Closed-Loop Interruption of Hippocampal Ripples through Fornix Stimulation in the Non-Human Primate.

•Stimulation to fornix electrodes can rapidly alter hippocampal activity in the macaque brain.•Closed-loop ripple detection leading to fornix stimulation interrupted ongoing ripples.•Ripple interruption transiently suppressed multi-unit activity at the hippocampal recording sites.•Suppressed multi-unit activity suggests that stimulation could alter local hippocampal computations during ripples, such as cell assembly replay.