Eight sessions of non-invasive brain stimulation improve postural response in people with Parkinson’s disease

A study conducted at São Paulo State University indicates that the non-invasive technique provides lasting benefits by reducing the risk of falls.

By Maria Fernanda Ziegler  |  Agência FAPESP – A Brazilian study published in the journal Gait & Posture found that eight sessions of transcranial direct-current stimulation (tDCS) improve the postural response of people with Parkinson’s disease, thereby reducing the risk of falls.

The non-invasive technique involves applying a low-intensity, continuous electrical current to the head to modulate brain activity. It has already been used to treat some cases of depression and has been tested in the recovery of people with neurological disorders, including stroke. In the case of Parkinson’s disease, tDCS has also been used; however, there is still no defined clinical protocol.

“It’s a complex disease and symptoms vary greatly from one individual to another. In addition, postural control isn’t very responsive to medication. In this study, we went beyond investigating whether or not this technique works in postural responses and demonstrated the neuromuscular parameters involved in posture control,” Victor Beretta, coordinator of the Neuroscience and Motor Behavior Laboratory (NEUROCOM-LAB) at São Paulo State University (UNESP), Presidente Prudente campus, told Agência FAPESP.

The research, funded by FAPESP, involved 22 volunteers with Parkinson’s disease. The results indicate that shortly after the eight sessions ended, the protocol improved balance recovery in the face of external disturbances. In assessments conducted one month later, the effects of the treatment were still evident.

In addition to improving balance recovery, the protocol also contributed to what the scientists call “automaticity in postural response control.” This was evident through a reduction in the time it took for the volunteers’ brains to activate the muscles involved in the postural response, as well as a decrease in prefrontal cortex activity.

“Improved automaticity is relevant in the case of Parkinson’s disease, since the neurodegeneration characteristic of the disease alters patients’ ability to perform automatic activities, such as postural responses and walking. This study was important because it highlighted that one month after the end of treatment, the improvement in balance maintenance persisted in these individuals, who are at high risk of falls. Thus, we demonstrated for the first time a possibility for a complementary treatment for postural instability in people with Parkinson’s,” the researcher comments.

Experimental protocol

There is still no cure for Parkinson’s disease, only treatments capable of mitigating the deficiency of dopamine, a neurotransmitter that Parkinson’s neurons fail to produce, whose absence triggers brain changes.

One symptom patients may experience is postural instability, which makes it difficult to maintain balance in certain situations. This instability results from difficulty generating adequate automatic postural reactions due to problems in the interaction between the sensorimotor system and the environment.

Postural control is essential for executing motor skills during daily activities. In everyday situations involving uneven or irregular flooring, for example, some people with Parkinson’s disease do not make sufficient postural adjustments to avoid falling after tripping or slipping.

The research technique consists of modulating neuronal function using a device with two electrodes that generate a low-intensity electric current (two milliamps) that passes through the most superficial region of the brain for 20 minutes. For the volunteers with Parkinson’s disease, the device was applied to the primary motor cortex, an area of the brain associated with postural response and movement control.

“By generating a low-intensity electric current in the brain, we can modulate the readiness of neurons. This stimulation doesn’t generate nerve impulse transmission, but rather modulates the membrane potential to facilitate it,” he explains.

According to Beretta, the goal is to use the electrodes to increase neuronal excitability (and potentially activity) in the motor cortex, which is hypoactive in patients with Parkinson’s disease. “This modulation facilitates neural activity so that, when necessary, the brain triggers what we call action potential [the basic mechanism for communication between neurons and for muscle contraction], increasing the number of neural firings in the cortical and subcortical areas involved in recovering stability and postural balance,” he says.

Before and after the electrical stimulation sessions, the volunteers stood on an unpredictable moving platform, which caused a disturbance to their balance. Consequently, they had to respond posturally to maintain stability. “This made it possible to assess the effect of these eight sessions of non-invasive brain stimulation on the postural response to a disturbance, in a test that simulates these people’s daily lives,” he says.

According to Beretta, neuromuscular and cortical activity changes were observed in the volunteers. “We saw a reduction in the time it took to activate the muscle after the disturbance [faster reaction], which is important for controlling the imbalance caused by the disturbance and preventing possible falls. In addition, we found that these changes were accompanied by decreased activity in a cortical area [prefrontal cortex], which suggests improved movement automaticity,” he says.

The article ”Eight sessions of transcranial electrical stimulation for postural response in people with Parkinson’s disease: A randomized trial” can be read at www.sciencedirect.com/science/article/abs/pii/S0966636224005927?via%3Dihub.