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

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

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

• 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

• STM has been replaced by Working Memory model

• STM has been replaced by Working Memory model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?

• 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

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 longterm store

Working Memory and Frontal Cortex
• Animal lesion studies reveal that the Lateral
Prefrontal cortex is critical for maintaining these “working” representations

Working Memory and Frontal Cortex
• Goldman-Rakic et al.
• Spatial working memory is dissociable from long-term associative memory

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

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

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

Working Memory and Frontal Cortex
• Goldman-Rakic et al.
• Spatial working memory is dissociable from recognition memory

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

Working Memory and Human Frontal
Cortex?
McCarthy et al. (1994)
Series of shapes presented at varying locations
Memory Condition:
Indicate if location had been previously used
Control Condition:
Indicate if shape is red
Baseline: Passive viewing

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