Cerebral Cortex Advance Access published online on March 28, 2004
Cerebral Cortex, doi:10.1093/cercor/bhh019
© 2004 by Oxford University Press
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
1 Department of Neurobiology, Weizmann Institute of Science, Rehovot 76100, Israel
* To whom correspondence should be addressed. E-mail: rafi.malach{at}weizmann.ac.il.
To what extent does neural activation in human visual cortex follow the temporal dynamics of the optical retinal stimulus? Specifically, to what extent does stimulus evoked neural activation persist after stimulus termination? In the present study, we used functional magnetic resonance imaging (fMRI) to explore the resulting temporal non-linearities across the entire constellation of human visual areas. Gray-scale images of animals, houses and faces were presented at two different presentation rates -- 1 and 4 Hz -- and the fMRI signal was analyzed in retinotopic and in high order occipito-temporal visual areas. In early visual areas and the motion sensitive area MT/V5, a fourfold increase in stimulus presentation rate evoked a twofold increase in signal amplitude. However, in high order visual areas, signal amplitude increased only by 25%. A control experiment ruled out the possibility that this difference was due to signal saturation (‘ceiling’) effects. A likely explanation for the stronger non-linearities in occipito-temporal cortex is a persistent neuronal activation that continues well after stimulus termination in the 1 Hz condition. These persistent activations might serve as a short term (iconic) memory mechanism for preserving a trace of the stimulus even in its absence and for future integration with temporally correlated stimuli. Two alternative models of persistence (inhibitory and excitatory) are proposed to explain the data. Key Words:
fMRI, short-term memory, visual cortex
Article
Enhanced Temporal Non-linearities in Human Object-related Occipito-temporal Cortex
2 Functional Brain Imaging Unit Tel Aviv Sourasky Medical Center, Tel Aviv 64239, Israel; Faculty of Medicine, Tel Aviv University, Tel Aviv 69978, Israel
Abstract 
CiteULike 
Connotea 
Del.icio.us What's this?
This article has been cited by other articles:
|
|
 |
|
  R. Q. Quiroga, R. Mukamel, E. A. Isham, R. Malach, and I. Fried Human single-neuron responses at the threshold of conscious recognition PNAS, March 4, 2008; 105(9): 3599 - 3604. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 T. J. McKeeff, D. A. Remus, and F. Tong Temporal Limitations in Object Processing Across the Human Ventral Visual Pathway J Neurophysiol, July 1, 2007; 98(1): 382 - 393. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
M.-E. Large, A. Aldcroft, and T. Vilis Perceptual Continuity and the Emergence of Perceptual Persistence in the Ventral Visual Pathway J Neurophysiol, June 1, 2005; 93(6): 3453 - 3462. [Abstract] [Full Text] [PDF]
|
|