Influence of script direction on word processing modes in left and right visual fields.

Word processing in left (LVF) and right (RVF) visual fields may be affected by left hemisphere activation during reading and by script direction. We evaluated the effect of script direction by presenting words in left-to-right (French) and right-to-left (Hebrew) scripts to bilingual French participants. Words of different lengths were presented in the LVF and the RVF in a naming task. Results showed (1) a stronger word length effect in the LVF than in the RVF in French, and no difference of word length effect between LVF and RVF in Hebrew; (2) a first-letter advantage only in the LVF in French and in the RVF in Hebrew, showing an effect of script direction on letter processing; and (3) a stronger advantage of external over internal letters in words presented in the LVF than in the RVF for both languages, showing a left hemisphere influence on letter activation. Thus, script direction and left hemisphere activation may affect different processes when reading words in LVF and RVF. Selective attention may orient and redistribute a processing "window" over the letter string according to script direction, and the modulation of attentional resources is influenced by left hemisphere activation.

Environmental script affects lateral asymmetry of word recognition: A study of French-Hebrew bilinguals tested in Israel and in France.

A written word is identified more easily when it is presented in the right than in the left visual field. This right visual field superiority (RVFS) may be explained by the left hemisphere's role in reading and by reading direction in left-to-right scripts. However, the comparison of left-to-right and right-to-left scripts had not resulted in systematic differences. It had also been found that the linguistic environment has an effect on visuospatial bias. We hypothesized that the linguistic environment might also affect RVFS. In an identification task, French and Hebrew words were presented in each visual field to four groups of 24 neurologically healthy participants, all of whom read French and Hebrew as a first or second language: native French speakers in France, native French speakers in Israel, native Hebrew speakers in Israel, and native Hebrew speakers in France. Results showed a greater RVFS with French than with Hebrew words in all groups except the native Hebrew speakers in Israel. Thus, at least for native Hebrew speakers, the country where participants lived also had an effect on the differential RVFS between languages, suggesting an effect of environmental script or reading practice.

Differential hemispheric modulation of preparatory attention.

Preparatory attention (PA) is the ability to allocate attention to a stimulus prior to its occurrence and is a crucial component of attentional control. We investigated the role of brain hemispheres in PA using an experimental test in which normal participants responded to a target that could appear in the right or the left visual fields, thus projecting to the left or the right hemispheres, while ignoring a central distractor that could appear in the preparatory phase preceding the target. This experimental test measures the ability of participants to modulate PA directed to a target location when the probability of a distractor occurrence varies across three blocks of trials (0%, 33%, 67%). The competition between distractors and target for PA should produce slower response times when the probability of distractors is high. Three experiments were conducted varying the temporal predictability of the target occurrence within a trial (high predictability in Experiments 1 and 3, and low predictability in Experiment 2), and the task used (location in Experiments 1 and 2, and detection in Experiment 3). We found that the modulation of PA by the expected probability of events was different in each visual field/hemisphere. Whereas the left hemisphere PA was influenced by the mere probability of events in each block of trials, the right hemisphere PA was mainly influenced by events with high temporal predictability. These results suggest that each hemisphere uses a different strategy to modulate PA when directed to a target location at the perceptual level of visual processing.

Dissociation between Selecting and Orienting Attentional Reading Deficits: A Study in Adults with Epilepsy.

Word reading requires a range of spatial attention processes, such as orienting to a specific word and selecting it while ignoring other words. This study investigated whether deficits of these spatial attention processes can show dissociations after hemispheric lesions. Thirty-nine patients with left or right focal epilepsy and 66 healthy participants had to read aloud four-letter words presented in the left and right visual hemifields. There were three successive blocks of presentation: in the unilateral block, a single word was presented in one of the visual hemifields; in the bilateral block, two words were presented simultaneously, one in each visual hemifield; in the cued block, two words were also presented, but only the cued word had to be reported. Twenty-one patients, twelve with a left and nine with a right hemisphere lesion, showed a word reading deficit. Four had specific difficulties in the cued block, suggesting an attentional selection reading deficit. Twelve patients had an asymmetric reading deficit, suggesting an attention orientation or a visual field deficit. Five patients had more complex deficits. The visual field presentation procedure may help to reveal different types of reading disorders in patients with epilepsy and to dissociate orienting and selecting deficits.

