Pleasant Stimuli Research Articles

Choice, difficulty, and confidence in the brain

To provide a neurobiological basis for understanding decision-making and decision confidence, we describe and analyze a neuronal spiking attractor-based model of decision-making that makes predictions about synaptic and neuronal activity, the fMRI BOLD response, and behavioral choice as a function of the easiness of the decision, and thus decision confidence. The spiking network model predicts probabilistic decision-making with faster and larger neuronal responses on easy versus difficult choices, that is as the discriminability Δ I between the choices increases, and these and the synaptic currents in turn predict larger BOLD responses as the discriminability increases. Confidence, which increases with discriminability, thus emerges from the firing rates of the decision-making neurons in the choice attractor network. In two fMRI studies, we confirm these predictions by showing that brain areas such as medial prefrontal cortex area 10 implicated in choice decision-making between pleasant stimuli have BOLD activations linearly related to the easiness of both olfactory and warm pleasantness choices. Further, this signature is not found in orbitofrontal cortex areas that represent on a continuous scale the value of the stimuli, but are not implicated in the choice itself. This provides a unifying and fundamental approach to decision-making and decision confidence, and to how spiking-related noise in the brain affects choice, confidence, synaptic and neuronal activity, and fMRI signals.

Neurociências, artes gráficas e saúde pública: as novas advertências sanitárias para maços de cigarros

A exposição a produtos derivados do tabaco é considerada a mais importante causa de morte evitável no mundo. Ações de controle do tabagismo envolvem uma gama de intervenções para ajudar pessoas a parar de fumar e prevenir que jovens não se tornem dependentes. Advertências sanitárias com imagens mostradas em embalagens de cigarro são uma das formas mais efetivas de informar acerca das consequências do tabagismo. Pesquisas em neurobiologia da emoção demonstram que estímulos visuais afetam atitudes e comportamentos; estímulos agradáveis promovem predisposições para aproximação e os aversivos, afastamento. Os apelos positivos que o marketing da indústria tabagista induz em suas embalagens devem ser neutralizados por advertências que mostrem os riscos de fumar, desconstruindo o apelo prazeroso e induzindo predisposições de afastamento em relação ao produto.

Negative bias of processing ambiguously cued emotional stimuli

Daily we cope with upcoming potentially disadvantageous events. Therefore, it makes sense to be prepared for the worst case. Such a 'pessimistic' bias is reflected in brain activation during emotion processing. Healthy individuals underwent functional neuroimaging while viewing emotional stimuli that were earlier cued ambiguously or unambiguously concerning their emotional valence. Presentation of ambiguously announced pleasant pictures compared with unambiguously announced pleasant pictures resulted in increased activity in the ventrolateral prefrontal, premotor and temporal cortex, and in the caudate nucleus. This was not the case for the respective negative conditions. This indicates that pleasant stimuli after ambiguous cueing provided 'unexpected' emotional input, resulting in the adaptation of brain activity. It strengthens the hypothesis of a 'pessimistic' bias of brain activation toward ambiguous emotional events.

Effects of Transcranial Direct Current Stimulation on Episodic Memory Related to Emotional Visual Stimuli

The present study investigated emotional memory following bilateral transcranial electrical stimulation (direct current of 1 mA, for 20 minutes) over fronto-temporal cortical areas of healthy participants during the encoding of images that differed in affective arousal and valence. The main result was a significant interaction between the side of anodal stimulation and image emotional valence. Specifically, right anodal/left cathodal stimulation selectively facilitated the recall of pleasant images with respect to both unpleasant and neutral images whereas left anodal/right cathodal stimulation selectively facilitated the recall of unpleasant images with respect to both pleasant and neutral images. From a theoretical perspective, this double dissociation between the side of anodal stimulation and the advantage in the memory performance for a specific type of stimulus depending on its pleasantness supported the specific-valence hypothesis of emotional processes, which assumes a specialization of the right hemisphere in processing unpleasant stimuli and a specialization of the left hemisphere in processing pleasant stimuli. From a methodological point of view, first we found tDCS effects strictly dependent on the stimulus category, and second a pattern of results in line with an interfering and inhibitory account of anodal stimulation on memory performance. These findings need to be carefully considered in applied contexts, such as the rehabilitation of altered emotional processing or eye-witness memory, and deserve to be further investigated in order to understand their underlying mechanisms of action.

