1 - DISCONNECTION SYNDROMES Flashcards
Small world model
SMALL WORLD MODEL
- SWM : described by Watts & Strogatz in 1998 as “network presenting high local cluster coefficient
& low minimal path length between any pair of nodes”
- With development of network being related to general decrease in short-range with simultaneous
increase in long-range connections
Difference network vs circuitry
Network vs circuitry
Circuitry = more detailed, more complex ideas of brain network
Network = more general and less precise
Definition node
Nodes = peripheral connection point inside network
Definition module
Modules = nodes with larger connectivity degree
Hubs:
- definition
- if damage: …
Hubs = modules that connect to other modules, as also other clusters entirely
Damaging hub => able to process & understand process but not able to do it (know how to draw a tree because know how a tree looks like and know use pen but unable to draw it)
Description défaut mode network
Everything that happens without activity, any action required (analyze, plan…)
Don’t take primary area, only secondary
psPC, piPC, PRECUN, CUN, V2, V3 = spatial / visual orientation
HPC = memory, but anythin without AM = emotion
aINS, pINS, TP = perception with emotional point of view => body sensation
dlPFC = motor strategy, behavioral strategy // OFC = attitude, believes & gathering of principles & identity
aCC, pCC, mCC = lot of info from different nodes = HUBS
Imbalance in amygdala (AM) => increased in AM, decreased in aCC => loss of focus due to emotional thinking
= resting or task-negative network of stimulus independent thought relating to all internal cognitive processes, happening in absence of immediate stimulation that will promote increased in brain activity
→ Strength of functional coupling within DMN modules during working memory tasks, correlates positively with performance where cognitive load seems to modulate degree of task induced deactivation, indicating monitoring value
Frontoparietal network description
= network responsible for modulating behavioral responses & creating context for analysis interpretation, that will directly guide decisions & interaction with environment & others
Red = FPN
Black = DMN
mPFC = work as “hub” => decision making, social behavior
Salience network description
= gathering & interpretation of external stimuli, as body sensations (internal), leading to reactions & adaptations to sensory experiences
- Adaptations can influence perception & cognition, directly impacting planning & decision-making processes
Apraxia:
- def
- not explain by
- General symptoms
Disorder of skilled movements, not explainable by:
- Muscle weakness
- Akinesia or other dyskinetic disorders
- Abnormal tone / posture
- Intellectual or communication deficits
- Unwillingness to cooperate
This doesn’t mean that dyspraxia patient will not present some of these symptoms,especially in cases of severe brain damage, only that loss of specific motor abilities cannot be traced back to it
General symptoms
- Most cases: left brain damage (LBD)
- Aphasia often observed
- Disturbance of skill movements can involve:
o Imitation
o Gesticulation (communication)
o Tool-use
o Sequential movements (ADLs)
Liepmann model:
- description
- 2 phases
LIEPMANN MODEL (1908)
- Classification model for higher level motor disorders
- Describes dyspraxia as disturbance on 1 of 2 phases
Phase 1: creation of mental image of movement in space, considering body proportions & sensations
Ideational dyspraxia
Phase 2: transduction of tibia of movement into appropriate mechanical commands
Ideokinetic (ideomotor) dyspraxia
CALLOSAL MODEL vs LDV GESCHWIND’S MODEL
Callosal model suggests that brain lateralization influenced by development & dominance of corpus callosum, which inhibits or facilitates certain functions between hemispheres
LDV Geschwind’s model proposed that lateralization arises from early developmental factors, such as role of testosterone affecting brain asymmetry & connectivity, especially in language areas
DMN: IDEOMOTOR & IDEATIONAL DEFICITS:
- damage of aDMN
- damage of pDMN
Damage to this portion of aDMN, located mostly on LBH
Difficulty translating mental image into intended motor
action
Damage to this portion of pDMN, located mostly on LBH
Difficulty constructing mental image to follow while performing
intended motor action
Different types of dyspraxia & def of each
- Ideomotor = deficit in pantomime of tool use & meaningless gestures, without loss of knowledge
