Dissociation

• Dissociating cognitive functions, and brain regions

  • Cognitive functions can be dissociated (separated to a degree) from each other through selective impairment
  • & for function of brain regions
• Dissociation studies

  • require minimum of 2 groups & 2 tasks.
  • Comparison between patient/control groups shows deficit
  • 2 tasks needed to determine whether deficit specific to particular function, or reflects more general impairment
• Single dissociation

  • Performance in declarative task lower in temporal lobe deficits than nondeclaritive
  • control performance = both same = temporal lobes involved in declarative memory
• Limits of single dissociation 


  • result suggest temporal lobes involved in declarative memory
  • conclusion = temporal lobes involved in declarative memory, & NOT in nondeclarative memory, does NOT follow

  = possible that poor performance caused by another factor -

  e.g. deficit in concentration, - test of declarative memory required more concentration than test of nondeclarative me
• Double dissociation example 


  • temporal lobe deficits = lower performance in declarative memory = temporal lobes involved in declarative memory
  • cerebellum deficits = lower performance in nondeclarative memory = cerebellum involved in nondeclarative memory
• Double dissociation provides evidence that

  • some cognitive processes = critical for task X = not critical for task Y & vice versa
  • brain-area A critical for task X but not Y
  • performance differences reflect functional differences between groups, rather than unequal sensitivity of 2 tasks = confidence in task
  • Participants don‘t have to be perfectly intact on either task - just need to be significantly better at one task than other