"Automatic" online reach corrections are associated with individual differences in executive function.

Previous research has demonstrated that the dorsal visual stream is able to execute rapid online movement corrections to sudden changes in target position. This "automatic pilot" can operate in the absence of visual awareness, and even under circumstances where participants are instructed to not correct their movements. In the current study, we examined the extent to which these "automatic" corrections might be related to individual differences in executive function.

Direction of visual shift and hand congruency enhance spatial realignment during visuomotor adaptation.

Although prism adaptation has been studied extensively for over 100 years to better understand how the motor system adapts to sensory perturbations, very few studies have systematically studied how the combination of the hand used to adapt, and the direction of visual shift, might influence adaptation. Given that sensory inputs and motor outputs from the same side are processed (at least initially) in the same hemisphere, we wondered whether there might be differences in how people adapt when the hand used and the direction of visual shift were congruent (e.g.

Assessment and recovery of visually guided reaching deficits following cerebellar stroke.

The cerebellum is known to play an important role in the coordination and timing of limb movements. The present study focused on how reach kinematics are affected by cerebellar lesions to quantify both the presence of motor impairment, and recovery of motor function over time. In the current study, 12 patients with isolated cerebellar stroke completed clinical measures of cognitive and motor function, as well as a visually guided reaching (VGR) task using the Kinarm exoskeleton at baseline (∼2 weeks), as well as 6, 12, and 24-weeks post-stroke.

Left Cerebellar Lesions may be Associated with an Increase in Spatial Neglect-like Symptoms.

Each cerebellar hemisphere projects to the contralateral cerebral hemisphere. Previous research suggests a lateralization of cognitive functions in the cerebellum that mirrors the cerebral cortex, with attention/visuospatial functions represented in the left cerebellar hemisphere, and language functions in the right cerebellar hemisphere. Although there is good evidence supporting the role of the right cerebellum with language functions, the evidence supporting the notion that attention and visuospatial functions are left lateralized is less clear.

The Ties that Bind: Agnosia, Neglect and Selective Attention to Visual Scale.

Purpose Of Review: Historical and contemporary treatments of visual agnosia and neglect regard these disorders as largely unrelated. It is thought that damage to different neural processes leads directly to one or the other condition, yet apperceptive variants of agnosia and object-centered variants of neglect share remarkably similar deficits in the quality of conscious experience. Here we argue for a closer association between "apperceptive" variants of visual agnosia and "object-centered" variants of visual neglect.

Cerebellar lesions disrupt spatial and temporal visual attention.

The current study represents the first comprehensive examination of spatial, temporal and sustained attention following cerebellar damage. Results indicated that, compared to controls, cerebellar damage resulted in a larger cueing effect at the longest SOA - possibly reflecting a slowed the onset of inhibition of return (IOR) during a reflexive covert attention task, and reduced the ability to detect successive targets during an attentional blink task. However, there was little evidence to support the notion that cerebellar damage disrupted voluntary covert attention or the sustained attention to response task (SART).

Cerebellar tDCS Alters the Perception of Optic Flow.

Studies have shown that the cerebellar vermis is involved in the perception of motion. However, it is unclear how the cerebellum influences motion perception. tDCS is a non-invasive brain stimulation technique that can reduce (through cathodal stimulation) or increase neuronal excitability (through anodal stimulation).

Visuomotor adaptation in the absence of input from early visual cortex.

Prism adaptation is a time-honored tool for studying how the motor system adapts to sensory perturbations. Past research on the neural substrates of prism adaptation has implicated the posterior parietal cortex (PPC) and the cerebellum, under the assumption that these structures gain their visual input from the dominant retinogeniculate pathway to V1. Here we question whether this pathway is even required for visuomotor adaptation to occur.

Affective blindsight in the absence of input from face processing regions in occipital-temporal cortex.

Previous research suggests that the implicit recognition of emotional expressions may be carried out by pathways that bypass primary visual cortex (V1) and project to the amygdala. Some of the strongest evidence supporting this claim comes from case studies of "affective blindsight" in which patients with V1 damage can correctly guess whether an unseen face was depicting a fearful or happy expression. In the current study, we report a new case of affective blindsight in patient MC who is cortically blind following extensive bilateral lesions to V1, as well as face and object processing regions in her ventral visual stream.

Prism adaptation speeds reach initiation in the direction of the prism after-effect.

Damage to the temporal-parietal cortex in the right hemisphere often leads to spatial neglect-a disorder in which patients are unable to attend to sensory input from their contralesional (left) side. Neglect has been associated with both attentional and premotor deficits. That is, in addition to having difficulty with attending to the left side, patients are often slower to initiate leftward vs.

Prism adaptation magnitude has differential influences on perceptual versus manual responses.

