Neuropsychology: The Lesioned and Stimulated Brain

Question 1

Why do we study the lesioned brain?

Answer 1

-Lesioned brain leads to particular deficits, behavioral problems, etc., so studying tells something about normal architecture of cognition and human brain (ex.: alien hand syndrome)
-Classical cases
-Taxonomy of brain manipulation methods

Question 2

What is Alien Hand Syndrome?

Answer 2

-Syndrome characterized by involuntary movement typically of hand
-No control: movements occur despite what patient reports verbally to intention
-Result of brain damage

Question 3

What is reverse engineering?

Answer 3

-Inferring function of brain region (or cognitive mechanism) by removing it and measuring effect on rest of system
-Disruption of brain can come from different causes: natural damage (stroke, trauma), elicited damage (animal models) or virtual damage (harmless temporary changes induced electro-magnetically (TMS))

Question 4

Why are classical cases important?

Answer 4

-Able to infer function of certain regions
-Able to know how normal function works
-Reverse engineering

Question 5

What different taxonomies are there of brain manipulation methods?

Answer 5

-First: distinction between non-invasive brain stimulation methods and other methods
-Second: more refined taxonomy where each of different causes divided into subcategories

Question 6

What does the taxonomy of brain manipulation methods look like with the first method?

Answer 6

Distinction between non-invasive brain stimulation methods and other methods
-Non-invasive brain stimulation methods: tFUS, rTMS, tDCS, tRNS, tACS, single-pulse TMS
-Other methods: lesion, drug manipulation, local pharmacological inactivation, opto-genetics, micro-stimulation

Question 7

What does the taxonomy of brain manipulation methods look like with the second method?

Answer 7

More refined taxonomy where each of different causes divided into subcategories
-Natural damage
–>Neurosurgery
–>Strokes: ischemic infarction or hemorrhage
–>Traumatic brain injury: closed or open
–>Tumor
–>Viral infection
–>Neurodegenerative disease: Alzheimer’s disease, Parkinson’s disease, frontotemporal dementia, etc.
-Virtual (temporary) damage
–>TMS
–>tES
-Elicited damage
–>Aspiration
–>Transection
–>Neurochemical lesions
–>Reversible lesions

Question 8

What different causes of natural brain damage are there?

Answer 8

-Neurosurgery
-Stroke
-Traumatic brain injury
-Intracranial tumors
-Viral infections
-Neurodegenerative disorders

Question 9

What are characteristics of neurosurgery as a cause of natural brain damage?

Answer 9

-Performed to remove focus of epileptic seizures
-Side effects
–>Removal of medial temporal lobe: permanent brain damage and memory problems
–>Split brain surgery (cutting of corpus callusom): brain networks affected (can’t communicate anymore)

Question 10

What are characteristics of a stroke as a cause of natural brain damage?

Answer 10

-Stroke: accident in arteries of brain, typically happens unexpected, but age is risk factor
-2 types: ischemic infarction and hemorrhage/bleeding
-Important to distinct types when person is having stroke: medication used in ischemic infarction cause damage in person with hemorrhage
–>Distinction by CT-scan

Question 11

What is an ischemic infarction?

Answer 11

-80% of strokes
-Neurons in brain don’t receive blood due to plaques or cloths
-Motor and cognitive problems depending on location and size of affected area
-Some arteries more vulnerable to infarction

Question 12

What is a hemorrhage/bleeding?

Answer 12

-20% of strokes
-Weak spot in blood vessel causes rupture
-Bleeding inside brain tissue
-People with aneurysm suffer more likely from hemorrhage

Question 13

What are characteristics of traumatic brain injury as a cause of natural brain damage?

Answer 13

-Injury caused by external force
-Clinically diverse picture: broad range of cognitive, emotional and behavioral disorders, outcome from complete recovery to death
-Risk factors
–>Age: 0-4, 15-19 and 75+
–>Sex: more likely in males
-Causes vary: traffic accidents, fall from height, violence, etc.
-Mechanical forces can result in: open or closed TBI
-Seen in MR-scan

Question 14

What is an open traumatic brain injury?

Answer 14

-Less common type of TBI
-When objects or bone fragments penetrate meninges
-More localized effects
-Can lead to infections

Question 15

What is a closed traumatic brain injury?

Answer 15

-More common type of TBI
-When axons get damages: diffuse axonal injury
-More widespread effects

Question 16

What are characteristics of intracranial tumors as a cause of natural brain damage?

Answer 16

-Tumor: mass of new tissue that persists and grows independently
-Origin
–>Meninges: meningioma
–>Glial cells: glioblastoma
-Classification in different ways

Question 17

In which ways are intracranial tumors classified?

