Research ArticleNEUROSCIENCE

Elastocapillary self-assembled neurotassels for stable neural activity recordings

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Science Advances  27 Mar 2019:
Vol. 5, no. 3, eaav2842
DOI: 10.1126/sciadv.aav2842
  • Fig. 1 Elastocapillary self-assembly of Neurotassels.

    (A) An as-fabricated 16-channel Neurotassel. The black dashed box highlights the freestanding segment supported on an aluminum release layer. XT and XL are the transverse and longitudinal directions, respectively. Scale bar, 500 μm. (B) Zoom-in view of 12-μm-wide and 3-μm-high microelectrode filaments, as marked by the dashed red box in (A). Scale bar, 50 μm. Inset: Scanning electron microscopy (SEM) image of a microelectrode filament with a 10-μm-diameter recording site. Scale bar, 10 μm (inset). (C) Simulated von Mises stresses in a deformed Neurotassel. (D) Schematics of the elastocapillary self-assembly of a Neurotassel. (E) Time sequence photographs of the elastocapillary self-assembly of a Neurotassel. Scale bar, 1 mm. (Photo credit: Shouliang Guan and Jinfen Wang at NCNST). (F) A Neurotassel/PEG assembly. Scale bar, 500 μm. (G and H) Zoom-in views of the Neurotassel/PEG assembly as marked by the red and black dashed boxes, respectively, in (F). Scale bars, 100 μm. (I) Cross-sectional image at the mesh-filament transition section, indicated by the red arrows in (G). Scale bar, 50 μm. (J) Cross-sectional image of the fiber. Scale bar, 10 μm.

  • Fig. 2 Recordings by Neurotassels during DPA tasks.

    (A) Schematic of the olfactory DPA task. (B) Performance of mice trained with the DPA task. Insets: An implanted 16-channel Neurotassel (left) and a mouse with an implanted Neurotassel in the mPFC (right). Error bars represent SD around the mean (n = 6). Scale bar, 1 mm (inset). (Photo credit: Xiaowei Gu at ION). (C) Microphoto of a 200-μm-thick brain slice with an implanted Neurotassel. The mouse brain was sliced in sagittal direction and parallel to the implanted Neurotassel. Anatomical borders were identified according to the stereotaxic atlas of Paxinos and Watson (2001). Scale bar, 500 μm. (D) Extracellular AP traces (250 to 8000 Hz) recorded by a 16-channel Neurotassel implanted in the mPFC of M04. Scale bars, 200 μV (vertical), 100 ms (horizontal). (E) LFP traces (0.5 to 200 Hz) during a task trial. Scale bars, 300 μV (vertical), 1 s (horizontal). (F) Spike rasters of isolated neurons during a task trial. Scale bars, 50 μV (vertical), 1 s and 1 ms (horizontal; left and right, respectively).

  • Fig. 3 Recording stability during DPA tasks.

    (A) Heat map of normalized firing rates (FRs) for the recorded neurons by Neurotassels during training. Each row represents the baseline-normalized firing rate of one neuron. The dashed red lines represent the onsets and offsets of odor delivery. (B) Distribution of neurons according to the continuously recorded duration days by Neurotassels (left) and microwire tetrodes (right), respectively. One hundred twenty-one (121) neurons were recorded by six Neurotassels from six mice, and 730 neurons were recorded by 256 tetrodes from eight mice. Each tetrode was constructed by twisting four PI-insulated, Ni-Chrome wires with a 12.5-μm-diameter core. (C) Cumulative distribution of the percentage of neurons as a function of recording duration showing significant increases in recording of Neurotassels (red line) compared with that of tetrodes (black line) (**P < 0.01, Kolmogorov-Smirnov test). (D) The waveforms of an example neuron stably recorded during the training process. Scale bars, 50 μV (vertical), 0.5 ms (horizontal). (E) Heat map of the normalized firing rate for two example neurons. Each row represents the baseline-normalized firing rate of one training day. (F) Percentage of neurons with an increase or a decrease in firing through training during the delay (left) and response (right) periods, respectively. Twenty-six (26) neurons that were continuously recorded for longer than 5 days were considered here.

