Samenvatting
Samenvatting ter voorbereiding tentamen van Brein & Cognitie 3
Met deze complete samenvatting, inclusief lecture notes, heb ik geleerd voor het tentamen van Brein & Cognitie 3 en dit vak succesvol afgerond!
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Voorbeeld 4 van de 53 pagina's
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Voorbeeld van de inhoud
B&C3 lecture notesCourse tips
Ff opletten op 4e vs 5e editie.
Keep up with the reading :(
Lectures en boek verschillen dus alles lezen.
Focus op de Learning Objectives en de take home messages
Lecture 1: introduction week 1
Descartes (1633): Inputs are passed on by the sensory organs to the pineal gland in the brain and
from there to the immaterial spirit”.
Gall (~1800) introduced the idea of localization of function, just like in the organs: ‘phrenology’.
Broca (1864) found evidence for localization.
When assessing abnormal behaviour distinct approaches:
o neurology (observable brain abnormalities)
o psychiatry (normal looking brain, freud)
Nowadays combined (Neuropsychiatry, Neuropsychology, Cognitive Neurology)
Behaviour arises from the brain: If you care about behaviour, you care about brains
Toolbox
Cognitive psychology and behavioural research…
• … provide insight into mental transformations / how information is processed
• Cognitive psychology = the study of mental activity as an information-processing problem.
• We do not directly perceive the world, but rather ‘interpret’ incoming information
o (vb: kleurenblind, zelfde stimuli maar je interpreteert het anders)
• Mental processing as an information processing problem:
o Information processing depends on pre-existing internal representations (like beliefs,
concepts, desires, perceptions). Context matters.
Posner: different response latencies reflect the degrees of processing.
o These mental representations undergo transformations (an olfactory sensation calls up
a memory, or a memory may alter how we perceive something) these processes are
also modulated by our attention.
Rotate the shape to find out if they are the same
• Cognitive psychology uses behavioral experiments to find out what these
representations and transformations are
o Memory comparison task. Does own brain process info parallel or serial
processing?
o Limitations in information processing also inform us about mental
transformations
o Incongruent Stroop condition shows
2 representations are activated, ‘word’ representation is dominant, at least when
reporting verbally
stroop effect demonstrates the multiplicity of mental representations: one
representation corresponds to the color of each stimulus and second corresponds
to the color concept associated with each word.
, The fact that participants name colors slower when ink and words are
inconquerent second representation is activated even though it is irrelevant to
the task.
• Cognitive psychology uses behavioral tasks to study mental representations and
transformations
o Useful to understand mental processes and their limitations
• Limitations
o cannot probe anything that is not expressed in behaviour
o no insight in how these processes are implemented in the brain
Patient studies
• Study how ‘cognition’ breaks down may tell us about how it is organized
• But with knowing what things you cannot do anymore when region falls out, it does not tell
us what that region exactly does.
• Study the cognitive function of brain regions through brain damage
o If a part of the brain is important for a particular function, this function will deteriorate
(verslechteren) after damage to this region
o Functions often have many components: what component leads to the disability in the
patient? e.g. bad performance on reading test: potential causes: blindness, attention
disorder, language disorder, motivation.
• Single vs Double dissociation
o When a group of patients is doing worse, are you measuring some specific process that
is being impaired or are you measuring that patients overall tend to do worse.
o Double are stronger evidence than single that damage to a particular brain region may
result in a selective deficit of a certain cognitive operation.
o Task sensitivity assume that the two tasks are equally sensitive to differences between
the two brain areas but one tasks can be more demanding, with double association this
is ruled out
o It is not just that patients are doing generally worse (bc they are patients they have a
harder job), but do worse on some tasks and good on other tasks so there is a specific
effect rather than the general effect that patients do worse.
o An double dissociation identifies whether two cognitive functions are independent of
each other (it is no longer reasonable to argue that a difference in performance results
merely from the unequal sensitivity of the two tasks).
• Patient lesion research: study functional role of brain regions through brain damage
• Patient studies tell us what regions are necessary. But not how a ’normal’ brain works.
• Limitations and caveats (kanttekeningen)
o Compensation mechanisms (andere hersengebieden nemen taken over)
o Exact damage location may vary between patients
, o Specificity of damage
o Double dissociations needed to show specificity (not only for lesion patients!)
o Surgical intervention in non-healthy patients only
o Most patient studies show correlation, not causation!
Tempting to conclude a causal link in the absence of a manipulation.
