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.     

The symmetry of visual fields in chromatic discrimination

Both classical and recent reports suggest a right-hemisphere superiority for color discrimination. Testing highly-trained normal subjects and taking care to eliminate asymmetries from the testing situation, we found no significant differences between left and right hemifields or between upper and lower hemifields. This was the case for both of the cardinal axes of color space. In addition, there was no difference according to whether the discriminanda were delivered to the same or to different hemispheres, and we note that the same number of synapses may lie between the retina and the site of comparison whether or not the stimuli are delivered to the same hemisphere.     

The effects of total sleep deprivation on recognition memory processes: A study of event-related potential

This study examined the memorization of information after a night of normal sleep and total sleep deprivation (TSD) by means of event-related potentials (ERPs). We expected a disfacilitatory effect of TSD on memory processing. Eighteen subjects were tested twice in a counterbalanced fashion. During the study session, subjects were presented with unfamiliar face stimuli and asked to memorize them for a subsequent memory test. At the test session, the subjects were presented with the studied faces intermixed with “new” faces and asked to indicate the previously presented stimuli. The N100 was used as a covariate to control for the differences in level of vigilance between the two sessions. Sleep deprivation decreased subjects’ ability to discriminate new from previously studied stimuli and decreased the peak amplitude of the early component (N200) to the decrement of performance. In addition, following TSD the amplitude of the late frontal component (LFC), which is thought to reflect contextual processing, was decreased in covariance with the N100 vigilance component. The amplitude of the late posterior component (LPC/P600) was also reduced but was unrelated to the vigilance component of the ERP. Based on prior studies, this LPC reduction can be interpreted to indicate a decrease in information retrieved after TSD. In summary, a night of TSD decreased the amplitude of the ERPs associated with complex episodic memory task stimuli, affected the frontal cortex during episodic retrieval, and prevented the elaboration process. Furthermore, there was an inability to discriminate what is and what is not in memory, possibly due to less local processing of details.     

Left gaze bias in humans, rhesus monkeys and domestic dogs

While viewing faces, human adults often demonstrate a natural gaze bias towards the left visual field, that is, the right side of the viewee’s face is often inspected first and for longer periods. Using a preferential looking paradigm, we demonstrate that this bias is neither uniquely human nor limited to primates, and provide evidence to help elucidate its biological function within a broader social cognitive framework. We observed that 6-month-old infants showed a wider tendency for left gaze preference towards objects and faces of different species and orientation, while in adults the bias appears only towards upright human faces. Rhesus monkeys showed a left gaze bias towards upright human and monkey faces, but not towards inverted faces. Domestic dogs, however, only demonstrated a left gaze bias towards human faces, but not towards monkey or dog faces, nor to inanimate object images. Our findings suggest that face- and species-sensitive gaze asymmetry is more widespread in the animal kingdom than previously recognised, is not constrained by attentional or scanning bias, and could be shaped by experience to develop adaptive behavioural significance.     

Reduced right hemisphere activation in severely abused violent offenders during a working memory task: An fMRI study

This study uses functional magnetic resonance imaging (fMRI) to address two important gaps in our knowledge of brain functioning and violence: (1) What are the brain correlates of adults in the community who have suffered severe physical abuse early in life and who go on to perpetrate serious violence in adulthood? (2) What characterizes those who experience severe physical abuse but who refrain from serious violence? Four groups of participants recruited from the community (controls, severe physical child abuse only, serious violence only, and severely abused, seriously violent offenders) underwent fMRI while performing a visual/verbal working memory task. Violent offenders who had suffered severe child abuse show reduced right hemisphere functioning, particularly in the right temporal cortex. Abused individuals who refrain from serious violence showed relatively lower left, but higher right, activation of the superior temporal gyrus. Abused individuals, irrespective of violence status, showed reduced cortical activation during the working memory task, especially in the left hemisphere. Brain deficits were independent of IQ, history of head injury, task performance, cognitive strategy, and mental activity during the control task. Findings constitute the first fMRI study of brain dysfunction in violent offenders, and indicate that initial right hemisphere dysfunction, when combined with the effects of severe early physical abuse, predisposes to serious violence but that relatively good right hemisphere functioning protects against violence in physically abused children. Aggr. Behav. 27:111–129, 2001. © 2001 Wiley‐Liss, Inc.     

