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Reentrainment following phase shifts of the light-dark (LD) cycle is accelerated in Octodon degus in the presence of olfactory social cues (i.e., odors) produced by conspecifics. However, not all odors from conspecifics were effective in facilitating reentrainment after a phase advance. In the current experiments, we examined whether nonanimal odors, odors from another species, or conspecific odors, including those manipulated by steroid hormones, can cause the same increased reentrainment of wheel-running activity as odors from an intact, adult female degu. A variety of odors, each selected to probe a particular aspect of the reentrainment acceleration phenomenon, were presented to a group of phase-shifting female degus. The shifting females (test animals) responded to odors of intact, female degu donors with decreased reentrainment time, but odors of ovariectomized (OVX), OVX with a single hormone replacement capsule (estradiol or progesterone) or phase-shifting females had no effect. Multiple males were effective odor donors, whereas a single male was ineffective in earlier studies. Rats and cloves were not effective in accelerating reentrainment. Furthermore, odors from rats delayed reentrainment. We conclude that the odors that effectively accelerate degu reentrainment after a phase advance of the LD cycle are species specific. We also report that repeated phase shifts, followed by complete recovery of phase relationships, do not alter the rate of recovery from a phase shift over time. These data suggest that in O. degus, a social species, odors may reinforce and strengthen the salience of the photic zeitgeber and/or facilitate synchronization of rhythms between animals. circadian rhythm; degu; phase-shift; entrainment; nonphotic signals

Humans' closest living relatives are bonobos (Pan paniscus) and chimpanzees (Pan troglodytes), yet these great ape species differ considerably from each other in terms of social behavior. Bonobos are more tolerant of conspecifics in competitive contexts and often use sexual behavior to mediate social interactions. Chimpanzees more frequently employ aggression during conflicts and actively patrol territories between communities. Regulation of emotional responses is facilitated by the amygdala, which also modulates social decision-making, memory and attention. Amygdala responsiveness is further regulated by the neurotransmitter serotonin. We hypothesized that the amygdala of bonobos and chimpanzees would differ in its neuroanatomical organization and serotonergic innervation. We measured volumes of regions and the length density of serotonin transporter-containing axons in the whole amygdala and its lateral, basal, accessory basal and central nuclei. Results showed that accessory basal nucleus volume was larger in chimpanzees than in bonobos. Of particular note, the amygdala of bonobos had more than twice the density of serotonergic axons than chimpanzees, with the most pronounced differences in the basal and central nuclei. These findings suggest that variation in serotonergic innervation of the amygdala may contribute to mediating the remarkable differences in social behavior exhibited by bonobos and chimpanzees. [ABSTRACT FROM AUTHOR]

Neocortical development in humans is characterized by an extended period of synaptic proliferation that peaks in mid-childhood, with subsequent pruning through early adulthood, as well as relatively delayed maturation of neuronal arborization in the prefrontal cortex compared with sensorimotor areas. In macaque monkeys, cortical synaptogenesis peaks during early infancy and developmental changes in synapse density and dendritic spines occur synchronously across cortical regions. Thus, relatively prolonged synapse and neuronal maturation in humans might contribute to enhancement of social learning during development and transmission of cultural practices, including language. However, because macaques, which share a last common ancestor with humans ∼25 million years ago, have served as the predominant comparative primate model in neurodevelopmental research, the paucity of data from more closely related great apes leaves unresolved when these evolutionary changes in the timing of cortical development became established in the human lineage. To address this question, we used immunohistochemistry, electron microscopy, and Golgi staining to characterize synaptic density and dendritic morphology of pyramidal neurons in primary somatosensory (area 3b), primary motor (area 4), prestriate visual (area 18), and prefrontal (area 10) cortices of developing chimpanzees (/Pan troglodytes/). We found that synaptogenesis occurs synchronously across cortical areas, with a peak of synapse density during the juvenile period (3-5 y). Moreover, similar to findings in humans, dendrites of prefrontal pyramidal neurons developed later than sensorimotor areas. These results suggest that evolutionary changes to neocortical development promoting greater neuronal plasticity early in postnatal life preceded the divergence of the human and chimpanzee lineages. [ABSTRACT FROM AUTHOR]

We examined the distribution of neurons immunoreactive for neuropeptide Y ( NPY) in the posterior part of the superior temporal cortex ( Brodmann's area 22 or area Tpt) of humans and nonhuman haplorrhine primates. NPY has been implicated in learning and memory and the density of NPY-expressing cortical neurons and axons is reduced in depression, bipolar disorder, schizophrenia, and Alzheimer's disease. Due to the role that NPY plays in both cognition and neurodegenerative diseases, we tested the hypothesis that the density of cortical and interstitial neurons expressing NPY was increased in humans relative to other primate species. The study sample included great apes (chimpanzee and gorilla), Old World monkeys (pigtailed macaque, moor macaque, and baboon) and New World monkeys (squirrel monkey and capuchin). Stereologic methods were used to estimate the density of NPY-immunoreactive (-ir) neurons in layers I- VI of area Tpt and the subjacent white matter. Adjacent Nissl-stained sections were used to calculate local densities of all neurons. The ratio of NPY-ir neurons to total neurons within area Tpt and the total density of NPY-ir neurons within the white matter were compared among species. Overall, NPY-ir neurons represented only an average of 0.006% of the total neuron population. While there were significant differences among species, phylogenetic trends in NPY-ir neuron distributions were not observed and humans did not differ from other primates. However, variation among species warrants further investigation into the distribution of this neuromodulator system. Am. J. Primatol. 75:415-424, 2013. © 2012 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

The article focuses on a study which examined the expression of proteins that are localized in von economo neurons (VENs), namely activating-transcription factor 3 (ATF3), interleukin 4 receptor (IL4Rα), and neuromedin B (NMB). The neurons utilized include pyramidal, VEN, fork, enveloping and other mulipolar. Study authors found the presence of phylogenetic variation in the protein expression profiles of VENs.

Inhibitory GABAergic interneurons are important for shaping patterns of activity in neocortical networks. We examined the distributions of inhibitory interneuron subtypes in layer II/III of areas V1 and V2 in 18 genera of anthropoid primates including New World monkeys, Old World monkeys, and hominoids (apes and humans). Interneuron subtypes were identified by immunohistochemical staining for calbindin, calretinin, and parvalbumin and densities were quantified using the optical disector method. In both V1 and V2, calbindin-immunoreactive neuron density decreased disproportionately with decreasing total neuronal density. Thus, V1 and V2 of hominoids were occupied by a smaller percentage of calbindin-immunoreactive interneurons compared to monkeys who have greater overall neuronal densities. At the transition from V1 to V2 across all individuals, we found a tendency for increased percentages of calbindin-immunoreactive multipolar cells and calretinin-immunoreactive interneurons. In addition, parvalbumin-immunoreactive cell soma volumes increased from V1 to V2. These findings suggest that modifications of specific aspects of inhibition might be critical to establishing the receptive field properties that distinguish visual areas. Furthermore, these results show that phylogenetic variation exists in the microcircuitry of visual cortex that could have general implications for sensory processing. Copyright © 2007 S. Karger AG, Basel [ABSTRACT FROM AUTHOR]