Learning and language in the unconscious human hippocampus.
bioRxiv : the preprint server for biology – April 09, 2025
Source: PubMed
Summary
Your brain keeps learning, even when you're completely unconscious. Scientists discovered that hippocampal neurons - our brain's memory center - can detect unusual sounds and process language during general anesthesia. Using advanced recording techniques, they found these neurons not only recognize patterns but also predict upcoming words, suggesting complex information processing continues even without consciousness.
Abstract
Consciousness is a fundamental component of cognition, 1 but the degree to which higher-order perception relies on it remains disputed. 2,3 Here we demonstrate the persistence of learning, semantic processing, and online prediction in individuals under general anesthesia-induced loss of consciousness. 4,5 Using high-density Neuropixels microelectrodes 6 to record neural activity in the human hippocampus while playing a series of tones to anesthetized patients, we found that hippocampal neurons could reliably detect oddball tones. This effect size grew over the course of the experiment (∼10 minutes), consistent with learning effects. A biologically plausible recurrent neural network model showed that learning and oddball representation are an emergent property of flexible tone discrimination. Last, when we played language stimuli, single units and ensembles carried information about the semantic and grammatical features of natural speech, even predicting semantic information about upcoming words. Together these results indicate that in the hippocampus, which is anatomically and functionally distant from primary sensory cortices, 7 complex processing of sensory stimuli occurs even in the unconscious state.