Phase transitions of brain evolution that produced human language and beyond.

The brain capacity of human ancestors underwent two phase transitions, which were supported by preadaptations during the animal protolanguage period, resulting in the emergence of human language. The transitions were (1) the emergence of the primate cerebral cortex, with its unique characteristic of additional cortical areas together with size expansion, and (2) the replacement of natural selection as the main evolutionary mechanism by triadic niche construction, an interactive expansion of ecological-, neural-, and cognitive-niches. These phase transitions accelerated the expansion of the hominid brain, exceeding the neural capacity threshold required for the emergence of language.

Neural Representation of Overlapping Path Segments and Reward Acquisitions in the Monkey Hippocampus.

Disambiguation of overlapping events is thought to be the hallmark of episodic memory. Recent rodent studies have reported that when navigating overlapping path segments in the different routes place cell activity in the same overlapping path segments were remapped according to different goal locations in different routes. However, it is unknown how hippocampal neurons disambiguate reward delivery in overlapping path segments in different routes.

A Markerless 3D Computerized Motion Capture System Incorporating a Skeleton Model for Monkeys.

In this study, we propose a novel markerless motion capture system (MCS) for monkeys, in which 3D surface images of monkeys were reconstructed by integrating data from four depth cameras, and a skeleton model of the monkey was fitted onto 3D images of monkeys in each frame of the video. To validate the MCS, first, estimated 3D positions of body parts were compared between the 3D MCS-assisted estimation and manual estimation based on visual inspection when a monkey performed a shuttling behavior in which it had to avoid obstacles in various positions. The mean estimation error of the positions of body parts (3-14 cm) and of head rotation (35-43°) between the 3D MCS-assisted and manual estimation were comparable to the errors between two different experimenters performing manual estimation.

Comparative anatomy of the arm muscles of the Japanese monkey (Macaca fuscata) with some comments on locomotor mechanics and behavior.

Background: The anatomical literature on the genus Macaca has focused mainly on the rhesus monkey. However, some aspects in the positional behaviors of the Japanese monkey may be different from those in rhesus monkey, suggesting that the anatomical details of these species are divergent.

Methods: Four thoracic limbs of Macaca fuscata adults were dissected.

Morphometric and statistical analysis of the palmaris longus muscle in human and non-human primates.

The palmaris longus is considered a phylogenetic degenerate metacarpophalangeal joint flexor muscle in humans, a small vestigial forearm muscle; it is the most variable muscle in humans, showing variation in position, duplication, slips and could be reverted. It is frequently studied in papers about human anatomical variations in cadavers and in vivo, its variation has importance in medical clinic, surgery, radiological analysis, in studies about high-performance athletes, in genetics and anthropologic studies. Most studies about palmaris longus in humans are associated to frequency or case studies, but comparative anatomy in primates and comparative morphometry were not found in scientific literature.