Changes In Task Performance Research Articles

Understanding communicative actions: A repetitive TMS study

Despite the ambiguity inherent in human communication, people are remarkably efficient in establishing mutual understanding. Studying how people communicate in novel settings provides a window into the mechanisms supporting the human competence to rapidly generate and understand novel shared symbols, a fundamental property of human communication. Previous work indicates that the right posterior superior temporal sulcus (pSTS) is involved when people understand the intended meaning of novel communicative actions. Here, we set out to test whether normal functioning of this cerebral structure is required for understanding novel communicative actions using inhibitory low-frequency repetitive transcranial magnetic stimulation (rTMS). A factorial experimental design contrasted two tightly matched stimulation sites (right pSTS vs left MT+, i.e., a contiguous homotopic task-relevant region) and tasks (a communicative task vs a visual tracking task that used the same sequences of stimuli). Overall task performance was not affected by rTMS, whereas changes in task performance over time were disrupted according to TMS site and task combinations. Namely, rTMS over pSTS led to a diminished ability to improve action understanding on the basis of recent communicative history, while rTMS over MT+ perturbed improvement in visual tracking over trials. These findings qualify the contributions of the right pSTS to human communicative abilities, showing that this region might be necessary for incorporating previous knowledge, accumulated during interactions with a communicative partner, to constrain the inferential process that leads to action understanding.

Neural chronometry and coherency across speed–accuracy demands reveal lack of homomorphism between computational and neural mechanisms of evidence accumulation

The stochastic accumulation framework provides a mechanistic, quantitative account of perceptual decision-making and how task performance changes with experimental manipulations. Importantly, it provides an elegant account of the speed-accuracy trade-off (SAT), which has long been the litmus test for decision models, and also mimics the activity of single neurons in several key respects. Recently, we developed a paradigm whereby macaque monkeys trade speed for accuracy on cue during visual search task. Single-unit activity in frontal eye field (FEF) was not homomorphic with the architecture of models, demonstrating that stochastic accumulators are an incomplete description of neural activity under SAT. This paper summarizes and extends this work, further demonstrating that the SAT leads to extensive, widespread changes in brain activity never before predicted. We will begin by reviewing our recently published work that establishes how spiking activity in FEF accomplishes SAT. Next, we provide two important extensions of this work. First, we report a new chronometric analysis suggesting that increases in perceptual gain with speed stress are evident in FEF synaptic input, implicating afferent sensory-processing sources. Second, we report a new analysis demonstrating selective influence of SAT on frequency coupling between FEF neurons and local field potentials. None of these observations correspond to the mechanics of current accumulator models.

Changes in simple visual matching task performance and physiological signals in intellectually and developmentally disabled people due to administration of highly concentrated oxygen

This study attempted to identify the effect of administration of highly concentrated oxygen on simple visual matching task performance, blood oxygen saturation [SpO2 (%)], and heart rate [HR (bpm)] of intellectually and developmentally disabled people. Nineteen intellectually and developmentally disabled people (mean age 30.6 ± 5.7 years) participated in an experiment consisting of a simple visual matching task performed under 21% and 92% oxygen. SpO2 and HR were measured under both oxygen conditions. When 92% oxygen was supplied, the response time decreased, SpO2 increased, and HR decreased compared to the vales obtained using 21% oxygen. The response time decreased for subjects with a high SpO2 and HR during the simple visual matching task phase. This result supports the hypothesis that administration of highly concentrated oxygen can positively affect the cognitive performance of intellectually and developmentally disabled people.

Action Simulation Plays a Critical Role in Deceptive Action Recognition

The ability to infer deceptive intents from nonverbal behavior is critical for social interactions. By combining single-pulse and repetitive transcranial magnetic stimulation (TMS) in healthy humans, we provide both correlational and causative evidence that action simulation is actively involved in the ability to recognize deceptive body movements. We recorded motor-evoked potentials during a faked-action discrimination (FAD) task: participants watched videos of actors lifting a cube and judged whether the actors were trying to deceive them concerning the real weight of the cube. Seeing faked actions facilitated the observers' motor system more than truthful actions in a body-part-specific manner, suggesting that motor resonance was sensitive to deceptive movements. Furthermore, we found that TMS virtual lesion to the anterior node of the action observation network, namely the left inferior frontal cortex (IFC), reduced perceptual sensitivity in the FAD task. In contrast, no change in FAD task performance was found after virtual lesions to the left temporoparietal junction (control site). Moreover, virtual lesion to the IFC failed to affect performance in a difficulty-matched spatial-control task that did not require processing of spatiotemporal (acceleration) and configurational (limb displacement) features of seen actions, which are critical to detecting deceptive intent in the actions of others. These findings indicate that the human IFC is critical for recognizing deceptive body movements and suggest that FAD relies on the simulation of subtle changes in action kinematics within the motor system.

