Transcript No Slide Title

MEMORY SYSTEMS IN THE
BRAIN
• Some Gross Anatomy
The Human Brain
saggital section at midline
THE “FUNCTIONAL
NEUROANATOMY” of MEMORY
• Medial temporal lobe structures
– Hippocampus
– Parahippocampus (entorhinal cortex)
– Encoding and consolidation of declarative
memory
– Role in recent LTM retrieval
– Damage leads to “classic” amnesia:
severe anterograde declarative deficit
– Some evidence for LH verbal, RH spatial
• Lateral temporal lobe structures
– retrieval of declarative memory?
– Representation of semantic knowledge?
– “convergence zones” that index the
attributes of an episode?
– LH semantic, RH autobio?
• Frontal lobe structures
– Anterior areas most involved in memory
function (prefrontal, basal forebrain)
– Lateral regions linked to working memory
– Medial regions linked to executive control
and attention
– Role in strategic aspects of memory
– Damage leads to deficits in “effortful”
aspects of remembering, confabulation
• Diencephalon
– Thalamus, Hypothalamus, Mammilary
Bodies
– Close links to frontal, prefrontal cortex
– Role in activation of retrieval process
– Damage can lead to amnesia that
resembles hippocampal syndrome
• Basal Ganglia, Cerebellum
– Storage, activation of procedural skill
and memory
– Damage leads to apraxia, deficits in the
initiation and control of action
• Posterior “Association” cortices
– More “abstracted” than sensory regions
– Representation of sensory-motor
aspects of memories?
fMRI studies of
EPISODIC MEMORY
• Explosion in work
• Tulving’s HERA model (Hemispheric
Encoding and Retrieval Asymmetry)
• Encoding of episodes
– Effortful encoding / semantic activation
• Left PFC, temporal/fusiform, anterior
cingulate
– Orienting / novelty/context?
• Medial temporal, hippocampal complex;
left for verbal, right for spatial (Dolan &
Fletcher, 97)
– Mixed evidence for retrieval-success
correlations
• Retrieval of episodes
– Retrieval mode and effort
• Right PFC, maybe anterior cingulate
and cerebellum, hits and CRs (Buckner,
98)
• Inhibition of lateral temporal region,
bilaterally
– Access and activation of traces
• Medial temporal lobes, hippocampal
complex activity correlates with
subsequent success/failure
– Further localization has been
controversial
• Regions of hippocampus, hippocampus
versus parahipp, entorhinal, etc.
dissociate in various ways (see Mayes)
• A recent example: memorycontingent activity via fMRI
– Casasanto, et al. (2002)
– 240 sentences (“they buried the
money”) (RSVP?) or length-matched
asterisks
– Intentional memory task
– Yes/no recognition of old & new
sentences
– MRI scanned during encoding
– Sentences – controls (subtraction)
• Left IPFC (pos corr with d’)
• Left Middle temporal gyri
• Right superior temporal gyri (negative
corr)
• Within MTL:
– +corr for hippocampus, parahipp,
and fusiform gyryus bilaterally
MEMORY-CONTINGENT fMRI
• Wagner, et al. (1998)
– Event-related fMRI
– Word lists @ 2 sec SOA
– LIFC and L parahipp activity greater for
subsequently remembered words
• Brewer, et al. (1998)
– Event-related fMRI
– Complex scenes
– RFC, bilateral parahipp activity greater
for subsequently remembered scenes
CURRENT CONTROVERSIES
– How localized are memory functions?
– Are processes content-specific?
– What is the neurobiological relation
between episodic, autobiographical and
semantic memory?
– What is the role of the various MTL
structures in episodic attention,
encoding, storage and retrieval?
– What changes over time?
– What is the role of moderating variables
like social context, IQ, age, time since
damage, etc. on the neurobiology of
memory?