Emotional response inhibition in children with attention-deficit/hyperactivity disorder: neural and behavioural data.

BACKGROUND: Although both emotion and response inhibition are thought to be important in attention-deficit/hyperactivity disorder (ADHD), little is known about the neural mechanisms that underlie the interaction between these two processes in patients with this disorder. This study aimed at examining how emotional contexts affect inhibitory control in children with ADHD. METHOD: A total of 24 ADHD children and 24 healthy comparison subjects performed a modified go/no-go task during three different emotionally laden contexts: negative, neutral and positive. To explore the timing and the underlying neural substrates of emotion-modulated response inhibition, event-related potentials were measured and further analysed both at the scalp and at the voxel level. RESULTS: Patients with ADHD showed greater activation of inhibition-related neural mechanisms (i.e. no-go P3 amplitudes and orbitofrontal cortex activity) to maintain a similar level of performance as healthy comparison subjects, especially during the emotionally arousing contexts (negative and positive). CONCLUSIONS: This study provides plausible neural mechanisms for the difficulty that ADHD children have in controlling their behaviour in highly emotional situations. Such emotional contexts might increase the need for top-down inhibitory control and put ADHD children at greater risk for impulsive behaviours and emotional dysregulation.

Temporospatial analysis of explicit and implicit processing of negative content during word comprehension.

Although divergences between explicit and implicit processing of affective content during word comprehension have been reported, the underlying nature of those differences remains in dispute. Prior studies focused on either the timing or the spatial location of the effects. The present study examined the precise dynamics of the processing of negative words when attention is directed to affective content or to non-emotional properties by capitalizing on fine temporal resolution of the event-related potentials (ERPs) and recent advances in source localization. Tasks were used that required accessing knowledge about different semantic properties of negative and neutral words. In the direct task, participants' attention was directed towards emotional information. By contrast, subjects had to decide whether the words' referent could be touched or not in the indirect task. Regardless of being processed explicitly or implicitly, negative compared to neutral words were associated with more errors and greater key pressure responses. Electrophysiologically, affective processing was reflected in larger amplitudes to negative words in a late positive component (LPC) at the scalp level, and in increased activity in the pre-supplementary motor area (pre-SMA) at the voxel level. Interestingly, an interaction between emotion and type of task was observed. Negative words were associated with more errors, larger anterior distributed LPC amplitudes and increased activity in the posterior cingulate cortex (PCC) in the direct compared to the indirect task. This LPC effect was modulated by the concreteness of the words. Finally, a task effect was found in a posterior negativity around 220ms, with enhanced amplitudes to words in the direct compared to the indirect task. The present results suggest that negative information contained in written language is processed irrespective of controlled attention is directed to it or not, but that this processing is reinforced in the former case.

N170 sensitivity to facial expression: A meta-analysis.

The N170 component is the most important electrophysiological index of face processing. Early studies concluded that it was insensitive to facial expression, thus supporting dual theories postulating separate mechanisms for identity and expression encoding. However, recent evidence contradicts this assumption. We conducted a meta-analysis to resolve inconsistencies and to derive theoretical implications. A systematic revision of 128 studies analyzing N170 in response to neutral and emotional expressions yielded 57 meta-analyzable experiments (involving 1645 healthy adults). First, the N170 was found to be sensitive to facial expressions, supporting proposals arguing for integrated rather than segregated mechanisms in the processing of identity and expression. Second, this sensitivity is heterogeneous, with anger, fear and happy faces eliciting the largest N170 amplitudes. Third, we explored some modulatory factors, including the focus of attention - N170 amplitude was found to be also sensitive to unattended expressions - or the reference electrode -common reference reinforcing the effects- . In sum, N170 is a valuable tool to study the neural processing of facial expressions in order to develop current theories.

Semantic processing of open- and closed-class words: an event-related potentials study.

Previous research on open- and closed-class words has revealed the existence of several differences in the processing of these types of vocabulary. In this paper the processing of open- and closed-class words was compared by means of an early electrical brain response, recognition potential (RP), which indexes semantic processing and originates from basal extrastriate areas. The effects of word frequency on closed-class words were also investigated. For these purposes, open- and closed-class words, among other stimuli, were presented by means of the rapid stream stimulation procedure. Results showed that there were no significant differences when comparing the RP evoked by open- and closed-class words in the left hemisphere. However, in the right hemisphere this situation changed: the RP evoked by open- and closed-class words did differ. Moreover, there were no differences between the RP evoked by closed-class words and pseudowords. These patterns of results suggest that the semantic processing of closed-class words shares some aspects with the processing of open-class words, despite the existence of some differences. Thus, whereas the semantic processing of open-class words recruits brain areas of both hemispheres, the semantic processing of closed-class words is left-lateralized. A second purpose of this work is to study word-frequency effects on closed-class words. Our results show the insensitivity of closed-class words to word-frequency effects.

An ERP study on the specificity of facial expression processing.

