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Radiant energy required for infrared neural stimulation.

Tan X, Rajguru S, Young H, Xia N, Stock SR, Xiao X, Richter CP - Sci Rep (2015)

Bottom Line: Maximum responses were observed when the radiation beam was directed towards the spiral ganglion neurons (SGNs), whereas little responses were seen when the beam was directed towards the basilar membrane.For cochlear INS it has been debated whether the radiation directly stimulates the SGNs or evokes a photoacoustic effect.The results support the view that a direct interaction between neurons and radiation dominates the response to INS.

View Article: PubMed Central - PubMed

Affiliation: Department of Otolaryngology, Northwestern University, 303 E. Chicago Ave, Searle 12-561, Chicago, IL 60611, USA.

ABSTRACT
Infrared neural stimulation (INS) has been proposed as an alternative method to electrical stimulation because of its spatial selective stimulation. Independent of the mechanism for INS, to translate the method into a device it is important to determine the energy for stimulation required at the target structure. Custom-designed, flat and angle polished fibers, were used to deliver the photons. By rotating the angle polished fibers, the orientation of the radiation beam in the cochlea could be changed. INS-evoked compound action potentials and single unit responses in the central nucleus of the inferior colliculus (ICC) were recorded. X-ray computed tomography was used to determine the orientation of the optical fiber. Maximum responses were observed when the radiation beam was directed towards the spiral ganglion neurons (SGNs), whereas little responses were seen when the beam was directed towards the basilar membrane. The radiant exposure required at the SGNs to evoke compound action potentials (CAPs) or ICC responses was on average 18.9 ± 12.2 or 10.3 ± 4.9 mJ/cm(2), respectively. For cochlear INS it has been debated whether the radiation directly stimulates the SGNs or evokes a photoacoustic effect. The results support the view that a direct interaction between neurons and radiation dominates the response to INS.

No MeSH data available.


Related in: MedlinePlus

Responses of single units from the ICC obtained during INS.(A) A representative example of single unit responses to a continuous 5 Hz INS pulse trains at orientations of 0, 90, 180, 270 and 360° is shown in the raster plots. Each dot represents an action potential. Note that the phase-locked responses at ~24 ms following stimulus presentation to 5 Hz INS pulse trains were only observed in the initial orientation (0°) and recurred at the same orientation (360°) after a full turn of rotation. (B) Vector strengths in response to INS at different energy levels and orientations. When the vector strength is higher than the Rayleigh criteria (open circles superimposed on each column), the response is considered significantly phase-locked (P < 0.001). The inset shows the uniformity of all the action potential waveforms recorded. The threshold stimulation energy of the single units was 12.4 μJ/pulse.
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f4: Responses of single units from the ICC obtained during INS.(A) A representative example of single unit responses to a continuous 5 Hz INS pulse trains at orientations of 0, 90, 180, 270 and 360° is shown in the raster plots. Each dot represents an action potential. Note that the phase-locked responses at ~24 ms following stimulus presentation to 5 Hz INS pulse trains were only observed in the initial orientation (0°) and recurred at the same orientation (360°) after a full turn of rotation. (B) Vector strengths in response to INS at different energy levels and orientations. When the vector strength is higher than the Rayleigh criteria (open circles superimposed on each column), the response is considered significantly phase-locked (P < 0.001). The inset shows the uniformity of all the action potential waveforms recorded. The threshold stimulation energy of the single units was 12.4 μJ/pulse.

Mentions: Since the CAP is the summation of the responses from many neurons along the cochlea it is not clear whether the response comes right from the target structure. For example, photoacoustic events caused by the infrared irradiation may activate large areas of the cochlea. To study local responses to INS along the cochlea, recordings in the ICC were conducted with multichannel electrodes, which were inserted in the ICC across frequency laminae. Multi-unit responses might be recorded at each electrode contact of the multichannel electrode array19. Therefore, an offline sorting procedure was performed for each recording to identify single units. Responses from well-isolated single units should have more precise orientation-dependence. An example is shown in Fig. 4A. The 5 panels in Fig. 4A show the responses of the single units to INS at orientations 0, 90, 180, 270 and 360°, respectively. Phase-locked responses to 5 Hz trains of laser pulses were only observed in the initial orientation (0°) and recurred at the same orientation (360°) after a full turn rotation of the angle-polished fiber. Phase-locked responses were determined by calculating the vector strength from single units in the ICC with well-isolated action potential waveforms such as the one shown in the inset of Fig. 4B. We used the Rayleigh test to determine the statistical significance of phase-locked firing (Fig. 4B). For this single unit, the threshold radiant energy required for stimulation in the ICC was 12.4 μJ/pulse.


