Influence of iron manipulation on hypoxic pulmonary vasoconstriction and pulmonary reactivity during ascent and acclimatization to 5050 m.

KEY POINTS: Iron acts as a cofactor in the stabilization of the hypoxic-inducible factor family, and plays an influential role in the modulation of hypoxic pulmonary vasoconstriction. It is uncertain whether iron regulation is altered in lowlanders during either (1) ascent to high altitude, or (2) following partial acclimatization, when compared to high-altitude adapted Sherpa. During ascent to 5050 m, the rise in pulmonary artery systolic pressure (PASP) was blunted in Sherpa, compared to lowlanders; however, upon arrival to 5050 m, PASP levels were comparable in both groups, but the reduction in iron bioavailability was more prevalent in lowlanders compared to Sherpa. Following partial acclimatization to 5050 m, there were differential influences of iron status manipulation (via iron infusion or chelation) at rest and during exercise between lowlanders and Sherpa on the pulmonary vasculature. ABSTRACT: To examine the adaptational role of iron bioavailability on the pulmonary vascular responses to acute and chronic hypobaric hypoxia, the haematological and cardiopulmonary profile of lowlanders and Sherpa were determined during: (1) a 9-day ascent to 5050 m (20 lowlanders; 12 Sherpa), and (2) following partial acclimatization (11 ± 4 days) to 5050 m (18 lowlanders; 20 Sherpa), where both groups received an i.v. infusion of either iron (iron (iii)-hydroxide sucrose) or an iron chelator (desferrioxamine). During ascent, there were reductions in iron status in both lowlanders and Sherpa; however, Sherpa appeared to demonstrate a more efficient capacity to mobilize stored iron, compared to lowlanders, when expressed as a Δhepcidin per unit change in either body iron or the soluble transferrin receptor index, between 3400-5050 m (P = 0.016 and P = 0.029, respectively). The rise in pulmonary artery systolic pressure (PASP) was blunted in Sherpa, compared to lowlanders during ascent; however, PASP was comparable in both groups upon arrival to 5050 m. Following partial acclimatization, despite Sherpa demonstrating a blunted hypoxic ventilatory response and greater resting hypoxaemia, they had similar hypoxic pulmonary vasoconstriction when compared to lowlanders at rest. Iron-infusion attenuated PASP in both groups at rest (P = 0.005), while chelation did not exaggerate PASP in either group at rest or during exaggerated hypoxaemia ( PIO2  = 67 mmHg). During exercise at 25% peak wattage, PASP was only consistently elevated in Sherpa, which persisted following both iron infusion or chelation. These findings provide new evidence on the complex interplay of iron regulation on pulmonary vascular regulation during acclimatization and adaptation to high altitude.

Hand anthropometry and the limits of aperture separation determine the utility of Weber's law in grasping and manual estimation.

Recent work proposed that biomechanical constraints in aperture separation limit the utility of Weber's law in determining whether dissociable visual codes support grasping and manual estimation. We tested this assertion by having participants precision grasp, manually estimate and complete a method of adjustment task to targets scaled within and beyond the range of their maximal aperture separation (i.e., from 20 to 140% of participant-specific maximal aperture separation: MAS). For grasping and manual estimation tasks, just-noticeable-difference (JND) scores were computed via the within-participant standard deviations in peak grip aperture, whereas method of adjustment JNDs were computed via the within-participant standard deviations in response output. Method of adjustment JNDs increased linearly across the range of targets; that is, responses adhered to Weber's law. Manual estimation JNDs linearly increased for targets 20-100% of MAS and then decreased for targets 120-140% of MAS. In turn, grasping JNDs for targets 20% through 80% of MAS did not differ and were larger than targets 100-140% of MAS. That manual estimation and grasping showed a decrease in JNDs for the largest targets indicates that participants were at their biomechanical limits in aperture shaping, and the fact that the target showing the JND decrease differed between tasks (i.e., manual estimation = 100% of MAS; grasping = 80% of MAS) is attributed to the fact that grasping-but not manual estimation-requires a safety-margin task-set. Accordingly, manual estimations and grasping across a range of functionally 'graspable' targets, respectively, adhered to and violated Weber's law-a result interpreted to reflect the use of dissociable visual codes.

Availability of vision and tactile gating: vision enhances tactile sensitivity.

