Cerebral lateralization and general intelligence: gender differences in a transcranial Doppler study

The present study evaluated cerebral lateralization during Raven's progressive matrices (RPM) paradigm in female and male subjects. Bilateral simultaneous transcranial Doppler (TCD) ultrasound was used to measure mean blood flow velocities (MBFV) in the right and left middle cerebral arteries (MCAs) in 24 (15 females and 9 males) right-handed normal subjects. The female subjects used a left hemisphere strategy, while males used a right hemisphere strategy to successfully solve RPM tasks. This implies that general intelligence is associated with neural systems within one hemisphere that are accessible to a variety of cognitive processes.     

Exceptional lexical skills but executive language deficits in school starters and young adults with Turners syndrome: implications for X chromosome effects on brain function

TS school starters had enhanced receptive and expressive language on standardised assessment (CELF-P) and enhanced rhyme judgements, spoonerisms, and lexical decision, indicating enhanced phonological skills and word representations. There was marginal but consistent advantage across lexico-semantic tasks. On executive tasks, speeded naming of numbers was impaired but not pictures. Young TS adults had enhanced naming and receptive vocabulary, indicating enhanced semantic skills. There were consistent deficits in executive language: phonemic oral fluency, rhyme fluency, speeded naming of pictures, numbers and colours; sentence completion requiring supression of prepotent responses.Haploinsufficiency of X-chromosome drives mechanisms that affect the anatomical and neurochemical development of the brain, resulting in enhanced temporal lobe aspects of language. These strengths co-exist with impaired development of frontal lobe executive language systems. This means not only that these elements of language can decouple in development but that their very independence is driven by mechanisms linked to the X-chromosome.     

Decreased functional brain activation in Friedreich ataxia using the Simon effect task

The present study applied the Simon effect task to examine the pattern of functional brain reorganization in individuals with Friedreich ataxia (FRDA), using functional magnetic resonance imaging (fMRI). Thirteen individuals with FRDA and 14 age and sex matched controls participated, and were required to respond to either congruent or incongruent arrow stimuli, presented either to the left or right of a screen, via laterally-located button press responses. Although the Simon effect (incongruent minus congruent stimuli) showed common regions of activation in both groups, including the superior and middle prefrontal cortices, insulae, superior and inferior parietal lobules (LPs, LPi), occipital cortex and cerebellum, there was reduced functional activation across a range of brain regions (cortical, subcortical and cerebellar) in individuals with FRDA. The greater Simon effect behaviourally in individuals with FRDA, compared with controls, together with concomitant reductions in functional brain activation and reduced functional connectivity between cortical and sub-cortical regions, implies a likely disruption of cortico-cerebellar loops and ineffective engagement of cognitive/attention regions required for response suppression.     

Age-related differences in the elderly in a spatial recognition task

ABSTRACT

Spatial memory is a cognitive ability which declines with ageing thus showing changes in some process such as the use of allocentric strategies. These age-related changes in spatial orientation suggest that this skill could be an adequate marker of cognitive decline. Many tasks used in investigation to assess spatial memory demand a participant’s active role, which involves that the navigational experience is different for everyone. In this study, the Almeria Spatial Memory Recognition Test (ASMRT), a test based on a recognition paradigm, was used to offer the same experience with the environment. The aim of this research was to determine if the ASMRT is suitable to be applied in the elderly and detect spatial memory differences as one age. The ASMRT and other neuropsychological tests were applied in a sample aged between 50and 79 years. Results revealed a decrease in the ASMRT performance by the older group. No gender differences were found. Performance in attention and visuospatial working memory tests revealed some correlations with the ASMRT performance. In conclusion, this study demonstrates that 70–79-year-old participants clearly show age-related changes in spatial memory. Thanks to its simplicity the ASMRT could be used as a screening test in medical practice.     

Age-related differences in attentional networks of alerting and executive control in young, middle-aged, and older Chinese adults

Previous studies suggest that aging is associated with impairment of attention. However, it is not known whether this represents a global attentional deficit or relates to a specific attentional network. We used the attention network test to examine three groups of younger, middle-aged, and older participants with respect to the efficiency of three anatomically defined attentional networks: alerting network, orienting network, and executive control network. Age-related change was found to have the greatest effect on the executive network and the least effect on the alerting network as well as on overall mean response time. Impairment of the orienting network was found to be insignificant. Age-related deterioration of the prefrontal lobe, the dopaminergic system, and function of specific genes may explain the age-related changes in executive attention, which occur after the fourth decade of life.     

