Alessio Facchin

Aftereffect induced by prisms of different power in the rehabilitation of neglect: A multiple single case report

OBJECTIVES Prism Adaptation (PA) is a technique used in the rehabilitation of unilateral spatial neglect. Several researchers have reported positive results on a number of tasks, but negative outcomes have also been reported. These conflicting results could be due to the use of prisms of different power. The aim of this study was to investigate the amplitude and duration of the aftereffect induced by prisms of different power by different measures in a series of single cases of neglect. METHODS Five neglect patients and ten control subjects participated in the study. Prism adaptation was evaluated with Subjective Straight Ahead (SSA), Open-Loop Pointing (OLP) and Line Bisection (LB) tasks, immediately before prism adaptation, immediately after, and 10/60 minutes after prism adaptation. The procedure was repeated with prisms of 5, 10 and 20 prismatic diopters (Δ). RESULTS The OLP task provided the most sensitive measures for the size of the aftereffect. The 20Δ prism proved to be most effective in inducing an immediate aftereffect, while the aftereffect of the 5Δ prism seemed to last longer. CONCLUSION We showed that the prism power and the task used for assessing PA effect are relevant variables to be consider in clinical practice of neglect rehabilitation.

Neuropsychological Evidence of High-Level Processing in Binocular Rivalry

One of the most fascinating and challenging ques-tions of cognitive neurosciences is what are the neuralcorrelatesofconsciousness. Wetrytoanswerthisques-tionbystudyingpatientshavingadissociationbetweenconsciousperceptionand sensory stimulation.We studied patients with right brain damage (RBD)involving unilateral spatial neglect (USN). USN fol-lows a lesion in the right frontoparietal cortex and in-volveslack of consciousnessof visual stimuli (or partsof them) presented in the contralesional (left) side ofspace, without any sensory deficit [5]. Even if patientsare unable to describe the left side of a stimulus, theyshowbehaviouralevidenceofpreservedvisualanalysiswhen tested implicitly [4].Tostudyvisualconsciousnessinneglectpatients,weusedbinocularrivalry. Thisinvolvesshowingdifferentimages to the two eyes. Instead of seeing both imagessimultaneously, neurologically normal people see oneimage for a few moments with no trace of the other,then they see the other image for a few moments withnotraceofthefirst, thentheysee thefirst again,andsoon for as long as they care to look. This phenomenonexhibitsa dissociationbetweensensoryinput,whichisunchanging,andconsciousness,whichchangescontin-uously.Therearetwoopposingexplanationsofbinocularri-valry: low-level and high-level theories [8]. Blake [2]proposed that rivalry is resolved at a low level of thevisual system, in the primary visual cortex, involving

The Glare Effect Test and the Impact of Age on Luminosity Thresholds

The glare effect (GE) is an illusion in which a white region appears self-luminous when surrounded by linearly decreasing luminance ramps. It has been shown that the magnitude of the luminosity effect can be modulated by manipulating the luminance range of the gradients. In the present study we tested the thresholds for the GE on two groups of adults: young (20–30 years old) and elderly (60–75 years old). Purpose of our perspective study was to test the possibility of transforming the GE into a test that could easily measure thresholds for luminosity and discomfort glare. The Glare Effect Test (GET) consisted in 101 printed cards that differed from each other for the range of luminance ramps. Participants were assessed with GET and a battery of visual tests: visual acuity, contrast sensitivity, illusion of length perception, and Ishihara test. Specifically in the GET, participants were required to classify cards on the basis of two reference cards (solid black-no gradient; full range black to white gradient). PSEs of the GE show no correlation with the other visual tests, revealing a divergent validity. A significant difference between young and elderly was found: contrary to our original expectations, luminosity thresholds of GE for elderly were higher than those for young, suggesting a non-direct relationship between luminosity perception and discomfort glare.

Examining visual field in clinical setting in neglect patients.

