Dissociating the role of dACC and dlPFC for emotion appraisal and mood regulation using cathodal tDCS.

Several neuroimaging studies have shown that a distributed network of brain regions is involved in our ability to appraise the emotions we experience in daily life. In particular, scholars suggested that the dorsal anterior cingulate cortex (dACC) may play a role in the appraisal of emotional stimuli together with subcortical regions, especially when stimuli are negatively valenced, and the dorsolateral prefrontal cortex (dlPFC) may play a role in regulating emotions. However, proofs of the causal role of these regions are lacking. In the present study, we aim at testing this model by stimulating both the dACC and the left dlPFC via cathodal tDCS. Twenty-four participants were asked to attend and rate the arousal and valence of negative and neutral emotional stimuli (pictures and words) in three different experimental sessions: cathodal stimulation of dACC, left dlPFC, or sham. In addition to the experimental task, the baseline affective state was measured before and after the stimulation to further assess the effect of stimulation over the baseline affective state after the experimental session. Results showed that cathodal stimulation of dACC, but not the left dlPFC, was associated with reduced arousal ratings of emotional stimuli, both compared with the sham condition. Moreover, cathodal stimulation of left dlPFC decreased participant's positive affective state after the session. These findings suggest for the first time, a dissociation between the dACC and dlPFC, with the former more involved in emotion appraisal, and the latter more involved in mood modulation.

Implicit and explicit safety evaluation of foods: The importance of food processing.

Identifying beneficial foods in the environment, while avoiding ingesting something toxic, is a crucial task humans face on a daily basis. Here we directly examined adults' implicit and explicit safety evaluations of the same foods presented with different degrees of processing, ranging from unprocessed (raw) to processed (cut or cooked). Moreover, we investigated whether individual characteristics (e.g., Body Mass Index, food neophobia and hunger) modulated their evaluations. We hypothesized that adults would associate the processed form of a food with safety more than its unprocessed form since processing techniques, which are ubiquitously applied in different cultures, often reduce the toxicity of foods, and signal previous human intervention and intended consumption. Adults (N = 109, 43 females) performed an implicit Go/No-Go association task (GNAT) online, assessing the association between safety attributes and food images differing on their degree of processing, both unfamiliar and familiar foods were used. Then each food was explicitly evaluated. Results revealed that individual self-reported characteristics affected both implicit and explicit evaluations. Individuals with excess weight and obesity had a strong and positive implicit association between processed foods and safety attributes, but explicitly rated cooked foods as the least safe overall, this latter result was found in highly neophobic individuals as well. Yet, at the explicit level, when looking at unfamiliar foods only, processed foods were rated safer than unprocessed foods by all participants. Our results are the first evidence that directly highlights the relevance of the degree of processing in food safety evaluation and suggest that thinking of the important tasks humans face regarding food selection enriches our understanding of food behaviors.

Food olfactory cues reactivity in individuals with obesity and the contribution of alexithymia.

Obesity has been associated with increased reward sensitivity to food stimuli, but a few studies have addressed this issue by using odors. This study investigated whether obesity is associated with increased liking and wanting of food odors and whether alexithymia, a psychological construct characterized by diminished affective abilities, contributes to altered responsiveness to food. Liking and wanting for food and pleasant non-food odors were measured through explicit (self-report ratings) and implicit measures (heart rate and skin conductance) in 23 women with healthy weight (HW) and 20 women with overweight/obesity (OW/OB). Differently from the HW group, the OW/OB group explicitly liked food odors less than non-food odors; but, at the implicit level, there were no differences in heart rate response for both types of odors, indicating that they were equally liked. Moreover, at variance with the HW group, the OW/OB group did not exhibit increased skin conductance response for food compared to nonfood odors. Alexithymia was associated with increased implicit liking and explicit wanting of food odors, in particular in the HW group. These findings show that obesity is characterized by high levels of implicit food liking and low levels of implicit food wanting. Moreover, both affective and motivational responses to food reward seem to be affected by alexithymia, which should be taken into account by studies evaluating the effect of cue exposure intervention for obesity treatment.

The neural substrates of subliminal attentional bias and reduced inhibition in individuals with a higher BMI: A VBM and resting state connectivity study.

