Cortical basis for skilled vocalization.

Marmosets display remarkable vocal motor abilities. Macaques do not. What is it about the marmoset brain that enables its skill in the vocal domain? We examined the cortical control of a laryngeal muscle that is essential for vocalization in both species.

The Cortical Motor Areas and the Emergence of Motor Skills: A Neuroanatomical Perspective.

What changes in neural architecture account for the emergence and expansion of dexterity in primates? Dexterity, or skill in performing motor tasks, depends on the ability to generate highly fractionated patterns of muscle activity. It also involves the spatiotemporal coordination of activity in proximal and distal muscles across multiple joints. Many motor skills require the generation of complex movement sequences that are only acquired and refined through extensive practice.

Posterior parietal cortex contains a command apparatus for hand movements.

Mountcastle and colleagues proposed that the posterior parietal cortex contains a "command apparatus" for the operation of the hand in immediate extrapersonal space [Mountcastle et al. (1975) 38(4):871-908]. Here we provide three lines of converging evidence that a lateral region within area 5 has corticospinal neurons that are directly linked to the control of hand movements.

Subdivisions of primary motor cortex based on cortico-motoneuronal cells.

We used retrograde transneuronal transport of rabies virus from single muscles of rhesus monkeys to identify cortico-motoneuronal (CM) cells in the primary motor cortex (M1) that make monosynaptic connections with motoneurons innervating shoulder, elbow, and finger muscles. We found that M1 has 2 subdivisions. A rostral region lacks CM cells and represents an "old" M1 that is the standard for many mammals.

Muscle representation in the macaque motor cortex: an anatomical perspective.

How are the neurons that directly influence the motoneurons of a muscle distributed in the primary motor cortex (M1)? To answer this classical question we used retrograde transneuronal transport of rabies virus from single muscles of macaques. This enabled us to define cortico-motoneuronal (CM) cells that make monosynaptic connections with the motoneurons of the injected muscle. We examined the distribution of CM cells that project to motoneurons of three thumb and finger muscles.