1. Neuroanatomy of Memory
Zara A. Melikyan
(some slides are courtesy of Dr. G.P.Sutton)
February 17, 2015

2. Lecture Goals: Brain structures involved in: - Declarative memory
- Non-Declarative memory
How are memories formed:
- STM vs. LTM

3. Gross Brain Anatomy

4. Brain Structures Involved in Memory

5. The Limbic System Cortical areas: Limbic lobe
Orbitofrontal cortex - decision making
Piriform cortex - part of olfactory system
Enthorhinal cortex - memory and associative processes
Subcortical areas:
Hippocampus - consolidation of new memories
Fornix - connects hippocampus to other areas
Septal nuclei - a pleasure zone
Amygdala - emotional processes, episodic autobiographical memory, social processing
Nucleus accumbens - reward, pleasure, addiction
Diencephalon:
Hypothalamus - regulates autonomic processes. Mammilary bodies transfer signals from hyppocampus to thalamus

6. Subtypes of LTM LTM Declarative Episodic Semantic Nondeclarative
(Procedural)
Skill learning
Priming
Conditioning

7. Declarative: Formation of Memories
Medial temporal lobes:
- Hippocampus - ability to retain and recall episodic memories, different neurons are activated depending on stimulus modality. Morris water navigation tasks, Patient H.M.
Eichenbaum et al. (2001), hippocampal functions:
1. recording of episodic memories,
2. identification common features between episodes,
3. Linking these episodes in memory space
- Hippocampus + Parahippocampus - formation of new declarative memories
- Parahippocampus - recognition
- Damage: More severe impairments when both temporal lobes
are damaged
Connections between limbic system and hippocampus
- Damage: Korsakoff syndrome
- Retro- and anterograde amnesia, confabulation, lack of insight, apathy
- B1 defficiency, viral encephalitis, alcohol abuse

8. Declarative: Storage of Memories
Episodic memories
- Prefrontal (remembering context, more episodic than semantic memory) and parietal cortex
Encoding memories: Left DLPC, Retrieving memories: RDLPC
Amygdala - encoding and retrieval of emotionally charged memories, flashbulb memories. Remembering emotionally charged pictures.
- Damage: impairs episodic formation/retrieval (not semantic formation/retrieval)
Episodic and semantic memories
- Multiple different parts of cortex

9. Non-Declarative: Skill Learning
Basal ganglia, striatum, motor cortex, cerebellum, limbic system
Evidence:
- Impaired with damage to these areas
- Activation demonstrated in neuroimaging
studies

10. Non-Declarative: Priming
Exposure to a stimulus influences response to another stimulus
Positive priming - increases the speed of response, experiencing the stimulus
Negative priming - decreases the response speed, experiencing the stimulus and then ignoring it
Perceptual priming (perceptive aspect of stimulus: table - table top)
- Reduced bilateral occipito-temporal cortical activation
Conceptual priming (semantic aspect of stimulus: table - desk)
- Reduced activation of left frontal cortex

11. Non-Declarative: Associative Learning
Classical conditioning
- Cerebellum involved in eye-blink conditioning
- Humans and non-humans
Operant conditioning
- A group of brain regions are involved because many aspects of behavior involved. Frontal lobes are important.

12. How are Memories Formed?
Sensory Memory - limited capacity 12 elements (G. Sperling), limited duration (hundreds of milliseconds). Registers all the sensory information.
- Iconic
- Echoic
- Haptic
Short-Term Memory - limited capacity (7+/-2, or 4-5 elements), limited duration ( sec). Registers information to which attention is paid. Transient patterns of neuronal connection in prefrontal & temporal lobes, hippocampus essential for information consolidation from STM to LTM. Information is rehearsed and chunked.
Subtype: Working memory. Manipulate information for immediate use. E.g., reverse a phone number in your head.
Long-Term Memory - close to unlimited capacity, unlimited duration. More stable and permanent changes in neuronal connections throughout the brain.

13. How are Memories Formed?
1. Encoding
- Raw info (sensory channels) transformed to STM
2. Consolidation
- STM transformed to LTM
3. Retrieval
- Stored info brought out from LTM for use
Emotionally arousing experiences are remembered best

14. STM vs. LTM Hippocampal involvement
- Consolidation of declarative STMs to LTMs
Effect of head trauma
- Often causes retrograde amnesia
- Does not affect other memories
- May interrupt consolidation of STM to LTM

15. LTM: Remembering and Forgetting
No “upper limit”
Forgetting is natural
- Beneficial to forget some things
- Filter out unimportant information, free up cognitive resources
Memory interference
- Proactive interference - Previously learned info interferes with learning of new info
- Retroactive interference - Newly learned info interferes with previously learned info

16. Reconsolidation and False Memories
Synaptic consolidation occurs within first few hours of learning
Systems consolidation - hippocampus-dependent memories become independent of hippocampus
Memory consolidation during sleep: reactivation of hippocampal memories, transfer information to neocortex to reintegrate with existing memories.
Slow-wave sleep, sleep spindle - consolidation of declarative memory
REM - consolidates emotional declarative memories
Reconsolidation - previously consolidated memories are recalled and actively consolidated to maintain, strengthen and modify memories in LTM. ECT for phobias. Bringing up a memory can make it susceptible to distortion.

17. Thank you for your attention!
Questions?
Thank you for your attention!