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. Author manuscript; available in PMC: 2016 Jun 28.
Published in final edited form as: Neuroscientist. 2014 Apr 11;20(5):483–498. doi: 10.1177/1073858414529829

Figure 2. Experimental evidence for heterosynaptic plasticity.

Figure 2

(A) Heterosynaptic LTD in the hippocampus (Lynch and others 1977, field potential recording). Induction of LTP at Schaffer collateral-commissural inputs to apical dendrites of CA1 pyramidal neurons was accompanied by an LTD at commissural inputs to basal dendrites that were not stimulated during the induction. And vice versa, induction of LTP at inputs to basal dendrites was accompanied by LTD of inputs to the apical dendrites. (B) Distributed plasticity and breakage of input specificity at short distances (Bonhoeffer and others 1989; Engert and Bonhoeffer 1997; Kossel and others 1990; Schuman and Madison 1994). After pairing of one input to a CA1 neuron, synapses formed by nearby fibers on that cell and even on nearby neurons were potentiated too (pink circle). (C) Mexican hat profile of plasticity (Royer and Paré 2003; White and others 1990). In structures with regular organization of the inputs, such as the hippocampus or amygdala, induction of LTP was accompanied by a weaker LTP at nearby inputs (pink circle) and heterosynaptic LTD at more distant inputs (green annulus), with the amplitude of LTD decreasing with distance. Symmetrical profile was observed around the site of LTD induction. This resulted in a Mexican hat profile of plasticity, with balanced potentiation and depression (Royer and Paré 2003). (D) Long-term plastic changes can be induced by rises of intracellular calcium concentration produced by photolysis of caged calcium (Neveu and Zucker 1996; Yang and others 1999). LTP could be induced by large increases of intracellular calcium, and LTD by smaller amplitude prolonged increases.