Talk: Modulation of synaptic plasticity in single neurons with transcranial direct current stimulat…

Speaker: Forouzan Farahani, City College of New York (grid.254250.4)
Title: Modulation of synaptic plasticity in single neurons with transcranial direct current stimulation
Emcee: B. Ezgi Arikan
Backend host: Saeed Salehi

Presented during Neuromatch Conference 3.0, Oct 26-30, 2020.

Summary: Background: Lasting therapeutic effects of transcranial direct current stimulation are thought to be mediated by synaptic plasticity. Direct current stimulation (DCS) is known to affect synaptic long-term potentiation (LTP) in vitro. We hypothesized that this is the result of a modulation of somatic spiking with DCS in the postsynaptic neuron, as opposed to indirect network effects. Previous studies with population activity provided only indirect evidence for this hypothesis. Here we aim to directly record somatic spiking in a postsynaptic neuron during LTP induction with concurrent DCS.

Methods: We recorded single-neuron activity by patching the soma of individual CA1 pyramidal neurons in a rodent in-vitro slice preparation. LTP was induced with theta-burst stimulation (TBS) applied concurrently with DCS. To specifically test the causal role of somatic polarization during DCS, we manipulated this polarization via patch pipette current injections. To explain the observed effects, we used a computational multi-compartment neuron model that captures the effect of electric fields on membrane polarization and activity-dependent synaptic plasticity.

Results: We find that TBS-induced LTP was enhanced when paired with anodal DCS as well as depolarizing current injections. In both cases, somatic spiking during the TBS was increased, suggesting that evoked somatic activity is indeed the primary factor affecting LTP modulation. However, the boost of LTP with DCS was less than expected given the increase in spiking activity alone. In some cells, we also observed spontaneous somatic spiking during DCS, suggesting that DCS also modulates LTP via spontaneous network activity. The computational model reproduces the observed effects of DCS on LTP and suggests that these effects are driven by both direct changes in postsynaptic spiking and indirect changes due to network activity

Conclusion: DCS enhances synaptic plasticity by increasing postsynaptic somatic spiking, but we also find that an increase in network activity may limit this enhancement.