Patterns of Brain Activation when Mothers View Their Own Child and Dog: An fMRI Study

Neural substrates underlying the human-pet relationship are largely unknown. We examined fMRI brain activation patterns as mothers viewed images of their own child and dog and an unfamiliar child and dog. There was a common network of brain regions involved in emotion, reward, affiliation, visual processing and social cognition when mothers viewed images of both their child and dog. Viewing images of their child resulted in brain activity in the midbrain (ventral tegmental area/substantia nigra involved in reward/affiliation), while a more posterior cortical brain activation pattern involving fusiform gyrus (visual processing of faces and social cognition) characterized a mother's response to her dog. Mothers also rated images of their child and dog as eliciting similar levels of excitement (arousal) and pleasantness (valence), although the difference in the own vs. unfamiliar child comparison was larger than the own vs. unfamiliar dog comparison for arousal. Valence ratings of their dog were also positively correlated with ratings of the attachment to their dog. Although there are similarities in the perceived emotional experience and brain function associated with the mother-child and mother-dog bond, there are also key differences that may reflect variance in the evolutionary course and function of these relationships

A Single Dose of Nicotine Enhances Reward Responsiveness in Nonsmokers: Implications for Development of Dependence

Background: Tobacco smoking, driven by the addictive properties of nicotine, is the most prevalent preventable cause of death in the Western world. Accumulated evidence suggests that nicotine may increase appetitive responding for nondrug incentives in the environment. Methods: To test this hypothesis, we conducted a randomized, double-blind, placebo-controlled, crossover study of the effect of a single dose of transdermal nicotine on reward responsiveness in 30 psychiatrically healthy nonsmokers. A novel signal detection task in which correct responses were differentially rewarded in a 3:1 ratio was used to assess the extent to which participants modulated their behavior as a function of reward. Results: Despite expected adverse effects such as nausea, nicotine significantly increased response bias toward the more frequently rewarded condition, at the expense of accuracy, independent of effects on attention or overall vigilance. Additionally, response bias on placebo was greater in participants who received nicotine in the first session, indicating that an effect of nicotine on reward responsiveness or reward-based learning persisted for at least 1 week. Conclusions: These findings suggest that a single dose of nicotine enhances response to non-drug-related rewards in the environment, with lasting effects. This effect may contribute to reinforcement of early smoking behavior and development of nicotine dependence.Psycholog

Single Dose of a Dopamine Agonist Impairs Reinforcement Learning in Humans: Evidence from Event-related Potentials and Computational Modeling of Striatal-Cortical Function

Animal findings have highlighted the modulatory role of phasic dopamine (DA) signaling in incentive learning, particularly in the acquisition of reward-related behavior. In humans, these processes remain largely unknown. In a recent study, we demonstrated that a single low dose of a D2/D3 agonist (pramipexole) - assumed to activate DA autoreceptors and thus reduce phasic DA bursts - impaired reward learning in healthy subjects performing a probabilistic reward task. The purpose of this study was to extend these behavioral findings using event-related potentials and computational modeling. Compared with the placebo group, participants receiving pramipexole showed increased feedback-related negativity to probabilistic rewards and decreased activation in dorsal anterior cingulate regions previously implicated in integrating reinforcement history over time. Additionally, findings of blunted reward learning in participants receiving pramipexole were simulated by reduced presynaptic DA signaling in response to reward in a neural network model of striatal-cortical function. These preliminary findings offer important insights on the role of phasic DA signals on reinforcement learning in humans and provide initial evidence regarding the spatiotemporal dynamics of brain mechanisms underlying these processes.Psycholog

Single Dose of a Dopamine Agonist Impairs Reinforcement Learning in Humans: Behavioral Evidence from a Laboratory-based Measure of Reward Responsiveness