Previous studies have shown that individuals with overweight and obesity may experience attentional biases and reduced inhibition toward food stimuli. However, evidence is scarce as to whether the attentional bias is present even before stimuli are consciously recognized. Moreover, it is not known whether or not differences in the underlying brain morphometry and connectivity may co-occur with attentional bias and impulsivity towards food in individuals with different BMIs. To address these questions, we asked fifty-three participants (age M = 23.2, SD = 2.9, 13 males) to perform a breaking Continuous Flash Suppression (bCFS) task to measure the speed of subliminal processing, and a Go/No-Go task to measure inhibition, using food and nonfood stimuli. We collected whole-brain structural magnetic resonance images and functional resting-state activity. A higher BMI predicted slower subliminal processing of images independently of the type of stimulus (food or nonfood, p = 0.001, εp2 = 0.17). This higher threshold of awareness is linked to lower grey matter (GM) density of key areas involved in awareness, high-level sensory integration, and reward, such as the orbitofrontal cortex [t = 4.55, p = 0.003], the right temporal areas [t = 4.18, p = 0.002], the operculum and insula [t = 4.14, p = 0.005] only in individuals with a higher BMI. In addition, individuals with a higher BMI exhibit a specific reduced inhibition to food in the Go/No-Go task [p = 0.02, εp2 = 0.02], which is associated with lower GM density in reward brain regions [orbital gyrus, t = 4.97, p = 0.005, and parietal operculum, t = 5.14, p < 0.001] and lower resting-state connectivity of the orbital gyrus to visual areas [fusiform gyrus, t = -4.64, p < 0.001 and bilateral occipital cortex, t = -4.51, p < 0.001 and t = -4.34, p < 0.001]. Therefore, a higher BMI is predictive of non food-specific slower visual subliminal processing, which is linked to morphological alterations of key areas involved in awareness, high-level sensory integration, and reward. At a late, conscious stage of visual processing a higher BMI is associated with a specific bias towards food and with lower GM density in reward brain regions. Finally, independently of BMI, volumetric variations and connectivity patterns in different brain regions are associated with variability in bCFS and Go/No-Go performances.

Neural correlates of the energetic value of food during visual processing and response inhibition.

Previous research showed that human brain regions involved in reward and cognitive control are responsive to visually presented food stimuli, in particular high-energy foods. However, it is still to be determined whether the preference towards high-energy foods depends on their higher energy density (kcal/gram), or is based on the difference in energy content of the food items (total amount of kcal). Here we report the results of an fMRI study in which normal-weight healthy participants processed food images during a one-back task or were required to inhibit their response towards food stimuli during a Go/No-Go task. High-energy density (HD) and low-energy density (LD) foods were matched for energy content displayed. Food-related kitchen objects (OBJ) were used as control stimuli. The lateral occipital complex and the orbitofrontal cortex showed consistent higher activity in response to HD than LD foods, both during visual processing and response inhibition. This result suggests that images of HD foods, even when the amount of food shown is not associated with a higher energy content, elicit preferential visual processing - possibly involving attentional processes - and trigger a response from the reward system. We conclude that the human brain is able to distinguish food energy densities of food items during both active visual processing and response inhibition.

A hierarchical-drift diffusion model of the roles of hunger, caloric density and valence in food selection.

Decisions based on affectively relevant stimuli, such as food items, hardly follow strictly rational rules. Being hungry, the food's caloric density, and the subjective valence attributed to various foods are known factors that modulate food choices. Yet, how these factors relatively and altogether contribute to the food choice process is still unknown. In this study, we showed 16 healthy young adults low- and high-calorie food when hungry or fed, and we asked them to evaluate the valence of each visually-presented food. To compute the relative influence of hunger, caloric density and valence on food choice, we applied a hierarchical drift diffusion model (HDDM). Results indicated that hunger, caloric density and valence affected how fast participants accumulated information in favor of the chosen item over the other. When fed, participants were faster in choosing low-calorie foods and foods with a higher valence. Conversely, when hungry, participants were faster in choosing high-calorie foods, including food items with lower subjective valence. All in all, these findings confirm the complex nature of food choices and the usefulness of nuanced computational models to address the multifaceted nature of decision-making and value assessment processes affecting food selection.