Facial expression processing specificity was investigated by means of event-related potentials (ERPs). Stimuli consisted on happiness facial expressions (H) along with three other visual stimuli with different physical and affective characteristics: neutral facial expressions, landscapes and grey slides. The 32 subjects had to rate the stimuli with respect to two affective dimensions: 'valence' and 'arousal'. EEG was recorded at T7, T8, Fz and Cz, and the epoch was of 1000 ms (100 ms prior to stimulus onset). Analyses revealed that the variability of N200 and P200 components, which were not able to detect a differential activity in response to H stimuli, could be explained in terms of physical complexity and relevance of the stimuli. N300 did detect a differentiation between H and the rest of stimuli, sharing some characteristics of previous and later components. With respect to late components, P300 seemed to reflect the trends of 'arousal' ratings and SW results suggest that its amplitude was influenced by the stimulus recognition effort. Not a clear right or left hemisphere advantage in facial expression processing was found. These ERP results suggest that the specificity of facial expression processing is not strictly circumscribed to a particular latency or to a specific neural area, but it resides in a particular combination of discrete processes.

Emotion, attention, and the 'negativity bias', studied through event-related potentials.

Behavioral studies indicate that there exists a 'negativity bias' in the way surrounding events are processed. Particularly, it has been indicated that negative events elicit more rapid and more prominent responses than non-negative events. The objective of the present study was to explore the role of attention in relation to this negativity bias. Three groups of emotional pictures were used as stimuli: positive, negative and neutral. Event-related potentials were recorded from 35 subjects at F5, Fz, F6, C5, Cz, C6, P5, Pz and P6. Valence and arousal content of the stimulation was measured via a questionnaire. The experimental design ensured that subjects whose data were finally analyzed attended to the stimuli. ANOVAs showed that P200, an attention-related component, showed higher amplitudes and shorter latencies in response to negative stimuli than in response to positive stimuli. Additional partial correlation analyses indicated that P200 amplitude, but not latency, significantly associates (at frontal and central sites) with valence content of the stimulation. Therefore, due to the valence-related nature of the bias, it is concluded that intensity aspects (more than timing aspects) of the P200-related attentional processes are particularly involved in the negativity bias.

[Human brain activity in response to emotional visual stimuli: open issues and recent data]. / Actividad cerebral humana en respuesta a estímulos visuales emocionales: debates abiertos y datos recientes.

INTRODUCTION: The traditional circumplex model on the structure of emotion postulates that this process is organized in two basic dimensions: valence (positive negative) and activation (relaxing activating). This model assumes that the valence activates a single evaluative system. With regard to cerebral activity, two ideas are derived from this assumption: 1) a single set of mechanisms and neural circuits becomes activated in response to both positive and negative events, 2) the faculty of response to adverse and pleasant responses (i.e., latency and intensity with which the neural structures involved can respond) is potentially balanced. DEVELOPMENT: We describe the debates on these two issues and, subsequently, the current data regarding them are also described. These data indicate that, in response to aversive stimuli (often noxious), neural systems characterized by their ability to produce an immediate response are preferentially activated. On the other hand, pleasant stimuli (which lead to an approaching behavior towards the stimulus) preferentially activate systems associated with more intense and precise information processing. This is a slower but longer lasting type of activity. CONCLUSION: The data suggest that there are separate mechanisms for the evaluation and preparation of a response according to whether the stimulus is negative or positive.

Decomposing unpleasantness: differential exogenous attention to disgusting and fearful stimuli.

Negative stimuli have consistently been shown to efficiently attract exogenous attention. Two different types of unpleasant stimuli, disgusting and fearful, sharing similar arousal and valence, are usually employed as a single category. However, since they diverge in several important aspects (biological functionality, associated feelings, and central and peripheral physiological correlates), it may be expected that their potential to capture attention differs. Event-related potentials and behavioral indices were recorded while participants were engaged in a digit categorization task in response to three types of irrelevant, distracting pictures: disgusting, fearful and neutral. Disgusting trials were associated with worse performance than fearful trials in the digit categorization task as revealed by reaction times and number of errors. Moreover, P2-associated cuneus activation and scalp anterior P2 amplitude were greater for disgusting than for fearful distracters. All these indices reveal that, under the experimental conditions employed in the present study, disgusting distracters are more efficient at attracting exogenous attention than are fearful distracters.

The striatum beyond reward: caudate responds intensely to unpleasant pictures.

The involvement of striatum in affective processes has been consistently reported in recent years. However, studies within this field have mainly focused on positive affect, revealing the involvement of striatum in reward situations. The present research aimed to explore the involvement of striatum in negative affect through fMRI. To that aim, participants (n=18) were presented with negative, positive and neutral pictures while they performed an indirect task, a strategy repeatedly recommended to avoid cognitive interferences. Positive and negative stimuli did not differ in their arousal levels, as assessed by participants themselves. Analyses of variance showed that caudate nucleus was sensitive to the emotional content of stimulation, negative pictures eliciting greater caudate responses than positive and neutral. Regression analyses indicated that both valence and arousal content of visual stimuli synergically contributed to explain the activation of caudate, whose strong response to negative pictures supports models proposing striatum as a key element in withdrawal situations.

