Differential vulnerability of global motion, global form, and biological motion processing in full-term and preterm children

Young children born very prematurely show elevated thresholds for global motion and global form [Atkinson, J. & Braddick, O. (2007). Visual and visuocognitive development in children born very prematurely. Progress in Brain Research, 164, 123–149; MacKay, T. L., Jakobson, L. S., Ellemberg, D., Lewis, T. L., Maurer, D., & Casiro, O. (2005). Deficits in the processing of local and global motion in very low birthweight children. Neuropsychologia, 43, 1738–1748]. In adolescence, those with white matter pathology show reduced sensitivity to biological motion [Pavlova, M., Sokolov, A., Staudt, M., Marconato, F., Birbaumer, N., & Krageloh-Mann, I. (2005). Recruitment of periventricular parietal regions in processing cluttered point-light biological motion. Cerebral Cortex, 15, 594–601; Pavlova, M., Staudt, M., Sokolov, A., Birbaumer, N., & Krageloh-Mann, I. (2003). Perception and production of biological movement in patients with early periventricular brain lesions. Brain, 126, 692–701]. Here, we measured sensitivity to global form, global motion, and biological motion in a sample of 23, five- to nine-year-old children born at <32 weeks gestation, and in 20 full-term controls matched to the clinical sample in age, socioeconomic status, and estimated Verbal IQ. As a group, premature children showed reduced sensitivity, relative to controls, on all three tasks (F > 4.1, p < 0.05). By computing a deficit score for each task (the ratio between a premature child's threshold and the mean threshold for three age-matched controls) we were able to compare performance across tasks directly. Mean deficit scores were significantly greater than 1 (indicating some level of impairment) for biological motion and global motion (ps < 0.03). In contrast, the mean deficit score for global form was not significantly different from 1 (indicating no impairment, relative to age-matched control children). Rates of impairment (deficit score ≥ 2) were four times higher for global motion than for global form (p < 0.04); rates of impairment on the biological motion task fell at an intermediate level. In agreement with previous studies, we find impairments in the processing of global motion (Atkinson & Braddick; MacKay et al.) and of biological motion (Pavlova et al.), which are larger than the impairments in the processing of global form (Atkinson & Braddick). In addition, we show that the impairments are not correlated with each other. The differential vulnerability that we observed across tasks could not be accounted for by stereoacuity deficits, amblyopia, or attentional problems. We suspect, instead, that it reflects the fact that these forms of visual processing develop at different rates, and may be differentially vulnerable to early brain injury or atypical neurodevelopment [c.f., Atkinson, J. & Braddick, O. (2007). Visual and visuocognitive development in children born very prematurely. Progress in Brain Research, 164, 123–149; Braddick, O., Atkinson, J., & Wattam-Bell, J. (2003). Normal and anomalous development of visual motion processing: Motion coherence and ‘dorsal-stream vulnerability’. Neuropsychologia, 41, 1769–1784].     

Dissociation between exact and approximate addition in developmental dyslexia

Previous research has suggested that number sense and language are involved in number representation and calculation, in which number sense supports approximate arithmetic, and language permits exact enumeration and calculation. Meanwhile, individuals with dyslexia have a core deficit in phonological processing. Based on these findings, we thus hypothesized that children with dyslexia may exhibit exact calculation impairment while doing mental arithmetic. The reaction time and accuracy while doing exact and approximate addition with symbolic Arabic digits and non-symbolic visual arrays of dots were compared between typically developing children and children with dyslexia. Reaction time analyses did not reveal any differences across two groups of children, the accuracies, interestingly, revealed a distinction of approximation and exact addition across two groups of children. Specifically, two groups of children had no differences in approximation. Children with dyslexia, however, had significantly lower accuracy in exact addition in both symbolic and non-symbolic tasks than that of typically developing children. Moreover, linguistic performances were selectively associated with exact calculation across individuals. These results suggested that children with dyslexia have a mental arithmetic deficit specifically in the realm of exact calculation, while their approximation ability is relatively intact.     

