Cognitive Neuroscience and Neuropsychology

Specific learning disabilities are a class of disorders that arise from neurodevelopmental abnormalities. The social–emotional processing disorder (SEPD), which has also been referred to as the non-verbal learning disability and the right-hemisphere learning disability, is a syndrome thought to arise from congenitally or early acquired damage to the right hemisphere.1 It is characterized by a history of deficient interpersonal relations, usually reflected in extreme shyness; difficulties interpreting and producing paralinguistic (non-verbal) aspects of communication including prosody, facial expression and gesture; and impaired visuospatial relative to verbal abilities. Associated features include poor emotional adjustment and psychiatric disorder, particularly depression, and deficient academic achievement in arithmetic but not in basic linguistic abilities.1,2 SEPD has been associated with right hemisphere dysfunction on the basis of the neuropsychological profile and the findings of neurological examination, neurophysiological studies and neuroimaging studies.1–4 In normal adults the right hemisphere provides the primary neuroanatomical substrate for the spatial distribution of attention.5,6 This large-scale neurocognitive network has its principal anatomical components in the prefrontal and posterior parietal cortices and the cingulate gyrus regions which, in animals, regulate both shifts of attention and accompanying shifts of gaze.7 The frontal eye field triggers saccades concerned with the intentional exploration of the visual environment, including correct antisaccades, while the parietal eye field triggers saccades made reflexively in response to the appearance of a visual target.8 Individuals with SEPD have attention deficits, but these deficits have not been well characterized.1 The purpose of this study was to better delineate the nature and anatomical substrate of spatial attention deficits in SEPD by using validated experimental eye movement protocols that are linked to specific anatomical components of the right hemisphere network. Eye movement measurements serve as objective, physiologically based indices of visual attention. We hypothesized that individuals with SEPD would exhibit deficits in specific aspects of spatially directed attention on the basis of presumed right hemisphere dysfunction. In particular, we expected that they would have difficulty with complex intentional aspects of visual attention. We tested this with an antisaccade protocol which requires the inhibition of a reflexive saccade and the substitution of an intentional gaze in the direction opposite the appearance of a target. We did not expect SEPD subjects to show difficulty with prosaccade which involves a more reflexive gaze to a visual target or with the simple maintenance of fixation in the absence of distraction. We did not expect to see any deficits in visual attention on these tasks in either normal or dyslexic control groups. Cognitive Neuroscience and Neuropsychology