Task-dependent Effects Research Articles

Task Dependent Effects of Head Orientation on Perceived Gaze Direction.

The perception of gaze direction involves the integration of a number of sensory cues exterior to the eye-region. The orientation of the head is one such cue, which has an overall repulsive effect on the perceived direction of gaze. However, in a recent experiment, we found the measured effect of head orientation on perceived gaze direction differed within subjects, depending on whether a single- or two-interval task design was employed. This suggests a potential difference in the way the orientation of the head is integrated into the perception of gaze direction across tasks. Four experiments were conducted to investigate this difference. The first two experiments showed that the difference was not the result of some interaction between stimuli in the two-interval task, but rather, a difference between the types of judgment being made across tasks, where observers were making a directional (left/right) judgment in the single-interval task, and a non-directional (direct/indirect gaze) judgment in the two-interval task. A third experiment showed that this difference does not arise from observers utilizing a non-directional cue to direct gaze (the circularity of the pupil/iris) in making their non-directional judgments. The fourth experiment showed no substantial differences in the duration of evidence accumulation and processing between judgments, suggesting that observers are not integrating different sensory information across tasks. Together these experiments show that the sensory information from head orientation is flexibly weighted in the perception of gaze direction, and that the purpose of the observer, in sampling gaze information, can influence the consequent perception of gaze direction.

The effects of a subsequent jump on the knee abduction angle during the early landing phase

BackgroundA double-leg landing with or without a subsequent jump is commonly used to evaluate the neuromuscular control of knee abduction. However, the differences in frontal plane knee biomechanics between landings with and without a subsequent jump are not well known. The purpose of the present study was to investigate the effects of a subsequent jump on knee abduction, including during the early landing phase, in female and male subjects.MethodsTwenty-one female subjects and 21 male subjects participated. All subjects performed drop landing task (a landing without a subsequent jump) and drop vertical jump task (a landing with a subsequent jump). The subjects landed from a 30-cm height. In drop vertical jump, the subjects also performed a maximum vertical jump immediately after landing. The knee abduction angle and moment were analyzed using a 3D motion analysis system. A two-way analysis of variance (task × time) was performed to examine the effects of a subsequent jump on the knee abduction angle during the early landing phase in female and male subjects. Another two-way analysis of variance (task × sex) was performed to compare peak knee abduction angles and moments.ResultsIn female subjects, the knee abduction angle was significantly greater during drop vertical jump than during drop landing, as measured 45 to 80 ms after initial contact (P < 0.05). Significant task-dependent effects in the peak knee abduction angle (P = 0.001) and the abduction moment (P = 0.029) were detected. The peak knee abduction angle and the abduction moment were greater during drop vertical jump than during drop landing.ConclusionsSubsequent jumps cause greater knee abduction during the early landing phase only in female subjects. This finding may relate to the sex discrepancy in non-contact anterior cruciate ligament injuries. Additionally, the presence of a subsequent jump significantly increases the peak knee abduction angle and the peak knee abduction moment during landings. Therefore, compared with a landing task without a subsequent jump (drop landing), a landing task with a subsequent jump (drop vertical jump) may be advantageous for screening for knee abduction control, especially in female athletes.

Active Sound Localization Sharpens Spatial Tuning in Human Primary Auditory Cortex.

Spatial hearing sensitivity in humans is dynamic and task-dependent, but the mechanisms in human auditory cortex that enable dynamic sound location encoding remain unclear. Using functional magnetic resonance imaging (fMRI), we assessed how active behavior affects encoding of sound location (azimuth) in primary auditory cortical areas and planum temporale (PT). According to the hierarchical model of auditory processing and cortical functional specialization, PT is implicated in sound location ("where") processing. Yet, our results show that spatial tuning profiles in primary auditory cortical areas (left primary core and right caudo-medial belt) sharpened during a sound localization ("where") task compared with a sound identification ("what") task. In contrast, spatial tuning in PT was sharp but did not vary with task performance. We further applied a population pattern decoder to the measured fMRI activity patterns, which confirmed the task-dependent effects in the left core: sound location estimates from fMRI patterns measured during active sound localization were most accurate. In PT, decoding accuracy was not modulated by task performance. These results indicate that changes of population activity in human primary auditory areas reflect dynamic and task-dependent processing of sound location. As such, our findings suggest that the hierarchical model of auditory processing may need to be revised to include an interaction between primary and functionally specialized areas depending on behavioral requirements.SIGNIFICANCE STATEMENT According to a purely hierarchical view, cortical auditory processing consists of a series of analysis stages from sensory (acoustic) processing in primary auditory cortex to specialized processing in higher-order areas. Posterior-dorsal cortical auditory areas, planum temporale (PT) in humans, are considered to be functionally specialized for spatial processing. However, this model is based mostly on passive listening studies. Our results provide compelling evidence that active behavior (sound localization) sharpens spatial selectivity in primary auditory cortex, whereas spatial tuning in functionally specialized areas (PT) is narrow but task-invariant. These findings suggest that the hierarchical view of cortical functional specialization needs to be extended: our data indicate that active behavior involves feedback projections from higher-order regions to primary auditory cortex.