Age association of language task induced deactivation induced in a pediatric population

Task-induced deactivation (TID) potentially reflects the interactions between the default mode and task specific networks, which are assumed to be age dependent. The study of the age association of such interactions provides insight about the maturation of neural networks, and lays out the groundwork for evaluating abnormal development of neural networks in neurological disorders. The current study analyzed the deactivations induced by language tasks in 45 right-handed normal controls aging from 6 to 22 years of age. Converging results from GLM, dual regression and ROI analyses showed a gradual reduction in both the spatial extent and the strength of the TID in the DMN cortices as the brain matured from kindergarten to early adulthood in the absence of any significant change in task performance. The results may be ascribed to maturation leading to either improved multi-tasking (i.e. reduced deactivation) or reduced cognitive demands due to greater experience (affects both control and active tasks but leads to reduced overall difference). However, other effects, such as changes in the DMN connectivity that were not included in this study may also have influenced the results. In light of this, researchers should be cautious when investigating the maturation of DMN using TID. With a GLM analysis using the concatenated fMRI data from several paradigms, this study additionally identified an age associated increase of TID in the STG (bilateral), possibly reflecting the role of this area in speech perception and phonological processing.

Maintenance of Cognitive Control during and after Walking in Preadolescent Children

The present study evaluated the effects of an acute bout of moderate-intensity treadmill walking on aspects of cognitive control underlying successful academic achievement. The study used a within-subjects counterbalanced design with a sample of 36 preadolescent children. Cognitive performance was assessed using a modified flanker task and a modified spatial n-back task to assess inhibition and working memory, respectively. No changes in task performance were observed while individuals were actively walking or at seated rest across both tasks. However, during the flanker task, increased response accuracy was observed after exercise relative to post-seated rest. Further observation revealed decrements to response accuracy after seated rest relative to baseline. No such effect was observed for the n-back task. These findings suggest selective exercise-induced changes to cognitive control for aspects of inhibitory control and attention but not for working memory. Furthermore, the findings suggest that short bouts of exercise may be efficacious for maintaining cognitive performance, which may have implications for scholastic achievement.

Minimally supervised multimodal exercise to reduce falls risk in economically and educationally disadvantaged older adults.

Few studies have evaluated the benefit of providing exercise to underprivileged older adults at risk for falls. Economically and educationally disadvantaged older adults with previous falls (mean age 79.06, SD = 4.55) were randomized to 4 mo of multimodal exercise provided as fully supervised center-based (FS, n = 45), minimally supervised home-based (MS, n = 42), or to nonexercise controls (C, n = 32). Comparing groups on the mean change in fall-relevant mobility task performance between baseline and 4 mo and compared with the change in C, both FS and MS had significantly greater reduction in timed up-and-go, F(2,73) = 5.82, p = .004, η2 p = .14, and increase in tandem-walk speed, F(2,73) = 7.71, p < .001 η2 p = .17. Change in performance did not statistically differ between FS and MS. In community-dwelling economically and educationally disadvantaged older adults with a history of falls, minimally supervised home-based and fully supervised center-based exercise programs may be equally effective in improving fall-relevant functional mobility.

Effects of Font Size and Reflective Glare on Text-Based Task Performance and Postural Change Behavior of Presbyopic and Nonpresbyopic Computer Users

Nineteen young (18-35 year-old) and seven older presbyopic (55-65 year-old, wearing bifocal or progressive glasses) subjects with the same average visual acuity at near distance participated in this full-factorial, repeated measures study with two trial factors: font size (capital letter heights of 1.78, 2.23, and 3.56 mm) and reflective glare. The monitor location was fixed, but subjects were allowed to move their bodies and the chair while performing visually demanding tasks. The productivity improved up to 30% when using a large font size (average visual angle 23.4 arcmin) compared to a smaller font size (14.2 or 16.4 arcmin, p &lt; .0001). The relative contributions of torso flexion (78%), head forward (3%), and chair reposition (4%) to changes in the viewing distance remained constant across font size conditions. Reflective glare had no effect on productivity measures but led to reduction of viewing distance ( p &lt; .0001). There were no significant differences between the two age groups.

