Transcript Physiology and behavior: Localization of function

Physiology and behavior:
Localization of Brain Function
Learning Objectives
•
Discuss the use of brain imaging technologies in investigating the relationship
between biological factors and behavior (SAQ)
•
Explain how one study related to localization of function in the brain (SAQ)
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Examine one interaction between cognition and physiology in terms of behavior.
(ICE)
•
Evaluate two relevant studies (ICE)
•
Discuss two effects of the environment on physiological processes. (SAQ)
Part 1: Brain Imaging
What you need to know about brain imaging?
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What they are used for?
Strengths
Limitations
Research examples that use technology to
demonstrate your point (support the study of brain
localization)
Early investigations…
• Phrenology
– 18th-19th century
• Assumptions
– Good  certain parts of the
brain related to personality and
behavior
– No so good  you can tell by the
bumps and depressions on the
brain
Case studies & Naturally Occurring
Brain Damage
• Until the late 20th century, most brain
research was limited to case studies
– Not experimental
• No clear cause and effect
– Unethical to ask for volunteers
• Two research examples:
– Broca & Wernicke
• Participants developed aphasia
Broca & Wernicke
• Method: Case Study
• AIM: to study the brain (post-mortem) to connect
the language disorder with a specific region in
the brain
• Procedure:
– Step 1: study behavior before death
– Step 2: autopsy the brain and pin point a specific
region associated with the behavior
• Implications:
– Broca’s Aphasia: unable to produce language
• Left Frontal Lobe
– Wernicke’s Aphasia: unable to comprehend speech
• Left Temporal Lobe
Modern Technology
• What do you need to know?
– What do we use the scan for?
– Strengths/limitations
– Research support
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Electroencephalograph (EEG)
Computed Tomography (CT)
Magnetic Resonance imaging (MRI)
Functional MRI (fMRI)
Positron Emission Tomography (PET)
EEG
• What do we use the scan for?
– Best known for sleep research
• Brain waves change during sleep
• Strengths/limitations
– Strengths: clearly distinct patterns for brain waves
– Limitations: not accurate enough for most localization
of function research
• Why? Electrodes outside the brain
• Research support
– Connolly 2000
Connolly (2000)
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Method: Case Study
AIM: to determine the extent of cognitive loss
Procedure: use EEG to measure awareness
Results: individual actually had awareness and
extensive rehabilitation enhanced his recovery
• Implications: awareness changes brain activity
REM: Dreams
CT
• What do we use the scan for?
– Allows us to see soft tissue of the brain
• Structure changes to do to damage or tumor
• Strengths/limitations
– Strengths: Great at see structural changes
• Brain tumor/damage
– Limitations: does not show brain activity
• Research support
– Ogden (2005)
Stroke
Ogden (2005)
• Method: Case Study
• AIM: study the impact of a brain tumor on
hemineglect
– Hemineglect: brain damage causes inattention to the
opposite side of space
• Procedure
– Neurological assessments:
• Scan the brain (CT)
• Draw pictures, read
• Implications
– Patients are aware of the neglect (jokes, justifications) but
a willing neglect by half the brain
Tumor
MRI
• What do we use the scan for?
– Damage to really specific parts
• Strengths/limitations
– Strengths: three dimensional pictures
• Allows us to see more structure
– Limitations:
• Safety (metal?) but it is limited on x-ray radiation
• Does not show activity
fMRI
• What do we use the scan for?
– Shows brain activity in specific area
– Used for a wide-range of behavior
• Strengths/limitations
– Strengths
• Studies the brain as activity occurs
• Wide range of behaviors
– Limitations: correlational
• not a natural environment (ecological validity)
• Colors may exaggerate activities
• Changes may occur for many reasons
• Research support
– Brefcynski-Lewis etal (2007)
Brefcynski-Lewis et al (2007)
• Method: Quasi-Experiment
• AIM: study examine differences in brain activity
resulting from meditation over a long period
• Procedure
– 10,000-54,000 hours of meditation (Asian)
– Newly trained (Caucasian)
– * used fMRI to measure attention during meditation by
distracting individuals with background noise
• Results
– Experienced  adjusted concentration (active
resistance to not being disturbed
• Implications: Meditation changes the brain
(plasticity)
Evaluation of
Brefcynski-Lewis etal (2007)
• Is this a true experiment?
