- "In its most general form, the synaptic plasticity and memory hypothesis states that 'activity-dependent synaptic plasticity is induced at appropriate synapses during memory formation and is both necessary and sufficient for the information storage underlying the type of memory mediated by the brain area in which that plasticity is observed.'"
- Synaptic plasticity is not as sufficient as we previously thought 

Martin et al., 2000

Synaptic Plasticity and Memory Hypothesis 

Abraham, W. C., Jones, O. D., & Glanzman, D. L. (2019). Is plasticity of synapses the mechanism of long-term memory storage? Nature Partner Journals: Science of Learning, 4(9), 1-8. https://doi.org/10.1038/s41539-019-0048-y



Washtenaw Community College

Long-term memory (LTM) is the system for continuous and permanent storage of information, characterized by a practically limitless capacity. It holds memories for extended periods, from minutes to a lifetime. Fundamentally, LTM is divided into two main categories: implicit memory, which is unconscious, and explicit memory, which involves conscious recall. Information within LTM is typically organized into complex, structured networks.

Long-Term Memory (LTM)

1. Encoding into Short-term Memory 
2. Consolidation into Long-term Memory 
3. Retrieval into Future Behavior 

System for Creating and Retaining Memories 

Martin, S. J., Grimwood, P. D., & Morris, R. G. (2000). Synaptic plasticity and memory: an evaluation of the hypothesis. Annual review of neuroscience, 23, 649–711. https://doi.org/10.1146/annurev.neuro.23.1.649

Martin et al., 2000

Short-term memory is the result of strengthening the preexisting proteins in the synapses. Contrastingly, long-term memory comes from the creation of new synaptic connections. In other words, long-term memory changes the anatomy of the brain, but short-term memory does not.   

Memory's Relationship to the Synapses

Rehearsal is a memory-enhancing strategy that involves the conscious repetition of information that needs to be remembered. According to Craik & Watkins (1973), this process is utilized to transfer information from short-term memory to long-term memory.

Rehearsal

Once information reaches long-term memory, it must be consolidated. This consolidation process occurs at two distinct stages: at the synaptic level, which takes a few hours, and into the broader memory system, which can take weeks or longer.

Levels of Memory Consolidation

According to the theory by Collins & Loftus (1975), long-term memories are structured in semantic, or associative, networks. These networks consist of interconnected concepts, with the connection strength determined by the frequency of their association. The specific organization of these networks is unique to each individual, as they are shaped by personal experiences.

Semantic Networks in Long-Term Memory

Long-term memory is broadly categorized into two main types: explicit and implicit. This distinction is crucial because various factors, such as the aging process, specific kinds of brain trauma, and certain disorders, can selectively affect one type of memory while leaving the other intact.

Types of Long-Term Memory: Explicit and Implicit

Analyze the individual's actions described in the case study below. Identify the two primary categories of long-term memory being demonstrated and explain how each part of the scenario corresponds to one of these categories.

Analyzing Memory in Action

Long-term memory is organized hierarchically into explicit memory and implicit memory. Explicit memory is further divided into episodic memory (for events and experiences) and semantic memory (for concepts and facts). Implicit memory is subdivided into procedural memory (for how to do things), priming (where stimulus exposure affects responses to a later stimulus), and emotional conditioning (for classically conditioned emotional responses).

Long-Term Memory Subsystems Hierarchy

The storage capacity of long-term memory is ________.

A) limited
B) unlimited
C) selective
D) temporary

**Correct Answer:** B) unlimited

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