Crossed Aphasia in a Dextral: A Test of the Alexander–Annett Theory of Anomalous Organization of Brain Function

A case of crossed aphasia is presented in a strongly right-handed 77-year-old white female without history of familial sinistrality or prior neurological illness. She developed a right middle cerebral artery infarction documented by CT and accompanied by obvious clinical signs of a conduction aphasia with some resolution but continuing obvious language defect after 9 weeks in rehabilitation. Comprehensive neuropsychological and aphasia testing suggested anomalous lateralization of phonologic-output aspects of language, emotional prosody, motor planning and body schema modules with usual lateralization of lexical–semantic aspects of language and visuo-spatial functions. Experimental validation of the uncrossed lexical–semantic aspects of language using tachistoscope methods found support for the Alexander–Annett theory that different aspects of language can be dissociated in their lateralization. The subject had difficulty identifying a semantic associate of a picture presented to the left visual field (7 errors out of 10) relative to right visual field presentation (2 errors out of 10). Bilateral free naming errors (6 and 5 errors in the left and right visual fields, respectively) occurred consistent with the aphasic presentation, suggesting phonologic-output dysfunction from the right cerebral vascular accident. Implications of the results for aphasia classification are discussed.     

Individual differences in language lateralisation,schizotypy and the remote-associate task

We tested the hypothesis that the level of reduced laterality in language is correlated with the degrees of schizotypal personality in healthy individuals and with their performance in the remote-associate task (RAT). A total of 53 healthy participants completed a schizotypal personality measure of the Oxford-Liverpool Inventory of Feelings and Experiences (O-LIFE; a questionnaire measuring the level of psychotic proneness), a consonant–vowel–consonant (CVC; requiring the identification of letter trigrams presented tachistoscopically in the left/right visual fields or both), measuring reduced language laterality and a remote-associate task (RAT; requiring to report a word, weakly associated with three cue words). Analysis revealed correlations between CVC and O-LIFE, as well as between CVC and RAT performance. The results suggest that reduced language lateralisation (reduced hemispheric integration) may play a role in schizophrenic language disorganization, as reflected in highly schizotypal individuals, and that hemispheric integration plays a role in the remote-associate task.     

Attention and hemispheric differences in reaction time during simultaneous audio-visual tasks

The effect of different types of competing auditory tasks on laterality differences in visual perception was investigated. Right-handed subjects were presented with digits which occurred randomly in the left or right visual fields. They responded vocally to previously specified digits in a go, no-go reaction time situation. In the absence of any competing auditory task, digits presented in the right visual field were processed more quickly. This visual field difference in reaction time was in the same direction while subjects performed a secondary musical task. However, when a secondary verbal task had to be performed, digits in the left visual field received faster responses. The results support the view that the right hemisphere is capable of some language functions, and that hemispheric differences in performance have at their basis a quantitative asymmetry, which can be reversed even in normal subjects by overloading their limited capacity.     

Response inhibition in the parametric go/no-go task and its relation to impulsivity and subclinical psychopathy

The current study utilizes the parametric go/no-go task (PGNG), a task that examines changes in inhibitory performance as executive function load increases, to examine the link between psychopathic traits, impulsivity, and response inhibition in a cohort of healthy participants. The results show that as executive function load increased, inhibitory ability decreased. High scores on the Cognitive Complexity subscale of the Barratt Impulsivity Scale (BIS–11) predict poor inhibitory ability in the PGNG. Similarly, high scores on the Psychopathy Personality Inventory–Revised (PPI–R) Blame Externalization subscale predict response inhibition deficits in the PGNG, which loads more on the executive functions than the standard go/no-go task. The remaining BIS–11 as well as PPI–R subscales did not interact with inhibitory performance in the PGNG highlighting the specificity of associations between aspects of personality and impulsivity with inhibitory performance as cognitive load is increased. These data point towards the sensitivity of the PGNG in studying response inhibition in the context of highly impulsive populations and its utility as a measure of impulsivity.     

