Comparing language lateralization determined by dichotic listening and fMRI activation in frontal and temporal lobes in children with epilepsy

We investigated the relationship between ear advantage scores on the Fused Dichotic Words Test (FDWT), and laterality of activation in fMRI using a verb generation paradigm in fourteen children with epilepsy. The magnitude of the laterality index (LI), based on spatial extent and magnitude of activation in classical language areas (BA 44/45, 21/22, 39) differed significantly for patients classified with unilateral left, compared to bilateral, language representation based on FDWT scores. Concordance with fMRI was higher for those classified with unilateral left, than bilateral language representation on the FDWT. Of note, asymmetry in temporal lobe, rather than frontal lobe, activation was more strongly related to the LI from the dichotic listening test. This study shows that the FDWT can provide a quick and valid estimate of lateralization in pre-surgical candidates, which can be readily adopted for other clinical or research purposes when an estimate of language dominance is desired.     

The specialized structure of human language cortex: pyramidal cell size asymmetries within auditory and language-associated regions of the temporal lobes

Functional lateralization of language within the cerebral cortex has long driven the search for structural asymmetries that might underlie language asymmetries. Most examinations of structural asymmetry have focused upon the gross size and shape of cortical regions in and around language areas. In the last 20 years several labs have begun to document microanatomical asymmetries in the structure of language-associated cortical regions. Such microanatomic results provide useful constraints and clues to our understanding of the biological bases of language specialization in the cortex. In a previous study we documented asymmetries in the size of a specific class of pyramidal cells in the superficial cortical layers. The present work uses a nonspecific stain for cell bodies to demonstrate the presence of an asymmetry in layer III pyramidal cell sizes within auditory, secondary auditory and language-associated regions of the temporal lobes. Specifically, the left hemisphere contains a greater number of the largest pyramidal cells, those that are thought to be the origin of long-range cortico-cortical connections. These results are discussed in the context of cortical columns and how such an asymmetry might alter cortical processing. These findings, in conjunction with other asymmetries in cortical organization that have been documented within several labs, clearly demonstrate that the columnar and connective structure of auditory and language cortex in the left hemisphere is distinct from homotopic regions in the contralateral hemisphere.     

Body image and the parietal lobes

In this review, the history of the concept of the body image in neuropsychiatry is presented. Links between the parietal cortex and the body image are discussed and the possible role of the parietal lobe in psychiatric disorders noted. The link between parietal lobe function and some neurophilosophical concepts are introduced.     

Associative memory and the medial temporal lobes

Associative recognition and recall depend on structures in the medial temporal lobes (MTLs). There is disagreement about whether associative memory is functionally heterogeneous, whether it is functionally distinct from intra-item associative memory and how the MTLs contribute to this kind of memory. Despite an increase in research on associative memory, work has lacked a theoretical framework to guide design and interpretation of studies. One view provides a useful framework by postulating that associative memories differ in the degree to which their informational components converge in MTL structures that create familiarity-supporting or recollection-supporting memory representations. Using this framework, we consider psychological, lesion and functional imaging evidence, highlighting how informational convergence in the brain underlies the associative nature of both memory and perception.     

Frontal amnesia and the dysexecutive syndrome

This study analyzes the memory deficits shown by an amnesic patient with bilateral frontal damage and a dysexecutive syndrome. He resembles a classic amnesic patient in showing grossly impaired episodic memory for both verbal and nonverbal material, together with normal digit span, and on occasion normal recency in free recall. He differs from the classic amnesic pattern however in showing an impairment in both the speed and accuracy of performance on tests of semantic memory, and in clear evidence for impaired performance on some though not all procedural learning tasks. Finally, his autobiographical memory was poor and subject to substantial confabulation. It is suggested that the pattern of deficits is consistent with a combination of a classic amnesic syndrome with the additional problems associated with the frontal dysexecutive syndrome, rather than exhibiting a qualitatively different form of amnesia.     

Adaptive versus veridical decision making and the frontal lobes

Adaptive decision making and veridical decision making are based on different mechanisms. Veridical decision making is based on the identification of the correct response, which is intrinsic to the external situation and is actor-independent. Adaptive decision making is actor-centered and is guided by the actor's priorities. The prefrontal cortex is particularly critical for adaptive decision making and less so for veridical decision making. However, most experimental procedures used in cognitive psychology and neuropsychology focus on veridical decision making and ignore adaptive decision making. Innovative experimental procedures are required to characterize the contribution of the prefrontal cortex to adaptive decision making. We have designed a prototype for such procedures, the Cognitive Bias Task, and present the novel findings generated by this task.     

Frontal tests and models for cognitive ageing

Results of investigations of how specific behavioural changes in old age may be related to local changes in the brain have been discrepant because of neglect of methodological issues. Among these are neglect of the reliability and validity of frontal and executive tests; the operational definition and construct validity of hypothetical functional processes such as “inhibition”; the nature and origins of mutual relationships between tests; the relationships of test performance to higher order constructs of general mental ability such as “gf” and, most importantly, problems of cohort selection arising from imprecise definitions of the models of the ageing process. These problems are illustrated by a discussion of the results of several experiments in which younger and older groups of people are compared on frontal and executive tests.     

