Journal of autism and developmental disorders, 2002
Based on clinical observations of abnormal gaze behavior of autistic children, it has been sugges... more Based on clinical observations of abnormal gaze behavior of autistic children, it has been suggested that autistic children have a problem in processing social information. Several studies on eye movements have indeed found indications that children with autism show particularly abnormal gaze behavior in relation to social stimuli. However, the methodology used in such investigations did not allow for precise gaze analysis. In the present study, the looking behavior of autistic children toward cartoon-like scenes that included a human figure was measured quantitatively using an infrared eye-tracking device. Fixation behavior of autistic children was similar to that of their age- and IQ-matched normal peers. These results do not support the notion that autistic children have a specific problem in processing socially loaded visual stimuli. Also, there is no indication for an abnormality in gaze behavior in relation to neutral objects. It is suggested that the often-reported abnormal u...
The Journal of neuroscience : the official journal of the Society for Neuroscience, Jan 23, 2014
The way we perceive the present visual environment is influenced by past visual experiences. Here... more The way we perceive the present visual environment is influenced by past visual experiences. Here we investigated the neural basis of such experience dependency. We repeatedly presented human observers with an ambiguous visual stimulus (structure-from-motion) that can give rise to two distinct perceptual interpretations. Past visual experience is known to influence the perception of such stimuli. We recorded fast dynamics of neural activity shortly after stimulus onset using event-related electroencephalography. The number of previous occurrences of a certain percept modulated early posterior brain activity starting as early as 50 ms after stimulus onset. This modulation developed across hundreds of percept repetitions, reflecting several minutes of accumulating perceptual experience. Importantly, there was no such modulation when the mere number of previous stimulus presentations was considered regardless of how they were perceived. This indicates that the effect depended on previo...
Multiple complex developmental disorder (MCDD) is a well-defined and validated behavioural subtyp... more Multiple complex developmental disorder (MCDD) is a well-defined and validated behavioural subtype of pervasive developmental disorder-not otherwise specified (PDD-NOS) and is thought to be associated with a higher risk of developing a schizophrenic spectrum disorder. The question was addressed whether patients with MCDD show the same psychophysiological abnormalities as seen in patients with schizophrenia. Smooth pursuit eye movement (pursuit gain and saccadic parameters) was measured in children with either MCDD (n=18) or autism (n=18), and in age- and IQ-matched controls (n=36), as well as in a group of adult patients with schizophrenia (n=14) and a group of adult controls (n=17). We found the expected effect of lower velocity gain and increased number of saccades in schizophrenic patients. Children with MCDD also showed a lower velocity gain compared to controls children. In contrast, velocity gain was similar in autistic subjects and controls. No differences for velocity gain were found in a direct comparison between MCDD and autism. Saccadic parameters were not significantly different from controls in either MCDD or autistic subjects. Children with MCDD, like schizophrenic adults, show a reduced velocity gain, which could indicate that schizophrenia spectrum disorders and MCDD share (at least to some degree) a common neurobiological background.
The authors assessed visual information processing in high-functioning individuals with pervasive... more The authors assessed visual information processing in high-functioning individuals with pervasive developmental disorders (PDD) and their parents. The authors used tasks for contrast sensitivity, motion, and form perception to test visual processing occurring relatively early and late in the magnocellular-dorsal and parvocellular-ventral pathways. No deficits were found in contrast sensitivity for low or high spatial frequencies or for motion or form perception between individuals with PDD in comparison with a matched control group. Individuals with PDD performed equally with or better than controls on motion detection tasks. In addition, the authors did not find differences on any of the tasks between parents of the PDD group and matched control parents. These results indicate that high-functioning individuals with PDD and their parents are able to process visual stimuli that rely on early or late processing in the magnocellular-dorsal and parvocellular-ventral pathways as well as controls.
Abstract Although there is considerable evidence for the role of feedforward, horizontal, and rec... more Abstract Although there is considerable evidence for the role of feedforward, horizontal, and recurrent interactions in figure-ground segregation, little is known about how this process would be affected by a selective deficit in one of these interactions. We conjectured that an ...
