Limits...
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 relative amplitudes of single unit spikes with high waveform correlation (>0.96) during two consecutive weeks. (A) Relative difference in amplitude shown as median and percentile values. The amplitude of units showed a tendency to increase over time, but this difference was not significant (p > 0.05). (B,C) Representative recordings (100 ms long) during week 2 and 3 in two different animals. Recordings are made from the same channel and show highly correlated units (waveform correlation > 0.96). Mean waveform ± standard deviation is shown to the right of each recording. In some cases, the amplitude of the units increased from week 2 to 3 (B), whereas in some other cases, the amplitude decreased (C).
© Copyright Policy
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4585103&req=5

Figure 7: Characterization of relative amplitudes of single unit spikes with high waveform correlation (>0.96) during two consecutive weeks. (A) Relative difference in amplitude shown as median and percentile values. The amplitude of units showed a tendency to increase over time, but this difference was not significant (p > 0.05). (B,C) Representative recordings (100 ms long) during week 2 and 3 in two different animals. Recordings are made from the same channel and show highly correlated units (waveform correlation > 0.96). Mean waveform ± standard deviation is shown to the right of each recording. In some cases, the amplitude of the units increased from week 2 to 3 (B), whereas in some other cases, the amplitude decreased (C).

Mentions: Single-unit recordings obtained during different recording sessions with a waveform correlation higher than 0.96 [see Section Materials and Methods (subsection Recording Performance Over Time)] were obtained during the larger part of the experimental period in all animals. The relative difference in amplitude for such correlated waveforms was close to 1 (median = 1.22, IQR = 0.72) during the whole experiment (Figure 7A). No significant (p > 0.05) difference in relative amplitude difference was observed between week 1 and 2, and week 2 and 3. However, the relative difference in amplitude tended to be smaller (closer to 1) between week 2 and 3. Despite this relatively low overall difference in amplitude, we did observe some cases where the amplitude (and thus SNR) differed significantly (up to a factor of around 3) while the waveform remained relatively unchanged (correlation > 0.96) (Figures 7B,C).


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 relative amplitudes of single unit spikes with high waveform correlation (>0.96) during two consecutive weeks. (A) Relative difference in amplitude shown as median and percentile values. The amplitude of units showed a tendency to increase over time, but this difference was not significant (p > 0.05). (B,C) Representative recordings (100 ms long) during week 2 and 3 in two different animals. Recordings are made from the same channel and show highly correlated units (waveform correlation > 0.96). Mean waveform ± standard deviation is shown to the right of each recording. In some cases, the amplitude of the units increased from week 2 to 3 (B), whereas in some other cases, the amplitude decreased (C).
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4585103&req=5

Figure 7: Characterization of relative amplitudes of single unit spikes with high waveform correlation (>0.96) during two consecutive weeks. (A) Relative difference in amplitude shown as median and percentile values. The amplitude of units showed a tendency to increase over time, but this difference was not significant (p > 0.05). (B,C) Representative recordings (100 ms long) during week 2 and 3 in two different animals. Recordings are made from the same channel and show highly correlated units (waveform correlation > 0.96). Mean waveform ± standard deviation is shown to the right of each recording. In some cases, the amplitude of the units increased from week 2 to 3 (B), whereas in some other cases, the amplitude decreased (C).
Mentions: Single-unit recordings obtained during different recording sessions with a waveform correlation higher than 0.96 [see Section Materials and Methods (subsection Recording Performance Over Time)] were obtained during the larger part of the experimental period in all animals. The relative difference in amplitude for such correlated waveforms was close to 1 (median = 1.22, IQR = 0.72) during the whole experiment (Figure 7A). No significant (p > 0.05) difference in relative amplitude difference was observed between week 1 and 2, and week 2 and 3. However, the relative difference in amplitude tended to be smaller (closer to 1) between week 2 and 3. Despite this relatively low overall difference in amplitude, we did observe some cases where the amplitude (and thus SNR) differed significantly (up to a factor of around 3) while the waveform remained relatively unchanged (correlation > 0.96) (Figures 7B,C).

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