[Emotional alterations in attention deficit hyperactivity disorder: existing data and open questions]. / Alteraciones emocionales en el trastorno por déficit deatención/hiperactividad: datos existentes y cuestiones abiertas.

INTRODUCTION: Research on attention deficit hyperactivity disorder (ADHD) has focused mainly on cognitive aspects, leaving in the background the study of the affective deficiencies accompanying the disorder. AIMS: To review the research on emotional competence of children, teenagers and adults with ADHD (recognition, regulation, and expression of emotions), and identify which issues have been scarcely studied yet and require further attention. DEVELOPMENT: Convergent data from different behavioral studies indicate that children as well as adults with ADHD show a primary dysfunction in the recognition of emotional stimuli (facial expression and affective prosody), and an important disability to modulate their emotions, specially the negative ones. Nevertheless, the existing knowledge concerning the emotional dysfunctions in ADHD is limited, and several open questions, most of them concerning the neural basis underlying these dysfunctions, still remain. CONCLUSIONS: The present review highlights the need to develop new research in the study of emotional dysfunctions in ADHD using not only behavioral measures, but also cerebral activity measures, and to assess and treat emotional problems in the clinical practice.

A study on the emotional-processing of visual stimuli through event-related potentials.

The effect of emotional charge of visual stimuli on cerebral activity was investigated through ERPs. This emotional charge is explained through two dimensions: arousal (relaxing-activating) and valence (attractive-repulsive). Stimuli were 12 paintings selected through questionnaires: three activating-attractive pictures (A+ group), three activating-repulsive (A-), three relaxing (R), and three neutral (N). The ERPs were recorded from the 31 subjects at F3, Fz, F4, C3, Cz, C4, P3, Pz and P4. N200 and P300 did not show significant reactions to the emotional charge of the stimuli. N300 showed greater amplitudes in response to activating stimuli: at frontal sites for A+ and at parietal sites for A-.

N300, P300 and the emotional processing of visual stimuli.

Two components of the ERPs elicited by emotional visual stimuli, N300 and P300, were investigated. The emotional charge is explained through two dimensions: arousal (relaxing (R) or activating (A)) and valence (attractive (+) or repulsive (-)). Stimuli were slides of nudes (A+), human remains (A-), landscapes (R), and buildings (neutral (N)). The peculiar structure of the stimuli, along with a distracting task which allowed us to disguise the real aim of the experiment, helped to avoid a sort of 'relevance-for-task effect', mainly related to cognitive processes, which could explain P300 reactions in response to emotional visual stimuli found in several experiments. The ERPs were recorded from 32 subjects at F3, Fz, F4, C3, Cz, C4, P3, Pz and P4. In contrast to previous studies, P300 did not show greater amplitudes in response to emotional stimuli than to N. N300 showed greater amplitudes in response to A+ at parietal sites, the greatest differences being those with respect to A-. No inter-hemispheric differences were found. N300 confirms its usefulness as a variable for studying emotional reactions to visual stimuli.

Emotion and attention interaction studied through event-related potentials.

Several studies on hemodynamic brain activity indicate that emotional visual stimuli elicit greater activation than neutral stimuli in attention-related areas such as the anterior cingulate cortex (ACC) and the visual association cortex (VAC). In order to explore the temporo-spatial characteristics of the interaction between attention and emotion, two processes characterized by involving short and rapid phases, event-related potentials (ERPs) were measured in 29 subjects using a 60-electrode array and the LORETA source localization software. A cue/target paradigm was employed in order to investigate both expectancy-related and input processing-related attention. Four categories of stimuli were presented to subjects: positive arousing, negative arousing, relaxing, and neutral. Three attention-related components were finally analyzed: N280pre (from pretarget ERPs), P200post and P340post (both from posttarget ERPs). N280pre had a prefrontal focus (ACC and/or medial prefrontal cortex) and presented significantly lower amplitudes in response to cues announcing negative targets. This result suggests a greater capacity of nonaversive stimuli to generate expectancy-related attention. P200post and P340post were both elicited in the VAC, and showed their highest amplitudes in response to negative- and to positive-arousing stimuli, respectively. The origin of P200post appears to be located dorsally with respect to the clear ventral-stream origin of P340post. The conjunction of temporal and spatial characteristics of P200post and P340post leads to the deduction that input processing-related attention associated with emotional visual stimulation involves an initial, rapid, and brief "early" attentional response oriented to rapid motor action, being more prominent towards negative stimulation. This is followed by a slower but longer "late" attentional response oriented to deeper processing, elicited to a greater extent by appetitive stimulation.