Exogenous testosterone increases status-seeking motivation in men with unstable low social status.

Testosterone is associated with status-seeking behaviors such as competition, which may depend on whether one wins or loses status, but also on the stability of one's status. We examined (1) to what extent testosterone administration affects competition behavior in repeated social contests in men with high or low rank, and (2), whether this relationship is moderated by hierarchy stability, as predicted by the status instability hypothesis. Using a real effort-based design in healthy male participants (N = 173 males), we first found that testosterone (vs. placebo) increased motivation to compete for status, but only in individuals with an unstable low status. A second part of the experiment, tailored to directly compare stable with unstable hierarchies, indicated that exogenous testosterone again increased competitive motivation in individuals with a low unstable status, but decreased competition behavior in men with low stable status. Additionally, exogenous testosterone increased motivation in those with a stable high status. Further analysis suggested that these effects were moderated by individuals' trait dominance, and genetic differences assessed by the androgen receptor (CAG-repeat) and dopamine transporter (DAT1) polymorphisms. Our study provides evidence that testosterone specifically boosts status-related motivation when there is an opportunity to improve one's social status. The findings contribute to our understanding of testosterone's causal role in status-seeking motivation in competition behavior, and indicate that testosterone adaptively increases our drive for high status in a context-dependent manner. We discuss potential neurobiological pathways through which testosterone may attain these effects on behavior.

Psychopharmacological modulation of event-related potentials suggests that first-hand pain and empathy for pain rely on similar opioidergic processes.

Accumulating evidence suggests that empathy for pain recruits similar neural processes as the first-hand experience of pain. The pain-related P2, an event-related potential component, has been suggested as a reliable indicator of neural processes associated with first-hand pain. Recent evidence indicates that placebo analgesia modulates this component for both first-hand pain and empathy for pain. Moreover, a psychopharmacological study showed that administration of an opioid antagonist blocked the effects of placebo analgesia on self-report of both first-hand pain and empathy for pain. Together, these findings suggest that the opioid system plays a similar role during first-hand pain and empathy for pain. However, such a conclusion requires evidence showing that neural activity during both experiences is similarly affected by psychopharmacological blockage of opioid receptors. Here, we measured pain-related P2 amplitudes and self-report in a group of participants who first underwent a placebo analgesia induction procedure. Then, they received an opioid receptor antagonist known to block the previously induced analgesic effects. Self-report showed that blocking opioid receptors after the induction of placebo analgesia increased both first-hand pain and empathy for pain, replicating previous findings. Importantly, P2 amplitudes were also increased during both experiences. Thus, the present findings extend models proposing that empathy for pain is partially grounded in first-hand pain by suggesting that this also applies to the underlying opioidergic neurochemical processes.

Effects of dopamine D2/D3 receptor antagonism on human planning and spatial working memory.

Psychopharmacological studies in humans suggest important roles for dopamine (DA) D2 receptors in human executive functions, such as cognitive planning and spatial working memory (SWM). However, studies that investigate an impairment of such functions using the selective DA D2/3 receptor antagonist sulpiride have yielded inconsistent results, perhaps because relatively low doses were used. We believe we report for the first time, the effects of a higher (800 mg p.o.) single dose of sulpiride as well as of genetic variation in the DA receptor D2 gene (DA receptor D2 Taq1A polymorphism), on planning and working memory. With 78 healthy male volunteers, we apply a between-groups, placebo-controlled design. We measure outcomes in the difficult versions of the Cambridge Neuropsychological Test Automated Battery One-Touch Stockings of Cambridge and the self-ordered SWM task. Volunteers in the sulpiride group showed significant impairments in planning accuracy and, for the more difficult problems, in SWM. Sulpiride administration speeded response latencies in the planning task on the most difficult problems. Volunteers with at least one copy of the minor allele (A1+) of the DA receptor D2 Taq1A polymorphism showed better SWM capacity, regardless of whether they received sulpiride or placebo. There were no effects on blood pressure, heart rate or subjective sedation. In sum, a higher single dose of sulpiride impairs SWM and executive planning functions, in a manner independent of the DA receptor D2 Taq1A polymorphism.

Competition, testosterone, and adult neurobehavioral plasticity.

Motivation in performance is often measured via competitions. Winning a competition has been found to increase the motivation to perform in subsequent competitions. One potential neurobiological mechanism that regulates the motivation to compete involves sex hormones, such as the steroids testosterone and estradiol. A wealth of studies in both nonhuman animals and humans have shown that a rise in testosterone levels before and after winning a competition enhances the motivation to compete. There is strong evidence for acute behavioral effects in response to steroid hormones. Intriguingly, a substantial testosterone surge following a win also appears to improve an individual's performance in later contests resulting in a higher probability of winning again. These effects may occur via androgen and estrogen pathways modulating dopaminergic regions, thereby behavior on longer timescales. Hormones thus not only regulate and control social behavior but are also key to adult neurobehavioral plasticity. Here, we present literature showing hormone-driven behavioral effects that persist for extended periods of time beyond acute effects of the hormone, highlighting a fundamental role of sex steroid hormones in adult neuroplasticity. We provide an overview of the relationship between testosterone, motivation measured from objective effort, and their influence in enhancing subsequent effort in competitions. Implications for an important role of testosterone in enabling neuroplasticity to improve performance will be discussed.