Model-based analysis of fatigued human knee extensors

This study investigated the effect of isometrically induced fatigue on Hill-type muscle model parameters and related task-dependent effects. Parameter identification methods were used to extract fatigue-related parameter trends from isometric and ballistic dynamic maximum voluntary knee extensions. Nine subjects, who completed ten fatiguing sets, each consisting of nine 3 s isometric maximum voluntary contractions with 3 s rest plus two ballistic contractions with different loads, were analyzed. Only at the isometric task, the identified optimized model parameter values of muscle activation rate and maximum force generating capacity of the contractile element decreased from 20.8 pm 8.4 to 11.2 pm 4.1 Hz and from 18{,}137 pm 150 to 10{,}666 pm 2139 N, respectively. For all tasks, the maximum efficiency of the contractile element, mathematically related to the curvature of the force–velocity relation, increased from 0.35 pm 0.04 to 0.42 pm 0.05. The model parameter maximum contraction velocity decreased from 0.93 pm 0.1 to 0.9 pm 0.1 m/s and the stiffness of the serial elastic element from 1936 pm 227 to 1432 pm 245 N/mm. Thus, models of fatigue should consider fatigue dependencies in active as well as in passive elements, and muscle activation dynamics should account for the task dependency of fatigue.

P 63 Investigating the effects of tRNS variants and task dependency on cortical excitability

Background Transcranial random noise stimulation (tRNS) has specific benefits and is fundamentally different as compared to more established methods such as transcranial direct current stimulation (tDCS) in modulating brain function (Terney et al., 2008; Ambrus et al., 2010). For example, previous research in the motor system has shown corticospinal excitability (CSE) to be task-dependent (Terney et al., 2008). It remains unresolved and largely unaddressed what the critical stimulation parameters of tRNS are, e.g. with regard to noise type (i.e. Gaussian, uniform) or current intensity (i.e. peak-to-peak amplitude, I max; effective current, I eff ). To study the effects of different tRNS parameters and task-dependency, Experiment 1 compared conventional, Gaussian tRNS (g-tRNS, 1 mA I max ) with uniform tRNS (u-tRNS, 1 mA I max ). Experiment 2 compared tRNS to anodal tDCS at higher, but equivalent effective current intensities (0.8 mA I eff ). The hypotheses were that (i) effects would be independent of noise distribution type and dependent on current intensity and (ii) that anodal tDCS and tRNS would induce similar effects if applied with comparable current intensities. The primary outcome measure was corticospinal excitability (CSE). Methods Twenty-nine healthy, right-handed individuals received stimulation over the left M1 in a double-blind, sham-controlled, within-subjects study design. Experiment 1 investigated g-tRNS (1 mA I max , 0.22 mA I eff ) and u-tRNS (1 mA I max ; 0.52 mA I eff ). Experiment 2 investigated tRNS (0.8 mA I eff ; 1.51 mA I max ) and anodal tDCS (0.8 mA I eff ; 0.8 mA I max ). Participants were randomly assigned one of two motor tasks to perform during tRNS/tDCS or sham stimulation. Half of the participants performed a simple motor task associated with cortical excitation (finger tapping-task, FT), the others performed a complex motor task associated with response inhibition (go/no-go-task, GNG). CSE was evaluated with 20 MEPs from the FDI prior to- and after 10 min of stimulation with task-execution. Results In Experiment 1, both g-tRNS and u-tRNS did not affect CSE. At higher current intensities, Experiment 2 found diverging task dependent effects comparing tRNS to anodal tDCS. TRNS facilitated CSE in the FT-group (331 μ V, +/−133 μ V) while inhibiting CSE in the GNG-group (−113 μ V, +/−59 μ V) with a significant difference between groups (pairwise comparisons, p = 0.004). TDCS in the FT group, significantly inhibited CSE (−80 μ V +/−106 μ V; pairwise comparisons, p = 0.044) and showed no effect in the GNG group. Conclusions Low tRNS current intensities do not influence CSE. Higher tRNS intensities (0.8 mA I eff ), but not anodal tDCS (0.8 mA), modulate CSE in a task-dependent manner. Future studies may benefit from the higher effective current intensities possible with uniform but not Gaussian noise and may take advantage of task dependency to potentiate the effect of tRNS.

