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Elaine Cristina Zachi, Dora Fix Ventura; Visual Perception and Visual Memory Differences between Asperger Syndrome and High Functioning Autism. Invest. Ophthalmol. Vis. Sci. 2014;55(13):790.
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© ARVO (1962-2015); The Authors (2016-present)
The assumption that Asperger Syndrome (AS) and high functioning autism (HFA) are quantitative manifestations of the same disorder, proposed in the DSM-V remains controversial. We examined possible differences between AS and HFA patients using visual perception and memory tests that preferentially activate magnocellular or parvocellular mechanisms, related respectively to the “weak central coherence” (WCC) and to the “enhanced perceptual function” (EPF) hypotheses.
15 AS patients (age range: 7-15 years old), 18 HFA patients (6-19 years old) and 27 controls (6-19 years old) were tested. Diagnosis was made by psychiatrists from the Psychiatric Institute, University of São Paulo with basis on DSM-IV criteria. Visual perception and memory were assessed with the Cambridge Neuropsychological Test Automated Battery (CANTAB), using tests of spatial memory (Spatial Recognition Memory, SRM), short and long term visual memory (Pattern Recognition Memory, PRM), and perception and memory for complex stimuli presented simultaneously or after short interval (Delayed Matching to Sample, DMS). The participants had intelligence quotients (IQs) in the normal range according to the Wechsler Intelligence Scales.
AS and HFA participants performed significantly worse than controls on the SRM test (ANCOVA with IQ as covariate, p<0.05). HFA patients showed lower scores on PRM in either short or long term recognition trials compared to AS patients and controls (p<0.01). AS participants performed significantly better than the other groups for immediate and delayed perceptual matching (p=0.03).
Memory impairment for spatial information supports the WCC hypothesis” that autistic individuals show deficits in processing contextual structure and motion information, since SRM presents achromatic low spatial frequency stimuli compatible with preferential activation of the magnocellular stream. Nevertheless, AS and HFA patients presented distinct profiles for processing non-structured visual information. HFA participants showed deficits on short and long term memory for shapes, whereas the AS group exhibited a superior performance in perception and memory for fine detailed shapes with saturated chromatic information, compatible with the EPC hypothesis, involving enhancement of parvocellular mechanisms. This study supports the view that AS and HFS may represent qualitatively distinct disorders.
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