Cortical Remapping through Spike Timing-Dependent Plasticity

Experimental evidence from a number of different preparations indicates that repeated pairing of pre-and postsynaptic action potentials can lead to long-term Long-term modification of synaptic efficacy can de-Spike timing-dependent plasticity (STDP) forces syn-pend on the timing of pre-and postsynaptic action apses to compete with each other for control of the potentials. In model studies, such spike timing-depen-timing of postsynaptic action potentials, and this, by dent plasticity (STDP) introduces the desirable fea-itself, can lead to competitive Hebbian synaptic modifi-tures of competition among synapses and regulation cation (Kempter et al., 1999; Song et al., 2000). Here, of postsynaptic firing characteristics. STDP strength-we explore whether STDP alone, without any global con-ens synapses that receive correlated input, which can straints on synaptic efficacies or additional forms of lead to the formation of stimulus-selective columns plasticity, can account for major features of activity-and the development, refinement, and maintenance dependent plasticity of columns and maps during devel-of selectivity maps in network models. The temporal opment and adulthood. asymmetry of STDP suppresses strong destabilizing An important feature of the form of STDP we discuss self-excitatory loops and allows a group of neurons is its asymmetry with respect to the timing of pre-and that become selective early in development to direct postsynaptic action potentials. Long-term potentiation other neurons to become similarly selective. STDP, (LTP) of synapses occurs if postsynaptic action poten-acting alone without further hypothetical global con-tials are repeatedly paired with presynaptic spikes that straints or additional forms of plasticity, can also re-precede them by no more than about 50 ms. Presynaptic produce the remapping seen in adult cortex following spikes that repeatedly follow postsynaptic action poten-afferent lesions. tials, within a time window either similar to the LTP window or considerably longer, depending on the syn-Introduction apse, induce long-term depression (LTD). The temporal asymmetry of STDP has a number of The formation of cortical maps during development important consequences. B, that tend to fire together in the sequence A followed 1999) and their modification during adulthood (Buono-by B. In a time-independent Hebbian model, excitatory strengthened in this situation. STDP, on the other hand, are fruitful testing grounds for ideas concerning activity-strengthens the synapse from A to B while weakening dependent synaptic plasticity. While activity-indepen-the synapse from B to A. This allows neuron A to modify dent processes undoubtedly play an important role in the selectivity of neuron B without itself being affected selective groups of neurons with correlated …