The purpose of the present study was to push the boundaries of cooperation among captive chimpanzees (Pan troglodytes). There has been doubt about the level of cooperation that chimpanzees are able to spontaneously achieve or understand. Would they, without any pre-training or restrictions in partner choice, be able to develop successful joint action? And would they be able to extend cooperation to more than two partners, as they do in nature? Chimpanzees were given a chance to cooperate with multiple partners of their own choosing. All members of the group (N = 11) had simultaneous access to an apparatus that required two (dyadic condition) or three (triadic condition) individuals to pull in a tray baited with food. Without any training, the chimpanzees spontaneously solved the task a total of 3,565 times in both dyadic and triadic combinations. Their success rate and efficiency increased over time, whereas the amount of pulling in the absence of a partner decreased, demonstrating that they had learned the task contingencies. They preferentially approached the apparatus when kin or nonkin of similar rank were present, showing a preference for socially tolerant partners. The forced partner combinations typical of cooperation experiments cannot reveal these abilities, which demonstrate that in the midst of a complex social environment, chimpanzees spontaneously initiate and maintain a high level of cooperative behavior.
The field of primate behavior management has had only limited success at preventing and treating abnormal behaviors such as stereotypy and self-injury in captive non-human primates (NHP). In contrast, applied behavior analysts have had great success in treating similar topographies of behavior in human clinical settings. By adapting and adopting the behavioral principles and methodologies commonly used by applied behavior analysts, primatologists may be able to develop more effective ways to analyze, reduce, and prevent these aberrant behaviors in NHP. This paper reviews studies that have used behavior analytic techniques to successfully address problem behaviors in NHP. Additionally, relevant literature from the field of applied behavior analysis is reviewed to illustrate how adopting a theoretical framework that emphasizes the determination of the underlying operant functions of behavior could lead to new behavioral technologies and advance the field of captive primate management.
Regulating ankle mechanics is essential for controlled interactions with the environment and rejecting unexpected disturbances. Ankle mechanics can be quantified by impedance, the dynamic relationship between an imposed displacement and the torque generated in response. Ankle impedance in the sagittal plane depends strongly on the triceps surae and Achilles tendon, but their relative contributions remain unknown. It is commonly assumed that ankle impedance is controlled by changing muscle activation and, thereby, muscle impedance, but this ignores that tendon impedance also changes with activation-induced loading. Thus, we sought to determine the relative contributions from the triceps surae and Achilles tendon during conditions relevant to postural control. We used a novel technique that combines B-mode ultrasound imaging with joint-level perturbations to quantify ankle, muscle and tendon impedance simultaneously across activation levels from 0% to 30% of maximum voluntary contraction. We found that muscle and tendon stiffness, the static component of impedance, increased with voluntary plantarflexion contractions, but that muscle stiffness exceeded tendon stiffness at very low loads (21±7 N). Above these loads, corresponding to 1.3% of maximal strength for an average participant in our study, ankle stiffness was determined predominately by Achilles tendon stiffness. At approximately 20% MVC for an average participant, ankle stiffness was 4 times more sensitive to changes in tendon stiffness than to changes in muscle stiffness. We provide the first empirical evidence demonstrating that the nervous system, through changes in muscle activations, leverages the non-linear properties of the Achilles tendon to increase ankle stiffness during postural conditions.
Children with an anxious temperament (AT) are at a substantially increased risk to develop anxiety and depression. The young rhesus monkey is ideal for studying the origin of human AT because it shares with humans the genetic, neural, and phenotypic underpinnings of complex social and emotional functioning. Heritability, functional imaging, and gene expression studies of AT in young monkeys revealed that the central nucleus of the amygdala (Ce) is a key environmentally sensitive substrate of this at risk phenotype. Because epigenetic marks (e.g., DNA methylation) can be modulated by environmental stimuli, these data led us to hypothesize a role for DNA methylation in the development of AT. To test this hypothesis, we used reduced representation bisulfite sequencing to examine the cross-sectional genome-wide methylation levels in the Ce of 23 age-matched monkeys (1.3 ± 0.2 years) phenotyped for AT. Because AT reflects a continuous trait-like variable, we used an analytical approach that is consistent with this biology to identify genes in the Ce with methylation patterns that predict AT. Expression data from the Ce of these same monkeys were then used to find differentially methylated candidates linked to altered gene regulation. Two genes particularly relevant to the AT phenotype were BCL11A and JAG1. These transcripts have well-defined roles in neurodevelopmental processes, including neurite arborization and the regulation of neurogenesis. Together, these findings represent a critical step toward understanding the effects of early environment on the neuromolecular mechanisms that underlie the risk to develop anxiety and depressive disorders.
A fundamental aspect of behavior in many animal species is 'social facilitation', the positive effect of the mere presence of conspecifics on performance. To date, the neuronal counterpart of this ubiquitous phenomenon is unknown. We recorded the activity of single neurons from two prefrontal cortex regions, the dorsolateral part and the anterior cingulate cortex in monkeys as they performed a visuomotor task, either in the presence of a conspecific (Presence condition) or alone. Monkeys performed better in the presence condition than alone (social facilitation), and analyses of outcome-related activity of 342 prefrontal neurons revealed that most of them (86%) were sensitive to the performance context. Two populations of neurons were discovered: 'social neurons', preferentially active under social presence and 'asocial neurons', preferentially active under social isolation. The activity of these neurons correlated positively with performance only in their preferred context (social neurons under social presence; asocial neurons under social isolation), thereby providing a potential neuronal mechanism of social facilitation. More generally, the fact that identical tasks recruited either social or asocial neurons depending on the presence or absence of a conspecific also brings a new look at the social brain hypothesis.
