Optokinetic therapy improves text reading in patients with hemianopic alexia: A controlled trial (original) (raw)
Related papers
Impaired reading in patients with right hemianopia
Annals of Neurology, 2000
A left occipital stroke may result in alexia for two reasons, which may coexist depending on the distribution of the lesion. A lesion of the left lateroventral prestriate cortex or its afferents impairs word recognition ("pure" alexia). If the left primary visual cortex or its afferents are destroyed, resulting in a complete right homonymous hemianopia, rightward saccades during text reading are disrupted ("hemianopic" alexia). By using functional imaging, we showed two separate but interdependent systems involved in reading. The first, subserving word recognition, involved the representation of foveal vision in the left and right primary visual cortex and the ventral prestriate cortex. The second system, responsible for the planning and execution of reading saccades, consisted of the representation of right parafoveal vision in the left visual cortex, the bilateral posterior parietal cortex (left > right), and the frontal eye fields (right > left). Disruption of this distributed neural system was demonstrated in patients with severe right homonymous hemianopia, commensurate with their inability to perform normal reading eye movements. Text reading, before processes involved in comprehension, requires the integration of perceptual and motor processes. We have demonstrated these distributed neural systems in normal readers and have shown how a right homonymous hemianopia disrupts the motor preparation of reading saccades during text reading.
Patients with hemianopic alexia adopt an inefficient eye movement strategy when reading text
American Journal of Ophthalmology, 2006
Patients with an acquired homonymous hemianopia often adapt over a period of a few months to compensate for some of the impairments caused by their visual field defect. Changes in their eye movement patterns have been demonstrated as performance on visual tasks improves with time; however, these patients often complain of persistent text reading problems. Using a video-based eye-movement tracking system, we investigated the text reading behaviour of patients with established hemianopic alexia (>6 months post deficit), a condition affecting left-to-right readers, with a homonymous field defect that encroaches into their right foveal/parafoveal visual field. Word-based analyses of text reading are standard in experiments involving normal readers, but this is the first time these methods have been extended to patients with hemianopic alexia. Using this method, we compared the patients' reading scanpaths to those generated by normal controls reading the same passages, and a random model generated by matching the patients' eye movement data to random permutations of the text they read. We demonstrate that patients adopt an inefficient reading strategy, fixating to the left of the preferred viewing location of words of four letters and longer. Fixating to the left of the normal preferred viewing location not only results in less of the fixated word being processed by the language system; ensuing fixations are also more likely to land within the same word (a refixation). It is this refixation rate that is the main factor in slowing reading times in these patients. Our data suggests that patients are able to extract some useful visual information from text to aid the planning of reading scanpaths as their behaviour differs critically from the random model. Potential reasons for this patient group failing to produce an effective reading strategy are discussed.
Treatment of reading impairment after stroke
Current Opinion in Neurology, 2008
Purpose of review Reading impairments after left or right hemisphere stroke are common yet receive little attention from clinicians and therapists. In this review, we focus on the classification of acquired alexia and the current theory and practice underlying the rehabilitation of this diverse set of disorders.
Read-Right: a “web app” that improves reading speeds in patients with hemianopia
Journal of Neurology, 2012
Effective behavioral therapies exist for patients with brain injury. The main issue is one of access. Can the internet be used as a resource so that suitable patients can build up enough practice to improve? We tested this hypothesis using a web-based application for patients with a right-sided hemianopia causing slow text reading. We studied 33 patients aged 26-81 years who fitted the entry criteria and accessed the therapy website between May 2010 and December 2011, in a longitudinal cohort study. The therapy consisted of reading animated, laterally scrolling text whose content and form was selected by the patients. Reading speeds on static text (main outcome) were assessed after every 5-h period of practice had been accrued. Statistical analysis was carried out using a repeated measures ANOVA. Read-Right therapy produced significant improvements in text reading speeds at all time points with a clear dose effect: 10 % at 5 h, 20 % at 10 h, 39 % at 15 h and 46 % at 20 h. Sub-analyses demonstrated that this was unlikely to be due to either multiple exposure to the testing materials (familiarity) or to the simple passage of time. This is the first example of a clinically proven therapy being delivered effectively to stroke patients over the internet. As therapists' time is more limited than patients' capacity to improve, carefully designed, web-based resources like Read-Right represent a realistic way of delivering a sufficient therapy dose to patients so they can obtain clinically meaningful improvements.
