By Rachel Tierney.
Direct Brain Stimulation
Techniques.
• Direct brain stimulation consists of a
device that delivers a weak electrical
impulse to disrupt neurons in specific
areas of the brain whilst the patient is
fully aware and conscious.
• Two types – Electrode stimulation and
Transcranial Magnetic Stimulation
(TMS).
• Direct brain stimulation techniques
only identify the function of the brain.
Electrode Stimulation.
An electrode is a small fine wire that can be placed onto or
inserted into specific areas of the brain.
• Wilder Penfield’s research in the
1940’s to 1960’s established that
when certain areas of the brain were
stimulated by electric currents a part
of the patient’s body would react. He
then used this information to help
treat epileptic patients.
• http://www.youtube.com/watch?v=kN
dM9JhTPJw
Electrode Stimulation
Advantages.
• Helped create a ‘map’ of the
brain.
• Provided a way for
researchers to identify the
locations and functions of
brain areas, including
hemispheric specialisation.
• Generally very consistent
results
Limitations.
• Extremely invasive.
• Considered unacceptable
with today’s ethical
standards.
• Difficulty in generalising
results as most studies were
done on epileptic patients
with not normally
functioning brains.
Transcranial Magnetic
Stimulation (TMS)
• TMS is a direct brain stimulation technique that involves
directing a magnetic field pulse through the skull and then
disrupts neuron activity in specific areas of the cerebral
cortex.
• Single pulse TMS & Repetitive TMS (rTMS)
• rTMS induces consecutive impulses that cause neurons to
lose their ability to fire.
Transcranial Magnetic
Stimulation (TMS)
Advantages
• Non–invasive.
• Completely safe and
harmless.
• Allows researchers to
conduct research ethically on
human participants.
• Provides information about
function of brain.
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•
•
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Limitations
Can’t be used on patients
with any metal or implanted
medical devices in their
body.
rTMS may induce scalp pain
or mild headaches.
Very rare cases of inducing
seizures.
Only penetrates the part of
the brain directly below the
skull.
Electroencephalograph
(EEG)
• Detects,
amplifies
and
records
electrical
brain
activity.
• Electrodes are
placed on the
scalp(cleaned)
in numerous
positions to
identify the
neuron activity
in different
areas of the
cerebral cortex.
Electroencephalograph
(EEG)
Advantages
• Non-invasive and harmless.
• Extremely cost effective
compared to other methods.
• Provides information about
the function of the brain
even whilst the participant is
doing long tasks.
Limitations
• Only provides general
information.
• Difficult to identify precise
areas of brain activity.
• The skull weakens the
electrical activity.
Structural Neuroimaging
Techniques.
• Structural neuroimaging
techniques can capture
detailed images of the
brain structure and
anatomy.
• Two types –
CT(computerised
tomography) & basic
MRI(magnetic resonance
imaging)
Computerised Tomography
(CT)
• A.K.A – Computerised axial tomography (CAT).
• This technique uses computer technology to take snapshots
of the brain which is separated into ‘slices’.
• An injection of iodine called contrast is injected to highlight
the blood vessels in the brain.
• The patient must lie very still as their head is inserted into
the scanner which rotates to take pictures from different
angles.
http://www.youtube.com/watch?v=M-4o0DxBgZk – Apply this to
the brain instead of the body! 
Computerised Tomography
(CT)
Advantages
• Rarely has side effects and is
non-invasive.
• Shows brain structure.
• Useful to identify location
and size of tumours.
Limitations
• Very expensive procedure
• Does not show functionality
of the brain on the structure.
Magnetic Resonance Imaging
(MRI)
• Is a structural
neuroimaging technique
similar to the CT that
uses magnetic fields and
radio waves to vibrate
atoms in neurons to
project an image of the
brain.
• Colour is used on the
image to identify highly
active neurons which
resemble high brain
activity and vice versa.
Magnetic Resonance Imaging
(MRI)
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•
Advantages
Clearer, more sensitive and
more detailed than a CT.
Non-invasive and harmless.
Almost photographic quality
images.
Does not use radioactive
substances or X-rays.
Limitations
• Only shows structure.
• People with metal implants
in their body cannot use it.
Functional Neuroimaging
Techniques.
• These are techniques that can identify not only
the brain structure like the CT and MRI can
but also they have the ability to show the
functions of the brain ‘at work’.
• Three types – PET(Positron
Emission Tomography),
SPECT(single photon emission
computed tomography) and
fMRI(functional magnetic
resonance imaging).
Positron Emission Tomography
(PET)
• PET uses radioactive
tracer which is either
injected or consumed to
track blood flow through
measuring how much
glucose is being used by
neurons in a particular
part of the brain.
• A computer-generated
image shows the brain ‘at
work’.
Positron Emission Tomography
(PET)
Advantages
• Can clearly show brain
tumours, PET is more
sensitive than CT and MRI.
• Enables researchers to
establish the role of the brain
in behaviour and mental
processes.
• Shows function and
structure.
Limitations
• PET scans are less detailed
than MRI scans.
• Radioactivity decays rapidly.
• Doesn’t always pick up rapid
changes in brain activity due
to 40 second intervals.
http://www.youtube.com/watch?v=5KXIDUo1
8aA 
Single Photon Emission
Computed Tomography (SPECT)
• SPECT is very similar to PET but it uses
a longer lasting radioactive tracer.
• A scanner and computer construct either
two or three dimensional images of the
brain activity.
Single Photon Emission
Computed Tomography (SPECT)
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•
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Advantages
Longer lasting radioactive
tracer can detect brain
activity on longer tasks.
Shows both function and
structure.
Non-invasive.
Significantly less expensive
than PET.
Limitations
• Images are not as good as
PET and have low
resolution.
Functional Magnetic
Resonance Imaging (fMRI)
• fMRI machines use oxygen levels in the blood
of the brain to determine the activity of
certain areas when the brain is ‘at work’.
• fMRI can take rapid pictures of the brain and
therefore capture more brain activity and
changes.
Functional Magnetic
Resonance Imaging (fMRI)
Advantages
• Does not require radioactive
substances.
• Colour coding and detailed
images make it relatively
easy to read.
Limitations
• Levels of activity may not be
related to the tasks that they
are asked to complete.
• Costly.