• Study the effects of natural or artificially induced rhythmic slow-wave activity.

• Easily examine rhythmic activity of brain regions from 64 recording electrodes

• Investigate the mechanisms generating hippocampal g, b and q rhythms

• Use advanced techniques such as current source density (CSD) analysis and online Fourier transforms to study intra- and inter-regional processes

• Generate two-dimensional current source density (CSD) movies automatically

Example 1: Carbachol-Induced Oscillations

(A) Carbachol-induced beta waves in the hippocampus measured with a dense electrode array (150 µm inter-electrode spacing)

(B) Sample of spontaneous responses in the presence of 50 µm carbachol

(C) Fast Fourier transformations display the frequency (x-axis) and amplitude (y-axis) of rhythmic activity

(D) Current source density analyses of carbachol-induced activity. The pseudo-colored panels show the computed current source density in the region of the electrode array at several time points during a carbachol-induced oscillation. The outlines of the pyramidal and granule cell fields and their apical dendrites are overlayed.

At time 0 ms, a sink appears in the apical dendrites of the border between fields CA3 and CA1 with a corresponding source in the basal dendrites. The fields merge and intensify and then dissipate after ~12 ms. At ~20 ms, a source appears in the apical dendrites with a corresponding sink in the basal dendrites. These expand and intensify before dissipating at ~40 ms, after which an apical sink reappears to reinitiate the cycle.

K. Shimono et al. Origin and distribution of cholinergically induced beta rhythms in hippocampal slices. J. Neurosci. 15, 8462-8473 (2000)

Example 2: The study of circadian and other biological rhythms as the cultures grown in the probe can be tested repeatedly day and night.

(A) A phase-contrast photomicrograph of a cultured SCN slice on the MED probe after 14 d in culture. (20 µm square micro-electrodes with 100 µm inter-electrode spacing) Scale bar, 150 µm

(B) Representative circadian firing rhythms of SCN neurons from Clock mutant and wild-type mice in slice cultures.

The firing rhythm was expressed in a histogram of the mean firing rate in 15 min. and double-plotted. The numbers in the right margin of the first lane in each panel were the scales of firing rate. The circadian periods of these firing rhythms were 28.1 h (left) and 28.0 h (right) for Clock/Clock, 25.3 h and 24.5 h for Clock/+, and 23.3 h and 23.8 h for +/+ neurons, respectively.

Nakamura, W. et al. Clock Mutation lengthens the circadian period without damping rhythms in individual SCN neurons. Nature Neuroscience, 5, 399-400 (2002)

Example 3: Endogenous Hippocampal Beta Rhythm

Acute slices from adult rat hippocampus were prepared on the MED probe. Infusion of carbachol (50mM), an acetylcholinergic agonist, triggered spontaneous beta waves in pyramidal regions in 41/55 slices.

Current source density analysis indicated that during each cycle (panel numbers refer to time during the 42 ms cycle) a sink appeared in field CA3 that extended to CA1 (0-9ms) where it subsided (15ms). This was followed by corresponding sources mirroring the sinks of the previous half cycle, in the same regions (21-36ms).

Based on data provided by G. Lynch (1999), UC Irvine