Dopamine modulates effort-based decision making in rats.

Previous research has implicated dopamine as a modulating factor in choice behavior based on effort. The purpose of the present study was to determine the individual contribution of different dopamine receptors to effort-based decision making in rats. Rats were trained in a T-maze to choose a large-reward arm that contained 8 pellets of food over a small-reward arm that contained 2 pellets of food. The rats then were trained to climb progressively higher barriers to obtain the food from the large-reward arm. Using a discounting procedure on each test day, it was found that rats were more likely to choose the small-reward arm after treatment with the D1 antagonist, SCH-23390, or the D2 antagonist, haloperidol. The dopamine agonist, D-amphetamine, biased the rats toward choosing the large-reward arm and blunted the effects of SCH-23390 or haloperidol. Treatment with the D3 receptor antagonist, U99194, or the D3 receptor agonist, 7-OH-DPAT, did not alter choice behavior. These data indicate that D1 and D2 receptors are required for decisions based on effort. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Dopamine: Helping males copulate for at least 200 million years: Theoretical comment on Kleitz-Nelson et al. (2010).

Brain dopamine (DA) systems are implicated in a variety of behavioral responses and clinical syndromes, including sex, drug addiction, feeding, satiety, sleep, wakefulness, arousal, attention, reward, decision-making, depression, anxiety, psychosis, and movement disorders. The paper in this issue (see record 2010-24688-004) by Kleitz-Nelson, Dominguez, and Ball (2010) shows how DA release in the medial preoptic area of male quail are activated in an androgen-dependent manner during appetitive and consummatory phases of sexual behavior, similar to that reported previously in male rats. Those data suggest that the steroid-dependent role of hypothalamic DA in male sexual behavior has been conserved through evolutionary time. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Espresso Reward Learning, Hold the Dopamine: Theoretical Comment on Robinson et al. (2005).

Question: Is dopamine needed for reward learning? Answer: No--at least, not in the brain of a caffeinated dopamine-deficient (DD) mutant mouse. That is the conclusion of an important paper in this issue by S. Robinson, S. M. Sandstrom, V. H. Denenberg, and R. D. Palmiter (see record 2005-01705-001). Those authors demonstrate that reward learning can proceed normally in the brains of DD mice, even though they contain no dopamine at the time of learning, if the mice are given caffeine just before learning. Caffeine activates the DD mice by a nondopaminergic mechanism, allowing them to learn where to obtain food reward in a T-maze runway. Their reward-learning-without-dopamine is revealed on a subsequent test day, when dopamine function is restored by L-dopa administration. Robinson et al. conclude that dopamine is not needed for normal learning about rewards, or for hedonic "liking" of rewards during learning, but rather specifically for a motivational "wanting" component of reward, such as incentive salience. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Dopamine and reward: Comment on Hernandez et al. (2006).

Many lines of evidence suggest that the dopaminergic projection from the midbrain tegmentum to the forebrain must play a critical role in mediating the behavioral effects of natural and artificial rewards, with brain stimulation reward and addictive drugs included in the latter category. However, a closer look reveals many incongruities. The work of G. Hernandez et al. (2006; see record 2006-09890-013) resolves several puzzles. It implies that the dopaminergic projection does not carry the signal that encodes the magnitude of a brain stimulation reward. It suggests that the elevation in the tonic levels of dopamine consequent on brain stimulation reward modulates the registration of the magnitude of the reward. This reconciles the psychophysical evidence with the pharmacological, electrophysiological, and anatomical evidence. However, some serious puzzles do remain. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The construction of the maternal brain: Theoretical comment on Kim et al. (2010).

