Comparing different EEG connectivity methods in young males with ASD
Although EEG connectivity data are often used to build models of the association between overt behavioural signs of Autism Spectrum Disorder (ASD) and underlying brain connectivity indices, use of a large number of possible connectivity methods across studies has produced a fairly inconsistent set of results regarding this association. To explore the level of agreement between results from five commonly-used EEG connectivity models (i.e., Coherence, Weighted Phased Lag Index- Debiased, Phase Locking Value, Phase Slope Index, Granger Causality), a sample of 41 young males with ASD provided EEG data under eyes-opened and eyes-closed conditions. There were relatively few statistically significant and/or meaningful correlations between the results obtained from the five connectivity methods, arguing for a re-estimation of the methodology used in such studies so that specific connectivity methods may be matched to particular research questions regarding the links between neural connectivity and overt behaviour within this population.
Directional alpha frontoparietal connectivity and anxiety in autistic boys
Describing neural connectivity between pre-frontal and parietal brain regions and anxiety in children and adolescents with Autism Spectrum Disorder (ASD) has the potential to inform diagnosis and treatment decisions. This study aimed to identify the neural connectivity patterns between the prefrontal cortex (PFC) and parietal regions in young autistic males, and to determine if Generalised Anxiety Disorder (GAD) was associated with these communication patterns. Forty-one males with ASD aged between 6 and 18 yr (M age= 10.76 yr, SD= 3.14 yr) and their mothers were recruited as volunteer participants from the Gold Coast region, Australia. After assessments, participants received 3 min of eyes-closed and 3 min of eyes-opened EEG data-collection under resting conditions. EEG data from the frontal and parietal regions were investigated for their connectivity via Granger Causality (GC). There were significant correlations between the PFC-to-parietal region GC connectivity indices and total GAD scores, and also for the core components of GAD, but these were restricted to the alpha-wave frequency with only minimal beta-wave significant results. No significant correlations between parietal-to-PFC regions and GAD were present. Communication from the decision-making region (PFC) to the spatial reasoning (parietal) regions appeared to be aimed at instigating increased motor activity associated with GAD.
Which kinds of work stress are related with which types of depression? Workplace satisfaction and subtypes of depression in rural Australians
Although the association between Job Satisfaction (JS) and depression has been reported at a global level, relatively little is known about that relationship in terms of specific aspects of JS and subtypes of depression. To investigate this issue, eighty-eight employed participants from rural Australia answered questionnaires about JS and depression, plus background factors such as hours worked at paid employment and at unpaid employment. Data were analysed at total JS and depression score level and also for specific JS aspects and four subtypes of depression, as well as specific depressive symptoms. There were significant correlations between participants’ dissatisfaction with the hours they worked at paid employment and global depression, and also for depressed mood and Somatic depression. Specific depressive symptoms related to hours worked included feeling downhearted and blue and having trouble sleeping at night. There was also some evidence of an interaction between participants’ dissatisfaction with hours worked and their ability to complete non-paid work responsibilities. Identification of the pathways between specific aspects of JS and particular subtypes and symptoms of depression suggests possible interventions that may be focussed upon those depression symptoms and/or differential allocation of work hours within the workplace.
A Comment on some Methodological Issues in EEG Connectivity Studies of Sensory Features in Youth with Autism
Investigation of the neurological underpinnings of the diagnostic symptoms for Autism Spectrum Disorder (ASD) represents a potential pathway towards a biomarker for this disorder. One of the key symptoms of ASD is Sensory Features (SF), which refers to the difficulties that autistic people experience with particular kinds of environmental stimuli. Studies using eeg measures of neural connectivity across various regions of the brain hold promise in identifying how the autistic brain reacts to its environment. This commentary identifies several 'participant' and 'measurement' methodological issues that need to be adequately addressed in SF-eeg connectivity studies, and applies these comments to a sample of five previous studies. Recommendations are made for future research procedures.
