Developmental neglect dyslexia in a Hebrew-reading child

This paper describes for the first time a detailed study of a child with neglect dyslexia. NT is 10-year-old child, with left word-based neglect dyslexia, without clinical signs of visuo-spatial neglect. Since he is a native speaker of Hebrew, which is read from right to left, his neglect dyslexia manifests in omissions and substitutions of final letters. He is severely impaired in single words, with 96% of his errors being omissions and substitutions of final letters. When presented with more than one word, in word pairs, sentences or text, he neglects the left part of each word, but never omit whole words on the left side of the page. His reading improves considerably when the same word is presented vertically or when manipulations are done to shift his attention to the left--with coloured final letters, flashing light, or tapping his finger to the left of each word. NT's neglect dyslexia is very selective, with good reading of numbers and symbols, and even good performance on letter sequences when no reading is required. A dissociation is also detected between his impaired reading due to neglect dyslexia and his normal performance on conventional clinical tests of general visual neglect visual of line, object and letter cancellation, line bisection, object drawing and copying. His neglect dyslexia seems to be developmental as no abrupt onset is reported.     

An investigation of attentional contributions to visual errors in right "neglect dyslexia"

One type of error that is sometimes produced by patients with acquired dyslexia is the substitution of an orthographically similar word with letters that overlap the target either in early or late letter positions. When such errors affect the left sides of words, they are usually produced by patients with focal right hemisphere lesions who typically show evidence of left neglect in non-reading tasks. This pattern has thus been termed “neglect dyslexia”. When the right sides of words are affected, however, patients frequently fail to show any signs of neglect in tasks other than reading. This study presents results from a patient with left hemisphere damage, and a very clear pattern of right “neglect” errors in reading, on a series of tasks testing attentional and imagery processes. Given the magnitude and consistency of the patient's reading errors, there was little evidence that these errors resulted from inattention to the right side of space or to the right side of an internally generated visual image. It is argued that the positional errors result from an impairment to an abstract ordinal code with graded activation of letter positions from first to last, and that this code is specific to tasks involving orthographic representations.     

Callosal neglect

BACKGROUND: According to the interhemispheric inhibition model of neglect, the uninjured hemisphere inhibits (via the corpus callosum) the injured hemisphere but the injured hemisphere can no longer inhibit the opposite hemisphere, which becomes hyperactive and produces an ipsilesional attentional bias. Alternatively, according to the compensation hypothesis, the uninjured hemisphere helps compensate for the damaged hemisphere, which is impaired in directing attention to contralateral stimuli. If the inhibition model of neglect is correct, callosal disconnection should reduce neglect. If the compensation model is correct, however, it may increase or induce neglect. PATIENT: A 32-year-old woman, at age 14 years, developed a right frontal astrocytoma and was treated with surgery and radiation but had a cardiopulmonary arrest secondary to aspiration. Subsequent imaging studies revealed damage to the frontal, parietal, and occipital regions of the right hemisphere and damage to the temporal region of the left hemisphere. After discharge, she was able to return to school and drive a car, without any evidence of neglect. About 10 years later, she developed complex partial and atonic seizures that were multifocal and medically intractable. She underwent a complete section of her corpus callosum at age 31 years. RESULTS: One year after the callosal section, she demonstrated (1) diminished spontaneous saccades to the left, hypometric leftward saccades, and left gaze impersistence; (2) left arm hemispatial limb akinesia; (3) unilateral spatial neglect; and (4) motor and cognitive impersistence. CONCLUSION: In patients with right hemisphere injury, callosal section may induce or enhance motor-intentional deficits and hemispatial neglect.     