Recently, there has been a spate of articles detailing the many and multifaceted alterations that define the Maternal Brain. The article by Kim et al. (2010) has provided a new “window” into the brain of the mother by the use of MRI showing structural changes in major regions over the period of the first few months, during which the intimate relationship between mother and infant forms. In this accompanying Commentary, we explore some connections between the animal work and the human data, and suggest some common pathways. In the end, it appears that maternal motivation, far from the intrinsic or instinctual state that many believe it to be, may, in fact, be attributable to many active processes “building” a responsive neural substrate. Like early brain development, itself a marvel of interacting genetic and environmental forces, the Maternal Brain may represent another developmental epoch in the life of the female. In this case, the alterations occur to promote the survival of subsequent generations and the care and protection of a most expensive mammalian metabolic and genetic investment. If so, is it possible that just as there are edifices that are poorly constructed and crumble at the first challenge by earthquake or hurricane, there may be defectively assembled maternal brains that fail in their task of caring adequately for young? (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The value of a comparative perspective: Theoretical comment on Pearce et al. (2005).

J. M. Pearce, D. N. George, M. Haselgrove, J. T. Erichson, and M. Good (2005) (see record 2005-13804-017) report that damage to the hippocampus does not impair either delay conditioning, a biconditional discrimination, or a series of complex visual and spatial discriminations that require feature binding, but does impair trace conditioning and the ability to perform a working and reference memory maze task. The J. M. Pearce et al. study highlights the value of a comparative perspective and the value of appreciating the multiple ways in which animals can solve tasks, which together will provide a deeper understanding of the function of the hippocampus. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Amyloid, hyperactivity, and metabolism: Theoretical comment on Vloeberghs et al. (2008).

Recent data suggest that amyloid precursor protein transgenic mice consume excess calories relative to nontransgenic mice, yet they weigh less. Potential explanations include increased locomotor activity or increased basal metabolism. Mechanisms that might underlie the latter explanation include transmembrane pores produced by assemblies of Aβ modifying proton or ion gradients across membranes. Alzheimer's disease also results in weight loss. If amyloid were found to induce a hypermetabolic state, this would suggest an alternative mechanism for the pathology found in the disease and provide opportunities for therapeutic strategies not yet considered. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Biological implementation of the temporal difference algorithm for reinforcement learning: Theoretical comment on O'Reilly et al. (2007).

The ability to survive in the world depends critically on the brain's capacity to detect earlier and earlier predictors of reward or punishment. The dominant theoretical perspective for understanding this capacity has been the temporal difference (TD) algorithm for reinforcement learning. In this issue of Behavioral Neuroscience, R. C. O'Reilly, M. J. Frank, T. E. Hazy, and B. Watz (2007, see record 2007-02025-004)) propose a new model dubbed primary value and learned value (PVLV) that is simpler than TD, and they claimed that it is biologically more realistic. In this commentary, the author suggests some slight modifications of a previous biological implementation of TD instead of adopting the new PVLV algorithm. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Motivated decision making: Effects of activation and self-centrality of values on choices and behavior.

Six studies examined the value-behavior relation and focused on motivational properties of values, the self, and value activation. Priming environmental values enhanced attention to and the weight of information related to those values, which resulted in environmentally friendly consumer choices. This only occurred if these values were central to the self-concept. Value-congruent choices were also found in response to countervalue behavior in an unrelated context. Donating behavior congruent with central altruistic values was found as a result of enhanced self-focus, thus demonstrating the importance of the self in the value-behavior relation. The external validity of the value-centrality measure and its distinction from attitudes were demonstrated in the prediction of voting. Values were thus found to give meaning to, energize, and regulate value-congruent behavior, but only if values were cognitively activated and central to the self. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Impulsivity as a mediating mechanism between early-life adversity and addiction: Theoretical comment on Lovic et al. (2011).