Sensory Features and Bi-directional EEG Connectivity in Young Autistic Males
Several lines of research suggest that autism is a neurological phenomenon, but the precise associations between neurological activity and the key diagnostic symptoms of autism are yet to be completely clarified. This study examined EEG connectivity and Sensory Features (SF) in a sample of young autistic males by examining bi-directional neural connectivity between separate brain regions as the key potential correlate of SF. Forty male autistic participants aged between 6 and 17 years, with an IQ of at least 70, underwent EEG measurements of their Frontal, Occipital and Temporal region responses to low-, medium-, and high-intensity audiovisual stimulus conditions. EEG connectivity data were analysed via Granger Causality. SF was measured via parent responses about their sons on the Child Sensory Profile (2nd ed.) (CSP-2). There were significant (p < .05) correlations between right hemisphere Frontal and Temporal connectivity and CSP-2 dominant scores, largely due to lower Temporal-to-Frontal than Frontal-to-Temporal connectivity. There were no significant correlations between general CSP-2 scores and EEG connectivity data collected during audiovisual stimuli. These results confirm and extend previous findings by adding bi-directional connectivity as an index of brain activity to other studies that used only uni-directional connectivity data when measuring SF. Although there may be a discrepancy between the kinds of information collected via instruments such as the CSP-2 and actual brain electrical connectivity across major regions, these results hold implications for the use of brain-training interventions with autistic boys.
Variation in Social Anxiety and Separation Anxiety over Age in ASD and Non-ASD Young Males: Issues for Clinical Assessment and Treatment-Planning
To further understand how young males with Autism Spectrum Disorder (ASD) experience anxiety, two specific forms of anxiety were examined in samples of boys with ASD and their non-ASD (NASD) peers. Self-reports on the Child and Adolescent Symptom Inventory (4th rev.) were collected from 117 ASD boys and 50 NASD boys, aged from 6 yr to 17 yr who were matched for IQ and age. Data regarding their Social Anxiety and Separation Anxiety were examined and indicated that the ASD boys had significantly elevated levels of both forms of anxiety compared to their NASD peers. When examined at two-yearly age intervals, the ASD boys continued to exhibit high levels of Social Anxiety over age but the NASD boys showed a gradual decrease in this form of anxiety with age. Although Separation Anxiety showed a gradual decrease with age in the ASD group, that result was different for four of the Separation Anxiety symptoms, thus identifying aspects of Separation Anxiety that may remain elevated despite decreases in some other aspects with age. These results have implications for assessment of anxiety in boys with ASD and for the development of treatment plans aimed at assisting them to function effectively.
Frontoparietal connectivity, Sensory Features, and Anxiety in Children and Adolescents with Autism Spectrum Disorder
Objectives Because atypical global neural connectivity has been documented in autistic youth, but only limited data are available regarding the association between generalized anxiety disorder (GAD), sensory features (SF), and neural connectivity between frontal and parietal brain regions, these links were investigated in a sample of male autistic children and adolescents.
Methods Forty-one autistic males aged between 6 and 18 years and their mothers were recruited as volunteer participants from Queensland, Australia. Participants underwent 3 min of eyes-closed and 3 min of eyes-opened electroencephalography (EEG) under resting conditions. EEG connectivity was investigated using Granger causality between frontal and parietal regions in alpha (8–13 Hz) and beta (13–30 Hz) bands.
Results There was a significant (p < .01) positive correlation between SF and GAD. GAD was associated with some characteristics of SF in the sample population. Additionally, there was a significant (p < .01) inverse correlation between directional frontoparietal connectivity and SF during the eyes-closed condition, specifically in relation to avoiding stimuli and sensitivity to the environment.
Conclusions Reduced frontoparietal connectivity in association with higher anxiety and SF may demonstrate reduced relaxation due to greater sensitivity to sensory input.
