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Neuroscience: Modern Technology & Research (Evidence from Brain…
Neuroscience:
Modern Technology &
Research
Brain Mapping
Attempt to provide a
complete picture about
how the brain works
Relate the brain's
structure to its
function
Find what parts of the
brain give us certain
abilities.
Brain Mapping Techniques
Structural
X-ray Techniques
Cerebral Angiography
Computed Tomography
Computer Axial Tomography
(CAT)
Useful in detecting disorders associated with
abnormalities in brain arteries
Example: hemorrhage (heavy bleeding)
Loss of oxygen in that area
A procedure that uses a special dye
(contrast material) and x-rays to see how
blood flows through the brain.
Injection of a dye into the vertebral artery
or carotid artery in the neck carried to
brain arteries
Paths of arteries surrounding brain tissue
X-rays of skulls then locate malfunctioning
artery – damaged area
Computer Axial Tomography (CAT)
Developed in early 1970s
Less radiation than traditional x-ray.
Computer technology enable
‘deblurring’ of picture &
reconstruction of a complete brain
image from multiple views
Development of CAT enable
process of imaging brain internal
structure to become safer & more
precise– 3D
Advantages
Safer - The fan shaped beam
exposes the body to less
radiation than traditional xrays
More precise - only takes a
cross section of an organ,
avoiding problem of
interference of all the layers
of tissue present in x-ray
images
Clearer image of brain
structures – ‘deblurring’ by
computer technology – 3D
Disadvantage
Doesn’t indicate when an
activity is occurring in the brain
Magnetic Resonance Imaging
(MRI)
Uses a magnetic field to take
images of the inside of your body.
Assumes atoms in the body will
react to magnetic field
Based on radio signals emitted by
the protons in the human body
Advantages
No X-rays or radioactive
material is used (unlike
CAT or PET)
Resolution of the image is
sharper / clearer than
CAT scans
Flexibility – allows the
researcher to distinguish
different structures of the
brain – gray/white matter
and cerebrospinal fluid
Disadvantages
Slow – for an image to be
generated.
An image generated at a given
time will no longer depict a
situation precisely as it was at the
time of the imaging
Cannot be used in patients with
metallic devices, like
pacemakers
May cause claustrophobic
reaction in some patients
Functional
Electrophysiological Techniques
Electroencephalography
Event-Related Potentials (ERPs)
Electroencephalography
A test of the function of the brain itself
records the electrical activity on the brain's
surface.
image the brain while it is performing
cognitive task.
detect the location and magnitude of brain
activity involved in the various types of
cognitive functions
Non-invasive and painless procedure
Take brief patient history
Apply electrode leads to the patient's scalp
Run the test
Advantages
Able to trace rapid changes
in neural activity
Can record activations in
brains of people who are
fully conscious & engaged
in various activities in
natural environment
Disadvantages
Invasiveness – relative
May affect data validity
Possible interference from
movement, heartbeats –
blur reading
Electroencephalograms (EEGs)
Tracings/Recordings of
patterns of electrical
activity in the brain view and record the changes
in brain activity during
performance of cognitive
task
Provide fine
-tuned reading
of rapidly occurring
changes (MRI too slow to
do this)
Event-Related Potential (ERP)
Subject presented with a
stimulus during EEG process
Record voltage change around
the stimulus (before and after
it ends)
Repetitions of event – average
the values
Evoked response provides a
picture of neural activity
changing over time as the
brain processes information
Blood-Flow Techniques
Positron Emission Tomography
(PET)
Single Photon Emission
Computed Tomography (SPECT)
Functional Magnetic Resonance
Imaging (fMRI)
Functional Magnetic Resonance Imaging (fMRI)
Also known as real time or
dynamic MRI – available in
1990s
Decade of the Brain
Detect changes in magnetic
state of blood using MRI
scanners with fast imaging
techniques
Record changes in oxygen
level & blood flow in various
brain locations as subjects
perform various cognitive tasks
FMRI is a technique for determining which parts of the
brain are activated by different types of physical sensation
or activity, such as:
sight
sound
movement of a subject's fingers
mental imagery
calculation
Advantages
Provides information about
brain structure and
function
Safer- Less harm to patients
as no X-rays or radioactive
material is used
Allows researchers to infer
which locations are involved
in specific activities
Positron Emission Tomography (PET scan)
Method of measuring
cerebral blood flow while
subject carries out cognitive
tasks
Uses radioactive isotopes
(i.e. positrons)
PET scans look at bodily
process by detecting the
decay products from
radioactive tracers injected
into the body.
Advantages
Provides an image of brain
activity as a cognitive task is
occurring – locate activity in
specific parts of the brain
Disadvantages
Requires the use of cyclotron,
an expensive equipment to
provide the radioactive isotopes
(decay easily and needs to be
produced each day)
Not as sensitive to changes over
milliseconds (in comparison to
electrophysiological techniques)
not as precise for analyzing
cognitive tasks involving
changes within milliseconds
Radioactive material used
Evidence from Brain Mapping Research
: Insights into Human Cognition
Language
Neural organization of language quite similar for
language learned in ordinary way (i.e. hearing &
speaking) and for signed language acquired by deaf
individuals
Insight from fMRI images on Broca’s & Wernicke’s
Areas confirm hypotheses about involvement of
these areas in human language function
Left hemisphere’s involvement in language is the
same, whether the language is seen or heard
The intact hemisphere can take over tasks of
damaged/removed brain hemisphere
Different parts of brain involved in processing
content (nouns) & function words
Aphasia
(ASL)
Localization
of Brain
Brain
Plasticity
Processing of
Content &
Function Words
Memory
Functions of
Working
Memory
Role of
Hippocampus
Implicit &
Explicit
Memory
Long Term
Memory
Two distinct functions of working memory (i.e. retrieval &
coding) are performed in different locations within the
brain area associated with working memory
working memory NOT generalized; different sorts of
processes carried out in different regions
Investigate role in explicit (i.e. conscious recollection) &
implicit (i.e. unconscious recollection) memory of events
Activation associated more with actual/explicit recollection of
event (i.e. conscious) rather than in effort trying to remember it
Significant role of prefrontal cortex in explicit memory
Greater activation at higher levels of load (higher
memory load lasts longer - continuing activation)
Amount of memory load = amount of information to be
remembered
Concept
Categories
Categorization
Task
Name finding
Disorders
Bipolar &
Unipolar
Disorder
Mood – Bipolar (normal mood alternated with both depression
& mania) & Unipolar (only depression)
Role of neurotransmitter - Missing or deficient
chemical level or substances
Neurochemical and autonomic abnormalities.
Schizophrenia- severe mental disorder (hallucinations
& delusions)
Structural image differences between patient with
childhood onset schizophrenia & adult
Medication has effect in patients’ brain (caudate –
basal ganglia)
Language dysfunction due to deficit in language
processing ability (unable to integrate context –
incoherence)
Autism
developmental brain disorder affecting brain function –
affect social interaction (social & communication deficits)
Greater brain volume found in autistic subjects – possible
causes
Increased production of neurons
Neurons do not die off in great numbers as in
normal development
Increased production of non-neural brain
tissue (e.g. blood vessel)
Dyslexia
Brain-based type of learning disability – affect reading
Unawareness of associations between phonological
segments (sounds) in construction of words
Inability to decode