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. Author manuscript; available in PMC: 2011 Apr 14.
Published in final edited form as: Trends Neurosci. 2010 Jan 12;33(3):153–161. doi: 10.1016/j.tins.2009.12.003

Figure 4. Hypothetical synaptic modification curves for young (green) and aged (purple) CA1 neurons.

Figure 4

The X-axis shows different stimulation parameters used to induce LTP or LTD, and the Y-axis is magnitude and sign of synaptic modification. (1) In old CA1 neurons altered Ca2+ homeostasis causes a change in the synaptic modification curve, such that there is a greater probability of LTD following 900 pulses of 1 Hz stimulation (LFS) [45]. (2) This age difference can be eliminated by increasing the ratio of Ca2+ to Mg2+ in the recording medium [44]. (3) Additionally, with weak stimulation parameters (i.e., theta burst stimulation ot 4, 100 Hz pulses), there is a lower probability of LTP induction in aged compared to young CA1 neurons [81, 82]. (4) When more robust stimulation is used (i.e., fifteen 20 ms bursts at 400 Hz) the amount of synaptic modification is equivalent between age groups [41].