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An array of highly flexible electrodes with a tailored configuration locked by gelatin during implantation-initial evaluation in cortex cerebri of awake rats.

Agorelius J, Tsanakalis F, Friberg A, Thorbergsson PT, Pettersson LM, Schouenborg J - Front Neurosci (2015)

Bottom Line: The structure of the electrode array was well preserved 3 weeks after implantation.A new implantable multichannel neural interface, comprising electrodes individually flexible in 3D that retain its architecture and functionality after implantation has been developed.Since the new neural interface design is adaptable, it offers a versatile tool to explore the function of various brain structures.

View Article: PubMed Central - PubMed

Affiliation: Department of Experimental Medical Science, Neuronano Research Centre, Lund University Lund, Sweden ; The Nanometer Structure Consortium, Lund University Lund, Sweden.

ABSTRACT

Background: A major challenge in the field of neural interfaces is to overcome the problem of poor stability of neuronal recordings, which impedes long-term studies of individual neurons in the brain. Conceivably, unstable recordings reflect relative movements between electrode and tissue. To address this challenge, we have developed a new ultra-flexible electrode array and evaluated its performance in awake non-restrained animals.

Methods: An array of eight separated gold leads (4 × 10 μm), individually flexible in 3D, were cut from a gold sheet using laser milling and insulated with Parylene C. To provide structural support during implantation into rat cortex, the electrode array was embedded in a hard gelatin based material, which dissolves after implantation. Recordings were made during 3 weeks. At termination, the animals were perfused with fixative and frozen to prevent dislocation of the implanted electrodes. A thick slice of brain tissue, with the electrode array still in situ, was made transparent using methyl salicylate to evaluate the conformation of the implanted electrode array.

Results: Median noise levels and signal/noise remained relatively stable during the 3 week observation period; 4.3-5.9 μV and 2.8-4.2, respectively. The spike amplitudes were often quite stable within recording sessions and for 15% of recordings where single-units were identified, the highest-SNR unit had an amplitude higher than 150 μV. In addition, high correlations (>0.96) between unit waveforms recorded at different time points were obtained for 58% of the electrode sites. The structure of the electrode array was well preserved 3 weeks after implantation.

Conclusions: A new implantable multichannel neural interface, comprising electrodes individually flexible in 3D that retain its architecture and functionality after implantation has been developed. Since the new neural interface design is adaptable, it offers a versatile tool to explore the function of various brain structures.

No MeSH data available.


Related in: MedlinePlus

Characterization of electrode performance over time. (A) Noise level estimated by Equation (1) (distributions shown as median and percentiles values) including all electrode channels. The noise increased significantly (***p < 0.001) between weeks 1 and 2, but remained stable between weeks 2 and 3 (p > 0.05). (B) Signal to noise ratio (SNR) of single-units (distribution including all identified units shown as median and percentile values) remained stable (p > 0.05) between week 1 and 2, but increased significantly between week 2 and 3 (**p < 0.01). This reflects the fact that high amplitude units were added during week 3. The increase in SNR and yield suggest that the overall recording conditions improved during the course of the experiment. (C) Bar diagram depicting yield in percentage (number of channels with units divided by number of channels is shown on top of each bar). It can be seen that yield increased for both good (SNR ≥ 4) and fair (SNR ≥ 2) units (C), although the increase was not strictly monotonic for fair units (peaked during week 2).
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Figure 6: Characterization of electrode performance over time. (A) Noise level estimated by Equation (1) (distributions shown as median and percentiles values) including all electrode channels. The noise increased significantly (***p < 0.001) between weeks 1 and 2, but remained stable between weeks 2 and 3 (p > 0.05). (B) Signal to noise ratio (SNR) of single-units (distribution including all identified units shown as median and percentile values) remained stable (p > 0.05) between week 1 and 2, but increased significantly between week 2 and 3 (**p < 0.01). This reflects the fact that high amplitude units were added during week 3. The increase in SNR and yield suggest that the overall recording conditions improved during the course of the experiment. (C) Bar diagram depicting yield in percentage (number of channels with units divided by number of channels is shown on top of each bar). It can be seen that yield increased for both good (SNR ≥ 4) and fair (SNR ≥ 2) units (C), although the increase was not strictly monotonic for fair units (peaked during week 2).

Mentions: The signal quality was good throughout the experiment with an overall median noise level of 5.42 μV (IQR1 = 2.16 μV) and overall median single-unit SNR of 3.30 (IQR = 2.30), respectively. As can be seen in Figure 6A, the noise level increased significantly (Mann-Whitney test, p < 0.001) between weeks 1 and 2, or from 4.27 to 5.95 μV (median) but remained stable (p > 0.05) between weeks 2 and 3. The SNR remained stable (p > 0.05) between weeks 1 and 2, but increased significantly (p < 0.01) between weeks 2 and 3, from 2.78 to 4.21 (median) (Figure 6B). In some cases, units with very high SNR (SNR > 6) were identified, indicating that the corresponding electrode sites in these cases were located very close to active neurons. In many cases, several single units with lower SNR were identified on the same channel, indicating that signals from more distant or electrically isolated neurons were also recorded.