Rehabilitation of hemianopic dyslexia: are words necessary for re-learning oculomotor control?
Brain, 2008
Unilateral homonymous visual field disorders after brain damage are frequently associated with a severe impairment of reading, called hemianopic dyslexia. A specific treatment method has been developed which allows patients to regain sufficient reading performance by re-learning eye-movement control in reading through systematic oculomotor practice. However, it is still unclear whether the treatment effect associated with this training procedure critically depends on using text material. We therefore evaluated the effectiveness of systematic oculomotor training with non-text material (Arabic digits) in comparison with conventional oculomotor training using text material (words) in 40 patients with unilateral homonymous visual field disorders and hemianopic dyslexia. Non-text training was found to be as effective as conventional text training in improving reading performance and associated eye-movements in these patients. Our results suggest that using words is not critical to the treatment effect of this training procedure. Thus, lexical-semantic processes seem not to be necessary for re-learning eye-movement control in hemianopic dyslexia.
How do hemianopic patients read?
Neurology
Eye movements serve vision by placing the image of an object of regard on the fovea of each retina and by preventing slippage of images on the retina. The brain employs two modes of ocular motor control: Fast eye movements (saccades) and smooth (slow) pursuit eye movements (SPEM). Five distinct ocular motor systems are utilized to achieve clear vision. Four of the systems generate conjugate movements (version), one system generates dysjunctive horizontal movements (vergence). 1. Saccades achieve rapid fixation of targets that fall on the extrafoveal retina by moving the eyes at peak velocities up to 700 deg/sec. Quick nystagmus phases are also saccades generated by the same neurons in pons and midbrain. The saccadic system arises mainly from the frontal eye field (FEF, area 8). The FEF projects directly to the pontine (PPRF, horizontal) and mesodiencephalic (riMLF, vertical) saccadic generating centers, this pathway decussating at the junction of the midbrain and pons. Saccades from the occipital lobe get direct access to the brainstem via the superior colliculus (SC). There is another third-indirect-pathway through the caudate nucleus, the pars reticulata of the substantia nigra and the SC; this pathway is tonically inhibitory to the SC. The cortex initiates and voluntarily controls saccadic eye movements, the control signals, however, are generated in brainstem supranuclear gaze centers (PPRF, riMLF). Vertical gaze-as a general principle-is mediated by bilateral circuits. 2. ~mooth oursuit mair~tains fixation of slowly moving target. The SPEMsystem starts where vision is primarily received (area 17) responding to slippage of an image near the fovea. Axons from the striate cortex project to extrastriate visual areas (middle temporal visual area MT, medio-superior temporal area MST, posterior parietal region), from here ipsilaterally to the dorsolateral pontine nuclei, then to the flocculus and the dorsal vermis of the cerebellum, then to the oculomotor nuclei: Concept of an ipsilateral parietooccipito-ponto-cerebellar pathway. It is interesting that this pathway unlike the saccadic pathway goes from the brainstem to the cerebellum and then back to the brainstem, whereas the saccadic pathway goes directly from cerebral hemisphere to brainstem. 3. The vestibulo-ocular reflex (VOR) prevents retinal slip during head movements by moving the eyes at the same velocity as the head, but in the opposite direction-the VOR keeps gaze stable relative to the world. Visual cancellation of the VOR occurs when an object is pursued with the head-head and eye moving simultaneously toward the target. 4. Ootokinetic smooth eye movements aid vestibular eye movements by stabilizing images on the retina during constant velocity or very low frequency head movements, when the VOR does not function optimally. 5. The veraen~ system achieves binocular vision by generating dysjunctive eye movements that align the two foveas on an object as it approaches the head; the vergence system is also responsible for maintaining stereoacuity. One of the most complex type of eye movements are the frequently occuring combined vergent-saccadic movements; it is not yet clearly understood how the underlying control signal is generated. Additionally the cerebellum mediates control of ocular motor systems participating in four major ocular motor functions: a) stabilization of images upon the retina during smooth pursuit, b) regulation of the duration of the vestibulo-ocular responses; the time required for the VOR to discharge is measured by the VOR time constant, c) regulation of saccadic amplitude, and d) repair of ocular dysmetria.
