Computational principles of neural adaptation for binaural signal integration
Fig 4
Left column: stimuli and results of the adapter tone experiment 3. Right column: results of the timing experiment 4. (A) input stimulus example for Experiment 4. The first ridge depicts the ILD of the adapter tone with a duration of 1.2s followed by a break of 500ms. The second ridge shows the ILD of the actual test stimulus. Differently shaded areas illustrate different test stimulus ILDs for the same adapter tone. Grey dashed line marks 0dB ILD. (B) Responses of model neuron to different adapter tone intensities. Blue 40dB, orange 20dB, green 0dB and constant test stimulus intensity (40dB). The response of the neuron to an adapter tone sound level of 40dB (blue line) is maximal. However, the responses to the consecutive test stimuli is reduced through adaptation i.e. the higher the ILD of the adapter tone the lower the response to the test stimulus. (C) Response of a single LSO neuron to stimuli of constant ILD after the presentation of various adapter tone ILDs. Light blue dashed line depicts the response to a test stimulus of ILD 40dB after presenting an adapter ILD of 0dB. Dark blue line draws the response to the same test stimulus after presenting an adapter ILD of −40dB. No adaptation takes place and the response is similar to the default response of the neuron (compare Fig 2B). Light blue line draws the attenuated response to the same test stimulus after presenting an adapter ILD of 40dB. (D) Responsiveness of LSO neuron for different ILDs over ITDs. The blue line indicates the neuron response for 0dB level difference, the darker blue area shows possible responses for higher ILD values, whereas the light blue area indicates possible responses for negative ILD values. The depicted ILD range is limited to −20dB and + 20dB for a clearer plot. Note the u-shape (dark blue) and v-shape (light blue) response curves. (E) Neuron responses over various ITD and ILD values. (F) Adaptation range of model LSO neuron for various ITDs of the input signals. Light blue line and corresponding filled area indicates model response for stimuli with positive ITDs. Dark blue area shows responses for stimuli with negative ITDs. Area filled with blue is inferred from simulation results.