The abnormal gaze behavior of autistic children toward human faces, as observed in daily-life sit... more The abnormal gaze behavior of autistic children toward human faces, as observed in daily-life situations, are investigated in two fixation time studies. It has been argued that faces are a special kind of stimuli for normal individuals and that this might not be the case for autistic children. A group of high-functioning autistic children (including a group of sub-threshold PDD-NOS children) was compared with a group of normal children, with respect to their fixation behavior for photographs of human faces. Using an infrared eye-tracking device, fixation times for the whole face and for the facial elements of faces were compared between the two groups. The first study dealt with faces having an emotional expression. The second study dealt with neutral faces presented either upright or upside-down. Results of the two studies showed that autistic children have the same fixation behavior as normal children for upright faces, with or without an emotional expression. Furthermore, results of the second study showed that normal children spent less time looking at upside-down faces, but that the fixation times of autistic children were not influenced by the orientation of the faces. These results plead against the notion that the abnormal gaze behavior in everyday life is due to the presence of facial stimuli per se. Furthermore, the absence of a face orientation effect in autistic children might be a reflection of a lack of holistic processing of human faces in autism.
Journal of Autism and Developmental Disorders, 2007
Research on visual perception in Autism Spectrum Disorder (ASD) tries to reveal the underlying me... more Research on visual perception in Autism Spectrum Disorder (ASD) tries to reveal the underlying mechanisms of aberrant local and global processing. Global motion perception is one way to study this aspect of ASD. We used plaid motion stimuli, which can be perceived as a coherently moving pattern, requiring feature integration, or as two transparent gratings sliding over each other. If global motion detection is impaired in ASD, this would lead to a decrease of the total time that a coherent pattern is perceived. However, in contrast to other studies in the literature, our results gave no evidence of impaired global motion perception in people with ASD. A reconciliation of the different outcomes is proposed based on spatial frequency processing in ASD.
PurposeThe effect of methylphenidate (MPH) on inhibitory control as assessed by the stop task in ... more PurposeThe effect of methylphenidate (MPH) on inhibitory control as assessed by the stop task in children with attention-deficit/hyperactivity disorder (ADHD) could be influenced by task difficulty and may be mediated by attention.Subjects and methodsFifteen children with ADHD performed the stop and the change task after placebo, 0.5 and 1.0 mg/kg MPH in a within-subject design.ResultsLinear-trend analysis showed a similar effect of MPH in both tasks and a stronger effect for inhibitory control than for attention. Furthermore, a correlation was found between blood serum metabolites of norepinephrine and dopamine for attentional measures and inhibitory control measures, respectively.Discussion and conclusionIn children with ADHD MPH could act primarily on inhibitory control, and is not influenced by task difficulty. Also, attention and inhibitory control could have differential pharmacological profiles.
Journal of autism and developmental disorders, 2002
Based on clinical observations of abnormal gaze behavior of autistic children, it has been sugges... more Based on clinical observations of abnormal gaze behavior of autistic children, it has been suggested that autistic children have a problem in processing social information. Several studies on eye movements have indeed found indications that children with autism show particularly abnormal gaze behavior in relation to social stimuli. However, the methodology used in such investigations did not allow for precise gaze analysis. In the present study, the looking behavior of autistic children toward cartoon-like scenes that included a human figure was measured quantitatively using an infrared eye-tracking device. Fixation behavior of autistic children was similar to that of their age- and IQ-matched normal peers. These results do not support the notion that autistic children have a specific problem in processing socially loaded visual stimuli. Also, there is no indication for an abnormality in gaze behavior in relation to neutral objects. It is suggested that the often-reported abnormal u...
The Journal of neuroscience : the official journal of the Society for Neuroscience, Jan 23, 2014
The way we perceive the present visual environment is influenced by past visual experiences. Here... more The way we perceive the present visual environment is influenced by past visual experiences. Here we investigated the neural basis of such experience dependency. We repeatedly presented human observers with an ambiguous visual stimulus (structure-from-motion) that can give rise to two distinct perceptual interpretations. Past visual experience is known to influence the perception of such stimuli. We recorded fast dynamics of neural activity shortly after stimulus onset using event-related electroencephalography. The number of previous occurrences of a certain percept modulated early posterior brain activity starting as early as 50 ms after stimulus onset. This modulation developed across hundreds of percept repetitions, reflecting several minutes of accumulating perceptual experience. Importantly, there was no such modulation when the mere number of previous stimulus presentations was considered regardless of how they were perceived. This indicates that the effect depended on previo...
