Multisynaptic projections from the ventrolateral prefrontal cortex to the dorsal premotor cortex in macaques - anatomical substrate for conditional visuomotor behavior

• Published in: The European journal of neuroscience 2012-11, Vol.36 (10), p.3365-3375
• Main Authors: Takahara, Daisuke, Inoue, Ken-ichi, Hirata, Yoshihiro, Miyachi, Shigehiro, Nambu, Atsushi, Takada, Masahiko, Hoshi, Eiji
• Format: Article
• Language: English
• Subjects: Anatomy; Animals; Axons - physiology; Brain Mapping; Cell body; Cortex (cingulate); Cortex (motor); Cortex (prefrontal); Cortex (premotor); Cortex (visual); Female; Fluorescent Dyes; Macaca; Male; motor control; Motor Cortex - cytology; Motor Cortex - physiology; Nerve Net - cytology; Nerve Net - physiology; Nervous system; Neurons; oculomotor behavior; Prefrontal Cortex - cytology; Prefrontal Cortex - physiology; presupplementary motor area; Presynapse; Psychomotor Performance; Rabies; Rabies virus; sensorimotor integration; Synapses - physiology; Tracers; transneuronal transport
• ISSN: 0953-816X; 1460-9568
• DOI: 10.1111/j.1460-9568.2012.08251.x

Lines of evidence indicate that both the ventrolateral prefrontal cortex (vlPFC) (areas 45/12) and dorsal premotor cortex (PMd) (rostral F2 in area 6) are crucially involved in conditional visuomotor behavior, in which it is required to determine an action based on an associated visual object. However, virtually no direct projections appear to exist between the vlPFC and PMd. In the present study, to elucidate possible multisynaptic networks linking the vlPFC to the PMd, we performed a series of neuroanatomical tract‐tracing experiments in macaque monkeys. First, we identified cortical areas that send projection fibers directly to the PMd by injecting Fast Blue into the PMd. Considerable retrograde labeling occurred in the dorsal prefrontal cortex (dPFC) (areas 46d/9/8B/8Ad), dorsomedial motor cortex (dmMC) (F7 and presupplementary motor area), rostral cingulate motor area, and ventral premotor cortex (F5 and area 44), whereas the vlPFC was virtually devoid of neuronal labeling. Second, we injected the rabies virus, a retrograde transneuronal tracer, into the PMd. At 3 days after the rabies injections, second‐order neurons were labeled in the vlPFC (mainly area 45), indicating that the vlPFC disynaptically projects to the PMd. Finally, to determine areas that connect the vlPFC to the PMd indirectly, we carried out an anterograde/retrograde dual‐labeling experiment in single monkeys. By examining the distribution of axon terminals labeled from the vlPFC and cell bodies labeled from the PMd, we found overlapping labels in the dPFC and dmMC. These results indicate that the vlPFC outflow is directed toward the PMd in a multisynaptic fashion through the dPFC and/or dmMC. Both the ventrolateral prefrontal cortex (vlPFC) and the dorsal premotor cortex (PMd) are implicated in conditional visuomotor behavior, in which it is required to determine an action based on an associated visual object. However, virtually no direct projections appear to exist between vlPFC and PMd. Here we provide evidence that vlPFC outflow is directed toward PMd in a multisynaptic fashion through the dorsal prefrontal cortex (dPFC) and the dorsomedial motor cortex (dmMC).