A multitude of events bombard our sensory systems at every moment of our lives. Thus, it is important for the sensory and motor cortices to gate unimportant events. Tactile suppression is a well-known phenomenon defined as a reduced ability to detect tactile events on the skin before and during movement. Previous experiments (Buckingham et al. in Exp Brain Res 201(3):411-419, 2010; Colino et al. in Physiol Rep 2(3):e00267, 2014) found detection rates decrease just prior to and during finger abduction and decrease according to the proximity of the moving effector. However, what effect does vision have on tactile gating? There is ample evidence (see Serino and Haggard in Neurosci Biobehav Rev 34:224-236, 2010) observing increased tactile acuity when participants see their limbs. The present study examined how tactile detection changes in response to visual condition (vision/no vision). Ten human participants used their right hand to reach and grasp a cylinder. Tactors were attached to the index finger and the forearm of both the right and left arm and vibrated at various epochs relative to a "go" tone. Results replicate previous findings from our laboratory (Colino et al. in Physiol Rep 2(3):e00267, 2014). Also, tactile acuity decreased when participants did not have vision. These results indicate that the vision affects the somatosensation via inputs from parietal areas (Konen and Haggard in Cereb Cortex 24(2):501-507, 2014) but does so in a reach-to-grasp context.

Explicit knowledge and real-time action control: anticipating a change does not make us respond more quickly.

When the target of a goal-directed reach changes location, people normally respond rapidly and automatically to the target shift. Here, we investigate whether explicit knowledge about a moving target (knowing whether a location change is likely/unlikely) improves responsiveness, with the goal of understanding top-down effects on real-time reaching. In Experiment 1, we presented participants with pre-cues that indicated a 20 or 80% likelihood of a target perturbation on that trial. When participants made pro-pointing responses to the target perturbations, their online response occurred later for 20% trials than for 80% trials, but this effect may have been due to suppression of the online response on 20% trials, rather than enhancement of the response on 80% trials. In Experiment 2, we presented participants with 50 and 100% likelihood pre-cues, and observed no shortening of the latency on 100% trials compared to 50% trials, which suggests that expectation does not enhance the automatic response to a perturbation. However, we did observe more vigorous responses to the perturbation on the 100% trials, and this contributed to shorter movement times relative to the 50% trials. We also examined, in Experiment 2, whether prior knowledge about the direction of the target perturbation would shorten the latency of the online response, but we did not observe any reduction in latency. In sum, the onset of the automatic response appears to be suppressible, but not augmentable by top-down input. The possibility that the forcefulness of the automatic response is modifiable by expectation is examined, but not resolved.

How low can you go? Measuring human event-related brain potentials from a two-channel EEG system.

Over the past ten years, there has been a rapid increase in the availability and use of mobile electroencephalography (mEEG) in research. Indeed, researchers using mEEG have recorded EEG and event-related brain potentials in a wide range of environments - for example, while walking (Debener et al., 2012), riding a bike (Scanlon et al., 2020), or even in a shopping mall (Krigolson et al., 2021). However, given that low-cost, ease-of-use, and setup speed provide the primary advantages of an mEEG system over large array traditional EEG systems, an important and unresolved question is just how many electrodes does an mEEG system need to collect research-quality EEG data? Here, we tested whether or not a two-channel forehead-mounted mEEG system - the "Patch" - could measure event-related brain potentials within their established amplitude and latency characteristics (Luck, 2014). In the present study, participants performed a visual oddball task while we recorded EEG data from the Patch. Our results demonstrated that we could capture and quantify the N200 and P300 event-related brain potential components using a minimal electrode array forehead-mounted EEG system. Our data further support the idea that mEEG can be used for quick and rapid EEG-based assessments, such as measuring the impact of concussions on the sports field (Fickling et al., 2021) or assessing the impact of stroke severity in a hospital (Wilkinson et al., 2020).

Exercising is good for the brain but exercising outside is potentially better.

It is well known that exercise increases cognitive function. However, the environment in which the exercise is performed may be just as important as the exercise itself. Time spent in natural outdoor environments has been found to lead to increases in cognition similar to those resulting from acute exercise. Therefore, the benefits of both exercise and nature exposure suggest an additive impact on brain function when both factors are combined. This raises the question: what is the interaction between acute exercise and environment on cognition? We answered this question using electroencephalography to probe cognitive function using the oddball task before and after brief indoor and outdoor walks on 30 participants (average 21 years old, 95% CI [20, 22]). Our results demonstrate improved performance and an increase in the amplitude of the P300, an event-related neural response commonly associated with attention and working memory, following a 15-min walk outside; a result not seen following a 15-min walk inside. Importantly, this finding indicates that the environment may play a more substantial role in increasing cognitive function such as attention than exercise, at least in terms of acute exercise (i.e., a brief walk). With the world's growing urbanization and the associated increase in sedentary time indoors, a deeper understanding of how these factors interact and influence cognition may be critical to combat adverse health effects.

