Open Access

Erratum to: Testing the potential of a virtual reality neurorehabilitation system during performance of observation, imagery and imitation of motor actions recorded by wireless functional near-infrared spectroscopy (fNIRS)

  • Lisa Holper1, 2Email author,
  • Thomas Muehlemann1, 3,
  • Felix Scholkmann1,
  • Kynan Eng2,
  • Daniel Kiper2 and
  • Martin Wolf1
Journal of NeuroEngineering and Rehabilitation201310:16

DOI: 10.1186/1743-0003-10-16

Received: 1 February 2013

Accepted: 1 February 2013

Published: 8 February 2013

The Research to this article has been published in Journal of NeuroEngineering and Rehabilitation 2010 7:57

Correction

Following publication of our article [1], we realised that some of the statistical tests used were not appropriate. We have now conducted the appropriate statistical tests, and updated the relevant tables, figures five and six (Figures 1 and 2 here, respectively) and conclusions accordingly.
https://static-content.springer.com/image/art%3A10.1186%2F1743-0003-10-16/MediaObjects/12984_2013_Article_430_Fig1_HTML.jpg
Figure 1

Unilateral group recorded over contralateral hemisphere: shown are the Δ[O 2 Hb] amplitude changes with standard error of the mean (SEM) and statistical significances of repeated measures ANOVA.

https://static-content.springer.com/image/art%3A10.1186%2F1743-0003-10-16/MediaObjects/12984_2013_Article_430_Fig2_HTML.jpg
Figure 2

Bilateral group recorded over contra- (dark gray) and ipsilateral (light gray) hemisphere: shown are the Δ[O 2 Hb] amplitude changes with standard error of the mean (SEM) and statistical significances of repeated measures ANOVA.

For both the unilateral and the bilateral groups, analyses were recalculated.

Intra-condition differences:

  • original publication [1]: paired t-test using means per trial for unilateral and bilateral group

  • update: one-way repeated measures ANOVA using means per subject for unilateral and bilateral group

Inter-condition differences:

  • original publication [1]: one-way ANOVA using means per trial for unilateral and bilateral group

  • update: one-way repeated measures ANOVA using means per subject for unilateral and bilateral group

Conclusions

For the unilateral group (Table 1 and Figure 1), no changes in significance levels were found in Δ[O2Hb] signals. For the bilateral group (Table 2 and Figure 2), the main differences compared to the original publication are that the intra-condition differences ([O2Hb]rest versus [O2Hb]stim) for the two conditions ‘Observation Right’ (O_R, p = 0.077) and ‘Observation Left’ (O_L, p = 0.080) recorded over the ipsilateral hemisphere do not reach significant level any more. Hence, the paragraphs discussing the intra-condition significances in those two conditions (sections Observation, imagery and imitation and Bilateral oxygenation of the Discussion) are only applicable for the contralateral hemisphere. Further, in both groups changes in significance levels were found for Δ[HHb]. However, since the Discussion and Conclusion of the originally published article only focuses on the concentration changes found in Δ[O2Hb], this aspect does not change these sections.
Table 1

Unilateral group

Unilateral group [N = 15]

Observation

Motor imagery

Observation & motor imagery

Imitation

Left hemisphere (contralateral) (μmol/ l ± SD)

Mean ∆ [O2Hb]

0.06953 ± 0.1800

0.0833 ± 0.1404

0.0460 ± 0.2218

0.2309 ± 0.3212

Mean ∆ [HHb]

−0.0051 ± 0.03855

0.0356 ± 0.0771

−0.0089 ± 0.0963

0.0079 ± 0.0832

Intra-condition, ANOVA, repeated measures

   

[O2Hb] rest-stim

p = 0.157

p = 0.037*

p = 0.435

p = 0.015*

[HHb] rest-stim

p = 0.612

p = 0.097

p = 0.727

p = 0.717

Inter-condition ANOVA, repeated measures, post-hoc-tests, Bonferroni 0.05

[HHb]

[O 2 Hb]

 
 

O – MI

p = 0.347

p = 1.000

 
 

O – O&MI

p = 1.000

p = 1.000

 
 

O – IM

p = 1.000

p = 0.286

 
 

MI – O&MI

p = 0.132

p = 1.000

 
 

MI – IM

p = 1.000

p = 0.622

 
 

O&MI – IM

p = 1.000

p = 0.321

 

Main effect on condition

p = 0.253

p = 0.062

 

(Top) Mean signal amplitudes (μmol/l ± SD) of channels with significant concentration changes. Separate calculations for increases in [O2Hb], decreases in [HHb] in response to the four conditions for each group. Numbers were rounded to four decimal places. (Middle) Intra-condition statistical significance of the mean changes between [O2Hb]rest and [O2Hb]stim and [HHb]rest and [HHb]stim repeated measures ANOVA. (Bottom) Inter-condition statistical significance of mean changes of ∆ [O2Hb] and ∆ [HHb] between the four conditions using repeated measures ANOVA. Shown are post-hoc tests (with Bonferroni correction); significant values (p ≤ 0.05) are highlighted by * (observation = O, motor imagery = MI, observation & motor imagery = O & MI, imitation = IM).