[Le port du masque affecte l'identification des expressions faciales émotionnelles, surtout chez les personnes âgées]. / Wearing face masks makes identifying emotional facial expressions harder, especially for older adults.

Younger adults have difficulties identifying emotional facial expressions from faces covered by face masks. It is important to evaluate how face mask wearing might specifically impact older people, because they have lower emotion identification performance than younger adults, even without face masks. We compared performance of 62 young and 38 older adults in an online task of emotional facial expression identification using masked or unmasked pictures of faces with fear, happiness, anger, surprise, and neutral expression, from different viewpoints. Face masks affected performance in both age groups, but more so in older adults, specifically for negative emotions (anger, fear), in favour of the saliency hypothesis as an explanation for the positive advantage. Additionally, face masks more affected emotion recognition on profile than on three-quarter or full-face views. Our results encourage using clearer and full-face expressions when dealing with older people while wearing face masks.

Cognitive aspects of attention disorders in Alzheimer's disease.

Attention deficits are encountered at a very early stage in the development of Alzheimer's disease. While these deficits may be detected using classic clinical tests or even through simple observation, experimental tools enable a more precise evaluation of these deficits, typically by differentiating between conditions in which the quantity of attention needed varies, and by recording response times, which allows for a more precise and modulated measurement. The sensitivity of these tools can be further increased by analysing the intra-individual variability of performance in these experiments, which is particularly significant during the earliest stages of the disease. We present the cognitive aspects of these deficits by regrouping them according to the type of experiment used to highlight each deficit. We therefore distinguish spatial attention orientation deficits, executive control deficits, and sustained attention deficits. In each section, we present some of the more commonly used experiments (spatial cueing, spatial search, dual tasks, conflict tasks, vigilance tests), and draw parallels between these experiments and everyday life.

[Cognitive aspects of attention deficits in Alzheimer's disease]. / Aspects cognitifs des troubles de l'attention dans la maladie d'Alzheimer.

Attention deficits are encountered very early in the development of Alzheimer's disease. While these deficits may be detected using classic clinical tests or even from simple observation, experimental tools enable a more precise evaluation of these deficits, typically by subtracting between conditions which vary the quantity of necessary attention, and by recording response times which allow a more precise and modulated measurement. The sensitivity of these tools can be further increased by analyzing the intra-individual variability of performance in these experiments, this variability being particularly important during the earliest stages of the disease. We present the cognitive aspects of these deficits by regrouping them according to the type of experiment used to highlight each deficit. Thus, we distinguish deficits of spatial attention orientation, of executive control and of sustained attention. In each section we present several of the more often employed experiments (spatial cueing, spatial search, dual-tasks, conflict tasks, vigilance tests), and draw a parallel between these experiments and everyday life.

Problems inhibiting attentional capture by irrelevant stimuli in patients with frontotemporal dementia.

We studied the role of the frontal lobes in orienting spatial attention and inhibiting attentional capture by goal-irrelevant stimuli, using a spatial cueing method in patients with frontotemporal dementia (FTD). Two blocks of trials were presented, one with non-predictive cues and the other with counter-predictive cues. FTD patients showed a global orienting deficit, with a greater difference between invalid and valid trials than age-matched controls. However, they were able to use the (counter-) predictiveness of the cue to reduce the invalid/valid difference when targets occurred most often in the location opposite the cue. Thus, endogenous control of attention in our FTD patients was sufficient to reorient attention on the basis of the probability of events, but not to resist the capture of attention by goal-irrelevant stimuli. These results confirm the role of frontal lobes in the inhibition of attentional capture.

[Visual perceptual disorders in Alzheimer's disease]. / Les troubles de la perception visuelle dans la maladie d'Alzheimer.