Clinical neurophysiology of visual and auditory processing in dyslexia: A review

Neurophysiological studies on children and adults with dyslexia provide a deeper understanding of how visual and auditory processing in dyslexia might relate to reading deficits. The goal of this review is to provide an overview of research findings in the last two decades on motion related and contrast sensitivity visual evoked potentials and on auditory event related potentials to basic tone and speech sound processing in dyslexia. These results are particularly relevant for three important theories about causality in dyslexia: the magnocellular deficit hypothesis, the temporal processing deficit hypothesis and the phonological deficit hypothesis. Support for magnocellular deficits in dyslexia are primarily provided from evidence for altered visual evoked potentials to rapidly moving stimuli presented at low contrasts. Consistently ERP findings revealed altered neurophysiological processes in individuals with dyslexia to speech stimuli, but evidence for deficits processing certain general acoustic information relevant for speech perception, such as frequency changes and temporal patterns, are also apparent.     

Holistic versus detailed visual processing in body dysmorphic disorder: Testing the inversion,composite and global precedence effects

Individuals with Body Dysmorphic Disorder (BDD) are preoccupied with perceived defects in their appearance that are not visible to others. An excessive focus and processing of details has been proposed as a possible mechanism underlying this distorted self-image in BDD. The nature and extent of visuoperceptual abnormalities in BDD however require further investigation; specifically, it remains unclear whether feature-based processing in BDD is a result of a failure of holistic perceptual processes. The present study evaluated whether BDD is associated with an impairment in global processing. Twenty-five individuals with a primary diagnosis of BDD (15 unmedicated, 10 medicated) and 25 matched healthy controls were administered three robust behavioural tasks that test holistic encoding, namely the face inversion, the composite and the navon tasks. Overall, individuals in the BDD and control groups performed similarly in all aspects of holistic processing tested. Our findings suggest that the excessive focus on specific aspects of appearance in BDD may not be explained by impairments in the global encoding of visual information. Implications of these results and suggestions for future research on visual processing in BDD are discussed.     

Lack of visual evoked potentials amplitude decrement during prolonged reversal and motion stimulation in migraineurs

ObjectiveWe evaluated response decrement during a short time repetitive low and high contrast reversal and low contrast motion stimulation in controls and migraineurs.MethodsA total of 39 migraine patients (out of which 19 were in the interictal period and without prophylactic treatment) and 36 healthy volunteers were examined using pattern-reversal (PR-VEP) and motion-onset (M-VEP) visual evoked potentials. Binocular stimulation lasted 2.5 min and the decrement assessment was blinded.ResultsEvidence of significant decrement was observed in healthy volunteers for high contrast PR-VEP amplitude of P100-N75 ratios between the fifth and first blocks (0.9; p = 0.001) with a linear decline (−0.7 μV/min, p = 0.001) and in the P100-N145 amplitude with linear decline (−0.5 μV/min, p = 0.004). Significant decrement was also observed for the ratio between the fifth and first block P1-N2 amplitudes in M-VEP (0.9, p = 0.006). No significant decrement was noted in the low contrast PR-VEP or among migraineurs.ConclusionsWe confirm differences in decrease of VEPs amplitude during short term examination between controls and migraineurs. We showed the decrement deficit also in the extrastriatal regions of the migraineurs’ visual cortex.SignificanceLow contrast and motion-onset stimuli in short time decrement assessment did not increase the test sensitivity.     

