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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 2. Summary of age-related alterations in LTP and LTD between young and aged animals.

Figure 2

The Y-axes reflect the change in the extracellular EPSP (mV) following LTP or LTD induction and the X-axes time following induction of LTP or LTD (green lines - young rats; purple lines - aged rats). A) LTP induction at perforant path–CA3 synapse is intact in aged rats when robust (supra-threshold) stimulation protocols are used, but LTP maintenance over days is impaired [40]. B) LTP induction is also intact at the perforant path–granule cell synapse when robust stimulation parameters are used. Similar to what is observed in CA3, LTP decays more rapidly over days in the dentate gyrus of old rats [left panel; 29]. When weak (peri-threshold) stimulation protocols are used, however, aged rats also show LTP induction deficits at the perforant path dentate gyrus synapse [right panel; 42, 43]. This induction impairment could, in part, result from the higher threshold in LTP induction at this synapse [80]. C) At the Schaffer–CA1 synapse both LTP induction and decay over hours is similar across age groups when robust stimulation protocols are used [top left panel; 41]. As shown above for the dentate gyrus, however, when weak stimulation parameters are used, LTP induction deficits are unmasked in old rats [top right panel; 81, 82]. This LTP induction deficit is not due to a threshold change at Schaffer collateral synapses in old rats [83]. For CA1, aged rats have also been shown to be more susceptible the induction of LTD following low-frequency stimulation (LFS) [bottom left panel; 45]. Moreover, LTP can be reversed with same stimulation protocol that induces LTD. While LTP is not completely reversed by this LFS in young rats, old rats are also more prone to this reversal of LTP [bottom right panel; 45].