It's the Thought That Counts: Examining the Task-Dependent Effects of Transcranial Direct Current Stimulation on Executive Function

Background: Prior investigations employing transcranial direct current stimulation (tDCS) have shown that stimulation can elicit subsequent improvement on tests of various cognitive abilities, including working memory. While stimulation parameters such as intensity and duration are known to determine the effects of tDCS, the degree to which stimulation effectsare influenced bycognitive activitiesduring stimulation remains unclear.

Body ownership and agency: task-dependent effects of the virtual hand illusion on proprioceptive drift.

Body ownership and agency are fundamental to self-consciousness. These bodily experiences have been intensively investigated using the rubber hand illusion, wherein participants perceive a fake hand as their own. After presentation of the illusion, the position of the participant's hand then shifts toward the location of the fake hand (proprioceptive drift). However, it remains controversial whether proprioceptive drift is able to provide an objective measurement of body ownership, and whether agency also affects drift. Using the virtual hand illusion (VHI), the current study examined the effects of body ownership and agency on proprioceptive drift, with three different visuo-motor tasks. Twenty healthy adults (29.6±9.2years old) completed VH manipulations using their right hand under a 2×2 factorial design (active vs. passive manipulation, and congruent vs. incongruent virtual hand). Prior to and after VH manipulation, three different tasks were performed to assess proprioceptive drift, in which participants were unable to see their real hands. The effects of the VHI on proprioceptive drift were task-dependent. When participants were required to judge the position of their right hand using a ruler, or by reaching toward a visual target, both body ownership and agency modulated proprioceptive drift. Comparatively, when participants aligned both hands, drift was influenced by ownership but not agency. These results suggest that body ownership and agency might differentially modulate various body representations in the brain.

Task dependency effects of collaboration in learners’ corpus consultation: An exploratory case study

AbstractCollaborative learning has attracted attention as pedagogic mediation to assist learners’ corpus consultation, but some studies have pointed to negative aspects of collaboration. Based on the two sides of collaboration in language learning, this study presents a qualitative investigation of different effects of collaboration depending on task types used in learners’ corpus consultation. This study examined two types of tasks: a conceptual task, which tested students’ competence to draw a generalizable conclusion through a meaning-making process of corpus consultation; and a procedural task, which asked students to complete problem-solving activities strategically through corpus analysis. Two groups of three students were given the same tasks of corpus consultation but asked to complete the tasks either collaboratively or individually. The students’ verbal and nonverbal behaviors during the task completion, pre-and post-interviews, and the instructor’s observation notes were the main sources of data for analysis. The results of this study showed that collaboration has significantly different effects depending on the task types of corpus consultation. The collaborative group (CG) outperformed the individual group (IG) in the conceptual corpus consultation task, but the procedural task was more efficiently completed by the IG than the CG. The underperformance of the CG in the procedural task seemed to be partly attributable to the role of established intersubjectivity and the power inequality in the CG. Despite some limitations, the findings of this study reveal task-dependent effects of collaboration in corpus consultation and suggest practical implications for more effective and pedagogically beneficial use of learners’ corpus consultation in second language (L2) instruction.

Differential effects of wake promoting drug modafinil in aversive learning paradigms.

