Auditory neuroscience: neuronal sensitivity in humans

Abstract

Microelectrode recordings from the human auditory cortex suggest that the tuning of individual neurons can account for sound frequency discrimination thresholds and that this tuning varies in a context-dependent fashion with the type of sound used to measure it.

Figure 1. Probing the frequency selectivity of neurons in the auditory cortex.

(A) Example of a ‘random chord’ sound stimulus. Random chords consist of numerous brief tone pips presented at random time intervals. The sound spectrogram is shown beneath the stimulus waveform. ‘Warm’ (yellow and red) colors in the spectrogram indicate high sound intensities at the times and frequencies shown on the x- and y-axes, respectively. (B) The spec-tro-temporal receptive field (STRF) of a single neuron in the human auditory cortex, estimated by reverse correlation with the random chord stimuli. In the STRF, warm colors show which frequencies excite the neuron and over what time course. (C) Example of a ‘sound track’ stimulus, consisting of a human speech dialogue against faint background music. (D) STRF of the same neuron shown in B, but this time recorded with the sound-track stimulus. Note that the neuron’s frequency tuning adapts to the stimulus and becomes broader (based on data in Bitterman et al. [1]).