Frontal EEG asymmetry and premenstrual dysphoric symptomatology

Resting frontal electroencephalographic (EEG) asymmetry has been hypothesized to tap a diathesis toward depression or other emotion-related psychopathology. Frontal EEG asymmetry was assessed in college women who reported high (n = 12) or low (n = 11) levels of premenstrual negative affect. Participants were assessed during both the follicular and the late luteal phases of the menstrual cycle. Women reporting low premenstrual dysphoric symptomatology exhibited greater relative left frontal activity at rest than did women high in premenstrual dysphoric symptomatology, an effect that was not qualified by phase of cycle. Although women with extreme levels of symptomatology were assessed, the question of whether such symptoms qualified for premenstrual dysphoric disorder criteria was not assessed. These results are consistent with a diathesis-stress model for premenstrual dysphoric symptomatology.     

Famous people knowledge and the right and left temporal lobes

It is generally accepted that the anterior temporal lobes support knowledge of famous people. The specific roles of the right and left temporal lobe remain a subject of debate, with some studies suggesting differential roles based on modality (visual versus verbal information) and others category (person knowledge versus general semantics). The present study re-examined performance of semantic dementia patients with predominantly right and predominantly left temporal lobe atrophy on famous face, famous name and general semantic tasks, with the specific aim of testing the hypothesis that the right temporal lobe has a privileged role for person knowledge and the left temporal lobe for general semantic knowledge. Comparisons of performance rankings across tasks showed no evidence to support this hypothesis. By contrast, there was robust evidence from naming, identification and familiarity measures for modality effects: right-sided atrophy being associated with relatively greater impairment for faces and visual tasks and left-sided atrophy for names and verbal tasks. A double dissociation in test scores in two patients reinforced these findings. The data present a challenge for the influential `semantic hub' model, which views the anterior temporal lobes as an area of convergence in which semantic information is represented in amodal form.     

Infant artificial language learning and language acquisition

The rapidity with which children acquire language is one of the mysteries of human cognition. A view held widely for the past 30 years is that children master language by means of a language-specific learning device. An earlier proposal, which has generated renewed interest, is that children make use of domain-general, associative learning mechanisms. However, our current lack of knowledge of the actual learning mechanisms involved during infancy makes it difficult to determine the relative contributions of innate and acquired knowledge. A recent approach to studying this problem exposes infants to artificial languages and assesses the resulting learning. In this article, we review studies using this paradigm that have led to a number of exciting discoveries regarding the learning mechanisms available during infancy. These studies raise important issues with respect to whether such mechanisms are general or specific to language, the extent to which they reflect statistical learning versus symbol manipulation, and the extent to which such mechanisms change with development. The fine-grained characterizations of infant learning mechanisms that this approach permits should result in a better understanding of the relative contributions of, and the dynamic between, innate and learned factors in language acquisition.     

Frontal Brain Electrical Activity in Shyness and Sociability

A number of studies have shown that shyness and sociability may be two independent personality traits that are distinguishable across a variety of measures and cultures. Utilizing recent frontal activation–emotion models as a theoretical framework, this study examined the pattern of resting frontal electroencephalographic (EEG) activity in undergraduates who self-reported high and low shyness and sociability. Analyses revealed that shyness was associated with greater relative right frontal EEG activity, whereas sociability was associated with greater relative left frontal EEG activity. Also, different combinations of shyness and sociability were distinguishable on the basis of resting frontal EEG power. Although high-shy/high-social and high-shy/low-social subjects both exhibited greater relative right frontal EEG activity, they differed significantly on EEG power in the left, but not right, frontal lead. High-shy/high-social subjects exhibited significantly less EEG power (i.e., more activity) in the left frontal lead compared with the high-shy/low-social subjects. These findings suggest that in distinguishing individual differences in personality and personality subtypes, it is important to consider not only frontal EEG asymmetry measures, but also the pattern of absolute EEG power in each frontal hemisphere.     

Frontal theta power linked to neuroticism and avoidance

Approach–avoidance conflict is thought to generate negative affective bias, mediated by theta rhythms. This process is distinct from, and adds to, the effects of simple aversive input. We assessed this distinction by holding gain constant and increasing loss value so that conflict and simple aversion peaked in the conflict (gain equals loss) and loss (net loss) conditions, respectively. Right frontal areas showed increases in both conflict- and loss-induced theta power. However, loss, but not conflict, power was correlated with avoidance and neuroticism, showing a Gender x Hemisphere interaction. We concluded that multiple aversive processes converge in lateral frontal networks and that individual differences in theta response in these networks may reflect differences in behavioural and emotional reactivity to aversive events.     

Frontal Lobe Function and Pain in the Elderly

We review the literature on pain and aging and conclude that evidence supports a hypothesis that right frontal cortex contributes to the mediation of the chronic pain experience in elderly persons with chronic pain syndromes. Evidence for the right frontal pain hypothesis comes from clinical, neurocognitive, and neuroimaging studies, which implicate right inferior and orbitofrontal cortex in (1) the persistent pain experience, (2) negative emotional states, (3) retrieval of negative emotional and autobiographical memories, (4) regulation of autonomic arousal, and (5) regulation of attentional and pain functions of the anterior cingulate region. Right frontal dysfunction is also implicated in the effects of cognitive aging. If right frontal neurocognitive systems are affected in cognitively impaired elderly, and if (by hypothesis) the right frontal cortex also plays a major role in the experience of chronic pain, then cognitively impaired elderly with right frontal dysfunction should be protected to some extent from persistent pain syndromes. Available evidence supports this proposition.