Early discoveries of brain function
and localisation
Dr. Paul Dockree, History of Psychology: PS1203, 2009
What is neuropsychology?
“In any well-made machine one is ignorant of most of the parts – the
better they work the less we are conscious of them…it is only fault that
draws attention to the existence of a mechanism at all.” (Craik, K., 1943)
TV set analogy:
Faulty TV sets:-no sound but intact picture
-no picture but intact sound
-picture without colour (ie black & white pic)
-colour without picture?
What is neuropsychology?
• The experimental neuropsychologist asks, “What pattern
of behavioural dysfunction occurs when a particular brain
region is damaged or lesioned?”
• The clinical neuropsychologist asks, “How can normal
function be restored or compensated for in the brain?”
• Science-Practitioner Model
• How did the field evolve?
• John Hughlings Jackson’s (1835-1911) first
credible human localisationist view – evidence
from epileptic patients.
How did the field evolve?
Broca’s Aphasia
In 1862, showing brain lesions in a stroke patient who could understand
language but could not speak (could only say "tan"), he demonstrated that
the left frontal lobe was responsible for articulation of speech.
How did the field evolve?
Wernicke’s Aphasia
Like Broca, Wernicke investigated a similar stroke victim. But this time
the patient could speak but made no sense. The damaged area was
around where the temporal and parietal lobes meet in the posterior part
of the left hemisphere. His findings further revived the localisationist
view.
Wernicke’s aphasics show deficits in language comprehension but
intact articulation
How did the field evolve?
Speech content of a Broca’s and Wernicke’s
aphasic
•
To mean: "The dog needs to go out so I will take him
for a walk.“
•
•
a Wernicke’s aphasic patient says:
“You know that smoodle pinkered and that I want to get him
round and take care of him like you want before.”
an Broca’s aphasic patient says:
“Walk dog.”
The logic of lesion analysis
Function X: speech articulation
Function Y: speech comprehension
Brain function
Function X
Speech
articulation
Function Y
Speech
comprehension
Area A: Broca’s area
Area B: Wernicke’s area
Structures to be Lesioned
Area A
Area B
Broca’s area
Wernicke’s area
Impairment
Can’t speak fluently
No Impairment
In fluent speech
No Impairment
Understanding
speech of others
Impairment
Can’t understanding
speech of others
The logic of lesion analysis
Function X: speech articulation
Function Y: speech comprehension
Brain function
Function X
Speech
articulation
Function Y
Speech
comprehension
Area A: Broca’s area
Area B: Wernicke’s area
Structures to be Lesioned
Area A
Area B
Broca’s area
Wernicke’s area
Impairment
Can’t speak fluently
No Impairment
In fluent speech
No Impairment
Understanding
speech of others
Impairment
Can’t understanding
speech of others
The logic of lesion analysis
• Function X (articulation of speech) depends on area A
(Broca’s area) but not area B,
• whereas function Y (comprehending speech) depends
on area B (Wernicke’s area) but not area A.
• Double dissociation – Gold standard of
neuropsychological research
How did the field evolve?
Wilder Penfield
• Growing evidence for localisationist view in early 20th
century – direct evidence from motor and sensory maps
in the brain from early work of Wilder Penfield.
• Features drawn according to how much brain space they
take up in somatosensory cortex.
How did the field evolve?
Wilder Penfield
Stimulating the temporal lobes could he elicit meaningful,
integrated responses. Physical basis for memory: an "engram.”
How did the field evolve?
• Holistic approach:
• Karl Lashley (1935) – lesions made throughout the
brain do not necessary create problems when learning
a new task (e.g., maze learning in rats).
• A lesioned brain is like a new system, not an old
system with one part missing.
How did the field evolve?
• Localisation vs holistic:
A Compromise-
• Complex functions (e.g., perception, memory,
reasoning) cannot be accomplished by a single brain
process or brain region; integration of functional
neuroanatomy – holistic view
• Nevertheless, the simple processes themselves that are
recruited to exercise complex functions are localised –
localisation view
• Brain damage may reveal something about the
underlying organisation of the system.
• What are the methods used in neuropsychology?
• Psychometric testing:
• database of standardised scores
• Clinical patients vs. healthy controls
• Clinical observation:
• Diagnosis
• Assessment
• Rehabilitation
• Neuroanatomy:
• Connectional studies in animal studies
• projection maps (e.g., LGN to visual cortex)
What are the methods used in neuropsychology?