Early-life adversity, impulsivity, and dopaminergic function have all been implicated in adult drug addiction. The article by Lovic, Keen, Fletcher, and Fleming in this issue further elucidates this relationship by demonstrating that early-life adversity can increase impulsivity and decrease behavioral flexibility in adulthood. Recent literature suggests that these results are likely due to structural and functional changes in regions such as the orbitofrontal cortex (OFC) and nucleus accumbens (NAc), as well as altered dopamine activity. Impulsivity and behavioral inflexibility can increase susceptibility to addiction, and in turn, chronic substance abuse can impair the neurocircuitry underlying behavioral inhibition. Thus, early-life adversity may act as an entry point into a feed-forward spiral of impulsivity and addiction via the dysfunction of regions such as the OFC, NAc, and mesolimbic dopamine. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Adaptive priorities in brain development: Theoretical comment on Pravosudov et al. (2005).

V. V. Pravosudov, P. Lavenex, and A. Omanska (2005) (see record 2005-13804-022) reported that undernutrition in the first few weeks' posthatching leads to lower mean hippocampus volumes in adult Western scrub jays (Aphelocoma californica) and to poorer performance on spatial memory tasks. Together with prior work on the effects of poor nutrition on the development of the song system in songbirds, these results fit reasonably well with the view that natural selection determines priorities for investment in the development of neural structures. What seems somewhat anomalous under this view is that undernutrition did not affect the development of color association abilities in scrub jays. This work sets the stage for future comparative research on adaptive priorities in the development of brain and behavior. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of neonatal medial versus lateral temporal cortex injury: Theoretical comment on Malkova et al. (2010).

The article by Malkova, Mishkin, Suomo, and Bachevalier (see record 2010-24688-002) adds an important piece to our understanding of the role of the medial versus lateral temporal regions in socioemotional behavior. In their paper, they evaluate the effect of infant and adult amygdala lesions and infant inferotemporal cortex lesions on the social interactions of monkeys in infancy and adulthood. The results show that medial temporal lesions performed in infants produce greater effects on socioaffective behavior than similar lesions in adulthood and that infant monkeys with inferotemporal lesions exhibit social deficits that are resolved by adulthood. These results are relevant to three significant issues: (1) the role of the medial temporal and lateral temporal cortex in the symptoms of the Kluver-Bucy syndrome; (2) the role of age at injury in behavioral change after cerebral injuries; and (3) the importance of lesion locus and behavioral measure for recovery from infant and adult cerebral injury. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Weak criticisms and selective evidence: Reply to Blanton et al. (2009).

We respond to a critique by H. Blanton et al. (see record 2009-06703-001), challenging our previous work demonstrating that an Implicit Association Test designed to assess implicit prejudice reliably predicts intergroup discrimination (see record 2001-11532-008). We outline 3 flawed aspects of the critique. First, we note that claims that an outlier should be eliminated from the original data set are unfounded, and even with the elimination of this outlier, the conclusions of our original work are still strongly supported by the data. Second, we explain that concerns about interjudge reliability are specious and that considerable data support the validity of the judges’ observations reported in our original study. Third, we note that claims of a disconnect between Implicit Association Test scores (argued to show negative bias against Blacks) and behavioral measures (argued to show pro-Black bias) are inappropriate because they neglect the relativistic nature of the key measures. Implications for the relation between implicit attitudes and behavior, for the law, and for future work on implicit attitudes are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Pigeons prefer conditional stimuli over their absence: A comment on Roberts et al. (2009).

Recently, Roberts et al. (2009) have suggested that pigeons performing delayed matching-to-sample appear unwilling to request to see the sample again (or even for the first time) prior to choice, even if that choice would result in an increase in matching accuracy. In each of their four experiments, however, presentation (Experiments 3 & 4) or representation of the sample (Experiments 1 & 2) resulted in an added delay to reinforcement. Thus, the pigeons had to choose between an immediate reinforcer on about 50% of the trials and a delayed reinforcer on a significantly higher percentage of the trials. In the present research, when we equated the two alternatives for delay to reinforcement, we found that pigeons generally showed a significant preference for trials with a relevant sample over trials with an irrelevant sample. When the contingencies were reversed, most of the pigeons reversed their preference. Although these results do not present evidence for metacognition, they do show that pigeons are sensitive to the potential for a higher probability of reinforcement when delay to reinforcement is controlled. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Compound Measure of Hand-Foot-Eye Preference Masked Opposite Turning Behavior in Healthy Right-Handers and Non-Right-Handers: Technical Comment on Mohr et al. (2003).

