Memory retrieval under the control of the prefrontal cortex

Memory retrieval is a process wherein a distributed neural network reactiva tes the brain's representation of past experiences. Sensory long-term memor y is represented among: a population of neurones in the modality-specific p osterior association cortex. The coded representation of memory earn be ret rieved by interactions of hierarchically different cortical areas along bot tom-up and top-down anatomical connections. We examined the function of the prefrontal cortex in memory retrieval by two different approaches. Firstly , a meta-analysis of brain imaging studies revealed that the prefrontal cor tex is reliably activated by memory retrieval in humans. Secondly, in order to determine the causal relationship between the prefrontal activations an d memory retrieval, we designed a new experimental paradigm using posterior -split-brain monkeys. Following section of the splenium of the corpus callo sum and the anterior commissure, visual stimulus-stimulus association learn ing within one hemisphere did nor transfer to the other. Nevertheless, when a visual cue was presented to one hemisphere, the prefrontal cortex could instruct the contralateral hemisphere to retrieve the correct stimulus spec ified by the cue. These findings suggest that the prefrontal cortex can reg ulate the recall of long-term memory in the absence of bottom-up sensory in puts.