David M. Senseman and Kay A. Robbins
University of Texas at San Antonio
Journal of Neuroscience 19:RC3:1-7, 1999
Abstract
The network behavior of cortical cells during the processing of a light flash was characterized in an isolated, but functionally intact, turtle visual system. Rapid changes in intracellular membrane potential were monitored optically using a voltage-sensitive dye (VSD). Spatially coherent changes in membrane potential were determined by subjecting high-speed movies of the VSD signals to Karhunen-Loéve decomposition. In all experimental trials analyzed (n > 50), coherent activity was restricted to a small number of similar spatial patterns or modes. At least four modes (M1,1, M1,2, M2,1, and M2,2) have an organizational structure similar to the normal modes of a vibrating membrane (drum). This empirical observation of modal activity provides a useful framework for analyzing the macroscopic behavior of cortical networks.Key words: cerebral cortex; visual cortex; pyramidal cell; neural network; voltage-sensitive dye; turtle
The six
QuickTime\256 movies listed below are appendix material for the paper which appeared
in the Rapid Communications of Journal of Neuroscience
(
www.neuroscience.org/cgi/content/full/19/10/RC3)
Movies #1 and Movie #2
Each of these movies presents a side-by-side comparison of an original data set with a data set computed from the contributions of the three most important modes (M1,1, M1,2, and M2,1). These movies illustrate the fidelity with which a low-dimensional modal representation reproduces the behavior observed in the original data set.
Movie 1: shows a response evoked in
the right cortex and corresponds to the data presented in Fig. 1A of the article
(experiment Cor3207).
Movie 2: shows a response evoked in the left cortex and corresponds to the data presented in Fig. 1B of the article (experiment Cor3404). In both cases, the visual stimulus was a brief, diffuse light flash presented to the contralateral eyecup at 0 ms. Please note that in Movie #1 (but not in Movie #2), the orientation of the cortical tissue is rotated 180o in the movie relative to its orientation in Fig. 1A. In Movie #1 rostral is towards the bottom of the picture while dorsomedial is to the left. In Movie #2 (and all other movies), rostral is towards the top of the screen and dorsomedial is to the left.
Movies #3 through Movie #6
Movie #3 through Movie #6 compare the time signatures of responses in the same preparation to different types of visual stimuli. Trial Cor3404 of Fig. 1B is used as a reference for each comparison. These movies correspond to the data presented in Fig. 4 of the article:
Movie 3: Red diffuse versus white diffuse
Movie 4: Spot nasal versus white diffuse
Movie 5: Spot temporal versus white diffuse
Movie 6: Spot temporal versus white diffuse (alternative view)