Rationale. The dopaminergic system, particularly D2-like dopamine receptors, has been strongly implicated in reward processing. Animal studies have emphasized the role of phasic dopamine (DA) signaling in reward-related learning, but these processes remain largely unexplored in humans. Objectives. To evaluate the effect of a single, low dose of a D2/D3 agonist-pramipexole-on reinforcement learning in healthy adults. Based on prior evidence indicating that low doses of DA agonists decrease phasic DA release through autoreceptor stimulation, we hypothesized that 0.5 mg of pramipexole would impair reward learning due to presynaptic mechanisms. Materials and methods. Using a double-blind design, a single 0.5-mg dose of pramipexole or placebo was administered to 32 healthy volunteers, who performed a probabilistic reward task involving a differential reinforcement schedule as well as various control tasks. Results. As hypothesized, response bias toward the more frequently rewarded stimulus was impaired in the pramipexole group, even after adjusting for transient adverse effects. In addition, the pramipexole group showed reaction time and motor speed slowing and increased negative affect; however, when adverse physical side effects were considered, group differences in motor speed and negative affect disappeared. Conclusions. These findings show that a single low dose of pramipexole impaired the acquisition of reward-related behavior in healthy participants, and they are consistent with prior evidence suggesting that phasic DA signaling is required to reinforce actions leading to reward. The potential implications of the present findings to psychiatric conditions, including depression and impulse control disorders related to addiction, are discussed.Psycholog

fMRI results for main effect of relationship (own vs. unfamiliar) in brain regions of interest.

a<p>Neurosynth term/function (<a href="http://www.neurosynth.org" target="_blank">www.neurosynth.org</a>); N/A  =  not available in the Neurosynth atlas.</p>b<p>Hemisphere: R, right, L, left</p>c<p>Cluster size; number of contiguous voxels with p< 0.01.</p>d<p>x, y, and z coordinates in MNI space.</p>e<p>Familywise error corrected at the cluster level.</p><p>All results significant at <i>p</i>< .05, cluster-level family-wise error correction.</p><p>Follow-up t-tests revealed all significant main effects were the result of greater brain activation in the own vs. unfamiliar (own > unfamiliar) contrast. There were no significant differences in ROI activation for the unfamiliar > own contrast.</p><p>fMRI results for main effect of relationship (own vs. unfamiliar) in brain regions of interest.</p

fMRI results for the own dog > fixation contrast in brain regions of interest (n = 14).

a<p>Neurosynth term/function (<a href="http://www.neurosynth.org" target="_blank">www.neurosynth.org</a>).</p>b<p>Hemisphere: R, right, L, left.</p>c<p>Cluster size; number of contiguous voxels with p<0.05.</p>d<p>x, y, and z coordinates in MNI space.</p>e<p>Familywise error corrected at the cluster level.</p><p>All results significant at <i>p</i>< .05, cluster-level family-wise error correction.</p><p>fMRI results for the own dog > fixation contrast in brain regions of interest (n = 14).</p

Brain activation maps and graphs for the own dog vs. own child contrast.

<p>There was greater activation for the own dog vs. own child contrast in fusiform gyrus (A) and less deactivation for own child vs. own dog contrast in NAcc/ventral striatum (B). Other conventions the same as in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0107205#pone-0107205-g002" target="_blank">Figure 2</a>.</p

fMRI results for own child > unfamiliar child contrast in brain regions of interest (n = 14).

a<p>Neurosynth term/function (<a href="http://www.neurosynth.org" target="_blank">www.neurosynth.org</a>).</p>b<p>Hemisphere: R, right, L, left.</p>c<p>Cluster size; number of contiguous voxels with p<0.01.</p>d<p>x, y, and z coordinates in MNI space.</p>e<p>Familywise error corrected at the cluster level.</p><p>All results significant at <i>p</i>< .05, cluster-level family-wise error correction.</p><p>There were no significant differences for the own dog vs. unfamiliar dog contrast.</p><p>fMRI results for own child > unfamiliar child contrast in brain regions of interest (n = 14).</p

Participant Characteristics (n = 14).

<p>IQ  =  Weschler Test of Adult Reading Full Scale IQ.</p><p>LAPS  =  Lexington Attachment to Pets Scale (higher score means greater level of attachment).</p><p>Participant Characteristics (n = 14).</p