Development of attentional allocation in the dual task paradigm

Effects of age and sex on developmental neural networks of visual-spatial attention allocation

Compared to our understanding of the functional maturation of brain networks underlying complex cognitive abilities, hardly anything is known of the neurofunctional development of simpler cognitive abilities such as visuo-spatial attention allocation. Furthermore, nothing is known on the effect of gender on the functional development of attention allocation. This study employed event related functional magnetic resonance imaging to investigate effects of age, sex, and sex by age interactions on the brain activation of 63 males and females, between 13 to 38years, during a visual-spatial oddball task. Behaviourally, with increasing age, speed was traded for accuracy, indicative of a less impulsive performance style in older subjects. Increasing age was associated with progressively increased activation in typical areas of selective attention of lateral fronto-striatal and temporo-parietal brain regions. Sex difference analysis showed enhanced activation in right-hemispheric inferior frontal and superior temporal regions in females, and in left-hemispheric inferior temporo-parietal regions in males. Importantly, the age by sex interaction findings showed that these sex-dimorphic patterns of brain activation may be the result of underlying sex differences in the functional maturation of these brain regions, as females had sex-specific progressive age-correlations in the same right inferior fronto-striato-temporal areas, while male-specific age-correlations were in left medial temporal and parietal areas. The findings demonstrate progressive functional maturation of fronto-striato-parieto-temporal networks of the relatively simple function of attention allocation between early adolescence and mid-adulthood. They furthermore show that sex-dimorphic patterns of enhanced reliance on right inferior frontal, striatal and superior temporal regions in females and of left temporo-parietal regions in males during attention allocation may be the result of underlying sex differences in the functional maturation of these brain regions.

Working memory and specific language impairment: an update on the relation and perspectives on assessment and treatment

PURPOSE

Children with specific language impairment (SLI) demonstrate significant language impairments despite normal-range hearing and nonverbal IQ. Many of these children also show marked deficits in working memory (WM) abilities. However, the theoretical and clinical characterization of the association between WM and language limitations in SLI is still sparse. Our understanding of this association would benefit greatly from an updated and thorough review of the literature.

METHOD

We review the newest developments in these areas from both a theoretical and clinical perspective. Our intent is to provide researchers and practicing clinicians (a) a conceptual framework within which the association between WM and language limitations of children with SLI can be understood and (b) potentially helpful suggestions for assessing and treating the memory-language difficulties of children with SLI.

CONCLUSIONS

In the past 10 years, important new theoretical insights into the range and nature of WM deficits and relation between these limitations and the language difficulties in SLI have occurred. New, robust diagnostic assessment tools and computerized treatment methods designed to enhance children's WM functioning have also been developed. The assessment, diagnosis, and treatment of the language difficulties in SLI should consider the potential influence of WM.

Infant cognition: going full factorial with pupil dilation

The violation-of-expectation (VOE) paradigm and related methods are the main tools used to study high-level cognition in preverbal infants. Infants' differential looking to conceptually implausible/impossible events has been used as an index of early cognitive competence in many areas, including object knowledge, physics, language, and number. However, an event's plausibility is commonly confounded with its perceptual novelty or familiarity, leading to a variety of interpretations for looking time data (Bogartz, Shinskey & Speaker, 1997). This illustrative study demonstrates the value of factorial designs, in which perceptual (novelty-familiarity) and conceptual (possible-impossible) variables are independently and jointly explored. It also introduces pupil dilation as a viable and complementary dependent measure to study infant cognition. We show that pupil data can assist in the interpretation of otherwise equivocal looking time data. The discussion focuses on methodological considerations in infancy research.