The “Anhedonia Paradox” in Schizophrenia: Insights from Affective Neuroscience

Emotional disturbances, and particularly anhedonia (the loss of pleasure), occupy a prominent place in conceptualizations of schizophrenia, including early writings by Bleuler and Kraepelin. Fitting these conceptualizations, hundreds of studies using clinical measures or self-report trait questionnaires have linked schizophrenia to reduced experiences of pleasure (1). In stark contrast to these findings, laboratory studies have shown that, when exposed to pleasant stimuli across modalities (e.g., visual, auditory, gustatory), individuals with schizophrenia typically report hedonic responses similar to those of controls (2,3). These sets of findings are puzzling: why do individuals with schizophrenia typically not endorse statements such as “Beautiful scenery has been a great delight to me” but do report normative emotional experiences when exposed to pictures of attractive scenery (4)? Are in-the-moment experiences of pleasure preserved in schizophrenia, and if so, how can we reconcile these findings with clinical observations of anhedonia? Finally, can neuroimaging provide any clues that could illuminate the “anhedonia paradox” in schizophrenia?

Predicting Odor Pleasantness with an Electronic Nose

A primary goal for artificial nose (eNose) technology is to report perceptual qualities of novel odors. Currently, however, eNoses primarily detect and discriminate between odorants they previously “learned”. We tuned an eNose to human odor pleasantness estimates. We then used the eNose to predict the pleasantness of novel odorants, and tested these predictions in naïve subjects who had not participated in the tuning procedure. We found that our apparatus generated odorant pleasantness ratings with above 80% similarity to average human ratings, and with above 90% accuracy at discriminating between categorically pleasant or unpleasant odorants. Similar results were obtained in two cultures, native Israeli and native Ethiopian, without retuning of the apparatus. These findings suggest that unlike in vision and audition, in olfaction there is a systematic predictable link between stimulus structure and stimulus pleasantness. This goes in contrast to the popular notion that odorant pleasantness is completely subjective, and may provide a new method for odor screening and environmental monitoring, as well as a critical building block for digital transmission of smell.

Predispositions to approach and avoid are contextually sensitive and goal dependent

The authors show that predispositions to approach and avoid do not consist simply of specific motor patterns but are more abstract functions that produce a desired environmental effect. It has been claimed that evaluating a visual stimulus as positive or negative evokes a specific motor response, extending the arm to negative stimuli, and contracting to positive stimuli. The authors showed that a large congruency effect (participants were faster to approach pleasant and avoid unpleasant stimuli, than to approach unpleasant and avoid pleasant stimuli) could be produced on a novel touchscreen paradigm (Experiment 1), and that the congruency effect could be reversed by spatial (Experiment 2) and nonspatial (Experiment 3) response effects. Thus, involuntary approach and avoid response activations are not fixed, but sensitive to context, and are specifically based on the desired goal.

Personality and lexical decision times for evaluative words

We studied personality influences on accessibility of pleasant and unpleasant stimuli in a sample of 129 students. Self‐reports and reports by knowledgeable informants on extraversion, neuroticism, approach temperament and avoidance temperament were combined with a go/no‐go lexical decision task that included pleasant, unpleasant and neutral words, and two response modes, manual and vocal. The data were analysed using multilevel modelling. Extraversion and approach temperament predicted faster identification of pleasant words than of neutral and of unpleasant words. Vocal responses took longer than manual responses, but mode of response did not interact with the valence of the words. Copyright © 2009 John Wiley & Sons, Ltd.

