Papers by Julen Hernandez-Lallement
Callous-unemotional traits – the insensitivity to other's welfare and well-being – are characteri... more Callous-unemotional traits – the insensitivity to other's welfare and well-being – are characterized by a lack of empathy. They are characteristic of psychopathy and can be found in other antisocial disorders, such as conduct disorder. Because of the increasing prevalence of antisocial disorders and the rising societal costs of violence and aggression, it is of great importance to elucidate the psychological and physiological mechanisms underlying callousness in the search for pharmacological treatments. One promising avenue is to create a relevant animal model to explore the neural bases of callousness. Here, we review recent advances in rodent models of pro-social choice that could be applied to probe the absence of pro-sociality as a proxy of callous behavior, and provide future directions for the exploration of the neural substrates of callousness.
Disadvantageous inequity aversion (IA) is a behavioural response to an inequitable outcome distri... more Disadvantageous inequity aversion (IA) is a behavioural response to an inequitable outcome distribution yielding a smaller reward to oneself than to a conspecific, given comparable efforts to obtain the reward. This behavioural response aims to minimize unfair reward distributions. It has been proposed to be essential for the emergence of cooperation. Humans show choice patterns compatible with IA and, as recently suggested, cooperative nonhuman species such as primates, corvids and dogs also respond negatively to disadvantageous inequitable outcomes. Here, we asked whether rats are sensitive to such inequitable outcomes. In a double T-maze apparatus, actor rats could choose to enter one of two different compartments after which a conspecific (partner rat) entered the adjoining partner compartment. One side of the paired compartments was associated with an equitable reward distribution (identical amount for the actor and the partner) whereas entry into the other paired compartment led to an inequitable reward distribution (in which the partner received a larger reward). Both compartments yielded an identical reward for the actor. Using a within-subjects design, we compared the actor rats' choices in the social condition with a nonsocial baseline control condition in which a toy rat replaced the partner rat. Actor rats exhibited disadvantageous IA: they preferred equitable outcomes in the social, but not the toy condition. Moreover, there was large variability in IA between rats. This heterogeneity in social preference could be partly explained by a social-hierarchy-dependent sensitivity to IA, as dominant animals showed higher IA than subordinate animals. Our study provides evidence for social-hierarchy-dependent disadvantageous IA in social vertebrates. Our findings are consistent with the notion that a sense of fairness may have evolved long before humans emerged. IA may therefore be a basic organizational principle, shared by many social species, that shapes the intricate social dynamics of individuals interrelating in larger groups.
Current Topics in Behavioral Neurosciences, 2016
Although the use of neuroimaging techniques has revealed much about the neural correlates of soci... more Although the use of neuroimaging techniques has revealed much about the neural correlates of social decision making (SDM) in humans, it remains poorly understood how social stimuli are represented, and how social decisions are implemented at the neural level in humans and in other species. To address this issue, the establishment of novel animal paradigms allowing a broad spectrum of neurobiological causal manipulations and neurophysiological recordings provides an exciting tool to investigate the neural implementation of social valuation in the brain. Here, we discuss the potential of a rodent model, Rattus norvegicus, for the understanding of SDM and its neural underpinnings. Particularly, we consider recent data collected in a rodent prosocial choice task within a social reinforcement framework and discuss factors that could drive SDM in rodents.
