selectively. In addition to engineering efficient optogenetic methods, drugs affecting short-term synaptic plasticity, but less so firing rates, can be used to probe circuits. For example, drug activation of presynatic cannabinoid receptors (Freund et al., 2003) had no effect on the positional representation of hippocampal place cells, field size or their population vector, thus leaving the ‘spatial map’ intact, yet the rats could not solve a spatial task. Since the drug interfered with the timing of neuronal spikes at the gamma-theta time scale, the behavioral impairment may be explained by the inability of the reader mechanisms to properly interpret the hippocampal messages (Robbe and Buzsáki, 2009).