  • Fig. 4 Simultaneous optogenetic stimulation and electrical recordings.

    (A) Schematic of elastocapillary self-assembly of a Neurotassel on a sharpened optical fiber. (B) A 61-channel Neurotassel assembled on a sharpened optical fiber without (left) and with (right) light, respectively. Scale bars, 100 μm. (C) Black: Potential trace for a single trial with optogenetic transients at onset and offset of laser stimulation. Orange: Potential trace after subtraction of the median. Scale bars, 0.1 mV (vertical), 10 ms (horizontal). (D) Average waveforms of light-evoked (blue) and spontaneous (black) spikes. Scale bars, 50 μV (vertical), 0.5 ms (horizontal). (E) Raster plots of evoked spike firing of an example neuron by 10-Hz (left) and 20-Hz (right) 5-ms laser stimulation (marked by blue bars). (F) Distribution of spike jitter from laser as measured by the delay from stimulation onset to the first evoked spikes during the 10-Hz (left, total 200 pulses) and 20-Hz (right, total 400 pulses) stimulation. (G) Top: Heat map of firing rates of seven neurons in response to 1-s laser stimulation. Middle: Averaged firing rate of the neurons. Bottom: Heat map of field potentials at the recording sites of the neurons.

  • Fig. 5 Chronic stability of implanted Neurotassels.

    (A to C) Average spike amplitude, SNR, and firing rate of all sortable neurons recorded by Neurotassels from 3 to 6 weeks after implantation. Error bars represent SD around the mean. (D) Aligned and average spike waveforms recorded by a microelectrode of a 16-channel Neurotassel from 3 to 6 weeks after implantation. Scale bars, 100 μV (vertical), 1 ms (horizontal). (E) PCA of all waveforms in (D). (F) Time evolution of ISI histograms. Bin size, 20 ms. (G to L) Immunohistochemical staining and bright-field images of a horizontal brain slice after 5-week implantation of a Neurotassel and a silicon probe, respectively. The 100-μm-thick slice was labeled for astrocytes [glial fibrillary acidic protein (GFAP), green] and neurons (NeuN, red). Inset: A silicon probe with a cross-section of 100 × 30 μm2. Scale bars, 50 μm (G to L), 100 μm (L, inset).

  • Fig. 6 Scalability of Neurotassels.

    (A) An as-fabricated 128-channel Neurotassel. Scale bar, 1 mm. (B) Zoom-in view of the microelectrode filaments in the red dashed box in (A). Scale bar, 50 μm. Inset: Zoom-in view in the white dashed box. Scale bar, 10 μm (inset). (C) An as-fabricated 1024-channel Neurotassel. Scale bar, 1 mm. (D) Zoom-in view of the microelectrode filaments in the red dashed box in (C). Scale bar, 50 μm. Inset: Zoom-in view in the white dashed box. Scale bar, 10 μm (inset). (E) An SEM image (tilted at 45°) of Pt-coated microelectrode filaments of a released 1024-channel Neurotassel. Scale bar, 10 μm. Inset: Focused ion beam–polished cross-section along the red dashed line. Scale bar, 1 μm (inset). (F and G) Assembled 128- and 1024-channel Neurotassel/PEG composite fibers, respectively. Scale bars, 200 μm. (H and I) Cross-sectional images of the assembled 128- and 1024-channel Neurotassel/PEG composite fibers, respectively. Scale bars, 20 μm. (J) Averaged impedance and yield of 16-, 61-, 128-, 256-, 512-, and 1024-channel Neurotassels after Pt electrodeposition. Error bars represent SE (n = 20).

