Reading focus
Syllabus: How Does the Nervous System Develop and Change?
Connect the properties of potentiation with the requirements of a memory mechanism, keeping induction and maintenance distinct.
Why you’re reading it. This supplies a mechanistic proposal against which observations of learning-related structure can be evaluated.
A question to consider. What feature of a memory task would you use to test the importance of input-specific rather than indiscriminate synaptic strengthening?
Why this reading
A durable change in communication between neurons is a plausible component of memory, but resemblance is not identity. Bliss and Collingridge explain why long-term potentiation became a synaptic model of memory and what evidence would be needed to connect that model with learning and retention.
Before you read
Synaptic efficacy describes how strongly an input affects a receiving cell. Long-term potentiation, or LTP, is a persistent increase in that response after an inducing event. This review concentrates on NMDA-receptor-dependent hippocampal LTP. Induction starts a change, expression produces the altered response, and maintenance sustains it. A receptor's dependence on both transmitter and membrane voltage can make it sensitive to coincident events.
Read for
- Follow cooperativity, associativity, and input specificity in the stimulation comparisons. Ask what each property contributes to the proposed memory mechanism.
- Distinguish evidence about initiating potentiation from evidence about where and how its continued expression occurs.
- Examine the step from synaptic physiology to behavioral memory, including the limitations and competing possibilities in Box 4.
Consider afterwards
- Why does demonstrating a long-lasting synaptic change not by itself demonstrate that a memory has been stored?
- What would a selective intervention need to preserve to test a role in memory without simply impairing all neural communication?
Editorial context
This is an influential 1993 mechanistic synthesis, with hypotheses and disputes that should be read in their historical setting. It does not make one form of hippocampal LTP the explanation of every kind of memory. Later approaches, such as Hayashi-Takagi and colleagues' manipulation of recently potentiated motor-cortical spines, test more selective links between a synaptic change and learned behavior. Those experiments address a different preparation and do not validate every proposed molecular step in this review.