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Corticofugal projection patterns of whisker sensorimotor cortex to the sensory trigeminal nuclei.

Smith JB, Watson GD, Alloway KD, Schwarz C, Chakrabarti S - Front Neural Circuits (2015)

Bottom Line: We confirmed our anterograde tracing results by injecting retrograde tracers at various rostro-caudal levels within the trigeminal sensory nuclei to determine the position of retrogradely labeled cortical cells with respect to S1 barrel cortex.Our results demonstrate that S1 and S2 projections terminate in largely overlapping regions but show some significant differences.Contrary to the view that sensory gating could be mediated by differential activation of inhibitory interconnections between the spinal trigeminal subnuclei, we observed that projections from S1 and S2 are largely overlapping in these subnuclei despite the differences noted earlier.

View Article: PubMed Central - PubMed

Affiliation: Department of Engineering Science and Mechanics, Pennsylvania State University University Park, PA, USA ; Center for Neural Engineering, Huck Institute of Life Sciences, Pennsylvania State University University Park, PA, USA.

ABSTRACT
The primary (S1) and secondary (S2) somatosensory cortices project to several trigeminal sensory nuclei. One putative function of these corticofugal projections is the gating of sensory transmission through the trigeminal principal nucleus (Pr5), and some have proposed that S1 and S2 project differentially to the spinal trigeminal subnuclei, which have inhibitory circuits that could inhibit or disinhibit the output projections of Pr5. Very little, however, is known about the origin of sensorimotor corticofugal projections and their patterns of termination in the various trigeminal nuclei. We addressed this issue by injecting anterograde tracers in S1, S2 and primary motor (M1) cortices, and quantitatively characterizing the distribution of labeled terminals within the entire rostro-caudal chain of trigeminal sub-nuclei. We confirmed our anterograde tracing results by injecting retrograde tracers at various rostro-caudal levels within the trigeminal sensory nuclei to determine the position of retrogradely labeled cortical cells with respect to S1 barrel cortex. Our results demonstrate that S1 and S2 projections terminate in largely overlapping regions but show some significant differences. Whereas S1 projection terminals tend to cluster within the principal trigeminal (Pr5), caudal spinal trigeminal interpolaris (Sp5ic), and the dorsal spinal trigeminal caudalis (Sp5c), S2 projection terminals are distributed in a continuum across all trigeminal nuclei. Contrary to the view that sensory gating could be mediated by differential activation of inhibitory interconnections between the spinal trigeminal subnuclei, we observed that projections from S1 and S2 are largely overlapping in these subnuclei despite the differences noted earlier.

No MeSH data available.


Related in: MedlinePlus

Corticofugal terminal counts in the trigeminal sensory nuclei following dual tracer injections in S1 and S2. Bar graph showing the total number of labeled terminals resulting from anterograde tracer injections into S1 (blue) and S2 (red) whisker representations, normalized by the total number of terminals resulting from each injection, averaged across animals (n = 3). Brackets indicate standard error of the mean.
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Figure 3: Corticofugal terminal counts in the trigeminal sensory nuclei following dual tracer injections in S1 and S2. Bar graph showing the total number of labeled terminals resulting from anterograde tracer injections into S1 (blue) and S2 (red) whisker representations, normalized by the total number of terminals resulting from each injection, averaged across animals (n = 3). Brackets indicate standard error of the mean.

Mentions: We next counted the number of labeled terminals originating from S1 and S2 in the various trigeminal sensory nuclei after normalizing each by the total number of terminals resulting from that particular injection (Figure 3). The overall similar pattern of S1 and S2 labeling across the different nuclei was reflected in these counts which showed similar distributions, with the highest number of corticofugal projections terminating in Sp5c, Sp5ic and Pr5, in that order. A one way ANOVA showed that this difference across nuclei was statistically significant for both S1 (F = 70.22; p < 10e−6) and S2 terminals (F = 55.11; p < 10e−6). Within each nucleus, however, there were no significant differences between S1 and S2 terminal counts.