Phonological,temporal and spectral processing in vowel length discrimination is impaired in German primary school children with developmental dyslexia

It is still unclear whether phonological processing deficits are the underlying cause of developmental dyslexia, or rather a consequence of basic auditory processing impairments. To avoid methodological confounds, in the current study the same task and stimuli of comparable complexity were used to investigate both phonological and basic auditory (temporal and spectral) processing in dyslexia. German dyslexic children (Grades 3 and 4) were compared to age- and grade-matched controls in a vowel length discrimination task with three experimental conditions: In a phonological condition, natural vowels were used, differing both with respect to temporal and spectral information (in German, vowel length is phonemic, and vowel length differences are characterized by both temporal and spectral information). In a temporal condition, spectral information differentiating between the two vowels of a pair was eliminated, whereas in a spectral condition, temporal differences were removed. As performance measure, the sensitivity index d′ was computed. At the group level, dyslexic children's performance was inferior to that of controls for phonological as well as temporal and spectral vowel length discrimination. At an individual level, nearly half of the dyslexic sample was characterized by deficits in all three conditions, but there were also some children showing no deficits at all. These results reveal on the one hand that phonological processing deficits in dyslexia may stem from impairments in processing temporal and spectral information in the speech signal. On the other hand they indicate, however, that not all dyslexic children might be characterized by phonological or auditory processing deficits.     

Abnormal timing of visual feedback processing in young adults with schizophrenia

Background

Recent studies have shown that schizophrenia is characterized by visual perceptual deficits, especially in the ability to integrate stimulus details into a global percept. Also, several studies have found amplitude attenuation of the visual P1 component of the event-related brain potential (ERP), probably indicating impaired visual feedforward processing in schizophrenia. However, there is little knowledge on the role of feedbackward processing in this group. This question is of importance, as recent studies indicate that feedback processing is critical in stimulus integration.

Methods

In the present study we tested whether there is evidence for atypical recurrent processing in a group of 14 young adults with recent-onset schizophrenia (mean age 21.7 years, mean TIQ 92.7) and 17 age and IQ matched control subjects, all males. To achieve this aim, we used a texture segregation task and measured ERP activity concurrently.

Results

We found normal amplitudes, but longer latencies of activity related to feedbackward processing in the schizophrenia group. In addition, we found enhanced occipito-temporal activity around 160 ms that is probably the reflection of increased detail processing.

Discussion

We show for the first time evidence for abnormal timing in feedback activity related to visual perception in subjects with schizophrenia. It is hypothesized that this latency effect is the functional reflection of abnormal structural connectivity in this group, and might result in increased processing of stimulus detail.     

Impairments in speech and nonspeech sound categorization in children with dyslexia are driven by temporal processing difficulties

Auditory processing problems in persons with dyslexia are still subject to debate, and one central issue concerns the specific nature of the deficit. In particular, it is questioned whether the deficit is specific to speech and/or specific to temporal processing. To resolve this issue, a categorical perception identification task was administered in thirteen 11-year old dyslexic readers and 25 matched normal readers using 4 sound continua: (1) a speech contrast exploiting temporal cues (/bA/-/dA/), (2) a speech contrast defined by nontemporal spectral cues (/u/-/y/), (3) a nonspeech temporal contrast (spectrally rotated/bA/-/da/), and (4) a nonspeech nontemporal contrast (spectrally rotated/u/-/y/). Results indicate that children with dyslexia are less consistent in classifying speech and nonspeech sounds on the basis of rapidly changing (i.e., temporal) information whereas they are unimpaired in steady-state speech and nonspeech sounds. The deficit is thus restricted to categorizing sounds on the basis of temporal cues and is independent of the speech status of the stimuli. The finding of a temporal-specific but not speech-specific deficit in children with dyslexia is in line with findings obtained in adults using the same paradigm (Vandermosten et al., 2010, Proceedings of the National Academy of Sciences of the United States of America, 107: 10389-10394). Comparison of the child and adult data indicates that the consistency of categorization considerably improves between late childhood and adulthood, particularly for the continua with temporal cues. Dyslexic and normal readers show a similar developmental progress with the dyslexic readers lagging behind both in late childhood and in adulthood.     