In a recent study, we demonstrated that rats prefer mutual rewards in a Prosocial Choice Task. He... more In a recent study, we demonstrated that rats prefer mutual rewards in a Prosocial Choice Task. Here, employing the same task, we show that the integrity of basolateral amygdala was necessary for the expression of mutual reward preferences. Actor rats received bilateral excitotoxic (n = 12) or sham lesions (n = 10) targeting the basolateral amygdala and were subsequently tested in a Prosocial Choice Task where they could decide between rewarding (‘‘Both Reward”) or not rewarding a partner rat (‘‘Own Reward”), either choice yielding identical reward to the actors themselves. To manipulate the social context and control for secondary reinforcement sources, actor rats were paired with either a partner rat (partner condition) or with an inanimate rat toy (toy condition). Sham-operated animals revealed a significant preference for the Both-Reward-option in the partner condition, but not in the toy condition. Amygdala-lesioned animals exhibited significantly lower Both-Reward preferences than the sham group in the partner but not in the toy condition, suggesting that basolateral amygdala was required for the expression of mutual reward preferences. Critically, in a reward magnitude discrimination task in the same experimental setup, both sham-operated and amygdala-lesioned animals preferred large over small rewards, suggesting that amygdala lesion effects were restricted to decision making in social contexts, leaving self-oriented behavior unaffected
It is ecologically adaptive that the amount of effort invested to achieve a reward increases the ... more It is ecologically adaptive that the amount of effort invested to achieve a reward increases the relevance of the resulting outcome. Here, we investigated the effect of effort on activity in reward and loss processing brain areas by using functional magnetic resonance imaging. In total, 28 subjects were endowed with monetary rewards of randomly varying magnitude after performing arithmetic calculations that were either difficult (high effort), easy (low effort) or already solved (no effort). Subsequently, a forced donation took place, where a varying part of the endowment was transferred to a charity organization, causing a loss for the subject. Results show that reward magnitude positively modulates activity in reward-processing brain areas (subgenual anterior cingulate cortex and nucleus accumbens) only in the high effort condition. Furthermore, anterior insular activity was positively modulated by loss magnitude only after high effort. The results strongly suggest an increasing relevance of outcomes with increasing previous effort.
Pro-sociality, i.e., the preference for outcomes that produce benefits for other individuals,
is ... more Pro-sociality, i.e., the preference for outcomes that produce benefits for other individuals,
is ubiquitous in humans. Recently, cross-species comparisons of social behavior have
offered important new insights into the evolution of pro-sociality. Here, we present
a rodent analog of the Pro-social Choice Task that controls strategic components,
de-confounds other-regarding choice motives from the animals’ natural tendencies to
maximize own food access and directly tests the effect of social context on choice
allocation. We trained pairs of rats—an actor and a partner rat—in a double T-maze task
where actors decided between two alternatives only differing in the reward delivered
to the partner. The “own reward” choice yielded a reward only accessible to the actor
whereas the “both reward” choice produced an additional reward for a partner (partner
condition) or an inanimate toy (toy Condition), located in an adjacent compartment. We
found that actors chose “both reward” at levels above chance and more often in the
partner than in the toy condition. Moreover, we show that this choice pattern adapts to
the current social context and that the observed behavior is stable over time
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Papers by Julen Hernandez-Lallement
is ubiquitous in humans. Recently, cross-species comparisons of social behavior have
offered important new insights into the evolution of pro-sociality. Here, we present
a rodent analog of the Pro-social Choice Task that controls strategic components,
de-confounds other-regarding choice motives from the animals’ natural tendencies to
maximize own food access and directly tests the effect of social context on choice
allocation. We trained pairs of rats—an actor and a partner rat—in a double T-maze task
where actors decided between two alternatives only differing in the reward delivered
to the partner. The “own reward” choice yielded a reward only accessible to the actor
whereas the “both reward” choice produced an additional reward for a partner (partner
condition) or an inanimate toy (toy Condition), located in an adjacent compartment. We
found that actors chose “both reward” at levels above chance and more often in the
partner than in the toy condition. Moreover, we show that this choice pattern adapts to
the current social context and that the observed behavior is stable over time
is ubiquitous in humans. Recently, cross-species comparisons of social behavior have
offered important new insights into the evolution of pro-sociality. Here, we present
a rodent analog of the Pro-social Choice Task that controls strategic components,
de-confounds other-regarding choice motives from the animals’ natural tendencies to
maximize own food access and directly tests the effect of social context on choice
allocation. We trained pairs of rats—an actor and a partner rat—in a double T-maze task
where actors decided between two alternatives only differing in the reward delivered
to the partner. The “own reward” choice yielded a reward only accessible to the actor
whereas the “both reward” choice produced an additional reward for a partner (partner
condition) or an inanimate toy (toy Condition), located in an adjacent compartment. We
found that actors chose “both reward” at levels above chance and more often in the
partner than in the toy condition. Moreover, we show that this choice pattern adapts to
the current social context and that the observed behavior is stable over time