Visual perception is humans' preferred way for taking information on the surrounding world. Visual perception is frequently impaired in patients with Alzheimer's disease, lessening patients' quality of life, and making evaluation of other cognitive deficits more complicated. Our review covers the recent literature describing visual perception deficits in patients suffering from Alzheimer's disease by classifying them according to their neuroanatomical correspondence: retina, visual pathway, subcortical structures, occipital visual cortex, occipito-temporal "what" and occipito-parietal "where" pathways. Overall, both low-level and high-level visual perception disorders seem quite common in Alzheimer's disease, including, on a low-level, loss of visual field, decreased acuity and contrast sensitivity, and impaired color vision, and on a high-level, impaired color vision, motion perception, visuospatial deficits, object agnosia, prosopagnosia and impaired recognition of facial emotional expressions. Professionals working with Alzheimer's disease should be aware of visuoperceptual deficits, which could impair the quality of life of the patients, and distort the results of neuropsychological tests using visual material. Moreover, some tests assessing visual perception could be of interest for early diagnosis of the disease.

Orienting of spatial attention in Huntington's Disease.

To explore the functioning of spatial attention in Huntington's Disease (HD), 14 HD patients and 14 age-matched controls performed a cued response time (RT) task with peripheral cues. In Experiment 1, cues were not informative about the future target location, thus eliciting a purely exogenous orienting of attention. At short stimulus-onset asynchrony (SOA), controls showed an initial facilitation for cued locations, later replaced by a cost (inhibition of return, IOR). Patients had a larger and more persistent validity effect, with delayed IOR, resulting from a larger cost for uncued targets. This suggests an impairment of attentional disengaging from cued locations. In Experiment 2, 80% of the cues were valid, thus inducing an initially exogenous, and later endogenous, attentional shift towards the cued box. The validity effect was larger in patients than in controls, again as a result of a disproportionate cost for uncued targets. In Experiment 3, 80% of the cues were invalid, thus inviting participants to endogenously re-orient attention towards the uncued box. Patients could take advantage of invalid cues to re-orient their attention towards the uncued targets but at a longer SOA than controls, thus suggesting that endogenous orienting is preserved in HD, but slowed down by the disengage deficit. The disengage deficit correlated with several radiological and biological markers of HD, thus suggesting a causal relationship between HD and attentional impairments. Cued RT tasks are promising tools for the clinical monitoring of HD and of its potential treatments.

A case of spatial neglect dysgraphia in Wilson's Disease.

We report here on a single neuropsychological case study of a young girl, KH, who presented with Wilson's Disease (WD) associated with a peripheral spatial neglect dysgraphia without major problems in the standard clinical tests of spatial neglect. Few studies have demonstrated a visuospatial deficit in WD and to date there has been no report of neglect syndrome arising from WD. However, recent studies have demonstrated that neglect is frequently associated with brain damage including the primary site of WD, the basal ganglia. KHs writing abilities were evaluated just after her admission to the rehabilitation department and 6 months later. The baseline evaluation demonstrated that KH had neglect dysgraphia with verbal stimuli (e.g., words or sentences) although her deficit was less evident in drawing multiple geometric shapes. Six months after the initial evaluation, KH showed evidence of neglect dysgraphia only when writing was associated with a secondary memory task. KHs writing performance is discussed with reference to previous cases of spatial neglect dysgraphia and in the context of spatial neglect. We suggest that the asymmetry between verbal writing and nonverbal drawing disturbances was caused by different attentional loads.

Examination of the split fovea theory in a case of pure left hemialexia.

To address the extent to which the visual foveal representation is split, we examine the case of a patient, M.B., suffering from a left mesial occipital lesion and presenting a pure left hemialexia and a right hemianopia with a spared area of the macula. Reading performance on tachistoscopically presented four-letter words and pseudowords in the spared area of the right visual field was significantly better than reading performance in the intact left visual field. Reading performance in the spared area of the right visual field was also significantly better than reading performance of stimuli centred on the fovea. Moreover, a length effect was found only in the left half of pseudowords centred on the fovea, but not in the right half (up to five letters). These differences in reading efficiency between the left and right halves of the foveal region militates in favour of the split fovea theory and cannot be explained by the bilateral projection theory.

Impaired orienting of attention in left unilateral neglect: a componential analysis.

