Brain Activations Induced by Reflexology at the Left Great Toe.

Tang Mei Yee

HKU Theses Online (HKUTO).

Submitted for the degree of Master of Philosophy at the University of Hong Kong in August 2006

reflexology, fMRI, big toe, reflexology charts, brain,

Part of  “Medical Imaging: Applications of Functional Magnetic Resonance Imaging and the Development of a Magnetic Resonance Compatible Ultrasound System”

We tried to use fMRI to investigate the neural pathway of reflexology applied at the feet, which may help in explaining the underlining principles and quantify the validity of this therapy.

In this part of the study, we investigate the brain activation induced by massaging the inner lateral corner of the left great toe at lower limb. According to reflex zone therapy, the great toe corresponds to the brain and the lateral corner of the great toe corresponds to the temporal lobe of the cerebral cortex [16]. We hypothesis there is a positive correlation between stimulating this zone and activations at right temporal lobe of the brain.

15 healthy volunteers were recruited for this study and 13 set of data (mean age = 25.8 ±3.09) were successfully collected for analysis. 2 set of data were discarded because of severe head motions along the z directions observed during data analysis. All subjects did not receive any foot reflexology or physiotherapy in the past 2 weeks before the study and did not have the history of fracture at the left foot sole.

All volunteers were first informed with written consent and explained in details the experimental procedures, so as to screen out unqualified volunteers and minimize anxiety of volunteers which may affect the results of the study.

MRI scans were carried out in a 1.5T MR system (Signa Horizon Echo Speed with version 5.51 software, General Electric Medical Systems, Milwaukee, WI, USA) at
St. Paul’s Hospital, Hong Kong. A quadrature head coil was used for this study.

After the volunteer was advanced to the magnet bore, a 9-slices-3- planes localizer scan was first obtained which was used for subsequence scans planning. fMRI scan was then followed with the parameters: Gradient Echo EPI, TR=2s, TE=50ms, NEX=1, FOV=240mm, slice thickness = 8mm, no. of slices =16, matrix size = 64×64, number of dynamics = 64. Coronal oblique slices were obtained perpendicular to the Anterior Commissure and Posterior Commissure (AC-PC) line to ensure better visualization of the temporal lobe. Noted that the first 4 dynamics were dummy scans and were discarded to ensure the EPI sequence reached a steady state magnetization.

Fig. 3.1 (a) shows the position at which the pressure force was applied. Fig. 3.2 (b) shows the activation paradigm. The activation paradigm was a block design with 2 rest stages and 2 massaging stimuli stages. M represents massage and R represents rest, at 30 seconds (15 dynamics) intervals. During the M stimulation stage, massage stimulation was applied continuously at the inner lateral corner of the left great toe, with application of chamomile essential oil as lubricant. Pressing force was tested at the right great toe before each scan, such that a greatest acceptable force without inducing pain at the toe could be applied to each volunteer. The fMRI scan lasted for 2 minutes and 60 volumetric images (with dummy discarded) were collected for each volunteer. High resolution Anatomical T1 weighted image with parameters: Spin Echo, TR = 475ms, TE=minimum full, matrix = 256×256 was also obtained for overlaying the activation maps obtained from the analysis of the fMRI data onto it so as to clearly visualize the region of activations.

Fig. 3.2 shows the fMRI paradigm convolved with HRF function and BOLD response of a volunteer at coordinate [60, 2, 4] in MNI space, which is corresponding to BA22. The red line shows the block design paradigm convolved with the HRF function, which is the expected pattern to be observed, while the blue dots represent the true activations along time at that co-ordinate due to the stimulus.

Fig. 3.3 shows the brain activation map from the group test overlaid on the T1 template. Activations were localized at the (a) left cerebellum; (b-c) left and right superior temporal gyrus, Brodmann’s area (BA) (BA 41-42 and 22); (d) bilateral inferior parietal lobe (BA 40) and (e) right postcentral gyrus (BA 3).

The local maximum statistic intensity values of each clusters are (a) t = 3.01 at leftcerebellum, (b-c) t = 10.08 at right superior temporal gyrus; (d) t = 4.78 at right inferior parietal lobe and (e) t = 4.82 at right postcentral gyrus, with p<0.001.

Activation at temporal gyrus is strongest, and it is stronger at right hemisphere than that at left (t=10.08 vs. t=6.08; p<0.001).

The activation area at (a) left cerebellum is probably the sensory-motor signal pathway which is used for conducting impulses between the sensory receptors at left great toe to the primary sensory area in cerebral cortex for sensation perception.

Activations located at (d) and (e) at the inferior parietal lobule (BA40) and right postcentral gyrus (BA 3) are related to the movement of lower limbs during massage and the tactile stimulation of the left great toe. Inferior parietal lobule (BA40) is the secondary somato-sensory cortex (S-II) while postcentral gyrus (BA3) is the primary somato-sensory cortex(S-I). Activations found in these areas are expected because whenever mechanical force was applied to the great toe, the volunteer must experience a tactile sensation and the foot sole was pressed and moved passively by the practitioner.

For the strong activations found at the right superior temporal gyrus, strongest activations were found at the BA41 and BA42, which are the primary auditory cortex. Activation was also found in BA22 (right hemisphere) which is related to working memory and language function. However, there was no auditory stimulation involved in our tasks and there was no sudden change in background acoustic noise (sound) throughout the scanning. Therefore, it could be concluded that the activation in these area was due to our massage tasks.

The above results showed that there is a positive relationship between massaging the mentioned area in reflex zone therapy to activations at the temporal lobe, especially at the superior temporal gyrus. These matched with our hypothesis that massage applied at the inner lateral corner of the left great toe activated the right temporal lobe of the brain.

Therefore, fMRI could be a useful tool to investigate the neural pathway of foot reflexology. However, fMRI could only show that mechanical force applied at that reflex zone could activate the auditory cortex in the brain. Further investigations needed to be done to verify whether massage applied at that reflex zone could be used as a treatment point for auditory and language related diseases.

Tang, M. Y. (2006). Medical imaging: applications of functional magnetic resonance imaging and the development of a magnetic resonancecompatible ultrasound system. HKU Theses Online (HKUTO).