Week 9 - 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

      • Papez circuit: Cortex → EC → Hippocampus → fornix (white matter pathway) → mammillary body → anterior thalamic nucleus → mPFC & mPC

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

  • Trisynaptic pathway? Perforant → mossy fiber → schaffer collateral

    Perforant path: EC → DG

    Mossy fibers: DG → CA3

    Schaffer collaterals: CA3 → CA1

    Monosynaptic: EC → CA1 (direct)

    Output loop: CA1 → subiculum → EC

  • KF and EE, for example, are two patients who had damage to the angular gyrus.

    • Short term memory deficits, good with long-term

  • 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 & SLF

  • Muscle memory involved more “efficient” activations

  • Procedural memory requires basal ganglia

  • Priming

    • Visual priming lasts much longer than word priming

    • Patient MS - right occipital lobe damage, impaired priming intact LTM

  • 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)

  • in entorhinal cortex and in subiculum, you have border cells