In clinical setting it is sometimes difficult to disentangle severe Unilateral Spatial Neglect (USN) from Homonymous Hemianopia (HH). Due to cost and time it is not always viable to perform a computerized visual field (VF) perimetry which often is also unreliable in acute stroke patients with attentional deficits (Dersu et al., 2014). Hence, in acute phases, the simple confrontation test is used. This method to detect VF defects though is prone to the confounding effects of USN. To remedy, some authors suggested that VF confrontation test should be carried out with the patients rotating their eyes leftward or rightward by about 30 while maintaining their head position aligned with the body (Kooistra & Heilman, 1989). Another, similar, proposal has been to rotate the patients head by 30 towards the contralesional side (Vuilleumier, Valenza, Mayer, Perrig, & Landis, 1999). These techniques could be useful but only with patients without a severe attraction towards the ipsilesional space independent from their eye/head/trunk position. However, such patients are not rare. With these patients, we have tried positioning the patient with their right (or left in right neglect patients) side close to a wall with the chair/wheelchair parallel to the wall. The examiner should also be close to the wall and facing the patient (see Fig. 1). The sequence of presentation and the subdivision into quadrants could be the same as in the standard clinical examination. In our procedure, the patients is asked to keep a central fixation, on the examiners nose, throughout the test, and is presented with 10 “yes” stimuli (whereby the examinermoves their finger), and three catch trials (eliciting a “no” answer) whereby the examiner does not move their fingers. In all cases the patient has to answer whether they saw a finger moving and to indicate where. It is very important that the examiner remains motionless with their shoulders to avoid that the patient responds to a central clue. The score here reported considers only the “yes” responses, hence ranging from 0 to 10. We observed that this task is easier for USN patients because they are forced to move attention towards the left space. The use of this strategy in several cases permits to bypass USN and to show the integrity of contralesional VF. For example, patient CZ showed a severe left USN after a middle cerebral artery stroke. He was unable to inhibit a “magnetic attraction” and returned to the same right-sided objects over and over again (Bartolomeo, 2000), failing to explore the left side. We could not be sure on whether or not he was showing HH over and above USN. Rotating his head by 30 to the left and to the right did not change his performance. On the “wall” testing condition he detected 90 per cent of the stimuli on the left, clearly showing that he was not hemianopic. He also responded correctly to the three catch trials. To verify that this difference was due to excluding stimulation from the right in the “wall” condition, we also carried out the classic confrontation butwith the experimenter presenting only the left sided stimuli with their left arm still alongside the body; CZ scored 2.6 out of 10. We tested him five times over five days, replicating the same findings: on the classic confrontation test he obtained an average 1.6 out of 10 in the left VF, on the “wall” version he scored 9.2. We have used the same procedure with other 12 USN patients showing magnetic attraction to the ipsilesional side. In none of them the classic confrontational test allowed us detect whether or not their contralesional VF was intact. In 5

A comparison of prism adaptation with terminal versus concurrent exposure on sensorimotor changes and spatial neglect

ABSTRACT Prism adaptation (PA) is a technique that induces a temporary change of the alignment between different reference frames. This technique has been shown to reduce many signs of unilateral spatial neglect (USN). Two procedures of prism adaptation have been used. In concurrent exposure participants can see their arm and hand during the movement trajectory, and during terminal exposure, participants can see only the most distal few centimetres. Because the two exposures elicit different proportions of visual and proprioceptive realignment, they could present different rehabilitation efficacies. We compared these procedures in 12 USN patients and 12 healthy participants who performed one session of PA with concurrent exposure and one session with terminal exposure. We compared the effects of the two exposure types on sensorimotor outcomes (visual subjective straight ahead, proprioceptive subjective straight ahead, open loop pointing, and error correction during exposure) and neglect outcomes. We found no significant differences in the effects of the two exposure types on sensorimotor performance of patients and controls, nor on patients’ neuropsychological outcomes. Compared with controls, USN patients showed a significant rightward bias in visual subjective straight ahead pre-adaptation, a slower rate of error correction during prism exposure, and some evidence that visual and proprioceptive shift could be influenced by their neglect. Based on these results, we recommend that prism adaptation be conducted with concurrent exposure for easiness of execution.

The Reliability of the DEM Test in the Clinical Environment

The developmental eye movement (DEM) test is a practical and simple method for assessing and quantifying ocular motor skills in children. Different studies have previously assessed the reliability of the DEM test and they have generally found high values for vertical and horizontal time, whereas those for Ratio and Errors were medium and low, respectively. In the second application of test were found an improvement in performance in all subtests. Our aim was to evaluate the reliability of the DEM test using seconds and percentile scoring and looking in depth at the improvement in performance when the test is repeated. We tested the reliability of the DEM test on a group of 115 children from the 2nd to the 5th grade using different statistical methods: correlations, ANOVA, limits of agreement for results expressed in seconds and as percentile scoring and pass-fail diagnostic classification. We found high reliability with excellent values for vertical and adjusted horizontal time, medium-to-high for ratio and medium for errors. We have re-confirmed the presence of a significant improvement of performance on the second session for vertical time, horizontal time and ratio. The stability of binary classification of Pass–Fail criteria appears to be medium. We found high reliability for the DEM test when compared with the published results of other research but the improvement of performance, the learning effect was still present, but at a lower level than previously found. With the awareness of these limitations the DEM test can be used in clinical practice in evaluating performance over time.