• Lesion analysis:
• selection of animals or humans with discrete
brain damage to areas thought to be essential in
a particular processing chain.
• one of the oldest methods for studying brain
function in humans and animals.
• single most informative technique available for
understanding the neural bases of behaviour.
• http://www.wwnorton.com/college/psych/psychs
ci2/content/activities/ch04a.asp#movie
What are the methods used in neuropsychology?
• Types of lesions:
• cerebrovascular accidents (CVA; stroke); occurs
when blood flow to the brain is disrupted;
What are the methods used in neuropsychology?
• Types of lesions:
• penetrating head injuries, from gunshot or other incidents;
What are the methods used in neuropsychology?
•
•
Types of lesions:
Following traumatic brain injury (TBI), diffuse white matter damage typically co-occurs with more
focal lesions or hematomas (blood clots) and contusions (bruising) damaging the dense collections
of cell bodies (grey matter)
What are the methods used in neuropsychology?
• Types of lesions:
Neurodegeneration: widespread area of tissue death
or abnormal cell functioning due to
neuropathology (AD, PD);
healthy older
person
Pt with AD
What are the methods used in neuropsychology?
• Deliberate lesions - on experimental animals.
• tissue excision, where tissue is deliberately removed
(usually by aspiration);
• tissue destruction, tissue is destroyed electrolytically
or chemically (e.g., MPTP, a chemical agent to create
an animal model of Parkinson’s disease);
What are the methods used in neuropsychology?
• tissue deactivation, where tissue is reversibly
deactivated via injections of local anaesthetic or
through chemical cooling;
• tissue disconnection, where brain areas are left
intact but fibre tracts which communicate
between these areas are permanently cut or
temporarily interrupted (by anaesthetic or
cooling);
What are the methods used in neuropsychology?
•Neurosurgery is often conducted on humans in order to
relieve conditions such as drug-resistant epilepsy (patient
H.M.), relief from intractable pain or brain tumours.
Laterality
The Wada test: sodium amytal technique
•Sodium amytal is injected into one
hemisphere at a time
•The effect is to shut down any
language and/or memory function in
that hemisphere in order to evaluate
the other hemisphere ("half of the
brain").
•Then the patient is engaged in a
series of language and memory
related tests
Neurorehabilitation
• Broca and aphasia therapy (1865)
• Broca concluded that the patient, “could recognize a
word as one would a face or landscape, the details of which had
never been analysed”
• it deosn't mttaer waht oredr the ltteers in a wrod are, the olny
iprmoetnt tihng is taht the frist and lsat ltteres are at the rghit
pclae. The rset can be a tatol mses and you can sitll raed it wouthit
a porbelm. Tihs is bcuseae we do not raed ervey lteter by it slef
but the wrod as a wlohe.
Neurorehabilitation
• WW1- German rehabilitation
(Popplereuter, Goldstein)
• Cologne and Frankfurt centres
• WWII – Alexandra Luria:
theoretical perspective from
which to predict recovery
• Restoration of function via:
• De-inhibition
• Transfer to opposite hemisphere
• Reorganisation of the system
• Luria stressed the importance
of premorbid personality and
motivation
Is there any point to lesion analyses
now?
• A reading of the last fifteen years of the functional imaging
literature - imaging literature largely concerned with the hightech confirmation of the preceding one hundred and fifty years of
careful neuropsychological analysis.
• PET and fMRI studies do not provide a definitive conclusion
about whether or not a particular area is absolutely required in a
processing chain.
• The only way to definitively decide if function X is dependent on
area A is to remove that area from the processing chain.
Is there any point to lesion analyses
now?
•
Lesion analysis complements functional imaging by identifying necessary and
contributing components of the processing chain; functional imaging also
allows the identification of specific components of the processing chain.
•
Overall one strategy complements and underlines the other.
•
nb: All of the above techniques require that you get the psychology right - if
you do not have a good functional theory, applying technology will not get you
a meaningful answer.
•
Further understanding of lesions and their functional role is key for targeted
rehabilitation of function and the guided recovery of patients.
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Lecture 8: Early Discoveries of Brain Function and Localisation