• How else could you describe the study?
• Are the conclusions valid?
• Reference page 46-47
PET
• What do we use the scan for?
– Abnormalities in activity level
• Alzheimer’s
• Strengths/limitations
– Strengths: activity
– Limitations: limited on specific region
• Use tomography
• Health problems limit availability
The Brain and Behavior
**Warning…intense picture
Use the Blue Textbook
• Write down the function of each brain part
– Page 64-70
Neurons
• What do they do?
– Networks produce intelligence and
consciousness
• Single neuron is not very smart
• Neurons link together to send
messages
– Necessary for even a small thought
• No TWO neurons are exact
Neurons
• Neurons are composed of:
– Cell body (soma): directs actions of the cell
– Dendrites: extensions that receive information
– Axon: extends from cell body, carries electrical
potential, sends a chemical message to adjacent
neurons via terminal buttons
Brain Function and Ethics
• Non-Invasive
– Researcher does not invade the body to
conduct research
• Brain Scans
• Experiments
• Invasive
– Researcher invades the body to conduct
research
• Brain Surgery, Autopsy
• Ablation, deep lesioning
• Invasive:
– Lesioned
hypothalamus
– Results  doubled
weight
• Ethics: damage
cannot be reversed &
does it cause pain?
Animals and
invasive research
Gazzaniga, 1967
• Localization of Brain Function
– Corpus Callosum
Video: Gazzaniga
• http://www.youtube.com/watch
?v=82tlVcq6E7A
• TWO Researches
• Method
• AIM/Hypothesis
• Procedure
• Results
• Implications (how does this
relate to localization of brain
function)
– Note…its not the hemispheres
Case Study of HM
• Why is it important?
– Showed us that there are different memory systems in
the brain.
• Original study
Milner (1957)
– Age 7  head injury from falling
– 20 years of seizures  increasingly incapacitated
– Age 27  removed brain parts to stop seizures
• Behavior impact:
– Could not create NEW memory (Amnesia)
» Semantic: factual memory
» Episodic: personal memory
» Personality was unchanged
Limbic System
• Corkin et al (1997)
– MRI Scan
– Parts missing
• Pieces of temporal lobe (hearing and language)
• Limbic System
– Hippocampus (memory)
– Amygdala (emotion and fear)
– Damage wasn’t as severe as Milner thought
What did we
learn about localization
(HM)?
• Hippocampus
– Important for converting memories
• from short term to long term storage
– temporary vs. permanent storage
• retained memory before surgery
– could learn a few procedural memories
• Not stored by the hippocampus
• Specific memory loss  specific brain
region
– The brain has several memory stores
Evaluation of HM Case Study
• Operation was based on the assumption
that the seizures would stop
– Damage may have already been done
• Strength  Longitudinal
– 50 years of a wide range of tests
• Cognitive, observations, neuroimaging
• Ethics
– Is it unethical if he cannot remember all the
times he participated in research?
• Justification: findings are very important
• Guardian gave consent
• Limitations
– Case Study
• Findings from one research do not represent the
whole population
• But…Supported by years of follow-up research
Mozart Effect
Rauscher at al. 1993
• Hypothesis: listening to Mozart
will temporarily increase spatial
reasoning ability
– Why? Complex musical productions
excite neurons needed to solve
complex spatial tasks
Thompson et al. 2001
• Experiment
• Hypothesis: when people do something
they enjoy (elevated mood), they have
improved spatial skills
• Results: Increase in spatial skills
• Implications: improvement is not based on
plasticity but on increased attention
• Limitation: Ecological validity
Using the Amnesia
reading…answer the following
questions?