Table 2

Bilateral group

Bilateral group [N = 8]

Observation right

Observation left

Imitation right

Imitation left

Left hemisphere (contralateral) (μmol/ l ± SD)

Mean ∆ [O2Hb]

0.1231 ± 0.1506

0.1231 ± 0.1507

0.3941 ± 0.4598

0.3715 ± 0.4289

Mean ∆ [HHb]

−0.0056 ± 0.0676

−0.0408 ± 0.0915

0.0371 ± 0.1131

0.0474 ± 0.0665

Intra-condition, ANOVA, repeated measures

[O2Hb] rest-stim

p = 0.044*

p = 0.047*

p = 0.025*

p = 0.038*

[HHb] rest-stim

p = 0.821

p = 0.247

p = 0.384

p = 0.084

Inter-condition, ANOVA, repeated measures, post-hoc-tests, Bonferroni 0.05

[HHb]

[O 2 Hb]

 
 

O_R – O_L

p = 1.000

p = 1.000

 
 

O_R – IM_R

p = 1.000

p = 0.519

 
 

O_R – IM_L

p = 1.000

p = 0.862

 
 

OL_ – IM_R

p = 0.227

p = 0.486

 
 

O_L – IM_L

p = 0.223

p = 0.777

 
 

IM_R – IM_L

p = 1.000

p = 1.000

 

Main effect on condition

p = 0.072

p = 0.119

 

Right hemisphere (ipsilateral) (μmol/ l ± SD)

Mean ∆ [O2Hb]

0.1541 ± 0.0735

0.1957 ± 0.1957

0.4036 ± 0.2097

1.3728 ± 1.6143

Mean ∆ [HHb]

−0.0113 ± 0.0334

0.0068 ± 0.0274

0.0235 ± 0.0402

0.7016 ± 1.9167

Intra-condition, ANOVA, repeated measures

   

[O2Hb] rest-stim

p = 0.077

p = 0.080

p = 0.002*

p = 0.032*

[HHb] rest-stim

p = 0.367

p = 0.502

p = 0.142

p = 0.335

Inter-condition, ANOVA, repeated measures, post-hoc-tests, Bonferroni 0.05

[HHb]

[O 2 Hb]

 
 

O_R – O_L

p = 1.000

p = 1.000

 
 

O_R – IM_R

p = 0.445

p = 0.014*

 
 

O_R – IM_L

p = 1.000

p = 0.324

 
 

OL_ – IM_R

p = 1.000

p = 0.015*

 
 

O_L – IM_L

p = 1.000

p = 0.231

 
 

IM_R – IM_L

p = 1.000

p = 0.710

 

Main effect on condition

p = 0.384

p = 0.008*

 

(Top) Mean signal amplitudes (μmol/l ± SD) of channels with significant concentration changes. Separate calculations for increases in [O2Hb], decreases in [HHb] in response to the four conditions for each group. Numbers were rounded to four decimal places. (Middle) Intra-condition statistical significance of the mean change between [O2Hb]rest and [O2Hb]stim and [HHb]rest and [HHb]stim using repeated measures ANOVA. (Bottom) Inter-condition statistical significance of mean changes of ∆ [O2Hb] and ∆ [HHb] between the four conditions using repeated measures ANOVA. Shown are post-hoc tests (with Bonferroni correction); significant values (p ≤ 0.05) are highlighted by * (observation left = O_L, observation right = O_R, imitation left = IM_L, imitation right = IM_R).

Declarations

Authors’ Affiliations

(1)
Biomedical Optics Research Laboratory (BORL), Division of Neonatology, Department of Obstetrics and Gynecology, University Hospital Zurich
(2)
Institute of Neuroinformatics (INI), University of Zurich and ETH Zurich
(3)
Molecular Imaging and Functional Pharmacology, Institute for Biomedical Engineering, ETH and University of Zurich

References

  1. Holper L, et al: Testing the potential of a virtual reality neurorehabilitation system during performance of observation, imagery and imitation of motor actions recorded by wireless functional near-infrared spectroscopy (fNIRS). J Neuroeng Rehabil. 2012, 7: 57-View Article

Copyright

© Holper et al; licensee BioMed Central Ltd. 2013

This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://​creativecommons.​org/​licenses/​by/​2.​0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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