The Dostoyevsky effect: epileptogenesis and memory enhancement after kindling stimulation in the primate basolateral amygdala.

Kindling is an electrical stimulation technique used to lower the threshold for epileptogenic activity in the brain. It can also be used as a tool to investigate electrophysiologic alterations that occur as a result of seizures. Epileptiform activity, like seizures and after-discharges (AD; evoked epileptiform activity), commonly cause memory impairment but rarely, can elicit vivid memory retrieval. We kindled the basolateral amygdala of a non-human primate (NHP) once weekly and had him perform a spatial memory task in a 3D virtual environment before, during and after kindling. AD were associated with an initial average performance increase of 46.6%. The enhancement which followed AD persisted up to 2 days. Memory task performance enhancement was accompanied by significant resetting of hippocampal theta oscillations and robust hippocampal potentiation as measured by field evoked potentials. However, neither lasted throughout the duration of performance enhancement. Sharp-wave ripples (SWR), a local field event that supports episodic memory, were generated more often throughout the period of enhancement. SWR rate increased from 14.38 SWR per min before kindling to 24.22 SWR per min after kindling on average. Our results show that kindling can be associated with improved memory. Memory function appears to depend on the particular induction circuit and the resultant excitation/inhibition ratio of the mesial temporal lobe network. Investigating the electrophysiologic underpinnings of this observed memory enhancement is an important step towards understanding the network alterations that occur after seizures and stimulation.Clinical Relevance- Our findings provide new insight into the effects of kindling stimulation in the primate brain. Kindling can cause increase MTL synchrony and the frequency of spontaneous seizures in a primate. This work highlights important considerations for therapeutic deep brain stimulation.