Integration of stimulus history in information conveyed by neurons in primary auditory cortex in response to tone sequences

S. Klampfl, S. David, P. Yin, S. Shamma, and W. Maass

Abstract:

A critical component of auditory processing is integrating information about sound features that change over time. Previous studies have shown that the context of a sound - the immediate history of auditory stimulation - can have a substantial effect on responses of auditory neurons to a current sound. In order to characterize these effects, we measured the information contained in the neural activity in primary auditory cortex (A1) about both current and preceding sounds. Neural recordings were made from single A1 neurons (n=122) isolated from 23 multi-channel recordings in 4 passively listening ferrets. The stimulus was a sequence of tones (150 ms duration). The frequency step between two consecutive tones was always half an octave up or down. For each neuron, we measured at particular points in time the mutual information (MI) between its response during a sliding window (20ms) and the identity of the current and preceding tone. Since direct estimates of MI from spike trains typically suffer from a systematic error (bias) due to the limited number of available response trials for a given stimulus, we used a recently proposed shuffling-based estimator with additional quadratic extrapolation bias correction (Panzeri et al., 2007). This method produces reliable information estimates for this particular setup. We found that most responses (102 out of 122 neurons) contained significant information about the stimulus throughout the duration of the tone. Of this information, on average, 60% was about the current tone, while 40% was about the previous tone. We also trained linear classifiers (Support Vector Machines with linear kernel) on the low-pass filtered response spike trains of multiple simultaneously recorded neurons (4-10) to discriminate between the two possible predecessors for a given tone. The performance the linear classifier can be viewed as a lower bound on the information contained in the responses about the previous tone. Performance of up to 80% was achieved. These results quantify the amount of information contained in the responses of A1 neurons about both currently and previously played tones and demonstrate that neurons in A1 integrate information about previous input into their current responses. References: Panzeri et al. (2007), J Neurophysiol, 98(3):1064

Reference: S. Klampfl, S. David, P. Yin, S. Shamma, and W. Maass. Integration of stimulus history in information conveyed by neurons in primary auditory cortex in response to tone sequences. 39th Annual Conference of the Society for Neuroscience, Program 163.8, Poster T6, 2009.