of task - Ideational = deficit in tool use & sequential tasks
- Limb-kinetic = manipulative deficit, like loss of dexterity on contra-lateral limb
- Conceptual = knowledge deficit about selection of tools & objects for task
- Dissociative = deficit in following verbal commands only
- Conduction = deficit on gesture imitation only (subtype of other dyspraxia)
Conceptual description
Conceptual
- Little to no damage to lexical semantics & object recognition
- Connection between tool & action semantics damage
- Issues with conceptualization of already known motor plan, related to choice
of tool in specific context
Apraxia of speech description
Apraxia of speech
- Even though definition of apraxia of speech & aphasia overlaps some points, 2 terms describe 2 different conditions
- Apraxia of speech & aphasia can occur simultaneously
- Apraxia patient might have difficulties with communication only due to inability to mimic mouth / tongue movements to pronounce words
- Also applies for dysarthrophonia, still apraxia patient will be able to control respiration during speech, without intonation issues
Apraxia = inability to perform purposive actions, as result of brain damage
Aphasia = impairment of language, affecting production & comprehension of speech. Also affect ability to read or write
Dysarthrophonia = disorder of voice & speech typically associated with PD’s (pronunciation, phonation & articulation)
Description of evaluation of dyspraxia + ≠ types
EVALUATION
Dyspraxia patients might have difficulty producing adequate movements not only on contralesionally body hemisphere, but also on ipsi-lesional. In 1st approach for examination of disorder, 3 main domains of action evaluated:
- Imitation of gestures
- Communicative gestures
- Tool & object use
Imitation of meaningless gestures
Imitation of meaningless gestures
- Sign of deficit in translation of mental images into gestures
- Explores connection between perception of gesture & its immediate execution
- Consider unknown nature of imitated gestures
Expression of communicative gestures
Expression of communicative gestures
- Asymbolia often described as clumsiness of communicative gestures
- Described degradation in execution of communicative gestures
- Previously described as exclusive symptom of aphasia, since many aphasic patients present in
difficulty, asymbolia was incorporated in definition of apraxia symptoms for its close relation of time-space motor representation deficit
Pantomime of tool-use
Individual demonstrated how to use tool without holding in hands
Tool-use
Image
Tests sets
Tests sets
- Use of actual tools (transitive movements) → technical reasoning
- Novel tool test →mechanical reasoning
Overview of assessment depending on different types of dyspraxia
Table
Reconnecting:
- definition
- different types
Evidence-based practice
- All approaches seen in literature have low influence on functional outcomes
- Most approaches based on bottom-up strategies, aiming conditioning
- Issue with complexity of transhemispheric network development & restauration
→ Strategy training
→ Sensory stimulation
→ Cueing
→ Chaining
Strategy training
Strategy training
- Use of compensatory mechanisms to facilitate ADL
- Based on internal or external process:
o Mentally describing action
o Making use of assistive technology
Sensory stimulation
Sensory stimulation
Applying direct or indirect augmented sensory input:
- Applying pressure
- Utilizing different surface stimulation
- Weight bearing during exercise
Visual, somatosensory, auditory …High to low system
Chaining
Chaining
Rehabilitation technique using step-by-step linking of simple tasks to re-establish communication
between disconnected brain regions, compensating for lost connections in disconnection syndromes
Breaking down any task in at less 5 steps
Cueing
Cueing
Using verbal or tactile prompts to guide & improve. Patient’s motor performance or cognitive function.
Help identify & address issues like impaired coordination, delayed response or disorganized movement
pattern. Evaluating patient’s ability to respond to external stimuli & integrate sensory or motor functions.
Other approaches of reconnecting
Other approaches
- Transcranial direct current stimulation (tDCS)
- Single or repetitive transcranial magnetic stimulation (TMS) as excitatory or inhibitory stimulation
- Paired associative stimulation (PAS)
- Theta burst stimulation (TBS): shorter stimulation period
