Document Detail

Event-related potentials to omitted visual stimuli in a reptile.
MedLine Citation:
PMID:  7517844     Owner:  NLM     Status:  MEDLINE    
Visual omitted stimulus potentials (OSPs) were recorded from awake pond turtles with arrays of 3-20 electrodes in the dorsal cortex (DC), dorsal ventricular ridge (DVR) and optic tectum. Since they are generally longer in duration than the interstimulus interval (ISI), the standard experiment is a short conditioning train of regular light or dark flashes (1-20 Hz) whose termination elicits the OSP. Tectal surface OSPs after trains > 7 Hz have 2 major positive peaks, P120-140 and P220-250 after the due-time of the first omission; after < 7 Hz down to the minimum of 1.5 Hz only the slower peak appears. Some deep tectal loci also have one to three 100 msec wide negative waves peaking at variable times from 200 to 1300 msec. Forebrain OSPs in DC and DVR are approximately 30 msec later and often include induced 17-25 Hz oscillations, not phase-locked and attenuated in averages. Both tectal and forebrain OSP main waves tend toward a constant latency after the due-time, over a wide range of ISIs, as though the system expects a stimulus on schedule. Jitter of ISI around the mean does not greatly reduce the OSP. At all loci higher conditioning rates cause the amplitudes of the steady state response (SSR) VEPs to decline and of the OSPs to increase. Some similarities and correlations of regional amplitude fluctuations between OSPs and VEPs are noted. The OSP dynamics are consistent with the hypothesis of a postinhibitory rebound of temporally specific VEP components increasingly inhibited with higher stimulation rates; much of this response is retinal but each higher brain level further modulates. OSPs in this reptile are similar to those known in fish and to the "high frequency" type in humans, quite distinct in properties from the "low frequency" OSPs. It will be important to look at the high frequency type in laboratory mammals to determine whether they are present in the midbrain and retina, as in fish and reptiles.
J C Prechtl; T H Bullock
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Publication Detail:
Type:  Journal Article; Research Support, U.S. Gov't, P.H.S.    
Journal Detail:
Title:  Electroencephalography and clinical neurophysiology     Volume:  91     ISSN:  0013-4694     ISO Abbreviation:  Electroencephalogr Clin Neurophysiol     Publication Date:  1994 Jul 
Date Detail:
Created Date:  1994-08-10     Completed Date:  1994-08-10     Revised Date:  2008-09-09    
Medline Journal Info:
Nlm Unique ID:  0375035     Medline TA:  Electroencephalogr Clin Neurophysiol     Country:  IRELAND    
Other Details:
Languages:  eng     Pagination:  54-66     Citation Subset:  IM    
Neurobiology Unit, Scripps Institution of Oceanography, La Jolla, CA.
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MeSH Terms
Brain / physiology*
Evoked Potentials, Visual / physiology*
Photic Stimulation / methods
Reaction Time / physiology
Turtles / physiology*

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