Delay discounting and future-directed thinking in anhedonic individuals

Anhedonia (lack of reactivity to pleasurable stimuli) and a negatively skewed view of the future are important components of depression that could affect economic decisions in depressed individuals. Delay discounting paradigms might be useful for probing putative affective and cognitive underpinnings of such decisions. As a first step to evaluate whether difficulties experiencing pleasure might affect delay discounting, 36 undergraduate students with varying levels of anhedonia performed a delay discounting task in which they made choices between a small immediate and larger future monetary reward. Increasing levels of anhedonia (Snaith–Hamilton Pleasure Scale) were negatively associated with delay discounting rate, indicating that anhedonic individuals tended to choose the larger, albeit delayed reward. These correlations remained after controlling for variables previously linked to delay discounting (working memory capacity and impulsivity) and pessimistic future-directed thinking. The current findings provide preliminary evidence indicating that anhedonic individuals make less myopic decisions about their future, possibly due to their decreased responsiveness to immediate rewards.

The effects of gender and catechol O-methyltransferase (COMT) Val108/158Met polymorphism on emotion regulation in velo-cardio-facial syndrome (22q11.2 deletion syndrome): An fMRI study

Velo-cardio-facial syndrome (VCFS) is caused by a micro-deletion of over 40 genes at the q11.2 locus of chromosome 22 and is a risk factor for the development of schizophrenia and other psychiatric disorders. COMT, one of the genes located in the deleted region, has been considered as a major candidate gene for genetic susceptibility in psychiatric diseases. Its functional polymorphism Val108/158Met has been shown to affect prefrontal function and working memory and has been associated with emotional dysregulation. We utilized a functional magnetic resonance imaging (fMRI) event-related paradigm to asses COMT genotype and gender-moderated effects on the neural activation that are elicited by viewing emotionally salient images charged with pleasant, unpleasant, and neutral content. Since estrogen down-regulates COMT activity resulting in lower COMT activity in women than men, we hypothesized an allele-by-gender interaction effect on neural activation. Participants included 43 VCFS individuals (Val/male=9, Val/female=17, Met/male=9, Met/female=8). We observed a gender effect on processing positive emotions, in that girls activated the cingulate gyrus more than boys did. We further observed a significant gender-by-allele interaction effect on neural function specific to the frontal lobe during the processing of pleasant stimuli, and specific to limbic regions during the processing of unpleasant stimuli. Our results suggest that in VCFS, the effect of the COMT Val108/158Met polymorphism is moderated by gender during the processing of emotional stimuli and could contribute to the understanding of the way in which this COMT polymorphism affects vulnerability to neuropsychiatric disorders.

The interaction of anticipatory anxiety and emotional picture processing: An event-related brain potential study

The present study examined the interaction of anticipatory anxiety and selective emotion processing. Toward this end, a rapid stream of pleasant, neutral, and unpleasant pictures was presented in alternating blocks of threat-of-shock or safety, which were signaled by colored picture frames. The main finding is that pleasant pictures elicited a sustained negative difference potential over occipital regions during threat as compared to safety periods. In contrast, unpleasant and neutral picture processing did not vary as a function of threat-of-shock. Furthermore, in both the safety and threat-of-shock conditions, emotional pictures elicited an enlarged early posterior negativity and late positive potential. These data show that the activation of the fear/anxiety network exerts valence-specific effects on affective picture processing. Pleasant stimuli mismatching the current state of anticipatory anxiety apparently draw more attentional resources.

Adverse experiences in childhood influence brain responses to emotional stimuli in adult psychiatric patients