Using Electroencephalography to Measure the Effects of Sensory Features upon Functional and Effective Connectivity in Children and Adolescents with Autism Spectrum Disorder
Autism Spectrum Disorder (ASD) is a neurodevelopmental condition, characterised by impairments in social communication and the presence of restricted and repetitive behaviours, activities, or interests. ‘Sensory Features’ (SF) are a key symptom of ASD, and affect 90-95% of individuals with ASD, manifesting as atypical behavioural, neurological, and self-regulatory responses to sensory stimuli in the environment. Although the overt behavioural characteristics of SF in people with ASD have been extensively investigated, internal neurophysiological processes of SF in the ASD population have been minimally explored. One method of identifying these internal neurophysiological processes associated with SF is by using electroencephalography (EEG) to measure the brain’s electrical activity, and the ways that regions of the brain communicate or ‘connect’ with each other. There is a paucity of research investigating the direct relationship between SF and brain neural connectivity in children and adolescents with ASD, and this issue was made the focus of this research. Therefore, the current study aimed to investigate the relationship between SF in the ASD population and neural connectivity via (i) analyses of five different types of EEG connectivity measurements based on resting EEG data during eyes-closed and eyes-opened conditions, and (ii) analysis of Granger Causality on naturalistic audiovisual low-, medium-, and high-intensity stimulus conditions. The current study also aimed to investigate whether there was a relationship between age and Granger Causality connectivity indices in the ASD sample.
Forty-one male participants aged between 6 and 17 years, with an IQ of at least 70 and who were diagnosed with ASD took part in the current study. Connectivity analysis (using five methods: Coherence, Weighted Phase Lag Index-Debiased, Phase Locking Value, Granger Causality, and Phase Slope Index) and subsequent statistical analyses (using Pearson product moment and Spearman correlations, MANOVA, and paired samples t-tests) were conducted on EEG data from these participants.
Results indicated (i) minimal agreement between functional and effective connectivity for eyes-closed and eyes-opened conditions, (ii) significant (p < .05) deficits in connectivity between right hemisphere frontal and temporal brain regions, and a lack of significant correlations between this connectivity and Sensory Quadrant data collected on the Child Sensory Profile ( 2nded.) for audiovisual stimuli, (iii) no significant differences in connectivity between frontal and occipital regions for all resting and stimulus conditions, and (iv) no significant correlations between age and neural connectivity in frontal, temporal, and occipital regions in response to audiovisual stimuli.
The results from this research add to the current literature and provide more evidence of atypical neuronal communication, especially between frontal and temporal regions, in regards to SF in male children and adolescents with ASD. Further research using a consistent connectivity method to analyse the associations between EEG connectivity and naturalistic experimental stimuli may provide more meaningful insights and suggestions for neurophysiological interventions to reduce the adverse effects of SF in individuals with ASD.
A Brief Report on the 2.4-Year Test-Retest Agreement of Morning Cortisol and Anxiety in Boys with Autism Spectrum Disorder
Children with Autism Spectrum Disorder (ASD) also often suffer from elevated stress and anxiety. These states can be measured via reports of behaviour (from self or others) or from physiological measures of stress, including the symptoms of Generalised Anxiety Disorder (GAD) and salivary cortisol, respectively. The use of these measures assumes a degree of reliability over time so that data from a specific period may be generalised to other periods. To measure the test-retest reliability of salivary cortisol and self-ratings of GAD in 27 high-functioning boys with ASD (M age = 12.1 yr., SD = 2.8 yr), samples were collected a mean of 2.4 yr. (SD = 0.5 yr) apart and analysed to test for the presence of a significant correlation within each variable over time. Results indicated that, although the concentrations of salivary cortisol increased over the period of the study, there was a significant correlation between the two measures of cortisol. GAD scores also showed a significant correlation over the period of the study. These findings suggest that both GAD and salivary cortisol data collected from boys with ASD may be reasonably inferred to represent fairly stable phenomena over time in research and clinical settings.
Default mode network activity in depression subtypes
Depression continues to carry a major disease burden worldwide, with limitations on the success of traditional pharmacological or psychological treatments. Recent approaches have therefore focused upon the neurobiological underpinnings of depression, and on the "individualization" of depression symptom profiles. One such model of depression has divided the standard diagnostic criteria into four "depression subtypes", with neurological and behavioral pathways. At the same time, attention has been focused upon the region of the brain known as the "default mode network" (DMN) and its role in attention and problem-solving. However, to date, no review has been published of the links between the DMN and the four subtypes of depression. By searching the literature studies from the last 20 years, 62 relevant papers were identified, and their findings are described for the association they demonstrate between aspects of the DMN and the four depression subtypes. It is apparent from this review that there are potential positive clinical and therapeutic outcomes from focusing upon DMN activation and connectivity, via psychological therapies, transcranial magnetic stimulation, and some emerging pharmacological models.