Persistent Single-Neuron Activity during Working Memory in the Human Medial Temporal Lobe

Working memory is an essential component of human cognition. Persistent activity related to working memory has been reported in many brain areas, including the inferior temporal and prefrontal cortex [1–8]. The medial temporal lobe (MTL) contains “concept cells” that respond invariantly to specific individuals or places whether presented as images, text, or speech [9, 10]. It is unknown, however, whether the MTL also participates in working memory processes. We thus sought to determine whether human MTL neurons respond to images held in working memory. We recorded from patients with chronically intractable epilepsy as they performed a task that required them to remember three or four sequentially presented pictures across a brief delay. 48% of visually selective neurons continued to carry image-specific information after image offset, but most ceased to encode previously presented images after a subsequent presentation of a different image. However, 8% of visually selective neurons encoded previously presented images during a final maintenance period, despite presentation of further images in the intervening interval. Population activity of stimulus-selective neurons predicted behavioral outcome in terms of correct and incorrect responses. These findings indicate that the MTL is part of a brain-wide network for working memory. •MTL neuronal responses decay after stimulus offset and are blocked by subsequent stimuli•MTL delay period activity reflects the contents of working memory•Activity of MTL neurons predicts successful working memory performance•The MTL is part of a brain-wide network for working memory Kornblith et al. investigate the activity of human MTL neurons during a working memory (WM) task. Visual responses decayed slowly after image offset and were blocked by subsequent stimuli. However, some neurons showed stimulus-selective activity during WM maintenance that predicted task performance. The MTL is part of a brain-wide network for WM.