The half of the story we did not know about prism adaptation.

Since 1910 (Helmholtz, treatise on physiological optics), it is known that pointing under deviating prisms induces an initial error in the direction of the deviation, immediately followed by a gradual correction of the error, and an after effect (AE) in the opposite direction after prisms removal, the hallmark of prisms adaptation (PA). Several sensorimotor effects are also produced by PA on proprioceptive, visual and visuo-proprioceptive frames of reference, the latter being called total aftereffect shift (TS) of prism adaptation. Yet, after more than one century, we face a puzzling result: while pointing under prisms exposure, people rapidly achieve an optimal performance and reduce their error by 100%.

Stress Assignment Errors in Surface Dyslexia: Evidence from Two Italian Patients with a Selective Deficit of the Orthographic Input Lexicon.

Surface dyslexia designates a selective impairment in reading irregular words, with spared ability to read regular and novel words, following a cerebral damage usually located in the left dominant hemisphere. In Italian language, which is regular at the segmental level, surface dyslexia is characterized by stress assignment errors. Here we report on two cases of Italian surface dyslexic patients who produced stress assignment errors, mainly in reading irregular words.

Are movements necessary for the sense of body ownership? Evidence from the rubber hand illusion in pure hemiplegic patients.

A question still debated within cognitive neuroscience is whether signals present during actions significantly contribute to the emergence of human's body ownership. In the present study, we aimed at answer this question by means of a neuropsychological approach. We administered the classical rubber hand illusion paradigm to a group of healthy participants and to a group of neurological patients affected by a complete left upper limb hemiplegia, but without any propriceptive/tactile deficits.

Far Space Remapping by Tool Use: A rTMS Study Over the Right Posterior Parietal Cortex.

Background: In previous studies, rTMS has been successfully employed to interfere with the right posterior parietal cortex (rPPC) inducing neglect-like behavior in healthy subjects. Several studies have shown that the use of tools can modulate the boundaries between near and far space: indeed when far space is reached by the stick, far space can be remapped as near.

Objective: The aim of the present study was to investigate whether once that rTMS on the rPPC has selectively induced neglect-like bias in the near space (but not in the far space), neglect can appears also in the far space when the subjects used a tool to perform the task.

Long-lasting amelioration of walking trajectory in neglect after prismatic adaptation.

In the present study we explored the effect of prismatic adaptation (PA) applied to the upper right limb on the walking trajectory of a neglect patient with more severe neglect in far than in near space. The patient was asked to bisect a line fixed to the floor by walking across it before and after four sessions of PA distributed over a time frame of 67 days. Gait path was analyzed by means of an optoelectronic motion analysis system.

Functional independence between numerical and visual space: evidence from right brain-damaged patients.

What is the relationship between numerical and visual space? Here we tried to shed new light on this debated issue investigating whether and how the two forms of representation are associated or dissociated when co-activated. We carried out a series of visual-numerical bisection experiments on a large group of right brain-damaged patients (N=32) with and without left neglect. We examined (a) the degree of association between the pathological rightward error in the bisection of numerical intervals and left neglect (experiment 1); (b) if the size of the numerical interval modulates spatial errors in bisection tasks in which numerical and visual space representations are co-activated (experiment 2).

Losing one's hand: visual-proprioceptive conflict affects touch perception.

Background: While the sense of bodily ownership has now been widely investigated through the rubber hand illusion (RHI), very little is known about the sense of disownership. It has been hypothesized that the RHI also affects the ownership feelings towards the participant's own hand, as if the rubber hand replaced the participant's actual hand. Somatosensory changes observed in the participants' hand while experiencing the RHI have been taken as evidence for disownership of their real hand.

Object-centred pseudoneglect for non-verbal visual stimuli.

The rightward spatial bias shown by left neglect patients and the small leftward bias displayed by healthy subjects (pseudoneglect) have been interpreted as phenomena sharing a common attentional imbalance mechanism. Here we investigated whether pseudoneglect, similarly as neglect, can occur in an object-centred frame of reference. Thirty healthy participants repeatedly bisected the elongated caricature of a basset hound with the head on the left and the tail on the right or viceversa.

Are drawing perseverations part of the neglect syndrome?

Unilateral neglect patients typically omit to cancel contralesional targets. Moreover, they can repeatedly cancel ipsilesional stimuli exhibiting what is termed 'perseverative behavior'. Two alternative accounts of this behavior have been proposed.

Mental number line disruption in a right-neglect patient after a left-hemisphere stroke.

A right-neglect patient with focal left-hemisphere damage to the posterior superior parietal lobe was assessed for numerical knowledge and tested on the bisection of numerical intervals and visual lines. The semantic and verbal knowledge of numbers was preserved, whereas the performance in numerical tasks that strongly emphasize the visuo-spatial layout of numbers (e.g.

Modular structure of awareness for sensorimotor disorders: evidence from anosognosia for hemiplegia and anosognosia for hemianaesthesia.

In the present paper, we shall review clinical evidence and theoretical models related to anosognosia for sensorimotor impairments that may help in understanding the normal processing underlying conscious self-awareness. The dissociations between anosognosia for hemiplegia and anosognosia for hemianaesthesia are considered to give important clinical evidence supporting the hypothesis that awareness of sensory and motor deficits depends on the functioning of discrete self-monitoring processes. We shall also present clinical and anatomical data on four single case reports of patients selectively affected by anosognosia for hemianaesthesia.

Spatial representations, distortions and alterations in the graphic and artistic production of brain-damaged patients and of famous artists.

The authors review the drawing disorders that can be observed in patients with brain damage (in particular, those with constructional apraxia and unilateral spatial neglect), the impact of brain damage on the output of professional artists, and the distortions of body image that characterise the work of many great artists, from Rubens to Lucien Freud. These different perspectives share the basic assumption that the graphic and artistic output of patients, normal subjects, and exceptionally gifted individuals may represent a window onto the neural organisation of body image.

Bisecting lines with different tools in right brain damaged patients: the role of action programming and sensory feedback in modulating spatial remapping.

In a first experiment we studied, through a line bisection task, (a) the frequency of the selective disruption of far or near space representations in a group of 28 right brain-damaged patients and (b) the effect of tool use on line bisection error in far and near space in order to clarify whether the kind of action performed by the subject influences the extension of space representation, as suggested by previous studies. In a second experiment, carried out on two neglect patients, we asked whether the representation of "near" and "far" space depends on the sensory feedback during the execution of the action or whether it is independent on sensory feedback and more related to the action programmed as a consequence of the kind of tool used. Our data show (a) that dissociations between far and near space neglect are a frequent observation in right brain damaged patients and that most of these patients are able to recode space representations when tools change the spatial relation between the agent's body and the target object; (b) that spatial remapping can be elicited by the kind of action associated to the tool used and by the sensory feedback (either visual or proprioceptive) available during the execution of the task.