Limitations & benefits of patient studies

• Limitations of Patient studies

  1. Assumption of modularity - parts of brain work independently
  2. Lesions extensive & varied
  3. Lesion anatomy inaccurate, connections not considered
  4. Individual differences in functional anatomy
  5. Poor temporal resolution
• Phrenology

  bumps on head determine mental/ brain faculties
• Modularity of function 


  • assumption that mental processes occur with a high degree of isolation
  • when 1 area damaged other regions don't adapt functions
  • brain = static
  • processes/ dynamics neglected: neurons, not black boxes, that perform function - but how?
• Modularity of function - brain plasticity 


  • in reality brain reorganises quickly
  • intact regions change behaviour = difficult to infer function of damaged region
• Lesions extensive and varied

  • patients often have large lesions
  • lesions oftern damage several functional centres = few have 'pure' deficits
  • lesion size & location variable - hard to find similar groups - but inferences from single patients = weak
  • individual difference in recuperative history

  = variability in participants
• Lesions anatomy inaccurate & connections not considered

  • Anatomical scans show destroyed regions, but intact regions may not be functioning
  • regions may be disconnected from other regions that provide input
• Individual differences in functional anatomy 


  • assume anatomical regions of brain does same function in all individuals
  • clearly violated assumption - e.g. Wada test indicates left hemisphere predominates in language processing in most
  • variability of function across individuals reduces power of group studies
• benefits of patient studies

  • show areas necessary for particular cognitive function (double dissociation)
  • show cognitive, emotional, social consequences of a deficit
  • cost and time effective, single case studies possible
• why can't localize speech production in this area

  • damage not limited by functional boundaries
  • lesion might be smaller than functional module
  • interindividual differences in brain organisation
  • result might reflect increased vulnerability of region to injury
  • area might just be interconnected with actually relevant area
• Poor temporal resolution & experimental control

  • Patient studies identify necessary brain regions & cognitive processes, but cannot discern processing stages
  • Memory deficits may result from encoding, retention, or recall failures
  • Lesion location lacks experimental control, but animal studies with experimental ablation offer this control
  • Other methods address these limitations