Working memory (2)

• Complex span task


  • Solve each maths problem & say word aloud – recall all 3 words at end
  • Complex span requires retention of info in WM & requires active processing, manipulation and updating of this info (WM)
  • Requires following a fairly complex set of task rules
• Fluid IQ


  • Involves construction of 'mental program' for task performance
  • Subdividing complex tasks into manageable chunks
• Multivoxel pattern analysis (MVPA)


  Takes advantage of the fine grained patterns of activation across groups of voxels
• Rao et al. (1997) findings


  • Over ½ neurons showed both object &location selectively
  • Neurons in PFC adapt flexibly to represent task relevant info
  • PFC = not organized according to type of stimulus held in WM
  • PFC may not store info in WM
• Riggall & Postle (2012) findings


  • Could decode which direction & how fast dots were moving but only from visual & temporal cortex
  • PFC provided no info
  • Task instructions could be decoded from PFC & parietal regions
• Postles alternative theory


  • WM as an emergent property
  • WM functions produced when attention = directed to systems that have evolved to accomplish or sensory,- representation-, action-related functions
• Higo et al. (2011) method

  1. Ppts held 2 objects in WM & cued either to maintain both or singular object

  2. Selective or non-selective attention

  3. Asked to decide if any objects in array matched objects they were holding in WM
• Higo et al. (2011) findings


  • Activation in PFC = greater for selective condition
  • Activation in PFC modulated activation in diff occipitotemporal regions depending on which stimulus the subject maintained in WM
  • Combined TMS/fMRI showed disruption of PFC activity caused distal effects on occipitotemporal activation - establishing direction of causation
  • PFC sends an attentional bias signal to sensory-specific regions – enhances processing of task-relevant object during WM
• Distributed neuronal architecture of WM


  • Lower level visual regions maintain temporary representations of items in WM
  • PFC holds representation of task rules for manipulating info
  • The central executive
• Duncan et al (2012) – Rule WM task

  Findings:

  • Strongest correlation between WM & IQ
  • Other types of WM (eg.complex span) correlated with fluid IQ – not sig

  Conclusions:

  • Manipulating/processing infor in WM = key component of fluid IQ
  • Construction & use of rules underlies individ diff in fluid IQ
•  Duncan et al. (2013)

  • Fluid IQ involves construction of  ‘mental program’ for task performance
  • Subdividing complex tasks into manageable chunks
•  Linden et al. (2012) - holding multiple objects in WM


  Findings:

  • PFC doesn’t hold info for WM
  • Regions holding info in WM = proterior part of brain
  • Visual processing regions = fusiform face area & areas of ventral visual stream

  Implications:

  • Same regions enable us to process an object when we see it = also involved in storying temporary representations of objects in WM