Knowing When to Move On

We investigated people’s ability to decide how much time to spend on the task at hand. To make such decisions well, one must take into account, among other things, the cost of failing and how one’s task performance changes as a function of time. We first investigated timing decisions when the underlying task was perceptual. Decisions were highly efficient and suggested that people can make good use of perceptual knowledge and abstract reward information. Previous studies have found that perceptual decisions are generally optimal, but that cognitive decisions are generally suboptimal—a perception-cognition gap. Does a similar gap exist for timing decisions? We compared timing decisions for a perceptual task with timing decisions for more cognitive tasks. Performance was highly similar across the tasks, which suggests that knowledge can be acquired, and used to make timing decisions, in an equally efficient way regardless of whether that knowledge is derived through perceptual or cognitive experience.

Optimal Timing of Rehabilitation: Overview of the Evidence in the Literature

Stroke results in chronic disability which is a major burden in various ways and thus regaining functional independence is an important goal for the stroke patients and caregivers. Early rehabilitative training after stroke onset takes place in most stroke centers. However, optimal timing of rehabilitation after stroke remains controversial and debate on the complications and other issues induced by the early rehabilitation is still ongoing despite considerable amount evidence in the literature that supports early rehabilitation. There is uncertainty about whether very early mobilization within 24 to 48 hours of stroke onset improves outcome after stroke. Emphasis on early mobilization with increasing frequency and dose of mobilization in the early phase of stroke may contribute to improved functional outcomes after stroke. In this article, superiority of the very early mobilization after stroke is demonstrated by reviewing supporting evidence from animal studies by showing changes in task performance and anatomy, clinical comparative data by comparing outcome measurement scores, AVERT studies, a large scale randomized controlled trial currently in progress to provide sufficient clinical evidence, and the current Clinical Practice Guidelines. (Brain & NeuroRehabilitation 2012; 5: 1-5)

Stimulus onsets and distraction in younger and older adults.

Changes in task performance that accompany healthy aging are often attributed to age-impaired inhibitory control. For example, Maylor and Lavie (1998) demonstrated greater interference in older than younger people for response-incompatible visual distractors presented peripherally to a central low-load task. Here we explore the possible contribution of age-related changes in bottom-up visual processing in this task, and specifically the effect of the abrupt visual onsets associated with the distractors. In Experiment 1, with distractors presented as abrupt onsets, we replicated Maylor and Lavie's (1998) effect. In Experiment 2, when placeholders preceded the stimuli to eliminate the abrupt onsets, response-incompatible distractors had a markedly reduced effect relative to neutral distractors, for older participants in particular. Stimuli presented as abrupt visual onsets, therefore, capture attention differentially depending upon the stimulus identity in combination with the age of the individual, with the greatest effects here for response-incompatible distractors in older people. We conclude that age-related differences in basic bottom-up processes may contribute to many purported declines in higher-level functioning in older people. More generally, this study provides further evidence for the interaction, and nonadditivity, of stimulus-driven and goal-driven influences in determining processing priorities across the age span.

Neuronal correlates of reduced memory performance in overweight subjects

There is growing evidence that excessive body weight correlates with impaired cognitive performance like executive function, attention and memory. In our study, we applied a visual working memory task to quantify associations between body weight and executive function. In total, 34 lean (BMI 22±2.1 kg/m(2)) and 34 obese (BMI 30.4±3.2 kg/m(2)) subjects were included. Magnetic brain activity and behavioral responses were recorded during a one-back visual memory task with food and non-food pictures, which were matched for color, size and complexity. Behavioral responses (reaction time and accuracy) were reduced in obese subjects independent of the stimulus category. Neuronal activity at the source level showed a positive correlation between the right dorsolateral prefrontal cortex (DLPFC) activity and BMI only for the food category. In addition, a negative correlation between BMI and neuronal activity was observed in the occipital area for both categories. Therefore we conclude that increased body weight is associated with reduced task performance and specific neuronal changes. This altered activity is probably related to executive function as well as encoding and retrieval of information.

Dual-task repetition alters event-related brain potentials and task performance

ObjectiveWe examined the modulation of event-related brain potentials (ERPs) and the accuracy of sensori-motor coordination on short-term repetition of the concurrent performance of a somatosensory discrimination (oddball) task and a visuo-motor tracking task. MethodsThe subjects concurrently performed visuomotor tracking and somatosensory oddball tasks. In the dual-task condition, the subjects performed the visuomotor tracking and somatosensory oddball tasks concurrently for about an hour. In the oddball-only condition, they performed just the oddball task for the same period. ResultsTracking performance improved with task repetition. The amplitude of the P300 elicited by somatosensory stimulation in the oddball-only condition decreased significantly with task repetition, whereas in the dual-task condition, it showed a complex pattern of change. The earlier responses were decreased in amplitude in the dual-task condition compared to the oddball-only condition, and gradually decreased with task repetition in both conditions. ConclusionsDynamic changes in ERPs and task performance with dual-task repetition support the idea that dual-task repetition produces changes in resource allocation following the automation of stimulus processing in addition to so-called habituation. SignificanceThis study also provides evidence for use of ERP amplitudes as physiological indices of functionally different types of resources.

