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Psych3227A > Chp 5: Disconnection Syndromes > Flashcards

Chp 5: Disconnection Syndromes Flashcards

1
Q

Association fibres

A

Axon fibres connect one lobe of the brain to another, to one part of a lobe to another part

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2
Q

Commissural fibres

A

Axon fibres connect one hemisphere of the brain to the other

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3
Q

Cerebral white matter - 3 types of fibres

A
  • Association
  • Commissural
  • Projection
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4
Q

Projection Fibres

A

cross over and are contralaterally processed

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5
Q

Corpus Callosum Connections (3)

A
  1. Projections are topographical
    - Homotopic:
    A on one side connects with A on the other side
  2. Connects projections areas contralaterally
    - Heterotopic :
    A send to B on the left, also to the B on the Right
  3. Diffuse terminal projections
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6
Q

Portrait: At Cross Purposes -D.M.

A

-D.M.
-Director of large psychiatric hospital
- Developed symptoms:
- Headaches, memory problems

Cyst in the 3rd ventricle
◦ Cyst drained to relieve pressure causing symptoms
◦ Cannula inserted through dorsal surface of the brain through corpus callosum and part of brainstem

D.M. showed good recovery
◦ No headaches, memory problems improved
-After removal, his hands did not work together properly in some situations
- Surgeons accidentally cut the corpus callosum linking his two hands

Bilateral

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7
Q

Partial callostomy - Patient MC (Senses in hands)

A

Absence of callosal transfer of tactile information after posterior callosum was severed

Before surgery
- When left hand is touched, both hemispheres know what happen to the left hand

After surgery (cut anterior of corpus callosum)
- No tactile information transferred to other side of the brain

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8
Q

John Downer’s Experiment

A

◦ Observing what happens when information is prevented from travelling freely through brain

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9
Q

Disconnections

A

Cutting of cerebral connections

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10
Q

Disconnection syndromes

A

◦ Behavioral effects of disconnections

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11
Q

Apraxia

A

is a neurological disorder characterized by the inability to perform learned (familiar) movements on command, even though the command is understood and there is a willingness to perform the movement.

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12
Q

Behavioral Effects of Disconnection
Hugo Liepmann (1900)
◦ Theory of apraxia

A

in absence of weakness or incoordination that would normally be observed following lesion to right motor cortex

“move your left hand”
Verbal command:
- Understood in left hemisphere
Motor:
- Corpus callosum communicate to the right hem to move the left side of the body
severed: fail to move the left hand

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13
Q

Commissurotomy; and what is it usually for?

A

Separation of the hemispheres
- sectioning/ cutting through all of the commissure, not only corpus callosum, anterior/posterior commissures
- Fibers cut as a therapy for epilepsy
- Each hemisphere has its own sensations, perceptions, thoughts, and memories

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14
Q

Disconnecting Sensorimotor Systems: Olfaction

A

◦ Not crossed (ipsilateral)
◦ Severing the anterior commissure leads to an inability of the right nostril to name odors, but can pick the odors out with the left hand
◦ Anosmic: Inability to smell

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15
Q

Anosmic

A

Inability to smell

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16
Q

What do those 6 layers of neocortex do for us? (5)

A
  • Extends usefulness of all behaviours
  • Allows for finer sensory discernment
  • Allows for finer motor control/dexterity
  • Makes behaviours more adaptable
  • Consider future needs
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17
Q

Intermanual conflict

A
  • antagonizing movements of the two hands
  • mostly due to the disconnection between the two cerebral hemispheres
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18
Q

Callosotomy

A

just the sever of the corpus callosum

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19
Q

Speaking Versus Nonspeaking Hemispheres (with visual stimuli presented on left and right sides of visual fields)

A

The split-brain patient reports through the speaking hemisphere only the items flashed to the right half of the screen and denies seeing left-field stimuli or recognizing objects presented to the left hand. Nevertheless, the left hand correctly retrieves objects presented in the left visual field, about which the patient verbally denies knowing anything.

Verbally report the word presented to the right visual field

Yet the left hand can act according to the word presented to the left visual field

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20
Q

The Interpreter

A

The unique specialization of the left hemisphere

our ability to make causal interpretations about the world around us

split-brain patient P.S.
eg. The left hemisphere of split-brain patient P.S. was shown a chicken claw, and his right hemisphere was shown a snow scene. When P.S. was asked to point to a picture associated with the image he had just seen, his right hand (guided by his left hemisphere) pointed to the chicken, and his left hand pointed to the shovel. When asked why he had pointed to those things, he replied, “Oh, that’s simple. The chicken claw goes with the chicken, and you need a shovel to clean out the chicken shed.”

