Categorization of behavioural sequences in the prefrontal cortex

Although it has long been thought that the prefrontal cortex of primates is involved in the integrative regulation of behaviours(1-4), the neural architecture underlying specific aspects of cognitive behavioural planning has yet to be clarified(5-8). If subjects are required to remember a large number of complex motor sequences and plan to execute each of them individually, categorization of the sequences according to the specific temporal structure inherent in each subset of sequences serves to facilitate higher-order planning based on memory. Here we show, using these requirements, that cells in the lateral prefrontal cortex selectively exhibit activity for a specific category of behavioural sequences, and that categories of behaviours, embodied by different types of movement sequences, are represented in prefrontal cells during the process of planning. This cellular activity implies the generation of neural representations capable of storing structured event complexes at an abstract level, exemplifying the development of macro-structured action knowledge in the lateral prefrontal cortex(9).