Attentional load associated with performing and stabilizing a between-persons coordination of rhythmic limb movements

This study addressed the issue of intentional stabilization of between-persons coordination patterns (in-phase/isodirectional and anti-phase/non-isodirectional) and the attentional cost incurred by the nervous system in maintaining and further stabilizing these coordination patterns. Five pairs of participants performed in-phase and anti-phase interpersonal coordination patterns in dual-task conditions (coordination+RT task). Results showed that: (1) isodirectional pattern (in-phase) was more stable than non-isodirectional pattern (anti-phase), (2) both iso- and non-isodirectional pattern were stabilized intentionally, (3) RT was lower for the isodirectional pattern (i.e., the most stable), and (4) attentional manipulation led to a trade-off between pattern stability and RT performance. These results suggest that performing between-persons coordination patterns incurs a central cost that depends on the coupling strength between the limbs. These findings are consistent with the previous studies in intrapersonal coordination.     

Effects of aging on whole body and segmental control while obstacle crossing under impaired sensory conditions

The ability to safely negotiate obstacles is an important component of independent mobility, requiring adaptive locomotor responses to maintain dynamic balance. This study examined the effects of aging and visual–vestibular interactions on whole-body and segmental control during obstacle crossing. Twelve young and 15 older adults walked along a straight pathway and stepped over one obstacle placed in their path. The task was completed under 4 conditions which included intact or blurred vision, and intact or perturbed vestibular information using galvanic vestibular stimulation (GVS). Global task performance significantly increased under suboptimal vision conditions. Vision also significantly influenced medial–lateral center of mass displacement, irrespective of age and GVS. Older adults demonstrated significantly greater trunk pitch and head roll angles under suboptimal vision conditions. Similar to whole-body control, no GVS effect was found for any measures of segmental control. The results indicate a significant reliance on visual but not vestibular information for locomotor control during obstacle crossing. The lack of differences in GVS effects suggests that vestibular information is not up-regulated for obstacle avoidance. This is not differentially affected by aging. In older adults, insufficient visual input appears to affect ability to minimize anterior–posterior trunk movement despite a slower obstacle crossing time and walking speed. Combined with larger medial–lateral deviation of the body COM with insufficient visual information, the older adults may be at a greater risk for imbalance or inability to recover from a possible trip when stepping over an obstacle.     

Attentional mechanisms associated with repressive distancing

This research explores the role of attentional shift and disengagement in repressive distancing. During a target-detection task in which emotional and neutral facial expressions were used as cues, participants received performance feedback intended to elicit a negative emotional reaction that rendered the task either threatening or not threatening to self-concept. When the task was perceived to threaten self-concept, repressors distanced themselves by rapidly disengaging their attention from the facial expressions rather than by slowly shifting or not shifting their attention to the facial expressions. Attentional disengagement was accompanied by sympathetic nervous system activity suggestive of a defense response. This research provides further insight into the nature and consequences of the interplay of dispositional tendencies, situational contexts, and higher order cognitive influences in attentional behavior.     

Attentional set interacts with perceptual load in visual search

In the present study, we examined the hypothesis that perceptual load is the primary factor that determines the efficiency of attentional selection. Participants performed a visual search task under conditions of high- and low-load. In line with the perceptual load hypothesis, presenting conditions of highand low-load in separate blocks of trials resulted in processing of to-be-ignored stimuli only in the lowload condition (Experiment 1). However when high- and low-load conditions were randomly mixed in blocks of trials, the participants showed processing of to-be-ignored stimuli in both conditions, suggesting that high perceptual load is not necessarily sufficient to obtain perceptual selectivity (Experiment 2). An analysis of intertrial transition effects showed that on high-load trials, processing of to-be-ignored stimuli occurred only when the previous trial was a low-load trial. The results suggest that low perceptual load can engender broad attentional processing. On the other hand, when a high-load trial was preceded by another high-load trial, little processing of task-irrelevant stimuli was observed. The present results are discussed in terms of the interaction between expectancies and bottom-up factors in the efficiency of attentional selection.     