The emotional control of action: ERP evidence.

It is known that unpleasant emotions can modulate the speed of involuntary movements, yet the effects of aversive stimulation on voluntary motor acts have not been systematically investigated. The effects of aversive stimulation on subsequent movement-related cortical activity were examined using a task invalving compatible and incompatible movements. Negative shifts in the timing of two motor event-related potentials were found subsequent to aversive stimulation for compatible movements only. With analogy to the Fear-Potentiated Startle Reflex, a reactive mechanism affecting covert action, these Fear-Potentiated Movement-Related Potentials (FPMPs) reflect preparation for overt actions performed to cope with particular types of danger. Further analysis revealed a positive deflection in the left frontal cortex prior the execution of incompatible movements, which may reflect inhibitory suppression of externally-triggered imitative tendencies.

Deep brain stimulation of the subthalamic nucleus and the temporal discounting of primary and secondary rewards.

Although deep brain stimulation of the subthalamic nucleus is an effective surgical treatment for Parkinson's disease, it may expose patients to non-motor side effects such as increased impulsivity and changes in decision-making behavior. Even if several studies have shown that stimulation of the subthalamic nucleus increases the incentive salience of food rewards in both humans and animals, temporal discounting for food rewards has never been investigated in patients who underwent STN-DBS. In this study, we measured inter-temporal choice after STN-DBS, using both primary and secondary rewards. In particular, PD patients who underwent STN-DBS (in ON medication/ON stimulation), PD patients without STN-DBS (in ON medication) and healthy matched controls (C) performed three temporal discounting tasks with food (primary reward), money and discount vouchers (secondary rewards). Participants performed also neuropsychological tests assessing memory and executive functions. Our results show that STN-DBS patients and PD without DBS behave as healthy controls. Even PD patients who after DBS experienced weight gain and/or eating alterations did not show an increased temporal discounting for food rewards. Interestingly, patients taking a higher dosage of dopaminergic medications, fewer years from DBS surgery and, unexpectedly, with better episodic memory were also those who discounted rewards more. In conclusion, this study shows that STN-DBS does not affect temporal discounting of primary and secondary rewards. Furthermore, by revealing interesting correlations between clinical measures and temporal discounting, it also shed light on the clinical outcomes that follow STN-DBS in patients with PD.

How brain response and eating habits modulate food energy estimation.

The estimates we do of the energy content of different foods tend to be inaccurate, depending on several factors. The elements influencing such evaluation are related to the differences in the portion size of the foods shown, their energy density (kcal/g), but also to individual differences of the estimators, such as their body-mass index (BMI) or eating habits. Within this context the contribution of brain regions involved in food-related decisions to the energy estimation process is still poorly understood. Here, normal-weight and overweight/obese women with restrained or non-restrained eating habits, received anodal transcranial direct current stimulation (AtDCS) to modulate the activity of the left dorsolateral prefrontal cortex (dlPFC) while they performed a food energy estimation task. Participants were asked to judge the energy content of food images, unaware that all foods, for the quantity presented, shared the same energy content. Results showed that food energy density was a reliable predictor of their energy content estimates, suggesting that participants relied on their knowledge about the food energy density as a proxy for estimating food energy content. The neuromodulation of the dlPFC interacted with individual differences in restrained eating, increasing the precision of the energy content estimates in participants with higher scores in the restrained eating scale. Our study highlights the importance of eating habits, such as restrained eating, in modulating the activity of the left dlPFC during food appraisal.

Recognition by action: dissociating visual and semantic routes to action in normal observers.

In this article the operation of a direct visual route to action in response to objects, in addition to a semantically mediated route, is demonstrated. Four experiments were conducted in which participants made gesturing or naming responses to pictures under deadline conditions. There was a cross-over interaction in the number of visual errors relative to the number of semantic plus semantic-visual errors in the two tasks: In gesturing, compared with naming, participants made higher proportions of visual errors and lower proportions of semantic plus semantic-visual errors (Experiments 1, 3, and 4). These results suggest that naming and gesturing are dependent on separate information-processing routes from stimulus to response, with gesturing dependent on a visual route in addition to a semantic route. Partial activation of competing responses from the visual information present in objects (mediated by the visual route to action) leads to high proportions of visual errors under deadline conditions. Also, visual errors do not occur when gestures are made in response to words under a deadline (Experiment 2), which indicates that the visual route is specific to seen objects.

