1. Seminar in Developmental Disabilities
Memory Systems
Isabelle Rapin
Seminar in Developmental Disabilities
February 20, 2013
No conflict of interest

2. Multiple Memory Systems
Short term memory systems
Sensory buffers (for each modality + endogenous inputs from memory)
Working memory
Long term memory systems
Declarative (or explicit)
Non-declarative
Retrieval systems

3. 1. Schema of STM systems Short Term Memory Sensory buffers
Working memory
Sensory cortices
Prefrontal cortex

4. Short Term Memory Components: buffers + working memory
Sensory buffers: in continuous on-line reciprocal contact with working memory circuitry
Working memory: processes only information that reaches awareness, does so in the light of other inputs and priorities*
Duration range: < 1 - few seconds
Requirement: repeated inputs or rehearsal
Fate: erasure or potential storage
*Information that does not reach awareness may have
non-declarative priming effects

5. Working Memory Circuitry
Prefrontal cortex: in continuous on-line reciprocal connections with
Sensory cortices for each modality (specific buffers)
Limbic circuits
Arousal circuits
Motor output circuits
* * *
Note: Hippocampus circuitry: (data from amnestic patients)
Not critical on-line,
Critical for long term storage

6. LTM declarative systems
Declarative (or explicit)
memories
Episodic memory
(time-bound facts of the
individual’s past)
Semantic memory
(knowledge of
the world)
Medial temporal cortices +
Medial temporal cortices +

7. Declarative (explicit) Memory 1. Episodic (Tulving)
Uniquely human capacity to look back to the past and predict the future
Powerful tool
Retrieve specific facts/events in time/place context (unique, autobiographical)
Late to develop evolutionarily (man only?) and ontogenitically (infant amnesia)
Fragile to degeneration
Critically dependent on (not limited to!) hippocampal/medial temporal cortices

8. Declarative (explicit) Memory 2. Semantic Memory
Knowledge (as opposed to remembrance of specific facts)
“Picked-up” knowledge from exposure to mostly forgotten past events/experiences
Starts at birth, long before episodic memory
Broad and powerful
Much more resilient than episodic memory

9. 2 - LTM non-declarative systems
Non-declarative (implicit)
memories/learning nodes
Procedural
(skills, habits)
Priming
Conditioning
Non-associative
Basal ganglia
(putamen), etc.
Sensory cortices
Emotional: amygdala
Motor: cerebellum +
Reflex pathways

10. Hippocampus system
Binds inputs from all sensory modalities with limbic and prefrontal executive inputs
Reciprocally connected with relevant cortical and subcortical circuitry
Required for declarative memory
For fresh and midterm declarative memories
Not for very long term “ “
Not required for non-declarative memories

11. Brain molecular/cellular underpinnings of memory (Kandel, etc.)
Molecular – short term manipulation of incoming information to guide on-going behavior
Alteration in strength/effectiveness of already existing synapses
Neurotransmitter release/uptake
Cellular – long term storage
Requires protein synthesis and growth of new
synaptic receptors
dendrites
Brain circuitry – long-term (yrs) consolidation

12. Retrieval Long-term explicit memory storage:
mainly in modality-specific relevant neocortical, ± limbic areas
Recognition -- cue, strong, bottom-up
Retrieval of unique item -- top/down, effortful
Long-term implicit memory storage:
mainly in cortical/subcortical circuitry relevant to task/skill performance (e.g., motor cortex, basal ganglia, cerebellum, brainstem, spinal cord)

13. Amnestic syndrome Result of bilateral hippocampal damage
Not necessarily irreversible except for peri-lesional time-window
Impairs new explicit learning
Impairs explicit but not implicit memories
Does not impair procedural memory/skills
Does not preclude learning new skills!
Occasional cases in kids, even infants

14. Evidence for neural circuitry of memory
Lesion studies
Behavioral evidence
Imaging
Autopsy
Electrophysiology
Functional imaging (PET, fMRI…)
Subtraction: task vs. no task (“rest”)
Subtraction: impaired group vs. “typical” group

15. Problems with functional studies
Smallness of samples
Homogeneity of samples
Failure to replicate
Multiplicity of nodes in widely distributed pathways
Requirement for cooperation
Great difficulty/impossibility of testing young children
Cost
Time required for data analysis
Fancy statistical analyses required