Influence of posture on the regulation of cerebral perfusion.

BACKGROUND: Posture has a major influence on cerebral blood flow (CBF). Unlike head-up tilt (HUT), less is known about how CBF is regulated during head-down tilt (HDT). We hypothesized that CBF would be elevated during HDT and decreased during HUT. METHODS: In 21 healthy young adults, while controlling for end-tidal Pco2, we combined concurrent measurements of middle cerebral artery velocity and posterior cerebral artery velocity (MCAv and PCAv, respectively), blood pressure (BP), and heart rate (HR). Measures were made at rest and, in a randomized order, during -90 degrees HDT and +900 HUT. Dynamic cerebral autoregulation was quantified using transfer function analysis. In a subgroup, volumetric blood flow recordings were obtained in the common carotid artery (CCA; N=11), internal and external carotid arteries (ICA; N=8 and ECA; N=6), and vertebral artery (VA; N=4). RESULTS: End-tidal Pco2, CCA, ICA, VA, MCAv(mean) and PCAv(mean) remained unchanged during -90 degrees HDT and +90 degrees HUT compared to supine. During -90 degrees HDT, mean BP (+22 mmHg) and cerebral vascular resistance (CVR) in both the MCA and PCA were elevated relative to supine, whereas HR remained unchanged. During +900 HUT, when compared to supine, HR increased (+18 bpm), and mean arterial pressure (MAP) total power and low frequency (LF) power in the MCA and PCA increased. In both the very low frequency (VLF) and LF ranges, coherence during +90 degrees HUT increased (P < 0.05 vs. supine) in both the MCA and PCA. In contrast, coherence was reduced during -90 degrees HDT. DISCUSSION: Despite marked changes in perfusion pressure with HUT or HDT, our findings indicate that cerebral perfusion is well maintained during acute severe changes in posture.

Preceding movement effects on sequential aiming.

In this study, two experiments were devised to examine the control strategy used by individuals when performing sequential aiming movements. Of particular interest was the aiming behavior displayed when task difficulty was changed midway through a sequence of movements. In Experiment 1, target size was manipulated, as the targets were made either larger or smaller, between the 8th and 12th movement of the sequence. In Experiment 2, the amplitude between the two targets was similarly changed while the target size remained constant. Results revealed that in Experiment 1, individuals took two movements following the perturbation to target size, to re-tune their movement times in order to correspond with the new task difficulty. Conversely for Experiment 2, movement time changed immediately and in correspondence with the new target amplitude. These findings demonstrate that participants can use information from the preceding movement to prepare and guide subsequent movements--but only when target size is changed. When response amplitude changes mid-sequence, it seems individuals rely more on immediate, target-derived information. Therefore, counter to some current accounts of visual movement control, it appears that memory representations of the preceding movement can guide subsequent movements; however, this information appears selectively accessed in a context-dependent fashion.

Changing the sheets: a new system to reduce strain during patient repositioning.

BACKGROUND: Manually repositioning patients puts healthcare providers at risk for injury; this may be reduced by using low-friction bedsheets. OBJECTIVES: The aim of this study was to evaluate the physical properties and the physiological measures of muscle activity and perceptual participant accounts between a new slider sheet system and traditional hospital bedsheet makeup (soaker pad with a jersey bottom sheet). METHOD: Surface electromyography was recorded from the arm and shoulder muscles of five healthcare providers executing a patient repositioning (boosting and turning) in a controlled laboratory setting to gain an indication of muscle activity required for two types of bedsheets (slider system and traditional sheet makeup). The Borg Scale was used to establish rating of perceived exertion for these repositioning tasks on the two types of bedsheet makeup. To evaluate the sheets independent of human interaction and contact, the physical resistive characteristics of the sheets were calculated by determining the coefficient of friction. RESULTS: Patient repositioning on traditional sheets, compared with the slider system, resulted in 16% greater electromyography burst numbers and 11% longer duration for both boosting and turning. Moreover, ratings of perceived exertion for repositioning patients on traditional sheets versus on slider sheets were more than double. The coefficient of friction of the traditional sheets was 65% less in the slider sheet system. DISCUSSION: This study suggests that manually repositioning patients on a low-friction slider system reduces muscular and perceived effort. Proper usage of this type of bedsheets may reduce the risks associated with musculoskeletal strain and injuries of the healthcare providers.

