Changes in brain activation induced by the training of hypothesis generation skills: an fMRI study

The aim of the present study is to investigate the learning-related changes in brain activation induced by the training of hypothesis generation skills regarding biological phenomena. Eighteen undergraduate participants were scanned twice with functional magnetic resonance imaging (fMRI) before and after training over a period of 2 months. The experimental group underwent eight biological hypothesis generation training programs, but the control group was not given any during the 2-month period. The results showed that the left frontal gyri, the cingulate gyrus, and the cuneus were activated during hypothesis generation. In addition, the brain activation of the trained group increased in the left inferior and the superior frontal gyri, which are related to working memory load and higher-order inferential processes. However, the activation after training decreased in the occipito-parietal route, which is associated with the perception and the analysis processes of visual information. Furthermore, the results have suggested that the dorsolateral prefrontal cortex (DLPFC) region is the critical area in the training of hypothesis generation skills.     

Deficits in executed and imagined aiming performance in brain-injured children

Motor disorders are a frequent consequence of acquired brain injury (ABI) in children and much effort is currently invested in alleviating these deficits. The aim of the present study was to test motor imagery (MI) capabilities in children with ABI (n=25) and an age- and gender-matched control group (n=25). A computerized Virtual Radial Fitts Task (VRFT) was used to investigate the speed-accuracy trade-offs (or Fitts' law) that occur as target size is varied for both executed and imagined performance. In the control group, the speed for accuracy trade-off for both executed and imagined performance conformed to Fitts' law. In the ABI group, only executed movements conformed to Fitts' law. These findings suggest that children with ABI show an inferior ability to imagine the time needed to complete goal-directed movements with differential difficulty levels.     

Relationship between psychological stress and lymphocytic 5′-ectonucleotidase

The relationship between psychological stress and lymphocytic 5-ectonucleotidase, an enzyme marker for lymphocyte differentiation, was studied. Lymphocytic 5-ectonucleotidase was decreased significantly by about twofold in persons experiencing psychological stress, with a corresponding change in Total Mood Disturbance scores of the Profile of Mood States. Enzyme values were reversible in that they returned to normal once the stress had been reduced. Administration of high doses of ascorbate to severely depressed patients also normalized 5-ectonucleotidase activities, and implied that low enzyme values in stressed persons may be mediated by oxygen radical damage. This finding was consistent with previous reports of heightened inflammatory responses occurring in depressed patients. The primary cause of lowered 5-ectonucleotidase during stress may be the breakdown in the homeostatic mechanisms of the hypothalamic-pituitary-adrenal axis and immune system resulting in lymphoid tissue resistance to corticosteroids. It is suggested that this lowering of lymphocyte 5-ectonucleotidase may contribute to stress-mediated immune suppression by inhibiting lymphocyte maturation.     

The effect of context during word perception in schizophrenic patients

Hospitalized chronic and acute schizophrenics were compared with age- and social-status-matched controls on word perception tests to measure the effect of context on recognition thresholds. In Experiment 1 the method of J. Morton (1964, British Journal of Psychology, 55, 165-180) was adopted to see how related and unrelated contexts influenced word recognition thresholds when both context and stimulus word were presented visually. Experiment 2 was an auditory analog of Experiment 1 and in addition the chronic schizophrenics were selected on the basis of a presence or absence of auditory hallucinations. The influence of context on perceptual thresholds was quite normal in all schizophrenics. However, analysis of the incorrect responses elicited showed that some schizophrenic subjects do produce bizarre or irrelevant responses or perseveration to a greater extent than their controls. These results are explained in terms of automatic and strategic modes of information processing. The automatic processes responsible for the adjustment of perceptual thresholds operate normally in schizophrenics but response production which demands strategic selection and editing of responses is prone to malfunction which results in the observed deviations in the normal use of language.     

