title: Neurons in the inferior colliculus of the rat show stimulus-specific adaptation for frequency, but not for intensity.
abstract: Electrophysiological and psychophysical responses to a low-intensity probe sound tend to be suppressed by a preceding high-intensity adaptor sound. Nevertheless, rare low-intensity deviant sounds presented among frequent high-intensity standard sounds in an intensity oddball paradigm can elicit an electroencephalographic mismatch negativity (MMN) response. This has been taken to suggest that the MMN is a correlate of true change or "deviance" detection. A key question is where in the ascending auditory pathway true deviance sensitivity first emerges. Here, we addressed this question by measuring low-intensity deviant responses from single units in the inferior colliculus (IC) of anesthetized rats. If the IC exhibits true deviance sensitivity to intensity, IC neurons should show enhanced responses to low-intensity deviant sounds presented among high-intensity standards. Contrary to this prediction, deviant responses were only enhanced when the standards and deviants differed in frequency. The results could be explained with a model assuming that IC neurons integrate over multiple frequency-tuned channels and that adaptation occurs within each channel independently. We used an adaptation paradigm with multiple repeated adaptors to measure the tuning widths of these adaption channels in relation to the neurons' overall tuning widths.
authors.affiliation: Auditory Neuroscience Laboratory, Institute of Neuroscience of Castilla y León (INCYL), University of Salamanca, Salamanca 37007, Spain.
authors.forename: Daniel
authors.initials: D
authors.lastname: Duque
authors.affiliation: Auditory Neuroscience Laboratory, Institute of Neuroscience of Castilla y León (INCYL), University of Salamanca, Salamanca 37007, Spain.
authors.forename: Xin
authors.initials: X
authors.lastname: Wang
authors.affiliation: Auditory Neuroscience Laboratory, Institute of Neuroscience of Castilla y León (INCYL), University of Salamanca, Salamanca 37007, Spain.
authors.forename: Javier
authors.initials: J
authors.lastname: Nieto-Diego
authors.affiliation: MRC Institute of Hearing Research, University Park, Nottingham, NG7 2RD, UK.
authors.forename: Katrin
authors.initials: K
authors.lastname: Krumbholz
authors.affiliation: Auditory Neuroscience Laboratory, Institute of Neuroscience of Castilla y León (INCYL), University of Salamanca, Salamanca 37007, Spain.|Department of Cell Biology and Pathology, Faculty of Medicine, University of Salamanca, Campus Miguel de Unamuno, 37007, Salamanca, Spain.|Salamanca Institute for Biomedical Research (IBSAL), Salamanca, Spain.
authors.forename: Manuel S
authors.initials: MS
authors.lastname: Malmierca
mesh_terms: D000222:Adaptation, Physiological; D000818:Animals; D055724:Electrophysiological Phenomena; D005260:Female; D007245:Inferior Colliculi / Q000502:physiology*; D009474:Neurons / Q000502:physiology*; D011571:Psychoacoustics; D020318:Rats, Long-Evans; D013016:Sound