Is heterosynaptic modulation essential for stabilizing Hebbian plasticity and memory?
In 1894, Ramón y Cajal first proposed that memory is stored as an anatomical change in the strength of neuronal connections. For the following 60 years, little evidence was recruited in support of this idea. This situation changed in the middle of the twentieth century with the development of cellular techniques for the study of synaptic connections and the emergence of new formulations of synaptic plasticity that redefined Ramón y Cajal's idea, making it more suitable for testing. These formulations defined two categories of plasticity, referred to as homosynaptic or Hebbian activity-dependent, and heterosynaptic or modulatory input-dependent. Here we suggest that Hebbian mechanisms are used primarily for learning and for short-term memory but often cannot, by themselves, recruit the events required to maintain a long-term memory. In contrast, heterosynaptic plasticity commonly recruits long-term memory mechanisms that lead to transcription and to synpatic growth. When jointly recruited, homosynaptic mechanisms assure that learning is effectively established and heterosynaptic mechanisms ensure that memory is maintained.
Howard Hughes Medical Institute, Center for Neurobiology and Behavior, College of Physicians and Surgeons of Columbia University, New York State Psychiatric Institute, New York, New York 10032, USA.
C H
CH
Bailey
M
M
Giustetto
Y Y
YY
Huang
R D
RD
Hawkins
E R
ER
Kandel
D000818:Animals; D001048:Aplysia / Q000502:physiology*; D003214:Conditioning, Classical / Q000502:physiology*; D006624:Hippocampus / Q000502:physiology*; D006801:Humans; D017774:Long-Term Potentiation / Q000502:physiology; D008568:Memory / Q000502:physiology*; D009473:Neuronal Plasticity / Q000502:physiology*; D018377:Neurotransmitter Agents / Q000502:physiology*; D009435:Synaptic Transmission / Q000502:physiology*
D018377:Neurotransmitter Agents