Twenty-six patients suffering from damage to the right side of the brain, 19 of whom exhibited signs of left neglect, as well as 32 matched controls, ran 3 spatial cuing tasks. Patients were also tested with 2 cancellation tests, a line-bisection test, the copy of a complex drawing, and a visual extinction procedure. Results first showed correlations between extinction and cancellation tests performance on one hand, and between line bisection and copy on the other hand. Second, results demonstrated that an engagement deficit toward contralesional targets appeared to be the most striking feature of neglect, and the engagement score was correlated with the cancellation score and extinction. Most patients with neglect also presented a deficit in disengagement, a deficit of inhibition of return, and probably a deficit of alertness. Deficits in engagement and in disengagement, as well as poor scores in cancellation tests, seemed to be related with posterior cortical and subcortical lesions. Most important, even if an endogenous deficit (frequently related with a thalamic lesion) could aggravate the neglect behavior, neglect syndrome was mainly explained by a deficit of exogenous attention.

Attentional Processing of Letter Strings by Children.

Reading a letter string requires attentional orienting toward the beginning of the string (left-dominant orientation), followed by orienting along the string. These attentional-orienting processes differ according to the lexicality of the letter string: Sequential processes apply when reading nonwords or pseudowords, while words can be processed more globally. The aim of this study was to evaluate the development of these attentional processes involved in reading. We conducted two experiments in 6- (first grade), 7- (second grade), and 9-year-old (fourth grade) children, using a procedure that required the detection of a letter (Experiment 1) or a nonletter (Experiment 2) target in a string of five characters. The target character could occur in the second (left) or fourth (right) position in the string. Results showed an advantage for left nonletter targets as early as age 6 and of left letter targets as early as age 7. In 6-year-olds, only good readers detected a left letter target faster than a right letter target; others detected a right letter target faster. Thus, dominant orienting toward the beginning of the letter string is not fully developed in children before the second year of reading. A possibility is that beginning readers have difficulties inhibiting an attention-orienting bias toward the right visual field in linguistic tasks. The results also showed that the lexicality effect on these attentional processes develops gradually until the fourth year of reading. We believe that the procedure used in this study will be very valuable for evaluating attentional difficulties during reading acquisition.

Deficit of preparatory attention in children with frontal lobe epilepsy.

We compared the performance of a sustained attention task by children with epilepsy in either the frontal or temporal lobe. In a new simple task that specifically measures preparatory attention, developed recently by LaBerge, Auclair, and Siéroff [LaBerge, D., Auclair, L., & Siéroff, E. (2000). Preparatory attention: Experiment and theory. Consciousness and Cognition, 9, 396-434], patients responded to a target presented in the centre of the display and ignored a distracter presented at locations to the right or the left side of the target. The distracter was presented prior to the onset of the target and the relative frequency of the distracter to target was varied within a block of trials (from 0% to 67%). Children with frontal lobe epilepsy showed a higher mean slope of response time to the target as a function of distracter probability compared to children with temporal lobe epilepsy or compared to the response time slope of control subjects. The response time slope of children with temporal lobe epilepsy did not differ from that of control subjects. These results indicate that the presence of frontal lobe epilepsy selectively affects the capacity of these patients to resist the interference a distracter.

Neglected attention in apparent spatial compression.

Halligan and Marshall [Cortex 27 (1991) 623] devised a new test to evaluate the hypothesis that in visual neglect, left space is systematically compressed rightwards. In the critical condition of the original study, rows of horizontally arranged numbers with a target arrow pointing to one of them from the opposite margin of the display were presented. When asked to verbally identify the number indicated by the arrow, a right brain-damaged patient with left neglect and hemianopia often indicated a number to the right of the target. The more the target was located on the left, the greater the response shift rightward, as if rightward compression were linearly proportional to the co-ordinates of Euclidian space. However, a possible alternative account could be that the patient's attention was attracted by the numbers located to the right of the target digit, thus biasing her responses toward numbers on the right. To explore this hypothesis, we asked normal participants and patients with right hemisphere lesions, with and without neglect or hemianopia, to mark on the margin of a sheet the approximate location indicated by an arrow situated on the opposite margin. In three different conditions, the arrow indicated either one of several numbers or lines in a row, or a blank location on the sheet margin. Only patients with left neglect, and especially those with associated hemianopia, deviated rightward, and then crucially only on those conditions where visible targets were present, consistent with the attentional bias account.

