Transcript Lecture 23 Powerpoint File

Sensory Memory and Working
Memory
Sensory Memory
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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
Short-Term Memory
• Duration of seconds
• Limited capacity
• Not pre-attentive
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
Working Memory
• STM has been replaced by Working Memory
model
Central
Executive
Visuospatial
Sketchpad
Articulatory
Loop
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• STM has been replaced by Working Memory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?
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
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?
Memory Condition:
Indicate if location had
been previously used
McCarthy et al. (1994)
Series of shapes
presented at varying
locations
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