A selective and critical review of neuropsychological deficits and the frontal lobes

Presumptions about the functions of the frontal lobes, and the sensitivity and specificity of certain tests to measure frontal lobe functions, are having a substantial influence on both clinical and research conclusions. In this paper the authors examine the details of the studies that have contributed to these presumptions, and find that the evidence to support these conclusions is weak. A detailed evaluation of the evidence relating to the Wisconsin Card Sorting Test and the Thurstone Word Fluency Test is also presented. Finally, the development of the belief that frontal lobe functions can be specifically measured is reviewed. The authors of this paper conclude that the bewildering array of deficits attributed to frontal lesions still seems to prevail.     

Frontal-Lobe Involvement in Spatial Memory: Evidence from PET,fMRI, and Lesion Studies

Many studies have identified the prefrontal cortex as the brain area that is critical for spatial memory, both in humans and in other primates. Other studies, however, have failed to establish this relation. Therefore, the aim of this paper was to review the literature regarding the role of the human prefrontal lobe in spatial memory. This was done by examining the evidence obtained from neuropsychological patients and from studies using brain-imaging techniques (PET and fMRI). Evidence supporting the notion that the prefrontal cortex is extensively involved in spatial working memory was found. The majority of these studies, however, suggests that frontal-lobe involvement is not related to the type of material that is being processed (e.g., spatial vs. nonspatial), but to process-specific functions, such as encoding and retrieval. Theoretically, these functions could be linked to the central executive within Baddeley's working-memory model, or to recent theories that emphasize the various processes that play a role in working memory. Also, methodological issues were discussed. Further research is needed to enhance our understanding of the precise interaction of domain-specific and general processes.     

Learning new names for new objects: cortical effects as measured by magnetoencephalography

We tracked the evolvement of naming-related cortical dynamics with magnetoencephalography when five normal adults successfully learned names and/or meanings of unfamiliar objects. In all subjects, the learning of new names was associated with pronounced cortical effects. The learning effect was of long latency and emerged as a change of activation in the same cortical network that was active during naming of familiar items. In four out of five subjects, the cortical learning effect occurred in the inferior parietal lobe. In three of these subjects, the cortical effect was left-sided. These results suggest that the inferior parietal lobe plays an important role in the acquisition of novel words, presumably as a part of working memory systems.     

Liberal bias mediates emotion recognition deficits in frontal traumatic brain injury

It is well-known that patients having sustained frontal-lobe traumatic brain injury (TBI) are severely impaired on tests of emotion recognition. Indeed, these patients have significant difficulty recognizing facial expressions of emotion, and such deficits are often associated with decreased social functioning and poor quality of life. As of yet, no studies have examined the response patterns which underlie facial emotion recognition impairment in TBI and which may lend clarity to the interpretation of deficits. Therefore, the present study aimed to characterize response patterns in facial emotion recognition in 14 patients with frontal TBI compared to 22 matched control subjects, using a task which required participants to rate the intensity of each emotion (happiness, sadness, anger, disgust, surprise and fear) of a series of photographs of emotional and neutral faces. Results first confirmed the presence of facial emotion recognition impairment in TBI, and further revealed that patients displayed a liberal bias when rating facial expressions, leading them to associate intense ratings of incorrect emotional labels to sad, disgusted, surprised and fearful facial expressions. These findings are generally in line with prior studies which also report important facial affect recognition deficits in TBI patients, particularly for negative emotions.     

Building phrases in language production: An MEG study of simple composition

Although research on language production has developed detailed maps of the brain basis of single word production in both time and space, little is known about the spatiotemporal dynamics of the processes that combine individual words into larger representations during production. Studying composition in production is challenging due to difficulties both in controlling produced utterances and in measuring the associated brain responses. Here, we circumvent both problems using a minimal composition paradigm combined with the high temporal resolution of magnetoencephalography (MEG). With MEG, we measured the planning stages of simple adjective–noun phrases (‘red tree’), matched list controls (‘red, blue’), and individual nouns (‘tree’) and adjectives (‘red’), with results indicating combinatorial processing in the ventro-medial prefrontal cortex (vmPFC) and left anterior temporal lobe (LATL), two regions previously implicated for the comprehension of similar phrases. These effects began relatively quickly (∼180 ms) after the presentation of a production prompt, suggesting that combination commences with initial lexical access. Further, while in comprehension, vmPFC effects have followed LATL effects, in this production paradigm vmPFC effects occurred mostly in parallel with LATL effects, suggesting that a late process in comprehension is an early process in production. Thus, our results provide a novel neural bridge between psycholinguistic models of comprehension and production that posit functionally similar combinatorial mechanisms operating in reversed order.     

