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Differential effects of tactile high- and low-frequency stimulation on tactile discrimination in human subjects.

Ragert P, Kalisch T, Bliem B, Franzkowiak S, Dinse HR - BMC Neurosci (2008)

Bottom Line: T-HFS-effects were stable for at least 24 hours whereas t-LFS-induced changes recovered faster.No changes were observed when the stimulated area was very small (< 1 mm2) indicating special requirements for spatial summation.Our results demonstrate differential effects of such protocols in a frequency specific manner that might be related to LTP- and LTD-like changes in human subjects.

View Article: PubMed Central - HTML - PubMed

Affiliation: Institute for Neuroinformatics, Department of Theoretical Biology, Experimental Neurobiology Lab, Ruhr-University, 44780 Bochum, Germany. patrick.ragert@uni-duesseldorf.de

ABSTRACT

Background: Long-term potentiation (LTP) and long-term depression (LTD) play important roles in mediating activity-dependent changes in synaptic transmission and are believed to be crucial mechanisms underlying learning and cortical plasticity. In human subjects, however, the lack of adequate input stimuli for the induction of LTP and LTD makes it difficult to study directly the impact of such protocols on behavior.

Results: Using tactile high- and low-frequency stimulation protocols in humans, we explored the potential of such protocols for the induction of perceptual changes. We delivered tactile high-frequency and low-frequency stimuli (t-HFS, t-LFS) to skin sites of approximately 50 mm2 on the tip of the index finger. As assessed by 2-point discrimination, we demonstrate that 20 minutes of t-HFS improved tactile discrimination, while t-LFS impaired performance. T-HFS-effects were stable for at least 24 hours whereas t-LFS-induced changes recovered faster. While t-HFS changes were spatially very specific with no changes on the neighboring fingers, impaired tactile performance after t-LFS was also observed on the right middle-finger. A central finding was that for both t-LFS and t-HFS perceptual changes were dependent on the size of the stimulated skin area. No changes were observed when the stimulated area was very small (< 1 mm2) indicating special requirements for spatial summation.

Conclusion: Our results demonstrate differential effects of such protocols in a frequency specific manner that might be related to LTP- and LTD-like changes in human subjects.

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Related in: MedlinePlus

Psychophysical effect of large-field t-LFS on tactile discrimination thresholds of the right d2. Average data from all subjects of group 2 (n = 13). Dots represent mean thresholds, boxes show standard errors, and whiskers correspond to the standard deviation. Time of t-LFS application (20 minutes) on the right d2 is indicated by an arrow. Shown are the results from 4 consecutive sessions before LFS was applied. After session s4 (s4 = pre condition), t-LFS was applied. After t-LFS, discrimination thresholds were significantly increased, indicating impaired tactile performance. 24 hours after termination of t-LFS, discrimination thresholds recovered to baseline conditions. Reassessment of thresholds 1 week later revealed stable performance.
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Figure 5: Psychophysical effect of large-field t-LFS on tactile discrimination thresholds of the right d2. Average data from all subjects of group 2 (n = 13). Dots represent mean thresholds, boxes show standard errors, and whiskers correspond to the standard deviation. Time of t-LFS application (20 minutes) on the right d2 is indicated by an arrow. Shown are the results from 4 consecutive sessions before LFS was applied. After session s4 (s4 = pre condition), t-LFS was applied. After t-LFS, discrimination thresholds were significantly increased, indicating impaired tactile performance. 24 hours after termination of t-LFS, discrimination thresholds recovered to baseline conditions. Reassessment of thresholds 1 week later revealed stable performance.

Mentions: We assessed the outcome of large-field t-LFS on 2-point discrimination in 13 right-handed subjects. All subjects achieved a stable baseline performance, as estimated from repeated assessment of thresholds over 4 consecutive sessions (rmANOVA with factor SESSION F(3,36) = 0.052; p = 0.984, see Fig. 1 and 5). Under pre condition, discrimination thresholds were 1.57 ± 0.06 mm for the right d2. After 20 min of t-LFS, discrimination performance of the right d2 was impaired in all subjects as indicated by a significant increase in discrimination thresholds of 0.15 ± 0.04 mm, from 1.57 ± 0.06 mm to 1.72 ± 0.04 mm (rmANOVA with factor SESSION F(1,12) = 10.608; p = 0.007, see Fig. 5). Linear correlation analysis (Pearson correlation coefficient) revealed no significant relation between the individual performance before stimulation was applied (pre-condition) and the individual change in performance (r = 0.485; p = 0.093; n = 13). Analysis of the time course of stability of the effects revealed that discrimination thresholds recovered to baseline conditions 24 h after termination of t-LFS (rmANOVA with factor SESSION (pre vs. rec, n = 13) F(1,12) = 1.209; p = 0.293) implying that the t-LFS-induced impairment was less persistent than the improvement observed after t-HFS. Additional measurements one week after LFS application showed that discrimination thresholds remained unchanged as compared to baseline conditions (rmANOVA with factor SESSION (pre vs. rec 1 week, n = 13) F(1,12) = 0.958; p = 0.347, see Fig. 5). The decline of discrimination performance was confirmed by calculation of d'prime. We found a decrease after t-LFS from 2.29 ± 0.08 (pre) to 2.11 ± 0.08 (post). Values returned to baseline 24 hours after stimulation (2.27 ± 0.08) and remained stable after 1 week (2.32 ± 0.10).


