Memory

Types of memory

• Sensory (most fleeting)

• Working (maintenance): actively rehearse, few mins

• Long-term:

  • Declarative: semantic (facts), episodic (events)

  • Non-declarative: procedural memory (biking - motor-based)

Encode → store → retrieve

• Pattern completion/reinstatement - retrieve complete memory

  • Papes circuit: Hippocampus → fornix (white matter pathway) → mammillary body → anterior thalamic nucleus

  • Singulum is how medial, prefrontal, and parietal cortex communicate with one another

Patient HM - Medial Temporal Lobe removed (including hippocampus)

• improved at mirror-tracing task, but needed instructions re-explained every time & did not remember past trials

  •     Non-declarative memory does not require hippocampus

Muscle memory partly stored in white matter connections

• More white matter after learning juggling?

• In VOF (ventral occipital fasciculus) of parietal

Muscle memory involved more “efficient” activations

Priming

• Visual priming lasts much longer than word priming

Non-declarative memory: classical/Pavlovian conditioning

• Conditioned stimulus → new response

• Unconditioned stimulus →

• Need hippocampus for trace conditioning (else no conditioning will happen)

Neurodegeneration

• Alzheimer’s: buildup of amyloid plaques (CSF, atrophied hiccampi on MRI)

Encoding position

• Place cell

• Grade cell

• Border cell

• Head direction cell

Any voxels that keep track of encoding?

• Yes, heightened activity when viewing a word that will later be remembered

  • Left inferior prefrontal cortex

  • Left medial temporal love (VWFA)

• Any voxels

The animation makes it seems like place cells are in order?

Hippocampus replaying memories when sleeping (neural replay)