1. What is the difference between anterograde
and retrograde amnesia?
2. What is the difference between declarative and
nondeclarative memories?
– Connect to HM
3. What specific brain locations are associated
with anterograde amnesia?
4. Break down ONE research discussed in
reading
– Who, when, method, aim, results, implications
How does the environment
impact the brain?
Topics
•Brain Plasticity
•Psychological trauma & PTSD
SAQ:
•Discuss two effects of the environment on physiological processes
Assumption
• Brain changes behavior, behavior changes the
brain
– especially cerebral cortex
• Higher functioning
• Brain plasticity
– Changes that occur as a result of learning or
experience
– Rearranging the connections between neurons
– Adaptation to the environment
Dendritic
Branching
• Learn something new  change
in neuron connection
– Dendritic branching
• Example:
– Musician has a thicker area of the
cortex related to music
• Research support:
– Rosenzweig, 1972
– Limitation: unknown impact on
behavior
• Assumed because of an increased
neuron density
Rosenzweig & Human Behavior
• Psychologists cannot carry out controlled
experiments to test humans
• Humans differ
– Genetic make-up
– Environmental inputs
• Importance of education in the growth of
new neuron connections (synapse)
• Brefcynski-Lewis et al, 2007
– Meditating monks
Environment, Brain Function
and Behavior
Neurology/physiology of PTSD
Environment and the Brain
• Meditating monks  different levels of brain
functioning
• MA Case Study  Different areas of the
brain can take over language
• Taxi drivers  use hippocampus to store
more visual memory
• Limitations and strengths
– How clearly can we use cause and effect?
– How clearly do we understand the interaction
between cognition and physiology?
What is PTSD?
• Mental Disorder: Post-Traumatic Stress Disorder
• Behaviors
– traumatic memories that seem different from other
kinds of memories.
• continue for many decades
• easily triggered
– Memory in PTSD patients is also characterized by
impairment
• not being able to remember aspects of the trauma
• fragmentation of memories
• dysfunction in the amygdala and hippocampus
– "emotional memory system" of the brain.
Physiology of PTSD
• Role of hippocampus
– Connects and organizes memories
– PTSD  Decrease in size
• Stanford University (2009)
– children with PTSD
– (MRI)
– PTSD symptoms  poorly functioning
hippocampus.
• Yale University (1995)
– Vietnam Veterans with memory problems
– 8 percent reduction in the size of the right
hippocampus
• other portions of the brain retained their size.
Rauch et al., 1998
• Method: Case Study
• Hypothesis: Amygdala and Hippocampus are
impacted by PTSD
• Procedure: PET and MRI studies
• Results
– Veterans with PTSD demonstrate increased right
amygdala activity when exposed to combat
movies.
– Both male combat veterans and women survivors
of childhood sexual abuse with PTSD have lower
hippocampal volumes.
• Implications
– Decreased volume of the hippocampus correlated
with trauma exposure or memory deficits.
• How do we know PTSD caused a
shrinking of the hippocampus?
– Prolonged exposure to trauma shrinks the
hippocampus
• OR
– A smaller hippocampus makes you more
vulnerable to PTSD
Harvard Medical School, 2002
• Method: Case Study
• AIM: relationship between hippocampi and PTSD
• Procedure
– MRI bran imaging
– pairs of identical twins
• one twin served in Vietnam and the other did not
• Results:
– The veterans with PTSD  smaller hippocampi
– Brothers of the veterans with PTSD  smaller than
average hippocampi.
• Implications
– Smaller than average hippocampus is not the result of
PTSD, but a risk factor for developing it.
• Quiz Thursday: Behavior and physiology
(Localization of Brain Function)
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Brian imaging
Localization of brain parts
Basic neuron parts
Physiology and behavior (types of memory) of
amnesia
– Environment and brain changes: Plasticity and PTSD