Problem 8 Flashcards
Reverse engineering
Lesion studies
Refers to a process where one attempts to infer the function of a brain region by observing what the rest of the cognitive system can + can’t do when that brain region is removed
Transcranial magnetic stimulation
TMS
Refers to a non-invasive stimulation of the brain that is caused by a rapidly changing electrical current in a coil held over the scalp
Transcranial direct current stimulation
tDCS
Refers to non-invasive stimulation of the brain caused by passing a weak electrical current through it
–> can be used to boost cognitive function (e.g. rehabilitation)
Single dissociation
Being impaired in performing one task but not in another related one
–> being impaired in both tasks but significantly worse in one is a strong single dissociation
Provide explanations for single dissociation.
- each task uses different cognitive processes
- Task-resource artifact
- -> they both use the same cognitive resources but one task utilizes more of this resource - Task-demand artifact
- -> patient performs one of the tasks sub optimally because he misunderstood the instructions
Double dissociation
Occurs when two related mental processes are shown to function independently of each other
–> most powerful way of discounting a task-resource artifact
THUS: provides evidence that 2 functions are separate/independent
The fractionation assumption
Assumes that brain damage can produce selective cognitive lesions
Transparency assumption
Assumes that lesions affect one or more components within the pre-existing cognitive system
BUT: lesions do not result in a completely new cognitive system
Universality assumption
Suggests that all cognitive systems are basically identical
Why are single case studies said to be the only acceptable method in cognitive neuropsychology ?
Because, averaging across participants may not be possible/wise as
- differences in observed performance may be attributable to differences in lesion
- determining whether the lesion is in the cognitive system can only be determined by observing each case in turn
Name the most common objections against the use of single-case studies ?
One cannot create a theory based on observations from only a single case
Name the grouping principles by which patients should be grouped in oder to associate lesion sites with deficits ?
- Grouping by syndrome
- -> best for understanding the neural correlates of a given disease pathology - Grouping by cognitive symptom
- Grouping by anatomical lesion
There are various methods for producing experimental lesions in animals.
Name them.
- Aspiration
- -> suction device - Transection
- -> cutting off discrete white matter bundles - Neurochemical lesions
- Reversible lesions
- -> temporary
Unilateral spatial neglect
Occurs when the brains attention network is damaged in only one hemisphere
–> most persistent + severe effects occur from right HP damage
Ipsilesional
Attention bias in the direction of the lesion
–> disregarding everything to the left if the patient has lesion on right HP
How does neglect affect the people suffering from it ?
- Objects present in the visual world
- Imagination
- Memory
–> they do not actually lack the memory but their attention to parts of the recalled images is biased
How can we distinguish neglect from blindness in the contralateral visual HP ?
Neglect patients do detect stimuli normally when they are salient + presented in isolation
e.g. flashes of light, wiggling of fingers
Extinction
Refers to the failure to perceive or act on stimuli contralateral to the lesion (contralesional stimuli) when presented simultaneously with a stimulus ipsilateral to the lesion (ipsilesional stimulus)
–> extinction does not occur when stimuli are presented one at a time to each hemifield
Balints syndrome
Demonstrates 3 deficits
- Simultanagnosia
- -> difficulty perceiving the visual field as a whole scene - Ocular apraxia
- -> difficulty making eye movements to scan the visual field/voluntarily moving eyes - Optic ataxia
- -> difficulty moving the hand to a specific object
THUS: disturbance in perception
Association
Suggests that the behavioral/cognitive phenomena in question are a manifestation of one underlying process
–> consistent co-occurence of 2 or more impairments
Commissurotomy/
Split brain surgery
Involves the cutting of the corpus callosum
–> supposed to stop seizures from spreading to both HPs
Sodium amobarbital test
SAT
Refers to a surgery for the relief of seizures that involves the removal of the cortex region that has been declared the origin of the patients seizures
Testing procedure of the SAT
- Barbiturate sodium abobarbital is injected into the internal carotid artery
- It then enters the cerebral circulation + passes into the ipsilateral middle cerebral artery
- This HP is then anesthetized
- Before the drug is injected the patient is instructed to extend the arms + wiggle toes
- After drug injection he suffers a hemiparesis
- Various tests can be conducted
Hemiparisis
Extreme weakness of one side of the body
Neurochemical lesions
Using chemicals to alter the normal functioning of neurons
–> reversible effects: as long as the drug os active, the exposed neurons do not function, when the drug wears off the function will gradually return
BUT: not all are reversible
Lesions studies in humans
Works by either
- picking a population with similar anatomical lesions
- Assembling a population with a similar behavioral deficit
