lecture 6 - neuropsyc intro Flashcards
what is neuropsychology
Study of the link between brain and behaviour
* Fundamentally about studying impairments in
individuals who have suffered brain damage
what are some causes of brain damage
- Traumatic injury (car accidents, falls, projectile)
- Stroke (leading cause on non-traumatic injury)
- Lack of oxygen (hypoxia)
- Tumors
- Brain infections or inflammation (e.g., encephalitis, hydrocephalus)
- Nutritional deficiencies
- Chronic alcohol abuse (e.g., Korsakoff’s syndrome)
- Surgery (e.g., intractable epilepsy)
clinical neuropsychology vs cognitive neuropsychology
Both concern impairments in normal functions in the brain / brain damage
* Clinical neuropsychologists are interested in understanding the
impairment
* Cognitive neuropsychologists are interested in learning about
normal functions from studying the impairment
what do clinical neuropsychologists focus on
Focus on assessment (diagnosis and prognosis),
management and rehabilitation for patients
* Define pathological conditions/characterise deficits considering cognitive, behavioural, emotional and social aspects
focus of cognitive neuropsychology
-the two types of cognitive neuropsyc
Understand normal functions in the brain by
studying patterns of impairment after brain damage
* Map functions to brain regions
* Two types of cognitive neuropsychology:
* Strong: start out with no theory and use patient data to infer / construct theory
* Weak: use patient (damaged brains) data to constrain / refine theory, (could be a theory developed by already studying a healthy brain)
Assumptions in cognitive
neuropsychology
- Universality
- Modularity
- Fractionation
- Transparency
need to understand these if were gonna use damaged brains to understand our brains
assumption of universality
Cognitive processes are the same in all individuals
-the way our brains are organised are roughly the same
-will find same building blocks for the same processes
-Still some scope for individual differences but the average of a group of individuals should be a
good reflection of any individual in the wider population
-the assumption is not that brains are identical, we just have same architecture
assumption of modularity
Complex cognitive processes can be broken down into simpler processing units
-can break individual processes in the brain into a series of steps
assumption of Fractionation
-more important in neuropsyc
Brain damage can result in the selective impairment of a particular cognitive process
-you can selectivley impair one of your cognitive processes in the brain, and if you do that you them removed or impair the behaviour associated with the process
assumption of Transparency (aka subtractivity)
The cognitive system of a brain-damaged patient is fundamentally the same as that of a normal subject except for a “local” modification of the system = all other processes are intact
-the impairment shouldnt impair other functions in the brain
-otherwise healthy and intact brain
are these assumptions justified
fractionation
modularity
these two assumtpions are hard to justify in terms of evidence but can be justified by theory
-hard to show modularity is right or not
-fractionation- do have many patients to show this so cant necessarily argue against
are these assumptions justified
-universality
structure
function
structure
-the way it looks is shown to be similar in images
-the lines (sulci) they key lines are roughly the same but do vary a bit
-all brains have 2 halves (not identical) , tend to have more mass in the left front and more mass in right back.
function
-when you look at activity in the brain, eg fmri studies , group study, showing average activity,
-often find that the most active site across all participants is responsible for that function
-photos show 9 healthy individuals brains doing a word recognition task
-red circle indicates most active location, their is much variation
-shows there is variation of function in brain
are these assumptions justified
transparency
-adapting to brain damage,
Marotta, Genovese &
Behrmann (2001)
*Disruption to the cognitive
processes
-often find that problems are not just in one cognitive process, eg people who struggle to recognise faces sometimes also cant recognise objects well
-brains can adapt to the damage
* Behavioural compensation 9find behavioural solution)
* Neural re-organisation (re organise things in the brain)
adapting to brain damage
-behavioural compensation
-neural re organisation
example of adapting by behavioural compensation
-patient with visual object agnosia
-given picture of apple asked to identify it
-you see in the end he succesfully identifies the apple, but not in the method in the normal we do
-he used a different behavioural strategy, he figured if things have corners and edges etc then they’re likely to be manmade
example adapting by neural re organisation:
-the same brain scanned at differnt times
-one photo shows damage in the inidvidual , have localised damage in right hemispeher, where face recognition tends to happen
-in the other scan its shown that activity is spread out when looking at faces, has learnt to recognise faces still, but activity goes on also in left hemisphere (not normal place thats active when recognising faces)
are these assumptions justified
transparency
-pre surgery brain function
-other surgical damage
-sometimes brain damage is caused by surgery
-the two halves of brain have been researched by looking at split brain patients, patients 2 hemispheres dont communicate (through surgery the corpus callosum is cut maybe bc eoilipsy etc)
-2 halves of brain operate independently - these have been studies
-the assumption here is that once the fibres are cut, the way the brain is organised should be normal (in an individual who has not had normal activation because of uncontrolled firing) is this fair? we dont know.