Understanding symptoms of medical frontal lobe disorder: A clinical case study

A case of anterior communicating artery aneurysm with damage to inferior medial frontal areas (Brodmann areas 25, 32, 24-inferior) is presented. Four prominent deficits are discussed: (1) anterograde amnesia, (2) inert perseverative card sorting, (3) motor stereotypies, and (4) reduplicative paramnesia. These four deficits are discussed as negative or positive symptoms, related either to damage in inferior medial frontal (Brodmann areas 25, 32, 24-inferior) regions or release phenomena of superior medial frontal (Brodmann areas 6-medial and 24-superior) regions. It is concluded that the inferior and superior medial frontal regions act as opponent processors, with the inferior (B25, 32) area functioning to switch current mental set while the superior (B24-superior, 6-medial) region functions to maintain current mental set. Testable hypotheses about the opponent processor mechanism are suggested, as applied to neuropsychiatric disorders.     

The role of regional heterogeneity in age-related differences in functional hemispheric asymmetry: an fMRI study

Neuroimaging literature has documented age-related hemispheric asymmetry reduction in frontal regions during task performances. As most studies employed working memory paradigms, it is therefore less clear if this pattern of neural reorganization is constrained by working memory processes or it would also emerge in other cognitive domains which are predominantly lateralized. Using blocked functional magnetic resonance imaging (fMRI), the present study used a homophone judgment task and a line judgment task to investigate age-related differences in functional hemispheric asymmetry in language and visuospatial processing respectively. Young and older adults achieved similar task accuracy although older adults required a significantly longer time. Age-related functional hemispheric asymmetry reduction was found only in dorsal inferior frontal gyrus and was associated with better performance when the homophone condition was contrasted against fixation, and not line condition. Our data thus highlights the importance of considering regional heterogeneity of aging effects together with general age-related cognitive processes.     

The modulation of stimulus structure on visual field asymmetry effects: The case of Chinese character recognition

Recent research suggests that visual field (VF) asymmetry effects in visual recognition may be influenced by information distribution within the stimuli for the recognition task in addition to hemispheric processing differences: Stimuli with more information on the left have a right VF (RVF) advantage because the left part is closer to the centre, where the highest visual acuity is obtained. It remains unclear whether visual complexity distribution of the stimuli also has similar modulation effects. Here we used Chinese characters with contrasting structures—left-heavy, symmetric, and right-heavy, in terms of either visual complexity of components or information distribution defined by location of the phonetic component—and examined participants' naming performance. We found that left-heavy characters had the largest RVF advantage, followed by symmetric and right-heavy characters; this effect was only observed in characters that contrasted in information distribution, in which information for pronunciation was skewed to the phonetic component, but not in those that contrasted only in visual complexity distribution and had no phonetic component. This result provides strong evidence for the influence of information distribution within the stimuli on VF asymmetry effects; in contrast, visual complexity distribution within the stimuli does not have similar modulation effects.     

Brain asymmetry and autonomic conditioning: Sensitization control

In the present experiment we report effects of cerebral asymmetry, or laterality, during classical conditioning to facial emotional stimuli. Twenty-five female subjects were presented with slides of a happy face in one visual half-field (VHF), and simultaneously a slide of an angry face in the other VHF, followed by shock as the unconditioned stimulus (UCS). To control for effects of sensitization, a new stimulus, never associated with the UCS, was introduced in the extinction phase. Dependent measures were phasic heart rate responses (HR) and skin conductance responses (SCR). The HR results showed a significant right hemisphere effect for the CS-UCS association, that was not attributable to UCS sensitization. No significant effects were found for the SCRs. The basic HR finding was a right hemisphere superiority for learning of a conditioned association.     

道德概念垂直空间隐喻理解中的映射:双向性及不平衡性

通过4个实验考察道德概念垂直空间隐喻理解中的映射机制和特征。实验1采用空间Stroop范式,发现被试判断完道德词后,对判断随后呈现在屏幕上方或下方字母的反应时的差异不显著,没有发现词汇类型对空间位置的影响。实验2采用有意识迫选法,要求被试出声读出屏幕中央的道德词后,对屏幕上方或下方的希腊语非词进行二择一迫选,发现被试读出道德词后倾向于选择屏幕上方的非词,读出不道德词后倾向于选择屏幕下方的非词。实验3仍采用Stroop范式,发现被试做出空间"上"的判断后,对随后道德词的词义判断反应时显著快于不道德词,做出空间"下"的判断后,对不道德词的反应时显著快于道德词。实验4探讨空间位置是否会对判断人物的道德性产生影响,结果发现被试倾向于认为屏幕上方的人物是道德的,而屏幕下方的人物是不道德的。4个实验的结果表明,在道德概念垂直空间隐喻的理解中,映射的方式是灵活的、双向的,既可以由始源域向目标域映射,也可以由目标域向始源域映射,但两个方向上的映射力量是不平衡的。