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					week5.1: neuropsychology: frontal lobes




           09.23.2007 / PSY332




                      week5.1: neuropsychology: frontal lobes
frontal lobes → interconnected




      numerous interconnections with other brain regions
        1   emotion & mood centers (limbic system)
        2   cognitive centers
      3 general anatomical divisions of the frontal cortex
        1   precentral cortex
        2   limbic component
        3   prefrontal cortex




                                      week5.1: neuropsychology: frontal lobes
week5.1: neuropsychology: frontal lobes
precentral cortex




      consists of areas that lie immediately before the central sulcus
      consist primarily of primary & secondary motor control areas
      lesions result in intentional motor control issues




                                      week5.1: neuropsychology: frontal lobes
limbic component




     inferior & medial parts of cingulate gyrus
     posterior parts of the orbital frontal areas
     interconnections with the amygdala, hippocampus, thalamus,
     etc.




                                     week5.1: neuropsychology: frontal lobes
prefrontal cortex




      area implicated in studies of personality & behavioral effects
      of frontal lobe lesions
      has extensive interconnections with virtually every other part
      of the cerebrum
          association areas in temporal, occipital & parietal lobes
          limbic system
          thalamus
          basal ganglia




                                       week5.1: neuropsychology: frontal lobes
cognitive impairment




      patients with frontal lobe lesions:
           may have extensive brain injury
           may have numerous behavioral changes
           typically score within the normal range on IQ tests




                                       week5.1: neuropsychology: frontal lobes
cognitive impairment, 2




      cog. impairment ass. with frontal lobe lesions:
           involve cognitive abilities not measured by conventional IQ
           tests
      abstract reasoning & hypothesis testing
      memory disorder
      attention deficits
      difficulty in initiation of cognitive activity




                                       week5.1: neuropsychology: frontal lobes
abstract reasoning impairment




      overriding functions of frontal lobes are to modulate & control

        1   motor function
        2   emotion
        3   attention
        4   other such cognitive activity
      virtually all aspects of frontal lobe impairment can be
      considered a specific aspect of a general deficit of control




                                            week5.1: neuropsychology: frontal lobes
abstract reasoning 1




      involves making complex associations between semantic
      elements & super-ordinate categories
      first, semantic associations
      patients have difficulty formulating super-ordinate categories
      which subsume individual semantic elements
          e.g., cannot reason that cars, trains, airplanes, etc., are
          members of category ’modes of transportation’




                                        week5.1: neuropsychology: frontal lobes
abstract reasoning 2



      difficulty formulating & using rules that guide future behavior
      even if given a rule, patients have difficulty using it to guide
      behavior
      patients cannot conceptualize goal states
      patients cannot use goals as objectives to guide thought &
      actions
      actions → motivated by very concrete, superficial goals
          e.g., immediate gratification of simple impulses




                                      week5.1: neuropsychology: frontal lobes
disturbances of behavior & personality




      behavioral syndrome characterized by:
          lack of originality
          lack of creativity
          impairment of attention
          tendency to display inappropriate emotions & behavior
          difficulty initiating behavior
          once initiated, activity may continue without stopping




                                      week5.1: neuropsychology: frontal lobes
dist. of behavior & personality: emotion



      2 principle reactions
           inhibition → apathy, flattened affect, withdrawal, etc.
           disinhibition → euphoria, impulsivity, irritability, anxiety,
           obscene language, etc.
      emotional disturbances may include:
           laughing or crying in inappropriate situations
      emotional responses appear superficial & variable
      patient usually has no awareness that their emotional response
      is incorrect or extreme




                                         week5.1: neuropsychology: frontal lobes
language impairment, Broca’s area




      Broca’s area resides in left frontal lobe
      lesions to Broca’s area? (‘Tan!’)




