In the last few decades, there has been a push towards restoring sensory perception to upper-limb amputees. This sensory perception ranges from gentle to noxious (harmful) stimuli. These are indispensable elements for bodily protection as well as rebuilding the sense of embodiment in amputees.
A study in 2019 used EEG recordings to identify and validate a spatio-temporal signature of brain activity during innocuous, intense and noxious stimulation of an amputee’s phantom limb using transcutaneous nerve stimulation (TENS). The spatio-temporal EEG features were then used to develop a system for detecting pain perception and reaction in the brain. The study managed to localise brain activity to the sensory stimuli in different conditions. Their findings suggested that noxious sensory stimulation actives the anterior cingulate cortex and the posterior cingulate cortex. Whereas, the parietal lobe was activated by moderately intense stimulation. The parietal lobe also plays an important role in pain perception and understanding. These findings were a first attempt to classify neural activity when restoring sensory perception to amputees. This is a novel approach towards designing a real time pain reaction system in upper-limb prostheses.
Based on the identified spatio-temporal brain activity patterns, an offline system for the detection of pain was developed. The system is able to recognise the three distinct stimulation conditions from the recorded EEG responses by using effective spatio-temporal bio-markers to identify the different brain regions involved in noxious stimuli processing. The overall goal of the study was to extend upon the Osborn study in which a reflex system was implemented in the arm prosthesis and the amputee was not involved in the withdrawing reaction. This is thought to be crucial when designing a bidirectional-control system between the human and the prosthesis; hence it increases the amputee’s sense of embodiment and the sense of ownership. Furthermore, the detection of perceived pain sensation and reaction will have an important role in protecting the prosthesis from external damage.
Unlike fMRI or intracranial signals, the EEG allows for a continuous and real-time recording; which could be used when developing real-time systems based on neural response to sensory stimulation. The study suggests that a withdrawal/pain reaction system could be implemented by harnessing the neural response to painful stimuli. The withdrawal reaction could be activated when the prosthesis touches sharp objects- protecting it from damage. Along the same lines, this can help better monitor the user’s perception of what is happening to create more natural protheses and provide the amputee more intuitive control over their prosthesis as well as increase the sense of embodiment and ownership. This is a ground-breaking neuroscientific approach to designing functional prosthetics that behave as a normal limb would.
- Sham
My poem of the week:
The awakening
In the early dawn of happiness
You gave me 3 kisses
So that I would wake up
To this moment of love
I tried to remember in my heart
what I dreamt about
during the night
before I became aware
of this morning
of life
I found my dreams
but the moon took me away.
it lifted me up to the firmament
and suspended me there.
I saw how my heart had fallen
on your path
singing a song.
Rumi
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