Modafinil (MO) an inhibitor of the dopamine transporter was initially approved to treat narcolepsy, a sleep related disorder in humans. One interesting “side-effect” of this drug, which emerged from preclinical and clinical studies, is the facilitation of cognitive performance. So far, this was primarily shown in appetitive learning paradigms, but it is yet unclear whether MO exerts a more general cognitive enhancement effect. Thus, the aim of the present study in rats was to extend these findings by testing the effects of MO in two aversive paradigms, Pavlovian fear conditioning (FC) and the operant two-way active avoidance (TWA) learning paradigms. We discovered a differential, task-dependent effect of MO. In the FC paradigm MO treated rats showed a dose-dependent enhancement of fear memory compared to vehicle treated rats, indicated by increased context-related freezing. Cue related fear memory remained unaffected. In the TWA paradigm MO induced a significant decrease of avoidance responses compared to vehicle treated animals, while the number of escape reactions during the acquisition of the TWA task remained unaffected. These findings expand the knowledge in the regulation of cognitive abilities and may contribute to the understanding of the contraindicative effects of MO in anxiety related mental disorders.

Allocation of cognitive resources in comparative visual search – Individual and task dependent effects

Behaviors recruit multiple, mutually substitutable types of cognitive resources (e.g., data acquisition and memorization in comparative visual search), and the allocation of resources is performed in a cost-optimizing way. If costs associated with each type of resource are manipulated, e.g., by varying the complexity of the items studied or the visual separation of the arrays to be compared, according adjustments of resource allocation (“trade-offs”) have been demonstrated. Using between-subject designs, previous studies showed overall trade-off behavior but neglected inter-individual variability of trade-off behavior. Here, we present a simplified paradigm for comparative visual search in which gaze-measurements are replaced by switching of a visual mask covering one stimulus array at a time. This paradigm allows for a full within-subject design. While overall trade-off curves could be reproduced, we found that each subject used a specific trade-off strategy which differ substantially between subjects. Still, task-dependent adjustment of resource allocation can be demonstrated but accounts only for a minor part of the overall trade-off range. In addition, we show that the individual trade-offs were adjusted in an unconscious and rather intuitive way, enabling a robust manifestation of the selected strategy space.

Effect of nitric oxide synthase inhibitor l-NAME on fear extinction in rats: A task-dependent effect

There is increasing evidence that nitric oxide may be involved in learning and memory. However, there remain comparatively few studies that have explored the relationship between nitric oxide signaling and fear extinction, an inhibitory learning model. In the present study, we tested the effects of nitric oxide synthase inhibitor l-NAME on three tone fear extinction tasks in rats. In task 1, rats received fear conditioning, extinction training and extinction test in the same context (AAA design). In task 2, rats received fear conditioning in context A, extinction training in context B and extinction test in context A (ABA design). In task 3, rats received fear conditioning in context A, extinction training and extinction test in context B (ABB design). l-NAME (10, 20 and 40mg/kg) was injected intraperitoneally 30min prior to extinction training in each task. Percent of time spent freezing was used to measure conditioned fear response. We found that l-NAME administrations had no effect on freezing in task 1 and 2 but produced a dose-dependent increase in task 3. Further results indicated that the increased freezing in task 3 was not attributed to state-dependency effects or nonspecific changes of locomotor activity that followed l-NAME injection. These results showed that l-NAME produced a task-dependent impairment of fear extinction, and implied that nitric oxide signaling was involved in memory process of certain extinction tasks.

Task-Specific Effect of Transcranial Direct Current Stimulation on Motor Learning

Transcranial direct current stimulation (tDCS) is a relatively new non-invasive brain stimulation technique that modulates neural processes. When applied to the human primary motor cortex (M1), tDCS has beneficial effects on motor skill learning and consolidation in healthy controls and in patients. However, it remains unclear whether tDCS improves motor learning in a general manner or whether these effects depend on which motor task is acquired. Here we compare whether the effect of tDCS differs when the same individual acquires (1) a Sequential Finger Tapping Task (SEQTAP) and (2) a Visual Isometric Pinch Force Task (FORCE). Both tasks have been shown to be sensitive to tDCS applied over M1, however, the underlying processes mediating learning and memory formation might benefit differently from anodal transcranial direct current stimulation (anodal-tDCS). Thirty healthy subjects were randomly assigned to an anodal-tDCS group or sham-group. Using a double-blind, sham-controlled cross-over design, tDCS was applied over M1 while subjects acquired each of the motor tasks over three consecutive days, with the order being randomized across subjects. We found that anodal-tDCS affected each task differently: the SEQTAP task benefited from anodal-tDCS during learning, whereas the FORCE task showed improvements only at retention. These findings suggest that anodal-tDCS applied over M1 appears to have a task-dependent effect on learning and memory formation.

