Document Detail


A comparison of monaural and binaural responses to frequency modulated (FM) sweeps in cat primary auditory cortex.
MedLine Citation:
PMID:  1483517     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
Monaural and binaural single unit responses to frequency-modulated (FM) sweeps were compared in cat primary auditory cortex (AI). Both upward-directed (changing from low to high frequency) and downward-directed (changing from high to low frequency) FM sweeps were presented monaurally and binaurally at five rates of frequency modulation (referred to here as the speed of FM sweep). Two types of binaural FM sweep conditions were presented: (1) like-directed FM sweeps, in which identical FM sweeps were presented to both ears, and (2) opposite-directed FM sweeps, in which one ear was presented with one direction of FM sweep while the other ear was simultaneously presented with the opposite direction of FM sweep. In a sample of 78 cells, 33 cells were classified as EE (binaural facilitatory) and 45 were classified as EI (binaural inhibitory). Ninety-four percent of all units were sensitive to the direction and/or speed of FM sweeps. In general, under binaural stimulus conditions, EE cells responded optimally to like-directed FM sweeps, while EI cells preferred opposite-directed FM sweeps. When tested monaurally, 59% of all cells (both EE and EI) were direction selective, with the majority (76%) preferring downward-directed FM sweeps. When tested binaurally, most direction selective EE cells (60%) preferred upward-directed FM sweeps, while the majority of direction selective EI cells (71%) preferred downward-directed FM sweeps. Our analysis also allowed us to classify inhibitory responses of EI cells as either direction selective (37%) or non-direction selective (63%). For FM speed selectivity under monaural conditions, most EE cells preferred fast FM sweep rates (0.4-0.8 kHz/ms), while approximately equal numbers of EI cells preferred either slow (i.e., 0.05-0.1 kHz/ms) or fast (i.e., 0.4-0.8 kHz/ms) speeds. Under binaural conditions, the majority of EE and EI cells responded best to high speeds when tested with like-directed FM sweeps, while the preferred speed with opposite-directed FM sweeps was more broadly tuned. The results suggest the presence of binaural neural mechanisms underlying cortical FM sweep direction and speed selectivity.
Authors:
J R Mendelson; K L Grasse
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Publication Detail:
Type:  Comparative Study; Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Experimental brain research. Experimentelle Hirnforschung. Expérimentation cérébrale     Volume:  91     ISSN:  0014-4819     ISO Abbreviation:  Exp Brain Res     Publication Date:  1992  
Date Detail:
Created Date:  1993-02-16     Completed Date:  1993-02-16     Revised Date:  2009-11-11    
Medline Journal Info:
Nlm Unique ID:  0043312     Medline TA:  Exp Brain Res     Country:  GERMANY    
Other Details:
Languages:  eng     Pagination:  435-54     Citation Subset:  IM    
Affiliation:
Division of Life Sciences, University of Toronto, Scarborough, Ontario, Canada.
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MeSH Terms
Descriptor/Qualifier:
Acoustic Stimulation*
Animals
Auditory Cortex / cytology,  physiology*
Auditory Threshold*
Cats
Microelectrodes
Neural Inhibition
Neurons, Afferent / physiology

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine


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