How do the layered circuits of prefrontal and motor cortex carry out working memory storage, sequence learning, and voluntary sequential item selection and performance? A neural model called LIST PARSE is presented to explain and quantitatively simulate cognitive data about both immediate serial recall and free recall, including bowing of the serial position performance curves, error-type distributions, temporal limitations upon recall, and list length effects. The model also qualitatively explains cognitive effects related to attentional modulation, temporal grouping, variable presentation rates, phonemic similarity, presentation of non-words, word frequency/item familiarity and list strength, distracters and modality effects. In addition, the model quantitatively simulates neurophysiological data from the macaque prefrontal cortex obtained during sequential sensory-motor imitation and planned performance. The article further develops a theory concerning how the cerebral cortex works by showing how variations of the laminar circuits that have previously clarified how the visual cortex sees can also support cognitive processing of sequentially organized behaviors. 2
INTRODUCTIONIntelligent behavior depends upon the capacity to think about, plan, execute, and evaluate sequences of events. Whether we learn to understand and speak a language, solve a mathematics problem, cook an elaborate meal, or merely dial a phone number, multiple events in a specific temporal order must somehow be kept in mind temporarily in working memory. Once events are stored temporarily in a working memory, they are then grouped, or chunked, through learning into unitized representations that encode whole sequences of events; e.g., word and action sequences. How these working memory sequences and unitized plans interact during cognitive information processing and motor performance remains one of the most important problems confronting cognitive scientists and neuroscientists.This article introduces the LIST PARSE (Laminar Integrated Storage of Temporal Patterns for Associative Retrieval, Sequencing and Execution) model, which proposes how the layered circuits of prefrontal and motor cortex may be organized to achieve processes of working memory storage, sequence learning, and motor planning and execution during both cognitive and sensory-motor tasks. A schematic of the model is shown in Figure 1. The model makes predictions about the laminar organization of such cortical circuits that go beyond present neurophysiological and anatomical knowledge. It formulates these predictions by integrating several sorts of convergent constraints: extensive behavioral and neuroimaging data about cognitive information processing in humans; behavioral and neurobiological data about sensorymotor storage and performance of familiar sequential actions in monkeys; anatomical data about the laminar circuits that are shared by granular neocortical areas and connectivity specific to the lateral prefrontal cortex; laminar models of visual cortex that can e...