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Peripheral optogenetic stimulation induces whisker movement and sensory perception in head-fixed mice

View Article: PubMed Central - PubMed

ABSTRACT

We discovered that optical stimulation of the mystacial pad in Emx1-Cre;Ai27D transgenic mice induces whisker movements due to activation of ChR2 expressed in muscles controlling retraction and protraction. Using high-speed videography in anesthetized mice, we characterize the amplitude of whisker protractions evoked by varying the intensity, duration, and frequency of optogenetic stimulation. Recordings from primary somatosensory cortex (S1) in anesthetized mice indicated that optogenetic whisker pad stimulation evokes robust yet longer latency responses than mechanical whisker stimulation. In head-fixed mice trained to report optogenetic whisker pad stimulation, psychometric curves showed similar dependence on stimulus duration as evoked whisker movements and S1 activity. Furthermore, optogenetic stimulation of S1 in expert mice was sufficient to substitute for peripheral stimulation. We conclude that whisker protractions evoked by optogenetic activation of whisker pad muscles results in cortical activity and sensory perception, consistent with the coding of evoked whisker movements by reafferent sensory input.

Doi:: http://dx.doi.org/10.7554/eLife.14140.001

No MeSH data available.


Related in: MedlinePlus

Characterization of whisker movements evoked by optogenetic whisker pad stimulation.(A) Top: Illustration of experiment setup (isoflurane anesthesia, 0.8–1.5%). Rostral whisker pad illumination (460 nm) was used to evoke whisker protractions (positive angle values). Bottom: Image of whiskers under infrared illumination as used for whisker tracking. Angle changes of individual whiskers were measured relative to the initial position (green lines). (B) Relationship between light intensity and evoked whisker protractions. Top: Example traces from one mouse (mean ± SD of single trial for n = 4 whiskers). Blue triangle indicates the onset of the light stimulation. Intensities: 1.3, 3.1, 4.1, 6.5, 8.4, 10.3 mW. Duration of stimuli, 50 ms. Bottom: amplitude of evoked angle change (left axis) and movement latency (right axis) vs. light intensity (bin size, 1 mW; mean ± SEM; n = 4 mice). (C) Relationship between light duration and evoked whisker protractions. Top: Example traces from one mouse (mean ± SD of 10 trials). Blue triangles indicates the onset of the light stimulation. Durations: 10–80 ms at 9.94 mW intensity. Bottom: amplitude of evoked angle change vs. light duration (mean ± SEM; n = 4 mice; note gap in axis between 60 and 250 ms and difference in x-axis scaling for 5–60 ms and 250–1200 ms). (D) Adaptation of evoked whisker protractions to optical pulse frequency. Top: two example traces from one mouse at 6 Hz and 22 Hz stimulation (9.94 mW). Blue triangle indicates the onset of the light stimulation. Bottom: Adaptation indexes (black: an/a1, ratio of last to first response amplitude; gray, a2/a1, ratio of second to first response amplitude) plotted versus stimulus frequency (mean ± SEM; n=3 mice).DOI:http://dx.doi.org/10.7554/eLife.14140.00610.7554/eLife.14140.007Figure 2—source data 1.Data for Figure 2B.DOI:http://dx.doi.org/10.7554/eLife.14140.007Data for Figure 2C.DOI:http://dx.doi.org/10.7554/eLife.14140.008Data for Figure 2D.DOI:http://dx.doi.org/10.7554/eLife.14140.009
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fig2: Characterization of whisker movements evoked by optogenetic whisker pad stimulation.(A) Top: Illustration of experiment setup (isoflurane anesthesia, 0.8–1.5%). Rostral whisker pad illumination (460 nm) was used to evoke whisker protractions (positive angle values). Bottom: Image of whiskers under infrared illumination as used for whisker tracking. Angle changes of individual whiskers were measured relative to the initial position (green lines). (B) Relationship between light intensity and evoked whisker protractions. Top: Example traces from one mouse (mean ± SD of single trial for n = 4 whiskers). Blue triangle indicates the onset of the light stimulation. Intensities: 1.3, 3.1, 4.1, 6.5, 8.4, 10.3 mW. Duration of stimuli, 50 ms. Bottom: amplitude of evoked angle change (left axis) and movement latency (right axis) vs. light intensity (bin size, 1 mW; mean ± SEM; n = 4 mice). (C) Relationship between light duration and evoked whisker protractions. Top: Example traces from one mouse (mean ± SD of 10 trials). Blue triangles indicates the onset of the light stimulation. Durations: 10–80 ms at 9.94 mW intensity. Bottom: amplitude of evoked angle change vs. light duration (mean ± SEM; n = 4 mice; note gap in axis between 60 and 250 ms and difference in x-axis scaling for 5–60 ms and 250–1200 ms). (D) Adaptation of evoked whisker protractions to optical pulse frequency. Top: two example traces from one mouse at 6 Hz and 22 Hz stimulation (9.94 mW). Blue triangle indicates the onset of the light stimulation. Bottom: Adaptation indexes (black: an/a1, ratio of last to first response amplitude; gray, a2/a1, ratio of second to first response amplitude) plotted versus stimulus frequency (mean ± SEM; n=3 mice).DOI:http://dx.doi.org/10.7554/eLife.14140.00610.7554/eLife.14140.007Figure 2—source data 1.Data for Figure 2B.DOI:http://dx.doi.org/10.7554/eLife.14140.007Data for Figure 2C.DOI:http://dx.doi.org/10.7554/eLife.14140.008Data for Figure 2D.DOI:http://dx.doi.org/10.7554/eLife.14140.009