A previous article reported opposite turning behavior in right-handers and non-right-handers (C. Mohr. T. Landis, H. S. Bracha, & P. Brugger, 2003; see record 2003-10460-031). This observation appears contradictory to the 1st study on long-term spontaneous turning behavior in healthy participants (H. S. Bracha, D. J. Seitz, J. Otemaa, & S. D. Click, 1987; see record 1987-33604-001). These latter authors found a complex interaction between hemispheric dominance, preferred turning side, and sex. C. Mohr et al. (2003) argued that the differentiation of the population in hemisphere-dominant groups by a compound measure of hand-foot-eye preference might have masked their recent finding. Thus, this commentary presents a reanalysis of the original data set (H. S. Bracha et al., 1987). Replicating recent observation, right-handers preferred left-sided turns; and non-righthanders, right-sided turns. This replication strengthens the proposition that handedness and turning behavior might depend on interhemispheric dopamine asymmetries. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Learning about sex: Conditioning of partner preference: Theoretical comment on Coria-Avila et al. (2005).

Sexual partner preference in female rats has been difficult to establish experimentally because the vaginocervical stimulation the female receives during the preference test can be rewarding or aversive depending on the context. G. A. Coria-Avila, A. J. Ouimet, P. Pacheco, J. Manzo, and J. G. Pfaus (2005) (see record 2005-06959-008) reported that female rats can be conditioned to show partner preference for a male that is scented with a sexually neutral odor if they are mated repeatedly with that male in a paced mating test. These results suggest that establishment of a partner preference depends on rewarding characteristics of the vaginocervical stimulation the female receives during an initial mating and that selection of a sexual partner can be determined by olfactory stimuli associated with that stimulation. These results are discussed within the context of the appetitive-consummatory construct of sexual behavior and the evolutionary significance of conditioned partner preference. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The sleep-like nature of early mammalian behavioral rhythms: Theoretical comment on Todd et al. (2010).

Early sleep patterns lack several of the major defining physiological criteria used to identify sleep states in adult animals, but many typical aspects of mature sleep can nevertheless be demonstrated at surprisingly early stages of development. In Todd, Gibson, Shaw, & Blumberg (2010), the ability to compensate for enforced sleep deprivation is found to be present already shortly after birth in laboratory rats, an altricial mammalian species. Whereas the brainstem is capable of resisting enforced wakefulness by an increasing “pressure” to fall asleep, “catch-up” replacement of the lost sleep by means of longer subsequent sleep durations requires forebrain participation. This investigation represents an initial foray into the theoretically important area of the ontogeny of homeostatic regulatory mechanisms for behaviorally crucial neurophysiological processes. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The mu-opioid receptor and the evolution of mother-infant attachment: Theoretical comment on Higham et al. (2011).

Genetic variation at a single nucleotide polymorphism (SNP) in the mu-opioid receptor gene (OPRM1) of both humans and rhesus macaques Macaca mulatta has been associated with differential affinity to the endogenous ligand beta-endorphin as well as alterations in pain sensitivity, drug and alcohol dependence, and social behaviors. The new study by Higham et al. (2011) presented in the current issue of this journal shows for the first time that some of the natural variation in maternal behavior observed in rhesus macaque populations can also be explained by genetic differences at this SNP. This work, in conjunction with other recent studies showing that genetic variability at this same locus are related to changes in infant attachment, provides unique insights into how opioids have been reutilized during evolution to coordinate the mother-infant relationship. (PsycINFO Database Record (c) 2011 APA, all rights reserved)