Neural Interfaces and Prostheses
György Karmos, Balázs
Dombóvári, István Ulbert, Bálint
Péter Kerekes
Pázmány Péter Catholic University
Faculty of Information Technology
Budapest, Hungary
[karmos,dombovari]@itk.ppke.hu,
ulbert@cogpsyphy.hu,
kerekes.balint.peter@gmail.com
Richárd Csercsa, Richárd
Fiáth
Institute for Psychology
Hungarian Academy of Sciences
Budapest, Hungary
[csercsa,fiath]@cogpsyphy.hu
Ákos Kusnyerik
Semmelweis University
Dept. of Ophthalmology
Budapest, Hungary
kusnyeri@szem1.sote.hu
The course makes the students familiar
with the new developments of neural engi-
neering in the field of neuroprosthetic devices
that can substitute motor, sensory or cognitive
functions that might have been damaged as a
result of an injury or a disease. These devices
make direct interfaces with the peripheral and
central nervous system. Some of these devices
are already routinely used in the clinical prac-
tice like the cochlear prostheses for restoring
hearing others are still in the developmental or
experimental phase. Neural interface is a con-
nection between the living tissue and a man-
made device, in most case a bioelectrode.
Neuroprosthetic research is integrating differ-
ent fields of medical and engineering disci-
plines. New discoveries in this field are al-
ways the result of close collaboration of ex-
perts in most different areas of research. In the
course we intend to give a survey of divergent
areas of neuroprosthetics.
In the first lectures of the course the basics
of bioelectrical processes of nerve cells are
summarized and the effects of electrical stim-
ulation in the excitable tissues are discussed.
The electrical stimulation to activate peripher-
al nerves innervating muscles affected by pa-
ralysis is called functional electrical stimula-
tion (FES). In a lecture the clinical applica-
tions of FES combined by different forms of
orthoses are discussed. In the last decade
spectacular development was made in the neu-
ral control of limb prostheses. The nerve rein-
nervation technique resulted in the develop-
ment of the “bionic arm” that is controlled by
the intentions of the patient through myoelec-
tric signals.
Navigation methods like stereotaxic tech-
nique and frameless neuronavigation made
possible minimal invasive neurosurgery. Neu-
ronavigation is based on fusion of CT, MR,
and angio images by a neurosurgical planning
software. The planning software can precisely
locate the size, shape and location of the brain
tumor, lesion or abnormality. Modern “blood-
less neurosurgery” by “Gamma knife” does
not require the skull to be opened for perfor-
mance of the operation. Studies demonstrate
savings of more than 50% of direct costs as-
sociated with microsurgery.
Stereotaxic implantation of electrodes in
humans made possible the chronic deep brain
stimulation (DBS) in movement disorders.
The target area is also localized by recording
of the neural activity along the electrode track.
DBS is a neurosurgical treatment involving
the implantation of a battery-powered neu-
rostimulator which sends electrical impulses
to the target area of the brain through the im-
planted electrode. The neurostimulator is usu-
ally implanted under the skin of the chest and
wires go under the skin to the electrodes. The
patient can program the neurostimulator by
radiofrequency way. In the lecture the Parkin-
son’s disease is used as an example since
DBS is most widely and most successfully
used in patients suffering in medication re-
sistant Parkinson’s disease. DBS is not a cure
but suppresses the motor symptoms and high-
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ly improve the quality of life of the patients.
In the last decade DBS also became generally
accepted as treatment in dystonia, essential
tremor, Tourette's syndrome, obsessive–
compulsive disorder and depression. The
physiological mechanisms of the DBS are still
not clear. The different hypotheses are dis-
cussed. The most accepted view is that DBS
has a suppressing effect on the pathological
rhythm of the target area neuronal networks.
A special noninvasive form of brain stimu-
lation is the transcranial magnetic stimulation
(TMS). TMS apparatus generate rapidly
changing magnetic field in a coil held close to
the head. The weak electric currents induced
by this magnetic field change causes excita-
tion or inhibition in the neurons of the stimu-
lated area of the brain. TMS causes minimal
discomfort, allowing the functioning and in-
terconnections of the brain to be studied. The
TMS lecture deals with the principles and
techniques of TMS and examples of possible
clinical applications are mentioned.
Sensory prostheses are the subjects of three
lectures. Two of them deal with the hearing
aids. After a short introduction of the biology
of hearing, the possibilities and types of audi-
tory prostheses will be detailed, focusing
mainly on cochlear implants, but we will
show other solutions too, ranging from the
middle ear implantable hearing devices to
methods in experimental stage like the audito-
ry brainstem implants and auditory midbrain
implants. The subjects of the third lecture are
the visual prostheses. The retinal implants are
discussed in more detail but other solutions
like stimulation of the optic nerve and the
visual cortex are also mentioned.
There are diseases or pathological states
when the muscle system of the patients is to-
tally paralyzed and they are unable keep con-
tact with their environment. A special group
of neuroprosthetic devices, the “brain com-
puter interfaces” (BCIs) give promise for the-
se patients. These devices translate the brain
electrical signals for communication with the
external world as well as for manipulation of
technical devices such prostheses and micro-
processors. We devoted three lectures to this
topic giving detailed survey of both noninva-
sive and invasive BCIs. The present day BCI
systems are in experimental phase but some
noninvasive BCIs are already commercially
available. A new area of BCI application is
the games and virtual reality. BCI research
became very popular in the recent years, new
applications will emerge and the BCI systems
will become part of our everyday life.
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