Download Why study brain-behavior relations?

What is Neuropsychology
Study of brain–behavior relations (sometimes
referred to as functional localization)
Functional Lateralization – refers to notion that
a function may depend on one side
(hemisphere) of the brain
Definition of Clinical Neuropsychologist
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A clinical neuropsychologist is a professional
psychologist who applies principles of assessment
and intervention based upon the scientific study of
human behavior as it relates to normal and
abnormal functioning of the central nervous system.
The clinical neuropsychologist is a doctoral-level
psychology provider of diagnostic and intervention
services who has demonstrated competence in the
application of such principles for human welfare
following:
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A doctoral degree in psychology from an accredited
university training program.
An internship, or its equivalent, in a clinically relevant area
of professional psychology.
The equivalent of two (fulltime) years of experience and
specialized training, at least one of which is at the postdoctoral level, in the study and practice of clinical
neuropsychology and related neurosciences. These two
years include supervision by a clinical neuropsychologist .
A license in his or her state or province to practice
psychology and/or clinical neuropsychology independently,
or is employed as a neuropsychologist by an exempt
agency.
Different types of
Neuropsychologists/ Subareas
􀁺 Experimental neuropsychologists – work to understand
the neural bases of cognition by doing studies
– Experimental neuropsychology = cognitive
neuropsychology or cognitive neuroscience
􀁺 Clinical neuropsychologists – work in health-related
settings (e.g., hospitals, clinics) with patients
– Involved in diagnosis
– Involved in rehabilitation (e.g., designing programs)
– May be involved in research
– Clinical neuropsychology
How do we study brain-behavior
relations? (Techniques)
Invasive
– Lesion
– Inject radioactive tracer
Non-invasive
– Brain-imaging to see what regions are active during
specific mental task
– Record activity of cells to determine what activity makes
them respond
– Present information to different hemispheres and see
which side does task better or faster
Why study brain-behavior
relations?
􀁺 Diagnostic purposes
􀁺 Rehabilitation purposes
􀁺 Intellectual curiosity
Methods in
Neuropsychology
Method of converging operations:
Use a number of different methods and
populations
􀁺 Evidence obtained from a set of
experiments converge on the same
conclusion
– e.g., fMRI and lesion studies
Research considerations:
􀁺 What type of participants?
􀁺 How will we gather information about
their brains?
􀁺 How will be measure behavior?
Research Participants:
􀁺 (1) Patients with lesions
􀁺 (2) Healthy Individuals
􀁺 (3) Animals
(1) Patients with lesions
􀁺 Question: What functions supported by this
neural site?
􀁺 Studies need to include patients with lesions
to a specific site and patients with lesions to a
different site
􀁺 ‘Double dissociation’ - lesions have converse
effects on two distinct cognitive functions
􀁺 Allow one to conclude that structures/
functions are independent
􀁺 Question: What neural sites are
associated with a particular deficit?
– e.g., Memory impairment associated with
damage to:
– Brenda Milner’s work with temporal lobe
epilepsy and memory where
hippocampus was found to be
important for learning
Problems with lesion method
􀁺 Brain damage messy in humans
(1) People vary in their genetic and
environmental characteristics
• e.g., differ in education, onset of dementia
– Lesions vary in their extent and origin
• Stroke vs tumor vs bullet
(2) Lesion does not allow us to observe directly the function
served by the lesioned site
􀁺 Only know how brain performs without
that particular area
􀁺 We can infer the site may be critical but we can not identify
all the areas that may be involved
􀁺 Site may not be critical in performing a particular function:
rather, may contain axons that connect regions that
must interact for correct performance
– Disconnection syndrome
• Split brain
• Conduction aphasia
Associated problem:
single cases or groups
􀁺 Groups of patients may be so hetergeneous in their
behavior that ‘group average’ is meaningless
– Argues for single case approach
􀁺 Problem with single case approach
– Is pattern observed representative of people in
general?
– Does not allow one to rule out random error
􀁺 Use multiple case approach, validating
research findings on a series of patients, or
􀁺 Follow-up findings from single-case with
group studies
(2) Neurologically intact
Individuals
􀁺 These persons provide the control group that allows us to
determine thedegree to which performance of brain
damaged people is compromised
􀁺 Well-designed studies must include appropriate control
group
(3) Animal Populations
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􀁺 Allows for control over
– Environmental conditions/experience
– Size and nature of lesions
– Genetic differences, etc.
