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, 17 (4), 339-45

Active Microelectronic Neurosensor Arrays for Implantable Brain Communication Interfaces

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Active Microelectronic Neurosensor Arrays for Implantable Brain Communication Interfaces

Y-K Song et al. IEEE Trans Neural Syst Rehabil Eng.

Abstract

We have built a wireless implantable microelectronic device for transmitting cortical signals transcutaneously. The device is aimed at interfacing a cortical microelectrode array to an external computer for neural control applications. Our implantable microsystem enables 16-channel broadband neural recording in a nonhuman primate brain by converting these signals to a digital stream of infrared light pulses for transmission through the skin. The implantable unit employs a flexible polymer substrate onto which we have integrated ultra-low power amplification with analog multiplexing, an analog-to-digital converter, a low power digital controller chip, and infrared telemetry. The scalable 16-channel microsystem can employ any of several modalities of power supply, including radio frequency by induction, or infrared light via photovoltaic conversion. As of the time of this report, the implant has been tested as a subchronic unit in nonhuman primates ( approximately 1 month), yielding robust spike and broadband neural data on all available channels.

Figures

Fig. 1
Fig. 1
Schematics of the ‘dual panel’ brain implantable microsystem featuring an active brain sensor (microelectrode array integrated to amplifier IC) in the cortical unit, and hybrid A/D, control, and RF-IR(Infrared) telemetry in the cranial unit.
Fig. 2
Fig. 2
(a) Photographic images showing an implantable 16-channel microsystem with a dual-panel liquid crystal polymer substrate. A spiral pattern of RF power receiving coil is clearly visible in the backside image; (b) a block diagram of the dual-panel microsystem showing neural signal and power/clock flows among various micro- and optoelectronic components.
Fig. 3
Fig. 3
(a) RF input power/clock transmission with coil separation of ~3mm (Top Trace); Pulse-coded optical output datastream representing part of a neural event (Bottom Trace), and (b) Comparison of system performance using pseudospike recording test in saline bath. 100-500 μV signals are injected into the saline bath and recorded by hybrid RF-IR power/telemetry wireless system (right) and a system with electrically wired telemetry and power links as a reference (left).
Fig. 4
Fig. 4
(a) A block diagram of the ‘Brown NeuroCard’, which is a compact neural recording system on PCB substrate with a Neuroport™ adapter connecting to the input terminals (b) A photographic image of the Brown NeuroCard showing various micro- and optoelectronic components on a small PCB substrate.
Fig. 5
Fig. 5
(a) A typical multichannel (15 channels) neural recording acquired with the Brown Neurocard from a behaving Rhesus monkey with a passive microelectrode array implanted in the primary motor cortex (M1). Each subplot represents a 500μV range and 3.5msec interval and contains superimposed action potentials from continuous recording for about 5 seconds. (b) Successive recordings were performed in a single session (within 2 hours) with Cerebus™ recording system (left panel) and Brown Neurocard (right panel), yielding very similar results in both spike shapes and spiking rates. All the waveforms shown here are band-pass-filtered at 0.3-7.5 kHz. Channel 4 did not exhibit clear spike activity.
Fig. 6
Fig. 6
In-vivo recording of neural activity by the 4×4 element integrated active neural probe from motor cortex of an anesthetized rat, showing 23 consecutive spikes superimposed in a 5 ms window [18].
Fig. 7
Fig. 7
Cortical action potentials recorded from a fully implanted neural microsystem in a rhesus monkey. Pulse code modulated IR optical signal of neural data was transmitted to an external photoreceiver through skin (inset: an IR sensitive “night vision” photograph showing a bright spot on the monkey’s head where the IR laser is located under the skin). 48 spike waveforms are detected for 15 seconds, and superimposed in a single plot after off-line filtering. The data was taken 7 days after implant surgery.

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