LMAv2 - The 2nd generation Linear Microelectrode Array

Two years ago, Microprobes for Life Science strove to design a next-generation LMA based on years of customer feedback on the original. In short, researchers needed a probe that was longer, sharper, more reliable, more resistant to bending after many insertions, and budget-friendlier than competing options. We recognized that the short length limitations of the original LMA as well as its blunter tip and too-flexible shank would need to be greatly improved. With all these in mind, our technicians created the LMAv2. This probe features a special tapered-tube design that allows for the functional tip section diameter to be under 200 microns while featuring up to 32 contacts tuned for unit recording. Above this tip section, the tube tapers up to a wider diameter allowing for a substantially longer and more rigid shaft section.
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  • The LMAv2 is competitively priced and significantly lower in cost compared to similar linear arrays available on the market.
  • The LMAv2 has been successfully used for Acute and Chronic applications.
  • Thinner functional tip section, even up to 32 channels.
  • A solid tungsten core 2x thicker than in the original LMA, greatly improving rigidity.
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  • The tungsten is custom etched to match the taper of the probe, creating a tip that is much sharper and smoother than the original.
  • A polyimide section that extends 65mm and beyond, much longer than the 15mm permitted in the original LMA.
  • All of the versatility of the original LMA including arbitrary contact placement anywhere along the shank (linear, multi-columnal, helical, clustered, directional ringed), both acute and chronic configurations, flexible cable and multi-shank options, and available MRI compatibility.
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The LMAv2 probe is now our linear electrode array of choice for acute neurophysiology in behaving macaque monkeys. We record from cortex and do not use a guide tube. The LMAv2 is stiff enough to penetrate through the silicone membrane that we implant in place of the native dura. Signal quality from the LMAv2 is excellent on most channels and consistent across sessions. We have used some LMAv2 arrays in over 30 penetrations and they are still delivering excellent results for both spikes and local field potentials. Our experience with the engineers at Microprobes has also been outstanding. With their expertise and discussions with our group, we now have an LMAv2 that is custom fit to our needs. Thank you Microprobes!
Figure 1. Waveforms from a single recording with an LMAv2. Recording is from motor cortex of a macaque monkey performing a reach-to-grasp task. Single and multi-units were isolated on 25 of the 32 channels. Many channels had 2-3 units. For each unit, ~20 consecutive waveforms are shown. Figure credit: Nick Chehade (PhD student in Gharbawie lab)
Figure 2. Voltage traces from 32 channels recorded with an LMAv2. Recording is from motor cortex of a macaque monkey performing a reach-to-grasp task. Red traces are from channels (5-29) that were confirmed in cortex. Channels 1-4 were above cortex and channels 30-32 were in white matter. This recording was from the 25th penetration done with this LMAv2.
Omar A. Gharbawie Ph.D.
Omar A. Gharbawie Ph.D.Department of Neurobiology; University of Pittsburgh
"Our lab chronically implants tetrodes into the auditory midbrain of rabbits to study hearing. We wanted to increase our yield by switching to linear microelectrode arrays with more channels, but it was difficult to find probes that were compatible with our microdrive setup and had the length needed to reach the midbrain. We chose the 16-channel LMAv2 because it was incredibly customizable and could work with our current microdrive. Using custom 3D-printed parts, we adapted our NeuraLynx 5-drive setup to use the LMAv2. With this setup, we can reach the 14mm depth of the auditory midbrain and sample at different depths. We have implanted a probe for about two months and have gotten high-quality single-unit midbrain recordings on 8/16 channels. We estimate the probe is about three quarters in the auditory midbrain and as we continue descending, we hope to see even more driven channels. The impedance values of the LMAv2 have stayed constant since implantation, and we are excited to continue collecting data with these probes. After we gather more pilot data, we hope to further increase yield by adding multiple probes.
Johanna, Fritzinger
Johanna, FritzingerNeuroscience graduate student; University of Rochester Medical Center
“My lab needed a multi-site recording electrode that could be chronically implanted at a shallow insertion angle into NHP frontal eye fields. We tried a flexible polyimide electrode, but a linear probe didn’t meet our needs. After talking with MicroProbes, Inc, we settled on the multi-shank LMAv2. The first couple of implants went well, and we were getting units on about 80-90% of the recording sites (16 channel in one implant, 32-channels in the other). That’s when it got interesting. At 3 months post implant, we were still getting units on 13 of the 16 channel implant! At 6 months, we still got units on half of the channels. Today we are approaching 12 months post implant and still getting units on 5 channels, and local field potentials on the original 13 channels that were viable at 3 months. Impedances have been stable since the first couple months. Obviously, this isn’t typical, but on the other implant, we lost implant integrity before we lost recordings on the LMAv2s! This fall I’m looking at up doing more implants in hippocampus and prefrontal cortex, and they will all be LMAv2s.
Robert E. Hampson, Ph.D.
Robert E. Hampson, Ph.D.Research Associate in the Winrich Freiwald lab at Rockefeller University

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