Differential effects of tactile high- and low-frequency stimulation on tactile discrimination in human subjects.

Ragert P, Kalisch T, Bliem B, Franzkowiak S, Dinse HR - BMC Neurosci (2008)

Psychophysical effect of large-field t-LFS on tactile discrimination thresholds of the right d2. Average data from all subjects of group 2 (n = 13). Dots represent mean thresholds, boxes show standard errors, and whiskers correspond to the standard deviation. Time of t-LFS application (20 minutes) on the right d2 is indicated by an arrow. Shown are the results from 4 consecutive sessions before LFS was applied. After session s4 (s4 = pre condition), t-LFS was applied. After t-LFS, discrimination thresholds were significantly increased, indicating impaired tactile performance. 24 hours after termination of t-LFS, discrimination thresholds recovered to baseline conditions. Reassessment of thresholds 1 week later revealed stable performance.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2244613&req=5

Figure 5: Psychophysical effect of large-field t-LFS on tactile discrimination thresholds of the right d2. Average data from all subjects of group 2 (n = 13). Dots represent mean thresholds, boxes show standard errors, and whiskers correspond to the standard deviation. Time of t-LFS application (20 minutes) on the right d2 is indicated by an arrow. Shown are the results from 4 consecutive sessions before LFS was applied. After session s4 (s4 = pre condition), t-LFS was applied. After t-LFS, discrimination thresholds were significantly increased, indicating impaired tactile performance. 24 hours after termination of t-LFS, discrimination thresholds recovered to baseline conditions. Reassessment of thresholds 1 week later revealed stable performance.
Mentions: We assessed the outcome of large-field t-LFS on 2-point discrimination in 13 right-handed subjects. All subjects achieved a stable baseline performance, as estimated from repeated assessment of thresholds over 4 consecutive sessions (rmANOVA with factor SESSION F(3,36) = 0.052; p = 0.984, see Fig. 1 and 5). Under pre condition, discrimination thresholds were 1.57 ± 0.06 mm for the right d2. After 20 min of t-LFS, discrimination performance of the right d2 was impaired in all subjects as indicated by a significant increase in discrimination thresholds of 0.15 ± 0.04 mm, from 1.57 ± 0.06 mm to 1.72 ± 0.04 mm (rmANOVA with factor SESSION F(1,12) = 10.608; p = 0.007, see Fig. 5). Linear correlation analysis (Pearson correlation coefficient) revealed no significant relation between the individual performance before stimulation was applied (pre-condition) and the individual change in performance (r = 0.485; p = 0.093; n = 13). Analysis of the time course of stability of the effects revealed that discrimination thresholds recovered to baseline conditions 24 h after termination of t-LFS (rmANOVA with factor SESSION (pre vs. rec, n = 13) F(1,12) = 1.209; p = 0.293) implying that the t-LFS-induced impairment was less persistent than the improvement observed after t-HFS. Additional measurements one week after LFS application showed that discrimination thresholds remained unchanged as compared to baseline conditions (rmANOVA with factor SESSION (pre vs. rec 1 week, n = 13) F(1,12) = 0.958; p = 0.347, see Fig. 5). The decline of discrimination performance was confirmed by calculation of d'prime. We found a decrease after t-LFS from 2.29 ± 0.08 (pre) to 2.11 ± 0.08 (post). Values returned to baseline 24 hours after stimulation (2.27 ± 0.08) and remained stable after 1 week (2.32 ± 0.10).

Bottom Line: T-HFS-effects were stable for at least 24 hours whereas t-LFS-induced changes recovered faster.No changes were observed when the stimulated area was very small (< 1 mm2) indicating special requirements for spatial summation.Our results demonstrate differential effects of such protocols in a frequency specific manner that might be related to LTP- and LTD-like changes in human subjects.

View Article: PubMed Central - HTML - PubMed

Affiliation: Institute for Neuroinformatics, Department of Theoretical Biology, Experimental Neurobiology Lab, Ruhr-University, 44780 Bochum, Germany. patrick.ragert@uni-duesseldorf.de

ABSTRACT

Background: Long-term potentiation (LTP) and long-term depression (LTD) play important roles in mediating activity-dependent changes in synaptic transmission and are believed to be crucial mechanisms underlying learning and cortical plasticity. In human subjects, however, the lack of adequate input stimuli for the induction of LTP and LTD makes it difficult to study directly the impact of such protocols on behavior.

Results: Using tactile high- and low-frequency stimulation protocols in humans, we explored the potential of such protocols for the induction of perceptual changes. We delivered tactile high-frequency and low-frequency stimuli (t-HFS, t-LFS) to skin sites of approximately 50 mm2 on the tip of the index finger. As assessed by 2-point discrimination, we demonstrate that 20 minutes of t-HFS improved tactile discrimination, while t-LFS impaired performance. T-HFS-effects were stable for at least 24 hours whereas t-LFS-induced changes recovered faster. While t-HFS changes were spatially very specific with no changes on the neighboring fingers, impaired tactile performance after t-LFS was also observed on the right middle-finger. A central finding was that for both t-LFS and t-HFS perceptual changes were dependent on the size of the stimulated skin area. No changes were observed when the stimulated area was very small (< 1 mm2) indicating special requirements for spatial summation.

Conclusion: Our results demonstrate differential effects of such protocols in a frequency specific manner that might be related to LTP- and LTD-like changes in human subjects.

Show MeSH
Related in: MedlinePlus