Distribution of Practice Combined with Observational Learning Has Time Dependent Effects on Motor Skill Acquisition.

Studies of the benefits of a distributed practice schedule on motor skill acquisition have typically found that distribution of practice results in better learning. However, less research has focused on how the benefits of distributed practice are impacted by timing during acquisition. To examine how timing of skill acquisition interacts with distribution of practice we had two groups of participants complete either an extensive massed or distributed training schedule to learn a speed stacking sequence across ten sessions. For participants in both groups, we provided observational learning to facilitate skill acquisition. Analysis of speed stacking time on a retention test revealed an overall benefit for the distributed relative to the massed practice group. Interestingly, our analysis of the benefits of distributed practice during training only showed performance benefits in the early session (session one) and later sessions (sessions eight, nine, and ten) of skill acquisition but not mid-way through it (sessions two through seven). Our results support previous findings highlighting the learning benefits of a distributed practice schedule but suggest that these benefits occur differentially throughout acquisition. Our work also replicates research demonstrating that observational learning is more beneficial when it is yoked to actual practice.

Using Muse: Rapid Mobile Assessment of Brain Performance.

The advent of mobile electroencephalography (mEEG) has created a means for large scale collection of neural data thus affording a deeper insight into cognitive phenomena such as cognitive fatigue. Cognitive fatigue - a neural state that is associated with an increased incidence of errorful performance - is responsible for accidents on a daily basis which at times can cost human lives. To gain better insight into the neural signature of cognitive fatigue in the present study we used mEEG to examine the relationship between perceived cognitive fatigue and human-event related brain potentials (ERPs) and electroencephalographic (EEG) oscillations in a sample of 1,000 people. As a secondary goal, we wanted to further demonstrate the capability of mEEG to accurately measure ERP and EEG data. To accomplish these goals, participants performed a standard visual oddball task on an Apple iPad while EEG data were recorded from a Muse EEG headband. Counter to traditional EEG studies, experimental setup and data collection was completed in less than seven minutes on average. An analysis of our EEG data revealed robust N200 and P300 ERP components and neural oscillations in the delta, theta, alpha, and beta bands. In line with previous findings we observed correlations between ERP components and EEG power and perceived cognitive fatigue. Further, we demonstrate here that a linear combination of ERP and EEG features is a significantly better predictor of perceived cognitive fatigue than any ERP or EEG feature on its own. In sum, our results provide validation of mEEG as a viable tool for research and provide further insight into the impact of cognitive fatigue on the human brain.

Antisaccades exhibit diminished online control relative to prosaccades.

Convergent evidence suggests that stimulus-driven saccades (i.e., prosaccades) are mediated via online trajectory modifications (e.g., Gaveau et al. 2003). The goal of the present investigation was to determine whether manipulating the cognitive demands of a saccade influences the extent to which the response's trajectory is structured online. To that end, participants completed pro- and antisaccades (i.e., 180 degrees mirror-symmetrical transformation) to target stimuli that were continuously visible (Experiment 1) or occluded (Experiment 2) during the response. To index trajectory modifications, we computed the proportion of variance (R (2) values) explained by the spatial location of the eye at 10% increments of normalized movement time [i.e., 10, 20, ... 80, 90% of movement time (MT)] relative to the saccade's ultimate movement endpoint. The basis for this analysis is that between-task differences in the magnitude of R (2) values reflect differences in the use of feedback for online trajectory amendments. Results indicated that antisaccades produced larger R (2) values (from 40 to 80% of MT) as well as less accurate and more variable endpoints than their prosaccade counterparts. Such a pattern of results indicates that antisaccades were not controlled online to the same degree as prosaccades. In particular, we propose that the cognitive nature of the antisaccade task disrupts the normally online operation of saccade networks and renders a mode of control that is not optimized for feedback-based trajectory amendments.

Gating of vibrotactile detection during visually guided bimanual reaches.