The wide-open doors to lexical access

The wide-open doors to lexical access

History of Reading Struggles Linked to Enhanced Learning in Low Spatial Frequency Scenes

People with dyslexia, who face lifelong struggles with reading, exhibit numerous associated low-level sensory deficits including deficits in focal attention. Countering this, studies have shown that struggling readers outperform typical readers in some visual tasks that integrate distributed information across an expanse. Though such abilities would be expected to facilitate scene memory, prior investigations using the contextual cueing paradigm failed to find corresponding advantages in dyslexia. We suggest that these studies were confounded by task-dependent effects exaggerating known focal attention deficits in dyslexia, and that, if natural scenes were used as the context, advantages would emerge. Here, we investigate this hypothesis by comparing college students with histories of severe lifelong reading difficulties (SR) and typical readers (TR) in contexts that vary attention load. We find no differences in contextual-cueing when spatial contexts are letter-like objects, or when contexts are natural scenes. However, the SR group significantly outperforms the TR group when contexts are low-pass filtered natural scenes [F(3, 39) = 3.15, p<.05]. These findings suggest that perception or memory for low spatial frequency components in scenes is enhanced in dyslexia. These findings are important because they suggest strengths for spatial learning in a population otherwise impaired, carrying implications for the education and support of students who face challenges in school.

A task-dependent effect of memory and hand-target on proprioceptive localization

We examine whether the task goal affects the accuracy and precision with which participants can localize an unseen hand. Proprioceptive localization was measured using three different tasks: two goal-directed movement tasks (reaching to and reproducing final hand-target location) and a perceptual estimation task in which participants judged the location of the hand-target relative to visual references. We also assessed whether proprioceptive localization in these different tasks is affected by localization from memory, the hand-target being localized (left or right) or the movement path of the proprioceptive target (9 paths, derived from combinations of starting and final hand-target positions). We found that participants were less precise when reaching from memory, but not when reproducing or estimating remembered final hand-target location. Participants also misperceived the felt location of their hands, judging their left hand to be more leftward and their right hand to be more rightward when reaching to and when estimating final hand-target location, but not when reproducing hand-target location. The movement path of the proprioceptive target did not affect localization, regardless of the task goal. Overall, localization seems poorer when proprioception is used to guide a reach with the opposite hand, particularly from memory, and best when merely reproducing the proprioceptive target site. This may have an important application in neuro-rehabilitation, whereby one task may better establish or re-establish important or failing sensory connections.

Task-dependent effects of interhemispheric inhibition on motor control

Interhemispheric communication consists of a complex balance of facilitation and inhibition that is modulated in a task-dependent manner. However, it remains unclear how individual differences in interhemispheric interactions relate to motor performance. To assess interhemispheric inhibition, we utilized the ipsilateral silent period technique (iSP; evoked by suprathreshold transcranial magnetic stimulation), which elicits inhibition of volitional motor activity. Participants performed three force production tasks: (1) unimanual (right hand) constant force, (2) bimanual constant force, (bimanual simultaneous) and (3) bimanual with right hand constant force and left hand sine wave tracking (bimanual independent). We found that individuals with greater IHI capacity demonstrated reduced mirror EMG activity in the left hand during unimanual right hand contraction. However, these same individuals demonstrated the poorest performance during the bimanual independent force production task. We suggest that a high capacity for IHI from one motor cortex to another can effectively prevent “motor overflow” during unimanual tasks, but it can also limit interhemispheric cooperation during independently controlled bimanual tasks.