Radiant energy required for infrared neural stimulation.

Tan X, Rajguru S, Young H, Xia N, Stock SR, Xiao X, Richter CP - Sci Rep (2015)

Responses of single units from the ICC obtained during INS.(A) A representative example of single unit responses to a continuous 5 Hz INS pulse trains at orientations of 0, 90, 180, 270 and 360° is shown in the raster plots. Each dot represents an action potential. Note that the phase-locked responses at ~24 ms following stimulus presentation to 5 Hz INS pulse trains were only observed in the initial orientation (0°) and recurred at the same orientation (360°) after a full turn of rotation. (B) Vector strengths in response to INS at different energy levels and orientations. When the vector strength is higher than the Rayleigh criteria (open circles superimposed on each column), the response is considered significantly phase-locked (P < 0.001). The inset shows the uniformity of all the action potential waveforms recorded. The threshold stimulation energy of the single units was 12.4 μJ/pulse.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4548241&req=5

f4: Responses of single units from the ICC obtained during INS.(A) A representative example of single unit responses to a continuous 5 Hz INS pulse trains at orientations of 0, 90, 180, 270 and 360° is shown in the raster plots. Each dot represents an action potential. Note that the phase-locked responses at ~24 ms following stimulus presentation to 5 Hz INS pulse trains were only observed in the initial orientation (0°) and recurred at the same orientation (360°) after a full turn of rotation. (B) Vector strengths in response to INS at different energy levels and orientations. When the vector strength is higher than the Rayleigh criteria (open circles superimposed on each column), the response is considered significantly phase-locked (P < 0.001). The inset shows the uniformity of all the action potential waveforms recorded. The threshold stimulation energy of the single units was 12.4 μJ/pulse.
Mentions: Since the CAP is the summation of the responses from many neurons along the cochlea it is not clear whether the response comes right from the target structure. For example, photoacoustic events caused by the infrared irradiation may activate large areas of the cochlea. To study local responses to INS along the cochlea, recordings in the ICC were conducted with multichannel electrodes, which were inserted in the ICC across frequency laminae. Multi-unit responses might be recorded at each electrode contact of the multichannel electrode array19. Therefore, an offline sorting procedure was performed for each recording to identify single units. Responses from well-isolated single units should have more precise orientation-dependence. An example is shown in Fig. 4A. The 5 panels in Fig. 4A show the responses of the single units to INS at orientations 0, 90, 180, 270 and 360°, respectively. Phase-locked responses to 5 Hz trains of laser pulses were only observed in the initial orientation (0°) and recurred at the same orientation (360°) after a full turn rotation of the angle-polished fiber. Phase-locked responses were determined by calculating the vector strength from single units in the ICC with well-isolated action potential waveforms such as the one shown in the inset of Fig. 4B. We used the Rayleigh test to determine the statistical significance of phase-locked firing (Fig. 4B). For this single unit, the threshold radiant energy required for stimulation in the ICC was 12.4 μJ/pulse.

Bottom Line: Maximum responses were observed when the radiation beam was directed towards the spiral ganglion neurons (SGNs), whereas little responses were seen when the beam was directed towards the basilar membrane.For cochlear INS it has been debated whether the radiation directly stimulates the SGNs or evokes a photoacoustic effect.The results support the view that a direct interaction between neurons and radiation dominates the response to INS.

View Article: PubMed Central - PubMed

Affiliation: Department of Otolaryngology, Northwestern University, 303 E. Chicago Ave, Searle 12-561, Chicago, IL 60611, USA.

ABSTRACT
Infrared neural stimulation (INS) has been proposed as an alternative method to electrical stimulation because of its spatial selective stimulation. Independent of the mechanism for INS, to translate the method into a device it is important to determine the energy for stimulation required at the target structure. Custom-designed, flat and angle polished fibers, were used to deliver the photons. By rotating the angle polished fibers, the orientation of the radiation beam in the cochlea could be changed. INS-evoked compound action potentials and single unit responses in the central nucleus of the inferior colliculus (ICC) were recorded. X-ray computed tomography was used to determine the orientation of the optical fiber. Maximum responses were observed when the radiation beam was directed towards the spiral ganglion neurons (SGNs), whereas little responses were seen when the beam was directed towards the basilar membrane. The radiant exposure required at the SGNs to evoke compound action potentials (CAPs) or ICC responses was on average 18.9 ± 12.2 or 10.3 ± 4.9 mJ/cm(2), respectively. For cochlear INS it has been debated whether the radiation directly stimulates the SGNs or evokes a photoacoustic effect. The results support the view that a direct interaction between neurons and radiation dominates the response to INS.

No MeSH data available.


Related in: MedlinePlus