Linked Variants Are Associated with Social Behavior Differences in Bonobos ().

Single-nucleotide polymorphisms (SNPs) in forkhead box protein P2 () and oxytocin receptor () genes have been associated with linguistic and social development in humans, as well as to symptom severity in autism spectrum disorder (ASD). Studying biobehavioral mechanisms in the species most closely related to humans can provide insights into the origins of human communication, and the impact of genetic variation on complex behavioral phenotypes. Here, we aimed to determine if bonobos () exhibit individual variation in and loci that have been associated with human social development and behavior.

The AliveCor KardiaMobile ECG device allows electrocardiogram assessment in awake bonobos (Pan paniscus).

Objective: To determine the diagnostic utility of a smartphone-based ECG device (Alivecor KardiaMobile) in awake bonobos (Pan paniscus).

Animals: 7 adult bonobos in human care.

Procedures: Bonobos were trained with positive reinforcement to hold 1 finger from each hand onto the KardiaMobile sensors for 30 seconds to obtain an ECG reading.

Comparison of bonobo and chimpanzee brain microstructure reveals differences in socio-emotional circuits.

Despite being closely related, bonobos and chimpanzees exhibit several behavioral differences. For instance, studies indicate that chimpanzees are more aggressive, territorial, and risk-taking, while bonobos exhibit greater social tolerance and higher rates of socio-sexual interactions. To elucidate the potential neuroanatomical variation that accompanies these differences, we examined the microstructure of selected brain areas by quantifying the neuropil fraction, a measure of the relative tissue area occupied by structural elements of connectivity (e.

Changes in Frontoparietotemporal Connectivity following Do-As-I-Do Imitation Training in Chimpanzees ( Pan troglodytes).

Human imitation is supported by an underlying "mirror system" principally composed of inferior frontal, inferior parietal, and superior temporal cortical regions. Across primate species, differences in frontoparietotemporal connectivity have been hypothesized to explain phylogenetic variation in imitative abilities. However, if and to what extent these regions are involved in imitation in nonhuman primates is unknown.

Neocortical grey matter distribution underlying voluntary, flexible vocalizations in chimpanzees.

Vocal learning is a key property of spoken language, which might also be present in nonhuman primate species, such as chimpanzees (Pan troglodytes), to a limited degree. While understanding the origins of vocal learning in the primate brain may help shed light on the evolution of speech and language, little is still known regarding the neurobiological correlates of vocal flexibility in nonhuman primates. The current study used voxel-based morphometry (VBM) to assess whether the cerebral cortex of captive chimpanzees that learned to voluntarily produce sounds to attract the attention of a human experimenter (attention-getting sounds) differs in grey matter distribution compared to chimpanzees that do not exhibit this behavior.

Differential serotonergic innervation of the amygdala in bonobos and chimpanzees.

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.

Multimodal communication in chimpanzees.

A fundamental characteristic of human language is multimodality. In other words, humans use multiple signaling channels concurrently when communicating with one another. For example, people frequently produce manual gestures while speaking, and the words a person perceives are impacted by visual information.

Delay of gratification is associated with white matter connectivity in the dorsal prefrontal cortex: a diffusion tensor imaging study in chimpanzees (Pan troglodytes).

Individual variability in delay of gratification (DG) is associated with a number of important outcomes in both non-human and human primates. Using diffusion tensor imaging (DTI), this study describes the relationship between probabilistic estimates of white matter tracts projecting from the caudate to the prefrontal cortex (PFC) and DG abilities in a sample of 49 captive chimpanzees (Pan troglodytes). After accounting for time between collection of DTI scans and DG measurement, age and sex, higher white matter connectivity between the caudate and right dorsal PFC was found to be significantly associated with the acquisition (i.

Why vocal production of atypical sounds in apes and its cerebral correlates have a lot to say about the origin of language.

Ackermann et al. mention the "acquisition of species-atypical sounds" in apes without any discussion. In our commentary, we demonstrate that these atypical sounds in chimpanzees not only include laryngeal sounds, but also have a major significance regarding the origins of language, if we consider looking at their context of use, their social properties, their relations with gestures, their lateralization, and their neurofunctional correlates as well.

Vocal learning of a communicative signal in captive chimpanzees, Pan troglodytes.

We hypothesized that chimpanzees could learn to produce attention-getting (AG) sounds via positive reinforcement. We conducted a vocal assessment in 76 captive chimpanzees for their use of AG sounds to acquire the attention of an otherwise inattentive human. Fourteen individuals that did not produce AG sounds during the vocal assessment were evaluated for their ability to acquire the use of an AG sound through operant conditioning and to employ these sounds in an attention-getting context.

Using naturalistic utterances to investigate vocal communication processing and development in human and non-human primates.

Humans and several non-human primates possess cortical regions that are most sensitive to vocalizations produced by their own kind (conspecifics). However, the use of speech and other broadly defined categories of behaviorally relevant natural sounds has led to many discrepancies regarding where voice-sensitivity occurs, and more generally the identification of cortical networks, "proto-networks" or protolanguage networks, and pathways that may be sensitive or selective for certain aspects of vocalization processing. In this prospective review we examine different approaches for exploring vocal communication processing, including pathways that may be, or become, specialized for conspecific utterances.

Initiation of joint attention is associated with morphometric variation in the anterior cingulate cortex of chimpanzees (Pan troglodytes).

