Impedance Tomography of Aplysia Abdominal Ganglion
Using Multichannel Micro-electrode Arrays


Collaborator: Dr. Rosalind Sadleir

Abstract - For years, researchers have studied impedance changes in neural tissue resulting from increased neuronal activity. Here, we explore this relationship using voltages recorded on a 60-channel micro-electrode array. Specifically, we show that increased action potential firing events (spikes) produced changes in the average impedance of the tissue. In each trial, changes in the amplitude of a sinusoidal carrier wave caused by an injected subthreshold current were analyzed in order to determine these impedance changes. Higher frequency data, obtained after the carrier wave was removed, were analyzed to determine the location and frequency of spike events. We here validate the utility of the 60-channel micro-electrode array for this purpose and outline future, more detailed experiments.



impedance_system
Schematic representation of recording and stimulation system used to study impedance changes during neural activity of an Aplysia abdominal ganglion.

aplysiaaplysiaCNS
Aplysia Californica and schmatic diagram of neural system. The abdominal ganlion mediates the response to tactile stimulation of the siphon or mantle shelf which produces a characteristic withdrawl response often studied for the effects of sensitization and habituation.

imped_waveform


Example of a spike during 1.2 seconds of baseline recordings (top), during application of the 10 A current source (middle), and following application of the LMS filter (bottom panel).