Distortions and disconnections: disrupted brain connectivity in autism

The past few years have seen considerable interest in findings of abnormal brain connectivity in the autism spectrum disorders (ASD). We review recent work from neuroimaging and other sources, and argue that there is considerable convergent evidence suggesting that connectivity is disrupted in ASD. We point to evidence both of local over-connectivity and of long-distance under-connectivity, and describe some non-uniformities in this picture, most notably that disruptions appear more severe in later-developing cortical regions. We conclude by discussing a number of extant questions. Firstly, we consider whether aberrant connectivity should be seen as part of the primary pathogenesis of autism, or whether disrupted connectivity in ASD emerges over time. Secondly, we consider how the patterns of disrupted connectivity found in ASD might relate to those being found in a range of other disorders.     

Mechanisms of developmental regression in autism and the broader phenotype: a neural network modeling approach

Loss of previously established behaviors in early childhood constitutes a markedly atypical developmental trajectory. It is found almost uniquely in autism and its cause is currently unknown (Baird et al., 2008). We present an artificial neural network model of developmental regression, exploring the hypothesis that regression is caused by overaggressive synaptic pruning and identifying the mechanisms involved. We used a novel population-modeling technique to investigate developmental deficits, in which both neurocomputational parameters and the learning environment were varied across a large number of simulated individuals. Regression was generated by the atypical setting of a single pruning-related parameter. We observed a probabilistic relationship between the atypical pruning parameter and the presence of regression, as well as variability in the onset, severity, behavioral specificity, and recovery from regression. Other neurocomputational parameters that varied across the population modulated the risk that an individual would show regression. We considered a further hypothesis that behavioral regression may index an underlying anomaly characterizing the broader autism phenotype. If this is the case, we show how the model also accounts for several additional findings: shared gene variants between autism and language impairment (Vernes et al., 2008); larger brain size in autism but only in early development (Redcay & Courchesne, 2005); and the possibility of quasi-autism, caused by extreme environmental deprivation (Rutter et al., 1999). We make a novel prediction that the earliest developmental symptoms in the emergence of autism should be sensory and motor rather than social and review empirical data offering preliminary support for this prediction.     

Intelligence and neural efficiency: Measures of brain activation versus measures of functional connectivity in the brain

The neural efficiency hypothesis of intelligence suggests a more efficient use of the cortex (or even the brain) in brighter as compared to less intelligent individuals. This has been shown in a series of studies employing different neurophysiological measurement methods and a broad range of different cognitive task demands. However, most of the studies dealing with the brain–IQ relationship used parameters of absolute or relative brain activation such as the event-related (de-)synchronization of EEG alpha activity, allowing for interpretations in terms of more or less brain activation when individuals are confronted with cognitively demanding tasks. In order to investigate the neural efficiency hypothesis more thoroughly, we also used measures that inform us about functional connectivity between different brain areas (or functional coupling, respectively) when engaged in cognitive task performance. Analyses reveal evidence that higher intelligence is associated with a lower brain activation (or a lower ERD, respectively) and a stronger phase locking between short-distant regions of the frontal cortex.     

Identifying environmental contributions to autism: provocative clues and false leads

The potential role of environmental factors in autism spectrum disorders (ASD) is an area of emerging interest within the public and scientific communities. The high degree of heritability of ASD suggests that environmental influences are likely to operate through their interaction with genetic susceptibility during vulnerable periods of development. Evaluation of the plausibility of specific neurotoxicants as etiological agents in ASD should be guided by toxicological principles, including dose-effect dependency and pharmacokinetic parameters. Clinical and epidemiological investigations require the use of sufficiently powered study designs with appropriate control groups and unbiased case ascertainment and exposure assessment. Although much of the existing data that have been used to implicate environmental agents in ASD are limited by methodological shortcomings, a number of efforts are underway that will allow more rigorous evaluation of the role of environmental exposures in the etiology and/or phenotypic expression of the disorder. Surveillance systems are now in place that will provide reliable prevalence estimates going forward in time. Anticipated discoveries in genetics, brain pathology, and the molecular/cellular basis of functional impairment in ASD are likely to provide new opportunities to explore environmental aspects of this disorder.     

