Human Synapses Show a Wide Temporal Window for Spike-timing- Dependent Plasticity Synaptic Neuroscience

plasticity (STDP) depending on parameters such as brain area and neuron type (Froemke et al. However, it is unknown what synaptic learning rules exist in human synapses and whether similar temporal windows for STDP at synapses hold true for the human brain. There are few studies on synaptic LTP and LTD in humans. With field potential recordings from hippocampal and neocorti-cal tissue excised from human patients it was shown that high frequency stimulation (100 Hz) induces LTP in human synapses (Chen et al., 1996; Beck et al., 2000). Blocking NMDA receptors with APV prevents LTP induction, indicating that plasticity of human synapses shares molecular mechanisms with animal models. Low frequency stimulation (1 Hz) resulted in LTD (Chen et al., 1996), showing that the strength of human synapses can be regulated bi-directionally. Indirect evidence suggests that coincident millisecond timing of activity is likely to govern synaptic changes in humans as well (Stefan et al., 2000; Wolters et al., 2003). Pairing transcranial magnetic stimulation (TMS) of motor cortex with peripheral nerve stimulation in vivo can alter motor-evoked potentials in muscles, and precise timing determines the sign of this plasticity (Wolters