance; D000818:Animals; D001303:Auditory Cortex / Q000166:cytology*; D001307:Auditory Perception / Q000502:physiology*; D009474:Neurons / Q000502:physiology*; D009622:Noise; D010470:Perceptual Masking; D011571:Psychoacoustics; D051381:Rats; D017207:Rats, Sprague-Dawley; D011930:Reaction Time; D013997:Time Factors