BDNF polymorphism predicts the rate of decline in skilled task performance and hippocampal volume in healthy individuals

Numerous studies have indicated a link between the presence of polymorphism in brain-derived neurotrophic factor (BDNF) and cognitive and affective disorders. However, only a few have studied these effects longitudinally along with structural changes in the brain. This study was carried out to investigate whether valine-to-methionine substitution at position 66 (val66met) of pro-BDNF could be linked to alterations in the rate of decline in skilled task performance and structural changes in hippocampal volume. Participants consisted of 144 healthy Caucasian pilots (aged 40–69 years) who completed a minimum of 3 consecutive annual visits. Standardized flight simulator score (SFSS) was measured as a reliable and quantifiable indicator for skilled task performance. In addition, a subset of these individuals was assessed for hippocampal volume alterations using magnetic resonance imaging. We found that val66met substitution in BDNF correlated longitudinally with the rate of decline in SFSS. Structurally, age-dependent hippocampal volume changes were also significantly altered by this substitution. Our study suggests that val66met polymorphism in BDNF can be linked to the rate of decline in skilled task performance. Furthermore, this polymorphism could be used as a predictor of the effects of age on the structure of the hippocampus in healthy individuals. Such results have implications for understanding possible disabilities in older adults performing skilled tasks who are at a higher risk for cognitive and affective disorders.

Motor Skill Learning, Retention, and Control Deficits in Parkinson's Disease

Parkinson's disease, which affects the basal ganglia, is known to lead to various impairments of motor control. Since the basal ganglia have also been shown to be involved in learning processes, motor learning has frequently been investigated in this group of patients. However, results are still inconsistent, mainly due to skill levels and time scales of testing. To bridge across the time scale problem, the present study examined de novo skill learning over a long series of practice sessions that comprised early and late learning stages as well as retention. 19 non-demented, medicated, mild to moderate patients with Parkinson's disease and 19 healthy age and gender matched participants practiced a novel throwing task over five days in a virtual environment where timing of release was a critical element. Six patients and seven control participants came to an additional long-term retention testing after seven to nine months. Changes in task performance were analyzed by a method that differentiates between three components of motor learning prominent in different stages of learning: Tolerance, Noise and Covariation. In addition, kinematic analysis related the influence of skill levels as affected by the specific motor control deficits in Parkinson patients to the process of learning. As a result, patients showed similar learning in early and late stages compared to the control subjects. Differences occurred in short-term retention tests; patients' performance constantly decreased after breaks arising from poorer release timing. However, patients were able to overcome the initial timing problems within the course of each practice session and could further improve their throwing performance. Thus, results demonstrate the intact ability to learn a novel motor skill in non-demented, medicated patients with Parkinson's disease and indicate confounding effects of motor control deficits on retention performance.

The dynamics of development on the Dimensional Change Card Sorting task

A widely used paradigm to study cognitive flexibility in preschoolers is the Dimensional Change Card Sorting (DCCS) task. The developmental dynamics of DCCS performance was studied in a cross-sectional design (N = 93, 3 to 5 years of age) using a computerized version of the standard DCCS task. A model-based analysis of the data showed that development on the DCCS task is best described as a discontinuous change in performance on the post-switch phase of the task. In addition to a perseveration group and a switch group, a transitional group that showed shifts between perseverating and switching during the post-switch trials could be distinguished. Computational models of performance and development on the DCCS task cannot, in their current forms, explain these results. We discuss how a catastrophe model of the developmental changes in task performance could be used to generate specific hypotheses about the variables that control development of DCCS performance.

Division of labor increases with colony size in the harvester ant Pogonomyrmex californicus

Size has profound consequences for the structure and function of biological systems, across levels of organization from cells to social groups. As tightly integrated units that vary greatly in size, eusocial insect colonies, in particular, are expected to exhibit social scaling relations. To address the question of how social organization scales with colony size, we quantified task performance in variably sized colonies of the harvester ant Pogonomyrmex californicus. We found a positive scaling relationship between colony size and division of labor in 2 different contexts. First, individual workers were more specialized in older, larger colonies. Second, division of labor increased with colony size, independently of colony age. Moreover, the proportional allocation of workers to tasks shifted during colony ontogeny—older, larger colonies performed relatively less brood care—but did not vary with colony size among same-aged colonies. There were no colony-size effects on per capita activity or the distribution of activity across workers. Size-related changes in task performance were correlated with changes in the rate of encounter between nest mates. These results highlight the importance of colony size for the organization of work in insect societies and raise broader questions about the role of size in sociobiology.

