The Journal of Neuroscience, September 15, 2000, 20(18):7080-7086
Synaptic Plasticity in the Human Dentate Gyrus
Heinz
Beck,
Ivan V.
Goussakov,
Ailing
Lie,
Christoph
Helmstaedter, and
Christian E.
Elger
Department of Epileptology, University of Bonn Medical Center,
D-53105 Bonn, Germany
Activity-dependent plasticity is a fundamental feature of most CNS
synapses and is thought to be a synaptic correlate of memory in
rodents. In humans, NMDA receptors have been linked to verbal memory
processes, but it is unclear whether NMDA receptor-dependent synaptic
plasticity can be recruited for information storage in the human CNS.
Here we have for the first time analyzed different forms of synaptic
plasticity in human hippocampus. In human subjects who show a
morphologically intact hippocampus that is not the primary seizure
focus, NMDA receptor-dependent long-term potentiation (LTP) and
forskolin-induced long-lasting potentiation are readily induced at the
perforant path-dentate gyrus synapse. In this group, long-term
potentiation could be partially depotentiated by low-frequency stimulation.
Because patients with a hippocampal seizure focus showed a marked
reduction in verbal memory performance in previous studies, we asked
whether synaptic plasticity is similarly affected by the presence of a
hippocampal primary seizure focus. We found that the amount of
potentiation induced by high-frequency stimulation or perfusion of
forskolin is dramatically reduced in this patient group. In addition,
low-frequency stimulation is not effective in inducing synaptic depression.
In summary, we show that activity-dependent synaptic plasticity with
properties similar to the rodent is available for information storage
in the human hippocampus. Because both verbal memory processes and
synaptic plasticity are impaired by a hippocampal seizure focus, we
suggest that impaired synaptic plasticity may contribute to deficient
declarative memory in human temporal lobe epilepsy.
Key words:
hippocampal synaptic plasticity; N-methyl-D-aspartate; human; dentate gyrus; temporal lobe epilepsy; declarative memory
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