21
Q

Disconnecting Sensorimotor Systems: Vision

A

Vision
◦ Crossed
◦ Visual stimuli in the right visual field travels to the left hemisphere
◦ Visual stimuli in the left visual field travels to the right hemisphere
◦ After commissurotomy, information is not shared

22
Q

Dominance of visuospatial abilities in right hemisphere in drawing task, which hand will draw better?

A

For tasks, left hand will draw better because of access to right hemisphere expertise in this area

23
Q

Disconnecting Sensorimotor Systems: Somesthesis

A

Crossed
◦ Sensations in the left hand travel to the right hemisphere
◦ Sensations in the right hand travel to the left hemisphere
◦ Somatosensory functions become independent after commissurotomy

24
Q

Disconnecting Sensorimotor Systems: Movement

A

Movement
◦ Crossed connections
◦ Severity of deficits after disconnection declines over time
◦ inter manual conflict appears in complete split brains

25
Q

Corpus Callosum Anatomy

A

◦ GENU - Connect to prefrontal Cortex
◦ BODY - Premotor, motor, somatosensory,
posterior parietal cortex
◦ SPLENIUM - Superior temporal, inferior
temporal, visual cortex
- Individual differences in size

26
Q

Corpus Callosum Abnormalities in Psychopathic Antisocial Individuals

A

Findings:
1. Corpus callosum was bigger in psychopathic participants
2. Might reflect atypical neurodevelopmental processes involving an arrest of early axonal pruning or increased white matter myelination (bad pruning)

27
Q

The corpus callosum of Albert Einstein’s Brain

A
  • Albert’s brain was also bigger
  • Connectivity between the two hemispheres was enhanced
28
Q

Callosal Agenesis (ACC)

A
  • Corpus callosum is partially or completely absent.
  • Neuropsychological deficits
  • Variability – 5 in 1000 have callosal agenesis
  • Deficits in memory, language, visuospatial issues
  • Also display neuroplasticity

Fear, disgust and surprised is hardest emos to read in the faces

Probst fibre bundles : with no connection of the corpus callosum, the fibres turn an outward 90 degrees and to the outer areas, dunno what they do

Unique in callosal agenesis

29
Q

Portrait: Lingering Effects
of Brain Trauma
- CASE STUDY - R.L.

A

◦ 32 year old nurse, mother of 4
◦ Sustained whiplash in a car accident
◦ Head struck back headrest and the side
window
◦ Blacked out for a few minutes
◦ When emergency vehicles arrived
- she was conscious, although disoriented and Dysphasic (impaired speech)
- Severe pain in back and neck
◦ Week spent in hospital

◦ Neither CT nor MRI revealed damage
- Although several vertebrae were damaged

  • She was an accomplished musician
    ◦ Could still play well from memory, but could no longer read music
    ◦ Oral language skills remained impaired and was not able to read
    ◦ Also showed apraxia (inability to make voluntary movements in absence of paralysis or other motor or sensory impairment – especially an inability to make proper use of an object)
30
Q

Dysphasic

A

impaired speech

31
Q

Apraxia

A

inability to make voluntary movements in absence of paralysis or other motor or sensory impairment – especially an inability to make proper use of an object

32
Q

Contrecoup injury

A
  • injuries affect the side of the brain opposite from where the impact occurred.
  • They are often overlooked or misdiagnosed because of their location.

-> When there is a strong force on the back, impact zone- coup (initial impact)
-> transfers from back motion to the front of the skull (contrecoup injury)

33
Q

Portrait: Lingering Effects
of Brain Trauma
- CASE STUDY - R.L.

A

◦ Seen by Kolb & Whishaw
◦ Depressed – neurologists could no reason for impairment
◦ Testing featuring the Wisconsin Card Sorting Test
◦ She was eventually able to perform the WCST, but with difficulty
◦ Neuropsychological evaluation by Kolb & Whishaw revealed
– Above-average intelligence
– Significant loss of verbal fluency
– Severe dyslexia
◦ 10 year follow-up
– Still unable to read music
– Ability to read text only with great difficulty

34
Q

Wisconsin Card Sorting Test

A
  • Tests response inhibition
  • Patients with frontal lobe lesions will perseverate on responses
  • Sort by color, number of elements or shape
  • After 10 correct selections are made the sorting criteria changes
  • Switching to a new strategy proves to be difficult for those with frontal lobe damage
  • Only tell them that there is a change, so they have to find the sorting strategy only by the experimenter saying yes or no
35
Q

Stroop Task

A

Name ink colour
- measure a person’s selective attention capacity and skills, processing speed, and alongside other tests to evaluate overall executive processing abilities.