Convergent and divergent effects of neck proprioceptive and visual motion stimulation on visual space processing in neglect

Visual motion stimulation as well as neck muscle vibration are known to effectively modulate the subjective body orientation in spatial neglect. However, so far only motion stimulation has been demonstrated to substantially influence size and space distortion in neglect patients. The present study aimed to compare the two stimulation methods with respect to their potentially differential impact on subjective body orientation and on space and size distortion, in five neglect patients showing perceptual distortions. We found comparable beneficial effects during left motion stimulation and left neck vibration for the subjective straight ahead. Additionally, left motion stimulation significantly ameliorated the leftward overextension in size matching, line bisection and distance estimation in all five patients. In contrast, during neck vibration only two patients showed an improvement for line bisection and size estimation and none did so for distance estimation. Since these two patients differed from the others as they had either no visual field defects or a major visual field sparing, we suggest--based on recent anatomical and neuropsychological findings--that neck vibration only tends to improve pure neglect-related visuo-perceptual distortions whereas motion stimulation can additionally improve perceptual distortions in neglect associated with hemianopia.     

Neural correlates of visual motion processing without awareness in patients with striate cortex and pulvinar lesions

Patients with striate cortex lesions experience visual perception loss in the contralateral visual field. In few patients, however, stimuli within the blind field can lead to unconscious (blindsight) or even conscious perception when the stimuli are moving (Riddoch syndrome). Using functional magnetic resonance imaging (fMRI), we investigated the neural responses elicited by motion stimulation in the sighted and blind visual fields of eight patients with lesions of the striate cortex. Importantly, repeated testing ensured that none of the patients exhibited blindsight or a Riddoch syndrome. Three patients had additional lesions in the ipsilesional pulvinar. For blind visual field stimulation, great care was given that the moving stimulus was precisely presented within the borders of the scotoma. In six of eight patients, the stimulation within the scotoma elicited hemodynamic activity in area human middle temporal (hMT) while no activity was observed within the ipsilateral lesioned area of the striate cortex. One of the two patients in whom no ipsilesional activity was observed had an extensive lesion including massive subcortical damage. The other patient had an additional focal lesion within the lateral inferior pulvinar. Fiber‐tracking based on anatomical and functional markers (hMT and Pulvinar) on individual diffusion tensor imaging (DTI) data from each patient revealed the structural integrity of subcortical pathways in all but the patient with the extensive subcortical lesion. These results provide clear evidence for the robustness of direct subcortical pathways from the pulvinar to area hMT in patients with striate cortex lesions and demonstrate that ipsilesional activity in area hMT is completely independent of conscious perception. Hum Brain Mapp 36:1585–1594, 2015. © 2014 Wiley Periodicals, Inc.     

Newborn brain event-related potentials revealing atypical processing of sound frequency and the subsequent association with later literacy skills in children with familial dyslexia

The role played by an auditory-processing deficit in dyslexia has been debated for several decades. In a longitudinal study using brain event-related potentials (ERPs) we investigated 1) whether dyslexic children with familial risk background would show atypical pitch processing from birth and 2) how these newborn ERPs later relate to these same children’s pre-reading cognitive skills and literacy outcomes. Auditory ERPs were measured at birth for tones varying in pitch and presented in an oddball paradigm (1100 Hz, 12%, and 1000 Hz, 88%). The brain responses of the typically reading control group children (TRC group, N = 25) showed clear differentiation between the frequencies, while those of the group of reading disability with familial risk (RDFR, 8 children) and the group of typical readers with familial risk (TRFR, 14 children) did not differentiate between the tones. The ERPs of the latter two groups differed from those of the TRC group. However, the two risk groups also showed a differential hemispheric ERP pattern. Furthermore, newborn ERPs reflecting passive change detection were associated with phonological skills and letter knowledge prior to school age and with phoneme duration perception, reading speed (RS) and spelling accuracy in the 2nd grade of school. The early obligatory response was associated with more general pre-school language skills, as well as with RS and reading accuracy (RA). Results suggest that a proportion of dyslexic readers with familial risk background are affected by atypical auditory processing. This is already present at birth and also relates to pre-reading phonological processing and speech perception. These early differences in auditory processing could later affect phonological representations and reading development. However, atypical auditory processing is unlikely to suffice as a sole explanation for dyslexia but rather as one risk factor, dependent on the genetic profile of the child.     

