Dissociable patterns of neural activity during response inhibition in depressed adolescents with and without suicidal behavior

Objectives - Impaired attentional control and behavioral control are implicated in adult suicidal behavior. Little is known about the functional integrity of neural circuitry supporting these processes in suicidal behavior in adolescence. Method - Functional magnetic resonance imaging was used in 15 adolescent suicide attempters with a history of major depressive disorder (ATTs), 15 adolescents with a history of depressive disorder but no suicide attempt (NATs), and 14 healthy controls (HCs) during the performance of a well-validated go-no-go response inhibition and motor control task that measures attentional and behavioral control and has been shown to activate prefrontal, anterior cingulate, and parietal cortical circuitries. Questionnaires assessed symptoms and standardized interviews characterized suicide attempts. Results - A 3 group by 2 condition (go-no-go response inhibition versus go motor control blocks) block-design whole-brain analysis (p < .05, corrected) showed that NATs showed greater activity than ATTs in the right anterior cingulate gyrus (p = .008), and that NATs, but not ATTs, showed significantly greater activity than HCs in the left insula (p = .004) to go-no-go response inhibition blocks. Conclusions - Although ATTs did not show differential patterns of neural activity from HCs during the go-no-go response inhibition blocks, ATTs and NATs showed differential activation of the right anterior cingulate gyrus during response inhibition. These findings indicate that suicide attempts during adolescence are not associated with abnormal activity in response inhibition neural circuitry. The differential patterns of activity in response inhibition neural circuitry in ATTs and NATs, however, suggest different neural mechanisms for suicide attempt versus major depressive disorder in general in adolescence that should be a focus of further study.

Pediatric CNS pathophysiology

Research in pediatric central nervous system pathophysiology is focused around three primary goals: identification of neurodevelopmental disorders, understanding the differences in brain development which underlie these disorders, and improving treatment for these young children. Autism spectrum disorders (ASDs) are a complex set of disorders which are characterized by difficulties in language and social interactions. These behavioral measures are highly variable and a number of underlying causes can generate similar behavioral effects. Therefore, it is important to identify neurophysiological markers to better identify and characterize these disorders. Recent ASD findings using MEG show atypical latency and amplitude responses and poor cortical connectivity in children with ASDs across the cognitive spectrum from basic auditory processing, multisensory integration, to face and semantic processing. These results further support the view that ASDs are a complex neurologically-based disorder. On the other hand, the cause of Down syndrome is well understood as originating from a partial or full replication of chromosome 21. However, the cognitive and neurological consequences of this chromosomal abnormality are not yet well understood. Using a simple observation and motor execution task, poor functional connectivity in sensory-motor areas, particularly in the gamma band range, has been identified in children with Down syndrome and is consistent with behavioral deficits in the sensory-motor realm. Additional studies are needed to better understand whether targeted identification of these abnormalities can facilitate treatment in this disorder. Finally, while epilepsy can be reliably diagnosed, seizure control is still limited in many cases where the seizure onset zone is not readily apparent. Advances in pre-surgical evaluation and intra-operative co-registration will be described. These studies describing pediatric CNS pathophysiology will be discussed. © Springer-Verlag 2010.

Group membership salience and task performance

Purpose – Social loafing is described in the literature as a frequent problem reducing individuals' performance when working in groups. This paper aims to utilize the social identity approach and proposes that under conditions of heightened group salience social loafing can be reduced and turned into social laboring (i.e. increased performance). Design/methodology/approach – Two experimental studies are conducted to examine the impact of participant's group membership salience on task performance. In Study 1, school teachers work either in coactive or in collective working conditions on brainstorming tasks. In Study 2, participants perform both a brainstorming task and a motor task. Findings – The results show social laboring effects. As predicted, participants in the high salient group conditions outperform participants in the low salient group conditions and the coactive individual condition. Practical implications – The results indicate that rather than individuating group members or tasks to overcome social loafing, managers can increase group performance by focusing on group members' perceptions of their groups as important and salient. Originality/value – The studies presented in this paper show that social identity theory and self categorization theory can fruitfully be applied to the field of group performance. The message of these studies for applied settings is that collective work in groups must not necessarily negatively impact performance, i.e. social loafing. By heightening the salience of group memberships groups can even outperform coactively working individuals.

Frontoparietal control of spatial attention and motor intention in human EEG

Relations between spatial attention and motor intention were investigated by means of an EEG potential elicited by shifting attention to a location in space as well as by the selection of a hand for responding. High-density recordings traced this potential to a common frontoparietal network activated by attentional orienting and by response selection. Within this network, parietal and frontal cortex were activated sequentially, followed by an anterior-to-posterior migration of activity culminating in the lateral occipital cortex. Based on temporal and polarity information provided by EEG, we hypothesize that the frontoparietal activation, evoked by directional information, updates a task-defined preparatory state by deselecting or inhibiting the behavioral option competing with the cued response side or the cued direction of attention. These results from human EEG demonstrate a direct EEG manifestation of the frontoparietal attention network previously identified in functional imaging. EEG reveals the time course of activation within this network and elucidates the generation and function of associated directing-attention EEG potentials. The results emphasize transient activation and a decision-related function of the frontoparietal attention network, contrasting with the sustained preparatory activation that is commonly inferred from neuroimaging.

Arms, bending discounting functions:how motor actions affect intertemporal decision-making

We demonstrate that task-irrelevant somatic activity influences intertemporal decision making: Arm movements associated with approach (arm flexion), rather than avoidance (arm extension), instigate present-biased preferences. The effect is moderated by the sensitivity of the general reward system and, owing to learning principles, restricted to arm positions of the dominant hand.

Experiments in time:exploring the components of motor timing behaviour in dyslexia

This investigation aimed to pinpoint the elements of motor timing control that are responsible for the increased variability commonly found in children with developmental dyslexia on paced or unpaced motor timing tasks (Chapter 3). Such temporal processing abilities are thought to be important for developing the appropriate phonological representations required for the development of literacy skills. Similar temporal processing difficulties arise in other developmental disorders such as Attention Deficit Hyperactivity Disorder (ADHD). Motor timing behaviour in developmental populations was examined in the context of models of typical human timing behaviour, in particular the Wing-Kristofferson model, allowing estimation of the contribution of different timing control systems, namely timekeeper and implementation systems (Chapter 2 and Methods Chapters 4 and 5). Research examining timing in populations with dyslexia and ADHD has been inconsistent in the application of stimulus parameters and so the first investigation compared motor timing behaviour across different stimulus conditions (Chapter 6). The results question the suitability of visual timing tasks which produced greater performance variability than auditory or bimodal tasks. Following an examination of the validity of the Wing-Kristofferson model (Chapter 7) the model was applied to time series data from an auditory timing task completed by children with reading difficulties and matched control groups (Chapter 8). Expected group differences in timing performance were not found, however, associations between performance and measures of literacy and attention were present. Results also indicated that measures of attention and literacy dissociated in their relationships with components of timing, with literacy ability being correlated with timekeeper variance and attentional control with implementation variance. It is proposed that these timing deficits associated with reading difficulties are attributable to central timekeeping processes and so the contribution of error correction to timing performance was also investigated (Chapter 9). Children with lower scores on measures of literacy and attention were found to have a slower or failed correction response to phase errors in timing behaviour. Results from the series of studies suggest that the motor timing difficulty in poor reading children may stem from failures in the judgement of synchrony due to greater tolerance of uncertainty in the temporal processing system.