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PSYC31: Ch8

17 Pages
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Department
Psychology
Course Code
PSYC31H3
Professor
Konstantine Zakzanis

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PSYC31- Chapter 8
Diffuse and Focal Effects
- concepts more clear cut than manifestations
Diffuse EffectsFocal Effects
- behavioral expression
memory, attention, concentration disabilities
impaired higher level and complex reasoning-
conceptual concretism, inflexibility
response slowing
- emotional flattening or lability (constantly undergoing
change)
- these symptoms most severe immediately after injury or
early stages of sudden onset disease OR first appear as
subtle transient problems that increase in duration and
severity as condition worsens
- symptoms almost always accompany focal lesions of
sudden onset
- i.e. cloudy consciousness, confusion, slowed
responsiveness may obscure focal residual effects
evidence focal injury wont known until later
- ultimately, diffuse effects resulting from increased
intracranial pressure and circulatory changes may
obliterate specific defects due to local tissue damage
-
- cause most: trauma, space displacing lesions (i.e. tumors,
blood vessel malformations), localized infections,
cerebrovascular accidents
- systemic conditions too – severe thiamine deficiency
- occasionally accompany acute exacerbation of systemic
disorderi.e. diabetes confusing the diagnostic picture
until underlying disorder brought under control and organic
symptoms subside
- distinguished by lateralizing signs since most discrete
lesions involve only one hemisphere
- when both hemispheres, damage apt to be assymetrical
predominance of lateralized symptom pattern
- generally when one function or several are significantly
impaired while others remain intactexaminer can
conclude focal injury
Site and Size of Focal Lesions
- site of lesion determine many characteristics of attendant behavioral alterations
- expression of changes – severity, intransigency, burdensomeness – depends on other variables that just the
location of lesion makes prediction of symptoms virtually impossible
- localizing lesion and localizing function not identical operations
- certain areas of brain may be critical for specific cognitive functions but brain regions not isolated – work
interconnected, distributed neural networks
- evidence by neuroimaging
- lesions in one area may disrupt network and produce impairment similar to lesions in another area within
network
- each area contirbtue to some aspect of cognitive processing
www.notesolution.com
- clinical practice, few patients iwht primary focal lesions have damage confined to the identified area
- stroke patients – lesion site more likely to predict nature of NP deficits than its size/ volume
- i.e. small subcrotical lesions can have major effects
- complexity of site vs. size site more important determing language behavior while lesions size may be a
factor in severity of articulatory impairment
- while others believe both size and site contribute to severity of dysfunction
- CT measures of stroke: severity estimated best by taking into account both size and hemisphere of lesion
- TBI’s rarelyclean” (except for missile, puncture wounds) – size of lesion impt determinant of residual
functional capacity
- tumors widespread throughout brains boundaries – erratic in destruction of nervous tissue
- location of lesion only partial description of primary site of damage
- patterns behavior and NP test results may not meet cookbook expectations of lesion
Depth of Lesion
- subcortical damage – added effects of disrupted pathways or damaged lower integration centers
- depth and extent of cortical lesion involving subcortical damage – alter behavioral correlates of similar cortical
lesions
- depth of lesion = related to severity of impairment of verbal skills
- i.e. anosognosia – impaired awareness of ones own disabilities or disabled body parts, associated with right
parietal lobe damage illustrate differences in behavioral correlates of similarily situated cortical lesiosn with
different amounts subcortical involvement
- lesions of right optic region of thalamus = anosognosia with neglect of paralyzed side
- lesions penetrating only transmission fibers from thalamus – parietal cortex = anosognosia with
amnesia or lack of recognition of affected limbs or side
- lesions to parietal cortex = anosognosia with “positive” psych symptoms – confabulation, delusions
Distance effects
Diaschisis: chronic depression of activity that place in areas of brain outside immediate site of damage – usually
associated with acute focal brain lesiosn
- originally thought of shock to nervous system due to disruptions in neural network
www.notesolution.com
- include depression of relatively discrete or circumscribed clusters of related functions than global dampening
of cerebral activity
- typically viewed as transient, then dissipates allows depressed functions to improve spontaenosuly
- may also account for appearnance of permanent changes in functions not directly associated with lesion site
- i.e. stroke patients exhibited deficits associated with noninfarcted hemisphere – i.e. from reduced blood flow
- recovery in young stroke patients whereas elderly likely experience persisting diaschisis effects
Disconnection syndromes:
- similar to diaschisis – both show up as depression or loss of function primarily served by an area of brain that
is intact and at some distance from lesion
- both involve disrupted neural transmission through subcortical white matter
- diaschisis: cortical lesions that may/ may not extend to white matter
- disconnection syndromes: damage to white matter that cuts cortical pathways disconnecting one or another
cortical area from communication network of brain
- simulate effects of cortical lesion orproduce atypical symptom pattern
- even small subcortical lesion result in significant behavioral changes if interrupts critical pathway btw cortexes
– thus, cortical lesion not necessary for that cortex to be nonfunctional
- most dramatic DS: interhemispheric connections severed – surgery, disease
- damage in given area have secondary adverse effects on activity of distant but normally interacting areas
Nature of Lesion
Type of Damage
- clean loss of cortical tissue as result of surgery or missile wounds – functions specifically mediated by lost
tissue no longer performed
- when white matter removed, some discconection effects may occur
- when lesion involves tissie removal with little to no diseased tissue remaining – impact on other unrelated
functions minimal and potential for rehab is high
- dead or diseased brain tissue = behavioral distortions involving other functions, high level cognitive
reprocussions, personality benefits in removal (memory improvements)
- diseased/ dead tissue also affect circulation and metabolism surroudnign tissue – secondary effects; build up
www.notesolution.com

