Electrophysiological evidence for increased auditory crossmodal activity in adult ADHD.

Background: Attention deficit and hyperactivity disorder (ADHD) is a neurodevelopmental disorder characterized by core symptoms of inattention, and/or impulsivity and hyperactivity. In order to understand the basis for this multifaceted disorder, the investigation of sensory processing aberrancies recently reaches more interest. For example, during the processing of auditory stimuli comparable low sensory thresholds account for symptoms like higher distractibility and auditory hypersensitivity in patients with ADHD. It has further been shown that deficiencies not only exist on an intramodal, but also on a multimodal level. There is evidence that the visual cortex shows more activation during a focused auditory task in adults with ADHD than in healthy controls. This crossmodal activation is interpreted as the reallocation of more attentional resources to the visual domain as well as deficient sensory inhibition. In this study, we used, for the first time, electroencephalography to identify a potential abnormal regulated crossmodal activation in adult ADHD. Methods: 15 adult subjects with clinically diagnosed ADHD and 14 healthy controls comparable in age and gender were included. ERP components P50, P100, N100, P200 and N200 were measured during the performance of a unimodal auditory and visual discrimination task in a block design. Sensory profiles and ADHD symptoms were assessed with inattention as well as childhood ADHD scores. For evaluating intramodal and crossmodal activations, we chose four EEG channels for statistical analysis and group-wise comparison. Results: At the occipital channel O2 that reflects possible crossmodal activations, a significantly enhanced P200 amplitude was measured in the patient group. At the intramodal channels, a significantly enhanced N200 amplitude was observed in the control group. Statistical analysis of behavioral data showed poorer performance of subjects with ADHD as well as higher discrimination thresholds. Further, the correlation of the assessed sensory profiles with the EEG parameters revealed a negative correlation between the P200 component and sensation seeking behavior. Conclusion: Our findings show increased auditory crossmodal activity that might reflect an altered stimulus processing resource allocation in ADHD. This might induce consequences for later, higher order attentional deployment. Further, the enhanced P200 amplitude might reflect more sensory registration and therefore deficient inhibition mechanisms in adults with ADHD.

Studying trait-characteristics and neural correlates of the emotional ego- and altercentric bias using an audiovisual paradigm.

In social interactions, emotional biases can arise when the emotional state of oneself and another person are incongruent. A person's ability to judge the other's emotional state can then be biased by their own emotional state, leading to an emotional egocentric bias (EEB). Alternatively, a person's perception of their own emotional state can be biased by the other's emotional state leading to an emotional altercentric bias (EAB). Using a modified audiovisual paradigm, we examined in three studies (n = 171; two online & one lab-based study) whether emotional biases can be considered traits by measuring two timepoints within participant and relating empathy trait scores to emotional biases, as well as the electrophysiological correlates of emotional biases. In all studies, we found a congruency effect, reflecting an EEB and EAB of small size. Both biases failed to correlate significantly within participants across timepoints and did not display significant relationships with empathy trait scores. On the electrophysiological level, we did not find any neural emotional bias effects in the time-frequency domain. Our results suggest that EEB and EAB effects are strongly task sensitive. Caution is warranted when studying interindividual differences in emotional biases using this paradigm, as they did not show significant test-retest reliabilities.

Social Context and Rejection Expectations Modulate Neural and Behavioral Responses to Social Feedback.

When meeting other people, some are optimistic and expect to be accepted by others, whereas others are pessimistic and expect mostly rejections. How social feedback is evaluated in situations that meet or do not meet these biases and how people differ in their response to rejection and acceptance depending on the social situation are unknown. In this study, participants experienced rejection and acceptance by peers in two different social contexts, one with high (negative context) and the other with low probability of rejection (positive context). We examined how the neural and behavioral responses to rejection are altered by this context and whether it depends on the individual's sensitivity to rejection. Behavioral results show that, on average, people maintain an optimistic bias even when mostly experiencing rejection. Importantly, personality differences in rejection sensitivity affected both prior expectations to be rejected in the paradigm and the extent to which expectations changed during the paradigm. The context also strongly modulated ERPs and theta responses to rejection and acceptance feedback. Specifically, valence effects on neural responses were enhanced in the negative context, suggesting a greater relevance to monitor social feedback in such a situation. Moreover, midfrontal theta predicted how expectations were changed in response to prediction errors, stressing a role for theta in learning from social feedback. Surprisingly, interindividual differences in rejection sensitivity did not affect neural responses to feedback. Our results stress the importance of considering the interaction between subjective expectations and the social context for behavioral and neural responses to social rejection.

An approach to social flexibility: Congruency effects during spontaneous word-by-word interaction.

