HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) CME: Take the course for this article: Volume 56, Number 8, April 24, 2001 Correspondence: Submit a response Alert me when this article is cited Alert me when Correspondence are posted Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Meador, K. J. Articles by Loring, D. W. Search for Related Content PubMed PubMed Citation Articles by Meador, K. J. Articles by Loring, D. W.

Relationship of extinction to perceptual thresholds for single stimuli

From the Section of Behavioral Neurology, Department of Neurology, Medical College of Georgia, Augusta.

Address correspondence and reprint requests to Dr. K.J. Meador, Section of Behavioral Neurology, Department of Neurology, Medical College of Georgia, 1120 15 St. (BA3410), Augusta, GA 30912-3280; e-mail: kmeador{at}neuro.mcg.edu

OBJECTIVE: To demonstrate the effects of target stimulus intensity on extinction to double simultaneous stimuli.

BACKGROUND: Attentional deficits contribute to extinction in patients with brain lesions, but extinction (i.e., masking) can also be produced in healthy subjects. The relationship of extinction to perceptual thresholds for single stimuli remains uncertain.

METHODS: Brief electrical pulses were applied simultaneously to the left and right index fingers of 16 healthy volunteers (8 young and 8 elderly adults) and 4 patients with right brain stroke (RBS). The stimulus to be perceived (i.e., target stimulus) was given at the lowest perceptual threshold to perceive any single stimulus (i.e., Minimal) and at the threshold to perceive 100% of single stimuli. The mask stimulus (i.e., stimulus given to block the target) was applied to the contralateral hand at intensities just below discomfort.

RESULTS: Extinction was less for target stimuli at 100% than Minimal threshold for healthy subjects. Extinction of left targets was greater in patients with RBS than elderly control subjects. Left targets were extinguished less than right in healthy subjects. In contrast, the majority of left targets were extinguished in patients with RBS even when right mask intensity was reduced below right 100% threshold for single stimuli. RBS patients had less extinction for right targets despite having greater left mask - threshold difference than control subjects. In patients with RBS, right "targets" at 100% threshold extinguished left "masks" (20%) almost as frequently as left masks extinguished right targets (32%).

CONCLUSIONS: Subtle changes in target intensity affect extinction in healthy adults. Asymmetries in mask and target intensities (relative to single-stimulus perceptual thresholds) affect extinction in RBS patients less for left targets but more for right targets as compared with control subjects.

This article has been cited by other articles:

				B. M. Kluger, K. J. Meador, C. W. Garvan, D. W. Loring, D. T. Townsend, and K. M. Heilman A TEST OF THE MECHANISMS OF SENSORY EXTINCTION TO SIMULTANEOUS STIMULATION Neurology, April 29, 2008; 70(18): 1644 - 1645. [Full Text] [PDF]