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A non-synaptic mechanism underlying interictal discharges in human epileptic neocortex

Lookup NU author(s): Dr Anita Roopun, Dr Jennifer Simonotto, Dr Michelle Pierce, Dr Alistair Jenkins, Dr Ian Schofield, Professor Roger Whittaker, Professor Marcus Kaiser, Professor Miles Whittington, Professor Mark Cunningham


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Very fast oscillations (VFO, >80 Hz) are important for physiological brain processes and, in excess, with certain epilepsies. Multiple putative mechanisms have been proposed for VFO, principally:- rapid spike generation in interneurons, and emergent network activity in coupled pyramidal cell axons. It is not known whether either, or both of these are applicable in physiological and pathophysiological conditions. Here we record from human cortical tissue in vitro, resected from presumed foci in neocortical epilepsies. Spontaneously occurring interictal discharges were preserved in slices from this tissue. The VFO associated with these discharges was manifest in both the local field potential and, with phase delay, in excitatory synaptic inputs to fast spiking interneurons. However, recruitment of somatic pyramidal cell and interneuron spiking was low and there was no correlation between the VFO power and either inhibitory or excitatory synaptic input to principal cells. Furthermore, reduced synaptic inhibition failed to affect VFO occurrence. In contrast, VFO was abolished by reduced gap junction conductance, and intracellular spikelets - indicative of nonsynaptic communication between principal cells - correlated with the field VFO with c.1 ms timing. These data suggest a lack of causal role for interneurons, and favour a non-synaptic pyramidal cell network origin for VFO in epileptic human neocortex.

Publication metadata

Author(s): Roopun AK, Simonotto JD, Pierce ML, Jenkins A, Schofield IS, Whittaker RG, Kaiser M, Whittington MA, Traub RD, Cunningham MO

Publication type: Conference Proceedings (inc. Abstract)

Publication status: Published

Conference Name: Neuroscience 2009: Society for Neuroscience Annual Meeting

Year of Conference: 2009

Publisher: Society for Neuroscience


Notes: Poster presentation