Altered social and non-social decision-making in recreational and dependent cocaine users.

BACKGROUND: Maladaptive decision-making is assumed to be a core feature of cocaine addiction. Indeed, numerous studies have reported deficits in non-social decision-making tasks and reward-related impulsivity in dependent cocaine users. However, social decision-making has not been examined in cocaine users yet. Moreover, it is unknown if even recreational and non-dependent cocaine use is linked to decision-making deficits. Therefore, we investigated whether recreational and dependent cocaine users exhibit alterations in social and non-social decision-making. METHOD: The performance of healthy controls (n = 68), recreational cocaine users (n = 68) and dependent cocaine users (n = 30) in classical decision-making paradigms (Iowa Gambling Task, Delay Discounting) and in social interaction paradigms (Distribution Game, Dictator Game) was assessed. RESULTS: Decisions in the social interaction tasks of both cocaine user groups were more self-serving compared with controls as cocaine users preferred higher monetary payoffs for themselves. In the Iowa Gambling Task, only dependent cocaine users were more likely to choose disadvantageous card decks, reflecting worse decision-making. They were also more likely to choose immediate smaller rewards over larger delayed rewards in the Delay Discounting task. CONCLUSIONS: Our results imply that both recreational and dependent cocaine users are more concerned with their own monetary gain when interacting with another person. Furthermore, primarily dependent cocaine users are less foresighted and more impulsive regarding immediate reward. Overall, social interaction deficits are already present in recreational users, while non-social decision-making deficits occur predominantly in dependent cocaine users. Thus, social interaction training and cognitive remediation strategies may improve treatment success and quality of life in cocaine dependence.

Prejudice and truth about the effect of testosterone on human bargaining behaviour.

Both biosociological and psychological models, as well as animal research, suggest that testosterone has a key role in social interactions. Evidence from animal studies in rodents shows that testosterone causes aggressive behaviour towards conspecifics. Folk wisdom generalizes and adapts these findings to humans, suggesting that testosterone induces antisocial, egoistic, or even aggressive human behaviours. However, many researchers have questioned this folk hypothesis, arguing that testosterone is primarily involved in status-related behaviours in challenging social interactions, but causal evidence that discriminates between these views is sparse. Here we show that the sublingual administration of a single dose of testosterone in women causes a substantial increase in fair bargaining behaviour, thereby reducing bargaining conflicts and increasing the efficiency of social interactions. However, subjects who believed that they received testosterone-regardless of whether they actually received it or not-behaved much more unfairly than those who believed that they were treated with placebo. Thus, the folk hypothesis seems to generate a strong negative association between subjects' beliefs and the fairness of their offers, even though testosterone administration actually causes a substantial increase in the frequency of fair bargaining offers in our experiment.

Time-course of "off-line" prefrontal rTMS effects--a PET study.

Low-frequency "off-line" repetitive transcranial magnetic stimulation (rTMS) over the course of several minutes has attained considerable attention as a research tool in cognitive neuroscience due to its ability to induce functional disruptions of brain areas. This disruptive rTMS effect is highly valuable for revealing a causal relationship between brain and behavior. However, its influence on remote interconnected areas and, more importantly, the duration of the induced neurophysiological effects, remain unknown. These aspects are critical for a study design in the context of cognitive neuroscience. In order to investigate these issues, 12 healthy male subjects underwent 8 H(2)(15)O positron emission tomography (PET) scans after application of long-train low-frequency rTMS to the right dorsolateral prefrontal cortex (DLPFC). Immediately after the stimulation train, regional cerebral blood flow (rCBF) increases were present under the stimulation site as well as in other prefrontal cortical areas, including the ventrolateral prefrontal cortex (VLPFC) ipsilateral to the stimulation site. The mean increases in rCBF returned to baseline within 9 min. The duration of this unilateral prefrontal rTMS effect on rCBF is of particular interest to those who aim to influence behavior in cognitive paradigms that use an "off-line" approach.

The involvement of primary motor cortex in mental rotation revealed by transcranial magnetic stimulation.

We used single-pulse transcranial magnetic stimulation of the left primary hand motor cortex and motor evoked potentials of the contralateral right abductor pollicis brevis to probe motor cortex excitability during a standard mental rotation task. Based on previous findings we tested the following hypotheses. (i) Is the hand motor cortex activated more strongly during mental rotation than during reading aloud or reading silently? The latter tasks have been shown to increase motor cortex excitability substantially in recent studies. (ii) Is the recruitment of the motor cortex for mental rotation specific for the judgement of rotated but not for nonrotated Shepard & Metzler figures? Surprisingly, motor cortex activation was higher during mental rotation than during verbal tasks. Moreover, we found strong motor cortex excitability during the mental rotation task but significantly weaker excitability during judgements of nonrotated figures. Hence, this study shows that the primary hand motor area is generally involved in mental rotation processes. These findings are discussed in the context of current theories of mental rotation, and a likely mechanism for the global excitability increase in the primary motor cortex during mental rotation is proposed.