The role of arm swing in gait: a combined EEG-EMG study in healthy participants and PD patients

In human gait, oscillating leg movement is accompanied by anti-phase arm swing,
which has been suggested to serve stabilization, energetic efficiency and
maintenance of the cyclic motor pattern. Although cerebral control of such
four-limb movement pattern is embedded in both cortical and subcortical
circuitry, the Supplementary motor area (SMA) seems to make a prominent
cortical contribution. The altered four-limb pattern in Parkinsonian gait is
characterized by small shuffling steps, stooped posture and reduced arm swing,
while freezing may additionally occur. Reduced SMA activation has been
associated with a wide range of impaired motor functions in Parkinson*s Disease
(PD), including these gait characteristics. Cerebral circuitry controlling the
onset and continuation of human locomotion and its pathophysiology remains to
be further identified. Most neuroimaging techniques are inappropriate to
measure brain signals during walking, making it difficult to study the
underlying neural substrates responsible for gait disturbances in PD. With the
wireless combined electroencephalography (EEG)- electromyography (EMG)
technique we can measure brain and muscle activity while participants walk
under ecologically valid circumstances, hopefully leading to more understanding
regarding the neural control of locomotion and to identification of potential
targets for medical and surgical interventions.

The primary objective is to examine the contribution of arm swing to the onset
and continuation of locomotion in healthy individuals and PD patients and to
study activity in its underlying functional brain networks. Secondary
objectives are to evaluate how brain and muscles work together during the onset
and continuation of walking and the differences in step duration, gait velocity
and walking rhythm between PD patients and healthy controls.

Observational study
Wireless combined EEG-EMG will be used to measure brain and muscle activity
during locomotion. During the experiments, participants will be fitted with a
32-channel EEG cap and EMG will be recorded from five of the major muscles
involved in locomotion (tibialis anterior, soleus, rectus femoris, biceps
femoris and gluteus medius). Moreover, accelerometers will be attached to the
lower trunk and both left and right shanks. Each participant will then execute
the following tasks:
(i) At random start-stop task (examining gait initiation), executed a) with and
b) without armswing
* Participants walk back and forth through a hallway of 150m, while the
researcher instructs the person to stop and start again thirty times at a
(pseudo-) random time point.
(ii) Straight-path walking (examining continued gait)
* Participants walk back and forth through a hallway of 100m in a straight line
a) with their arms in (normal) anti-phase with their lower limbs, b) with their
arms in-phase with their lower limbs and c) without arm swing.
Other parameters of interest (medication use and comorbidities) will be
collected from the patient*s file. Moreover, participants will be videoed
during task execution to allow visual analysis of the walking pattern and
identification of freezing of gait.
The study will consist of a pilot study and a case-control study. In the
latter, differences between the various conditions in healthy subjects serve
the primary objective, providing reference for comparison with the
characteristically changed gait in PD patients. The pilot study is used to
assess feasibility of the number of conditions to be tested in the patient
group.

Patients will not be taken off any medication, but measurements will be planned
just before taking a new dose of the medication to ensure maximum occurrence of
symptoms. There are no risks or benefits, and the burden is limited to the time
invested in the test (approximately 2 hours, with breaks).