Dataset for: Effect of preceding stimulation on sound localization and its representation in the auditory midbrain

Prior stimulation can influence the perception of sound source location. Some psychophysical sound localization procedures differ in the amount of prior stimulation, which may affect measures of localization accuracy. If and how particularly the number of preceding stimuli affects sound localization and the neural representation of sound source position has not been investigated so far and will be the focus of the present report. We trained Mongolian gerbils in a left/right discrimination task where the target stimulus was preceded by silence or followed a number of reference stimuli. Localization thresholds decreased with the number of references presented before the target stimulus. The smallest thresholds were found after the presentation of a train of five reference stimuli and after silence. We recorded from units in the inferior colliculus (IC) of anaesthetised gerbils using virtual-acoustic space stimuli mimicking the ones used in the behavioral task and applied signal detection theory to compare behavioral and neurometric thresholds. We found that neurometric thresholds based on spike rate information of single units covered a wide range of threshold values but only neurometric thresholds based on responses of small populations of IC units reached consistently thresholds we also observed in the behavioral experiment. Unlike behavioral thresholds, however, neurometric thresholds were independent of the number of reference stimuli suggesting that processing stages downstream from the IC might better reflect the effect of prior stimulation

Dataset for: Release from informational masking by auditory stream segregation: Perception and its neural correlate

In the analysis of acoustic scenes we easily miss sounds or are insensitive to sound features that are salient if presented in isolation. This insensitivity that is not due to interference in the inner ear is termed informational masking (IM). So far, the cellular mechanisms underlying IM remained elusive. Here, we apply a sequential IM paradigm to humans and gerbils using a sound-level-increment-detection task determining the sensitivity to target tones in a background of standard (same frequency) and distracting tones (varying in level and frequency). The amount of IM that was indicated by the level-increment thresholds depended on the frequency separation between the distracting and the standard and target tones. In humans and gerbils we observed similar perceptual thresholds. A release from IM of more than 20 dB was observed in both species if the distracting tones were well segregated in frequency from the other tones. Neuronal rate responses elicited by similar sequences in gerbil inferior colliculus and auditory cortex were recorded. At both levels of the auditory pathway the neuronal thresholds obtained with a signal-detection theoretic approach deducing the sensitivity from the analysis of the neurons’ receiver operating characteristics matched the psychophysical thresholds revealing that IM already emerges at midbrain level. By applying objective response measures in physiology and psychophysics we demonstrated that the population of neurons has a sufficient sensitivity for explaining the perceptual level-increment thresholds indicating IM. There was a good correspondence between the neuronal and perceptual release from IM being related to auditory stream segregation