Download History and Methods

Cogsci 172
Brain Disorders and Cognition
Professor Ayse P. SAYGIN
TA: Mike Metke
[email protected]
Course URL: TBA
Brain Disorders and Cognitive Science
Upper division cognitive neuroscience class
Not a clinical class – not focused on treatment
Main goal is trying to understand how the brain
works
It may seem counterintuitive to study the
disordered system to do that…
Brain Disorders and Cognitive Science
A lot of what we know about the brain has been
revealed by the study of patients with brain
disorders
The study of brain disorders remains a powerful
source of information in cognitive neuroscience
Perception, action, cognition are easy
to take for granted
However…
More often than not, brain disorders do not
present themselves neatly packaged
Identifying behavior to brain relationships is
difficult in practice.
The need for multidisciplinary, multimethodology investigation of the research
questions.
A “Sampler”
Unfortunately, there are many disorders that
affect cognition
This course can only sample some of them
Focal brain lesions and their effects
More diffuse or neuromodulator-based disorders
We will cover visual agnosia, aphasia, apraxia, schizophrenia,
chronic pain, autism spectrum conditions and more…
You can pick a disorder not covered in class for your paper
How do work with disorders inform fundamental
questions in cognitive science?
About the Class
• Upper division
• Elective
My Goals and Expectations
– Some “textbook” style knowledge
– But most issues don’t have straightforward answers
– Important to learn how to think and inquire about the
brain and its disorders
– CRITICAL THINKING, RESEARCH and WRITING
Advice
– Lectures are key. There is no textbook and assigned
readings are supplements to the lecture, not substitutes
– Sections will go over the lectures and answer any
remaining questions
– No laptop or phone use in class. See syllabus as well.
– Do not miss exams/deadlines. There are no make-ups.
– Exams will have some “knowledge” questions, and some
that are more open-ended (even with no “right” answers)
– Work on your term paper throughout the quarter (you will
have interim deadlines)
– Participate in the lecture. Don’t be afraid. ASK QUESTIONS!
Academic Integrity
– There is absolutely zero tolerance for cheating and
plagiarism in this course. The syllabus contains important
information on course and university policies. READ IT.
– You must write in your own words. That means no
wikipedia or web text. No copy and pasting, period. None.
– It is your responsibility to understand and follow writing
and citation practices appropriate for this class. I will
lecture more on this later.
– If you are unsure how to cite/refer to something, do not
make assumptions – ask!
More on Plagiarism
– I personally read and grade every term paper.
– Every paper is checked for plagiarism with multiple
software packages.
– What happens if we find plagiarism:
• Academic sanction: You will get an F for that entire assessment
• Administrative sanction: I am required to report incidents to the
Academic Integrity office. The sanctions are decided depending
on the severity of the incident. Please understand, I have no
control over this process, so I cannot tell you exactly what will
happen – but I know in the past their decisions have been as
severe as three quarters of suspension.
This Week
• Lecture today
– Somewhat diverse set of background information
for the rest of the course
READINGS
An explanation of research (blog post):
http://hardsci.wordpress.com/2011/12/20/what-theheck-is-research-anyway-a-guest-post-by-brentroberts/
The syllabus (will be posted Wed on website). It
contains important deadlines, policies and
information that you should be aware of.
History and Methods
Why history? Introduction to some major ideas and
disputes in brain disorders and cognition.
Why methods? Because they will come up in the readings
and lectures in the following weeks.
History and Methods
Why history? Introduction to some major ideas and
disputes in brain disorders and cognition.
Why methods? Because they will come up in the readings
and lectures in the following weeks.
You do NOT need to worry about memorizing anything
about history and methods for this course!!
The idea of LOCALIZATION
and introduction to the “lesion” method
First reference to the brain
The Edwin Smith Papyrus (1700 BC - 3000 BC): First
medical document in history.
Discusses 48 medical cases, some referring to the brain,
spinal cord. Mostly trauma. Title, examination,
diagnosis, treatment sections.
Each case was classified as favorable, uncertain, or
unfavorable (expressed in the words, ‘an ailment not to
be treated’)
Gall and phrenology
Gall (born 1758)
Brain areas have distinct
functions.
Head and skull shape over
those areas reflect how
developed that function is
There was no scientific proof for phrenology as Gall proposed it,
but the idea is thought to mark the beginnings of human
brain mapping.
Paul Broca and Patient Leborgne
In 1861, reported the historical case of patient
Leborgne, also known as “TAN”
Sudden loss of speech (can only utter the
syllable “tan”) and right hemiparesis.
Relatively intact language comprehension.
Autopsy revealed cavity in left frontal lobe. Broca believes this is
the “special faculty of articulated language”
BUT MORE ON APHASIA LATER !
Carl Wernicke
Some patients are fluent but still have language
problems.
Posterior lesions can cause impairment of auditory comprehension
of language (sensory deficits).
BUT MORE ON APHASIA LATER !!
19th Century Critics of Localization
Hughlings Jackson
“To locate the damage which destroys speech and to localise speech
are two different things”
“Different amounts of nervous arrangements in different positions
are destroyed with different rapidity in different persons.”
Noted fluent aphasias, years before Wernicke
Noted non-linguistic deficits in aphasics
19th Century Critics of Localization
Sigmund Freud
“We must not search for the physiological substratum of mental
activity in this or that part of the brain, but we have to regard it as
the outcome of processes spread widely over the brain.”
“On Aphasia: A Critical Study” (1891)
Importance of sensorimotor systems
Also noted individual differences
20th Century Critics of Localization
Karl Lashley - the arch-antilocalizationist (1890 - 1958)
Learning and Memory
Rat and maze experiments, removing cortex
The Equipotentiality Principle: all cortical areas can substitute
for each other as far as learning is concerned.
The Mass Action Principle: reduction in learning is
proportional to the amount of tissue destroyed; the more
complex the learning task, the more disruptive lesions are.
Early/Mid 20th Century Advances
Cytoarchitectonic mapping of human brain
(Brodmann,1909)
Psychometrics & Statistical Evaluation