In developing human children, joint attention (JA) is an important preverbal skill fundamental to the development of language. Poor JA skills have been described as a behavioral risk factor for some neurodevelopmental disorders, such as autism spectrum disorder. It has been hypothesized that the anterior cingulate cortex (ACC) plays an important role in the development of JA in human children.

Social learning of a communicative signal in captive chimpanzees.

The acquisition of linguistic competency from more experienced social partners is a fundamental aspect of human language. However, there is little evidence that non-human primates learn to use their vocalizations from social partners. Captive chimpanzees (Pan troglodytes) produce idiosyncratic vocal signals that are used intentionally to capture the attention of a human experimenter.

Chimpanzee vocal signaling points to a multimodal origin of human language.

The evolutionary origin of human language and its neurobiological foundations has long been the object of intense scientific debate. Although a number of theories have been proposed, one particularly contentious model suggests that human language evolved from a manual gestural communication system in a common ape-human ancestor. Consistent with a gestural origins theory are data indicating that chimpanzees intentionally and referentially communicate via manual gestures, and the production of manual gestures, in conjunction with vocalizations, activates the chimpanzee Broca's area homologue--a region in the human brain that is critical for the planning and execution of language.

Cortical representation of lateralized grasping in chimpanzees (Pan troglodytes): a combined MRI and PET study.

Functional imaging studies in humans have localized the motor-hand region to a neuroanatomical landmark call the KNOB within the precentral gyrus. It has also been reported that the KNOB is larger in the hemisphere contralateral to an individual's preferred hand, and therefore may represent the neural substrate for handedness. The KNOB has also been neuronatomically described in chimpanzees and other great apes and is similarly associated with handedness.

A voxel-based morphometry analysis of white matter asymmetries in chimpanzees (Pan troglodytes).

Voxel-based morphometry (VBM) has become an increasingly common method for assessing neuroanatomical asymmetries in human in vivo magnetic resonance imaging (MRI). Here, we employed VBM to examine asymmetries in white matter in a sample of 48 chimpanzees (15 males and 33 females). T(1)-weighted MRI scans were segmented into white matter using FSL and registered to a common template.

The chimpanzee brain shows human-like perisylvian asymmetries in white matter.

Modern neuroimaging technologies allow scientists to uncover interspecies differences and similarities in hemispheric asymmetries that may shed light on the origin of brain asymmetry and its functional correlates. We analyzed asymmetries in ratios of white to grey matter in the lateral aspect of the lobes of the brains of chimpanzees. We found marked leftward asymmetries for all lobar regions.

Visualizing vocal perception in the chimpanzee brain.

The study of nonhuman primate vocal-auditory behavior continues to provide novel insights into the origins of human language. However, data on the neural systems involved in the perception and processing of conspecific vocalizations in great apes are virtually absent in the scientific literature, yet are critical for understanding the evolution of language. Here we used positron emission tomography to examine the neurological mechanisms associated with the perception of species-specific vocalizations in chimpanzees.

Gray matter asymmetries in chimpanzees as revealed by voxel-based morphometry.

Determination of whether nonhuman primates exhibit neuroanatomical asymmetries would inform our understanding of the evolution of traits in humans that show functional hemispheric dominance, including language and handedness. Here we report the first evidence of population-level asymmetries in the chimpanzee neocortex using voxel-based morphometry (VBM). MRI scans of the brain were collected in a sample of 31 chimpanzees including 9 males and 22 females, and the resulting images were segmented into gray matter, white matter and CSF.

Communicative signaling activates 'Broca's' homolog in chimpanzees.

Broca's area, a cerebral cortical area located in the inferior frontal gyrus (IFG) of the human brain, has been identified as one of several critical regions associated with the motor planning and execution of language. Anatomically, Broca's area is most often larger in the left hemisphere, and functional imaging studies in humans indicate significant left-lateralized patterns of activation during language-related tasks. If, and to what extent, nonhuman primates, particularly chimpanzees, possess a homologous region that is involved in the production of their own communicative signals remains unknown.

Sex differences in asymmetry of the planum parietale in chimpanzees (Pan troglodytes).

Magnetic resonance images were collected in 76 chimpanzees and the sylvian fissure was examined for the presence of a posterior bifurcation. A bilateral bifurcation of the sylvian fissure into an ascending and descending ramus was identified in 58 of the subjects. The posterior ascending ramus was measured in both hemispheres in order to evaluate the presence, magnitude, and direction of a planum parietale asymmetry.

Behavioral and neuroanatomical correlates of white matter asymmetries in chimpanzees (Pan troglodytes).

Although behavioral and brain asymmetries have been documented in non-human primates, lateralization in cortical connectivity as reflected in white matter has not been described in any species, despite the intrinsic theoretical interest in white matter expansion during primate brain evolution. Here we report evidence of population-level leftward asymmetries in the white matter of chimpanzees. We further report that lateralization in white matter correlates with their handedness as well as neuroanatomical asymmetries in the precentral gyrus.

Gesture handedness predicts asymmetry in the chimpanzee inferior frontal gyrus.

Neuroanatomical asymmetries have been identified in chimpanzee frontal and temporal lobes including regions believed to be homologous to human Broca's and Wernicke's areas. This study examined whether or not neuroanatomical asymmetries in chimpanzees are associated with hand use during gestural communication. Analyses revealed that those chimpanzees that reliably employ their right hand for manual gestures have larger inferior frontal gyri in the left hemisphere than those apes that do not show consistent hand use for gestures.