Dichotic listening with forced attention in patients with temporal lobe epilepsy: significance of left hemisphere cognitive dysfunction

Fifty right-handed patients with focal temporal lobe epilepsy were administered a dichotic listening test with consonant-vowel syllables under non-forced, forced right and forced left attention conditions, and a neuropsychological test battery. Dichotic listening performance was compared in subgroups with and without left hemisphere cognitive dysfunction, measured by the test battery, and in subgroups with left and right temporal epileptic focus. Left hemisphere cognitive dysfunction led to more correct responses to left ear stimuli in all three attention conditions, and fewer correct responses to right ear stimuli in the non-forced attention condition. This was probably caused by basic left hemisphere perceptual dysfunction. Dichotic listening was less affected by a left-sided epileptic focus than by left hemisphere cognitive dysfunction. General cognitive functioning influenced dichotic listening performance stronger in forced than in non-forced attention conditions. Larger cerebral networks were probably involved in the forced attention conditions due to the emphasis on conscious effort.     

Connectivity among semantic associates: an fMRI study of semantic priming

Semantic priming refers to a reduction in the reaction time to identify or make a judgment about a stimulus that has been immediately preceded by a semantically related word or picture and is thought to result from a partial overlap in the semantic associates of the two words. A semantic priming lexical decision task using spoken words was presented in event-related fMRI and behavioral paradigms. Word pairs varied in terms of semantic relatedness and the connectivity between associates. Thirteen right-handed subjects underwent fMRI imaging and 10 additional subjects were tested in a behavioral version of the semantic priming task. It was hypothesized priming would be greatest, reaction time fastest, and cortical activation reduced the most for related word pairs of high connectivity, followed by related word pairs of low connectivity, and then by unrelated word pairs. Behavioral and fMRI results confirmed these predictions. fMRI activity located primarily in bilateral posterior superior and middle temporal regions showed modulation by connectivity and relatedness. The results suggest that these regions are involved in semantic processing.     

EDITORIAL

The aim of the present study was to evaluate the usefulness of Barkley’s (1997a) model of inhibition and executive functioning in describing the deficits associated with Attention Deficit Hyperactivity Disorder (ADHD). Besides group differences, the present study addressed the question of independent effects of inhibition and the other executive functions in discriminating between children with ADHD and controls and how well, in terms of sensitivity and specificity, these measures can classify the children into the correct group. The results showed that children with ADHD differed significantly from controls with regard to measures of inhibition as well as all other executive function measures, except repetition of hand movements. In logistic regression models, three different measures tapping inhibition, working memory and emotion regulation were shown to be significant independent predictors of group membership. The sensitivity for these three variables as a set was 76.2, the specificity was 90.5, with a total of 86% of the sample correctly classified. When excluding the parental rating of emotion regulation, the overall classification rate decreased some, but was still relatively high in comparison with previous studies within this area of research.     

Extracorporeal Membrane Oxygenation versus Conventional Treatment: Neurodevelopmental and Social Outcomes at 24 Months

The purpose of this prospective, controlled study was to compare neurodevelopmental and social outcomes at 2 years of age for children treated with extracorporeal membrane oxygenation (ECMO; n = 25) to those of children with severe respiratory illness treated with conventional methods (CT; n = 16) and to matched, healthy full-term (FT; n = 29) children. Mothers' parenting attitudes and children's mental, motor, language, exploratory play, and social competence skills were assessed. A retrospective chart review was also undertaken to further describe the groups with respect to the results of neuroimaging, audiologic, and neuromotor examinations. The FT group had significantly higher mental, motor, and language scores as compared to the ECMO and CT groups. Groups did not differ on measures of behavior, social competence, exploratory play skills, or parental attitudes. Specifically for the ECMO group, there was a trend toward language being more problematic than other areas of development. In general, the data demonstrate that severe respiratory complications, regardless of type of treatment, place children at increased risk for neurodevelopmental difficulties.