| Local and global limitations on direction integration assessed using equivalent noise analysis. | |
| | |
MedLine Citation:
|
PMID: 16171844 Owner: NLM Status: MEDLINE |
Abstract/OtherAbstract:
|
We used an equivalent noise (EN) paradigm to examine how the human visual system pools local estimates of direction across space in order to encode global direction. Observers estimated the mean direction (clockwise or counter-clockwise of vertical) of a field of moving band-pass elements whose directions were drawn from a wrapped normal distribution. By measuring discrimination thresholds for mean direction as a function of directional variance, we were able to infer both the precision of observers' representation of each element's direction (i.e., local noise) as well as how many of these estimates they were averaging (i.e., global pooling). We estimated EN for various numbers of moving elements occupying regions of various sizes. We report that both local and global limits on direction integration are determined by the number of elements present in the display (irrespective of their density or the size of region they occupy), and we go on to show how this dependence can be understood in terms of neural noise. Specifically, we use Monte Carlo simulations to show that a maximum-likelihood operator, operating on pooled directional signals from visual cortex corrupted by Poisson noise, accounts for psychophysical data across all conditions tested, as well as motion coherence thresholds (collected under similar experimental conditions). A population vector-averaging scheme (essentially a special case of ML estimation) produces similar predictions but out-performs subjects at high levels of directional variability and fails to predict motion coherence thresholds. |
| | |
Authors:
|
Steven C Dakin; Isabelle Mareschal; Peter J Bex |
Related Documents
:
|
21045564 - Rostral migratory stream neuroblasts turn and change directions in stereotypic patterns. 8917784 - Responses of complex cells in area 17 of the cat to bi-vectorial transparent motion. 10789424 - Speed tuning of motion segmentation and discrimination. 18195864 - Influence of the atmosphere on space measurements of directional properties. 9893834 - Shift in rayleigh matches after adaptation to monochromatic light of various intensities. 21352394 - Neural mechanism of atrial fibrillation: insight from global high density frequency map... |
Publication Detail:
|
Type: Journal Article; Research Support, Non-U.S. Gov't |
Journal Detail:
|
Title: Vision research Volume: 45 ISSN: 0042-6989 ISO Abbreviation: Vision Res. Publication Date: 2005 Nov |
Date Detail:
|
Created Date: 2005-10-03 Completed Date: 2006-02-09 Revised Date: 2006-11-15 |
Medline Journal Info:
|
Nlm Unique ID: 0417402 Medline TA: Vision Res Country: England |
Other Details:
|
Languages: eng Pagination: 3027-49 Citation Subset: IM |
Affiliation:
|
Department of Visual Science, Institute of Ophthalmology, University College London, 11-43 Bath Street, London EC1V 9EL, UK. s.dakin@ucl.ac.uk |
Export Citation:
|
APA/MLA Format Download EndNote Download BibTex |
| MeSH Terms | |
Descriptor/Qualifier:
|
Discrimination (Psychology)
/
physiology* Humans Motion Perception / physiology* Pattern Recognition, Visual / physiology* |
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine
Previous Document: Dynamics of cross- and iso-surround facilitation suggest distinct mechanisms.
Next Document: Imaging of nitric oxide in the retina.