Corticofugal projection patterns of whisker sensorimotor cortex to the sensory trigeminal nuclei.

Smith JB, Watson GD, Alloway KD, Schwarz C, Chakrabarti S - Front Neural Circuits (2015)

Corticofugal terminal counts in the trigeminal sensory nuclei following dual tracer injections in S1 and S2. Bar graph showing the total number of labeled terminals resulting from anterograde tracer injections into S1 (blue) and S2 (red) whisker representations, normalized by the total number of terminals resulting from each injection, averaged across animals (n = 3). Brackets indicate standard error of the mean.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4588702&req=5

Figure 3: Corticofugal terminal counts in the trigeminal sensory nuclei following dual tracer injections in S1 and S2. Bar graph showing the total number of labeled terminals resulting from anterograde tracer injections into S1 (blue) and S2 (red) whisker representations, normalized by the total number of terminals resulting from each injection, averaged across animals (n = 3). Brackets indicate standard error of the mean.
Mentions: We next counted the number of labeled terminals originating from S1 and S2 in the various trigeminal sensory nuclei after normalizing each by the total number of terminals resulting from that particular injection (Figure 3). The overall similar pattern of S1 and S2 labeling across the different nuclei was reflected in these counts which showed similar distributions, with the highest number of corticofugal projections terminating in Sp5c, Sp5ic and Pr5, in that order. A one way ANOVA showed that this difference across nuclei was statistically significant for both S1 (F = 70.22; p < 10e−6) and S2 terminals (F = 55.11; p < 10e−6). Within each nucleus, however, there were no significant differences between S1 and S2 terminal counts.

Bottom Line: We confirmed our anterograde tracing results by injecting retrograde tracers at various rostro-caudal levels within the trigeminal sensory nuclei to determine the position of retrogradely labeled cortical cells with respect to S1 barrel cortex.Our results demonstrate that S1 and S2 projections terminate in largely overlapping regions but show some significant differences.Contrary to the view that sensory gating could be mediated by differential activation of inhibitory interconnections between the spinal trigeminal subnuclei, we observed that projections from S1 and S2 are largely overlapping in these subnuclei despite the differences noted earlier.

View Article: PubMed Central - PubMed

Affiliation: Department of Engineering Science and Mechanics, Pennsylvania State University University Park, PA, USA ; Center for Neural Engineering, Huck Institute of Life Sciences, Pennsylvania State University University Park, PA, USA.

ABSTRACT
The primary (S1) and secondary (S2) somatosensory cortices project to several trigeminal sensory nuclei. One putative function of these corticofugal projections is the gating of sensory transmission through the trigeminal principal nucleus (Pr5), and some have proposed that S1 and S2 project differentially to the spinal trigeminal subnuclei, which have inhibitory circuits that could inhibit or disinhibit the output projections of Pr5. Very little, however, is known about the origin of sensorimotor corticofugal projections and their patterns of termination in the various trigeminal nuclei. We addressed this issue by injecting anterograde tracers in S1, S2 and primary motor (M1) cortices, and quantitatively characterizing the distribution of labeled terminals within the entire rostro-caudal chain of trigeminal sub-nuclei. We confirmed our anterograde tracing results by injecting retrograde tracers at various rostro-caudal levels within the trigeminal sensory nuclei to determine the position of retrogradely labeled cortical cells with respect to S1 barrel cortex. Our results demonstrate that S1 and S2 projections terminate in largely overlapping regions but show some significant differences. Whereas S1 projection terminals tend to cluster within the principal trigeminal (Pr5), caudal spinal trigeminal interpolaris (Sp5ic), and the dorsal spinal trigeminal caudalis (Sp5c), S2 projection terminals are distributed in a continuum across all trigeminal nuclei. Contrary to the view that sensory gating could be mediated by differential activation of inhibitory interconnections between the spinal trigeminal subnuclei, we observed that projections from S1 and S2 are largely overlapping in these subnuclei despite the differences noted earlier.

No MeSH data available.


Related in: MedlinePlus