INNOVATIONS FROM THE EDGE - KPIT

on the methods of coding of output information,
which is transmitted out from the brain to the
body organs through the motor neurons and
inter-neurons.
III. Types of Brain Machine Interface
captured, decoded and transmitted to the robot
arm controller. The final robot arm movement is
also visible to the monkey. Scientists at Duke
University are carrying out this experiment [3]. The
figure 4 shows an experimental setup of BMI for
Robot control at Duke University.
Depending upon the placement of electrodes for
picking the neural signals, there are three types of
Brain Machine Interface that are currently under
development.
Invasive Brain Machine Interface
In this type of BMI, the electrodes are implanted
deep inside the brain during neurosurgery. This
type of placement produces the highest quality of
neural signals. However, this also has the
drawback of electrodes being damaged by the
reaction of brain tissue to foreign material
(electrode material). The figure 3 shows the
placement of electrode in Invasive BMI type.
Figure 4: Experimental Setup of BMI at
Duke's University (Reference [3])
The development areas for this type of BMI include
the development of implantable electrodes and the
development of signal processing techniques for
decoding neural signals picked by the implanted
electrodes.
Partially Invasive Brain Machine Interface
In this type of BMI, the electrodes are implanted
below the skull and outside the brain. The electrode
array is spread out on the brain surface instead of
penetrating inside the brain. The advantage of this
type of BMI is that it eliminates the possibility of the
electrode damage by the brain tissues. As the
electrode stays beneath the skull, the signal damping
due to the skull is reduced. However, this creates a
permanent hole on the skull. Electrocorticography
(ECoG) methods are utilized for the partially invasive
BMI implementations [4].
Figure 3: Invasive BMI Electrode Placement
This method of BMI is widely experimented on
animals like rats and monkeys. A number of
experiments are carried out for controlling a robot
arm by thoughts. In these experiments, the
electrodes are implanted in a monkey's brain and
the monkey is trained to move a joystick. The
signals from the monkey's brain, which are
generated during the joystick movement, are
Non-Invasive Brain Machine Interface
In this type of BMI, the electrodes are placed on the
s ku l l a t c e r ta i n d e f i n e d p o s i t i o n s . T h e
Electroencephalography (EEG) measurements
methods are widely used in non-invasive BMIs. There
a r e o t h e r n o n - i n v a s i v e m e t h o d s l i k e
Electromyography (EMG), Functional Magnetic
Resonance Imaging (fMRI), etc. which are also used in
the non-invasive BMIs.
In methods utilizing EEG, the signals (neural signals)
14 TechTalk@KPITCummins, Volume 5, Issue 1, 2012