Predicting cognitive control from preschool to late adolescence and young adulthood

In this longitudinal study, the proportion of time preschoolers directed their attention away from rewarding stimuli during a delay-of-gratification task was positively associated with efficiency (greater speed without reduced accuracy) at responding to targets in a go/no-go task more than 10 years later. The overall findings suggest that preschoolers' ability to effectively direct their attention away from tempting aspects of the rewards in a delay-of-gratification task may be a developmental precursor for the ability to perform inhibitory tasks such as the go/no-go task years later. Because performance on the go/no-go task has previously been characterized as involving activation of fronto-striatal regions, the present findings also suggest that performance in the delay-of-gratification task may serve as an early marker of individual differences in the functional integrity of this circuitry.     

The content of the message influences the hand choice in co-speech gestures and in gesturing without speaking

The present study investigates the hand choice in iconic gestures that accompany speech. In 10 right-handed subjects gestures were elicited by verbal narration and by silent gestural demonstrations of animations with two moving objects. In both conditions, the left-hand was used as often as the right-hand to display iconic gestures. The choice of the right- or left-hands was determined by semantic aspects of the message. The influence of hemispheric language lateralization on the hand choice in co-speech gestures appeared to be minor. Instead, speaking seemed to induce a sequential organization of the iconic gestures.     

Atypical speech lateralization in adults with developmental coordination disorder demonstrated using functional transcranial Doppler ultrasound

Research using clinical populations to explore the relationship between hemispheric speech lateralization and handedness has focused on individuals with speech and language disorders, such as dyslexia or specific language impairment (SLI). Such work reveals atypical patterns of cerebral lateralization and handedness in these groups compared to controls. There are few studies that examine this relationship in people with motor coordination impairments but without speech or reading deficits, which is a surprising omission given the prevalence of theories suggesting a common neural network underlying both functions. We use an emerging imaging technique in cognitive neuroscience; functional transcranial Doppler (fTCD) ultrasound, to assess whether individuals with developmental coordination disorder (DCD) display reduced left‐hemisphere lateralization for speech production compared to control participants. Twelve adult control participants and 12 adults with DCD, but no other developmental/cognitive impairments, performed a word‐generation task whilst undergoing fTCD imaging to establish a hemispheric lateralization index for speech production. All participants also completed an electronic peg‐moving task to determine hand skill. As predicted, the DCD group showed a significantly reduced left lateralization pattern for the speech production task compared to controls. Performance on the motor skill task showed a clear preference for the dominant hand across both groups; however, the DCD group mean movement times were significantly higher for the non‐dominant hand. This is the first study of its kind to assess hand skill and speech lateralization in DCD. The results reveal a reduced leftwards asymmetry for speech and a slower motor performance. This fits alongside previous work showing atypical cerebral lateralization in DCD for other cognitive processes (e.g., executive function and short‐term memory) and thus speaks to debates on theories of the links between motor control and language production.     

Cerebral lateralization of language in deaf and hearing people

In Experiment 1 neither hearing nor prelingually deaf signing adolescents showed marked lateralization for lexical decision but, unlike the hearing, the deaf were not impaired by the introduction of pseudohomophones. In Experiment 2 semantic categorization produced a left hemisphere advantage in the hearing for words but not pictures whereas in the deaf words and signs but not pictures showed a right hemisphere advantage. In Experiment 3 the lexical decision and semantic categorization findings were confirmed and both groups showed a right hemisphere advantage for a face/nonface decision task. The possible effect of initial language acquisition on the development of hemispheric lateralization for language is discussed.     