Relation of three mechanisms of working memory to children’s complex span performance

There is a paucity of research examining the relative contribution of the different mechanisms of working memory (short-term storage [STM], processing speed) to children’s complex memory span. This study served to replicate and extend the few extant studies that have examined the issue. In this study, the relative contribution of three mechanisms of working memory — STM storage, processing speed, attentional resource allocation — to children’s complex span was examined. Children (6—12) completed a digit span task, an auditory-visual reaction time task, a task of attentional allocation, and a complex (listening) span task. Correlation analyses revealed that, after controlling for age, storage, processing speed, and attentional allocation significantly correlated with complex span. Regression analyses showed that, after partialling out age, storage accounted for 12.1% of unique variance in complex span and processing speed accounted for another 6.6% of unique variance; allocation contributed no unique variance. Consistent with the developmental literature, storage and general processing speed play critical roles in children’s complex span performance.

Regulation of cognitive resources during an n-back task in youth-onset psychosis and attention-deficit/hyperactivity disorder (ADHD)

The goals of the current study were to use behavioral and pupillary measures to examine working memory on a spatial n-back task in 8-20-year-olds with youth-onset psychosis or ADHD (Combined subtype) and healthy controls to determine the contribution of different attentional factors to spatial working memory impairments, and to examine if age-related changes in performance differed across groups. Although both clinical groups had lower perceptual sensitivity on both 0- and 1-back, there was no evidence of an impairment in spatial working memory or differential order effects on the 0-back. Instead, results suggest that both clinical groups had difficulty encoding the stimuli. They also appeared to have difficulty maintaining attention and/or readiness to respond, and, to a lesser extent, recruiting resources on a trial-to-trial basis. It is likely that these attentional problems prevented the clinical groups from encoding the stimuli effectively and contributed to their general performance deficits.

Development of eye-movement control

Cognitive control of behavior continues to improve through adolescence in parallel with important brain maturational processes including synaptic pruning and myelination, which allow for efficient neuronal computations and the functional integration of widely distributed circuitries supporting top-down control of behavior. This is also a time when psychiatric disorders, such as schizophrenia and mood disorders, emerge reflecting a particularly vulnerability to impairments in development during adolescence. Oculomotor studies provide a unique neuroscientific approach to make precise associations between cognitive control and brain circuitry during development that can inform us of impaired systems in psychopathology. In this review, we first describe the development of pursuit, fixation, and visually-guided saccadic eye movements, which collectively indicate early maturation of basic sensorimotor processes supporting reflexive, exogenously-driven eye movements. We then describe the literature on the development of the cognitive control of eye movements as reflected in the ability to inhibit a prepotent eye movement in the antisaccade task, as well as making an eye movement guided by on-line spatial information in working memory in the oculomotor delayed response task. Results indicate that the ability to make eye movements in a voluntary fashion driven by endogenous plans shows a protracted development into adolescence. Characterizing the transition through adolescence to adult-level cognitive control of behavior can inform models aimed at understanding the neurodevelopmental basis of psychiatric disorders.

Attentional modulation of word recognition by children in a dual-task paradigm

PURPOSE

This study investigated an account of limited short-term memory capacity for children's speech perception in noise using a dual-task paradigm.

METHOD

Sixty-four normal-hearing children (7-14 years of age) participated in this study. Dual tasks were repeating monosyllabic words presented in noise at 8 dB signal-to-noise ratio and rehearsing sets of 3 or 5 digits for subsequent serial recall. Half of the children were told to allocate their primary attention to word repetition and the other half to remembering digits. Dual-task performance was compared to single-task performance. Limitations in short-term memory demands required for the primary task were measured by dual-task decrements in nonprimary tasks.

RESULTS

Results revealed that (a) regardless of task priority, no dual-task decrements were found for word recognition, but significant dual-task decrements were found for digit recall; (b) most children did not show the ability to allocate attention preferentially to primary tasks; and (c) younger children (7- to 10-year-olds) demonstrated improved word recognition in the dual-task conditions relative to their single-task performance.

CONCLUSIONS

Seven- to 8-year-old children showed the greatest improvement in word recognition at the expense of the greatest decrement in digit recall during dual tasks. Several possibilities for improved word recognition in the dual-task conditions are discussed.

