Brain activation while forming memories of fearful and neutral faces in women and men

Event-related functional MRI (fMRI) was used to assess brain activity during encoding of fearful and neutral faces in 12 women and 12 men. In a subsequent memory analysis, the authors separated successful from unsuccessful encoding of both types of faces, based on whether they were remembered or forgotten in a later recognition memory test. Overall, women and men recruited overlapping neural circuitries. Both sexes activated right-sided medial-temporal regions during successful encoding of fearful faces. Successful encoding of neutral faces was associated with left-sided lateral prefrontal and right-sided superior frontal activation in both sexes. In women, relatively greater encoding related activity for neutral faces was seen in the superior parietal and parahippocampal cortices. By contrast, men activated the left and right superior/middle frontal cortex more than women during successful encoding of the same neutral faces. These findings suggest that women and men use similar neural networks to encode facial information, with only subtle sex differences observed for neutral faces.     

The Interpretation of Sentence Ambiguity in Patients with Unilateral Focal Brain Surgery

Interpretations of ambiguous sentences were studied in patients with unilateral anterior temporal lobectomy or selective amygdalo-hippocampectomy. The sentences represented lexical and syntactic ambiguities. In both left- and right-sided groups, regardless of type of surgery, total mean score on the test was below normal. Left-sided cases, regardless of type of surgery, provided significantly fewer alternative interpretations than right-sided cases. The results suggest greater left than right hemisphere specialization in both lexical and syntactic processing, but also suggest right hemisphere involvement in resolution of lexical ambiguity.     

Involuntary vocalisations and a complex hyperkinetic movement disorder following left side thalamic haemorrhage

A variety of involuntary speech phenomena as for example palilalia have been described as consequences of neurological disorders. Palilalia is the involuntary repetition of syllabels, words and phrases in ongoing speech. We describe a 73 year old woman who suffered from a hypertensive thalamic haemorrhage. MRI revealed that the lesion was predominantly located within the pulvinar, extending to the lateroposterior thalamic nuclei and to the pretectal area with possible involvement of the medial geniculate body. Few months after the event she developed involuntary vocalisations with whole words and meaningless syllables being rapidly reiterated. In contrast to typical palilalia these vocalisations were not meaningfully related to the ongoing speech of the patient. In addition, the patient developed a complex hyperkinetic movement disorder with right-sided painful hemidystonia and bilateral clonic jerks and a right-sided postural tremor.     

From the left to the right: How the brain compensates progressive loss of language function

In normal right-handed subjects language production usually is a function oft the left brain hemisphere. Patients with aphasia following brain damage to the left hemisphere have a considerable potential to compensate for the loss of this function. Sometimes, but not always, areas of the right hemisphere which are homologous to language areas of the left hemisphere in normal subjects are successfully employed for compensation but this integration process may need time to develop. We investigated right-handed patients with left hemisphere brain tumors as a model of continuously progressive brain damage to left hemisphere language areas using functional neuroimaging and transcranial magnetic stimulation (TMS) to identify factors which determine successful compensation of lost language function. Only patients with slowly progressing brain lesions recovered right-sided language function as detected by TMS. In patients with rapidly progressive lesions no right-sided language function was found and language performance was linearly correlated with the lateralization of language related brain activation to the left hemisphere. It can thus be concluded that time is the factor which determines successful integration of the right hemisphere into the language network for compensation of lost left hemisphere language function.     

Left sidedness and sleep difficulty: the alinormal syndrome

Four indexes of laterality: handedness, footedness, eyedness, and earedness, were assessed in a sample of 1274 subjects. Left- and right-sided groups were compared on two aspects of self-reported sleep difficulty: trouble falling asleep and frequent night wakenings. The incidence of sleep difficulty was found to be elevated in the left-sided groups. The results are discussed in terms of a possible complex of behavioral deviations from the statistical norm, called the alinormal syndrome.     

Lateral differences in habituation of ipsilateral head-turning to repeated tactile stimulation in the human newborn

Lateral differences in habituation of ipsilateral head-turning to repeated tactile perioral stimulation following midline head restriction was studied in 44 full-term neonates. Left-sided stimulation had a significantly greater and faster decremental effect than right-sided stimulation. Even in the absence of tactile stimulation (Control Group), head-turning to the left decreased systematically whereas head-turning to the right did not. The transient efficacy of prior midline head restriction for the elimination of lateral differences in both spontaneous head movements and responsiveness to tactile input suggests that behavioral asymmetry is already well-established in the newborn.     

PTSD arousal and depression symptoms associated with increased right-sided parietal EEG asymmetry

Researchers have proposed that depression and particular types of anxiety are associated with unique patterns of regional brain activation. The authors examined the relationship among posttraumatic stress disorder (PTSD), anxiety, and depressive symptoms and frontal, temporal, and parietal EEG alpha asymmetry in female Vietnam War nurse veterans. The results indicate that PTSD arousal symptoms are associated with increased right-sided parietal activation. However, the combination of arousal, depression, and their interaction explain more than twice the variance in parietal asymmetry compared with arousal alone. The results support the contention that the association between anxiety and right-sided posterior activation is specific to the anxious arousal subtype. These findings underscore the importance of isolating, both theoretically and statistically, emotional subcomponents in studies of regional brain activation.     

