Spatial processing in Bálint syndrome and prosopagnosia: a study of three patients.

BACKGROUND: Spatial analysis may be subdivided into between-object and within-object spatial coding. We investigated the contribution of various visual cues to grouping processes that might determine whether single or multiple objects were perceived and therefore which type of spatial coding would be used for a stimulus. METHODS: We asked three patients to make shape judgments with a series of displays showing triangular arrangements, moving from more implicit triangles defined by separate objects at the apices (between-object spatial coding) to more explicit triangles with line edges or surface texture (within-object spatial coding). RESULTS: In two patients with prosopagnosia, within-object spatial judgments were impaired, whereas between-object spatial judgments were normal. In a patient with Bálint syndrome, the reverse pattern was obtained. Surface texture but not outline closure led to mandatory within-object coding in the prosopagnosic patients, whereas outline or surface texture was sufficient to support intact within-object spatial judgments in the patient with Bálint syndrome. Illusory contours were ineffective in promoting within-object coding in either condition. CONCLUSIONS: These findings support the existence of parallel representations of space for within-object and between-object processing and reveal the efficacy of different cues in determining which representation is potentially accessible.

Investigations of face expertise in the social developmental disorders.

BACKGROUND: Patients with social developmental disorders (SDD), also known as autism spectrum disorders, may have impaired recognition of facial identity or facial expressions. OBJECTIVE: Our goal was to determine whether SDDs were characterized by loss of a perceptual mechanism responsible for face expertise, as current theories suggest that such a loss should be selective for upright faces, disproportionately affect the perception of facial configuration, and possibly be more severe in the eye region. METHOD: We tested a group of 24 adult patients with SDD with an oddity paradigm that required them to detect changes in facial configuration or feature color, in either the eyes or the mouth, in both upright and inverted faces. RESULTS: One group of subjects with SDD with normal famous face recognition had only a mild reduction in accuracy and a normal pattern of inversion effects. A second group of subjects with SDD with impaired famous face recognition had a severe reduction of accuracy. This deficit was not limited to upright faces. It affected the perception of feature configuration and feature color to a similar degree and both eye and mouth changes were discriminated poorly in upright faces. CONCLUSION: The impaired face recognition that is present in a subset of patients with social developmental disorders is accompanied by impaired face perception, and this impairment is not exclusive to upright faces, facial configuration, or the eye region. The reduced face processing skills in these subjects may be more consistent with recent computational models of face expertise than with classic dual-route hypotheses.

Perception of facial expression and facial identity in subjects with social developmental disorders.

BACKGROUND: It has been hypothesized that the social dysfunction in social developmental disorders (SDDs), such as autism, Asperger disorder, and the socioemotional processing disorder, impairs the acquisition of normal face-processing skills. The authors investigated whether this purported perceptual deficit was generalized to both facial expression and facial identity or whether these different types of facial perception were dissociated in SDDs. METHODS: They studied 26 adults with a variety of SDD diagnoses, assessing their ability to discriminate famous from anonymous faces, their perception of emotional expression from facial and nonfacial cues, and the relationship between these abilities. They also compared the performance of two defined subgroups of subjects with SDDs on expression analysis: one with normal and one with impaired recognition of facial identity. RESULTS: While perception of facial expression was related to the perception of nonfacial expression, the perception of facial identity was not related to either facial or nonfacial expression. Likewise, subjects with SDDs with impaired facial identity processing perceived facial expression as well as those with normal facial identity processing. CONCLUSION: The processing of facial identity and that of facial expression are dissociable in social developmental disorders. Deficits in perceiving facial expression may be related to emotional processing more than face processing. Dissociations between the perception of facial identity and facial emotion are consistent with current cognitive models of face processing. The results argue against hypotheses that the social dysfunction in social developmental disorder causes a generalized failure to acquire face-processing skills.