How Does iReadMore Therapy Change the Reading Network of Patients with Central Alexia
Central alexia (CA) is an acquired reading disorder co-occurring with a generalized language deficit (aphasia). The roles of perilesional and ipsilesional tissue in recovery from poststroke aphasia are unclear. We investigated the impact of reading training (using iReadMore, a therapy app)ontheconnectionswithinandbetweentherightandlefthemisphereofthereadingnetworkofpatientswithCA.Inpatientswithpurealexia, iReadMore increased feedback from left inferior frontal gyrus (IFG) region to the left occipital (OCC) region. We aimed to identify whether iReadMore therapy was effective through a similar mechanism in patients with CA. Participants with chronic poststroke CA (n ϭ 23) completed 35 h of iReadMore training over 4 weeks. Reading accuracy for trained and untrained words was assessed before and after therapy. The neural response to reading trained and untrained words in the left and right OCC, ventral occipitotemporal, and IFG regions was examined using event-related magnetoencephalography. The training-related modulation in effective connectivity between regions was modeled at the group level with dynamic causal modeling. iReadMore training improved participants' reading accuracy by an average of 8.4% (range, Ϫ2.77 to 31.66) while accuracy for untrained words was stable. Training increased regional sensitivity in bilateral frontal and occipital regions, and strengthened feedforward connections within the left hemisphere. Our data suggest that iReadMore training in these patients modulates lower-order visual representations, as opposed to higher-order, more abstract representations, to improve word-reading accuracy.
Visual exploration training is no better than attention training for treating hemianopia
Brain, 2010
Patients with homonymous visual field defects experience disabling functional impairments as a consequence of their visual loss. Compensatory visual exploration training aims to improve the searching skills of these patients in order to help them to cope more effectively. However, until now the efficacy of this training has not been compared to that of a control intervention. Given that exploration training uses the visual search paradigm, which is known to require visual attention, in this study the efficacy of the technique was compared with training that requires visual attention but not exploration. Participants completed either exploration training (n = 21), or attention training followed by exploration training (n = 21). Assessment of the visual field, visual search, reading and activities of daily living were performed before and after each intervention that the participants completed. The results revealed that both the exploration training and the attention training led to significant improvements in most of the visual tasks. For most of the tasks exploration training did not prove superior to attention training, and for reading both types of intervention failed to yield any benefits. The results indicate that attention plays a large role in the rehabilitation of homonymous visual field defects.
Neurocase, 2020
Patients with pure alexia have major difficulties in reading aloud. However, they often perform above chance level in reading tasks that do not require overt articulation of the target word-like lexical decision or semantic judgment-a phenomenon usually known as "implicit reading." There is no agreement in the literature on whether implicit reading should be attributed to relative sparing of some left hemisphere (LH) reading centers or rather to signs of compensatory endeavors by the right hemisphere (RH). We report the case of an 81-year-old patient (AA) with pure alexia due to a lesion involving the left occipital lobe and the temporal infero-mesial areas, as well as the posterior callosal pathways. Although AA's reading was severely impaired and proceeded letter by letter, she showed an above-chance-level performance for frequent concrete words in a tachistoscopic lexical decision task. A structural disconnectome analysis revealed that AA's lesion not only affected the left occipital cortex and the splenium: it also disconnected white-matter tracts meant to connect the visual word-form system to decision-related frontal areas within the LH. We suggest that the RH, rather than the LH, may be responsible for patient AA's implicit reading.