Search

The brain in the genus Homo expanded rapidly during evolution, accelerated by a reciprocated interaction between neural, cognitive, and ecological niches (triadic niche construction, or TNC). This biologically costly expansion incubated latent cognitive capabilities that, with a quick and inexpensive rewiring of brain areas in a second phase of TNC, provided the basis for Homo sapiens specific abilities. The neural demands for perception of the human body in interaction with tools and the environment required highly integrated sensorimotor domains, inducing the parietal lobe expansion seen in humans. These newly expanded brain areas allowed connecting the sensations felt in the body to the actions in the world through the cognitive function of "projection". In this opinion article, we suggest that as a relationship of equivalence between body parts, tools and their external effects was established, mental mechanisms of self‐objectification might have emerged as described previously, grounding notions of spatial organization, idealized objects, and their transformations, as well as socio‐emotional states in the sensing agent through a self‐in‐the‐world map. Therefore, human intelligence and its features such as symbolic thought, language, mentalizing, and complex technical and social behaviors could have stemmed from the explicit awareness of the causal relationship between the self and intentional modifications to the environment. [ABSTRACT FROM AUTHOR]

Key points The cortical mechanisms of grasping have been extensively studied in macaques and humans; here, we investigated whether common marmosets could rely on similar mechanisms despite strong differences in hand morphology and grip diversity., We recorded electrocorticographic activity over the sensorimotor cortex of two common marmosets during the execution of different grip types, which allowed us to study cortical activity (power spectrum) and physiologically inferred connectivity (phase-slope index)., Analyses were performed in beta (16-35 Hz) and gamma (75-100 Hz) frequency bands and our results showed that beta power varied depending on grip type, whereas gamma power displayed clear epoch-related modulation., Strength and direction of inter-area connectivity varied depending on grip type and epoch., These findings suggest that fundamental control mechanisms are conserved across primates and, in future research, marmosets could represent an adequate model to investigate primate brain mechanisms., Abstract The cortical mechanisms of grasping have been extensively studied in macaques and humans. Here, we investigated whether common marmosets could rely on similar mechanisms despite striking differences in manual dexterity. Two common marmosets were trained to grasp-and-pull three objects eliciting different hand configurations: whole-hand, finger and scissor grips. The animals were then chronically implanted with 64-channel electrocorticogram arrays positioned over the left premotor, primary motor and somatosensory cortex. Power spectra, reflecting predominantly cortical activity, and phase-slope index, reflecting the direction of information flux, were studied in beta (16-35 Hz) and gamma (75-100 Hz) bands. Differences related to grip type, epoch (reach, grasp) and cortical area were statistically assessed. Results showed that whole-hand and scissor grips triggered stronger beta desynchronization than finger grip. Task epochs clearly modulated gamma power, especially for finger and scissor grips. Considering effective connectivity, finger and scissor grips evoked stronger outflow from primary motor to premotor cortex, whereas whole-hand grip displayed the opposite pattern. These findings suggest that fundamental control mechanisms, relying on adjustments of cortical activity and connectivity, are conserved across primates. Consistently, marmosets could represent a good model to investigate primate brain mechanisms. [ABSTRACT FROM AUTHOR]

Cadherin is a cell adhesion molecule widely expressed in the nervous system. Previously, we analyzed the expression of nine classic cadherins ( Cdh4, Cdh6, Cdh7, Cdh8, Cdh9, Cdh10, Cdh11, Cdh12, and Cdh20) and T-cadherin ( Cdh13) in the developing postnatal common marmoset ( Callithrix jacchus) brain, and found differential expressions between mice and marmosets. In this study, to explore primate-specific cadherin expression at the embryonic stage, we extensively analyzed the expression of these cadherins in the developing embryonic marmoset brain. Each cadherin showed differential spatial and temporal expression and exhibited temporally complicated expression. Furthermore, the expression of some cadherins differed from that in rodent brains, even at the embryonic stage. These results suggest the possibility that the differential expressions of diverse cadherins are involved in primate specific cortical development, from the prenatal to postnatal period. [ABSTRACT FROM AUTHOR]

Japanese macaques are able to learn how to use rakes to take food after only a few weeks of training. Since tool-use training induced rapid morphological changes in some restricted brain areas, this system will be a good model for studying the neural basis of plasticity in human brains. To examine the mechanisms of tool-use associated brain expansion on the molecular and cellular level, here, we performed comprehensive analysis of gene expressions with microarray. We identified various transcripts showing differential expression between trained and untrained monkeys in the region around the lateral and intraparietal sulci. Among candidates, we focused on genes related to synapse formation and function. Using quantitative reverse transcription-polymerase chain reaction and histochemical analysis, we confirmed at least three genes ( ADAM19, SPON2, and WIF1) with statistically different expression levels in neurons and glial cells. Comparative analysis revealed that tool use-associated genes were more obviously expressed in macaque monkeys than marmosets or mice. Thus, our findings suggest that cognitive tasks induce structural changes in the neocortex via gene expression, and that learning-associated genes innately differ with relation to learning ability. [ABSTRACT FROM AUTHOR]

Periostin ( POSTN or osteoblast specific factor) is an extracellular matrix protein originally identified as a protein highly expressed in osteoblasts. Recently, periostin has been reported to function in axon regeneration and neuroprotection. In the present study, we focused on periostin function in cortical evolution. We performed a comparative gene expression analysis of periostin between rodents (mice) and primates (marmosets and macaques). Periostin was expressed at higher levels in the primate cerebral cortex compared to the mouse cerebral cortex. Furthermore, we performed overexpression experiments of periostin in vivo and in vitro. Periostin exhibited neurite outgrowth activity in cortical neurons. These results suggested the possibility that prolonged and increased periostin expression in the primate cerebral cortex enhances the cortical plasticity of the mammalian cerebral cortex. [ABSTRACT FROM AUTHOR]

