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3 Processing speed (Salami (Measures of DTI (FA ((Low (In aging,…

- - - - Fractional anisotrophy
      - how direction-specific the diffusion of water is
      - High
        
        Intact local WM integrity
        
        Low
        
        In aging
        
        Information processing speed problems
      - Anterior
        
        executive tasks
        
        Posterior
        
        visual memory tasks
    - - Mean diffusivity
      - Average rate of water diffusion
      - Increased in age
      - High
        
        problems with processing speed, global cognition, executive function
        
        Poor local white matter
  - - - Age effect
        
        FA decrease, MD increase
        
        More in anterior than posterior
      - WM intergrity mediates effects of aging on cognition
        
        some WM tracts contribute more to some functions than others
        
        Frontal lobes (left)
        
        fluency
        
        Widespread
        
        Episodic memory
    - - Age effect of FA
        
        More in anterior
        
        Bilateral
      - Processing speed only significant effect
      - White matter changes not related to cognition, only to speed
      - Read results again
- - - - Performance in many cognitive tasks is limited by relatively general processing constraints, in addition to restrictions of knowledge and variations in efficiency or effectiveness of specific processes
      - Speed of processing is a critical processing constraint associated with increased age
    - - Limited time mechanism
        
        Relevant cognitive operations are executed too slowly to be succesfully completed in available time
        
        Assembly line metaphor
        
        Available time is occupied by execution of early operations
        
        More prominent in complex tasks
        
        External
      - Simultaneity mechanism
        
        Slow processing reduces amount of simultaneously available information needed for higher level processing
        
        Juggling metaphor
        
        Assumption
        
        info decreases over time as a function of decay/displacement
        
        Implication
        
        Dynamic capacity of processing systems such as W< wil be affected with impairments of higher order processes such as abstraction, elaboration or integration
        
        Speed effects may be interect because they affect effectiveness of process that affects cognitive performance
        
        Recuction in speed leads to broad/diffuse reduction in efficiency of many types of processing
        
        Figure in manual
        
        In other salthouse
        
        Internal #
    - - 3 hypotheses
        
        Age related slowing is not exclusively determined by specific and independent defecits
        
        Processing speed functions are a mediator of some of the relations between age and measures of cognitive functioning
        
        Path analyses
        
        Strong
        
        age speed
        
        Moderate
        
        speed cf
        
        Weak
        
        Age Cognitive function
        
        Mediators
        
        Cognitive functions mediated by processing speed
        
        Regression
        
        how much of the variance can be explained by other factors
        
        The limited time and simultaneity mechanisms are primarily responsible for the relations between speed and cognitive functioning
      - Read again
        
        Also see other salthouse
- - - - Diffuse axonal injury
      - results in generalized shearing of white matter pathways
        
        reduced interconnection between networks, resulting in a generalized slowing of cognitive processing
      - Wider range of NP problems
    - - Attentional set shifting
        
        Trail making test
      - Devided attention
        
        complex RT tasks
      - Focused attention/response inhibition
        
        Stroop
    - - defecits in DAI on basic speed of processing task
        
        no additional deficits in focused attention, attention shifting and divided attention
    - - Specific effect of basic speed processing in DAI
      - Effects on complex tasks removed when taking speed into account
      - Damage to white matter tracts resulting from DAI is thought to produce indirect interconnections between neural networks, leading to longer processing times