Task difficulty modulates brain-behavior correlations in language production and cognitive control: Behavioral and fMRI evidence from a phonological go/no-go picture-naming paradigm

Language production and cognitive control are complex processes that involve distinct yet interacting brain networks. However, the extent to which these processes interact and their neural bases have not been thoroughly examined. Here, we investigated the neural and behavioral bases of language production and cognitive control via a phonological go/no-go picture-naming task. Naming difficulty and cognitive control demands (i.e., conflict monitoring and response inhibition) were manipulated by varying the proportion of naming trials (go trials) and inhibition trials (no-go trials) across task runs. The results demonstrated that as task demands increased, participants’ behavioral performance declined (i.e., longer reaction times on naming trials, more commission errors on inhibition trials) whereas brain activation generally increased. Increased activation was found not only within the language network but also in domain-general control regions. Additionally, right superior and inferior frontal and left supramarginal gyri were sensitive to increased task difficulty during both language production and response inhibition. We also found both positive and negative brain–behavior correlations. Most notably, increased activation in sensorimotor regions, such as precentral and postcentral gyri, was associated with better behavioral performance, in both successful picture naming and successful inhibition. Moreover, comparing the strength of correlations across conditions indicated that the brain–behavior correlations in sensorimotor regions that were associated with improved performance became stronger as task demands increased. Overall, our results suggest that cognitive control demands affect language production, and that successfully coping with increases in task difficulty relies on both language-specific and domain-general cognitive control regions.     

The effect of semantic distance in yes/no and go/no-go semantic categorization tasks

The effect of semantic distance (Lund & Burgess, 1996) was examined in three semantic categorization experiments. Experiment 1, a yes/no task that required participants to make animal/nonanimal judgments by responding to both sets of stimuli (Forster & Shen, 1996), revealed no effect of semantic distance. Experiment 2, a go/no-go task that required participants to respond to only the experimental (i.e., nonanimal) items, revealed a large effect of semantic distance. In addition, response latencies were longer and error rates were lower to the experimental items in Experiment 2 than to those in Experiment 1. These findings were replicated in Experiment 3, in which semantic distance and task condition were manipulated within subjects. We conclude that these results are consistent with (1) the view that the go/no-go tasks elicited more extensive processing of the experimental items and (2) a connectionist account of semantic activation, whereby processing is facilitated by the presence of semantic neighbors.     

Developmental fractionation of working memory and response inhibition during childhood

The lateral prefrontal cortex (LPFC) plays a major role in both working memory (WM) and response inhibition (RI), which are fundamental for various cognitive abilities. We explored the relationship between these LPFC functions during childhood development by examining the performance of two groups of children in visuospatial and auditory WM tasks and a go/no-go RI task. In the younger children (59 5- and 6-year-olds), performance on the visuospatial WM task correlated significantly with that in the auditory WM task. Furthermore, accuracy in these tasks correlated significantly with performance on the RI task, particularly in the no-go trials. In contrast, there were no significant correlations among those tasks in older children (92 8- and 9-year-olds). These results suggest that functional neural systems for visuospatial WM, auditory WM, and RI, especially those in the LPFC, become fractionated during childhood, thereby enabling more efficient processing of these critical cognitive functions.     

Elimination of the enhanced Simon effect for older adults in a three-choice situation: Ageing and the Simon effect in a go/no-go Simon task

In a Simon task, participants show better performance when the irrelevant stimulus location corresponds with the response location than when it does not, and this effect is typically greater for older adults than for younger adults. To study the effect of cognitive ageing in the Simon task, we compared young and old adults using two versions of the Simon task: (a) a standard visual Simon task, for which participants respond with left and right key-presses to the red and green colours of stimuli presented in left and right locations; (b) a go/no-go version of the Simon task, which was basically the same, except that the shape of the stimulus in one third of the trials indicates that no response is to be made. In both tasks, both age groups showed the Simon effect. The magnitude of the effect for the standard Simon task was greater for the older adults than for the younger adults. Nevertheless, the two groups showed an equivalent Simon effect in the go/no-go version of the Simon task. Reaction time distribution analyses revealed basically similar functions for both age groups: a decreasing pattern of the Simon effect in the standard task and an increasing pattern of the effect in the go/no-go version of the task. The results suggest that older adults find it more difficult to suppress an automatic activation of the corresponding response, though this automatic activation was reduced in situations where the response was frequently inhibited.     