Unemployment and civil commitment: a test of the intolerance hypothesis

We theorize that the reported association between economic indicators and the incidence of civil commitment for mental illness may result, at least in part, from reduced tolerance in the community for impaired behavior among minorities. Earlier work suggests that economically induced intolerance will be focused primarily on minority males. Based on this literature, we hypothesize that the median level of functioning among African-American males subjected to civil commitment will vary positively with earlier changes in the unemployment rate. The test applies Box-Jenkins methods to 156 months (August 1985-July 1998) of data from California. Consistent with theory, results support the hypothesis.     

Lightness constancy: a direct test of the illumination-estimation hypothesis

Many models of color constancy assume that the visual system estimates the scene illuminant and uses this estimate to determine an object's color appearance. A version of this illumination-estimation hypothesis, in which the illuminant estimate is associated with the explicitly perceived illuminant, was tested. Observers made appearance matches between two experimental chambers. Observers adjusted the illumination in one chamber to match that in the other and then adjusted a test patch in one chamber to match the surface lightness of a patch in the other. The illumination-estimation hypothesis, as formulated here, predicted that after both matches the luminances of the light reflected from the test patches would be identical. The data contradict this prediction. A second experiment showed that manipulating the immediate surround of a test patch can affect perceived lightness without affecting perceived illumination. This finding also falsifies the illumination-estimation hypothesis.     

Reduced-frequency concurrent and terminal feedback: a test of the guidance hypothesis

In 2 experiments, the authors manipulated the frequency of concurrent feedback to discern the effects on learning. In each experiment, participants (N = 48, Experiment 1; N = 36, Experiment 2) attempted to reproduce a criterion force-production waveform (5 s in duration) presented on the computer monitor. Consistent with the guidance hypothesis, the results of Experiment 1 indicated very strong guiding effects of concurrent feedback and strong dependence on the feedback, as indicated by participants' extremely poor performance upon feedback withdrawal in retention. As predicted by the guidance hypothesis, dependence on the feedback was reduced as a result of reducing the frequency of the concurrent feedback. The results of Experiment 2 indicated that one can enhance learning by providing concurrent and terminal feedback on 1 trial, with no feedback on the subsequent trial. In that way, the strong guiding effects of concurrent feedback could be realized and the beneficial effects of terminal feedback could also be achieved.     

An experimental test of a core REBT hypothesis: evidence that irrational beliefs lead to physiological as well as psychological arousal

While numerous studies support Rational Emotive Behavior Therapy and Theory (REBT), they tend to be limited by their use of correlational designs, simulated scenarios and self-report measures. This study tested a core REBT hypothesis in an experimental design using multiple physiological as well as psychological measures. Ninety patients from a medical practice were placed in a real-life stressful situation while holding either a rational, an irrational, or an indifference belief. Those holding a rational belief reported the greatest increase in concern whereas those holding an irrational belief reported the greatest increase in anxiety. Of particular significance, those holding a rational belief showed a decrease in systolic blood pressure whereas those holding an irrational belief showed an increase (diastolic blood pressure increased in both conditions). These results not only support the core REBT hypothesis, but also suggest a way to differentiate between beliefs and emotions by measuring physiological as well as psychological changes.     

Children's perceptual organization of seriated displays: evidence against a memory reorganization hypothesis.

The memory for a seriated display and its reorganization over an eight-month interval was examined in educationally subnormal children. By including groups of children who viewed a random display and an array of disordered sticks, it was found that the reorganization into a more seriated drawing after the passage of time was not directly based on the original stimulus. Various controls including copying of the original material, and matching and recognition conditions, give evidence that the child's cognitive level affects encoding of the material as well as its later output. The observed phenomenon of 'memory' improvement may have little to do with stored images, and may instead be linked to the developmental symbolic level of the child which influences original perception as well as 'memory'. It was also found that educationally subnormal children perform like normal children of the same mental age on the seriation task.     

