PSYC10003 Lecture Notes - Inferior Frontal Gyrus, Living Brain, Aphasia
6. Methods for Studying the Living Brain
Clinical Neuropsychology
• A discipline closely allied with Behavioural Neuroscience
• In addition to helping with the diagnosis, management and treatment of patients with neurological
disorders, an important goal of clinical neuropsychology is to explain normal brain-behaviour
relationships by assessing how the system breaks down after damage.
• A key principle underlying the approach of clinical neuropsychology is to establish patterns of
association and dissociation in the behaviour of brain damaged individuals. This provides a way to
describe the functional modules of perceptual and cognitive processing that have been affected by
the damage, and those that have been spared.
• TV analogy: one has video but no audio, one has audio but no video. Without needing to examine
electrical components, can deduce that picture and sound controlled by separate processes as either
function can be damaged in isolation
Broas Aphasia – a disorder of spoken language
• Broas to patiets:
o Lost communication through speech but could still make lip, tongue and mouth movements
o Could understand what was said to them
o Both had lesions in LH, in posterior part of inferior frontal gyrus
o Broca concluded this region responsible for expressive language: Broca’s area
o Broca’s aphasia: laguage ipairet that results fro daage to Broas area.
• Broas aphasia
o Nonfluent aphasia/expressive aphasia
o Aware of problems but slow laborious nonfluent speech
o Have difficulty with grammatical function words (a, the, some, in, about)
o May be able to say some content words (words that convey meaning)
o Agrammatism – problems in comprehending or using grammatical constructions (e.g., the
use of –ed at the end of words)
o Anomia (without name) – a difficulty in finding (remembering) the appropriate word to
describe an object
o Apraxia of speech – an impairment in the ability to program movements of the tongue, lips
and throat required to produce the proper sequence of speech sounds
o Different patients will have different problems depending on location/size of lesion
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2
Werikes Aphasia – a disorder language comprehension
• Carl Werikes patiets:
o Lost ability to comprehend speech but not deaf
o Remained fluent in speech but meaningless
o Daage to LH, posterior to Broas area i posterior part of superior temporal gyrus
o Proposed this region must mediate ability to comprehend meaning for words: Wernicke’s
area
o Wernicke’s aphasia: oprehesio defiit that follos daage to Werikes area
• Werikes aphasia
o Fluent and unlaboured speech; no hesitation finding words and articulation
o Will use grammatical function words and prosody (melody; rising and falling tones we use in
speech to help convey meaning or emotion) of speech Is normal
o May use few content words or insert nonsense words or jargon
o Often unaware of impairment; this comprehension deficit may prevent from realizing faulty
speech
The discovery of two distinct types of language impairment following damage to two different cortical areas
of the left hemisphere is a good example of the contribution of clinical neuropsychology to our
understanding of normal brain function. The fact that there is a dissociation between processes associated
with speech production and those associated with comprehension suggests that these abilities represent
distinct functional modules of the mind. These functional modules also happen to be subserved by distinct
regions of the brain, though this need not always be the case.
Limitations of Clinical Neuropsychology
1. Patients with brain lesions may have medical problems that prevent intensive testing
2. Since lesions are accidental, no two patients will have identical brain pathology; difficult to replicate
experimental findings in other cases
3. Key assumption: lesions only affect functions of tissue destroyed, leaving functions of other areas
unaffected. Probably never true; brain lesions can cause swelling in distant brain sites that are not
directly destroyed. As all areas of brain are connected with many other areas, damage to one
structure will change inputs and outputs of many other regions
4. Because hua ases are eperiets of ature, ot possible to control size/location of damage.
Many patients have extensive lesions or diffuse damage that makes it impossible to link a particular
area of the brain with a particular function
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3
Ablation studies in animals — role of Hippocampus in Memory
Some researchers turned to animals as they are unable to specify location and extent of damage in human
cases
• Experimental ablation (to carry away): making small lesions in distinct parts of the brain of animals
and to observe the effects of lesions on behaviour
o May be achieved surgically, using radiofrequency energy or injecting toxic chemicals to
destroy neurons in area
o All invasive; usually carried out with strict ethical guidelines and usually under anaesthesia
o Main advantage: location of lesion can be fairly precise
o Determined role of parts of limbic system: hippocampus, amygdala and surrounding cortex,
in learning and memory (H.M.)
o As unethical on humans, usually use animals
Delayed non-matching to sample
Delayed non-matching to sample task: experimental task often used to test learning and memory in
monkeys.
• monkey separated from two food wells by an
opaque screen
• Initially experimenter hides food reward in one
of the wells by covering it with a card with a
distinctive symbol
• screen is raised and the monkey is shown the
correct response, which allows him to retrieve
the reward
• The screen is then lowered again and a food
reward hidden beneath a card with a different
symbol to that used in the first trial
• After a delay, during which the monkey must
remember the two symbols, the screen is raised
again, and the monkey must choose which of the
two cards the reward is hidden beneath
• After just a few trials a normal monkey will learn the simple rule of the task: after the delay the food
will always be hidden under the card that was NOT rewarded on the first trial (hence the tasks odd
name non-matching to sample)
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