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Memory (44 Short-Term Memory (candidate mechanisms (intrinsic cellular…

- - - - population of active neurons that maintain an active memory trace that remains for a period of time
      - involves feedback excitation to induce further spiking activity
      - involves feedback inhibition resulting in fixed point or oscillatory attractor dynamics
      - depends upon a preexisting structure of synaptic connectivity
    - - maintain memory for prior input in the form of persistent spiking activity in single neuron level
      - afterdepolarization/plateau potential
        membrane potential remains depolarized after the current injection is stopped by help of acetylcholine
      - such potential is resistant to transient distractors or brief periods of hyperpolarization
      - found in entorhinal cortex, presubiculum, perirhinal cortex, and hippocampus
      - support both temporary retention of novel information and synaptic changes for long term retention
    - - short-term potentiation/post-tetanic potentiation
        Transient changes in synaptic efficacy that decay over a period of seconds
    - - activation of multiple item representations is regulated by low-frequency theta oscillations such that each item representation is sequentially activated during a different theta phase
  - - - PFC lesions influence the active maintenance of the task that is currently relevant but not temporary storage of item information directly
      - PFC is related to context-dependent mappings bw stimuli and actions
      - not the site of all STM storage
    - - neocortical areas in the MTL play a role in STM when the relevant information is being actively maintained
      - Entorhinal and perirhinal cortex shows persistent, object-selective activity during short retention delays
      - hippocampus involves short-term retention of spatial and relational information
  - - - evidences supporting dual storage of LTM and STM came from serial position effects
      - the magnitude of the primacy effect is actually influenced by rehearsal, and that robust recency effects can be observed even when phonological rehearsal is not feasible
    - - phonological loop and visuospatial sketchpad
        the short-term representation of phonological and visual information
      - central executive
        the manipulation of information in the service of task goals that mediate the selection, inhibition, and manipulation of information in WM
      - episodic buffer
        Short-term retention of materials beyond the phonological and visuospatial domains
  - - - episodic memory retrieval involve cue processing that lead to a reinstatement of the hippocampal neural pattern
      - Retrieval cues are thought to unlock the HNP
      - hippocampal pattern completion
        A complete pattern can be reconstructed from only a subset of the elements making up that pattern
      - reinstatement of the HNP is then thought to be instrumental in reinstating the corresponding cortical neural pattern (CNP)
    - - Hippocampal encoding relates to memory for the contextual details associated with individual events
      - PRc encoding related to whether items were later recognized
      - PRc and PHc are domain-specific to objects and scenes respectively
      - hippocampus may be important in domain-general binding of the various event elements
    - - increased hippocampal activation is related to the conscious recollection of studied episodes, contextual details, and recognition of arbitrary item associations
      - retrieval specifically activates the same MTL neurons that were active during the original encoding experience
      - hippocampal replay
        Reactivation of hippocampal memory traces during retrieval
    - - memory encoding and retrieval are not performed in isolation, but rather are interactive processes
      - new learning influences and is influenced by reactivation of existing memories
      - memory reinstatement during new encoding helps reduce forgetting of past events
      - hippocampus helps to construct memory representations that link memory elements across discrete experiences
      - Integrative encoding also support novel inferences about the relationships between memory elements and generalization of knowledge to new situations