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Voltage-sensitive-dye imaging of microstimulation-evoked neural activity through intracortical horizontal and callosal connections in cat visual cortex

Jun Suzurikawa1,6, Toshiki Tani2,7, Masayuki Nakao3, Shigeru Tanaka2 and Hirokazu Takahashi1,4,5,7

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Recently, intrinsic signal optical imaging has been widely used as a routine procedure for visualizing cortical functional maps. We do not, however, have a well-established imaging method for visualizing cortical functional connectivity indicating spatio-temporal patterns of activity propagation in the cerebral cortex. In the present study, we developed a novel experimental setup for investigating the propagation of neural activities combining the intracortical microstimulation (ICMS) technique with voltage sensitive dye (VSD) imaging, and demonstrated the feasibility of this setup applying to the measurement of time-dependent intra- and inter-hemispheric spread of ICMS-evoked excitation in the cat visual cortices, areas 17 and 18. A microelectrode array for the ICMS was inserted with a specially designed easy-to-detach electrode holder around the 17/18 transition zones (TZs), where the left and right hemispheres were interconnected via the corpus callosum. The microelectrode array was stably anchored in agarose without any holder, which enabled us to visualize evoked activities even in the vicinity of penetration sites as well as in a wide recording region that covered a part of both hemispheres. The VSD imaging could successfully visualize ICMS-evoked excitation and subsequent propagation in the visual cortices contralateral as well as ipsilateral to the ICMS. Using the orientation maps as positional references, we showed that the activity propagation patterns were consistent with previously reported anatomical patterns of intracortical and interhemispheric connections. This finding indicates that our experimental system can serve for the investigation of cortical functional connectivity.


PACS

87.80.-y Biophysical techniques (research methods)

87.19.L- Neuroscience

87.19.R- Mechanical and electrical properties of tissues and organs

42.66.Ew Physiology of eye; optic-nerve structure and function

Subjects

Instrumentation and measurement

Optics, quantum optics and lasers

Medical physics

Biological physics

Dates

Issue 6 (December 2009)

Received 7 August 2009, accepted for publication 3 September 2009

Published 1 October 2009



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