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The Effects of Inflammation on Chronic Recording Reliability

  • George McConnell

This project investigates inflammation surrounding microelectrodes as a potential mechanism for chronic recording failure. Chronic recording from the brain suffers from an inability to reliably record neural signals after several months. In many cases, the ability to record from a site deteriorates entirely (see Figure 1).

George studies the tissue reaction to microelectrodes implanted in rat cortex and the effect on recording reliability. He has investigated the adhesive properties of the astroglial scar, which forms surrounding chronic microelectrode arrays [1]. As part of this study, state-of-the-art immunohistochemical markers were used to gain insight into a potential mechanism for microelectrode-scar adhesion.

Currently, George is working on developing impedance spectroscopy as a non-invasive technique to quantify tissue reaction to microelectrodes [2]. This technique shows promise for becoming a valuable tool for evaluating strategies to reduce tissue reaction, such as anti-inflammatory coatings [3,4], and thereby improve the longevity of chronic recordings.

Coatings, Figure 1A Coatings, Figure 1B

Figure 1. Separable units observed at 6 days were no longer discernable after 7 weeks. Sorted units from identical recording site after 6 days (A) and 47 days (B) post-implantation. (A) Two units with signal-to-noise ratio (SNR)=7.98 and 4.17. (B) Single unit with SNR=0.98, indicating an inability to separate from noise.

    References
  1. McConnell G, Schneider TM, Owens DJ, and Bellamkonda RV. 2007. Extraction Force and Cortical Tissue Reaction of Silicon Microelectrode Arrays Implanted in the Rat Brain. IEEE Transactions on Biomedical Engineering 54(6 Pt 1):1097-107.
  2. McConnell GC, Butera RJ, Bellamkonda RV. 2008. Py value is significantly correlated with GFAP expression and cellular density surrounding chronic intra-cortical microelectrodes. Neural Interfaces Workshop. Cleveland, OH.
  3. He W, McConnell GC, Schneider TM, Bellamkonda RV. 2007. A novel anti-inflammatory surface for neural electrodes. Advanced Materials. 19: 3529-3533.
  4. He W*, McConnell GC*, Bellamkonda RV. 2006. Nanoscale laminin coating mitigates chronic response of cortex to silicon microelectrode arrays. Journal of Neural Engineering, 3(4): 316-24.
    * both authors contributed equally