increases in hippocampal-dependent cognitive function. One important caveat is that under a more intense LTP-induction protocol, we observed that LTP in stress slices is inhibited. This result agrees with studies showing that chronic stress in different forms impairs LTP in the hippocampus (Pavlides et al., 2002; Alfarez et al., 2003). This highlights the notion that varying levels and types of synaptic plasticity may serve different physiologies and behaviors. For example, in a recent study, we observed that this same CMS protocol selectively enhances trace (hippocampal-dependent) fear conditioning, but does not affect either contextual fear conditioning, the prototypical hippocampal-dependent fear task, or non-hippocampal fear conditioning (Reich et al., 2013). However, more evasive 21-day chronic restraint stress protocols lead to increases in both hippocampal and non-hippocampal dependent forms of fear conditioning (Conrad et al., 1999; Cordero et al., 2003; Pêgo et al., 2008) but also impairs hippocampal LTP induction (Pavlides et al., 2002).
