Changes in the complex permittivity during spreading depression in rat cortex.
With recent developments in current density imaging (CDI), it is feasible to utilize this new technique in brain imaging applications. Since CDI's ability to measure changes in current density depends on a concomitant activity-dependent change in the conductivity of the brain tissue, we have examined the changes in complex conductivity during spreading depression (SD) in rodent neocortex using a coaxial probe. SD was chosen because it is often referred to as an animal model of cerebral ischemia and migraine with aura. The conductivity measurements revealed a change with short latency (30-60 s) followed by a change with a longer latency (200-300 s). This change in conductivity with short latency has not been reported before, and we conjecture that it may be the priming or triggering mechanism prior to the main SD episode. A 20% change in conductivity during SD is sufficiently large to be measured by CDI. Therefore, the ability to measure changes in the conductivity, as opposed to metabolic changes, makes CDI a viable approach to the study of ischemia and migraine with aura.
Yoon
R S
RS
Department of Electrical and Computer Engineering, University of Toronto, Ont., Canada. ryoon@ecf.utoronto.ca
Czaya
A
A
Kwan
H C
HC
Joy
M L
ML
D000818:Animals; D002545:Brain Ischemia / Q000503:physiopathology; D002540:Cerebral Cortex / Q000502:physiology*; D013181:Cortical Spreading Depression / Q000502:physiology*; D004195:Disease Models, Animal; D004553:Electric Conductivity; D004567:Electrodes, Implanted; D004569:Electroencephalography / Q000295:instrumentation / Q000379:methods / Q000706:statistics & numerical data; D020325:Migraine with Aura / Q000503:physiopathology; D051381:Rats; D017208:Rats, Wistar; D011930:Reaction Time / Q000502:physiology; D013997:Time Factors