Alpha MED64 MEA System

Simultaneous recording of extracellular signals across 64 channels without pulling glass electrodes

Signals (evoked potentials or spontaneous activity) are acquired with 64 planar microelectrodes patterned on the MED probe.
Any of the 64 electrodes can be used for stimulation (up to two simultaneously). Stimulus channels and waveforms are selectable by software.

Reveal important extracellular signals that can be hidden by other systems!

The MED64 features with the industry’s lowest-impedance planar microelectrodes (10 kohm at 1 kHz), that afford several unique benefits…

The most sensitive (The best signal-to-noise ratio)

Electrode impedance is a major factor in determining an electrophysiological acquisition system’s baseline noise level. Lower electrode impedance results in lower baseline noise level. When using MEAs, having a low baseline noise is the only method to achieve a good signal-to-noise ratio because electrodes do not penetrate into biological samples.

Thanks to the industry’s lowest-impedance electrodes, the MED64 can provide the lowest baseline noise level which can reveal important signals that may be hidden by other systems.

Baseline noise and spike extractions

Recording inside of a humidified incubator

A general rule for electrophysiology system is “The head amplifier needs to be placed close to electrodes”. However, MED64’s low-impedance electrodes do not even require this configuration. The MED Connector (holding the MEA) is connected to the amplifier via a 2 meter long cable, that does not generate signal attenuation.

Recording from cultured neurons in an incubator

Excellent capabilities for stimulation

Stimulation using planar microelectrodes is more challenging than recording. One of the reasons is stimulated electrodes need some time to discharge. This phenomenon appears as “stimulus artifacts” that interfere with signals coming right after the stimulation.

The MED64’s low-impedance electrodes discharge instantly, so the stimulus artifacts return to 0 within 0.5 msec. Evoked signals can be clearly measured immediately after stimulation. MED64’s excellent stimulation capabilities are validated by hundreds of publications.

Recording of evoked signal that comes right after stimulus artifact (left). Example for dragged stimulus artifacts (right).

A rate limiter for stimulating with MEAs is that voltage charged to planar electrodes must not go beyond 1V to avoid electrolysis. This could hamper the amplitude of the current that can be delivered through an MEA.

The MED64’s planar microelectrode has much higher capacitance (22,000 pF for 50 μm electrode) relative to other commercially available MEA, enabling large current-driven stimulation (up to 200 μA) to all electrodes of the MED64.

Differences in behavior in response to stimulation for electrodes of different material composition

What is the reason for the low-impedance?

Making planar microelectrodes for MEA is difficult. MEA electrodes need to have large surface area to achieve low-impedance (Electrode impedance is inversely proposed to its surface area).

This dilemma can be solved by making electrode surface rough on the nano level. The planar microelectrode of the MED Probe is coated with platinum black using a unique technology that Panasonic/Alpha MED established. This manufacturing method dramatically increases the electrode surface area 100-200x larger and its impedance decreases accordingly.