Age-related differences in the involvement of the prefrontal cortex in attentional control

We investigated the relative involvement of cortical regions supporting attentional control in older and younger adults during performance on a modified version of the Stroop task. Participants were exposed to two different types of incongruent trials. One of these, an incongruent-ineligible condition, produces conflict at the non-response level, while the second, an incongruent-eligible condition, produces conflict at both non-response and response levels of information processing. Greater attentional control is needed to perform the incongruent-eligible condition compared to other conditions. We examined the cortical recruitment associated with this task in an event-related functional magnetic resonance imaging paradigm in 25 older and 25 younger adults. Our results indicated that while younger adults demonstrated an increase in the activation of cortical regions responsible for maintaining attentional control in response to increased levels of conflict, such sensitivity and flexibility of the cortical regions to increased attentional control demands was absent in older adults. These results suggest a limitation in older adults’ capabilities for flexibly recruiting the attentional network in response to increasing attentional demands.     

Age of acquisition effects on the functional organization of language in the adult brain

Using functional magnetic resonance imaging (fMRI), we neuroimaged deaf adults as they performed two linguistic tasks with sentences in American Sign Language, grammatical judgment and phonemic-hand judgment. Participants’ age-onset of sign language acquisition ranged from birth to 14 years; length of sign language experience was substantial and did not vary in relation to age of acquisition. For both tasks, a more left lateralized pattern of activation was observed, with activity for grammatical judgment being more anterior than that observed for phonemic-hand judgment, which was more posterior by comparison. Age of acquisition was linearly and negatively related to activation levels in anterior language regions and positively related to activation levels in posterior visual regions for both tasks.     

The role of perception, language, and preference in the developmental acquisition of basic color terms

When learning basic color vocabulary, young children show a selective delay in the acquisition of brown and gray relative to other basic color terms. In this study, we first establish the robustness of this finding and then investigate the extent to which perception, language, and color preference may influence color conceptualization. Experimental tasks were designed to measure different aspects of perceptual color processing (discrimination and saliency), color preference and objective counts of color term frequency in preschool-directed language (books and mothers' speech) were used to compare the acquisition of three groups of colors: primary colors, secondary colors (orange, pink, and purple) that appear at the same time as the primary colors, and secondary colors (brown and gray) that appear late. Although our results suggest that perception does not directly shape young children's color term acquisition, we found that children prefer brown and gray significantly less than basic colors and that these color terms appear significantly less often in child-directed speech, suggesting that color preference, linguistic input, and developing color cognition may be linked.     

Individual differences in the acquisition of second language phonology

Perceptual training was employed to characterize individual differences in non-native speech sound learning. Fifty-nine adult English speakers were trained to distinguish the Hindi dental–retroflex contrast, as well as a tonal pitch contrast. Training resulted in overall group improvement in the ability to identify and to discriminate the phonetic and the tonal contrasts, but there were considerable individual differences in performance. A category boundary effect during the post-training discrimination of the Hindi but not of the tonal contrast suggests different learning mechanisms for these two stimulus types. Specifically, our results suggest that successful learning of the speech sounds involves the formation of a long-term memory category representation for the new speech sound.     

The representation of discourse in the two hemispheres: an individual differences investigation

Two experiments were conducted to investigate discourse representation in the two cerebral hemispheres as a function of reading skill. We used a lateralized visual-field procedure to compare left hemisphere (LH) and right hemisphere (RH) sensitivity to different discourse relations in readers with varying skill levels. In Experiment 1, we investigated two levels of discourse representation in memory: (a) the propositional representation and (b) the discourse model. We found that all readers were sensitive to propositional relations in the LH. In contrast, sensitivity to propositional relations in the RH increased as a function of reading skill. In addition, reading skill was positively related to topic relations in the LH, whereas it was negatively in the RH. In Experiment 2, we investigated propositional relations of different distances and again found that all readers were sensitive to propositional relations in the LH, whereas sensitivity to propositional relations in the RH was negatively related to reading skill. In general, reading skill appears to be associated with left-lateralized discourse representations.     