It is far more difficult to detect a small tactile stimulation on a finger that is moving compared to when it is static. This suppression of tactile information during motion, known as tactile gating, has been examined in some detail during single-joint movements. However, the existence and time course of this gating has yet to be examined during visually guided multi-joint reaches, where sensory feedback may be paramount. The current study demonstrated that neurologically intact humans are unable to detect a small vibratory stimulus on one of their index fingers during a bimanual reach toward visual targets. By parametrically altering the delay between the visual target onset and the vibration, it was demonstrated that this gating was even apparent before participants started moving. A follow up experiment using electromyography indicated that gating was likely to occur even before muscle activity had taken place. This unique demonstration of tactile gating during a task reliant on visual feedback supports the notion this phenomenon is due to a central command, rather than a masking of sensory signals by afferent processing during movement.

Bimanual reaching across the hemispace: which hand is yoked to which?

When both hands perform concurrent goal-directed reaches, they become yoked to one another. To investigate the direction of this coupling (i.e., which hand is yoked to which), the temporal dynamics of bimanual reaches were compared with equivalent-amplitude unimanual reaches. These reaches were to target pairs located on either the left or right sides of space; meaning that in the bimanual condition, one hand's contralateral (more difficult) reach accompanied by the other hand's ipsilateral (easier) reach. By comparing which hand's difficult reach was improved more by the presence of the other hand's easier ipsilateral reach, we were able to demonstrate asymmetries in the coupling. When the cost of bimanual reaching was controlled for the contralateral reaching left hand's performance was improved, suggesting that the left hand is yoked to the right during motor output. In contrast, the right hand showed the greatest improvements for contralateral reaching in terms of reaction time, pointing toward a dominant role for the left hand in the processes prior to movement onset. The results may point toward a mechanism for integrating the unitary system of attention with bimanual coordination.

The impact of wellness on neural learning systems.

Over the past 20 years there has been an increasing push for people to achieve or maintain "wellness" - a state in which one has not only physical but also mental and social well-being. While it may seem obvious that maintaining a state of wellness is beneficial, little research has been done to probe how maintaining a state of wellness impacts our brain. Here, we specifically examined the impact of wellness on a neural system within the medial-frontal cortex responsible for human reinforcement learning. Sixty-two undergraduate students completed the Perceived Wellness Survey after which they completed a computer-based learnable gambling game while electroencephalographic data were recorded. Within the game, participants were presented with a series of choices that either led to financial gains or losses. An analysis of our behavioral data indicated that participants were able to learn the underlying structure of the gambling game given that we observed improvements in performance. Concurrent with this, we observed an electroencephalographic response evoked by the evaluation of gambling outcomes - the reward positivity. Importantly, we found significant relationships between several aspects of wellness and the amplitude of the reward positivity. Given that the reward positivity is thought to reflect the function of a reinforcement learning system within the medial-frontal cortex, our results suggest that wellness impacts neural function - in this instance one of the systems responsible for human learning.

Anti-pointing is mediated by a perceptual bias of target location in left and right visual space.

We sought to determine whether mirror-symmetrical limb movements (so-called anti-pointing) elicit a pattern of endpoint bias commensurate with perceptual judgments. In particular, we examined whether asymmetries related to the perceptual over- and under-estimation of target extent in respective left and right visual space impacts the trajectories of anti-pointing. In Experiment 1, participants completed direct (i.e. pro-pointing) and mirror-symmetrical (i.e. anti-pointing) responses to targets in left and right visual space with their right hand. In line with the anti-saccade literature, anti-pointing yielded longer reaction times than pro-pointing: a result suggesting increased top-down processing for the sensorimotor transformations underlying a mirror-symmetrical response. Most interestingly, pro-pointing yielded comparable endpoint accuracy in left and right visual space; however, anti-pointing produced an under- and overshooting bias in respective left and right visual space. In Experiment 2, we replicated the findings from Experiment 1 and further demonstrate that the endpoint bias of anti-pointing is independent of the reaching limb (i.e. left vs. right hand) and between-task differences in saccadic drive. We thus propose that the visual field-specific endpoint bias observed here is related to the cognitive (i.e. top-down) nature of anti-pointing and the corollary use of visuo-perceptual networks to support the sensorimotor transformations underlying such actions.

The antipointing task: vector inversion is supported by a perceptual estimate of visual space.