Do complex models increase prediction of complex behaviours? Predicting driving ability in people with brain disorders

Prediction of complex behavioural tasks via relatively simple modelling techniques, such as logistic regression and discriminant analysis, often has limited success. We hypothesized that to more accurately model complex behaviour, more complex models, such as kernel-based methods, would be needed. To test this hypothesis, we assessed the value of six modelling approaches for predicting driving ability based on performance on computerized sensory–motor and cognitive tests (SMCTests?) in 501 people with brain disorders. The models included three models previously used to predict driving ability (discriminant analysis, DA; binary logistic regression, BLR; and nonlinear causal resource analysis, NCRA) and three kernel methods (support vector machine, SVM; product kernel density, PK; and kernel product density, KP). At the classification level, two kernel methods were substantially more accurate at classifying on-road pass or fail (SVM 99.6%, PK 99.8%) than the other models (DA 76%, BLR 78%, NCRA 74%, KP 81%). However, accuracy decreased substantially for all of the kernel models when cross-validation techniques were used to estimate prediction of on-road pass or fail in an independent referral group (SVM 73–76%, PK 72–73%, KP 71–72%) but decreased only slightly for DA (74–75%) and BLR (75–76%). Cross-validation of NCRA was not possible. In conclusion, while kernel-based models are successful at modelling complex data at a classification level, this is likely to be due to overfitting of the data, which does not lead to an improvement in accuracy in independent data over and above the accuracy of other less complex modelling techniques.     

Thought sequences

Abstract

Thought sequences are ordered series of verbal-like expressions that pass spontaneously through one's mind and which are characterised by well-demarcated beginnings and ends. The present paper notes the significance of and interest in thought sequences and presents a framework for their analysis. Given the scope of the enterprise, different levels of analysis are noted which set the boundaries for the present investigation, and define guidelines for further research. Here, the focus of interest is the structural (as distinct from either functional or computational) relationships between pairs of consecutive expressions. The informational bases for these relationships are reviewed and a typology of them is drawn. The typology reveals marked internal structure and it suggests that the variety of couplings of thought sequences constitutes a space spanned by a small number of variables. Methodological issues regarding the use of introspection in cognitive research are also discussed.     

Comprehensive driving assessment: neuropsychological testing and on-road evaluation of brain injured patients

The study investigates the correspondence between neuropsychological test results and on-road driving performance among 55 patients with a CT-verified brain damage or documented neurological disorder (cerebrovascular accident: 43, traumatic brain injury: 5, multiple sclerosis: 4, other: 3). 5 patients showed unimpaired test profiles and passed the on-road evaluation. 18 patients showed severe neuropsychological deficits contrary to driving and were not recommended for on-road evaluation. Of the remaining 32 patients with some neuropsychological deficits, all 100% in the minor impaired group (n = 8) passed the driving evaluation, compared to 69% in the mildly impaired (n = 16) and 38% in the moderately impaired group (n = 8). Measures of reduced visuoconstructive ability, reaction time, visual attention, and awareness of cognitive impairments, were found to discriminate between groups. It is concluded that neuropsychological assessment of targeted functions provide an ecological valid prediction of driving skill after brain damage, but that on-road evaluation is needed as supplement in cases with ambiguous test findings.     

The differential effects of thalamus and basal ganglia on facial emotion recognition

This study examined if subcortical stroke was associated with impaired facial emotion recognition. Furthermore, the lateralization of the impairment and the differential profiles of facial emotion recognition deficits with localized thalamic or basal ganglia damage were also studied. Thirty-eight patients with subcortical strokes and 19 matched normal controls volunteered to participate. The participants were individually presented with morphed photographs of facial emotion expressions over multiple trials. They were requested to classify each of these morphed photographs according to Ekman's six basic emotion categories. The findings indicated that the clinical participants had impaired facial emotion recognition, though no clear lateralization pattern of impairment was observed. The patients with localized thalamic damage performed significantly worse in recognizing sadness than the controls. Longitudinal studies on patients with subcortical brain damage should be conducted to examine how cognitive reorganization post-stroke would affect emotion recognition.     

Using perfusion fMRI to measure continuous changes in neural activity with learning

In this study, we examine the suitability of a relatively new imaging technique, arterial spin labeled perfusion imaging, for the study of continuous, gradual changes in neural activity. Unlike BOLD imaging, the perfusion signal is stable over long time-scales, allowing for accurate assessment of continuous performance. In addition, perfusion fMRI provides an absolute measure of blood flow so signal changes can be interpreted without reference to a baseline. The task we used was the serial response time task, a sequence learning task. Our results show reliable correlations between performance improvements and decreases in blood flow in premotor cortex and the inferior parietal lobe, supporting the model that learning procedures that increase efficiency of processing will be reflected in lower metabolic needs in tissues that support such processes. More generally, our results show that perfusion fMRI may be applied to the study of mental operations that produce gradual changes in neural activity.