Cognitive flexibility is the ability to switch between different concepts or to adapt goal-directed behavior in a changing environment. Although, cognitive research on this ability has long been focused on the individual mind, it is becoming increasingly clear that cognitive flexibility plays a central role in our social life. This is particularly evident in turn-taking in verbal conversation, where cognitive flexibility of the individual becomes part of social flexibility in the dyadic interaction. In this work, we introduce a model that reveals different parameters that explain how people flexibly handle unexpected events in verbal conversation. In order to study hypotheses derived from the model, we use a novel experimental approach in which thirty pairs of participants engaged in a word-by-word interaction by taking turns in generating sentences word by word. Similar to well established individual cognitive tasks, participants needed to adapt their behavior in order to respond to their co-actor's last utterance. With our experimental approach we could manipulate the interaction between participants: Either both participants had to construct a sentence with a common target word (congruent condition) or with distinct target words (incongruent condition). We further studied the relation between the interactive Word-by-Word task measures and classical individual-centered, cognitive tasks, namely the Number-Letter task, the Stop-Signal task, and the GoNogo task. In the Word-by-Word task, we found that participants had faster response times in congruent compared to incongruent trials, which replicates the primary findings of standard cognitive tasks measuring cognitive flexibility. Further, we found a significant correlation between the performance in the Word-by-Word task and the Stop-Signal task indicating that participants with a high cognitive flexibility in the Word-by-Word task also showed high inhibition control.

Expectancy effects in the EEG during joint and spontaneous word-by-word sentence production in German.

Our aim in the present study is to measure neural correlates during spontaneous interactive sentence production. We present a novel approach using the word-by-word technique from improvisational theatre, in which two speakers jointly produce one sentence. This paradigm allows the assessment of behavioural aspects, such as turn-times, and electrophysiological responses, such as event-related-potentials (ERPs). Twenty-five participants constructed a cued but spontaneous four-word German sentence together with a confederate, taking turns for each word of the sentence. In 30% of the trials, the confederate uttered an unexpected gender-marked article. To complete the sentence in a meaningful way, the participant had to detect the violation and retrieve and utter a new fitting response. We found significant increases in response times after unexpected words and - despite allowing unscripted language production and naturally varying speech material - successfully detected significant N400 and P600 ERP effects for the unexpected word. The N400 EEG activity further significantly predicted the response time of the subsequent turn. Our results show that combining behavioural and neuroscientific measures of verbal interactions while retaining sufficient experimental control is possible, and that this combination provides promising insights into the mechanisms of spontaneous spoken dialogue.

Studying brain activity during word-by-word interactions using wireless EEG.

We introduce here the word-by-word paradigm, a dynamic setting, in which two people take turns in producing a single sentence. This task requires a high degree of coordination between the partners and the simplicity of the task allows us to study with sufficient experimental control behavioral and neural processes that underlie this controlled interaction. For this study, 13 pairs of individuals engaged in a scripted word-by-word interaction, while we recorded the neural activity of both participants simultaneously using wireless EEG. To study expectation building, different semantic contexts were primed for each participant. Semantically unexpected continuations were introduced in 25% of all sentences. In line with the hypothesis, we observed amplitude differences for the P200-N400-P600 ERPs for unexpected compared to expected words. Moreover, we could successfully assess speech and reaction times. Our results show that it is possible to measure ERPs and RTs to semantically unexpected words in a dyadic interactive scenario.

Corrigendum: The N400 Effect during Speaker-Switch-Towards a Conversational Approach of Measuring Neural Correlates of Language.

[This corrects the article on p. 1854 in vol. 7, PMID: 27965604.].

The N400 Effect during Speaker-Switch-Towards a Conversational Approach of Measuring Neural Correlates of Language.

Language occurs naturally in conversations. However, the study of the neural underpinnings of language has mainly taken place in single individuals using controlled language material. The interactive elements of a conversation (e.g., turn-taking) are often not part of neurolinguistic setups. The prime reason is the difficulty to combine open unrestricted conversations with the requirements of neuroimaging. It is necessary to find a trade-off between the naturalness of a conversation and the restrictions imposed by neuroscientific methods to allow for ecologically more valid studies. Here, we make an attempt to study the effects of a conversational element, namely turn-taking, on linguistic neural correlates, specifically the N400 effect. We focus on the physiological aspect of turn-taking, the speaker-switch, and its effect on the detectability of the N400 effect. The N400 event-related potential reflects expectation violations in a semantic context; the N400 effect describes the difference of the N400 amplitude between semantically expected and unexpected items. Sentences with semantically congruent and incongruent final words were presented in two turn-taking modes: (1) reading aloud first part of the sentence and listening to speaker-switch for the final word, and (2) listening to first part of the sentence and speaker-switch for the final word. A significant N400 effect was found for both turn-taking modes, which was not influenced by the mode itself. However, the mode significantly affected the P200, which was increased for the reading aloud mode compared to the listening mode. Our results show that an N400 effect can be detected during a speaker-switch. Speech articulation (reading aloud) before the analyzed sentence fragment did also not impede the N400 effect detection for the final word. The speaker-switch, however, seems to influence earlier components of the electroencephalogram, related to processing of salient stimuli. We conclude that the N400 can effectively be used to study neural correlates of language in conversational approaches including speaker-switches.