Brain-wide single-neuron bases of working memory for sounds in humans

In order to understand the constantly changing acoustic world our brains must maintain elements of auditory scenes in memory. The neural mechanisms for this fundamental process remain unclear. Here, we report human intracranial recordings of 1269 single neurons, recorded from various brain structures while participants performed a non-verbal auditory working memory task that required adjusting a tone frequency to match a target. We found neurons within regions including hippocampus, insula and cingulate cortex, for which firing rates were modulated at various phases of the task, particularly throughout maintenance and during active tone adjustment. For the majority of the neurons modulated during maintenance, relative to baseline, there was a striking suppression of activity rather than increased activity, though response types were heterogeneous both within and between regions. Across the entire neuronal population, state-space analyses demonstrated that the different task phases were clearly separable. Behaviorally, there was an increased number of neurons were modulated at the beginning of the maintenance phase when participants performed better. These data support the existence of a distributed neural code for auditory working memory that determines related behavior.