Answer 17

-Benign (low-grade tumors) vs malign (high-grade tumors)
–>Benign evolve into malign without removal
-Encapsulated vs infiltrating
–>Encapsulated: distinct entity that puts pressure on brain
–>Infiltrating: tumor not separated from surrounding tissue
-Primary vs secondary
–>Primary: originate from brain tissue
–>Secondary: originate elsewhere in body as metastasis of primary tumor

Question 18

What are characteristics of viral infections as a cause of natural brain damage?

Answer 18

-Viral infection: invasion of body by disease-producing microorganism and subsequent tissue reactions
-Infections can kill neurons

Question 19

In what ways can infections kill neurons?

Answer 19

-Interference with blood supply
-Interference with glucose or oxygen metabolism
-Alter cell membranes
-Form pus
-Cause edema

Question 20

What are characteristics of neurodegenerative disorders as a cause of natural brain damage?

Answer 20

-Neurodegenerative disorders: increasing impairments in one or more cognitive functions
-Different types: Alzheimer’s disease, frontotemporal dementia (Pick’s disease), Huntington’s disease, multi-infarct (vascular) dementia, Parkinson’s disease

Question 21

What is Alzheimer’s disease?

Answer 21

-Reduced grey matter
-Deeper sulci
-Increase of cerebrospinal fluid
-Large ventricles
-Neurodegenerative disorder that causes brain damage

Question 22

What is frontotemporal dementia or Pick’s disease?

Answer 22

-Reduced grey matter
-Wider/deeper sulci
-Large ventricles
-Neurodegenerative disorder that causes brain damage

Question 23

What is Huntington’s disease?

Answer 23

Neurodegenerative disorder that causes brain damage

Question 24

What is multi-infarct (vascular) dementia?

Answer 24

-More white matter damage
-Information-processing problems
-Neurodegenerative disorder that causes brain damage

Question 25

What are dissociations in neuropsychology?

Answer 25

-Dissociation: inferring something about cognition or brain by studying pattern of deficits in patients
-2 types: single dissociation or double dissociation
-Example: writing vowels vs consonants (Cubelli, 1991; Kay & Hanley, 1994)

Question 26

What were the findings of the researches of Cubelli (1991) and Kay & Hanley (1994) about writing vowels vs consonants (dissociations)?

Answer 26

-Cubelli: observed patient who can’t write vowels, but can write consonants
-Hay & Hanley: observed patient who can’t write consonants, but can write vowels

-Writing vowels and writing consonants are independent things
-Inference that there are separate neural resources in brain for writing vowels and writing consonants
-Can lie in same location/brain area, but have different intermixed neurons

Question 27

What are single dissociations in neuropsychology?

Answer 27

-Being impaired on task A but (relatively) spared on task B
–>Classical or strong dissociation
–>Example: patient with apraxia
-Inferences can be made from single dissociation

Question 28

What is classical dissociation?

Answer 28

-Single dissociation
-Patient is impaired on task A, but performs normal on task B

Question 29

What is strong dissociation?

Answer 29

-Single dissociation
-Patient is impaired on task A and B, but more impaired on one of the two tasks
-Both tasks use different cognitive functions and different neural resources

Question 30

What is apraxia?

Answer 30

-Able to grab objects when asked
-Not able to mimic use of objects when asked
-Suggests that grabbing and pantomiming use different cognitive functions and different neural resources

Question 31

What types of inferences can be made from single dissociations?

Answer 31

-Task A and B rely on different cognitive processes and/or different neural resources
-Task-demand artifact: suboptimal performance, misunderstanding
-Task-resource artifact: same resource, but more needed for task A

Question 32

What are double double dissocations in neuropsychology?

Answer 32

-Two or more single cases with complementary profiles or strengths and weaknesses (example of vowels and consonants)
-Used to infer that 2 tasks/stimuli are separate neural and cognitive resources

Question 33

What are associations in neuropsychology?

Answer 33

-Association of symptoms: being impaired on task A and task B
–>Perhaps functions are close together in brain?
-Syndromes: cluster of different associated symptoms

Question 34

What are the 2 traditions of human neuropsychology?

Answer 34

-Cognitive neuropsychological approach
-Classical neuropsychological approach

Question 35

What are characteristics of the cognitive neuropsychological approach of human neuropsychology?

Answer 35

-Can particular function be spared/impaired relative to other cognitive functions
–>Addresses questions of what building blocks of cognition are
–>Using single case methodology to answer question
-Associated with single dissociation

Question 36

What are characteristics of the classical neuropsychological approach of human neuropsychology?

Answer 36

-What functions disrupted by damage to region X
–>Addresses questions of functional specialization, converging evidence to functional imaging
–>Using group study methods to answer question
-Associated with double dissociation

Question 37

What are the different assumptions underlying single-case studies?

Answer 37

-Fractionation assumption
-Transparency assumption
-Universality assumption

Question 38

What is the fractionation assumption?

Answer 38

Damage to brain can selectively impair cognitive function

Question 39

What is the transparency assumption?

