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- All Subjects: psychology
- All Subjects: MRI
- Status: Published
Method: A finger oscillation (Finger Tapping) test was administered to both ASD (n=21) and TD (n=20) participants aged 40-70 year old participants as a test of fine motor speed. Magnetic resonance (MR) images were collected using a Philips 3 Tesla scanner. 3D T1-weighted and diffusion tensor images (DTI) were obtained to measure gray and white matter volume and white matter integrity, respectively. FreeSurfer, an automated volumetric measurement software, was used to determine group volumetric differences. Mean, radial, and axial diffusivity, fractional anisotropy, and local diffusion homogeneity were measured from DTI images using PANDA software in order to evaluate white matter integrity.
Results: All participants were right-handed and there were no significant differences in demographic variables (ASD/TD, means) including age (51.9/49.1 years), IQ (107/112) and years education (15/16). Total brain volume was not significantly different between groups. No statistically significant group differences were observed in finger tapping speed. ASD participants compared to TDs showed a trend of slower finger tapping (taps/10 seconds) speed on the dominant hand (47.00 (±11.2) vs. (50.5 (±6.6)) and nondominant hand (44.6 (±7.6) vs. (47.2 (±6.6)). However, a large degree of variability was observed in the ASD group, and the Levene’s test for homogeneity of variance approached significance (p=0.053) on the dominant, but not the nondominant, hand. No significant group differences in gray matter regional volume were found for brain regions associated with performing motor tasks. In contrast, group differences were found on several measures of white matter including the corticospinal tract, anterior internal capsule and middle cerebellar peduncle. Brain-behavior correlations showed that dominant finger tapping speed correlated with left hemisphere white matter integrity of the corticospinal tract and right hemisphere cerebellar white matter in the ASD group.
Conclusions: No significant differences were observed between groups in finger tapping speed but the high degree of variability seen in the ASD group. Differences in motor performance appear to be associated with observed brain differences, particularly in the integrity of white matter tracts contributing to motor functioning.
This study investigates the effects of familiarity and the size of a novel object on perception of depth. Familiar size is a visual depth cue that provides information about the distance of an object. This project explores if the familiar size illusion is a result of an automatic perceptual process or an intellectual thought process. This data was collected in two phases, a familiarization phase and a testing phase. The experimental participants were familiarized for 30 seconds with a novel object, while the control group was not shown any objects prior to presentation of test objects. The novel test stimuli were constructed in 5 sizes and participants in the familiar group were familiarized with the medium size object. Participants were then asked to indicate the perceived distance of different sized objects by moving a rod with a pointer at the end to match the distance. The smaller comparison objects subtended visual angles that participants had not previously experienced, while larger comparison objects produced a larger visual angle than the participants had seen during the familiarization phase. The testing phase was identical for both familiar and unfamiliar control groups. Apparent distance was influenced by the size of the objects. Larger objects were judged to be closer than the smaller objects. Participants not familiarized showed smaller effects of stimulus size than the familiarized group. The effect of familiarity was not significant for the smaller stimuli but was very significant for the larger stimuli. The results were not consistent with the cognitive theory which argues that familiar size is a result of a conscious thought process. These outcomes are predicted under the model of familiar size being an automatic perceptual process.