Passion and psychological adjustment: a test of the person-environment fit hypothesis

Passion represents a strong inclination toward an activity that is important, liked, and in which significant time is invested. Although a harmonious passion is well integrated in one's identity and is emitted willingly, obsessive passion is not well integrated and is emitted out of internal pressure. This study tested for the presence of a Passion x Environment fit interaction with respect to psychological adjustment. Elite hockey players (N = 233) who tried out for a team in a highly competitive league participated in this short-term longitudinal study. As hypothesized, being selected by the highly competitive leagues led to higher psychological adjustment than not being selected by such leagues. Two months later, an interaction revealed that among athletes who were playing in highly competitive leagues, obsessively passionate athletes reported higher psychological adjustment than did harmonious athletes. Conversely, among athletes playing in less competitive leagues, harmonious athletes reported higher psychological adjustment than did obsessive athletes.     

Emotional arousal and memory: a test of the poststimulus processing hypothesis

Emotional arousal is believed to enhance memory for details central to an episode but impair memory for peripheral details. However, new research suggests that arousal induced thematically (i.e., through involvement with an unfolding event) produces only memory enhancements. This article examines whether consciously controlled elaborative processing in the aftermath of an arousing experience is responsible. A dual task manipulation was used to prevent participants from ruminating over a video that depicted an abduction and attack. Several indices of recall showed greater memory for emotional event details than for details from a neutral control video, which remained the case when the opportunity for post-stimulus elaboration was prevented. Thus, superior retention of the content of emotional experiences may arise from the way in which arousal is induced rather than through immediate postevent cognitions.     

Comparison of neural activity that leads to true memories,false memories,and forgetting: An fMRI study of the misinformation effect

False memories can occur when people are exposed to misinformation about a past event. Of interest here are the neural mechanisms of this type of memory failure. In the present study, participants viewed photographic vignettes of common activities during an original event phase (OEP), while we monitored their brain activity using fMRI. Later, in a misinformation phase, participants viewed sentences describing the studied photographs, some of which contained information conflicting with that depicted in the photographs. One day later, participants returned for a surprise item memory recognition test for the content of the photographs. Results showed reliable creation of false memories, in that participants reported information that had been presented in the verbal misinformation but not in the photographs. Several regions were more active during the OEP for later accurate memory than for forgetting, but they were also more active for later false memories, indicating that false memories in this paradigm are not simply caused by failure to encode the original event. There was greater activation in the ventral visual stream for subsequent true memories than for subsequent false memories, however, suggesting that differences in encoding may contribute to later susceptibility to misinformation.     

Left-side infant holding: a test of the hemispheric arousal-attentional hypothesis

When asked to hold a young infant in their arms, most adults hold on the left side (Harris, 1997). In a prior study, we found the same bias when we asked adults merely to imagine holding an infant in their arms (Harris, Almerigi, & Kirsch, 1999). It has been hypothesized that the left-side bias is the product of right-hemisphere arousal accompanying certain aspects of the act, causing attention to be driven to the contralateral, or left, side of personal space. Left-side holding, whether actual or imagined, thus would be consistent with the direction to which the holder's attention has been endogenously directed. We tested this hypothesis by giving 250 college students the "imagine-holding" task and then, as an independent measure of lateralized hemispheric arousal, a 34-item Chimeric Faces Test (CFT). On the "imagine" test, a significant majority reported a left-side hold, and, on the CFT, left-side holders had a significantly stronger left-hemispace bias than right-side holders, although both left- and right side holders had left-hemispace CFT biases. The results thus support the attentional-arousal hypothesis but indicate that other factors are contributing as well.