Attentional loads associated with interlimb interactions underlying rhythmic bimanual coordination

Studies of rhythmic bimanual coordination under dual-task conditions revealed (1) a dependence of secondary task performance on the stability of coordinative tasks, in that secondary task performance was better during in-phase than antiphase coordination, and (2) a shift in the mean relative phasing between the limbs compared to single-task conditions. The present study aimed to account for these phenomena by dissociating three qualitatively different interactions between the limbs that govern this motor behavior, related to movement planning, error correction, and interlimb reflex activity. The experiment probed the cognitive demands associated with each interlimb interaction by examining the attentional load under dual-task conditions, indexed by reaction times of the secondary task and kinematic changes in the coordinative tasks relative to single-task conditions. First, only in the condition that involved interlimb interactions at the level of movement planning reaction times were shorter for in-phase than for antiphase coordination, highlighting an intimate relation between movement planning and attentional processes. Second, under dual-task conditions a shift in the mean relative phase was observed relative to single-task conditions, but only for the interlimb interactions that depend directly on sensory feedback (error correction and interlimb reflex activity). These observations qualified the effects of attentional load reported in previous studies. Third, reaction times varied systematically over the movement cycle. These variations revealed a dynamical signature of the attentional load that differed between the three interlimb interactions.     

Cognitive demands of error processing associated with preparation and execution of a motor skill

Maxwell et al. [Maxwell, J. P., Masters, R. S. W., Kerr, E., & Weedon, E. (2001). The implicit benefit of learning without errors. The Quarterly Journal of Experimental Psychology, 54A, 1049–1068. The implicit benefit of learning without errors. The Quarterly Journal of Experimental Psychology, 54A, 1049–1068] suggested that, following unsuccessful movements, the learner forms hypotheses about the probable causes of the error and the required movement adjustments necessary for its elimination. Hypothesis testing is an explicit process that places demands on cognitive resources. Demands on cognitive resources can be identified by measuring probe reaction times (PRT) and movement times. Lengthened PRT and movement times reflects increased cognitive demands. Thus, PRT and movement times should be longer following errors, relative to successful, movements. This hypothesis was tested using a motor skill (golf putting). Furthermore, the association between error processing and the preparation and execution phases of movement was examined. The data confirmed that cognitive demand is greater for trials following an error, relative to trials without an error. This effect was apparent throughout learning and in both the preparatory and execution phases of the movement. Cognitive effort also appeared to be higher during movement preparation, relative to movement execution.     

Attentional Focus of Students with Hyperactivity During a Word-Search Task

Mirrors have been used to focus attention to aspects of the self (e.g., to known strategies, standards). We hypothesized that this could be important for students with hyperactivity/inattention, who typically direct attention outward to external novelty. In this study, we administered a partially solvable word puzzle to 43 middle school students, with and without hyperactivity/inattention, in the presence and absence of a mirror, counterbalanced for condition and form order. Differences between students with hyperactivity/inattention and comparisons in accuracy were found only in the no mirror condition. Furthermore, the beneficial effect of the mirror for children with hyperactivity/inattention was most pronounced for those who looked at the mirror. Findings were interpreted in terms of their potential to remedy the production deficits of these children.     

Culture,carrying, and communication: Beliefs and behavior associated with babywearing

Ethnographic research suggests mother-infant physical contact predicts high levels of maternal responsiveness to infant cues, yet it is unclear whether this responsiveness is driven by the act of physical contact or by underlying beliefs about responsiveness. We examine beliefs and behavior associated with infant carrying (i.e., babywearing) among U.S. mothers and experimentally test the effect of mother-infant physical contact on maternal responsiveness. In Study 1 (N = 23 dyads), babywearing mothers were more likely to interact contingently in response to infant cues than non-babywearing mothers during an in-lab play session. In Study 2 (N = 492 mothers), babywearing predicted maternal beliefs emphasizing responsiveness to infant cues. In Study 3 (N = 20 dyads), we experimentally manipulated mother-infant physical contact in the lab using a within-subjects design and found that babywearing increased maternal tactile interaction, decreased maternal and infant object contact, and increased maternal responsiveness to infant vocalizations. Our results motivate further research examining how culturally-mediated infant carrying practices shape the infant’s early social environment and subsequent development.     

Chronic work stress and exhaustion is associated with higher allostastic load in female school teachers

Epidemiological studies have shown that chronic work stress or unfavourable psychosocial work conditions are prospectively associated with different adverse health outcomes. The aim of the present cross-sectional study was to investigate the relationship between work-related chronic stress as well as exhaustion and a cumulative measure of physiological wear-and-tear called allostastic load (AL). AL could be a possible biological pathway for how chronic work stress and exhaustion lead to health impairments in the long run. As the teaching profession has been proposed to be a potentially high stressful occupation, chronic work stress (effort-reward-imbalance) and exhaustion were assessed in 104 female school teachers. AL was first analyzed according to McEwen's classical model comprised of ten parameters including cortisol, epinephrine and norepinephrine, dehydroepiandrosterone-sulphate (DHEA-S), waist/hip-ratio (WHR), glycosylated haemoglobin (HbA1c), high-density lipoprotein (HDL), total cholesterol/HDL-ratio, and systolic and diastolic blood pressure. Additionally it was extended to include tumor-necrosis-factor-alpha (TNF-alpha), C-reactive protein (CRP), fibrinogen, D-dimer, percent-body-fat, triglycerides, and glucose levels. A substantial proportion of our sample was highly exhausted whereas relatively few teachers showed high effort-reward-imbalance. AL scores were significantly higher in women high on effort-reward-imbalance or suffering from exhaustion. Although all teachers had been in a good health status, chronic work stress as well as exhaustion appears to be associated with changes in a multi-system summary indicator of physiological risk.     

