Single unit action potentials in humans and the effect of seizure activity

Abstract

See Kimchi and Cash (doi:) for a scientific commentary on this article.In patients undergoing surgical evaluation of focal neocortical epilepsies, Merricks et al. perform the first single-unit recordings of neurons in the ictal core and contrast their activity patterns with those of the penumbra. Single-unit spiking recovers rapidly after seizure termination, suggesting a network rather than cellular cause of post-ictal dysfunction.

Single‐unit activities during the transition to seizures in deep mesial structures

“…The longer recording durations provided a systematic test of single-unit stability over the transition to seizures, which was further confirmed by the reappearance of the waveforms in the postictal period. 19 In contrast, our recordings demonstrate that persistently stable units can be found within seizures, suggesting that relatively few synchronously firing neurons in the SOZ are involved in seizure genesis. Around 30% of neurons significantly increased or decreased their firing at the seizure onset.…”

Low‐voltage fast seizures in humans begin with increased interneuron firing

“…30 It should be noted that our results differ from those obtained using microelectrode arrays implanted in human neocortex, which showed how in the ictal core, single units could not be discriminated during seizures. 32 The disparity is not due to electrode placement, because in our study, the ictal core would encompass the mesial–temporal SOZ and later some of the sites of spread in patients with MTLE (see Fig 6). 29 One reason that SUA analysis could be successfully performed in LFP recordings from the “ictal core” may be that in this previous study unit activity was analyzed during both the ictal onset pattern and the following clonic bursting.…”

Altered Oscillatory Dynamics of CA1 Parvalbumin Basket Cells during Theta–Gamma Rhythmopathies of Temporal Lobe Epilepsy

“…Timely recruitment of PV basket cells determine coordinated oscillations and spatial representation (Korotkova et al, 2010). Interestingly, we noted a nonsignificant decline of the SPW/ripple ratio in PV basket cells of TLE rats (Table 1), pointing to their ineffective activation by Schaffer collaterals, but this could also be reflecting a sorting collapse during fast ripples (Ibarz et al, 2010; Merricks et al, 2015). Actually, enhancement of the fast gamma band (90–140 Hz) in TLE rats supports this view (Fig.…”

“…7 D–F , blue), despite the fact that large-amplitude fast ripples typical of the TLE hippocampus compromised sorting during some events (Fig. 7 E ; Ibarz et al, 2010; Merricks et al, 2015). Actually, the SPW/ripple ratio (Materials and Methods) had a nonsignificant trend to lower values in putative PV basket cells from epileptic rats (Student’s t test, p = 0.0624), suggesting their weak feedforward activation by Schaffer collaterals.…”