Mentions: To quantitatively characterize the whisker movements evoked by peripheral optogenetic stimulation, we recorded high-speed video (500 frames/s) in anesthetized mice (isoflurane 0.8–1.5%) (Figure 2A) in response to 460 nm light stimulation of varying intensity, duration, and frequency, with illumination centered at the rostral protraction area. The amplitude of whisker protraction in response to a 50 ms light pulse of increasing intensity (range, 1.3–10.3 mW) increased approximately linearly to a maximum amplitude of 11.4 ± 1.2 degrees (mean ± SEM, n = 4 mice; maximum 14.8 degrees in one mouse; Figure 2B). In 2 of 4 mice, the angle change appeared to saturate at less than maximal power (8.37 and 9.94 mW, respectively). The average latency of optogenetically evoked whisker movement was 13.5 ± 0.3 ms (mean ± SEM, n = 4 mice; threshold defined as 10% of the maximum peak) and was not affected by stimulus duration. We used 9.94 mW to define the relationships between whisker protraction, duration, and frequency (below). We next measured the relationship between whisker protraction and optical stimuli of varying duration from 5 to 1200 ms (at 9.94 mW intensity). Whisker protraction angle increased with the duration of the optical stimulus, saturating with durations longer than approximately 60 ms (Figure 2C).10.7554/eLife.14140.006Figure 2.Characterization of whisker movements evoked by optogenetic whisker pad stimulation.


