Storage is the retention of encoded information over time. After material has been registered by the senses and processed into a usable form, it must be held in some durable state if it is to be available later. Without storage there can be no later retrieval.

Memory systems differ in how long they maintain information. Sensory memory lasts fractions of a second. Short-term or working memory lasts seconds unless refreshed. Long-term memory can last years or a lifetime. The physical basis of long-term storage is thought to involve lasting changes in synaptic strength and, at larger scales, reorganization of neural networks.

Storage is not a passive warehouse. Memories can be consolidated, reconsolidated after retrieval, and gradually transformed. Interference, decay, and retrieval failure can all make stored information harder to access even when the underlying trace has not been completely erased.

• Retention of encoded information
• Occurs across multiple time scales
• Supported by synaptic and systems-level changes
• Subject to later modification

The quality of storage depends heavily on how the material was originally encoded and on subsequent experiences that interact with the trace.