The middle temporal visual area ( MT, also known as V5) is a visual association area that is particularly evolved in the primate brain. The MT receives input from the primary visual area (V1), constitutes part of the dorsal visual pathway, and plays an essential role in processing motion. Connections between the MT and V1 in the primate brain are formed after birth, and are related to the maturation of visual system. However, it remains to be determined what molecular mechanisms control the formation and maturation of the visual system. Cadherins are transmembrane proteins, originally isolated as cell adhesion molecules, which have multiple roles in synapse formation and function. To investigate potential involvement of cadherins in development of the primate visual system, we examined type II cadherin expression ( cadherin-6, -8, -12) in cortical and thalamic visual areas of pre- and postnatal brains of the common marmoset ( Callithrix jacchus). In the prenatal brain, cadherin-6 was dominantly expressed in the pulvino- MT pathway whereas cadherin-8 was dominant in the lateral geniculate nucleus ( LGN)-V1 pathway. During postnatal development, there was a downregulation of cadherin-6 and upregulation of cadherin-8 expression in the MT. The timing of this cadherin exchange preceded the development of V1- MT connections. Our results suggest the possibility that changes in cadherin expression are involved in the development of the primate visual system, and that a switch in cadherin expression may be a general mechanism to control neural plasticity of highly cognitive abilities. [ABSTRACT FROM AUTHOR]

ABSTRACT Cadherins are cell adhesion molecules widely expressed in the nervous system, where they play various roles in neural patterning, nuclei formation, axon guidance, and synapse formation and function. Although many published articles have reported on cadherin expression in rodents and ferrets, there are limited data on their expression in primate brains. In this study, in situ hybridization analysis was performed for 10 cadherins [nine classic cadherins ( Cdh4, - 6, - 7, - 8, - 9, - 10, - 11, - 12, and - 20) and T-cadherin ( Cdh13)] in the developing postnatal telencephalon of the common marmoset ( Callithrix jacchus). Each cadherin showed broad expression in the cerebral cortex, basal ganglia, amygdala, and hippocampus, as previously shown in the rodent brain. However, detailed expression patterns differed between rodents and marmosets. In contrast to rodents, cadherin expression was reduced overall and localized to restricted areas of the brain during the developmental process, suggesting that cadherins are more crucially involved in developmental or maturation processes rather than in neural functioning. These results also highlight the possibility that restricted/less redundant cadherin expression allows primate brains to generate functional diversity among neurons, allowing morphological and functional differences between rodents and primates. J. Comp. Neurol. 521:4027-4060, 2013. © 2013 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

Body size can vary throughout a person's lifetime, inducing plasticity of the internal body representation. Changes in horizontal width accompany those in dorsal-to-ventral thickness. To examine differences in the perception of different body axes, neural correlates of own-body-size perception in the horizontal and dorsoventral directions were compared using functional magnetic resonance imaging. Original and distorted (−30, −10, +10 and +30%) images of the neck-down region of their own body were presented to healthy female participants, who were then asked whether the images were of their own body or not based explicitly on body size. Participants perceived body images distorted by −10% as their own, whereas those distorted by +30% as belonging to others. Horizontal width images yielded slightly more subjective own-body perceptions than dorsoventral thickness images did. Subjective perception of own-body size was associated with bilateral inferior parietal activity. In contrast, other-body judgments showed pre-supplementary motor and superior parietal activity. Expansion in the dorsoventral direction was associated with the left fusiform gyrus and the right inferior parietal lobule, whereas horizontal expansions were associated with activity in the bilateral somatosensory area. These results suggest neural dissociations between the two body axes: dorsoventral images of thickness may require visual processing, whereas bodily sensations are involved in horizontal body-size perception. Somatosensory rather than visual processes can be critical for the assessment of frontal own-body appearance. Visual body thickness and somatosensory body width may be integrated to construct a whole-body representation. [ABSTRACT FROM AUTHOR]

We can control distant tools effectively by manipulating other objects as controllers in various remote-operated ways, even when the two mechanics are altered. To master the remote operation, we may rely on internal representation to organize individual moves of the controller and tool into a set of sequences by mapping the motor space among hand, controller and tool as a continuum. The present study confirmed that monkeys could also organize a sequence by mapping such a motor space or reorganize by remapping even after alteration. In addition, to investigate the neural substrates underlying such mapping/remapping, we measured the regional cerebral blood flow of two monkeys during joystick-controlled operation with alterable function of mechanics using positron emission tomography with . The monkeys were scanned during three different tasks produced by altering the directional gains of the x or y axis of the joystick — the two mechanics are congruent (standard task) and not congruent (reversed in the X or Y axis, X reverse or Y reverse task, respectively). Compared with random movement of the joystick as the control task, increased activities were detected in the prefrontal cortex, higher-ordered motor cortex, posterior parietal cortex and cerebellum during the standard task. Common brain areas during performance of the X reverse and Y reverse task were identified as showing almost the same pattern as during the standard task. These shared areas may not simply be associated with organization of individual motor imagery, but also with context-dependent processing of reorganization based on current functions by means of internal representation. [ABSTRACT FROM AUTHOR]