Answer 39

Other cognitive functions operate at normal pre-injury levels of efficiency
-Criticism, because of plasticity in brain

Question 40

What is the universality assumption?

Answer 40

-All individuals share same cognitive systems
-Criticism, because inter-individual differences may skew data

Question 41

Why would you use single-case studies instead of group studies?

Answer 41

-Researcher gets observations with individual differences when doing group studies
-Because every lesion is unique, it’s best not to cross-average across patients
-Evidence against group studies
-Use single-case methodology if you want to make inferences about the cognitive system

Question 42

What are characteristics of group-studies?

Answer 42

-Different ways of grouping patients
-Complications
-Useful if you want to make inferences about lesion-deficit associations

Question 43

What different ways are there to group patients in group-studies?

Answer 43

-Grouping by syndrome
-Grouping by behavioral symptoms
-Grouping by lesion location

Question 44

What are characteristics of grouping by syndrome and what is an example?

Answer 44

-Useful for investigating neural correlates of disease pathology
-Not useful for dissecting cognitive theory (inferences about building blocks of cognition)
-Example: lesion neuroanatomy of posterior cortical atrophy (PCA) in which patients were grouped by syndrome (PCA) to scan and assess at group levels which brain areas affected by atrophy

Question 45

What is posterior cortical atrophy (PCA)?

Answer 45

-Specific type of Alzheimer’s disease
-Dominated by perceptional problems rather than memory problems
-Degeneration of neurons mainly in posterior part of brain: occipital cortex, parietal cortex and bit in temporal cortex

Question 46

What are characteristics of grouping by behavioral symptoms and what is an example?

Answer 46

-Useful for identifying multiple regions implicated in behavior
-Example: lesion in neuroanatomy of set-switching accuracy in which comparing patients with and without deficits to find lesion distribution in patients with deficit, patients grouped by behavioral symptom (deficit vs no deficit)

Question 47

What are characteristics of grouping by lesion location and what is an example?

Answer 47

-Useful for testing predictions derived from functional imaging
-Example: contribution of parietal lobule to spatial attention in which patients were grouped by lesion location and found that patients with lesion surrounding temporal-parietal junction were impaired when stimuli occurred in contralesional visual field

Question 48

What are the independent variables and dependent measures for the different types of grouping?

Answer 48

-Grouping patients by syndrome or symptom (IV): looking at lesion location (DM)
-Grouping patients by lesion location (IV): looking at symptoms (DM)

Question 49

What are issues related to patient grouping?

Answer 49

-Some forms of brain damage make it hard to localize lesion
-Diaschisis: brain damage can induce functional lesions at distance (when regions function as network
-Dangerous to conclude that function is localized in region and that purpose of region is to support that function (neophrenology)
-Has to be considered whether region performs other functions or if other regions support this function

Question 50

What summary can you give about single- or group studies?

Answer 50

-Single case studies: important to determine what components of cognitive systems are
-Group studies of patients: important for establishing whether given region is critical for performing given task

Question 51

What are the advantages of using animal models in neuropsychology?

Answer 51

-Each animal can serve as its own control: before lesion compared to after lesion
-Possible to use groups of animals without lesion or groups of animals with lesion in different location

Question 52

What are disadvantages of animal models in neuropsychology?

Answer 52

-Not all cognitive functions can be studies in animals
-Not all cognitive functions can be studied at same level in animals

Question 53

What are the 4 causes of elicited brain damage often used in animal models in neuropsychology?

Answer 53

-Aspiration of brain regions by using suction device
-Transection: cutting discrete white matter bundles
-Neurochemical lesions: inserting toxins in neurons so they get killed
-Reversible lesions: pharmacological manipulations or colling to temporarily disrupt neural activity

Question 54

What can be a cause of virtual or temporary damage?

Answer 54

Transcranial magnetic stimulation (TMS)

Question 55

What is transcranial magnetic stimulation (TMS)?

Answer 55

-Results rather small and short
-Usage of coil with wire carrying electric current
–>Rapid change when current on, creating magnetic field
–>Magnetic field induces current in nearby neurons, causing them to generate action potentials
–>This disrupts cognitive function that neurons may be doing at that time
–>Measuring cognitive function by asking patients to perform task
-Not harmful, but some people excluded

Question 56

What are advantages of TMS in comparison to natural damage?

Answer 56

-No reorganization or compensation
-Can be used to determine timing of cognition
-Lesion is focal
-Lesion can be moved within same participant
-Can study functional integration

Question 57

What are advantages of natural damage in comparison to TMS?

Answer 57

-Subcortical lesions can be studied
-Lesions can be accurately localized with MRI
-Changes in behavior/cognition more apparent
-Clinical relevance is obvious

Question 58

Can you use brain stimulation to enhance brain function?

Answer 58

-Therapeutic effects of TMS and tES when repeated a lot
-Several promising areas of investigation: mood disorders non-responsive to other treatments, OCD, revalidation after stroke