What can anesthesia teach us about the functional architecture of visual cortex
While it is clear that data obtained from awake subjects are indispensible for understanding mental function, we cannot hope to understand awareness or indeed any facet of cognition and perception without understanding non conscious states. This stands to reason from a modeling (dynamical systems) point of view - without understanding the link between global parameters (which presumably underlie transitions in states of awareness/vigilance) and neural dynamics (especially in sustaining and effectuating transitions of disparate states such as sleep), it is hard to see how one can hope to formulate adequate models for the brain. In this regard, counter to current sentiment, the anesthetized state affords a unique window for studying core facets of neuronal networks, such as the connectivity patterns between cortical columns, as the system in effect is oblivious to input both external and internal, yet can be locked in stereotypical dynamics. This line of thought was put to test through analysis of anesthetized v1 data in cat:
Previously it was found that under anesthesia a striking phenomena can be observed in cat primary visual cortex - the emergence of spontaneous patterns of activity resembling orientation maps. To better understand the extent and origin of such patterns, Voltage sensitive dye imaging (VSDI) data were collected bilaterally from primary visual cortex of anesthetized cats. Bilateral activation patterns resembling orientation maps were observed, and further analysis showed that both hemispheres behave as one in this regard. Using a straight forward neural mass model we found that the salient features of these data could be captured. Our model in conjunction with the data suggest the following: Callosal connections are fast, exact (orientation specific), and of a similar magnitude in terms of synaptic efficacy to lateral connections within v1 . Spontaneously occurring maps could be explained by noise driven dynamics in conjunction with disrupted balance between excitation and inhibition. Under such conditions map like patterns form a ring like structure of transiently attracting states. Finally, "feature maps" appear to be the eigen modes of the synaptic matrix (i.e. patterns of covariance in the synaptic connections between columns), and as such their ordering determines the saliency of these features for upstream processing.
Keywords:
VSDI,
voltage sensitive dye,
V1,
Neural Mass Models,
spontaneous activity,
orientation selectivity,
cortical columns,
cortical maps
Conference:
Second Belgian Neuroinformatics Congress, Leuven, Belgium, 4 Dec - 4 Dec, 2015.
Presentation Type:
Poster Presentation
Topic:
Methods and Modeling
Citation:
Fekete
T and
Van Leeuwen
C
(2015). What can anesthesia teach us about the functional architecture of visual cortex.
Front. Neuroinform.
Conference Abstract:
Second Belgian Neuroinformatics Congress.
doi: 10.3389/conf.fninf.2015.19.00025
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Received:
14 Nov 2015;
Published Online:
17 Nov 2015.
*
Correspondence:
Dr. Tomer Fekete, KU Leuven, Leuven, 3000, Belgium, tomer.fekete@mail.huji.ac.il