Document Detail

MedLine Citation:
PMID:  3195064     Owner:  NLM     Status:  MEDLINE    
Bisection thresholds are approximately proportional to the separation/eccentricity of the targets. This "Weber's law" for position has been invoked over the past century. It is the separation of the reference targets, or their eccentricity which determines the threshold? In previous studies separation and eccentricity are confounded. In the present report we have pitted separation against eccentricity. Bisection thresholds were measured for stimuli presented on an isoeccentric arc, so that separation could be varied while holding the eccentricity of the test lines constant. We used a 5-fold range of separations from 2-10 deg. In this regime, the present results provide strong evidence against Weber's law. When separation is varied but eccentricity held constant, there is no Weber's law. Rather the thresholds are approximately constant. Our results suggest that the judgement of the separation of widely separated objects is similar to a distance measurement using a ruler on the cortex, in that the error of measurement is independent of the separation between objects. The results imply that when we attempt to gauge the distance between widely separated objects it is unlikely that we do so on the basis of the outputs of large spatial filters; rather it appears that we make such judgements by estimating the cortical distance which separates the targets of interest.
D M Levi; S A Klein; Y L Yap
Related Documents :
11934004 - Temporal dynamics of reflexive attention shifts: a dual-stream rapid serial visual pres...
15924244 - When are neighbours hostile? inhibitory neighbour effects in visual word recognition.
20565174 - Reflections on blindsight: neuroimaging and behavioural explorations clarify a case of ...
16043854 - Binocular summation of detection and resolution thresholds in the central visual field ...
21721854 - Varying the length of dim nocturnal illumination differentially affects the pacemaker c...
7774544 - How the horse moves: 1. significance of graphical representations of equine forelimb ki...
Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't; Research Support, U.S. Gov't, P.H.S.    
Journal Detail:
Title:  Vision research     Volume:  28     ISSN:  0042-6989     ISO Abbreviation:  Vision Res.     Publication Date:  1988  
Date Detail:
Created Date:  1988-12-28     Completed Date:  1988-12-28     Revised Date:  2007-11-14    
Medline Journal Info:
Nlm Unique ID:  0417402     Medline TA:  Vision Res     Country:  ENGLAND    
Other Details:
Languages:  eng     Pagination:  597-603     Citation Subset:  IM; S    
University of Houston, College of Optometry, TX 77004.
Export Citation:
APA/MLA Format     Download EndNote     Download BibTex
MeSH Terms
Depth Perception / physiology*
Perceptual Masking / physiology
Sensory Thresholds / physiology
Visual Acuity
Visual Fields
Grant Support

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

Previous Document:  IRBP-like proteins in the eyes of six cephalopod species--immunochemical relationship to vertebrate ...
Next Document:  Light spread and scatter from some common adapting stimuli: computations based on the point-source l...