The effect of spatio-temporal distance between visual stimuli on information processing in children with Specific Language Impairment

The purpose of this study is to evaluate whether children with Specific Language Impairment (SLI) have a deficit in processing a sequence of two visual stimuli (S1 and S2) presented at different inter-stimulus intervals and in different spatial locations. In particular, the core of this study is to investigate whether S1 identification is disrupted due to a retroactive interference of S2.To this aim, two experiments were planned in which children with SLI and children with typical development (TD), matched by age and non-verbal IQ, were compared (Experiment 1: SLI n = 19; TD n = 19; Experiment 2: SLI n = 16; TD n = 16).Results show group differences in the ability to identify a single stimulus surrounded by flankers (Baseline level). Moreover, children with SLI show a stronger negative interference of S2, both for temporal and spatial modulation.These results are discussed in the light of an attentional processing limitation in children with SLI.     

Delays in the reading and spelling of children with cerebral palsy: Associations with phonological and visual processes

BackgroundThis investigation addresses the question of whether there exists a significant discrepancy in the cognitive abilities of children with cerebral palsy (CP) who, despite the presence of age appropriate communication and language, have reading and spelling delays.AimsWe wanted to discover whether there was a relationship between the phonological and visual perceptual abilities of children with CP and their progress in reading and spelling.Methods and proceduresFifteen children with CP (aged between 6:9 years and 11:6 years) were assessed on reading and spelling; communication and language; non-verbal reasoning; phonological processing; and visual perception.Outcomes and resultsTen of the children had very weak reading and spelling skills. Five children had (mostly) age appropriate scores of reading and spelling. No differences were found between these two groups in non-verbal reasoning or communication and language. However, phonological abilities, visual sequential memory and perception of visuospatial relationships were found to be related to reading and spelling.Conclusions and implicationsThe findings suggest that children with CP are at risk for reading and spelling delays when they have poor phonological processing, visual sequential memory and perception of visuospatial relationships. The implications of the findings for classroom practice are discussed.     

Correlations of sensory processing and visual organization ability with participation in school-aged children with Down syndrome

Previous work has highlighted delays and differences in cognitive, language, and sensorimotor functions in children diagnosed with Down syndrome (DS). However, sensory processing and visual organization abilities have not been well-examined in DS to date. This study aimed to investigate the developmental profile of sensory processing and visual organization abilities, body functions classified by the World Health Organization's ICF model, and their impacts on participation in DS to guide research and evidence-based practices. Two hundred and six children (101 boys, 105 girls) with DS (age range = 6 years 1 month to 12 years 10 months; mean age = 8 years 1 month) were assessed on measures of sensory processing (Sensory Profile), visual organization ability (Hooper Visual Organization Test), and activity participation (Vineland Adaptive Behavior Scale, School Function Assessment). Our findings characterized the developmental continuum of body functions (sensory processing and visual organization) of children with DS, and revealed their correlations with activity participation. Interventions focused on improving body functions is needed while stressing the acquisition of functional skills that increase participation in age-appropriate activities.     

Effects of pattern redundancy and hierarchical grouping on global-local visual processing in monkeys (Cebus apella) and humans (Homo sapiens)

Using a Matching-To-Sample (MTS) procedure we assessed the effects of stimulus redundancy, defined on the basis of the information-theory approach to shape goodness proposed by Garner (1974) [20], and grouping on the processing of hierarchical visual patterns in capuchin monkeys and humans. In a first experiment, the MTS performance of both capuchin monkeys and humans benefitted from stimulus redundancy. Moreover, a local advantage in capuchins was observed with visual patterns that required grouping at both global and local level. In a second experiment we eliminated the requirement to group at the local level. This was done to determine if the effects of redundancy would have been evident in condition more similar to those used in previous studies of global-local processing in a comparative context. The benefits of stimulus redundancy emerged again in both species but were confined to local processing in monkeys and to global processing in humans. A local advantage was observed in both species. In a third experiment, the reduction of the size of the stimuli and the increase of the quantity of the local elements produced a shift to global dominance in humans but the local dominance in monkeys was preserved. The implications of these results are discussed in relation to other similarities and differences in higher visual functions in humans and monkeys.     