Recovery of oculo-motor bias in neglect patients after prism adaptation

Patients with "neglect dyslexia" usually make errors in reading the left part of words and non-words. It has been shown that "neglect dyslexia" can improve following a short period of adaptation to wedge prisms [Neuropsychologia 40 (2002) 718], however the mechanisms underlying this amelioration are still unknown. The present study evaluated the effect of prism adaptation (PA) on ocular scanning behaviour of neglect dyslexia patients by investigating: (a) the first saccade landing position during reading a letter string and (b) the distribution of fixation time as a function of the side of oculo-motor exploration of words and non-words. This in order to assess whether possible changes (in reading performance) after the adaptation might be attributed to a resetting of the oculo-motor system. Eye movements' performances were recorded before and after a single prismatic exposure on right brain-damaged patients with left hemispatial neglect and "neglect dyslexia". The results obtained in Experimental neglect patients before and after PA were then compared to that of control neglect patients, who were wearing goggles with neutral lenses. Moreover, in order to provide normative data on ocular scanning behaviour during letter string reading, neurologically healthy subjects were also studied. Following a single session of prism adaptation, the results showed, in the Experimental neglect patients, an improvement of neglect dyslexia, an increased left-sided exploration of the letter string and an increased amplitude of the first left-sided saccade. In contrast, in the Control neglect patients, neglect dyslexia as well as the oculo-motor system behaviour, remained the same after the use of goggles with neutral lenses. These findings demonstrate that the beneficial effect induced by a single prismatic adaptation may be conceived as a complex interaction between sensory stimulation and a resetting of oculo-motor system.     

Reading direction and spatial neglect

Many American and European investigators have reported that hemispatial neglect is more frequent and more severe after right than left hemisphere lesions. This hemispheric asymmetry may be due to biological asymmetries, learned behavior, or both. Readers of European languages, unlike readers of Semitic languages, scan from left to right. Learned rightward scanning may increase the unilateral neglect associated with right hemisphere lesions and reduce the severity of neglect associated with left hemisphere lesions. To learn if hemispheric asymmetries of neglect are influenced by learned scanning behavior, we used line bisection and cancellation tasks to study patients with unilateral stroke who read only a Semitic or European language before the age of fifteen. We found that independent of reading direction, unilateral neglect was more commonly associated with right than left hemisphere lesions. After right hemisphere damage right to left readers bisected lines closer to center than left to right readers, but on the cancellation test readers of European languages did not perform differently than readers of Semitic languages. These findings suggest that whereas learned scan direction may influence the severity of neglect when measured by line bisection, these learned directional scans cannot fully account for the observed hemisphere asymmetries of neglect. They also suggest that the line bisection test is more influenced by the direction of scanning than is the cancellation test.     

The effect of syntax on reading in neglect dyslexia

Individuals with text-based neglect dyslexia omit words on the neglected side of the sentence or text, usually on the left side. This study tested whether the syntactic structure of the target sentence affects reading in this type of neglect dyslexia. Because Hebrew is read from right to left, it enables testing whether the beginning of the sentence and its syntactic properties determine if the final, leftmost, constituent is omitted or not. The participants were 7 Hebrew-speaking individuals with acquired left text-based neglect dyslexia, without syntactic impairments. Each participant read 310 sentences, in which we compared 5 types of minimal pairs of sentences that differed in the obligatoriness of the final (left) constituent. Complements were compared with adjuncts, obligatory pronouns were compared with optional resumptive pronouns, and the object of a past tense verb was compared with the object of a present tense verb, which can also be taken to be an adjective, which does not require an object. Questions that require a verb were compared with questions that can appear without a verb, and clauses that serve as sentential complements of a verb were compared with coordinated clauses, which are not required by the verb. In addition, we compared the reading of noun sequences to the reading of meaningful sentences, and assessed the neglect point in reading 2 texts. The results clearly indicated that the syntactic knowledge of the readers with neglect dyslexia modulated their sentence reading. They tended to keep on reading as long as the syntactic and lexical-syntactic requirements of the sentence had not been met. In 4 of the conditions twice as many omissions occurred when the final constituent was optional than when it was obligatory. Text reading was also guided by a search for a “happy end” that does not violate syntactic or semantic requirements. Thus, the syntactic structure of the target sentence modulates reading and neglect errors in text-based neglect dyslexia, suggesting that the best stimuli to diagnose mild text-based neglect dyslexia are sentences in which the leftmost constituent is optional, and not required by syntax. Another finding of this study is dissociation between neglect dyslexia at the text and at the word levels. Two of the participants had neglect dyslexia at the text level, manifested in omissions of words on the left side of text, without neglect dyslexia at the word level (namely, without omissions, substitutions, or additions of letters on the left side of words).     

