New study protocol on freezing and vibrotactile cueing

The next publication from the project Parkinson Vibrating Socks has appeared, in the open access journal Frontiers in Neuroscience. It describes the study protocol for the neurophysiological part of the project. The subject is which changes in brain activity precede a freezing episode and whether vibrotactile cueing influences these changes.

For everyone who has been following the project for some time: what freezing of gait is, how cueing can help and why the choice falls on vibrotactile stimuli has already been explained in earlier posts. This post outlines what the new paper is about.

Background

A number of findings on the neural basis of freezing are already available. A large share comes from imaging studies in the MRI scanner, for instance using imagined movements or stepping tasks. This work has provided important evidence on the brain regions and possible mechanisms involved. What remains open is how the processes described unfold during actual walking. Mobile measurements with EEG or fNIRS have contributed initial findings here, as a rule using one of the two methods at a time.

The protocol connects to this state of research. Building on the first project publication, which showed that brain and movement data can be recorded in temporal synchrony in virtual reality, this approach is now applied to the neurophysiological question.

Methodological approach

Several levels of data are recorded simultaneously during walking:

  • EEG for electrical brain activity with high temporal resolution,
  • fNIRS for blood flow and therefore the activity of individual brain regions,
  • motion capture and force plates for each step and the forces involved.

The measurements take place in a virtual environment in which participants walk on a treadmill. Automatic doors and prescribed 360 degree turns serve as triggers for freezing, that is, situations that frequently lead to episodes in everyday life as well. This allows freezing to be elicited under controlled conditions and described using the recorded data.

Comparisons are made within the same person, in each case between walking with and without vibration as well as between freezing and unimpaired walking.

The research questions

  1. Where in the brain does freezing begin? The analysis examines brain regions that are active differently before the visible onset of freezing than during normal walking.
  2. What does the neural signature look like? The focus is on the temporal course and the frequency patterns of brain activity in the seconds beforehand.
  3. What does the cueing change? The analysis tests whether the vibrotactile stimuli attenuate these patterns and whether freezing becomes less frequent or shorter as a result.

The publication is a study protocol. It describes the planned procedure and the hypotheses, not yet any results. Publishing in advance makes the procedure traceable before data collection begins and documents the research question independently of the later outcome. The study is registered in the German Clinical Trials Register (DRKS00034584).

Relevance for practice

For therapists, the question of when a stimulus is delivered is relevant. Should it become apparent when freezing announces itself at the neural level, cueing could be applied in a more targeted way in future. For physicians, the work may contribute to the understanding of a non-invasive, low-risk addition to existing treatment approaches. For researchers, the combined use of EEG, fNIRS, kinematics and kinetics during walking is of methodological interest, since it allows measurements under conditions closer to everyday life.

The full protocol is freely accessible in Frontiers in Neuroscience.