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ref: Bartels-2008.09 tags: neurotrophic kennedy speech FM transmitter wireless Georga recording electrophysiology electrode date: 01-19-2017 02:18 gmt revision:6 [5] [4] [3] [2] [1] [0] [head]

PMID-18672003[0] Neurotrophic electrode: method of assembly and implantation into human motor speech cortex.

  • Glass electrode with 3-4 2mil Teflon insulated Au wires within it to record spiking.
  • Induce neurites (e.g. dendrites, axons, blood vessels, oligodendrocytes) to grow up into it using autologous sciatic nerve, and stay for the lifetime of the patient (Kennedy 1989) [1].
    • Histology has revealed axons, but not neurons, within the tissue inside the tip. (Kennedy 1989, 1992a.)
    • No glia in rat and monkey tests; PMID-1421115
    • Inserted 5-6mm into the cortex at an angle of 45 deg. far!?
  • Bipolar amplification on pairs of the Au wires.
  • patients damaged their electrodes due to spasms; same for monkeys, presumably. Seems the electronice and gold wires are also highly fragile. I'm quite familiar with this.
  • Includes a sine wave source for calibration. good idea!
  • Inductively powered @ 1Mhz.
  • FM modulation at 39.2Mz and 43.9Mhz. COTS?
    • The implantable electronics are bulky as can be seen in Figs. 14 and ‚Äčand 19. (what a mess?!)
  • 3 patients, 4 years in 2 patients that dies from unrelated causes, over 3 years in a third.
  • describe construction of electrode -- not complicated.

____References____

[0] Bartels J, Andreasen D, Ehirim P, Mao H, Seibert S, Wright EJ, Kennedy P, Neurotrophic electrode: method of assembly and implantation into human motor speech cortex.J Neurosci Methods 174:2, 168-76 (2008 Sep 30)
[1] Kennedy PR, The cone electrode: a long-term electrode that records from neurites grown onto its recording surface.J Neurosci Methods 29:3, 181-93 (1989 Sep)

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ref: Guenther-2009.12 tags: Guenther Kennedy 2009 neurotrophic electrode speech synthesize formant BMI date: 12-17-2011 02:12 gmt revision:2 [1] [0] [head]

PMID-20011034[0] A Wireless Brain-Machine Interface for Real-Time Speech Synthesis

  • Neurites grow into the glass electrode over the course of 3-4 months; the signals and neurons are henceforth stable, at least for the period prior publication (>4 years).
  • Used an FM modulator to send out the broadband neural signal; powered the implanted electronics inductively.
  • Sorted 56 spike clusters (!!)
    • quote: "We chose to err on the side of overestimating the number of clusters in our BMI since our Kalman filter decoding technique is somewhat robust to noisy inputs, whereas a stricter criterion for cluster definition might leave out information-carrying spike clusters."
    • 27 units on one wire and 29 on the other.
  • Quote: "neurons in the implanted region of left ventral premotor cortex represent intended speech sounds in terms of formant frequency trajectories, and projections from these neurons to primary motor cortex transform the intended formant trajectories into motor commands to the speech articulators."
    • Thus speech can be represented as a trajectory through formant space.
    • plus there are many simple low-load formant-based sw synthesizers
  • Used supervised methods (ridge regression), where the user was asked to imagine making vowel sounds mimicking what he heard.
    • only used the first 2 vowel formants; hence 2D task.
    • Supervised from 8 ~1-minute recording sessions.
  • 25 real-time feedback sessions over 5 months -- not much training time, why?
  • Video looks alright.

____References____

[0] Guenther FH, Brumberg JS, Wright EJ, Nieto-Castanon A, Tourville JA, Panko M, Law R, Siebert SA, Bartels JL, Andreasen DS, Ehirim P, Mao H, Kennedy PR, A wireless brain-machine interface for real-time speech synthesis.PLoS One 4:12, e8218 (2009 Dec 9)

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ref: bookmark-0 tags: Unscented sigma_pint kalman filter speech processing machine_learning SDRE control UKF date: 0-0-2007 0:0 revision:0 [head]