No abstract

Neuronal activities of the anterior part of the inferior parietal lobule (area 7b or PF) were investigated in five awake Japanese monkeys. There were neurons which had specific combinations of receptive field (RF) locations, most typically in both the face and hand; we refer to the seas Face-Hand neurons. The most interesting property of the Face-Hand neurons is that some of these neurons responded to specific behavior executed with synergism between the face (especially the mouth) and hand movements; namely, face-hand coordinated behavior (e.g., eating behavior). We call these cells Face-Hand coordination neurons (52% of all the Face-Hand neurons). These neurons discharged more strongly when the animal executed face-hand coordinated behavior, especially eating behavior, than when somatosensory stimuli were given to RFs passively, or when face movements and hand movements were executed separately. We thus propose that the neuronal activities of area 7b are related to the representation of face-hand coordination.

Prion-like spreading of abnormal proteins is proposed to occur in neurodegenerative diseases, and the progression of α-synuclein (α-syn) deposits has been reported in the brains of animal models injected with synthetic α-syn fibrils or pathological α-syn prepared from patients with Parkinson's disease (PD) and dementia with Lewy bodies (DLB). However, α-syn transmission in nonhuman primates, which are more similar to humans, has not been fully clarified. Here, we injected synthetic human α-syn fibrils into the left striatum of a macaque monkey (Macaca fuscata). At 3 months after the injection, we examined neurodegeneration and α-syn pathology in the brain using α-syn epitope-specific antibodies, antiphosphorylated α-syn antibodies (pSyn#64 and pSer129), antiubiquitin antibodies, and anti-p62 antibodies. Immunohistochemical examination with pSyn#64, pSer129, and α-syn epitope-specific antibodies revealed Lewy bodies, massive α-syn-positive neuronal intracytoplasmic inclusions (NCIs), and neurites in the left putamen. These inclusions were also positive for ubiquitin and p62. LB509, a human-specific α-syn antibody targeting amino acid residues 115-122, showed limited immunoreactivity around the injection site. The left substantia nigra (SN) and the bilateral frontal cortex also contained some NCIs and neurites. The left hemisphere, including parietal/temporal cortex presented sparse α-syn pathology, and no immunoreactivity was seen in olfactory nerves, amygdala, hippocampus, or right parietal/temporal cortex. Neuronal loss and gliosis in regions with α-syn pathology were mild, except for the left striatum and SN. Our results indicate that abnormal α-syn fibrils propagate throughout the brain of M. fuscata via projection, association, and commissural fibers, though the progression of α-syn pathology is limited.

Eye contact and pointing are typical gestures in order to direct another individual's attention toward a target. We previously investigated on Japanese monkeys whether joint attention ability encouraged by eye contact and pointing was associated with the imitation of human's actions. The monkeys with the joint attention skills showed the imitation of human's actions. In the current study, we investigated on a monkey whether joint attention ability also facilitated the imitation of human body-movements. Results showed that the monkey being taught eye contact and pointing showed the imitation of human body-movements. These results suggest that the monkeys have basic potential for following another individual's motion, and that what imitation expresses depends on where the monkeys are paying attention. Thus, eye contact and pointing are suitable for directing the monkey's attention toward the human.