The authors examined whether the visual field-specific endpoint bias of mirror-symmetrical reaching movements (i.e., antipointing) is related to top-down decoupling of the normal spatial relations between target and response (i.e., visuomotor inhibition) or the inversion of target coordinates to a mirror-symmetrical location (i.e., vector inversion). Participants completed pro- and antipointing movements in left and right visual space under conditions in which movement type was performed in separate blocks (i.e., blocked condition) and when randomly interleaved on a trial-by-trial basis (i.e., random condition). Most important, the random condition entailed equivalent premovement inhibition across pro- and antipointing. Propointing produced comparable endpoint accuracy in left and right visual space whereas antipointing under- and overshot target position: a finding characterizing blocked and random conditions. The authors attribute the visual field-specific bias of antipointing to the obligatory nature of the task and the integration of visuoperceptual networks to support vector inversion.

A comparison of free weight squat to Smith machine squat using electromyography.

The purpose of this experiment was to determine whether free weight or Smith machine squats were optimal for activating the prime movers of the legs and the stabilizers of the legs and the trunk. Six healthy participants performed 1 set of 8 repetitions (using a weight they could lift 8 times, i.e., 8RM, or 8 repetition maximum) for each of the free weight squat and Smith machine squat in a randomized order with a minimum of 3 days between sessions, while electromyographic (EMG) activity of the tibialis anterior, gastrocnemius, vastus medialis, vastus lateralis, biceps femoris, lumbar erector spinae, and rectus abdominus were simultaneously measured. Electromyographic activity was significantly higher by 34, 26, and 49 in the gastrocnemius, biceps femoris, and vastus medialis, respectively, during the free weight squat compared to the Smith machine squat (p < 0.05). There were no significant differences between free weight and Smith machine squat for any of the other muscles; however, the EMG averaged over all muscles during the free weight squat was 43% higher when compared to the Smith machine squat (p < 0.05). The free weight squat may be more beneficial than the Smith machine squat for individuals who are looking to strengthen plantar flexors, knee flexors, and knee extensors.

Visuomotor memory is independent of conscious awareness of target features.

A recent study by our group showed that the scaling of reach trajectories to target size is independent of conscious visual awareness of that intrinsic target property (Binsted et al. in Proc Natl Acad Sci USA 104:12669-12672, 2007). The present investigation sought to extend previous work and determine whether unconscious target information represents a temporally durable or evanescent visuomotor characteristic. To accomplish that objective, we employed Di Lollo et al's (J Exp Psychol Gen 129:481-507, 2000) object substitution masking paradigm and asked participants to complete verbal reports and reaching responses to different sized (1.5, 2.5, 3.5, 4.5, 5.5 cm) targets under masked and non-masked target conditions. To determine whether visuomotor networks retain unconscious target information, reaching trials were cued concurrent with target presentation or 1,000 or 2,000 ms after target presentation. For the perceptual trials, participants readily identified the size of non-masked trials but demonstrated only chance success identifying target size during masked trials. Interestingly, however, reaches directed to non-masked and masked targets exhibited comparable and robust scaling with target size; that is, lawful speed-accuracy relations related to movement planning and execution times were observed regardless of whether participants were aware (i.e., non-masked trials) or unaware (i.e., masked trials) of target size. What is more, the length of the visual delay period used here did not differentially influence the scaling of reach trajectories. These results indicate that a conscious visual percept is not necessary to support motor output and that unconscious visual information persists in visuomotor networks to support the kinematic parameterization of action.

Goal-directed reaching: movement strategies influence the weighting of allocentric and egocentric visual cues.

The location of an object in peripersonal space can be represented with respect to our body (i.e., egocentric frame of reference) or relative to contextual features and other objects (i.e., allocentric frame of reference). In the current study, we sought to determine whether the frame, or frames, of visual reference supporting motor output is influenced by reach trajectories structured to maximize visual feedback utilization (i.e., controlled online) or structured largely in advance of movement onset via central planning mechanisms (i.e., controlled offline). Reaches were directed to a target embedded in a pictorial illusion (the induced Roelofs effect: IRE) and advanced knowledge of visual feedback was manipulated to influence the nature of reaching control as reported by Zelaznik et al. (J Mot Behav 15:217-236, 1983). When vision could not be predicted in advance of movement onset, trajectories showed primary evidence of an offline mode of control (even when vision was provided) and endpoints demonstrated amplified sensitivity to the illusory (i.e., allocentric) features of the IRE. In contrast, reaches performed with reliable visual feedback evidenced a primarily online mode of control and showed increased visuomotor resistance to the IRE. These findings suggest that the manner a reaching response is structured differentially influences the weighting of allocentric and egocentric visual information. More specifically, when visual feedback is unavailable or unpredictable, the weighting of allocentric visual information for the advanced planning of a reach trajectory is increased.