Cueing strategies in neglect dyslexia

A single case study is reported of a patient with left neglect dyslexia after a right hemisphere stroke. The effectiveness of two cueing strategies in improving her single word reading was compared, a variation of the commonly used visuo-motor method and the recently advocated non-visual spatio-motor cueing technique. Results demonstrated the success of both strategies in reducing neglect dyslexic errors but showed qualitative differences in the processes involved. Only the visuo-motor strategy was associated with continued improvements in reading throughout the intervention period. Furthermore, the visuo-motor cueing technique showed gains still evident at 18 months post-treatment, suggesting clinically significant improvement may be mediated by visual aspects of cueing-based intervention for reading. The results are interpreted in terms of the efficacy of non-verbal attentional cues on a putative graphemic analysis system. Several practical considerations for the remediation of neglect in routine clinical settings are also discussed.     

Left hemispatial neglect with a splenial lesion

ABSTRACT

With injury of the anterior two-thirds of the corpus callosum, each hemisphere’s attentional bias to contralateral hemispace becomes manifest with each hand deviating ipsilaterally during line bisection tasks. Patients with infarctions in the right posterior cerebral artery distribution with occipital and splenial damage can also exhibit spatial neglect. The goal of this report is to learn the role of the splenium of the corpus callosum in mediating visuospatial attention. A right-handed woman with Marchiafava-Bignami disease and damage to the splenium of her corpus callosum without evidence of a mesial frontal, parietal, or occipital injury was assessed for spatial neglect with line bisections. When bisecting lines in her left hemispace with her right hand, she deviated to the right, but revealed no major deviations when the line was place in the midline, in right hemispace, or when bisecting lines with her left hand. This patient provides evidence that damage to the splenium can induce a special form of asymmetrical spatial neglect. This asymmetry might be related to the disconnected right hemisphere’s ability to allocate attention to both right and left hemispaces with the disconnected left hemisphere’s ability to allocate attention to the right but not left hemispace.     

Is there a correlation between motor neglect and unilateral sensory neglect

Similarities between motor neglect and unilateral sensorial neglect are so striking that their mechanisms are likely to be almost the same. As the attentional interpretation is no longer possible for motor neglect, and the intentional interpretation may be dismissed in man because of the loss of automatic movements, the psychological interpretation must be abandoned. A purely physiological hypothesis is put forward for motor neglect. When applied to unilateral neglect, it suggests that sensorial signals treated by the right hemisphere do not reach a significant functional level. In such case, the left hemisphere assumed to be dominant for awareness of body and space would receive from the right hemisphere a message interpreted as nul and would neglect information coming from the left.     

Double dissociation between unilateral neglect and anosognosia

We report two patients presenting with a subacute right hemisphere stroke. These cases demonstrate a double dissociation between unilateral neglect and anosognosia for hemiplegia. The first patient suffered from a severe left hemiplegia associated with severe and persisting unilateral neglect. He appeared fully aware of his motor impairment. The second patient had a severe left hemiplegia, without any major sign of unilateral neglect on clinical tests nor on behavioural assessment. Nevertheless, he presented a severe and sustained anosognosia for hemiplegia. These case reports support the assumption that anosognosia and unilateral neglect, although they are frequently associated, may rely on independent mechanisms.     

Auditory neglect.

