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cognitive neuroscience > the lesioned brain > Flashcards

the lesioned brain Flashcards

1
Q

what is neuropsychology

A

Studying brain damaged patients – by studying abnormal, it is possible to gain insight
into normal function

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2
Q

classical neuropsychology

A

What functions are disrupted by damage to region X?

Addresses questions of functional specialization, converging evidence to functional imaging

Tends to use group study methods

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3
Q

cognitive neuropsychology

A

Can a particular function be spared/impaired relative to other
cognitive functions?

Addresses questions of what the building blocks of cognition are (irrespective of where they are)

Tends to use single case methodology

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4
Q

types of brain damage

A

Cerebrovascular accident (CVA or stroke)

Neurosurgery (split brain)

Viral infections (HSE, HIV)

Tumour (glioma)

Head injury (traffic accidents, rugby)

Neurodegenerative disease (Dementias: Alzheimer type)

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5
Q

ischaemic stroke

A

lack of glucose and oxygen supply

occlusion

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6
Q

haemorrhage

A

bleeding into brain tissue

blood vessel rupture

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7
Q

test of semantic memory

A

pyramids and palm trees

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8
Q

visuospatial testing

A

figure of ray

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9
Q

what can we neuropsychologically test?>

A

Intelligence

Memory

Visuospatial

Executive functions

Sensation

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10
Q

single dissociation

A

If a patient is impaired on a particular task (Task A), but relatively spared on another task
(Task B)

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11
Q

classical single dissociation

A

If patient performs within the normal range on the Task B, this has been termed as
classical single dissociation

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12
Q

strong single dissociation

A

If patient is impaired on both tasks, but is significantly more impaired on one task,
this is referred to as a strong single dissociation

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13
Q

patient CF

A

ischemic stroke to the left parietal area

At the time of examination he was completely speechless, but could communicate through gestures.

Wrote with his left hand (right hemiplegia)

When writing words he systematically omitted vowel only

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14
Q

kay and Hanley (1994)

A

reported another patient who made spelling errors selectively on consonants (e.g. “record” is spelled as recorg)

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15
Q

logic behind single dissociations

A

that a difficulty in one domain, relative to an absence in difficulty in another domain can be used to infer the independence of these domains

This difference could be relative, neuropsychologist test for a whole range of stimuli in order to make conclusions about the exclusivity of function

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16
Q

double dissociation

A

al work aims at showing that 2 or more tasks have different cognitive and neural resources

Double dissociation is derived from 2 (or
more) single cases with complementary
profiles

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17
Q

issues with single case studies

A

Lesion needs to be assessed for each patient, and no guarantee that
same anatomical lesions have same cognitive effect in different
patients

Therefore the cognitive profile of each patient needs to be assessed separately from other patients

Argument is not against testing more than one patient, but this becomes a series of single case studies and not necessarily a group
study
-shouldn’t average

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18
Q

grouping in lesion studies

A

group by syndrome
group by behavioural symptom
group by lesion location

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19
Q

group by syndrome

A

useful for investigating neural correlates of a disease pathology (e.g. Alzheimer’s) but not for dissecting cognitive theory

measure lesion location

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20
Q

group by behavioural symptom

A

Can potentially identify multiple regions
that are implicated in a behaviour

measure lesion location

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21
Q

group by lesion location

A

Useful for testing predictions derived from
functional imaging

measure behavioural symptoms

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22
Q

forms of space in the brain

A

Locations on sensory surfaces (e.g. the retina; retinocentric space)

Location of objects relative to the body (egocentric space)

Location of objects relative to each other (allocentric space)

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23
Q

how do we locate things in space?

A

cross modal

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24
Q

egocentric space

A

Location of objects relative to the body

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25
Q

allocentric space

A

Location of objects relative to each other

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26
Q

attention

A

Attention is the process by which certain information is selected for further processing
and other information is discarded

Limited capacity to process all received information, so selection based on relevance or importance to current goals

Attention tends to be directed to locations in space (space is a common dimension of different sensory systems
and our motor system) – spotlight metaphor

Attention may be needed to bind together different aspects of conscious perception (e.g. shape and colour,
sound and vision)

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27
Q

spotlight metaphor as attention

A

Spotlight may move from one location to another (e.g. in visual search)

It may zoom in or out (narrow or wide “beam”), e.g. if attending to words or
attending to central letter in a word