Individual differences in the neural basis of causal inferencing

This study used fMRI to examine individual differences in the neural basis of causal inferencing. Participants with varying language skill levels, as indexed by scores on the vocabulary portion of the Nelson-Denny Reading Test, read four types of two-sentence passages in which causal relatedness (moderate and distant) and presence or absence of explicit clause connectives were orthogonally varied to manipulate coherence and cohesion during inference generation. Skilled readers showed better neural efficiency (less activation) during all context sentences and during all inference conditions. Increased activation in less-skilled readers was most extensively distributed in the right hemisphere (RH) homologues of left hemisphere (LH) language areas, especially in the most difficult passage types. Skilled readers also showed greater sensitivity to coherence (greater activation and synchronization in moderately related than distantly related passages) whereas less-skilled readers showed sensitivity to cohesion (greater activation and synchronization when clause connectives were present than when they were not). These finding support the hypothesis that skilled reading comprehension requires recruitment of the RH on an “as needed” basis. We describe the dynamic spillover hypothesis, a new theoretical framework that outlines the conditions under which RH language contributions are most likely evoked.     

Sex differences in English language acculturation and learning strategies among Vietnamese adults aged 40 and over in the United States

This study examines sex differences in English language acculturation and learning strategies among older Vietnamese in the United States in a nationwide probability sample. Data of this study came from the Southeast Asian Refugee Self-Sufficient Study (1982). The results reveal that older Vietnamese women had more problems with their English language than older Vietnamese men. In addition, the Vietnamese men were more likely to use various learning strategies to improve their English skills than the women.     

Sex differences in processing aggression words using the Emotional Stroop task

There is a robust relationship between the salience of stimulus materials presented in the Emotional Stroop task and inhibition of response in clinical populations. Researchers have now found information‐processing biases in both forensic and non‐forensic samples presented with threatening or aggressive stimuli [Cohen et'al., 1998; Eckhardt and Cohen, 1997; Smith and Waterman, 2003; Van Honk et'al., 2001]. We sought to explore sex differences in processing words relating to acts of direct and indirect aggression using a group of undergraduates (50 males and 50 females). Participants also completed self‐report questionnaires (AQ and EXPAGG) to allow some consideration of the relationship between objective and subjective measures. We predicted that males would demonstrate delayed responses when presented with words relating to acts of direct aggression. We also predicted that high levels of physical aggression would be the best predictor of bias for direct aggression words, high levels of verbal aggression would be the best predictor of bias for indirect aggression words, physical aggression would predict bias in males, and verbal aggression would predict bias in females. Males demonstrated a perceptual bias for words relating to acts of direct aggression, taking significantly longer to correctly colour name direct aggression words. Females were slower to correctly colour name indirect aggression words, but not significantly so. Verbal aggression, as expected, predicted bias performance for indirect aggression words but anger rather than physical aggression was the best predictor of bias for direct aggression words. Gender was a predictor for bias with both sets of words. Contrary to our predictions, it was observed that a high level of physical aggression was the best predictor of bias in both males and females. These data provide further evidence to confirm the saliency of aggression words to aggressive individuals in non‐forensic populations. Aggress. Behav. 00:00–00, 2005. © 2005 Wiley‐Liss, Inc.     

Defining face perception areas in the human brain: a large-scale factorial fMRI face localizer analysis

A number of human brain areas showing a larger response to faces than to objects from different categories, or to scrambled faces, have been identified in neuroimaging studies. Depending on the statistical criteria used, the set of areas can be overextended or minimized, both at the local (size of areas) and global (number of areas) levels. Here we analyzed a whole-brain factorial functional localizer obtained in a large sample of right-handed participants (40). Faces (F), objects (O; cars) and their phase-scrambled counterparts (SF, SO) were presented in a block design during a one-back task that was well matched for difficulty across conditions. A conjunction contrast at the group level {(F-SF) and (F-O)} identified six clusters: in the pulvinar, inferior occipital gyrus (so-called OFA), middle fusiform gyrus (so-called FFA), posterior superior temporal sulcus, amygdala, and anterior infero-temporal cortex, which were all strongly right lateralized. While the FFA showed the largest difference between faces and cars, it also showed the least face-selective response, responding more to cars than scrambled cars. Moreover, the FFA's larger response to scrambled faces than scrambled cars suggests that its face-sensitivity is partly due to low-level visual cues. In contrast, the pattern of activation in the OFA points to a higher degree of face-selectivity. A BOLD latency mapping analysis suggests that face-sensitivity emerges first in the right FFA, as compared to all other areas. Individual brain analyses support these observations, but also highlight the large amount of interindividual variability in terms of number, height, extent and localization of the areas responding preferentially to faces in the human ventral occipito-temporal cortex. This observation emphasizes the need to rely on different statistical thresholds across the whole brain and across individuals to define these areas, but also raises some concerns regarding any objective labeling of these areas to make them correspond across individual brains. This large-scale analysis helps understanding the set of face-sensitive areas in the human brain, and encourages in-depth single participant analyses in which the whole set of areas is considered in each individual brain.     