Evidence for motor cortex dedifferentiation in older adults

Older adults (OA) show more diffuse brain activity than young adults (YA) during the performance of cognitive, motor, and perceptual tasks. It is unclear whether this overactivation reflects compensation or dedifferentiation. Typically, these investigations have not evaluated the organization of the resting brain, which can help to determine whether more diffuse representations reflect physiological or task-dependent effects. In the present study we used transcranial magnetic stimulation (TMS) to determine whether there are differences in motor cortex organization of both brain hemispheres in young and older adults. We measured resting motor threshold, motor evoked potential (MEP) latency and amplitude, and extent of first dorsal interosseous representations, in addition to a computerized measure of reaction time. There was no significant age difference in motor threshold, but we did find that OA had larger contralateral MEP amplitudes and a longer contralateral MEP latency. Furthermore, the spatial extent of motor representations in OA was larger. We found that larger dominant hemisphere motor representations in OA were associated with higher reaction times, suggesting dedifferentiation rather than compensation effects.

A PRP-study to determine the locus of target priming effects

Visual stimuli that are made invisible by a following mask can nonetheless affect motor responses. To localize the origin of these target priming effects we used the psychological refractory period paradigm. Participants classified tones as high or low, and responded to the position of a visual target that was preceded by a prime. The stimulus onset asynchrony (SOA) between both tasks varied. In Experiment 1 the tone task was followed by the position task and SOA dependent target priming effects were observed. When the visual position task preceded the tone task in Experiment 2, with short SOA the priming effect propagated entirely to the tone task yielding faster responses to tones on visually congruent trials and delayed responses to tones on visually incongruent trials. Together, results suggest that target priming effects arise from processing before and at the level of the central bottleneck such as sensory analysis and response selection.

Semantic alignment and number comparison

Are the quantity representations activated by Arabic digits influenced by semantic context? We developed a novel paradigm to examine semantic alignment effects (e.g., Bassok et al. in J Exp Psychol Learn Mem Cogn 34:343-352, 2008) in number comparison. A horizontal word pair (either less more or few many) appeared for 480ms to prime either relative magnitude (less more) or quantity (few many). Then a horizontal pair of single digits that were either successors (near) or differed by at least four (far) appeared above the word pair. Participants indicated verbally whether or not the word and digit pairs were congruent with respect to left-to-right ascending or descending relative magnitude. The RT advantage for far number pairs compared to near pairs (the distance effect) was greater with magnitude primes (81ms) than quantity primes (17ms), demonstrating a semantic alignment effect. This effect disappeared in Experiment 2 in which participants received identical stimuli but named the larger of the two digits and were free to ignore the primes. Nonetheless, mean RT in Experiment 2 was faster with prime and target pairs both ascending or both descending, but only with quantity primes. This prime-dependent order-congruity effect suggests that semantic alignment with respect to numerical order affected number comparison in Experiment 2. The results thereby demonstrate that number comparison exhibits task-dependent semantic alignment effects and recruits distinct numerical representations as a function of semantic context (e.g., Cohen Kadosh and Walsh in Behav Brain Sci 32:313-373, 2009).

Large-scale cortical functional organization and speech perception across the lifespan.

Aging is accompanied by substantial changes in brain function, including functional reorganization of large-scale brain networks. Such differences in network architecture have been reported both at rest and during cognitive task performance, but an open question is whether these age-related differences show task-dependent effects or represent only task-independent changes attributable to a common factor (i.e., underlying physiological decline). To address this question, we used graph theoretic analysis to construct weighted cortical functional networks from hemodynamic (functional MRI) responses in 12 younger and 12 older adults during a speech perception task performed in both quiet and noisy listening conditions. Functional networks were constructed for each subject and listening condition based on inter-regional correlations of the fMRI signal among 66 cortical regions, and network measures of global and local efficiency were computed. Across listening conditions, older adult networks showed significantly decreased global (but not local) efficiency relative to younger adults after normalizing measures to surrogate random networks. Although listening condition produced no main effects on whole-cortex network organization, a significant age group x listening condition interaction was observed. Additionally, an exploratory analysis of regional effects uncovered age-related declines in both global and local efficiency concentrated exclusively in auditory areas (bilateral superior and middle temporal cortex), further suggestive of specificity to the speech perception tasks. Global efficiency also correlated positively with mean cortical thickness across all subjects, establishing gross cortical atrophy as a task-independent contributor to age-related differences in functional organization. Together, our findings provide evidence of age-related disruptions in cortical functional network organization during speech perception tasks, and suggest that although task-independent effects such as cortical atrophy clearly underlie age-related changes in cortical functional organization, age-related differences also demonstrate sensitivity to task domains.