Response inhibition in adults and teenagers: spatiotemporal differences in the prefrontal cortex

Inhibition is a core executive function reliant on the frontal lobes that shows protracted maturation through to adulthood. We investigated the spatiotemporal characteristics of response inhibition during a visual go/no-go task in 14 teenagers and 14 adults using magnetoencephalography (MEG) and a contrast between two no-go experimental conditions designed to eliminate a common confound in earlier studies comparing go with no-go trials. Source analyses were performed using an event-related beamformer algorithm with co-registered individual structural MRIs. Performance was controlled to be similar across subjects. Analyses of MEG data revealed bilateral prefrontal activity in the inhibitory condition for both age groups, but with different spatiotemporal patterns: around 300ms after stimulus onset in middle frontal gyri in teenagers vs. around 260ms in inferior frontal gyri in adults. Moreover, the inhibition of a prepotent motor response showed a stronger recruitment of the left hemisphere in teenagers than in adults and of the right hemisphere in adults than in teenagers. These findings provide high-resolution temporal and spatial information regarding response inhibition in adolescents compared to adults, independent of motor components and performance differences.     

The role of the prefrontal cortex in the go/no-go task in humans: a positron emission tomography study

To study the localization of response inhibition in the human brain, especially the role of the prefrontal cortex and laterality of its activation, we used positron emission tomography (PET) to measure regional cerebral blood flow in 11 right-handed participants while they performed a go/no-go and a simple control reaction-time task. In the control task, the participants responded to a target stimulus following a cue stimulus. In the go/no-go task they were instructed to inhibit the required response if the target stimulus did not appear. These tasks were performed using each hand. The right prefrontal cortex was found to be significantly activated when the go/no-go task was compared with the control task, regardless of the responding hand. The results indicated that response inhibition per se may be controlled by the right prefrontal cortex regardless of response hand for right-handed participants.     

Lateralisation of language and emotion in schizotypal personality: Evidence from dichotic listening

Striking disturbances have been reported in language and emotional prosody processing by patients diagnosed with schizophrenia. In view of this and of research suggesting that schizotypal personality traits can also be expressed sub-clinically, the present study aimed to discover whether similar disturbances would be reflected in cognitive laterality patterns when symptoms of schizotypy are present yet at a non-clinical level. A dichotic listening task was used to examine the sensitivity and speed with which 132 right-handed participants (85 females and 47 males, mean age = 32.44, SD = 12.29) detected both words and emotional prosody, all of whom also completed the Schizotypal Personality Questionnaire. Findings indicated that both high (n = 64) and low (n = 68) schizotypy groups demonstrated the typical right ear advantage for the detection of words and left ear advantage for the detection of emotional prosody. Individuals with higher schizotypal personality scores also demonstrated poorer sensitivity in detecting emotional prosody. These results reveal that within the healthy population, higher levels of schizotypy are not associated with the atypical lateralisation of language and emotion. Nevertheless, the existence of these symptoms does signal the presence of shared characteristics with the clinical sphere, namely poorer emotion recognition performance.     

The N2 in go/no-go tasks reflects conflict monitoring not response inhibition

The functional significance of the N2 in go/no-go tasks was investigated by comparing electrophysiological data obtained from two tasks: a go/no-go task involving both response inhibition as well as response conflict monitoring, and a go/GO task associated with conflict monitoring only. No response was required to no-go stimuli, and a response with maximal force to GO stimuli. The relative frequency of the go stimuli (80% vs. 50%) was varied. The N2 peaked on both no-go and GO trials, with larger amplitudes for both signals when presented in a context of frequent (80%) go signals. These results support the idea that the N2 reflects conflict monitoring not response inhibition.     