Attentional control in the aging brain: insights from an fMRI study of the stroop task

Several recent studies of aging and cognition have attributed decreases in the efficiency of working memory processes to possible declines in attentional control, the mechanism(s) by which the brain attempts to limit its processing to that of task-relevant information. Here we used fMRI measures of neural activity during performance of the color-word Stroop task to compare the neural substrates of attentional control in younger (ages: 21-27 years old) and older participants (ages: 60-75 years old) during conditions of both increased competition (incongruent and congruent neutral) and increased conflict (incongruent and congruent neutral). We found evidence of age-related decreases in the responsiveness of structures thought to support attentional control (e.g., dorsolateral prefrontal and parietal cortices), suggesting possible impairments in the implementation of attentional control in older participants. Consistent with this notion, older participants exhibited more extensive activation of ventral visual processing regions (i.e., temporal cortex) and anterior inferior prefrontal cortices, reflecting a decreased ability to inhibit the processing of task-irrelevant information. Also, the anterior cingulate cortex, a region involved in evaluatory processes at the level of response (e.g., detecting potential for error), showed age-related increases in its sensitivity to the presence of competing color information. These findings are discussed in terms of newly emerging models of attentional control in the human brain.     

A sensitive period for language in the visual cortex: distinct patterns of plasticity in congenitally versus late blind adults

Recent evidence suggests that blindness enables visual circuits to contribute to language processing. We examined whether this dramatic functional plasticity has a sensitive period. BOLD fMRI signal was measured in congenitally blind, late blind (blindness onset 9-years-old or later) and sighted participants while they performed a sentence comprehension task. In a control condition, participants listened to backwards speech and made match/non-match to sample judgments. In both congenitally and late blind participants BOLD signal increased in bilateral foveal-pericalcarine cortex during response preparation, irrespective of whether the stimulus was a sentence or backwards speech. However, left occipital areas (pericalcarine, extrastriate, fusiform and lateral) responded more to sentences than backwards speech only in congenitally blind people. We conclude that age of blindness onset constrains the non-visual functions of occipital cortex: while plasticity is present in both congenitally and late blind individuals, recruitment of visual circuits for language depends on blindness during childhood.     

Thinking about seeing: Perceptual sources of knowledge are encoded in the theory of mind brain regions of sighted and blind adults

Blind people’s inferences about how other people see provide a window into fundamental questions about the human capacity to think about one another’s thoughts. By working with blind individuals, we can ask both what kinds of representations people form about others’ minds, and how much these representations depend on the observer having had similar mental states themselves. Thinking about others’ mental states depends on a specific group of brain regions, including the right temporo-parietal junction (RTPJ). We investigated the representations of others’ mental states in these brain regions, using multivoxel pattern analyses (MVPA). We found that, first, in the RTPJ of sighted adults, the pattern of neural response distinguished the source of the mental state (did the protagonist see or hear something?) but not the valence (did the protagonist feel good or bad?). Second, these neural representations were preserved in congenitally blind adults. These results suggest that the temporo-parietal junction contains explicit, abstract representations of features of others’ mental states, including the perceptual source. The persistence of these representations in congenitally blind adults, who have no first-person experience with sight, provides evidence that these representations emerge even in the absence of relevant first-person perceptual experiences.     

A brief review on the use of functional near-infrared spectroscopy (fNIRS) for language imaging studies in human newborns and adults

Upon stimulation, real time maps of cortical hemodynamic responses can be obtained by non-invasive functional near-infrared spectroscopy (fNIRS) which measures changes in oxygenated and deoxygenated hemoglobin after positioning multiple sources and detectors over the human scalp. The current commercially available transportable fNIRS systems have a time resolution of 1-10 Hz, a depth sensitivity of about 1.5 cm, and a spatial resolution of about 1 cm. The goal of this brief review is to report infants, children and adults fNIRS language studies. Since 1998, 60 studies have been published on cortical activation in the brain’s classic language areas in children/adults as well as newborns using fNIRS instrumentations of different complexity. In addition, the basic principles of fNIRS including features, strengths, advantages, and limitations are summarized in terms that can be understood even by non specialists. Future prospects of fNIRS in the field of language processing imaging are highlighted.