The coupling of emotion and cognition in the eye: Introducing the pupil old/new effect

The study presented here investigated the effects of emotional valence on the memory for words by assessing both memory performance and pupillary responses during a recognition memory task. Participants had to make speeded judgments on whether a word presented in the test phase of the experiment had already been presented ("old") or not ("new"). An emotion-induced recognition bias was observed: Words with emotional content not only produced a higher amount of hits, but also elicited more false alarms than neutral words. Further, we found a distinct pupil old/new effect characterized as an elevated pupillary response to hits as opposed to correct rejections. Interestingly, this pupil old/new effect was clearly diminished for emotional words. We therefore argue that the pupil old/new effect is not only able to mirror memory retrieval processes, but also reflects modulation by an emotion-induced recognition bias.

The effect of a concurrent task on the walking performance of preschool children

Forty-eight children, aged 4-6 years, walked while performing or not performing an easy or difficult concurrent motor task (carrying a tray with or without marbles on it) or cognitive task (repeating a series of digits forwards or backwards). The temporal-distance gait parameters were measured using a GAITRite electronic walkway system. Dual-task costs were calculated as the difference between the children's walking performances with and without the concurrent task. Overall, walking alone was easier than walking while performing a concurrent task. A greater dual-task cost was observed when the concurrent task was difficult compared to when it was easy. However, this effect of difficulty was found for the motor task only. The results suggest that walking demands both the central processing capacity and the domain- and modality-specific processing resources in normal 4-6-year-old children.

Effects of stimulus probability on pupillary dilation and reaction time in categorization

Stimuli presented with a low frequency elicit larger pupillary responses than those presented with a high frequency. Similar effects are known for motor responses observed in reaction time experiments. Utilizing this stimulus probability effect, we conducted a Go/NoGo reaction time experiment and measured pupillary dilation to evaluate categorization. We found no probability effect when participants used distinctive features to classify stimuli with different frequencies into the same category. If no distinctive features could be applied, however, the effect was observed in both pupillary and reaction time data. The stimulus probability effect can serve as a tool for the evaluation of categorization and is discussed in the context of orienting.

Regulation of cognitive resources during sustained attention and working memory in 10-year-olds and adults

We examined differences between 10-year-olds and young adults in resource recruitment and regulation during tasks of sustained attention and spatial working memory. We administered participants spatial 0- and 1-back tasks and used pupillary dilation as a measure of resource recruitment. Repeated administration of 0-back led to smaller pupillary dilations and greater response time (RT) variability, revealing a vigilance decrement. Effects of repeated administration of 0-back and differences between 0- and 1-back in d' and RTs were similar between ages. Results further suggested that the children may not have been as effective as adults in extracting frequency information. Thus, on simple tasks of sustained attention and working memory, children recruit resources in a manner similar to adults. Finally, d' was correlated with RT variability on both tasks at both ages, highlighting the role of attentional fluctuations on both tasks.

Tracking stimulus processing in Pavlovian pupillary conditioning

The aim of the present study was to evaluate whether the anticipatory pupillary dilation response is a useful indicator for the examination of complex differential conditioning problems like patterning. A human fear conditioning procedure with six groups (n=20 each) was used to examine conditioned stimulus (CS) processing when a compound stimulus was reinforced, but not its elements (positive patterning) or when the elements were reinforced, but not the compound (negative patterning), as well as modifications in which the compound was replaced by either a new compound or by a new element. We found evidence for conditioning within 2 s after CS onset. Group differences in differential conditioning indicated systematic differences in CS processing due to different discrimination task difficulties. This study showed that the pupil response is a suitable indicator for human Pavlovian conditioning with high time resolution within and between trials.

Neuropsychological performance in first-episode adolescents with schizophrenia: a comparison with first-episode adults and adolescent control subjects

BACKGROUND

The goal of this study was to compare the extent of cognitive deficits between adolescents and adults early in the course of schizophrenia.

METHODS

A comprehensive neuropsychological battery was performed on 49 adolescents with childhood- or adolescent-onset schizophrenia, 139 adults with adult-onset schizophrenia, 32 healthy adolescent volunteers, and 240 healthy adult volunteers. Both patient groups were assessed early in the course of their illness and were matched to their respective control groups on age and parental education.

