Sensory Memory and Working Memory

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Sensory Memory and Working Memory
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Sensory Memory

• Brief
• Iconic/echoic
• High capacity
• Pre-attentive
• Is there a Neural Correlate of Sensory Memory?

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Is there a Neural Correlate of Sensory Memory?

• Stimuli that deviate from a regular sequence
  cause a change in the ERP/MEG called the mismatch
  negativity/mismatch field
• MMN/MMF only occurs when stimuli are close
  together in time
• Thought to reflect an automatic response to
  detection of difference between current and
  previous stimuli

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Short-Term Memory

• Duration of seconds
• Limited capacity
• Not pre-attentive

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Neuropsychology of STM

• Patient E.E.
• Reduced digit-span
• Normal speech, comprehension
• Normal long-term memory
• Why is this finding puzzling?

Removal of tumor in L. Angular Gyrus
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Working Memory

• STM has been replaced by Working Memory model

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Working Memory

• STM has been replaced by Working Memory model
• Transient representations of task relevant
  information
• Limited capacity store AND mechanism for working
  with that information
• Are there brain structures associated with these
  functions?

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Working Memory

• Left Supramarginal Gyrus and left premotor
  lesions associated with difficulty holding
  strings of words in mind
• Right parieto-occipital damage associated with
  visuospatial memory deficits
• Thus these are doubly dissociated

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Working Memory and Frontal Cortex

• An important aspect of working memory is
  maintaining a representation of previous
  information while it remains relevant to a
  current goal
• This information may come via sensory systems, or
  it may be reactivated from a long-term store

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Working Memory and Frontal Cortex

• Animal lesion studies reveal that the Lateral
  Prefrontal cortex is critical for maintaining
  these working representations

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Working Memory and Frontal Cortex

• Goldman-Rakic et al.
• Spatial working memory is dissociable from
  long-term associative memory

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Working Memory and Frontal Cortex

• Working Memory Task
• Well is baited with food
• Target well changes from trial to trial
• Monkeys view is blocked for a delay interval
• Monkey must indicate the baited well to get
  rewarded
• Requires maintained representation of current
  target location

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Working Memory and Frontal Cortex

• Associative Memory Task
• Each well is indicated by a picture
• Target is always associated with the same
  picture(s)
• Monkeys view is blocked for a delay interval
• Monkey must indicate the baited well to get
  reward
• Requires recall of cue from LTM

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Working Memory and Frontal Cortex

• Goldman-Rakic et al.
• Spatial working memory is dissociated from
  long-term memory
• Lesions cause deficit in working memory task but
  not association task

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Working Memory and Frontal Cortex

• Goldman-Rakic et al.
• Spatial working memory is dissociable from
  recognition memory

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Working Memory and Frontal Cortex

• Working Memory Task
• 1 of 3 objects is indicated to the monkey
• View is blocked for a delay
• 2 of the 3 objects are presented
• Monkey must select the non-match object
• Requires working memory because no other cues
  differentiate the two objects

• Recognition Memory Task
• Same as Working memory task except
• After delay, indicated object is paired with a
  novel object
• Monkey must select novel object
• Requires recognition memory to differentiate
  unfamiliar from familiar objects

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Working Memory and Human Frontal Cortex?
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Working Memory and Human Frontal Cortex
BOLD signal in lateral prefrontal cortex (area
46) is greater for memory task than for
color Discrimination task