Controversy in statistical analysis of functional magnetic resonance imaging data

To test the validity of statistical methods for fMRI data analysis, Eklund et al. (1) used, for the first time, large-scale experimental data rather than simulated data. Using resting-state fMRI measurements to represent a null hypothesis of no task-induced activation, the authors compare familywise error rates for voxel-based and cluster-based inferences for both parametric and nonparametric methods. Eklund et al.’s study used three fMRI statistical analysis packages. They found that, for a target familywise error rate of 5%, the parametric methods gave invalid cluster-based inferences and conservative voxel-based inferences

Boxplots and graphs.

<p>Neither last <b>(A)</b>, nor two-year mean <b>(B)</b>, HbA1c values differed between subjects with normal and impaired vibrotactile sense on at least one site on the foot. The duration of disease <b>(C)</b> did not statistically differ between subjects with normal and impaired vibrotactile sense on at least one site on the foot. However, among subjects with impaired vibrotactile sense, on at least one site of the foot, disease onset age was significantly higher <b>(D)</b>. The frequency of subjects with impaired vibrotactile sense, darker areas of the histograms, did not differ among boys and girls <b>(E)</b>, but subjects treated with MDI were more likely to have impaired vibrotactile sense <b>(F)</b>, than subjects treated with CSII. Among the 13 subjects with impaired vibrotactile sense four were receiving CSII treatment, and nine MDI treatment.</p

Impaired vibrotactile sense in children and adolescents with type 1 diabetes – Signs of peripheral neuropathy

<div><p>Objective</p><p>To investigate whether multi-frequency vibrometry can identify individuals with elevated vibration perception thresholds (VPTs), reflecting impaired vibrotactile sense, among children and adolescents with type 1 diabetes.</p><p>Methods</p><p>In 72 pediatric patients with type 1 diabetes, VPTs were evaluated for seven frequencies on two sites of the hand, and five frequencies on two sites of the foot. Z-scores, based on previously collected reference data, were calculated. Perception to light touch was investigated using monofilaments. Subjects’ characteristics were analyzed in comparison to normal and impaired vibrotactile sense.</p><p>Results</p><p>Subjects’ median age, disease duration and age at disease onset were 12.8, 5.3 and 6.9 years, respectively. A total of 13 out of 72 (18%) subjects had impaired vibrotactile sense on at least one foot site. Impaired vibrotactile sense was more common among subjects treated with multiple daily insulin injections (MDI) compared to subjects treated with continuous subcutaneous insulin infusion (CSII) (p = 0.013). Age at disease onset was higher among subjects with impaired vibrotactile sense (p = 0.046). No significant correlations were found with gender, HbA1c or duration of diabetes.</p><p>Conclusions</p><p>Impaired vibrotactile sense, mirroring diabetic peripheral neuropathy, was found in 1/5 of the children and adolescents in the study, and was more common in patients treated with MDI than in subjects treated with CSII.</p></div

VPT graphs.

<p>These graphs show the number of subjects presenting with pathological (>1.96), and non-pathological (<1.96), z-scores at all examined frequencies and sites on the index <b>(A)</b> and little <b>(B)</b> fingers of the hand and on MTH 1 <b>(C)</b> and MTH 5 <b>(D)</b> on the foot. Z-scores are calculated based on normative values previously collected from healthy children and adolescents [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0196243#pone.0196243.ref021" target="_blank">21</a>].</p

Vibrograms showing normal and abnormal VPTs.

<p>The vibrograms presented all arise from subjects with type 1 diabetes. (A) and (C) shows vibrograms reflecting normal vibrotactile sense, obtained from a 9-year old girl, at index and little fingers respectively. (B) and (D) shows vibrograms mirroring impaired vibrotactile sense, at index and little fingers respectively, in a 9-year old girl. (E) and (G) shows normal vibrograms, obtained from a 14-year old boy, at MTH 1 and MTH 5 respectively. (F) and (H) shows vibrograms, obtained from a 14-year old boy, mirroring impaired vibrotactile sense, at MTH 1 and MTH 5 respectively.</p

Characteristics of subjects.

<p>Characteristics of subjects.</p

Height and weight of the 269 healthy children included in the study.

<p>Values are means and 95% confidence intervals in parenthesis.</p><p>^a Data missing in two subjects.</p><p>Height and weight of the 269 healthy children included in the study.</p

Vibration perception thresholds at the heel in the sole of the foot at different frequencies in 269 healthy girls and boys.

<p>Values, expressed in dB (relative to 10^-6 m/s²⁾, are means and 95% confidence intervals in parenthesis.</p><p>Vibration perception thresholds at the heel in the sole of the foot at different frequencies in 269 healthy girls and boys.</p

Vibration perception thresholds in the finger pulp of little finger at different frequencies in 269 healthy girls and boys.

<p>Values, expressed in dB (relative to 10^-6 m/s²⁾, are means and 95% confidence intervals in parenthesis.</p><p>Vibration perception thresholds in the finger pulp of little finger at different frequencies in 269 healthy girls and boys.</p

Photo showing the experimental set-up.

<p>The subject is sitting with the arm/hand and leg/foot, respectively in a relaxed position (A). The investigated skin area (index or little finger, head or the first or fifth metatarsal bone or heel) is placed on a vibrating probe (insert). The subject regulates the intensity of the vibration by pressure a button on a remote control (arrow) in his/her contralateral hand (B). The result is a tactilogram (see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0119753#pone.0119753.g002" target="_blank">Fig. 2</a>). The probe for the foot is shown in (C) and the green light (D) indicates that the pressure is appropriate on the investigated area. The person on the photo is <i>not</i> one of the subjects in the study.</p