RESULTS

The adolescent patients performed significantly worse than the adult patients on tasks of working memory, language, and motor function. The healthy adolescents also performed significantly worse than the healthy adults in working memory and language tasks but were significantly better than the adults in motor function. When accounting for developmental differences in the control group, only motor performance was worse in the adolescent patients compared with the adult patients.

CONCLUSIONS

These findings, when coupled with published retrospective studies reporting greater cognitive deficits in earlier onset schizophrenia, implicate a cessation in development in specific cognitive domains following the onset of schizophrenia in adolescent patients.

Executive “Brake Failure” following Deactivation of Human Frontal Lobe

In the course of daily living, humans frequently encounter situations in which a motor activity, once initiated, becomes unnecessary or inappropriate. Under such circumstances, the ability to inhibit motor responses can be of vital importance. Although the nature of response inhibition has been studied in psychology for several decades, its neural basis remains unclear. Using transcranial magnetic stimulation, we found that temporary deactivation of the pars opercularis in the right inferior frontal gyrus selectively impairs the ability to stop an initiated action. Critically, deactivation of the same region did not affect the ability to execute responses, nor did it influence physiological arousal. These findings confirm and extend recent reports that the inferior frontal gyrus is vital for mediating response inhibition.

The BOLD response during Stroop task-like inhibition paradigms: Effects of task difficulty and task-relevant modality

Previous studies of the Stroop task propose two key mediators: the prefrontal and cingulate cortices but hints exist of functional specialization within these regions. This study aimed to examine the effect of task modality upon the prefrontal and cingulate response by examining the response to colour, number, and shape Stroop tasks whilst BOLD fMRI images were acquired on a Siemens 3T MRI scanner. Behavioural analyses indicated facilitation and interference effects and a noticeable effect of task difficulty. Some modular effects of modality were observed in the prefrontal cortex that survived exclusion of task difficulty related activations. No effect of task-relevant information was observed in the anterior cingulate. Future comparisons of the mediation of selective attention need to consider the effects of task context and task difficulty.

Development of saccadic suppression in children

We measured saccadic suppression in adolescent children and young adults using spatially curtailed low spatial frequency stimuli. For both groups, sensitivity for color-modulated stimuli was unchanged during saccades. Sensitivity for luminance-modulated stimuli was greatly reduced during saccades in both groups but far more for adolescents than for young adults. Adults' suppression was on average a factor of about 3, whereas that for the adolescent group was closer to a factor of 10. The specificity of the suppression to luminance-modulated stimuli excludes generic explanations such as task difficulty and attention. We suggest that the enhanced suppression in adolescents results from the immaturity of the ocular-motor system at that age.

Sympathetic and parasympathetic innervation of pupillary dilation during sustained processing

The contributions of separate sympathetic and parasympathetic pathways to pupillary dilation during a sustained processing task were studied through environmental and pharmacological manipulations. In Experiment 1, 22 healthy volunteers (11 female) performed a serial Subtract 7 task while pupil diameter was recorded both during moderate room light and in darkness. In a control for verbalization, subjects performed an easier Add 1 task. In all conditions, pupil diameter increased significantly during the response period as compared to a pre-verbalization baseline period. Pupillary dilation was increased for the difficult task, and further increase in dilation was associated with recording in light. This suggests a major differential contribution to task difficulty mediated through inhibition of the parasympathetic pathway. In Experiment 2, a subgroup of 12 volunteers (seven female) repeated all conditions at three additional sessions in which one eye was instilled with tropicamide (to block the parasympathetic sphincter muscle), dapiprazole (to block the sympathetic dilator muscle) or placebo. All pharmacological conditions resulted in overall dilation during task performance. Differential performance similar to the placebo condition was seen only in the dapiprazole condition, when parasympathetic activation was intact. The findings suggest that sustained performance during a difficult task is modulated by cortical inhibition of the parasympathetic pathway at the oculomotor nucleus. Moreover, modulation of both ambient light intensity and pharmacological blockade of the final pupillary musculature were observed to provide converging approaches for quantifying the activity of identifiable central autonomic pathways.