Effects of anticipation certainty on preparatory brain activity and anticipatory postural adjustments associated with voluntary unilateral arm movement while standing

We examined the effects of anticipation certainty concerning which voluntary movement is required in response to a stimulus while standing on preparatory brain activity and anticipatory postural adjustments (APAs). Ten right-handed adults abducted their left or right arm rapidly in response to a visual imperative stimulus, based on the type of stimulus. A warning cue, which did or did not contain information about the side of arm abduction, was presented 2000ms before the imperative stimulus. Preparatory brain activity before arm abduction was quantified by the mean amplitude of the contingent negative variation 100ms before the imperative stimulus (late CNV amplitude). Compared with the low anticipation condition, in the high anticipation condition the following results were obtained only in the case of right arm abduction: (1) larger late CNV amplitude, (2) earlier postural muscle activities with respect to the focal muscle of arm abduction, and (3) smaller peak displacement of center of pressure during the abduction. These findings suggest that high anticipation of voluntary movement of dominant arm to a stimulus while standing influences preparatory brain activity before the movement, resulting in earlier APAs and thus smaller disturbance of postural equilibrium during the movement.     

Preschoolers out of adults: Discriminative learning with a cognitive load

This paper explores novel predictions from the spontaneous overtraining interpretation of human discrimination shift learning (Sirois & Shultz, 1998a). Results from six experiments where adults perform a discrimination shift task with or without a cognitive distractor are reported. In three experiments with a concurrent distractor task (Experiments 1A, 2A, and 3A), performance of adults is comparable to what would be expected from preschoolers performing only the learning task. These adults show no dimensional transfer from initial learning, unless new attributes are introduced in shift learning. On the same tasks without a cognitive load (Experiments 1B, 2B, and 3B), performance is typical of normal adults. The discussion focuses on the relative ability of competing theoretical models (i.e., levels of processing, attentional mediation, and perceptual differentiation) to account for these data.     

Preschoolers out of adults: discriminative learning with a cognitive load

This paper explores novel predictions from the spontaneous overtraining interpretation of human discrimination shift learning (Sirois & Shultz, 1998a). Results from six experiments where adults perform a discrimination shift task with or without a cognitive distractor are reported. In three experiments with a concurrent distractor task (Experiments 1A, 2A, and 3A), performance of adults is comparable to what would be expected from preschoolers performing only the learning task. These adults show no dimensional transfer from initial learning, unless new attributes are introduced in shift learning. On the same tasks without a cognitive load (Experiments 1B, 2B, and 3B), performance is typical of normal adults. The discussion focuses on the relative ability of competing theoretical models (i.e., levels of processing, attentional mediation, and perceptual differentiation) to account for these data.     

Evidence for selective target processing with a low perceptual load flankers task

In this article, we demonstrate that selective target processing is possible when the perceptual load of the task is low. We presented a row of three items with two different identities: one identity for the target letter and one for the two flankers (B. A. Eriksen & C. W. Eriksen, 1974). Such stimulus arrays have been defined as low-load displays (Lavie & Tsal, 1994). We investigated whether subjects could ignore the irrelevant flankers, which were never response alternatives, by manipulating the predictive relationship between the flankers and the response (Miller, 1987). In a high-correlation block, the identity of the flankers was highly predictive of the target identity, whereas in a lowcorrelation block, the predictive value of the flankers was reduced. We varied (1) whether or not the target location was precued, (2) the flanker’s category (digit vs. letter), (3) the target-flanker proximity (near = 3° vs. far = 5°), and (4) the size of the characters. The results indicate that subjects were influenced by the predictive value of near flankers and that the magnitude of this effect was jointly modulated by the target-flanker categorical overlap and by the size of the characters. In contrast, null flanker effects were obtained for far letter flankers in the precue condition, and for far digit flankers, regardless of attentional cuing. These findings (1) are inconsistent with suggestions (Lavie, 1995) that irrelevant stimuli automatically capture attention, and (2) support the notion that target-flanker distinctiveness plays a role when the perceptual load of the task is low.     