Auditory neglect was investigated in normal controls and in patients with a recent unilateral hemispheric lesion, by requiring them to detect the interruptions that occurred in one ear in a sound delivered through earphones either mono-aurally or binaurally. Control patients accurately detected interruptions. One left brain damaged (LBD) patient missed only once in the ipsilateral ear while seven of the 30 right brain damaged (RBD) patients missed more than one signal in the monoaural test and nine patients did the same in the binaural test. Omissions were always more marked in the left ear and in the binaural test with a significant ear by test interaction. The lesion of these patients was in the parietal lobe (five patients) and the thalamus (four patients). The relation of auditory neglect to auditory extinction was investigated and found to be equivocal, in that there were seven RBD patients who showed extinction, but not neglect and, more importantly, two patients who exhibited the opposite pattern, thus challenging the view that extinction is a minor form of neglect. Also visual and auditory neglect were not consistently correlated, the former being present in nine RBD patients without auditory neglect and the latter in two RBD patients without visual neglect. The finding that in some RBD patients with auditory neglect omissions also occurred, though with less frequency, in the right ear, points to a right hemisphere participation in the deployment of attention not only to the contralateral, but also to the ipsilateral space.     

Right-sided neglect in a left-hander: evidence for reversed hemispheric specialization of attention capacity

Severe hemi-spatial neglect, anosognosia, contralateral hypokinesia, aprosodia, and visual-spatial constructive difficulties--typically seen in right-handers with right hemisphere lesions--were observed in a left-handed patient with an acute left frontal cortical and subcortical infarct. There was no evidence of accompanying aphasia and the neglect syndrome gradually resolved over a 2-week period. The assumption by the left hemisphere of a classic right hemisphere attention, visuo-spatial and prosodic superiority may represent a case of reversed hemispheric specialization.     

Object-based versus object-centred neglect in reading words

Neglect dyslexia is a reading disorder which affects the identification of portions of words or sentences and is typically due to right-brain damage. Caramazza and Hillis (1990a, b) proposed a model of representation of words whereby various patterns of neglect dyslexia are attributed to selective impairment to the different forms of representation. According to the model, patients with first and second level deficits will "neglect" those parts of horizontally presented words that fall on one side of the retina, or on one side of the string centre, respectively, but will read vertically presented words without errors. A patient with a third level deficit will neglect letters at the beginning of the word irrespective of whether they fall on the right or left half of the retina, or on the right or the left of the word centre. In the present paper I describe an atypical pattern of neglect errors that is not easily explicable by this model and is better interpreted as an object-based neglect within an ego-centred frame of reference.     

Brain stimulation procedures for treatment of contralesional spatial neglect

The application of brain stimulation techniques for modulation of cortical excitability changes underlying spatial neglect following right-brain-damage has been the first application of brain stimulation in the rehabilitation setting. Several factors concur in making neglect a prototype of cognitive disorders that can be modulated by brain stimulation: 1) neglect is highly lateralized deficit, 2) neglect is a network disorder in which lesion of a network node impacts affects excitability of intrahemispehric and interhemispheric connections, and 3) lesions of the right hemisphere, the most frequent cause of neglect, are associated with a transcallosally mediated increase of facilitation of the left hemisphere more frequently than are lesions of the left hemisphere associated with right hemisphere facilitation. We review the main applications of TMS for modulation of neglect disorder and we discuss the different potentialities of inhibition of the unaffected and facilitation of the affected hemisphere. Moreover, we suggest potential interactions of TMS with other behavioral techniques in the rehabilitation setting.     

The nature of unilateral neglect in the olfactory sensory system

This study investigated two major theories of unilateral neglect utilizing the ipsilaterally innervated olfactory sense. The sensory theory states that unilateral neglect is due to a diminished or attenuated sensory input. The representational theory states that unilateral neglect is due to a disordered internal representation, which is not dependent on sensory input. Results of the study revealed that right hemisphere lesion patients with left unilateral neglect failed to respond to their left contralateral nostril on olfactory double simultaneous stimulation, consistent with the representational theory because the left nostril has no direct sensory input to the right hemisphere.     