Intermittent alien hand syndrome and callosal apraxia in multiple sclerosis: implications for interhemispheric communication.

We report a case of a 47-year-old woman with 35-year history of multiple sclerosis, who showed alien hand signs, a rare behavioural disorder that involves unilateral goal-directed movements that are contrary to the individual's intention. Alien hand syndrome has been described in multiple sclerosis (MS) only occasionally and is generally suggestive of callosal disconnection. The patient presented also with bilateral limb apraxia and left hand agraphia, raising the possibility of cortical dysfunction or disconnection, in addition to corpus callosum and white matter involvement. Her specific pattern of symptoms supports the role of the corpus callosum in interhemispheric communication for complex as well as fine motor activities and may indicate that it can serve as both an inhibitory and excitatory function depending on task demands.

Cognitive neuroscience of actions: a whole is greater than the sum of its parts.

The purpose of the present issue of Brain and Cognition is to demonstrate that the strength of neuroscience is in its multidisciplinary approach to understand events. Here we are concerned with the domain of action recognition and production. Seven articles have been selected as representative studies of actions carried out in different areas of neuroscience such as neuropsychology, neurophysiology, and cognitive science. Although each addresses different questions within the field, the articles share a common neuroscientific knowledge, as can be readily gathered from the references cited in each article.

A form of ideational apraxia as a delective deficit of contention scheduling.

In this paper we studied three brain-damaged patients: the first two, DR and FG, had limb apraxia whilst the third was a control patient (WH2) with an executive function disorder but without limb apraxia. DR and FG were impaired in carrying out everyday actions, whilst they maintained the ability to sequence photographs representing those same activities. The failure in the action production task was not caused by visual agnosia for objects, as the patients could recognise them from sight. Nor was it produced by a loss of knowledge about their functions (De Renzi & Lucchelli, 1988), as DR and FG could identify objects from descriptions of their use. WH2's pattern of performance doubly dissociated from that of the apraxic patients, namely spared action production on the multiple object test, but faulty sequencing of photographs. WH2's difficulties in sequencing photographs were not due to a failure to understand the task, as she could sequence stimuli other than actions (e.g., shapes and numbers). Nor were the differences due to a loss of knowledge about the actions, since she could perform and identify them from photographs. These results show that the kind of apraxia observed in DR and FG is not produced by a degraded action sequence representation (Lehmkuhl & Poeck, 1981; Poeck & Lehmkuhl, 1980). We interpreted our results within a contention scheduling model (Cooper & Shallice, 2000; Norman & Shallice, 1986).

The selective impairment of the phonological output buffer.

A single case study is presented of a patient, LT, with a reproduction conduction aphasic pattern of performance on word reproduction tasks; thus he made substitutions, insertions, deletions, and transpositions in reading, writing, and repetition of words and nonwords, as well as in sentence production, and in spoken and written picture and action naming. Further analyses revealed that there was no effect of semantic or syntactic structure on performance, and that reading was slightly better than repetition and writing. Finally, the observed effects of lexicality, length, and word frequency were similar to those found in other phonological output buffer patients. Overall, the pattern observed fits the characteristics typical of phonological output buffer patients, as characterised by Caramazza, Miceli, and Villa (1986). We discuss the implications of these results for understanding the role of the output phonological buffer in neuropsychological and computational models of writing, reading, and repetition. From the perspective of LT's performance, the hypothesis suggested by Caramazza et al. (1986), and that of Hartley and Houghton (1996), that word production in reading and repetition uses an additional route to access articulatory or phoneme-level representations from the phonological output lexicon, is unnecessary; instead, word-nonword differences in other patients can be attributed to resource demand differences between the two types of stimuli. LT's preserved span fit with the assumption that two phonological buffers exist, one for input and the other for output. Results from a word repetition experiment, in which word syllable structure was manipulated, are in conflict with one further noncentral aspect of the Hartley and Houghton's model, which otherwise fits the results well.