Case study: relation PTSD and brain size (hippocampus) bc stress makes more
glucorticoids leads to hippocampal atrophy. But with twin study maybe other way
around. Small hippocampal size was a risk factor for developing PTSD and PTSD
alone did not cause decreased hippocampal size
Thus: We need controlled interventions
o Interventions to assume causality
Lesion surgery
Frontal lobotomy
Split brain (epilepsy)
Epilepsy source removal
Brain stimulation
Patients: deep brain stimulation, ECT
Healthy: transcranial magnectic stimulation, Focussed Ultrasound
Stimulation, TACS
Psychopharmacology
Neurosurgery with patient studies: patient is their own control but
patients did not have a normal brain prior to surgery. So cannot extend
the results to the normal brains.
Manipulating the brain
• Transcranial magnetic stimulation (TMS)
o generate artificial reversible ‘lesions’ or
activations
o disturbing cognitive processes
• Related to (neurological) patient lesion studies
Looking inside the brain
• Many research tools, each with their own strengths
and weaknesses.
o Difference in spatial and temporal resolution
o Dependent on what is available
• Method determines which conclusions you can
draw
• Combining methods to complement each other (= Converging evidence) conclusions are
stronger when supported by different approaches to the same question
• Additive logic = use 2 tasks, that differ only in the function you want to study. Assume that
all else is equal, assume that this function is ‘turned on’ in an additive faction. Subtract
activity on the 2 tasks. Assume that their difference is the region that ‘codes’ for the
function you are after.
o E.g. when interested in color processing testing color picture in MRI – black-white
picture in MRI to remove the other thoughts like: loud scanner, uncomfortable,
groceries etc.
, o you always need a baseline condition to compare it to. But does the experiment has a
base line condition? Showing black and white photo of house, is that color processing
or animate objects processing?
o there are a lot of caveats.
Why so many approaches?
Each approach has its strengths and limitations
Different methods answer different questions
To understand the brain and behaviour, we have to combine different methods
Converging evidence: conclusions are stronger when supported by different approaches to the
same question
Literature chapter 3
Take Home Message
Researchers study patients with neurological disorders or brain lesions to examine structure–
function relation- ships. Double dissociations are better evidence than single dissociations that
damage to a particular brain region may result in a selective deficit of a cognitive operation
Traumatic brain injuries are the most common cause of brain lesions. Even when the injuries are
mild, they can have chronic neurodegenerative consequences
Impairments in a particular cognitive process do not mean that the damaged part of the brain
“performs” that process. Brain lesions can disrupt processing in intact brain structures or disrupt
brain networks on a larger scale
Single-cell recording enables neurophysiologists to record from individual neurons and correlate
increases and decreases in neuronal activity with sensory stimulation or behavior. With
multiunit recording, we can record the activity of many neurons at the same time
Electrocorticography (ECoG) and electroencephalography (EEG) are two techniques to measure
the electrical activ- ity of the brain. In ECoG, the electrodes sit directly on the brain; in EEG, the
electrodes are on the scalp. These methods can measure endogenous changes in electrical
activity, as well as changes triggered by specific events (e.g., stimuli or movements). Although
the resolution of ECoG signals is much greater than that of EEG, it is used only in people
undergoing neurosurgery
An event-related potential (ERP) is a change in electrical activity that is time-locked to specific
events, such as the presentation of a stimulus or the onset of a response. To detect the relatively
small changes in neural activity triggered by a stimulus, EEG signals are averaged from multiple
trials
Magnetoencephalography (MEG) measures the magnetic signals generated by the brain.
Sensitive magnetic detectors placed along the scalp measure the small magnetic fields produced
by the electrical activity of neurons. We can use MEG in an event-related manner similar to ERPs,
with similar temporal resolution. The spatial resolution can be superior because there is minimal
distortion of magnetic signals by organic tissue such as the brain or skull
Positron emission tomography (PET) measures metabolic activity in the brain by monitoring the
distribution of a decaying radioactive tracer. A popular tracer for cognitive studies is 15O
because the distribution of oxygen increases in neural regions that are active. Researchers can
design tracers to target particular types of tissue. The PiB tracer was designed to bind to
betaamyloid, providing an in vivo assay of an important biomarker for Alzheimer’s disease
In functional magnetic resonance imaging (fMRI), the MRI scanner is configured to measure
changes in the oxygen content of the blood (hemodynamic response). We assume these
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