Limited capacity: not everything is illuminated

28
Q

location of attention and eye fixation

A

Location of attention not necessarily same as eye fixation (“looking out corner of
one’s eyes”) – however, there is a natural tendency for attention and eye-fixations
to go together

29
Q

control of attention

A

exogenous
inhibition of return

30
Q

exogenous control

A

externally guided by a stimulus

31
Q

inhibition of return

A

slowing of speed of processing when going back to previously attended location

32
Q

Visual search

A

scanning the environment to find something you are looking for

33
Q

feature integration theory (FIT)

A

Perceptual features (e.g. colour, line orientations) are encoded in parallel and prior to attention

If an object has a unique perceptual feature then it may be detected without the need for attention – “pop-out” (left array)

If an object shares features with other objects (right array) then it cannot be detected from a single perceptual feature and attention is needed to search all candidates serially

“Pop-out” is not affected by number of
items to be searched

34
Q

space and attention neural correlates

A

Parietal lobes (ventral) specialized for spatial processing and have been called the “where” route
(Ungerleider & Mishkin)

Parietal lobes (dorsal) also bring together different types of spatial representation that are needed for action (e.g. integrating visual space with body space) so also called the “how” route

35
Q

two main attention related networks

A
  1. a dorso-dorsal network (blue) involving lateral intraparietal area (LIP) and Frontal eye fields (FEF).
  2. ventro-dorsal stream (right tempo-parietal junction and ventral frontal cortex)
    that interrupts any cognitive task in order to divert attention away from processing
36
Q

dorso-dorsal network

A

FEF
LIP

37
Q

vernto-dorsal attention stream

A

right tempo-parietal junction
ventral frontal cortex

38
Q

right parietal lobe and space

A

Right parietal lobe contains richer representation of space (left space and
some right space)

39
Q

left parietal lobe and space

A

Left parietal lobe contains an impoverished representation of space
(predominantly of right side only)

40
Q

pseudoneglect

A

The greater spatial specialization of right parietal lobe means that we all have
a tendency to attend to left side of space (pseudoneglect)

41
Q

synonyms neglect

A

unilateral neglect, spatial neglect, or hemispatial neglect

42
Q

what is neglect?

A

Patients fail to attend to stimuli on the opposite side of space to their lesion
(a right sided lesion would affect the left side of the space)

43
Q

what is neglect caused by?

A

Neglect is most prominent following stroke to the right hemisphere of the human brain

Neglect could arise from different mechanisms:
* loss of neurons dedicated for representation of that space
* a failure to shift attention to that side
* some combination of the two

44
Q

neuroanatomy of neglect

A

The lesion is in parietal association cortex – integration of multiple sensory signals and extensive connections with frontal areas

45
Q

what does lesion site of neglect overlap with?

A

right angular gyrus

46
Q

clinical picture of neglect

A

Individuals with neglect do not suffer from any primary disorder of perception,
sensation or movement

Most commonly observed in the visual modality – visual neglect

Multimodal neglect reported: auditory and somatosensory (tactile)

Left parietal lesions can result in neglect – less severe and faster recovery

47
Q

clinical tests of neglect

A

line bisection

cancellation tasks (albert’s lines, star cancellation)

copy a drawing
draw from memory

48
Q

different types of neglect

A

perceptual vs representational neglect

neglect for near vs far space

personal vis peripersonal spcae

within object vs between object

spatial vs object based

49
Q

representational vs perceptual neglect

A

Neglect can affect memories of scenes

The brain contains different references for spatial and imagined events in external space.
Perception and imagery can dissociate at higher levels of visual processing

in both cases the information on the left side is compromised (RH damage)

50
Q

Piazza del duomo experiment

A

Two patients (IG, 86 and N.V., 72 with large right parietal lesions) were asked to
describe a familiar place, the Piazza del Duomo in Milan, according to different perspectives.

First (a), they were asked to imagine themselves
looking at the front of the cathedral from the opposite side of the square; then
the reverse perspective.

