Limits...
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

Analysis of retraction and protraction movements for individual whiskers.(A) Schematic of experiment as in Figure 1, with video image of tracked whiskers. (B) Color maps showing the peak whisker movement evoked by a 20 ms, 460 nm light spot located at various positions on the whisker pad. For each colormap, the identity of the tracked whisker is indicated above. The origin (0, 0) was defined a rostral area near the C4/D4 whiskers that evoked reliable protractions; this site was used in most additional experiments in this study. Stimulation of caudal-inferior sites, on the other hand, evoked mixed movement types in different whiskers, evident as diverse (yellow/red) colors on the color maps. (C) Time courses of movements evoked for 6 tracked whiskers (B1, B2, B3, C3, C4, D2) at each of three stimulation sites on the whisker pad, including the rostral protraction area (0, 0) and two caudal-inferior areas [(-2, -2) and (-3, -2)]. Note that movements measured as near-zero for some whiskers at some sites (e.g., C4 at -2, -2) might result from co-contraction of different muscle types that cause opposing retractions and protractions.DOI:http://dx.doi.org/10.7554/eLife.14140.004
© Copyright Policy
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4940159&req=5

fig1s1: Analysis of retraction and protraction movements for individual whiskers.(A) Schematic of experiment as in Figure 1, with video image of tracked whiskers. (B) Color maps showing the peak whisker movement evoked by a 20 ms, 460 nm light spot located at various positions on the whisker pad. For each colormap, the identity of the tracked whisker is indicated above. The origin (0, 0) was defined a rostral area near the C4/D4 whiskers that evoked reliable protractions; this site was used in most additional experiments in this study. Stimulation of caudal-inferior sites, on the other hand, evoked mixed movement types in different whiskers, evident as diverse (yellow/red) colors on the color maps. (C) Time courses of movements evoked for 6 tracked whiskers (B1, B2, B3, C3, C4, D2) at each of three stimulation sites on the whisker pad, including the rostral protraction area (0, 0) and two caudal-inferior areas [(-2, -2) and (-3, -2)]. Note that movements measured as near-zero for some whiskers at some sites (e.g., C4 at -2, -2) might result from co-contraction of different muscle types that cause opposing retractions and protractions.DOI:http://dx.doi.org/10.7554/eLife.14140.004

Mentions: We first characterized the whisker movements evoked by a 2–3 mm diameter, 460 nm spot of light aimed at different regions of the whisker pad in anesthetized Emx1-Cre;Ai27D mice (isoflurane 0.8–1.5%) (Figure 1A). The direction of movement depended on the location of the spot, such that illumination of the rostral pad resulted in whisker protraction, while illumination of the caudal-inferior pad resulted in whisker retraction (Figure 1B). Stimulation at some locations elicited more complex combinations of protractions and retractions from individual whiskers (Figure 1—figure supplement 1; see also Video 1, Video 2, Video 3). These regional variations in light-evoked protraction and retraction were qualitatively similar in 5 of 5 mice tested. In the rest of this study, we focused on whisker protractions evoked by optogenetic activation of the rostral whisker pad.10.7554/eLife.14140.003Figure 1.ChR2/tdTomato expression in whisker pad muscles and optical activation of whisker movements in Emx1-Cre;Ai27D mice.


Peripheral optogenetic stimulation induces whisker movement and sensory perception in head-fixed mice
Analysis of retraction and protraction movements for individual whiskers.(A) Schematic of experiment as in Figure 1, with video image of tracked whiskers. (B) Color maps showing the peak whisker movement evoked by a 20 ms, 460 nm light spot located at various positions on the whisker pad. For each colormap, the identity of the tracked whisker is indicated above. The origin (0, 0) was defined a rostral area near the C4/D4 whiskers that evoked reliable protractions; this site was used in most additional experiments in this study. Stimulation of caudal-inferior sites, on the other hand, evoked mixed movement types in different whiskers, evident as diverse (yellow/red) colors on the color maps. (C) Time courses of movements evoked for 6 tracked whiskers (B1, B2, B3, C3, C4, D2) at each of three stimulation sites on the whisker pad, including the rostral protraction area (0, 0) and two caudal-inferior areas [(-2, -2) and (-3, -2)]. Note that movements measured as near-zero for some whiskers at some sites (e.g., C4 at -2, -2) might result from co-contraction of different muscle types that cause opposing retractions and protractions.DOI:http://dx.doi.org/10.7554/eLife.14140.004
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4940159&req=5

fig1s1: Analysis of retraction and protraction movements for individual whiskers.(A) Schematic of experiment as in Figure 1, with video image of tracked whiskers. (B) Color maps showing the peak whisker movement evoked by a 20 ms, 460 nm light spot located at various positions on the whisker pad. For each colormap, the identity of the tracked whisker is indicated above. The origin (0, 0) was defined a rostral area near the C4/D4 whiskers that evoked reliable protractions; this site was used in most additional experiments in this study. Stimulation of caudal-inferior sites, on the other hand, evoked mixed movement types in different whiskers, evident as diverse (yellow/red) colors on the color maps. (C) Time courses of movements evoked for 6 tracked whiskers (B1, B2, B3, C3, C4, D2) at each of three stimulation sites on the whisker pad, including the rostral protraction area (0, 0) and two caudal-inferior areas [(-2, -2) and (-3, -2)]. Note that movements measured as near-zero for some whiskers at some sites (e.g., C4 at -2, -2) might result from co-contraction of different muscle types that cause opposing retractions and protractions.DOI:http://dx.doi.org/10.7554/eLife.14140.004
Mentions: We first characterized the whisker movements evoked by a 2–3 mm diameter, 460 nm spot of light aimed at different regions of the whisker pad in anesthetized Emx1-Cre;Ai27D mice (isoflurane 0.8–1.5%) (Figure 1A). The direction of movement depended on the location of the spot, such that illumination of the rostral pad resulted in whisker protraction, while illumination of the caudal-inferior pad resulted in whisker retraction (Figure 1B). Stimulation at some locations elicited more complex combinations of protractions and retractions from individual whiskers (Figure 1—figure supplement 1; see also Video 1, Video 2, Video 3). These regional variations in light-evoked protraction and retraction were qualitatively similar in 5 of 5 mice tested. In the rest of this study, we focused on whisker protractions evoked by optogenetic activation of the rostral whisker pad.10.7554/eLife.14140.003Figure 1.ChR2/tdTomato expression in whisker pad muscles and optical activation of whisker movements in Emx1-Cre;Ai27D 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