Gathering Information about
the Brain:Techniques
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􀁺 CT Scans
– Uses series of X-ray beams through head.
Images developed
on sensitive film. Shows anatomical image
of brain density.
– CSF < brain tissue < blood < bone
– Darker < …………………….> Lighter
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􀁺 Advantage:
– Can be used with most people
􀁺 Disadvantage:
– Uses radiation
– Dye may cause allergic reaction
– Results do not have a high spatial
resolution
– Structure of brain only
MRI
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􀁺 Anatomical image of substances such as water or
fat give picture of tissue density
􀁺 Relies on passing an external radio frequency
pulse to disrupt the magnetic fields of nuclei
and distort the behaviors of atoms
􀁺 When atoms fall back in line, they re-emit the
radio-frequency signal which is detected by a
receiver coil
􀁺 The frequency of this signal reflects the
number of elements in the nucleus and the
effect of the surrounding material
Advantages
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􀁺 Does not require X-rays or radioactive
material
􀁺 Safe, painless, non-invasive
􀁺 Result is high resolution
Disadvantages
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􀁺 Expensive
􀁺 Cannot be used in patients with metallic
devices, like clips, pacemakers, or
possibly orthopedic pins
􀁺 Cannot be used with claustraphobic
patients
􀁺 Assesses structure only
Functional MRI
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􀁺 In fMRI, MR signal measures functional
characteristics of brain
􀁺 Detects changes in blood flow to
particular areas of the brain
􀁺 Provides both an anatomical and
functional view of the brain
Advantages
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􀁺 Noninvasive - radiation needed
􀁺 Multiple scans can be done on an
individual so can examine changes
over time (e.g., learning)
– Provides a good measure of
brain activity over seconds
􀁺 Provides a good spatial resolution
Disadvantages
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Cannot localize processes in time better
than 1 second
– fMRI does not image neural activity but
rather response of vascular system to
oxygen demand and this can lag
functional
activation as well as extend beyond period
when activation
occurred
PET
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Also provides a functional image of brain
activity
􀁺 Radioactive substance (e.g., glucose)
introduced into blood
􀁺 Radioactive molecule becomes stable by
releasing positron, collides with electron,
annihilate each other -producing energy PET detects this energy
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􀁺 PET detects how much of the brain fuel
(oxygen, glucose) is being used by different
regions
􀁺 Areas that are metabolically active emit
lots of energy; those that are less active
emit less energy
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􀁺 Advantages
Good at examining functioning of a variety of
neurotransmitters
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􀁺 Disadvantages
Involves radiation
Provides image of brain activity averaged over very
long time periods (e.g., minutes whereas cognitive
decisions occur in msec)
Typically, data on task is averaged across many
people
Not very good at determining location of function in a
given person (does not provide high spatial
resolution)
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EEG
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􀁺 Electrical activity of the brain
􀁺 Provides information about general
state of person (e.g., awake)
􀁺 Good at detecting various clinical
disorders
– e.g., sleep, seizures
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􀁺 Provides accurate measures of activity
on a millisecond basis
􀁺 But poor at localizing activity
􀁺 Does not provide information about
subcortical structures
Event Related Potentials
(ERP)
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􀁺 Recording of brain’s activity that are linked to
the occurrence of an event (stimulus)
􀁺 Provides information linked to processes
such as memory and attention
􀁺 Examine components of the waveform
recorded on the scalp such as
– P300 - S must respond to target stimulus (‘b’
not ‘d’, blank sound) - appears to measure
attention, updating of memory
Neuropsychological
Assessment
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􀁺 Allows one to separate cognitive functions
(e.g., STM vs LTM)
􀁺 Profile patient strengths and weaknesses
– diagnosis
􀁺 Provide a baseline to evaluate change
– e.g., remediation, improvement, decline
􀁺 Make statements about prognosis
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􀁺 Fixed batteries
(e.g., Haltead-Reitan, Luria-Nebraska)
􀁺 Flexible battery
􀁺 Generally measure IQ (Wechsler tests)
􀁺 Also measure executive function,
attention, memory, language, spatial
ability, motor, sensory function,
emotional function
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􀁺 Need good normative data
􀁺 Pre-morbid Estimation
e.g., NART, WTAR