This study further investigated the specific contributions of the medial temporal lobe structures to contextual recognition memory. Monkeys (. Macaca mulatta) with either neurotoxic lesions of the hippocampus, aspiration lesions of the perirhinal cortex and parahippocampal areas TH/TF, or sham operations were tested on five conditions of a visual-paired comparison (VPC) task in which 3-dimensional objects were presented over multicolored backgrounds. In two conditions (Conditions 1 and 2: Context-changes), the sample object was presented on a new background during the retention tests, whereas in the three others (Conditions 3-5: No-context-changes) the sample object was presented over its familiar background. Novelty preference scores of control animals were weaker, but still significantly different from chance, in the Context-changes conditions than on the No-context-changes conditions. Animals in the three experimental groups showed strong preference for novelty on the No-context-change conditions, but weaker novelty preference on the Context-change conditions than controls. Thus, animals in all three lesion types had greater difficulty recognizing an object when its background was different from that used during encoding. The data are consistent with the view that the hippocampal formation, areas TH/TF, and perirhinal cortex contribute interactively to contextual memory processes.
Novel tests of semantic memory (SM)—for example, memory for news events (NE; news facts) or famous personalities—are useful for estimating the severity of retrograde amnesia. Individuals with mild cognitive impairment exhibit relatively intact SM/language on traditional neuropsychological tests but exhibit consistent impairment on novel tests of SM, suggesting novel SM tests are dissimilar from traditional SM tests. To identify the relationship between NE memory and traditional cognitive measures, older adults (N = 51) completed a traditional neuropsychological battery and the Retrograde Memory News Events Test (RM-NET; a new test that robustly measures NE memory across the adult life span with high temporal resolution), and the relationship between performance on these tests was examined. Total RM-NET scores were more closely aligned with episodic memory scores than SM scores. The strength of the association between NE scores and episodic memory scores decreased as the age of NE memory increased. Tests of news events appear to reflect performance on traditional tests of episodic memory rather than SM, especially when recent news events are tested.
by
Brian J. Roach;
Holly K. Hamilton;
Peter Bachman;
Aysenil Belger;
Ricardo E. Carrion;
Erica Duncan;
Jason Johannesen;
Joshua G. Kenney;
Gregory Light;
Margaret Niznikiewicz;
Jean Addington;
Carrie E. Bearden;
Emily M. Owens;
Kristin S. Cadenhead;
Tyrone D. Cannon;
Barbara A. Cornblatt;
Thomas H. McGlashan;
Diana O. Perkins;
Larry Seidman;
Ming Tsuang;
Elaine Walker;
Scott W. Woods;
Daniel H. Mathalon
Objectives
Mismatch negativity (MMN), an auditory event‐related potential sensitive to deviance detection, is smaller in schizophrenia and psychosis risk. In a multisite study, a regression approach to account for effects of site and age (12–35 years) was evaluated alongside the one‐year stability of MMN.
Methods
Stability of frequency, duration, and frequency + duration (double) deviant MMN was assessed in 167 healthy subjects, tested on two occasions, separated by 52 weeks, at one of eight sites. Linear regression models predicting MMN with age and site were validated and used to derive standardized MMN z‐scores. Variance components estimated for MMN amplitude and latency measures were used to calculate Generalizability (G) coefficients within each site to assess MMN stability. Trait‐like aspects of MMN were captured by averaging across occasions and correlated with subject traits.
Results
Age and site accounted for less than 7% of MMN variance. G‐coefficients calculated at electrode Fz were stable (G = 0.63) across deviants and sites for amplitude measured in a fixed window, but not for latency (G = 0.37). Frequency deviant MMN z‐scores averaged across tests negatively correlated with averaged global assessment of functioning.
Conclusion
MMN amplitude is stable and can be standardized to facilitate longitudinal multisite studies of patients and clinical features.
Functional connectivity using task-residual data capitalizes on remaining variance after mean task-related signal is removed from a time series. The degree of network specificity in language and attention domains featured by task-residual and resting-state data types were compared. Functional connectivity based on task-residual data evidenced stronger laterality of the language and attention connections and thus greater network specificity compared to resting-state functional connectivity of the same connections. Covariance between network nodes of task-residuals may thus reflect the degree to which two regions are coordinated in their specific activity, rather than a general shared co-activation. Task-residual functional connectivity provides complementary data to that of resting-state, emphasizing network relationships during task engagement.
Having previously used functional MRI to map the response to a reward signal in the ventral caudate in awake unrestrained dogs, here we examined the importance of signal source to canine caudate activation. Hand signals representing either incipient reward or no reward were presented by a familiar human (each dog’s respective handler), an unfamiliar human, and via illustrated images of hands on a computer screen to 13 dogs undergoing voluntary fMRI. All dogs had received extensive training with the reward and no-reward signals from their handlers and with the computer images and had minimal exposure to the signals from strangers. All dogs showed differentially higher BOLD response in the ventral caudate to the reward versus no reward signals, and there was a robust effect at the group level. Further, differential response to the signal source had a highly significant interaction with a dog’s general aggressivity as measured by the C-BARQ canine personality assessment. Dogs with greater aggressivity showed a higher differential response to the reward signal versus no-reward signal presented by the unfamiliar human and computer, while dogs with lower aggressivity showed a higher differential response to the reward signal versus no-reward signal from their handler. This suggests that specific facets of canine temperament bear more strongly on the perceived reward value of relevant communication signals than does reinforcement history, as each of the dogs were reinforced similarly for each signal, regardless of the source (familiar human, unfamiliar human, or computer). A group-level psychophysiological interaction (PPI) connectivity analysis showed increased functional coupling between the caudate and a region of cortex associated with visual discrimination and learning on reward versus no-reward trials. Our findings emphasize the sensitivity of the domestic dog to human social interaction, and may have other implications and applications pertinent to the training and assessment of working and pet dogs.