Recurrent fluent aphasia associated with a seizure focus

The relationship between dominant hemisphere seizure activity and aphasia is unclear. Although speech arrest, expressive speech problems, and comprehension difficulties have often been associated with temporal lobe seizure activity, neologistic, paraphasic speech is rare. We report a patient with seizures following encephalitis who had recurrent episodes of fluent, severely aphasic speech with impaired comprehension which correlated with continuous, high voltage spike and slow wave activity in the left temporal region. During a several-day period of intermittent electrographic seizure activity, he had fluctuating receptive aphasia, and he developed transient paranoid psychosis following treatment. We discuss the behavioral manifestations of his left temporal seizures and correlate the changing nature of his behavior with therapeutic interventions. This case, as well as a review of others, suggests that paroxysmal fluent aphasia results from a partially treated electrographic seizure focus in the dominant temporal lobe.     

The effect of instruction to synchronize over step frequency while walking with auditory cues on a treadmill

Walking to a pacing stimulus has proven useful in motor rehabilitation, and it has been suggested that spontaneous synchronization could be preferable to intentional synchronization. But it is still unclear if the paced walking effect can occur spontaneously, or if intentionality plays a role. The aim of this work is to analyze the effect of sound pacing on gait with and without instruction to synchronize, and with different rhythmic auditory cues, while walking on a treadmill.Firstly, the baseline step frequency while walking on a treadmill was determined for all participants, followed by experimental sessions with both music and footstep sound cues. Participants were split into two groups, with one being instructed to synchronize their gait to the auditory stimuli, and the other being simply told to walk. Individual auditory cues were generated for each participant: for each trial, cues were provided at the participant’s baseline walking frequency, at 5% and 10% above baseline, and at 5% and 10% below baseline.This study’s major finding was the role of intention on synchronization, given that only the instructed group synchronized their gait with the auditory cues. No differences were found between the effects of step or music stimuli on step frequency.In conclusion, without intention or cues that direct the individual’s attention, spontaneous gait synchronization does not occur during treadmill walking.     

Environmental factors associated with a spectrum of neurodevelopmental deficits

A number of environmental agents have been shown to demonstrate neurotoxic effects either in human or laboratory animal studies. Critical windows of vulnerability to the effects of these agents occur both pre- and postnatally. The nervous system is relatively unique in that different parts are responsible for different functional domains, and these develop at different times (e.g., motor control, sensory, intelligence and attention). In addition, the many cell types in the brain have different windows of vulnerability with varying sensitivities to environmental agents. This review focuses on two environmental agents, lead and methylmercury, to illustrate the neurobehavioral and cognitive effects that can result from early life exposures. Special attention is paid to distinguishing between the effects detected following episodes of poisoning and those detected following lower dose exposures. Perinatal and childhood exposure to high doses of lead results in encephalopathy and convulsions. Lower-dose lead exposures have been associated with impairment in intellectual function and attention. At high levels of prenatal exposure, methylmercury produces mental retardation, cerebral palsy and visual and auditory deficits in children of exposed mothers. At lower levels of methylmercury exposure, the effects in children have been more subtle. Other environmental neurotoxicants that have been shown to produce developmental neurotoxicity include polychlorinated biphenyls (PCBs), dioxins, pesticides, ionizing radiation, environmental tobacco smoke, and maternal use of alcohol, tobacco, marijuana and cocaine. Exposure to environmental agents with neurotoxic effects can result in a spectrum of adverse outcomes from severe mental retardation and disability to more subtle changes in function depending on the timing and dose of the chemical agent.     

Ultrastructural plasticity associated with hippocampal-dependent learning: a meta-analysis

In order to develop a profile of how individual synapses in the hippocampal formation alter their structure following learning experience, a meta-analysis synthesized the available literature on morphological change following hippocampal-dependent learning. Analysis of the 132 calculated effect sizes suggest a consistent profile of morphological change in the hippocampus following learning experience. Across the hippocampal formation, dendritic complexity, spine density, and the size of perforated postsynaptic densities showed consistent increases following training. Both the density of synapses in general and perforated synapses in particular showed unique responses to training, depending on the duration of training and/or different cell layers of the hippocampal formation. Most importantly, it seems that this profile, while consistent, is small and specific--only a select few of the morphological parameters typically measured in anatomical studies of plasticity showed significant change following training. Collectively, these data suggest that the distinct electrophysiological properties of neocortical versus hippocampal synapses may be at least partially mediated by distinct morphological cascades. That is, on the basis of theory, and with the support of the current data, it seems that synaptogenesis correlates with enduring neocortical plasticity, while structural changes correlate with more transient hippocampal plasticity. To be able to state these conclusions with conviction, however, more data are needed in several key areas for continued pursuit of the morphological correlates of hippocampal-dependent learning.