36
Q

Chicago Word Fluency Test/ Thurstone Word Fluency Test

A

Subjects are required to write as many different words beginning with S as possible in 5 minutes and, after this, as many singular four-letter words beginning with C as possible in 4 minutes.
-
used as one of the measures of brain’s frontal lobe function
- damage: tend to rule break, shaky

37
Q

The Changing Face of Neuropsychological Assessment
Goal of first tests and what modern assessment is influenced by

A

First tests:
◦ Goal was to establish a cutoff between brain damaged and non-brain damaged

Modern Assessment influenced by:
◦ Functional Imaging
◦ Cognitive Neuroscience
◦ Managed Health Care

38
Q

Use of Functional Imaging (3)

A
  • Investigators can identify changes in cerebral processing via images instead of looking for behavioral symptoms
  • Patients now referred for rehabilitation or general cognitive functioning
    Diagnostician -> Participant in rehabilitation, Documenting the
    nature and extent of disability.
  • Functional imaging does not predict the extent of behavioral disturbances
39
Q

Cognitive Neuroscience History

A

— 1950s–1980s
◦ Development of test batteries
– Still use cutoff scores

— 1990s
◦ cognitive theory and structural and functional imaging were used to understand how the brain works

40
Q

Managed Care, and what clinical assessments should do

A
  • Managed care produces pressure to reduce time and money
  • Clinical Assessment Should:
    ◦ Focus on matters linked to treatment
    ◦ Reduce costs
    ◦ Be time efficient
    ◦ Monitor progress and outcome evaluation
41
Q

Goals of Neuropsychological Assessment (6)

A
  1. Make an assessment of patient’s cognitive capacity
  2. Facilitate patient care
    ◦ Assessment can provide info about likely rate of recovery & potential for resuming former lifestyle
  3. Identify mild disturbances
    ◦ Especially where other diagnostic studies have
    produced ambiguous results
  4. Identify the cause of disorders
    ◦ Example – providing additional diagnostic information such as in the case of epilepsy
  5. Rehabilitation
    ◦ Documenting patient progress, assessing the
    effectiveness of various treatments
  6. Help the patient and their family understand the disorder
    ◦ Understanding/appreciating potential deficits, better planning possibilities for families
42
Q

Intelligence Testing in Neuropsychological Assessment : WAIS (Wechsler Adult Intelligence Scale)

A

Subscales for verbal ability and performance

  • Verbal score:
    measure of acquired knowledge, verbal reasoning and comprehension of verbal information
  • Performance score:
    indication of a person’s nonverbal reasoning, spatial-processing skills, attentiveness to detail and visuomotor integration

◦ Can be useful as a rough measure of right- and left hemisphere functioning

  • Low verbal score: potential problem in the left hem

Problems: Pre-injury intelligence is often not known

◦ Estimate usually made informally using a patient’s education, occupation, and socioeconomic background

43
Q

The Problem of Effort, test of effort

A

-Malingering
◦ Exaggerating cognitive deficits
-External incentives play a role in
performance

Forced Choice Digit Memory Test by Merielle Hiscock
Most sensitive malingering test (test of effort)

44
Q

Forced Choice Digit Memory Test by Merielle Hiscock

A

Most sensitive malingering test (test of effort)
- Jeanette McGlone, at Dalhousie, has shown even severely amnesic patients usually score nearly perfect
- Fakers score as low as chance
- A cutoff of no lower than 90% is used

45
Q

Malingering

A

Exaggerating cognitive deficits

46
Q

Contralateral neglect

A
  • A condition in which a person appears to ignore objects, people, and sometimes their own body on one side of their center of gaze
  • ## Most common following right hemisphere damage (posterior parietal cortex)eye tracking study: ppl with spatial neglect cannot engage with the a side of visual field (most usually left), When a patient suffers from a stroke on one side of the hemisphere, there would be a neglect to contralesional space. If the stroke is on the right, the patient will be unable to attend to the left visual field.
47
Q

What type of people would fail the clock drawing test?

A

Alzheimers
Dementia
Stroke

Susannah:
Contralateral Neglect

48
Q

Why are there more left neglect than right neglect? theory:

A

Theory:

Maybe the left hemisphere is also specialised for spatial processing and therefore takes up info about ipsilateral and contralateral space, and therefore takes over more

suggests that the right parietal lobe attends to space on both sides of the body, while the left side only attends to the right

49
Q

Is Contralateral Neglect is more of a disconnection syndrome?

A

Using DTI: they have destruction of white matter

Psych3227A (11 decks)

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