title: Learning auditory space: generalization and long-term effects.
abstract: BACKGROUND
  Previous findings have shown that humans can learn to localize with altered auditory space cues. Here we analyze such learning processes and their effects up to one month on both localization accuracy and sound externalization. Subjects were trained and retested, focusing on the effects of stimulus type in learning, stimulus type in localization, stimulus position, previous experience, externalization levels, and time.
  
  
  METHODS
  We trained listeners in azimuth and elevation discrimination in two experiments. Half participated in the azimuth experiment first and half in the elevation first. In each experiment, half were trained in speech sounds and half in white noise. Retests were performed at several time intervals: just after training and one hour, one day, one week and one month later. In a control condition, we tested the effect of systematic retesting over time with post-tests only after training and either one day, one week, or one month later.
  
  
  RESULTS
  With training all participants lowered their localization errors. This benefit was still present one month after training. Participants were more accurate in the second training phase, revealing an effect of previous experience on a different task. Training with white noise led to better results than training with speech sounds. Moreover, the training benefit generalized to untrained stimulus-position pairs. Throughout the post-tests externalization levels increased. In the control condition the long-term localization improvement was not lower without additional contact with the trained sounds, but externalization levels were lower.
  
  
  CONCLUSIONS
  Our findings suggest that humans adapt easily to altered auditory space cues and that such adaptation spreads to untrained positions and sound types. We propose that such learning depends on all available cues, but each cue type might be learned and retrieved differently. The process of localization learning is global, not limited to stimulus-position pairs, and it differs from externalization processes.
authors.affiliation: Cluster of Excellence Hearing4all, Carl Von Ossietzky University of Oldenburg, Oldenburg, Germany ; Department of Signal Processing and Acoustics, Aalto University, Espoo, Finland ; Centro Algoritmi, School of Engineering, University of Minho, Guimarães, Portugal.
authors.forename: Catarina
authors.initials: C
authors.lastname: Mendonça
authors.forename: Guilherme
authors.initials: G
authors.lastname: Campos
authors.forename: Paulo
authors.initials: P
authors.lastname: Dias
authors.forename: Jorge A
authors.initials: JA
authors.lastname: Santos
mesh_terms: D000222:Adaptation, Physiological / Q000502:physiology*; D000328:Adult; D005260:Female; D006801:Humans; D007858:Learning / Q000502:physiology*; D008297:Male; D008875:Middle Aged; D013017:Sound Localization / Q000502:physiology*; D013997:Time Factors