An array of highly flexible electrodes with a tailored configuration locked by gelatin during implantation-initial evaluation in cortex cerebri of awake rats.

Agorelius J, Tsanakalis F, Friberg A, Thorbergsson PT, Pettersson LM, Schouenborg J - Front Neurosci (2015)

Characterization of electrode performance over time. (A) Noise level estimated by Equation (1) (distributions shown as median and percentiles values) including all electrode channels. The noise increased significantly (***p < 0.001) between weeks 1 and 2, but remained stable between weeks 2 and 3 (p > 0.05). (B) Signal to noise ratio (SNR) of single-units (distribution including all identified units shown as median and percentile values) remained stable (p > 0.05) between week 1 and 2, but increased significantly between week 2 and 3 (**p < 0.01). This reflects the fact that high amplitude units were added during week 3. The increase in SNR and yield suggest that the overall recording conditions improved during the course of the experiment. (C) Bar diagram depicting yield in percentage (number of channels with units divided by number of channels is shown on top of each bar). It can be seen that yield increased for both good (SNR ≥ 4) and fair (SNR ≥ 2) units (C), although the increase was not strictly monotonic for fair units (peaked during week 2).
© Copyright Policy
Related In: Results  -  Collection

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Figure 6: Characterization of electrode performance over time. (A) Noise level estimated by Equation (1) (distributions shown as median and percentiles values) including all electrode channels. The noise increased significantly (***p < 0.001) between weeks 1 and 2, but remained stable between weeks 2 and 3 (p > 0.05). (B) Signal to noise ratio (SNR) of single-units (distribution including all identified units shown as median and percentile values) remained stable (p > 0.05) between week 1 and 2, but increased significantly between week 2 and 3 (**p < 0.01). This reflects the fact that high amplitude units were added during week 3. The increase in SNR and yield suggest that the overall recording conditions improved during the course of the experiment. (C) Bar diagram depicting yield in percentage (number of channels with units divided by number of channels is shown on top of each bar). It can be seen that yield increased for both good (SNR ≥ 4) and fair (SNR ≥ 2) units (C), although the increase was not strictly monotonic for fair units (peaked during week 2).
Mentions: The signal quality was good throughout the experiment with an overall median noise level of 5.42 μV (IQR1 = 2.16 μV) and overall median single-unit SNR of 3.30 (IQR = 2.30), respectively. As can be seen in Figure 6A, the noise level increased significantly (Mann-Whitney test, p < 0.001) between weeks 1 and 2, or from 4.27 to 5.95 μV (median) but remained stable (p > 0.05) between weeks 2 and 3. The SNR remained stable (p > 0.05) between weeks 1 and 2, but increased significantly (p < 0.01) between weeks 2 and 3, from 2.78 to 4.21 (median) (Figure 6B). In some cases, units with very high SNR (SNR > 6) were identified, indicating that the corresponding electrode sites in these cases were located very close to active neurons. In many cases, several single units with lower SNR were identified on the same channel, indicating that signals from more distant or electrically isolated neurons were also recorded.

Bottom Line: The structure of the electrode array was well preserved 3 weeks after implantation.A new implantable multichannel neural interface, comprising electrodes individually flexible in 3D that retain its architecture and functionality after implantation has been developed.Since the new neural interface design is adaptable, it offers a versatile tool to explore the function of various brain structures.

View Article: PubMed Central - PubMed

Affiliation: Department of Experimental Medical Science, Neuronano Research Centre, Lund University Lund, Sweden ; The Nanometer Structure Consortium, Lund University Lund, Sweden.

ABSTRACT

Background: A major challenge in the field of neural interfaces is to overcome the problem of poor stability of neuronal recordings, which impedes long-term studies of individual neurons in the brain. Conceivably, unstable recordings reflect relative movements between electrode and tissue. To address this challenge, we have developed a new ultra-flexible electrode array and evaluated its performance in awake non-restrained animals.

Methods: An array of eight separated gold leads (4 × 10 μm), individually flexible in 3D, were cut from a gold sheet using laser milling and insulated with Parylene C. To provide structural support during implantation into rat cortex, the electrode array was embedded in a hard gelatin based material, which dissolves after implantation. Recordings were made during 3 weeks. At termination, the animals were perfused with fixative and frozen to prevent dislocation of the implanted electrodes. A thick slice of brain tissue, with the electrode array still in situ, was made transparent using methyl salicylate to evaluate the conformation of the implanted electrode array.

Results: Median noise levels and signal/noise remained relatively stable during the 3 week observation period; 4.3-5.9 μV and 2.8-4.2, respectively. The spike amplitudes were often quite stable within recording sessions and for 15% of recordings where single-units were identified, the highest-SNR unit had an amplitude higher than 150 μV. In addition, high correlations (>0.96) between unit waveforms recorded at different time points were obtained for 58% of the electrode sites. The structure of the electrode array was well preserved 3 weeks after implantation.

Conclusions: A new implantable multichannel neural interface, comprising electrodes individually flexible in 3D that retain its architecture and functionality after implantation has been developed. Since the new neural interface design is adaptable, it offers a versatile tool to explore the function of various brain structures.

No MeSH data available.


Related in: MedlinePlus