Date of Award


Degree Type


Degree Name

Master of Science




Dr. Stan Leung


The timing of a spike with afferent excitation has been proposed to influence the direction of synaptic plasticity. I hypothesize that positive excitation-spike (ES)- Pairing— generating a synaptic excitation before a spike— results in long-term potentiation (LTP), while the opposite (negative ES-Pairing) results in long-term depression (LTD) in vivo. Extracellular potentials were recorded in the hippocampal CA1 region in urethane-anesthetized rats. Basal dendritic excitation was evoked by subthreshold stratum oriens stimulation while stratum radiatum stimulation evoked a spike that invaded the basal dendrites. ES-Pairing (50 times at 5 Hz) at -10, 0 and +10, +20 ES Intervals resulted in a significant potentiation of the slope of the basal excitatory

sink for 2 hr compared to controls. Pairing at -20 ms ES Interval did not result in significant potentiation compared to controls. Thus, dendritic excitation occurring within a short time window of a spike results in LTP in vivo.



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