Trait impulsivity and callous-unemotional traits as predictors of inhibitory control and risky choices among high-risk adolescents

Trait impulsivity and callous-unemotional traits are associated with behavioural problems among high-risk adolescents. While both are known to influence behaviour, the nature of their expression in high-risk behaviours, particularly those related to inhibitory control, is not well understood. In the current, preliminary study, we examined whether and how these traits predicted deficits in behaviour driven by bottom-up, automatic versus deliberate, top-down inhibitory processes among high-risk adolescents. Two go/no-go task variants, emotional and non-emotional, were used to assess reactive response inhibition, and the Balloon Analogue Risk Task was used to assess the ability to resist deliberate risky choices. The results showed that the two types of self-reported trait measures were differentially associated with performance on the two types of behavioural inhibition tasks. Trait impulsivity predicted non-emotional inhibitory control whereas callous-unemotional traits predicted risky choices. The results also showed that the emotions task elicited slower reaction times and higher false alarm rates than did the letters task, and that participants had greater difficulty inhibiting responses to negatively than to positively valenced no-go stimuli. While preliminary, the results suggest that the interplay between trait impulsivity and callous-unemotional traits is an important determinant of inhibitory behaviour in this high-risk adolescents.     

Relationship between schizotypal and borderline traits in college students

The main objective of the present investigation was to analyze the relationship between self-reported schizotypal and borderline personality traits in a sample of 759 college students (M = 19.63 years; SD = 2.03). For this purpose, the Schizotypal Personality Questionnaire-Brief (SPQ-B; Raine and Benishay, 1995) and Borderline Personality Questionnaire (BPQ; Poreh et al., 2006) were administered. The results showed that schizotypal and borderline features are partially related at subclinical level. The exploratory factor analysis conducted on the subscales revealed a three-factor solution comprised of the following factors: Identity/Interpersonal, Lack of Control and Schizotypal. The canonical correlation analysis showed that schizotypal features and borderline personality traits shared 34.8% of the variance. The data highlight the overlap between schizotypal and borderline personality traits in nonclinical young adults. Future studies should continue to examine the relationship and the degree of overlap between these traits in community samples.     

Transfer of response codes from choice-response to go/no-go tasks

The present study investigated the conditions for observing the Simon effect in go/no-go tasks. The Simon effect denotes faster and more accurate responses when irrelevant stimulus location and response location correspond than when they do not correspond. In four experiments, participants performed both in a choice-response task (CRT) and in a go/no-go task, and we varied the order and the similarity of the tasks. In the CRT, participants pressed a left key to one stimulus colour and a right key to another stimulus colour; in the go/no-go task, participants pressed one (e.g., left) key to one stimulus colour and refrained from responding to the other stimulus colour. As expected, Simon effects were consistently observed in the CRT. In contrast, Simon effects in the go/no-go task were only observed when it followed the CRT and when the mapping of stimulus colours to response locations was preserved between tasks (i.e., in Experiment 4). Results suggest that transfer of a particular S–R rule including response location from the CRT to the go/no-go task was responsible for the Simon effect in the latter task. In general, results are consistent with a response-discrimination account of the Simon effect.     

Unequal motor durations under simple-, go/no-go, and choice-RT tasks: extension of Miller and Low (2001)

The logic of the Subtraction Method is used implicitly or explicitly in a variety of work, ranging from traditional response-time research to functional neuroimaging. One assumption of all forms of the Subtraction Method is that components may be inserted (or deleted) without causing changes in the remaining components. We tested this assumption as it applies to the duration of late motor processing using the lag between the onset of lateralized readiness potential (LRP) and the production of the required response as the measure of late motor processing. In contrast to a similar, previous study that used this approach (Miller & Low, 2001), we found differences in the LRP lags across the types of task that are used in the Subtraction Method. The LRP lag for simple-RT was shorter than the lags for either go/no-go or choice-RT. This finding constitutes evidence against an assumption required by the Subtraction Method, at least as applied to component durations, but can be explained in terms of a supplementary (non-subtractive) inhibitory component that is only employed in the go/no-go task.