Previous results suggest that early life stress (ELS) may be related to altered cortical responses to emotional stimuli. In a previous study, we found suppressed cortical responses to emotional pictures in psychiatric patients with high-ELS. The present study explored the stability of this effect across time and stimulation conditions. In addition, the relationship between ELS and current life stress was examined, and we probed whether this current life stress was related to the cortical responses. Fifteen patients with high, 16 patients with low-ELS and 15 psychiatrically healthy subjects with low-ELS participated in two sessions 8months apart. Subjects monitored a rapid serial presentation of pleasant, neutral and unpleasant pictures during magnetoencephalographic recording. In both sessions, estimated neural activity in occipital–parietal–temporal regions between 70 and 250ms after picture onset was smaller in patients, particularly in those with high-ELS, compared to healthy subjects. Modulation of activity by arousing (pleasant and unpleasant) compared to neutral stimuli around 200ms post-stimulus did not differ between groups, whereas around 300ms, patients did not show the pronounced cortical response to pleasant stimuli exhibited by healthy subjects. Results suggest that ELS and psychiatric disorder (1) diminish early perceptual processing (<200ms) of emotional stimuli without substantially affecting activity modulation by stimulus arousal value, (2) diminish later attention allocation processes (>300ms), and (3) are related to more recent life stress. High intraindividual correlations of activity patterns between sessions suggest lasting effects of ELS on processing modes.

Olfactory fMRI in Patients with Parkinson's Disease

Hyposmia is one of the early signs in idiopathic Parkinson's disease (PD). Olfactory stimuli were applied during fMRI scanning to show disease-related modulation of central nervous system structures and to advance our understanding of olfactory dysfunction in PD patients. All participants received either unpleasant stimuli that smelled like rotten eggs or pleasant ones that smelled like roses. Using a block design at a 1.5 T scanner we investigated a total of 8 PD patients (mean age 60 ± 10.9 years) and 13 age matched controls (mean age 58 ± 9.6 years). PD duration ranged from 1 to 9 years (mean 6.63 years); patients had an average “Unified Parkinson's Disease Rating Scale III” score of 23.25 (range, 6–46). Olfactory function was established using the “Sniffin’ Sticks” test battery. Patients tended to rate the stimuli presented during fMRI scans as less intense, but also as more pleasant than controls. fMRI results revealed differences between PD patients and controls which depended on the type of stimulation. While both pleasant and unpleasant stimulation was associated with lower activation in the amygdalo–hippocampal complex in patients compared to controls, increased activity in response to pleasant stimuli was observed in the striatum and the left inferior frontal gyrus. In contrast, unpleasant stimulation led to hypoactivation of the ventral striatum in patients (but not in controls) and did not enhance left inferior frontal activity. These results may partly reflect differences between PD patients and healthy controls in the processing of primary dimensions of odors, intensity, and valence.

Brain activations to emotional pictures are differentially associated with valence and arousal ratings

Several studies have investigated the neural responses triggered by emotional pictures, but the specificity of the involved structures such as the amygdala or the ventral striatum is still under debate. Furthermore, only few studies examined the association of stimuli's valence and arousal and the underlying brain responses. Therefore, we investigated brain responses with functional magnetic resonance imaging of 17 healthy participants to pleasant and unpleasant affective pictures and afterwards assessed ratings of valence and arousal. As expected, unpleasant pictures strongly activated the right and left amygdala, the right hippocampus, and the medial occipital lobe, whereas pleasant pictures elicited significant activations in left occipital regions, and in parts of the medial temporal lobe. The direct comparison of unpleasant and pleasant pictures, which were comparable in arousal clearly indicated stronger amygdala activation in response to the unpleasant pictures. Most important, correlational analyses revealed on the one hand that the arousal of unpleasant pictures was significantly associated with activations in the right amygdala and the left caudate body. On the other hand, valence of pleasant pictures was significantly correlated with activations in the right caudate head, extending to the nucleus accumbens (NAcc) and the left dorsolateral prefrontal cortex. These findings support the notion that the amygdala is primarily involved in processing of unpleasant stimuli, particularly to more arousing unpleasant stimuli. Reward-related structures like the caudate and NAcc primarily respond to pleasant stimuli, the stronger the more positive the valence of these stimuli is.