Hand preference for pointing gestures and bimanual manipulation around the vocabulary spurt period

This study investigated the development of hand preference for bimanual manipulative activities and pointing gestures in toddlers observed longitudinally over a 5-month period, in relation to language acquisition. The lexical spurt was found to be accompanied by an increase in the right-sided bias for pointing but not for manipulation. Moreover, results revealed a significant correlation between hand preference for imperative pointing gestures and manipulative activities in children who did not experience the lexical spurt during the observational period. By contrast, measures of handedness for declarative pointing were never correlated with those of handedness for manipulation. This study illustrates the complex relationship between handedness and language development and emphasizes the need to take the different functions of pointing gestures into account.     

Regional brain electrical asymmetries discriminate between previously depressed and healthy control subjects

Baseline resting electroencephalogram (EEG) activity was recorded from 6 normothymic depressives and 8 controls using three different reference montages. Power in all frequency bands was extracted by Fourier transformation. Significant Group X Region X Hemisphere interactions were found consistently for alpha band power only. Previously depressed subjects had less left-sided anterior and less right-sided posterior activation (i.e., more alpha activity) than did never depressed subjects. Previously depressed subjects had no history of pharmacological treatment and did not differ from controls in emotional state at the time of testing. The pattern of anterior and posterior asymmetry in the previously depressed subjects is similar to that found in acutely depressed subjects and suggests that this may be a state-independent marker for depression.     

The effect of familial sinistrality on the relation between schizophrenialike thinking and pseudoneglect

We have recently reported a correlation between schizophrenialike symptoms and the degree of pseudoneglect in healthy right-handers. We aimed to investigate the effect of familial sinistrality (FS) on this relation. Seventy-six healthy right-handers were divided into four groups on the basis of gender and FS. A computerized version of Corsi's task was used as the visuospatial task. Subjects filled in the Magical Ideation Scale (MI), which asked for delusionlike beliefs, and performed the Corsi's task using each hand. Performance of both hemispaces was separately evaluated. In all groups, performance of the left hemispace was better than that of the right hemispace and FS+ subjects performed better than FS- subjects. When the right hand was used, performance was correlated to MI scores only for FS- groups. Findings suggest that the correlation between right-sided neglect and proneness to schizotypy in normal right-handers is affected by FS.     

Within-modal and cross-modal reliabilities of two laterality tests

Sixteen right handers were given four tests of a dichotic listening recall task (concrete words) and a visual half-field recall task (letters). There was a significant right ear and right visual half-field superiority for the four test sessions, with improvement in recall scores over sessions. Pearson correlations for each ear on the four dichotic tests ranged from .74 to .90. Correlations on the visual half-field scores, however, were significant only after the first session. Analysis of stability in lateral preferences across modalities revealed stable and reliable performance, particularly in the last two testings, where 81.3% of the subjects had a right-sided asymmetry. Cross-modal correlations, however, were not significant. Implications regarding predictions of speech laterality are discussed in the light of these findings.     

The dilemma of localizing language: John Abercrombie's unexploited evidence

John Abercrombie (1780-1844) was considered the most eminent Scottish physician of his time. In his Pathological and Practical Researches on the Diseases of the Brain and Spinal Cord (1836, Edinburgh: John Carfrae and Son, 3rd ed.) he described the cases of 140 patients with cerebral disorders, 48 of whom suffered from language disturbances. Despite the overwhelming clinical and neuropathological evidence of a close association between language disorder and right-sided hemiparesis or diseases of the left hemisphere, and in spite of his great interest in language disorders, he made no attempt to localize the aphasic syndrome to a specific brain area.     

Acoustic analysis of affective prosody during right-sided Wada Test: a within-subjects verification of the right hemisphere's role in language

A within-subjects study of the affective characteristics of voice was carried out in patients undergoing a Wada Test (WT). All patients became densely aphasic after the left-sided WT and lost the ability to impart affect into speech after the right-sided WT. The affective changes in voice induced by the Wada test were acoustically analyzed by computer-assisted techniques and compared to data obtained pre-Wada and post-Wada. The statistical results, using a one-way analysis of variance for repeated measures, confirmed robustly the current view that the right hemisphere modulates dominantly the affective components of language. The results are also evaluated in light of recent clinical and acoustical data regarding the organization of language in speakers of tone languages, thus, allowing the authors to address issues concerning universal principles of brain-language-behavioral relationships.     

Effects of attention and unilateral neglect on auditory stream segregation

Two pairs of experiments studied the effects of attention and of unilateral neglect on auditory streaming. The first pair showed that the build up of auditory streaming in normal participants is greatly reduced or absent when they attend to a competing task in the contralateral ear. It was concluded that the effective build up of streaming depends on attention. The second pair showed that patients with an attentional deficit toward the left side of space (unilateral neglect) show less stream segregation of tone sequences presented to their left than to their right ears. Streaming in their right ears was similar to that for stimuli presented to either ear of healthy and of brain-damaged controls, who showed no across-ear asymmetry. This result is consistent with an effect of attention on streaming, constrains the neural sites involved, and reveals a qualitative difference between the perception of left- and right-sided sounds by neglect patients.     