Double dissociation between perceptual (line bisection) and representational neglect suggests different spatial reference frames for external versus imagined (mind’s eye) space. Also – spatial knowledge not lost, but unavailable to report

51
Q

neglect for near vs far space

A

Double dissociation between near space: line bisection using pen and paper – IMPAIRED
(Halligan and Marshal, 1991) and far space = SPARED when tested with a light pointer
(Vuilleumier et al., 1998)

52
Q

personal vs peripersonal space

A

Double dissociation between personal (bodily) space and near space

Body neglect = failure to groom left of body, notice position of limbs, or feel pain in the left limbs
vs
Near space neglect = visual search of
array of external objects

53
Q

within objects vs between objects

A

Some neglect patients attend to objects on the left side of space but omit to attend to one
half of the object itself (object-based neglect) - STG

Forms a double dissociation with space-based neglect - AG

54
Q

spatial vs object based neglect

A

Axis-based neglect Driver and Halligan (1991) – patient with object neglect cannot detect differences on left side of an object even when falling into right side of space

55
Q

Neglect as a Disorder of Attention and Not
Low-Level Perception

A

Neglect patients still activate visual regions in occipital lobes for the information that they claim not to be aware of

They are often able to detect objects on the left if cued there

Affects auditory and tactile judgments as well as vision (e.g. sounds on left are mislocalized but still heard)

Phenomenon of visual extinction suggests different perceptual representations are competing for attention (and visual awareness)

56
Q

neglect and extinction

A

When two stimuli (targets) presented simultaneously to the left and right of the
patient’s midline – left target typically extinguished

57
Q

what happens to neglected information?

A

neglected information implicitly coded

58
Q

rehabilitation of neglect: adaption

A

involves patients wearing prism lens glasses that shift their view to the right

When asked to point at objects, they make errors by missing to the right. However, visual
feedback allows them to compensate for the errors and correct towards the left

the deviation to the left persists
after the prism lenses are removed and this can produce a relatively long lasting
improvement in symptoms

59
Q

video games, shaping attention and learning

A

Studied the effects of video games on perceptual and motor skills

Perceptual learning tends to be specific with a trained task

Action video game playing is capable of altering a range of visual skills

60
Q

brain game

A

when searching for a particular objects in a sea of shapes, people who played video games regularly showed less activation of the brain regions linked to attention

brains performing the tasks more efficiently

61
Q

The tests of variable association (TOVA)

A

TOVA assesses impulsivity and sustained attention. In this test, participants are required to
press a key as fast as possible in response to a target and to withhold responding to non-target stimuli

In one condition, the targets are rare and the nontargets appear frequently. The extent
to which participants are able to stay on task and respond quickly to rare targets is a
measure of sustained attention.

In a different set of trials, targets appeared frequently, whereas nontargets were rare.
The extent to which participants are able to withhold responding to nontargets is a
measure of impulsivity.

62
Q

TOVA to assess impulsivity and sustained attention in young adults who
were either non-video game players (NVGP) of habitual video game players (VGP)

A

Their results show that VGPs were overall faster than NVGPs in both the sustained attention and
the impulsivity condition. This increased speed did not come at the expense of accuracy as both

groups did not differ on this measure, indicating overall enhanced attentional control in VGPs

63
Q

cognitive control

A

set of neural processes that allow us to
interact with our complex environment in a goal-direct manner

64
Q

multitasking

A

attempt to accomplish simultaneous goals

65
Q

EEG and multi-tasking training

A

After NeuroRacer training EEG pattern resembled those of 20-year-olds. The key change was in prefrontal cortex – suggesting improvement in
executive functions

Measures of coherence were much better
– how well different brain areas
communicate with each other

66
Q

TDCS and Multitasking

A

The dorsolateral prefrontal cortex (DLPFC) has been proposed to play an important
role in neural processes that underlie multitasking performance

Anodal tDCS or sham tDCS at 1.0 mA was applied over left DLPFC in healthy young adults
immediately before they engaged in a 3-D video game designed to
assess multitasking performance

The anodal group showed enhanced multitasking performance and decreased
multitasking cost during the second session , suggesting delayed cognitive benefits of tDCS.

Performance benefits were
observed only for multitasking
and not on a single-task version
of the game

First evidence of how custom designed
video games can be used to assess and
enhance cognitive abilities across the
lifespan.

66
Q

TDCS and Multitasking

A

The dorsolateral prefrontal cortex (DLPFC) has been proposed to play an important
role in neural processes that underlie multitasking performance

Anodal tDCS or sham tDCS at 1.0 mA was applied over left DLPFC in healthy young adults
immediately before they engaged in a 3-D video game designed to
assess multitasking performance

The anodal group showed enhanced multitasking performance and decreased
multitasking cost during the second session , suggesting delayed cognitive benefits of tDCS.

Performance benefits were
observed only for multitasking
and not on a single-task version
of the game

cognitive neuroscience (3 decks)

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