Even
patients who gain movement and recover after stroke find it difficult to
perform goal directed and well-coordinated and smooth movements making tasks
like writing or holding and manipulating objects a challenge, which impacts
daily living both at home and in the work place.
Over
the past two
decades, neuroscientists have demonstrated that coordinated patterns of brain
cell activity known as oscillations are critical to efficient brain function.
More
have been shown to play a key role in regulating the firing
of neuronsin the brain's primary
motor cortex. The motor cortex controls voluntary movement, and
to ensure smooth, seamless and well-coordinated movements.
The
authors of the study believe that recovery of movement in patients following
would be better and quicker by using
brain stimulation compared to current standard of care
‘Stroke results in loss of low-frequency oscillations (LFOs) in the brain that leads to impaired movement. However, restoration of LFOS can improve movement and hasten recovery.’
"Our
main impetus was to understand how we can develop implantable neurotechnology
to help stroke patients," said Ganguly, who conducts research at the San
Francisco VA Health Care System. "There's an enormous field growing around
the idea of neural implants that can help neural circuits recover and improve function.
We were interested in trying to understand the circuit properties of an injured
brain relative to a healthy brain and to use this information to tailor neural
implants to improve motor function after stroke."
Details of Study
In
order to gain further insight into the possibility of LFOs in stroke recovery, the
scientists studied a rat model of stroke and analyzed its movements while trying to
reach for a food pellet, in essence simulating goal directed movement in humans
- They induced a stroke in the rats that affected the animals' movement
ability, and found that LFO
activity in the brain cells was reduced
- The
LFOs activity were also restored in rats that
recovered. Faster and more precise movements
were seen.
- There was a significant correlation between the restoration of LFOs and recovery of
movement. Animals that recovered fully had better
low-frequency activity than those that recovered only partially, and no
LFOs were seen in the animals that did not recover
- To try and aid recovery, the team
used electrodes to both record electrical activity as well as administer a
mild electrical current to the rats' brains, exciting the area immediately
adjacent to the part damaged by stroke
- This stimulation consistently
increased LFOs in the damaged area and seemed to aid in the
recovery of motor function; interestingly, when a burst of electricity was
delivered just before a rat attempted to make a movement, the animal was
nearly 60 percent on target in reaching for the food pellet than if no
current was delivered
"Interestingly,
we observed this augmentation of LFOs only on the trials where stimulation was
applied," said Tanuj Gulati, PhD, a postdoctoral researcher in the Ganguly
lab who is co-first author of the study, along with Dhakshin Ramanathan, MD,
PhD, now assistant professor of psychiatry at UC San Diego, and Ling Guo, a
neuroscience graduate student at UCSF.
Thus
the findings of the study suggest that
administering mild electrical
stimulation to brain restores LFO activity which is impaired during a stroke.
The restoration of LFO activity aids in quicker recovery. By delivering
current, the existing weak and ineffective LFOs become amplified and are able
to bring together the cells of the motor cortex of the brain to function
together to produce precise goal directed movement.
Measuring LFOs In Human
Stroke Patients
The
team further tested whether the findings in rat models might also apply to
humans. To this end, they analyzed tracings made from the surface of the brain
from a seizure patient who had suffered a stroke, impairing his mobility. The
recordings demonstrated significantly lesser number of LFOs than recordings
from two epilepsy patients who did not suffer a stroke.
Scope of Study
Currently
physiotherapy is the standard of care in stroke patients to hasten their
recovery, but unfortunately not in those whose
stroke damage is too extensive. Ganguly hopes that electrical
brain
stimulation could be
a useful alternative in these patients to make the existing neurons become
more functional. In fact,
brain stimulation is being widely used in patients with epilepsy and
Parkinson's disease and stroke patients can also benefit from this option.
The
study team hopes
that their findings could be used to improve stroke recovery in human patients
as well. The details of the study appear in the journal
Nature Medicine.
References :- Allen Cone., "Brain stimulation restores movement in rats after stroke" Nature Medicine (2018)
- Dennis Thompson, HealthDay Reporter., "New Electrical Stimulation Therapy Can Help Stroke Patients Move Paralyzed Hand" HealthDay (2016)
Source: Medindia