The assessment of visuo-spatial neglect after acute stroke.

Forty four consecutive patients with acute hemispheric stroke and forty seven elderly controls with no neurological disease were assessed for visuo-spatial neglect, using a modified neglect test battery. Neglect was found to be equally common in patients with right hemisphere and left hemisphere stroke three days after stroke (72% versus 62%). It was more severe in those with a right hemisphere stroke and resolved more frequently in those with a left hemisphere stroke. The battery was validated against an occupational therapist's assessment of neglect on self-care tasks. The inter-observer reliability was good and it was possible to monitor changes over time with the battery.     

Reading aloud and lexical decision in neglect dyslexia patients: a dissociation

This study investigated the dissociation between reading aloud and lexical decision in six Italian right-brain-damaged patients with left neglect dyslexia. Patients were requested to perform two tasks: (a) reading aloud and lexical decision on monomorphemic words of different frequencies and non-words with different degrees of similarity to real words (Experiment 1); (b) reading aloud and lexical decision on morphologically complex (suffixed) derived words and morphologically complex (suffixed) non-words (Experiment 2). The patients' performance on lexical decision was compared to that of a group of matched control subjects. Patients showed left neglect dyslexia in the reading aloud task, but had a normal level of performance in the lexical decision task. Furthermore, patients were affected by the same morpho-lexical variables that influence lexical decision in normal subjects, suggesting a largely preserved morpho-lexical processing of written letter strings, as assessed by the task of lexical decision. The mechanisms underlying the preservation of lexical decision in patients with left neglect dyslexia are discussed in the light of dual route models of reading.     

Representational neglect in "invisible" drawing from memory

We describe the case of a patient with right hemisphere damage and left unilateral neglect. The patient was asked to draw from memory common objects, either with or without visual feedback. In the conditions without visual feedback the patient was either blindfolded or he made “invisible” drawings using a pen with the cap on, the drawings being recorded with carbon paper underneath.Results showed more neglect without than with visual feedback, contrary to previously published cases. This patient's pattern of performance may result from the contribution of a deficit of spatial working memory. Alternatively or in addition, the patient, who was undergoing cognitive rehabilitation for neglect, may have found easier to compensate for his neglect with visual feedback, which allowed him to visually explore the left part of his drawings.     

Hemispheric asymmetry in neglect produced by unilateral lesions of dorsomedial prefrontal cortex in rats

Unilateral lesions of the medial precentral prefrontal cortex produce severe polymodal neglect which reaches a stable level of recovery over 3 to 4 weeks. Previous research has indicated that neglect is produced by unilateral destruction of this region in either hemisphere, but that the nature of the neglect produced is dependent on the hemisphere damaged. The present study is a further examination of behavioral laterality produced by this unilateral destruction. The results indicated that destruction of medial precentral cortex in the left hemisphere (n = 12) produced severe contralateral multimodal neglect of visual, somatosensory, and auditory stimuli. Identical destruction in the right hemisphere (n = 18) also produced severe neglect, but unlike the left hemisphere operates which always demonstrated contralateral neglect, there were two distinct populations of right hemisphere operates. These subjects demonstrated either ipsilateral neglect or a "switching" response pattern characterized by the initial demonstration of contralateral or ipsilateral neglect and then, during the course of recovery, severe neglect on the opposite body side. Histological analysis indicated that the left and right hemisphere lesions were equivalent, as were the lesions in the two behavioral subcategories of right hemisphere operates. Operated controls (n = 12) did not demonstrate long-standing neglect or this switching pattern. The behavioral laterality observed following unilateral destruction of medial precentral prefrontal cortex is discussed in relationship to the anatomical and neurochemical asymmetries which have been demonstrated in this cortical region.