Cross-region neuron co-firing mediated by ripple oscillations supports distributed working memory representations

High-frequency (~90-Hz) ripple oscillations may promote integrative processing in mammalian brains. Co-occurrence of ripple oscillations has been associated with enhanced temporal binding of neural activity between nearby human cortical neurons, but whether co-ripple facilitation of neuronal coupling supports cognitive processing or occurs at greater distances remains unclear. Here we analyze intracranial recordings from patients implanted with microwire electrodes in the hippocampus, amygdala, ventromedial prefrontal cortex, anterior cingulate cortex and pre-supplementary motor area, bilaterally, during a working memory task. We demonstrate that ripple rates increase in all recorded regions during encoding, maintenance and retrieval. Co-occurrence of ripples increases between brain regions, associated with ~30% increases in cross-region co-firing, without decrement over distances up to 220 mm. Cross-regional co-rippling and associated co-firing scale with memory load during maintenance and retrieval. During retrieval, co-ripples promote reinstatement of stimulus-specific, long-distance co-firing patterns observed during encoding, especially during rapid recognition. Co-occurring ripple oscillations thus coordinate long-range, stimulus-specific neural co-firing supporting distributed representations during human cognition.