TY - JOUR T1 - The geometry of abstraction in hippocampus and pre-frontal cortex JF - bioRxiv DO - 10.1101/408633 SP - 408633 AU - Silvia Bernardi AU - Marcus K. Benna AU - Mattia Rigotti AU - Jérôme Munuera AU - Stefano Fusi AU - C. Daniel Salzman Y1 - 2018/01/01 UR - http://biorxiv.org/content/early/2018/12/09/408633.abstract N2 - Abstraction can be defined as a cognitive process that identifies common features - abstract variables, or concepts - shared by many examples. Such conceptual knowledge enables subjects to generalize upon encountering new examples, an ability that supports inferential reasoning and cognitive flexibility. To confer the ability to generalize, the brain must represent variables in a particular ‘abstract’ format. Here we show how to construct neural representations that encode multiple variables in an abstract format simultaneously, and we characterize their geometry. Neural representations conforming to this geometry were observed in dorsolateral pre-frontal cortex, anterior cingulate cortex and the hippocampus in monkeys performing a serial reversal-learning task. Similar representations are observed in a simulated multi-layer neural network trained with back-propagation. These findings provide a novel framework for characterizing how different brain areas represent abstract variables that are critical for flexible conceptual generalization. ER -