Dürer, Depression, and Melencolia

INTRODUCTION Albrecht Durer (1471-1528) was a prolific Renaissance printmaker and painter from Nuremberg, Germany. Of the many artistic works that he created, none has stimulated as much reflection and interpretation as his engraving entitled Melencolia I. The term “melancholy” dates back to the ancient theory of humorism, which postulated that a person’s health and temperament were controlled by the four body humors of black bile, yellow bile, phlegm, and blood. An overabundance of black bile was believed to cause excessive moodiness and inward reflection, characteristics similar to what we would call depression today. The word melancholy (melencolia being the archaic spelling) is a combination of the Greek words “melano” (black) and “chole” (bile). The central focus of this work is a despondent winged figure, her head resting on her hand as if its weight were too heavy to bear. The hair is tangled and her appearance unkempt. An emaciated-looking dog is curled at her feet while scattered about are various idled tools of creativity such as the caliper she holds in her hands. Over her right shoulder a downcast, scribbling cherub keeps vigil. Directly above her head an hourglass shows the sands of time quickly running out. The “magic” square next to the hourglass contains various numbers which add up to 34 in all directions. The two bottom center numbers, 15 and 14, reflect the date of the work — 1514. The seven-rung ladder in the background is commonly thought to be an allegorical reference to the seven metals of the ancient tradition of alchemy, with the large polyhedron at the bottom representing the base metal lead. In the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV), melancholia is described as a more severe form of depression, characterized by both a pervasive loss of interest or pleasure and an inability to respond to pleasurable stimuli. The World Health Organization calls depression the leading cause of disability worldwide and in 2000 ranked it as the fourth highest contributor to the global burden of disease.1 Although depression is one of the most common disorders encountered in primary care, studies indicate that the illness continues to be significantly underdiagnosed and undertreated.2 Durer’s forlorn angel is an artistic and vivid reminder of the severe morbidity associated with depression, a disorder that today can generally be successfully managed if it is properly diagnosed and treated.

An increase in stimulus arousal has differential effects on the processing speed of pleasant and unpleasant stimuli

The arousal value of a stimulus influences its salience, whereby higher arousal should lead to faster processing. However, in previous research, participants consistently made faster valence judgments for low arousal, pleasant stimuli than for high arousal, pleasant stimuli. The speed of valence and arousal judgments for pictures and words were investigated in three experiments. Valence judgments were faster for low arousal than for high arousal pleasant pictures and for high arousal than for low arousal unpleasant pictures and words. Moreover, arousal judgments were faster for low arousal than high arousal pleasant and for high arousal than low arousal unpleasant pictures and words. The current research confirms that the impact of valence and arousal on processing speed does not reflect on the labels (valence versus arousal) used when recording speeded judgments. Similarly to valence, stimulus arousal interacts differentially with the evaluation of pleasant and unpleasant stimuli producing a processing advantage for high arousal, unpleasant stimuli but not high arousal, pleasant stimuli.

The Effects of Psychotherapy on Neural Responses to Rewards in Major Depression

Unipolar major depressive disorder (MDD) is characterized by anomalous neurobiological responses to pleasant stimuli, a pattern that may be linked to symptoms of anhedonia. However, the potential for psychotherapy to normalize neurobiological responses to pleasant stimuli has not been evaluated. Twelve adults with and 15 adults without MDD participated in two identical functional magnetic resonance imaging scans that used a Wheel of Fortune task. Between scans, MDD outpatients received Behavioral Activation Therapy for Depression, a psychotherapy modality designed to increase engagement with rewarding stimuli and reduce avoidance behaviors. Seventy-five percent of adults with MDD were treatment responders, achieving post-treatment Hamilton Rating Scale for Depression score of six or below. Relative to changes in brain function in the matched nondepressed group, psychotherapy resulted in functional changes in structures that mediate responses to rewards, including the paracingulate gyrus during reward selection, the right caudate nucleus (i.e., the dorsal striatum), during reward anticipation, and the paracingulate and orbital frontal gyri during reward feedback. There was no effect of diagnostic status or psychotherapy on in-scanner task-related behavioral responses. Behavioral Activation Therapy for Depression, a psychotherapy modality designed to increase engagement with rewarding stimuli and reduce avoidance behaviors, results in improved functioning of unique reward structures during different temporal phases of responses to pleasurable stimuli, including the dorsal striatum during reward anticipation.