Previous research has indicated that rightward prism adaptation can reduce symptoms of spatial neglect following right brain damage. In addition, leftward prism adaptation can create "neglect-like" patterns of performance in healthy adults on tasks that measure attention and spatial biases. Although a great deal of research has focused on which behaviors are influenced by prism adaptation, very few studies have focused directly on how the magnitude of visual shift induced by prisms might be related to the observed aftereffects, or the effects of prisms on measures of attentional and spatial biases.

Deficits in reflexive covert attention following cerebellar injury.

Traditionally the cerebellum has been known for its important role in coordinating motor output. Over the past 15 years numerous studies have indicated that the cerebellum plays a role in a variety of cognitive functions including working memory, language, perceptual functions, and emotion. In addition, recent work suggests that regions of the cerebellum involved in eye movements also play a role in controlling covert visual attention.

Overlapping neural circuits for visual attention and eye movements in the human cerebellum.

Previous research in patients with cerebellar damage suggests that the cerebellum plays a role in covert visual attention. One limitation of some of these studies is that they examined patients with heterogeneous cerebellar damage. As a result, the patterns of reported deficits have been inconsistent.

Spatial working memory deficits represent a core challenge for rehabilitating neglect.

Left neglect following right hemisphere injury is a debilitating disorder that has proven extremely difficult to rehabilitate. Traditional models of neglect have focused on impaired spatial attention as the core deficit and as such, most rehabilitation methods have tried to improve attentional processes. However, many of these techniques (e.

Retinotopic organization of the visual cortex before and after decompression of the optic chiasm in a patient with pituitary macroadenoma.

Compression induced by a pituitary tumor on the optic chiasm can generate visual field deficits, yet it is unknown how this compression affects the retinotopic organization of the visual cortex. It is also not known how the effect of the tumor on the retinotopic organization of the visual cortex changes after decompression. The authors used functional MRI (fMRI) to map the retinotopic organization of the visual cortex in a 68-year-old right-handed woman before and 3 months after surgery for a recurrent pituitary macroadenoma.

Programs for action in superior parietal cortex: a triple-pulse TMS investigation.

Converging evidence from neurological patients and functional brain imaging studies strongly supports the notion that the posterior parietal cortex (PPC), especially in the left hemisphere, plays a critical role in both the programming (i.e., setting the initial movement parameters of the reach) and the online control of goal-directed reaching movements.

Grasping the non-conscious: preserved grip scaling to unseen objects for immediate but not delayed grasping following a unilateral lesion to primary visual cortex.

Patients with damage to primary visual cortex can sometimes direct actions towards 'unseen' targets located in areas of the visual field that are deemed 'blind' on the basis of static perimetry tests. Here, we show that a patient with a complete right homonymous hemianopia after a V1 lesion remains sensitive to the width of objects presented in her blind field but only when reaching out to grasp them in 'real-time'. A subsequent fMRI experiment revealed spared extra-geniculostriate pathways, which may mediate her preserved abilities.

Through a prism darkly: re-evaluating prisms and neglect.

Many studies have demonstrated that prism adaptation can reduce several symptoms of visual neglect: a disorder in which patients fail to respond to information in contralesional space. The dominant framework to explain these effects proposes that prisms influence higher order visuospatial processes by acting on brain circuits that control spatial attention and perception. However, studies that have directly examined the influence of prisms on perceptual biases inherent to neglect have revealed very few beneficial effects.

Dissociating perceptual and motor effects of prism adaptation in neglect.

Prism adaptation reduces some symptoms of neglect; however the mechanisms underlying such changes are poorly understood. We suggest that prisms influence neglect by acting on dorsal stream circuits subserving visuomotor control, with little influence on perceptual aspects of neglect. We examined prism adaptation in three neglect patients and a group of healthy controls on line bisection and landmark tasks.

Can intention override the "automatic pilot"?

Previous research has suggested that the visuomotor system possesses an "automatic pilot" which allows people to make rapid online movement corrections in response to sudden changes in target position. Importantly, the automatic pilot has been shown to operate in the absence of visual awareness, and even under circumstances in which people are explicitly asked not to correct their ongoing movement. In the current study, we investigated the extent to which the automatic pilot could be "disengaged" by explicitly instructing participants to ignore the target jump (i.

"Real-time" obstacle avoidance in the absence of primary visual cortex.

When we reach toward objects, we easily avoid potential obstacles located in the workspace. Previous studies suggest that obstacle avoidance relies on mechanisms in the dorsal visual stream in the posterior parietal cortex. One fundamental question that remains unanswered is where the visual inputs to these dorsal-stream mechanisms are coming from.

Syllogistic reasoning time: disconfirmation disconfirmed.

Models of deductive reasoning typically assume that reasoners dedicate more logical analysis to unbelievable conclusions than to believable ones (e.g., Evans, Newstead, Allen, & Pollard, 1994; Newstead, Pollard, Evans, & Allen, 1992).