E.g, intelligence testing
Neuropsychological tests for human patients

From the 30’s on clinical tests were developed,
standardized, improved
Stimulation in surgical patients
Penfield (50’s)
Patients about to
undergo surgery for
severe epilepsy.
SUMMARY:
In their historical context, we have already learned
about the following methods used to study the brain,
which provide different kinds of information:
- Ablation (removing brain tissue from animals)
- Lesion (studying patients with brain damage)
- Stimulation (animal and human)
- Neuroanatomy (finding anatomically distinct areas)
What other methods are used?
Other modern methods
• Neurophysiology
– Recording from neurons - analyzing functional and
computational properties
– Mostly animal, some human studies
– Invasive!
• Imaging the human brain non-invasively
– CT, MRI, DTI: Structure
– EEG, MEG, PET, fMRI: Function
• More advanced animal lesion studies (targeting
specific systems or neurotransmitters)
• Genetic studies
• Computational modeling
• And more…
Structural Imaging: CT Scans
Since the 70’s
Structural Imaging: MRI Scans
Higher resolution than CT
Much more flexible, can “weight” different tissues differentially
Cannot scan if there is metal so CT is still used.
EEG/ERP
EEG: Scalp electrodes. Very small potentials
when neurons are active. But because there
are a lot of neurons and because neighboring
neurons frequently are active close together
in time we can pick up signal.
ERP: time-locking the recording of the EEG to
the onset of events (such as a person reading
a word), and averaging across trials.
Functional Imaging: PET and fMRI
PET: Emissions from radioactively
labeled chemicals injected into the
bloodstream.
Blood flow, oxygen, glucose metabolism,
or drug concentrations .
fMRI: Iron in hemoglobin in blood is used as
a local indicator of functional activity. MRI:
One nice looking image
fMRI: A series of lower res. Images
Then correlate the series of images with
what the subject was experiencing to find
areas of the brain related to perception,
cognition, emotion, etc.
…
Brain, Vasculature
and Stroke
Vascular System
Brain function is dependent on oxygen
Two main arterial supplies to the brain:
– Carotid Arteries
– Vertebral/Basilar Artery
Exercise
Try to label without looking at the legend
1 anterior cerebral artery
2 left middle cerebral artery
3 anterior communicating artery
4 posterior cerebral artery
5 posterior communicating artery
6 internal carotid artery
7 common carotid artery
8 vertebral arteries
9 external carotid artery
10 basilar artery
11 right middle cerebral artery
12 circle of willis
Stroke – Cerebrovascular Accident (CVA)
Reduction in or disruption of blood flow to brain
Two major categories:
– Ischemic (blockage of artery)
• Clot may form in artery. This is called thrombus. If it
completely blocks the artery, it causes a thrombotic
stroke.
• Clot may travel from somewhere else (e.g., heart) to the
brain and block artery. This is called an embolism. It
causes an embolic stroke.
– Hemorrhagic (damage or tear in artery)
• Intracerebral hemorrhage
• Subarachnoid hemorrhage
Symptoms of stroke
Headache
Other symptoms depend on the severity of the stroke and
part of the brain affected:
Muscle weakness in the face, arm, or leg (usually just one side)
Numbness or tingling on one side of the body
Trouble speaking or understanding others
Problems with eyesight
Sensation changes that can affect touch, pain, pressure, temperatures
perception
Change in hearing
Change in alertness (including sleepiness, unconsciousness, and coma)
Change in personality, mood, or emotions
Confusion or loss of memory
Difficulty swallowing
Changes in taste
Difficulty writing or reading
Loss of coordination or balance, dizziness, vertigo
Lack of control over the bladder or bowels
Medical Issues
Physical deficits rather than cognitive deficits attract
the most attention immediately after stroke
Speech/language and motor problems are common
due to prevalence of MCA strokes (lots of cortex
served by that artery)
Physical rehabilitation is often readily prescribed
Speech/language/cognitive rehabilitation can help, but
is not always available or sufficient (insurance!)
50-75% of stroke patients have persistent cognitive
impairments.
Other Issues
Cognitive problems associated with stroke vary in
relation to the region of brain injury.
Acute stage and chronic stage vary, depending on
region as well as from person to person.
Damage to certain cortical areas may generate
notable cognitive signs: aphasia, agnosia, etc.
Often also “non-cognitive” signs such as emotional
instability or loss of initiative.
High co-morbidity with depression. Hard to
differentiate from cognitive dysfunction.
High co-morbidity with chronic pain.
Lesion and Hypoperfusion
From reading: Gottesman & Hillis
Transient Ischemic Attack (TIA)
Temporary disturbance of blood supply to an area of
the brain, which results in a sudden, brief decrease
in brain function.
Causes are similar to CVA.
Physical or cognitive effects typically resolve within an
hour to 24 hours.
There is rarely persistent damage following a TIA
But TIAs can signal an impending stroke.
Summary
Vascular incidents must be carefully followed
Recurrence is common
Multiple vascular events may result in a
dementia complex
Both physical and occupational/cognitive
therapy are important in promoting
recovery following stroke