Supplementary Materials

  • Supplementary material for this article is available at http://advances.sciencemag.org/cgi/content/full/5/3/eaav2842/DC1

    Fig. S1. Schematics of Neurotassel fabrication steps.

    Fig. S2. 61–channel Neurotassels.

    Fig. S3. Flip chip–bonded 16- and 61-channel Neurotassels.

    Fig. S4. Simulated deformation and von Mises stresses in Neurotassels.

    Fig. S5. Elastocapillary assembly of Neurotassels with water and PEG.

    Fig. S6. Implantation of Neurotassel/PEG composite fiber in brain phantom.

    Fig. S7. Simultaneous recordings from aPC and pPC by two Neurotassels.

    Fig. S8. Time-dependent analysis of all recorded spiking activities during behavior training.

    Fig. S9. Time-dependent analysis of the spiking activities of two example neurons during behavioral training.

    Fig. S10. Simultaneous optical stimulation and electrical recordings with Neurotassel/optical fiber dual-functional probes.

    Fig. S11. Long-term recording stability of Neurotassels.

    Fig. S12. Chronic tissue response of Neurotassel and silicon probe after 5-week implantation.

    Fig. S13. Chronic tissue response of implanted probes.

    Fig. S14. Microglial activation in response to chronically implanted Neurotassel and silicon probe.

    Fig. S15. High-density Neurotassels.

    Fig. S16. Recordings with 1024-channel Neurotassels.

    Movie S1. Released Neurotassel.

    Movie S2. Elastocapillary assembly of Neurotassel.

    Movie S3. Depth implantation of Neurotassel in brain.

    Movie S4. Dissolution of PEG of Neurotassel/PEG fiber in the brain.

    Movie S5. Simultaneous optogenetic stimulation and recording with assembled Neurotassel/optical fiber probe.

    Movie S6. Mice with chronically implanted Neurotassels.

    Reference (60)

  • Supplementary Materials

    The PDF file includes:

    • Fig. S1. Schematics of Neurotassel fabrication steps.
    • Fig. S2. 61-channel Neurotassels.
    • Fig. S3. Flip chip–bonded 16- and 61-channel Neurotassels.
    • Fig. S4. Simulated deformation and von Mises stresses in Neurotassels.
    • Fig. S5. Elastocapillary assembly of Neurotassels with water and PEG.
    • Fig. S6. Implantation of Neurotassel/PEG composite fiber in brain phantom.
    • Fig. S7. Simultaneous recordings from aPC and pPC by two Neurotassels.
    • Fig. S8. Time-dependent analysis of all recorded spiking activities during behavior training.
    • Fig. S9. Time-dependent analysis of the spiking activities of two example neurons during behavioral training.
    • Fig. S10. Simultaneous optical stimulation and electrical recordings with Neurotassel/optical fiber dual-functional probes.
    • Fig. S11. Long-term recording stability of Neurotassels.
    • Fig. S12. Chronic tissue response of Neurotassel and silicon probe after 5-week implantation.
    • Fig. S13. Chronic tissue response of implanted probes.
    • Fig. S14. Microglial activation in response to chronically implanted Neurotassel and silicon probe.
    • Fig. S15. High-density Neurotassels.
    • Fig. S16. Recordings with 1024-channel Neurotassels.
    • Legends for movies S1 to S6
    • Reference (60)

    Download PDF

    Other Supplementary Material for this manuscript includes the following:

    • Movie S1 (.mov format). Released Neurotassel.
    • Movie S2 (.mov format). Elastocapillary assembly of Neurotassel.
    • Movie S3 (.mov format). Depth implantation of Neurotassel in brain.
    • Movie S4 (.mov format). Dissolution of PEG of Neurotassel/PEG fiber in the brain.
    • Movie S5 (.mov format). Simultaneous optogenetic stimulation and recording with assembled Neurotassel/optical fiber probe.
    • Movie S6 (.mov format). Mice with chronically implanted Neurotassels.

    Files in this Data Supplement:

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