1 2 3 Neurons with inverted tuning during the delay periods of working memory tasks in the 4 dorsal prefrontal and posterior parietal cortex

39 40 The dorsolateral prefrontal and posterior parietal cortex are two interconnected brain areas 41 that are co-activated in tasks involving functions such as spatial attention and working 42 memory. The response properties of neurons in the two areas are in many respects 43 indistinguishable, yet only prefrontal neurons are able to resist interference by distracting 44 stimuli when subjects are required to remember an initial stimulus. Several mechanisms have 45 been proposed that could account for this functional difference, including the existence of 46 specialized interneuron types, specific to the prefrontal cortex. Although such neurons with 47 inverted tuning during the delay period of a working memory task have been described in the 48 prefrontal cortex, no comparative data exist from other cortical areas that would establish a 49 unique prefrontal role. To test this hypothesis, we analyzed a large database of recordings 50 obtained in the dorsolateral prefrontal and posterior parietal cortex of the same monkeys, as 51 they performed working memory tasks. We found that in the prefrontal cortex neurons with 52 inverted tuning were more numerous and manifested unique properties. Our results give 53 credence to the idea that a division of labor exists between separate neuron types in the 54 prefrontal cortex and that this represents a functional specialization that is not present in its 55 cortical afferents. 56 57 58