                                      week5.1: neuropsychology: frontal lobes
language impairment, 2




     dorsolateral frontal lobe lesions
     reduction in language production
         language is fluent with correct syntax
     difficulty initiating & maintaining complex, spontaneous
     conversation
     deficit in ‘verbal fluency’, or ‘low verbal production’




                                    week5.1: neuropsychology: frontal lobes
language impairment, 3


     frontal lesions in secondary motor control areas (lesions to
     cingulum)
     patient comprehends language but cannot produce any
     vocalizations
     deficit is of the basic motor control or oral apparatus
     i.e., no initiation of activity
     patient is mute
     patient often indifferent to communication & does not show
     frustration, unlike Broca’s aphasia
     severe cases of mutism → ‘locked in’




                                       week5.1: neuropsychology: frontal lobes
impairment of motor function, 1




      highly controlled/volitional components of motor control
      located in frontal lobes including:
          primary motor control area
          basal ganglia
          cerebellum
          complex control of skeletal muscles in the execution of actions




                                      week5.1: neuropsychology: frontal lobes
impairment of motor function, 2




      impairments:
          perseveration
          in-coordination
          motor impersistence
          hypokinesia




                                week5.1: neuropsychology: frontal lobes
impairment of reflexes




     frontal lobes primary inhibitor of fundamental reflexes
     these fund. reflex. were presumably inherited as part of
     primitive brain structures (characteristic of the primate brain)
         grasp reflex
         snout & sucking reflexes




                                    week5.1: neuropsychology: frontal lobes
impairment of reflexes, grasp




      grasp reflex elicited by stroking the skin of the palm
      patient grasps the object
      has difficulty releasing the grasp even when told to attend to
      the hand & release grasp




                                     week5.1: neuropsychology: frontal lobes
impairment of reflexes, snout/sucking



      snout/sucking reflexes elicited by stimulating the lips & space
      between the upper lip & nose
      patient extends the lips outward for the snout reflex
      patient compelled to suck on an object placed in the lips when
      suck reflex is present
      frontal lobes usually inhibit these reflexes during childhood &
      adulthood
      with lesioned frontal lobes this inhibition is removed/reflexes
      return




                                     week5.1: neuropsychology: frontal lobes
note on social behavior




      social perception & action are very complex
      people do not have wide tolerance for social behavior
      even minor deviations in social behavior are noticeable




                                     week5.1: neuropsychology: frontal lobes
impairment of social behavior



      FL lesions result in pervasive defect in planning & modulation
      of behavior
      patients have compelling deficits in maintaining appropriate
      social responses
      great difficulty generating appropriate behavioral options in
      social situations
      base their behavior on concrete simple motivations (instead of
      considering the abstract appreciation of the social scene)




                                    week5.1: neuropsychology: frontal lobes
reduplication syndrome



      similar to confabulation
      patient confabulates the current environment (e.g,. hospital)
      is actually another place similar to the current setting
          e.g., university dormitory
          apartment building
      confabulated place is always somewhere else & usually familiar
      to the patient
      patient maintains confabulation even when confronted with
      salient, contradictory information




                                       week5.1: neuropsychology: frontal lobes
very severe FL lesions




      complete disintegration of behavior, observed as:
          nonreactive to environmental cues
          nonreactive to instructions from others
          reactive to irrelevant stimuli
          echolalia (Tourette’s syndrome-esq)
          mutism
          agraphia
          confusion
          generalized slowing




                                      week5.1: neuropsychology: frontal lobes
assessment




     important constructs to assess among executive functions:
       1   attention & freedom from distractability
       2   initiation, task persistence & maintenance of set
       3   mental flexibility & abstract reasoning




                                       week5.1: neuropsychology: frontal lobes
assess → attention & freedom from distractability




      letter vigilance tasks:
           patient asked to listen to a long string of letters and respond
           every time an ‘a’ is read
           good test of distractability
      Stroop test
           provides an evaluation of sustained & selective attention
           patient must selectively attend to one stimulus while inhibiting
           a more salient one




                                        week5.1: neuropsychology: frontal lobes
assess → initiation & maintenance of set



      initiation observed behaviorally as latency to respond, or
      inability to respond without prompting
      maintenance of set = ability to continue with an activity
      despite competing stimuli
          Go/nogo tasks → mirror a tapping task, then, task demands
          switch & patient must inhibit salient responses & give the
          opposite response
          word fluency tasks → think of as many words as you can that
          start with the specified letters of the alphabet (e.g., F, A, S)
          patients who lose set cannot stay on letter, or task




                                      week5.1: neuropsychology: frontal lobes
assess → mental flexibility & abstract reasoning




      patient sorts objects or categories
      WCST
      measures of perseverative tendency, failure to maintain set, &
      categories achieved help determine problem solving ability




                                     week5.1: neuropsychology: frontal lobes

				
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