Auditory cortical and hippocampal local-field potentials to frequency deviant tones in urethane-anesthetized rats: An unexpected role of the sound frequencies themselves.
The human brain can automatically detect auditory changes, as indexed by the mismatch negativity of event-related potentials. The mechanisms that underlie this response are poorly understood. We recorded primary auditory cortical and hippocampal (dentate gyrus, CA1) local-field potentials to serial tones in urethane-anesthetized rats. In an oddball condition, a rare (deviant) tone (p=0.11) randomly replaced a repeated (standard) tone. The deviant tone was either lower (2200, 2700, 3200, 3700Hz) or higher (4300, 4800, 5300, 5800Hz) in frequency than the standard tone (4000Hz). In an equiprobability control condition, all nine tones were presented at random (p=0.11). Differential responses to deviant tones relative to the standard tone were found in the auditory cortex and the dentate gyrus but not in CA1. Only in the dentate gyrus, the responses were found to be standard- (i.e., oddball condition-) specific. In the auditory cortex, the sound frequencies themselves sufficed to explain their generation. These findings tentatively suggest dissociation among non-contextual afferent, contextual afferent and auditory change detection processes. Most importantly, they remind us about the importance of strict control of physical sound features in mismatch negativity studies in animals.
Department of Teacher Education/Rauma Unit, University of Turku, Seminaarinkatu 1, FI-26101 Rauma, Finland; Centre for Learning Research, University of Turku, 20014 Turku, Finland. Electronic address: timo.ruusuvirta@utu.fi.
Timo
T
Ruusuvirta
Department of Neurobiology, AIV Institute, Faculty of Health Sciences, University of Eastern Finland, P.O. Box 1627 (street address: Neulaniementie 2), FI-70211 Kuopio, Finland; Department of Psychology, University of Jyväskylä, P.O. Box 35 (street address: Ylistönmäentie 33), FI-40014 Jyväskylä, Finland.
Arto
A
Lipponen
Department of Psychology, University of Jyväskylä, P.O. Box 35 (street address: Ylistönmäentie 33), FI-40014 Jyväskylä, Finland.
Eeva-Kaarina
EK
Pellinen
Department of Psychology, University of Jyväskylä, P.O. Box 35 (street address: Ylistönmäentie 33), FI-40014 Jyväskylä, Finland.
Markku
M
Penttonen
Department of Psychology, University of Jyväskylä, P.O. Box 35 (street address: Ylistönmäentie 33), FI-40014 Jyväskylä, Finland.
Piia
P
Astikainen
D000161:Acoustic Stimulation; D000704:Analysis of Variance; D018686:Anesthetics, Intravenous / Q000494:pharmacology*; D000818:Animals; D001303:Auditory Cortex / Q000187:drug effects* / Q000502:physiology; D001307:Auditory Perception / Q000502:physiology*; D005072:Evoked Potentials, Auditory / Q000187:drug effects* / Q000502:physiology; D006624:Hippocampus / Q000187:drug effects* / Q000502:physiology; D011571:Psychoacoustics; D051381:Rats; D017207:Rats, Sprague-Dawley; D014520:Urethane / Q000494:pharmacology*
D018686:Anesthetics, Intravenous; D014520:Urethane
Acoustic frequency; Change detection; Hippocampus; Local-field potentials; Primary auditory cortex