Multiple complex developmental disorder (MCDD) is a well-defined and validated behavioural subtyp... more Multiple complex developmental disorder (MCDD) is a well-defined and validated behavioural subtype of pervasive developmental disorder-not otherwise specified (PDD-NOS) and is thought to be associated with a higher risk of developing a schizophrenic spectrum disorder. The question was addressed whether patients with MCDD show the same psychophysiological abnormalities as seen in patients with schizophrenia. Smooth pursuit eye movement (pursuit gain and saccadic parameters) was measured in children with either MCDD (n=18) or autism (n=18), and in age- and IQ-matched controls (n=36), as well as in a group of adult patients with schizophrenia (n=14) and a group of adult controls (n=17). We found the expected effect of lower velocity gain and increased number of saccades in schizophrenic patients. Children with MCDD also showed a lower velocity gain compared to controls children. In contrast, velocity gain was similar in autistic subjects and controls. No differences for velocity gain were found in a direct comparison between MCDD and autism. Saccadic parameters were not significantly different from controls in either MCDD or autistic subjects. Children with MCDD, like schizophrenic adults, show a reduced velocity gain, which could indicate that schizophrenia spectrum disorders and MCDD share (at least to some degree) a common neurobiological background.
The authors assessed visual information processing in high-functioning individuals with pervasive... more The authors assessed visual information processing in high-functioning individuals with pervasive developmental disorders (PDD) and their parents. The authors used tasks for contrast sensitivity, motion, and form perception to test visual processing occurring relatively early and late in the magnocellular-dorsal and parvocellular-ventral pathways. No deficits were found in contrast sensitivity for low or high spatial frequencies or for motion or form perception between individuals with PDD in comparison with a matched control group. Individuals with PDD performed equally with or better than controls on motion detection tasks. In addition, the authors did not find differences on any of the tasks between parents of the PDD group and matched control parents. These results indicate that high-functioning individuals with PDD and their parents are able to process visual stimuli that rely on early or late processing in the magnocellular-dorsal and parvocellular-ventral pathways as well as controls.
Abstract Although there is considerable evidence for the role of feedforward, horizontal, and rec... more Abstract Although there is considerable evidence for the role of feedforward, horizontal, and recurrent interactions in figure-ground segregation, little is known about how this process would be affected by a selective deficit in one of these interactions. We conjectured that an ...
The abnormal gaze behavior of autistic children toward human faces, as observed in daily-life sit... more The abnormal gaze behavior of autistic children toward human faces, as observed in daily-life situations, are investigated in two fixation time studies. It has been argued that faces are a special kind of stimuli for normal individuals and that this might not be the case for autistic children. A group of high-functioning autistic children (including a group of sub-threshold PDD-NOS children) was compared with a group of normal children, with respect to their fixation behavior for photographs of human faces. Using an infrared eye-tracking device, fixation times for the whole face and for the facial elements of faces were compared between the two groups. The first study dealt with faces having an emotional expression. The second study dealt with neutral faces presented either upright or upside-down. Results of the two studies showed that autistic children have the same fixation behavior as normal children for upright faces, with or without an emotional expression. Furthermore, results of the second study showed that normal children spent less time looking at upside-down faces, but that the fixation times of autistic children were not influenced by the orientation of the faces. These results plead against the notion that the abnormal gaze behavior in everyday life is due to the presence of facial stimuli per se. Furthermore, the absence of a face orientation effect in autistic children might be a reflection of a lack of holistic processing of human faces in autism.
Journal of Autism and Developmental Disorders, 2007
Research on visual perception in Autism Spectrum Disorder (ASD) tries to reveal the underlying me... more Research on visual perception in Autism Spectrum Disorder (ASD) tries to reveal the underlying mechanisms of aberrant local and global processing. Global motion perception is one way to study this aspect of ASD. We used plaid motion stimuli, which can be perceived as a coherently moving pattern, requiring feature integration, or as two transparent gratings sliding over each other. If global motion detection is impaired in ASD, this would lead to a decrease of the total time that a coherent pattern is perceived. However, in contrast to other studies in the literature, our results gave no evidence of impaired global motion perception in people with ASD. A reconciliation of the different outcomes is proposed based on spatial frequency processing in ASD.
PurposeThe effect of methylphenidate (MPH) on inhibitory control as assessed by the stop task in ... more PurposeThe effect of methylphenidate (MPH) on inhibitory control as assessed by the stop task in children with attention-deficit/hyperactivity disorder (ADHD) could be influenced by task difficulty and may be mediated by attention.Subjects and methodsFifteen children with ADHD performed the stop and the change task after placebo, 0.5 and 1.0 mg/kg MPH in a within-subject design.ResultsLinear-trend analysis showed a similar effect of MPH in both tasks and a stronger effect for inhibitory control than for attention. Furthermore, a correlation was found between blood serum metabolites of norepinephrine and dopamine for attentional measures and inhibitory control measures, respectively.Discussion and conclusionIn children with ADHD MPH could act primarily on inhibitory control, and is not influenced by task difficulty. Also, attention and inhibitory control could have differential pharmacological profiles.
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