Effects of instructed focus and task difficulty on concurrent walking and cognitive task performance in healthy young adults

Dual task paradigms can be used to examine the interactions between cognition and the control of posture and gait. Measuring and interpreting changes in dual task performance is challenging, however, because many factors can influence performance. This study examined the effects of instructed focus and walking task difficulty, and the interaction between these factors, on dual task performance in healthy young adults. Fifteen participants performed a cognitive task while walking with either a usual base or a narrow base of support. Participants were instructed to focus on either the cognitive task or walking. Trade-offs both within and between tasks were assessed using the modified attention allocation index and the performance operating characteristic. Instructed focus influenced both the cognitive task and walking. Performance on the cognitive task was faster with instructions to focus on the cognitive task, and walking was faster (and more accurate in the narrow-base condition) with instructions to focus on walking. Walking task difficulty did not affect cognitive performance but did affect walking, with faster walking in the usual-base versus narrow-base condition. There was evidence of an interaction, with greater effects of instructed focus on the cognitive task during usual versus narrow-base walking. These results support the idea that the ability to flexibly shift attention allocation and task performance in response to instructions depends on the difficulty of the postural control task. The modified attention allocation index and the performance operating characteristic were instrumental in fully characterizing trade-offs between and within tasks in order to understand dual task performance changes. A clearer understanding of the factors that affect dual task walking and the interactions between these factors has important implications for the assessment of dual task performance in both clinical and research settings.

Gamma oscillations as a neuronal correlate of the attentional effects of pain

Successful behavior requires the attentional selection and preferred processing of behaviorally relevant sensory information. Painful stimuli are of utmost behavioral relevance and can therefore involuntarily affect attentional resources and interfere with ongoing behavior. However, the neuronal mechanisms which subserve the involuntary attentional effects of pain are largely unknown yet. Here, we therefore investigated the neuronal mechanisms of the attentional effects of pain by using electroencephalography during a visual attention task with the concurrent presentation of painful stimuli. Our results confirm that painful and visual stimuli induce gamma oscillations over central and occipital areas, respectively. Pain-induced gamma oscillations were correlated with pain-induced changes in visual gamma oscillations. Behaviorally, we observed variable effects of pain on visual reaction times, yielding an increase of reaction times for some subjects, as well as a decrease of reaction times for others. Most importantly, however, these changes in visual task performance were significantly related to pain-induced changes of visual gamma oscillations. These findings demonstrate that the variable attentional effects of pain are closely related to changes in neuronal gamma oscillations in the human brain. In the hypervigilant state of chronic pain, maladaptive changes in the attentional effects of pain may be associated with abnormal changes in neuronal gamma oscillations. Our findings may thus contribute to the understanding of the neuronal substrates of pain in health and may open a new window towards the understanding of pathological alterations of the pain experience in chronic pain syndromes.

Perceptual organization and visual search processes during target detection task performance in schizophrenia, as revealed by fMRI

BackgroundPast studies of perceptual organization in schizophrenia have demonstrated impairments binding fragmented stimulus components into unified representations. ERP and fMRI data indicate that even under conditions of adequate behavioral task performance, significant and meaningful changes in cortical and subcortical activation are present. Here, we examined, using fMRI, activation differences on a visual task wherein feature grouping was a precursor to the formation of distinct groups in the service of target location and identification. MethodFourteen schizophrenia patients and 16 healthy controls completed a target detection task with 2 conditions: one in which target–distractor grouping facilitates detection (the Isolated condition) and one in which it hinders detection (the Embedded condition). Stimuli were blocked by condition. Accuracy and RT data were obtained in addition to fMRI data. ResultsPatients and controls did not differ significantly in accuracy or RT in either condition. Within this context, controls demonstrated greater recruitment of brain regions involved in visual–spatial processing, and the groups differed in activity in areas known to support visual search, visual analysis, decision making and response generation. ConclusionThese findings are consistent with past data indicating reduced processing of stimulus organization, and the subsequent use of inefficient visual search strategies, even under conditions when behavioral performance is at a high level and matches that of healthy controls.