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Description
PSYC31- Chapter 8 Diffuse and Focal Effects - concepts more clear cut than manifestations Diffuse Effects Focal Effects - behavioral expression - cause most: trauma, space displacing lesions (i.e. tumors, memory, attention, concentration disabilities blood vessel malformations), localized infections, impaired higher level and complex reasoning- cerebrovascular accidents conceptual concretism, inflexibility - systemic conditions too severe thiamine deficiency - occasionally accompany acute exacerbation of systemic response slowing - emotional flattening or lability (constantly undergoing disorder i.e. diabetes confusing the diagnostic picture change) until underlying disorder brought under control and organic - these symptoms most severe immediately after injury or symptoms subside early stages of sudden onset disease OR first appear as - distinguished by lateralizing signs since most discrete lesions involve only one hemisphere subtle transient problems that increase in duration and severity as condition worsens - when both hemispheres, damage apt to be assymetrical - symptoms almost always accompany focal lesions of predominance of lateralized symptom pattern sudden onset - generally when one function or several are significantly - i.e. cloudy consciousness, confusion, slowed impaired while others remain intact examiner can responsiveness may obscure focal residual effects conclude focal injury evidence focal injury wont known until later - ultimately, diffuse effects resulting from increased intracranial pressure and circulatory changes may obliterate specific defects due to local tissue damage - Site and Size of Focal Lesions - site of lesion determine many characteristics of attendant behavioral alterations - expression of changes severity, intransigency, burdensomeness depends on other variables that just the location of lesion makes prediction of symptoms virtually impossible - localizing lesion and localizing function not identical operations - certain areas of brain may be critical for specific cognitive functions but brain regions not isolated work interconnected, distributed neural networks - evidence by neuroimaging - lesions in one area may disrupt network and produce impairment similar to lesions in another area within network - each area contirbtue to some aspect of cognitive processing www.notesolution.com- clinical practice, few patients iwht primary focal lesions have damage confined to the identified area - stroke patients lesion site more likely to predict nature of NP deficits than its size volume - i.e. small subcrotical lesions can have major effects - complexity of site vs. size site more important determing language behavior while lesions size may be a factor in severity of articulatory impairment - while others believe both size and site contribute to severity of dysfunction - CT measures of stroke: severity estimated best by taking into account both size and hemisphere of lesion - TBIs rarely clean (except for missile, puncture wounds) size of lesion impt determinant of residual functional capacity - tumors widespread throughout brains boundaries erratic in destruction of nervous tissue - location of lesion only partial description of primary site of damage - patterns behavior and NP test results may not meet cookbook expectations of lesion Depth of Lesion - subcortical damage added effects of disrupted pathways or damaged lower integration centers - depth and extent of cortical lesion involving subcortical damage alter behavioral correlates of similar cortical lesions - depth of lesion = related to severity of impairment of verbal skills - i.e. anosognosia impaired awareness of ones own disabilities or disabled body parts, associated with right parietal lobe damage illustrate differences in behavioral correlates of similarily situated cortical lesiosn with different amounts subcortical involvement - lesions of right optic region of thalamus = anosognosia with neglect of paralyzed side - lesions penetrating only transmission fibers from thalamus parietal cortex = anosognosia with amnesia or lack of recognition of affected limbs or side - lesions to parietal cortex = anosognosia with positive psych symptoms confabulation, delusions Distance effects Diaschisis: chronic depression of activity that place in areas of brain outside immediate site of damage usually associated with acute focal brain lesiosn - originally thought of shock to nervous system due to disruptions in neural network www.notesolution.com
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