Polymer Fiber Probes Enable Optical Control of Spinal Cord and Muscle Function In Vivo

Abstract

Restoration of motor and sensory functions in paralyzed patients requires the development of tools for simultaneous recording and stimulation of neural activity in the spinal cord. In addition to its complex neurophysiology, the spinal cord presents technical challenges stemming from its flexible fibrous structure and repeated elastic deformation during normal motion. To address these engineering constraints, we developed highly flexible fiber probes, consisting entirely of polymers, for combined optical stimulation and recording of neural activity. The fabricated fiber probes exhibit low-loss light transmission even under repeated extreme bending deformations.Using our fiber probes, we demonstrate simultaneous recording and optogenetic stimulation of neural activity in the spinal cord of transgenic mice expressing the light sensitive protein channelrhodopsin 2 (ChR2). Furthermore, optical stimulation of the spinal cord with the polymer fiber probes induces on-demand limb movements that correlate with electromyographical (EMG) activity.

Optogenetic entrainment of neural oscillations with hybrid fiber probes

“…Optical fibers with a PC core (refractive index n = 1.58) and COC cladding (n = 1.52) were capable of transmitting 473 nm light with a loss of 2.44 dB cm −1 , which is comparable to previously reported values for this materials combination (figure 1(C), [22]).…”

Optogenetic entrainment of neural oscillations with hybrid fiber probes

“…Optical fibers with a PC core (refractive index n = 1.58) and COC cladding (n = 1.52) were capable of transmitting 473 nm light with a loss of 2.44 dB cm −1 , which is comparable to previously reported values for this materials combination (figure 1(C), [22]).…”

Closed‐Loop Optogenetic Modulation of Neural Activities in Freely Moving Mice with Multimodal Fibers

“…The specific impedance (at 1 kHz) of the two multimodal fiber probes was calculated to be only 5.40 MΩ µm 2 and 10.62 MΩ µm 2 , respectively. They are one or two orders of magnitude smaller than that of the previous reported probes, [ 18,33,34 ] mainly due to the excellent electrical conductivity of Pt and W electrodes. Low impedance is beneficial to record weak electrical signals, but it is also easy to record noises.…”

Wirelessly powered, fully internal optogenetics for brain, spinal and peripheral circuits in mice

“…We and others have previously demonstrated that nerve cuffs and optical fibers can be used to control spinal cord and peripheral nerve circuits in mice and rats 20–22 . However, these tethered devices are typically bulky and restrict animal movement.…”

Optogenetic entrainment of neural oscillations with hybrid fiber probes

“…Optical fibers with a PC core (refractive index n = 1.58) and COC cladding (n = 1.52) were capable of transmitting 473 nm light with a loss of 2.44 dB cm −1 , which is comparable to previously reported values for this materials combination (figure 1(C), [22]).…”

Closed‐Loop Optogenetic Modulation of Neural Activities in Freely Moving Mice with Multimodal Fibers

“…The specific impedance (at 1 kHz) of the two multimodal fiber probes was calculated to be only 5.40 MΩ µm 2 and 10.62 MΩ µm 2 , respectively. They are one or two orders of magnitude smaller than that of the previous reported probes, [ 18,33,34 ] mainly due to the excellent electrical conductivity of Pt and W electrodes. Low impedance is beneficial to record weak electrical signals, but it is also easy to record noises.…”

Wirelessly powered, fully internal optogenetics for brain, spinal and peripheral circuits in mice

“…We and others have previously demonstrated that nerve cuffs and optical fibers can be used to control spinal cord and peripheral nerve circuits in mice and rats 20–22 . However, these tethered devices are typically bulky and restrict animal movement.…”

Optogenetic entrainment of neural oscillations with hybrid fiber probes

“…Optical fibers with a PC core (refractive index n = 1.58) and COC cladding (n = 1.52) were capable of transmitting 473 nm light with a loss of 2.44 dB cm −1 , which is comparable to previously reported values for this materials combination (figure 1(C), [22]).…”

Closed‐Loop Optogenetic Modulation of Neural Activities in Freely Moving Mice with Multimodal Fibers

“…The specific impedance (at 1 kHz) of the two multimodal fiber probes was calculated to be only 5.40 MΩ µm 2 and 10.62 MΩ µm 2 , respectively. They are one or two orders of magnitude smaller than that of the previous reported probes, [ 18,33,34 ] mainly due to the excellent electrical conductivity of Pt and W electrodes. Low impedance is beneficial to record weak electrical signals, but it is also easy to record noises.…”

Wirelessly powered, fully internal optogenetics for brain, spinal and peripheral circuits in mice

“…We and others have previously demonstrated that nerve cuffs and optical fibers can be used to control spinal cord and peripheral nerve circuits in mice and rats 20–22 . However, these tethered devices are typically bulky and restrict animal movement.…”