The influence of steroid sex hormones on the cognitive and emotional processing of visual stimuli in humans

Steroid sex hormones are responsible for some of the differences between men and women. In this article, I review evidence that steroid sex hormones impact on visual processing. Given prominent sex-differences, I focus on three topics for sex hormone effects for which there is most research available: 1. Preference and mate choice, 2. Emotion and recognition, and 3. Cerebral/perceptual asymmetries and visual–spatial abilities. For each topic, researchers have examined sex hormones and visual processing using various methods. I review indirect evidence addressing variation according to: menstrual cycle phase, pregnancy, puberty, and menopause. I further address studies of variation in testosterone and a measure of prenatal testosterone, 2D:4D, on visual processing. The most conclusive evidence, however, comes from experiments. Studies in which hormones are administrated are discussed. Overall, many studies demonstrate that sex steroids are associated with visual processing. However, findings are sometimes inconsistent, differences in methodology make strong comparisons between studies difficult, and we generally know more about activational than organizational effects.     

Reduced attentional capacity, but normal processing speed and shifting of attention in developmental dyslexia: Evidence from a serial task

We report the performance of a group of adult dyslexics and matched controls in an array-matching task where two strings of either consonants or symbols are presented side by side and have to be judged to be the same or different. The arrays may differ either in the order or identity of two adjacent characters. This task does not require naming – which has been argued to be the cause of dyslexics’ difficulty in processing visual arrays – but, instead, has a strong serial component as demonstrated by the fact that, in both groups, Reaction times (RTs) increase monotonically with position of a mismatch. The dyslexics are clearly impaired in all conditions and performance in the identity conditions predicts performance across orthographic tasks even after age, performance IQ and phonology are partialled out. Moreover, the shapes of serial position curves are revealing of the underlying impairment. In the dyslexics, RTs increase with position at the same rate as in the controls (lines are parallel) ruling out reduced processing speed or difficulties in shifting attention. Instead, error rates show a catastrophic increase for positions which are either searched later or more subject to interference. These results are consistent with a reduction in the attentional capacity needed in a serial task to bind together identity and positional information. This capacity is best seen as a reduction in the number of spotlights into which attention can be split to process information at different locations rather than as a more generic reduction of resources which would also affect processing the details of single objects.     

Relationships between time estimation,memory, attention,and processing speed in patients with severe traumatic brain injury

The present experiment was aimed at investigating the effects of memory and attention deficits and of information processing slowing on time estimation in patients with severe traumatic brain injury (TBI). Patients with TBI and normal control subjects reproduced and produced durations (5, 14, 38s) in both a control counting condition and in a concurrent reading condition. They also performed finger-tapping tasks at a free rate and at a 1s rate. Both groups were assessed on processing speed using a reaction-time task, and on memory and attention using a battery of neuropsychological tests. The results showed that time estimation was not less accurate in patients with TBI than in control subjects on the reproduction task or on the production task performed either in the control counting condition or in the concurrent reading condition. Conversely, duration judgments were more variable in patients with TBI than in control subjects on both tasks in both conditions. The results also showed that TBI patients exhibited slower reaction-times, and poorer working and episodic memory scores than control subjects. Most importantly, the variability index in the duration reproduction task was related to both working memory scores and processing speed measures, whereas the variability index in the duration production task was only related with the processing speed measures. The temporal performance pattern in TBI patients does not appear to reflect specific deficits in timing, but rather overall problems in attention, working memory, and processing speed mechanisms.