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Stages of Memory

For medical students2 min readUpdated 2026-10-10

The memory process is not a single-moment event, but a strict sequence of neurophysiological and biochemical events. The formation of a memory trace always begins with rapid electrical activity in nerve cells and gradually transitions to lasting structural changes in brain tissue.

Key CellPyramidal neuron of the cerebral cortex (PN)
Main TriggerDominant motivation (M)
Process StartElectrical activity of neurons
Process FinishStructural changes

Four Basic Stages of the Memory Process

From the perspective of normal physiology, any information entering the nervous system goes through a strictly defined cycle. This cycle includes four sequential stages:

  1. Perception, encoding, and learning — initial contact with information and its fixation in the brain.
  2. Storage — retention of the acquired data for a certain period of time.
  3. Retrieval — accessing necessary information as the body requires it.
  4. Forgetting — the natural process of losing access to information or erasing the memory trace, necessary to unload the nervous system.

First Stage: Mechanisms of Encoding

The very first stage — perception, encoding, and learning — is the foundation for all subsequent ones. The success of this stage is determined by the coordinated work of several mechanisms:

Formation Dynamics: From Impulse to Structure

The process of memorization cannot be viewed solely as a psychological phenomenon; it is a profound material process. It represents a complex chain of events developing over time:

First, electrical activity arises in the nervous system. This is the initial, highly unstable stage. Then, electrical impulses trigger a cascade of events that ultimately leads to structural changes in the nervous tissue. It is precisely this transformation — from a transient electrical signal to a rigid morphological rearrangement — that forms a reliable memory trace.

Stage of Primary Activation (Stage A)

To trigger the cascade described above, an initial push is necessary. This stage is called the stage of primary activation.

Mechanism: The main triggering factor here is the dominant motivation (M). It exerts a direct, targeted activating effect on the key structure of the cerebral cortex — the pyramidal neuron (PN).

Essence of the Process: Under the powerful influence of motivational excitation, the pyramidal neuron is drawn into action. It ceases to function in isolation and becomes part of a unified functional system aimed at storing vital experience.

Mnemonic

To quickly memorize the four stages, use the acronym S-S-R-F: Storage, Short-term/Encoding, Retrieval, Forgetting (or Perception, Storage, Retrieval, Forgetting).

Frequently asked questions

What specific biochemical processes ensure the transition from electrical activity to structural changes?

The transition from electrical activity to structural changes is ensured by monoaminergic mechanisms and a cascade of intracellular reactions.

The process includes the following steps:

  • Activation of intracellular postsynaptic processes by monoaminergic systems.
  • Involvement of secondary messengers — cyclic nucleotides (cAMP and cGMP).
  • Synthesis of specific protein molecules (via transcription and translation processes on ribosomes).
  • Stabilization of primary synaptic membrane alterations by newly synthesized proteins, which consolidates the memory trace in brain structures.
What brain structures, besides the cortex, are necessary for transferring information into long-term storage?

The hippocampus plays a paramount role in transferring short-term memory to long-term memory, ensuring memory consolidation and the fixation of conscious memory.

For full memory function, especially declarative memory, the integrity of the hippocampus itself and connecting pathways is crucial:

  • pathways from the hippocampus via the fornix to the septal nuclei;
  • pathways from the hippocampus via the fornix to the mammillary bodies, then to the anterior thalamic nuclei and the cingulate gyrus; this closed loop forms the Papez circuit;
  • separately, pathways from the amygdala to the dorsomedial thalamic nuclei and the orbitofrontal cortex are noted among memory pathways.
What mechanisms provide short-term retention of information before structural rearrangements begin?

Short-term information retention is provided by the process of circulation (reverberation) of nerve impulses through closed neural circuits.

Excitation from the pyramidal neuron is transmitted via its collaterals to interneurons, forming "neural traps". The maintenance of circulation is driven by the generation of excitatory postsynaptic potentials (EPSPs) in the circuit cells. The reverberation process lasts from several seconds to minutes and is interrupted only when an inhibitory postsynaptic potential (IPSP) develops in one of the circuit neurons.

What sequential stages does the memory process consist of?

The process includes four stages: 1) perception, encoding, and learning, 2) storage, 3) retrieval of necessary information, and 4) forgetting.

What types of memory participate in the initial encoding stage?

At this stage, short-term and intermediate memory mechanisms operate, with the active and mandatory participation of emotional memory.

What happens during the primary activation stage?

At this stage, the dominant motivation (M) directly activates the pyramidal neuron (PN) of the cerebral cortex, recruiting it into a functional system.

How does the memory substrate change during the memorization process?

The process begins with temporary electrical activity in neurons, which inevitably leads to lasting structural changes over time.

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