[Attention and aging]. / Attention et vieillissement.

Due to progress in the cognitive theories in the last twenty years, the description of attentional deficits associated with normal or pathological aging has substantially improved. In this article, attentional deficits are presented according to Posner theory, which describes three sub-systems in a global network of attention: vigilance, selective attention, command. This theory not only characterizes the functions of these subsystems, but gives precise indications about their anatomical and neurochemical substrates. Several clinical tests can be described for each of these different subsystems. The main attentional deficits are presented in the second part of this paper: if some decline of the attentional command occurs in normal aging, a real deficit in this subsystem is found in most degenerative processes (frontotemporal dementia, Alzheimer and Parkinson diseases). Alzheimer disease is also frequently associated with a deficit of selective spatial attention, early in the evolution of the disease.

[Planning and activities of daily living in Alzheimer's disease and frontotemporal dementia]. / Planification et activités de la vie quotidienne dans la maladie d'Alzheimer et les dégénérescences frontotemporales.

OBJECTIVE: To study the relationship between the disturbances in activities of daily living and the scores on tests assessing planning activities in frontotemporal dementia (FTD) and Alzheimer's disease (AD). METHODS: Eleven patients with FTD were compared to 11 patients with AD and 29 healthy controls. Cognitive status, evaluated by the Dementia Rating Scale (DRS) and the Mini Mental State Examination (MMSE) was identical in the two groups of patients. Activities of daily living were assessed by three questionnaires completed by the main caregiver: (1) the Cognitive Difficulties Scale (CDS); (2) the NADL, a composite scale including the Physical self-maintenance scale (ADL) the Instrumental activities of daily living (IADL) the social activities scale, (SADL); (3) the Dysexecutive Questionnaire (DEX) from the Behavioural Assessment of the Dysexecutive Syndrome. Planning abilities were assessed by the tower of London and three tests from the BADS: the key search, the zoo map and the six elements. RESULTS: No quantitative differences were found between FTD and AD patients in daily living activities disturbances or scores on planning tests. Both were closely related to the global cognitive performance assessed by the DRS or the MMSE but no clear relationship was found between them. The scores on the tower of London were not correlated to those on the tests from the BADS. CONCLUSION: Neither assessment of activities of daily living or scores on the planning tests could differentiate FTD from AD. Planning appears as a multidimensional construct poorly assessed by the usual assessment tools.

Development of endogenous orienting of attention in school-age children.

Orienting of attention was investigated in 6-, 8-, and 10-year-olds and in young adults, in a spatial cueing experiment comparing nonpredictive, predictive, and counterpredictive cues (in different blocks). A larger positive orienting effect (advantage of valid over invalid cues) in the predictive than in the nonpredictive condition occurred in all groups, showing efficient endogenous orienting of attention. However, this effect was larger in 6-year-olds, as if the ability to distribute attention between the different locations (and not only to orient to the most probable location) developed between 6 and 8 years. Moreover, only 10-year-olds and adults showed a significant negative orienting effect (advantage of invalid cues) in the counterpredictive condition, indicating inhibition of attentional capture by goal-irrelevant stimuli. Therefore, our results indicate a large change in the modulation of endogenous orienting between 6 and 10 years.

Timing constraints of temporal view association in face recognition.

This study tests the hypothesis that the recognition of a face is facilitated when the face has previously been presented in a rapid rather than a slow view sequence. We used a sequential comparison task, in which a first face, rotating back and forth around a left or a right three-quarter view, was followed, after a 1-s delay, by a static view of a second face, with the same or a different viewpoint. We compared rapid (180 ms per view) and slow (720 ms per view) sequences to evaluate the timing constraints of temporal view association, and video and view sequences to evaluate the importance of motion smoothness. Response times were faster for rapid view sequences, showing the importance of perceiving the views in a short temporal window. When the views of a face are perceived in a rapid sequence, attention may be distributed over the entire sequence, leading to a unified representation associating the views. This unified representation facilitates the recognition of the face. Moreover, response times were faster for view sequences than for video sequences, showing no advantage of motion smoothness.