A joint project of the Graduate School, Peabody College, and the Jean & Alexander Heard Library

Title page for ETD etd-12032007-154530


Type of Document Dissertation
Author Zhou, Zhiyi
URN etd-12032007-154530
Title Spatial characteristics of cooperative interactions in the striate cortex.
Degree PhD
Department Biomedical Engineering
Advisory Committee
Advisor Name Title
A. B. Bonds Committee Chair
Jon H. Kass Committee Member
Joseph S. Lappin Committee Member
Peter Konrad Committee Member
Richard G. Shiavi Committee Member
Keywords
  • Gamma Oscillation
  • Coherence
  • Visual cortex -- Physiology
  • Neural Coding
  • Synchrony
  • Synchronization
  • Visual perception -- Physiological aspects
Date of Defense 2007-11-16
Availability unrestricted
Abstract
In a complex visual scene, different objects with specific features are presented in combinations, which raises the question of how the visual system processes and represents structure in the huge amount of visual information that it receives every moment. Besides independent response rate modulation, which has been traditionally considered to be the primary coding mechanism in the visual system, correlated neural responses in the form of synchronized neural firing have been proposed as providing a versatile means of encoding. In this dissertation, the role of neural correlation in visual perception was explored by analyzing synchronized responses in cat primary visual cortex.

We first tested the neural response to collinear and cocircular contours and found that the strength of synchrony between cells is not only affected by the receptive field properties but also determined by the effectiveness of the visual stimulus in driving cells. Synchrony was found to be more reliable for detecting cocircular contours than the independent firing rate, suggesting that contour integration through neural synchrony could start as early as in the lowest level of visual cortex. We then explored the relationship between spike timing synchronization and coherent frequency oscillation. Strong correlation between cross-correlation analysis and coherence analysis suggests synchrony and coherence are internally related, though these two estimates reflect neural connectivity from different perspectives. By systematically perturbing the timing accuracy in neural responses, we also discovered that the temporal structures of spike trains are important in maintaining neural correlation. We last studied how the synchronized neural response modulates with the change of spatial integrity in visual stimulation. We found that the general association between neural spike trains depends strongly on spatial integrity, with coherence in the gamma band showing greater sensitivity to the change of spatial structure than other frequency bands. Temporal integrity, and not spatial integrity, generates synchrony; spatial integrity however is critical in triggering subsequent gamma band synchronization.

Files
  Filename       Size       Approximate Download Time (Hours:Minutes:Seconds) 
 
 28.8 Modem   56K Modem   ISDN (64 Kb)   ISDN (128 Kb)   Higher-speed Access 
  Thesis.pdf 1.75 Mb 00:08:06 00:04:10 00:03:38 00:01:49 00:00:09

Browse All Available ETDs by ( Author | Department )

If you have more questions or technical problems, please Contact LITS.