Lateralization of squamous cell carcinomas in the head-neck region

Earlier studies have shown the lateralization of several immune disorders, including herpes zoster infection and breast cancer. We investigated whether there is lateralization of squamous cell carcinomas in the head-neck region and a relation of handedness with this cancer. Analysis showed right-sided lateralization of head-heck cancers in right-handed patients and vice versa in left-handed ones and a higher rate of left-handedness in patients with squamous cell cancer. Associations among left-handedness, squamous cell carcinoma, and its lateralization may result from a genetic togetherness.     

Modulation of auditory spatial attention by visual emotional cues: differential effects of attentional engagement and disengagement for pleasant and unpleasant cues

Previous research has demonstrated that threatening, compared to neutral pictures, can bias attention towards non-emotional auditory targets. Here we investigated which subcomponents of attention contributed to the influence of emotional visual stimuli on auditory spatial attention. Participants indicated the location of an auditory target, after brief (250 ms) presentation of a spatially non-predictive peripheral visual cue. Responses to targets were faster at the location of the preceding visual cue, compared to at the opposite location (cue validity effect). The cue validity effect was larger for targets following pleasant and unpleasant cues compared to neutral cues, for right-sided targets. For unpleasant cues, the crossmodal cue validity effect was driven by delayed attentional disengagement, and for pleasant cues, it was driven by enhanced engagement. We conclude that both pleasant and unpleasant visual cues influence the distribution of attention across modalities and that the associated attentional mechanisms depend on the valence of the visual cue.     

Handedness, footedness, and eyedness

There is no agreement in the literature on whether there are associations among handedness, footedness, and eyedness among normal populations. These need to be clarified before studying abnormal populations. The majority of people have a right-sided preference for each of the three measures of laterality and hence some association is to be expected due to chance alone. Using three categories of laterality a statistical method which is new to these sorts of data has been used which allows the observed percentage agreement to be compared with that expected by chance for all three measures together (as well as in pairs). Its application to data from a sample of 192 young naval recruits suggests that there probably is a generalised dimension of motor laterality, at least among males.     

Approach-withdrawal and cerebral asymmetry: emotional expression and brain physiology. I

In this experiment, we combined the measurement of observable facial behavior with simultaneous measures of brain electrical activity to assess patterns of hemispheric activation in different regions during the experience of happiness and disgust. Disgust was found to be associated with right-sided activation in the frontal and anterior temporal regions compared with the happy condition. Happiness was accompanied by left-sided activation in the anterior temporal region compared with disgust. No differences in asymmetry were found between emotions in the central and parietal regions. When data aggregated across positive films were compared to aggregate negative film data, no reliable differences in brain activity were found. These findings illustrate the utility of using facial behavior to verify the presence of emotion, are consistent with the notion of emotion-specific physiological patterning, and underscore the importance of anterior cerebral asymmetries for emotions associated with approach and withdrawal.     

Differences in asymmetric perception of facial expression in free-vision chimeric stimuli and reaction time

Two forms of a Chimeric Faces Free-Vision Task used to estimate cerebral asymmetry for perceiving facial expression were given to young male subjects, n = 60 in a first session and n = 40 in a retest session. Test-retest and split-half reliabilities were high. As expected from assumptions of right-hemisphere specialization for processing expression, faces with left-sided smiles were more frequently judged as looking happier than those with right-sided smiles in both forms. However, there were individual differences in direction and extent of bias, which were systematically related to reaction time, right visual field-biased subjects being slower. Differences in lateral bias as well as in reaction time are assumed to reflect individual patterns of hemispheric activation, whereas the average left bias in the present male group may reflect right-hemisphere specialization for processing of facial expression.     

Depression, anxiety, and resting frontal EEG asymmetry: a meta-analytic review

Emotion-related disturbances, such as depression and anxiety, have been linked to relative right-sided resting frontal electroencephalograph (EEG) asymmetry among adults and infants of afflicted mothers. However, a somewhat inconsistent pattern of findings has emerged. A meta-analysis was undertaken to (a) evaluate the magnitude of effects across EEG studies of resting frontal asymmetry and depression, anxiety, and comorbid depression and anxiety and (b) determine whether certain moderator variables could help reconcile inconsistent findings. Moderate effects of similar magnitude were obtained for the depression and anxiety studies, whereas a smaller effect emerged for comorbid studies. Three moderating variables predicted effect sizes: (a) Shorter EEG recording periods were associated with larger effects among adults, (b) different operationalizations of depression yielded effects of marginally different magnitudes, and (c) younger infant samples showed larger effects than older ones. The current data support a link between resting frontal EEG asymmetry and depression and anxiety and provide a partial account of inconsistent findings across studies.