-after patient died they realised the surgery had caused other brain areas damage , evidence of stroke eg, also found metal clips in his brain, that corroded and damaged the tissue in the brain
ways of studying brain damaged individuals
- Patient-group studies
- Single-patient case studies
studying brain damaged
-group study approach
-look at a group of people and look at common deficits or abilities , and draw group data
Data aggregated across subjects (i.e. averaging)
* Inferences drawn from between-group comparisons:
patient group vs. control group
* Looking for ‘syndromes’: collection of symptoms which often co-occur in individuals
* Thus looking for associations of common deficits
* Can also look for common sites of damage
studying brain damage
group study problems
-Averaging across patients - the assumption of universality
Similar behavioural symptoms may arise from very different underlying
patterns of damage
* Prosopagnosia from damage to right (Marotta, Genovese & Behrmann, 2001) and left (Mattson, Levin & Grafman, 2000) hemispheres
- Similar sites of damage may be associated with very different symptoms
- Damage to right fusiform gyrus found in patients with prosopagnosia (Marotta, Genovese & Behrmann, 2001) and alexia (Leśniak, Soluch,
Stępień, Czepiel & Seniów, 2014) - Specific behavioural impairments within a syndrome may vary considerably
- e.g., different types of prosopagnosia
- Time consuming to find patients
- Risk of over-interpreting associations: the deficits may depend on functionally distinct processes that are anatomically related
- e.g., lesions to the ventral occipital lobe can produce severe deficits
in colour vision (achromatopsia) and face recognition (prosopagnosia
studying brain damage
case study approach
Look for specific single deficits in a patient
* Mainly concerns dissociations between
behaviours patient can and can’t do
* Single and double dissociations
-dissociation between what individuals can and cant do
single dissociations
-one individual has a particular problem, cant do one task
if patient can do A but not B, A & B
are (1) likely to be independent
processes in the brain and (2) may
involve different brain regions
video example shows
19 year old sarah, had a stroje
Spared word order / meaning /
comprehension (Task A intact), understood what happened to her as she produces aspect of speech
* Impaired naming / fluency (Task B
impaired), very specific
- BUT it may simply be that B is harder than A, so damage to the process / region that controls both A and B results in a more noticeable problem in B than in A
double dissociation
so can compare 2 patients
can make stronger claims that these 2 processes are different
One patient can do A but not B, another can do B but not A = strong evidence of involving different cognitive processes and brain
regions
Compare previous patient who had spared word order and meaning (Task A intact), but impaired fluency (Task B impaired)
- With this patient who has impaired word order and meaning (Task A impaired) but spared fluency of speech (Task B intact)
watch video if confused - Broca’s (first aphasia) vs Wernicke’s aphasia (second patient)
-allowed us to see where and how speech production is organised in the brain - Also different lesion sites for Broca’s and Wernicke’s aphasias
are double dissociations really the ‘gold standard’
-The need for pure cases
- Hard to find patients with damage purely to one cognitive process (and, depending on the cause of the damage, damage may be to several brain regions)
- The impossibility of precise replication, because they are based so much on the individual patient
-so long running debate over:Patient-group studies or
single-patient case studies?
Linking (impaired) functions
to structures in the brain
- What can we conclude about localisation of function in the brain from studying a brain damaged patient?
-motorcycle case (before we could study the brain properly before death)
-studied aphasia in patient in motorcycle accident,
-profound problems with speech problems
-studied him and he died a few days later
-and was able to see the brain of the individual post mortem- after death
-confirm / associate
deficits with anatomy
after death
What can we conclude about localisation of function in the brain from studying a brain damaged patient?
Imaging techniques (now study the brain with these new techniques)
-can use structural imaging to use where damage has occured in the brain using :
-CT (computed tomography) (x ray based) (tissue is brighter in damage area)
-Mri Magnetic Resonance
Imaging (MRI)
(Radio waves/magnetic field)
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