Peripheral optogenetic stimulation induces whisker movement and sensory perception in head-fixed mice
Characterization of whisker movements evoked by optogenetic whisker pad stimulation.(A) Top: Illustration of experiment setup (isoflurane anesthesia, 0.8–1.5%). Rostral whisker pad illumination (460 nm) was used to evoke whisker protractions (positive angle values). Bottom: Image of whiskers under infrared illumination as used for whisker tracking. Angle changes of individual whiskers were measured relative to the initial position (green lines). (B) Relationship between light intensity and evoked whisker protractions. Top: Example traces from one mouse (mean ± SD of single trial for n = 4 whiskers). Blue triangle indicates the onset of the light stimulation. Intensities: 1.3, 3.1, 4.1, 6.5, 8.4, 10.3 mW. Duration of stimuli, 50 ms. Bottom: amplitude of evoked angle change (left axis) and movement latency (right axis) vs. light intensity (bin size, 1 mW; mean ± SEM; n = 4 mice). (C) Relationship between light duration and evoked whisker protractions. Top: Example traces from one mouse (mean ± SD of 10 trials). Blue triangles indicates the onset of the light stimulation. Durations: 10–80 ms at 9.94 mW intensity. Bottom: amplitude of evoked angle change vs. light duration (mean ± SEM; n = 4 mice; note gap in axis between 60 and 250 ms and difference in x-axis scaling for 5–60 ms and 250–1200 ms). (D) Adaptation of evoked whisker protractions to optical pulse frequency. Top: two example traces from one mouse at 6 Hz and 22 Hz stimulation (9.94 mW). Blue triangle indicates the onset of the light stimulation. Bottom: Adaptation indexes (black: an/a1, ratio of last to first response amplitude; gray, a2/a1, ratio of second to first response amplitude) plotted versus stimulus frequency (mean ± SEM; n=3 mice).DOI:http://dx.doi.org/10.7554/eLife.14140.00610.7554/eLife.14140.007Figure 2—source data 1.Data for Figure 2B.DOI:http://dx.doi.org/10.7554/eLife.14140.007Data for Figure 2C.DOI:http://dx.doi.org/10.7554/eLife.14140.008Data for Figure 2D.DOI:http://dx.doi.org/10.7554/eLife.14140.009
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fig2: Characterization of whisker movements evoked by optogenetic whisker pad stimulation.(A) Top: Illustration of experiment setup (isoflurane anesthesia, 0.8–1.5%). Rostral whisker pad illumination (460 nm) was used to evoke whisker protractions (positive angle values). Bottom: Image of whiskers under infrared illumination as used for whisker tracking. Angle changes of individual whiskers were measured relative to the initial position (green lines). (B) Relationship between light intensity and evoked whisker protractions. Top: Example traces from one mouse (mean ± SD of single trial for n = 4 whiskers). Blue triangle indicates the onset of the light stimulation. Intensities: 1.3, 3.1, 4.1, 6.5, 8.4, 10.3 mW. Duration of stimuli, 50 ms. Bottom: amplitude of evoked angle change (left axis) and movement latency (right axis) vs. light intensity (bin size, 1 mW; mean ± SEM; n = 4 mice). (C) Relationship between light duration and evoked whisker protractions. Top: Example traces from one mouse (mean ± SD of 10 trials). Blue triangles indicates the onset of the light stimulation. Durations: 10–80 ms at 9.94 mW intensity. Bottom: amplitude of evoked angle change vs. light duration (mean ± SEM; n = 4 mice; note gap in axis between 60 and 250 ms and difference in x-axis scaling for 5–60 ms and 250–1200 ms). (D) Adaptation of evoked whisker protractions to optical pulse frequency. Top: two example traces from one mouse at 6 Hz and 22 Hz stimulation (9.94 mW). Blue triangle indicates the onset of the light stimulation. Bottom: Adaptation indexes (black: an/a1, ratio of last to first response amplitude; gray, a2/a1, ratio of second to first response amplitude) plotted versus stimulus frequency (mean ± SEM; n=3 mice).DOI:http://dx.doi.org/10.7554/eLife.14140.00610.7554/eLife.14140.007Figure 2—source data 1.Data for Figure 2B.DOI:http://dx.doi.org/10.7554/eLife.14140.007Data for Figure 2C.DOI:http://dx.doi.org/10.7554/eLife.14140.008Data for Figure 2D.DOI:http://dx.doi.org/10.7554/eLife.14140.009
Mentions: To quantitatively characterize the whisker movements evoked by peripheral optogenetic stimulation, we recorded high-speed video (500 frames/s) in anesthetized mice (isoflurane 0.8–1.5%) (Figure 2A) in response to 460 nm light stimulation of varying intensity, duration, and frequency, with illumination centered at the rostral protraction area. The amplitude of whisker protraction in response to a 50 ms light pulse of increasing intensity (range, 1.3–10.3 mW) increased approximately linearly to a maximum amplitude of 11.4 ± 1.2 degrees (mean ± SEM, n = 4 mice; maximum 14.8 degrees in one mouse; Figure 2B). In 2 of 4 mice, the angle change appeared to saturate at less than maximal power (8.37 and 9.94 mW, respectively). The average latency of optogenetically evoked whisker movement was 13.5 ± 0.3 ms (mean ± SEM, n = 4 mice; threshold defined as 10% of the maximum peak) and was not affected by stimulus duration. We used 9.94 mW to define the relationships between whisker protraction, duration, and frequency (below). We next measured the relationship between whisker protraction and optical stimuli of varying duration from 5 to 1200 ms (at 9.94 mW intensity). Whisker protraction angle increased with the duration of the optical stimulus, saturating with durations longer than approximately 60 ms (Figure 2C).10.7554/eLife.14140.006Figure 2.Characterization of whisker movements evoked by optogenetic whisker pad stimulation.

View Article: PubMed Central - PubMed

ABSTRACT

We discovered that optical stimulation of the mystacial pad in Emx1-Cre;Ai27D transgenic mice induces whisker movements due to activation of ChR2 expressed in muscles controlling retraction and protraction. Using high-speed videography in anesthetized mice, we characterize the amplitude of whisker protractions evoked by varying the intensity, duration, and frequency of optogenetic stimulation. Recordings from primary somatosensory cortex (S1) in anesthetized mice indicated that optogenetic whisker pad stimulation evokes robust yet longer latency responses than mechanical whisker stimulation. In head-fixed mice trained to report optogenetic whisker pad stimulation, psychometric curves showed similar dependence on stimulus duration as evoked whisker movements and S1 activity. Furthermore, optogenetic stimulation of S1 in expert mice was sufficient to substitute for peripheral stimulation. We conclude that whisker protractions evoked by optogenetic activation of whisker pad muscles results in cortical activity and sensory perception, consistent with the coding of evoked whisker movements by reafferent sensory input.

Doi:: http://dx.doi.org/10.7554/eLife.14140.001

No MeSH data available.


Related in: MedlinePlus