Psychophysiological and Self-Reported Emotional Responding in Alcohol-Dependent College Students: The Impact of Brief Acceptance/Mindfulness Instruction

Drinking motivated by the desire to cope with painful emotions has been shown to be strongly related to alcohol dependence; the resulting maladaptive pattern of substance use can, therefore, be conceptualized as a form of experiential avoidance (an attempt to decrease contact with unpleasant internal states). Acceptance-based interventions, which specifically address experiential avoidance, are multifaceted, and the mechanisms of action are only beginning to be understood. Using a treatment analogue design to look at the underlying components of acceptance-based interventions, the authors tested the effects of brief mindfulness instructions on the emotional responding of alcohol-dependent college students and compared these results with those from a sample of nondependent students. Multidimensional self-reported and psychophysiological emotional responses to pleasant, unpleasant, and neutral pictorial stimuli did not differ between alcohol-dependent and nondependent participants or between the alcohol-dependent participants receiving the mindfulness versus neutral condition. Alcohol-dependent participants' severity of alcohol dependence was found to be related to both self-reported and psychophysiological responses to the unpleasant pictures; these results support the notion that alcohol-dependent participants may use alcohol to cope with unpleasant emotions.

How the Brain Represents the Reward Value of Fat in the Mouth

The palatability and pleasantness of the sensory properties of foods drive food selection and intake and may contribute to overeating and obesity. Oral fat texture can make food palatable and pleasant. To analyze its neural basis, we correlated humans' subjective reports of the pleasantness of the texture and flavor of a high- and low-fat food with a vanilla or strawberry flavor, with neural activations measured with functional magnetic resonance imaging. Activity in the midorbitofrontal and anterior cingulate cortex was correlated with the pleasantness of oral fat texture and in nearby locations with the pleasantness of flavor. The pregenual cingulate cortex showed a supralinear response to the combination of high fat and pleasant, sweet flavor, implicating it in the convergence of fat texture and flavor to produce a representation of highly pleasant stimuli. The subjective reports of oral fattiness were correlated with activations in the midorbitofrontal cortex and ventral striatum. The lateral hypothalamus and amygdala were more strongly activated by high- versus low-fat stimuli. This discovery of which brain regions track the subjective hedonic experience of fat texture will help to unravel possible differences in the neural responses in obese versus lean people to oral fat, a driver of food intake.

Neural representation of reward in recovered depressed patients

IntroductionAnhedonia, a loss of interest and pleasure in normally rewarding stimuli, is a key diagnostic criterion for major depression. It has been suggested that deficits in the processing of reward-relevant stimuli could represent an endophenotype for depression. We hypothesized that people at risk of depression by virtue of a personal history of the illness would show impaired neural responses to a primary rewarding stimulus.Materials and methodsUsing functional magnetic resonance imaging, we measured the neural response to the sight and flavor of chocolate, and their combination, in 13 unmedicated recovered patients with a history of major depression and 14 healthy controls matched for age and gender. We also examined a control aversive condition consisting of the sight of moldy strawberries and a corresponding unpleasant taste. Participants simultaneously recorded subjective ratings of “pleasantness,” “intensity,” and “wanting.”Results and discussionDespite no differences between the groups in stimulus ratings, patients showed decreased neural responses to the pleasant stimulus in the ventral striatum and increases in the caudate nucleus to the aversive stimulus. Furthermore, patients had a diminished neural supralinearity response (the potentiation produced by simultaneous presentation of the sight and flavor of the stimuli) in the prefrontal cortex for both aversive and pleasant conditions. Patients recovered from depression appear to have deficits in the neural basis of reward and may also have impairments in the cross-modal integration of sensory stimuli.ConclusionThese findings support the view that abnormal neural responses to reward may be an endophenotype for depression and a potential target for intervention and prevention strategies.