Figure 1.

A. The reciprocal, parallel, visual and auditory cortical networks connecting with dlPFC. More ventral PFC regions connect with limbic areas subserving emotion (not shown). This figure is based on the work of Goldman-Rakic, as summarized in Arnsten, 2003 (Arnsten, 2003). B. The oculomotor delayed response (ODR) test of spatial working memory. For each trial, the monkey fixates on a central point, initiating the brief presentation (0.5s) of a cue in 1 of 8 locations. A delay period ensues (2.5–8s) in which the monkey must remember the spatial location until the fixation point extinguishes, and the monkey must make a saccade to the correct location to receive juice reward. The cued position randomly changes over hundred of trials, thus generating high levels of proactive interference. C. Cue, Delay and Response cells recorded from area 46 of the monkey dlPFC as a monkey performs the ODR task, and the corresponding microcircuitry thought to underlie physiological responses. (Goldman-Rakic, 1995). Cue cells fire during the presentation of the cue and stop firing during the Delay period. Delay cells often fire to the cue (and/or to the saccadic response), but are noted for their ability to maintain persistent firing across the delay period. Delay cells are usually spatially tuned, firing across the delay period for the neuron’s preferred direction, but decreasing firing for all other nonpreferred directions (the preferred direction for this Delay cell is indicated by a red asterisk). The microcircuits underlying Delay cell firing reside in deep layer III (and possibly in layer V as well) and are described in detail in the text. In contrast to Delay cells, Response cells are often inhibited during the delay period and instead fire leading up to, during, and/or after the motor response, initiating action and/or providing feedback. These neurons are thought to reside in layer V.