Neuropsychologia
-
Comparative Study
Impaired recognition of facial emotions from low-spatial frequencies in Asperger syndrome.
The theory of 'weak central coherence' [Happe, F., & Frith, U. (2006). The weak coherence account: Detail-focused cognitive style in autism spectrum disorders. Journal of Autism and Developmental Disorders, 36(1), 5-25] implies that persons with autism spectrum disorders (ASDs) have a perceptual bias for local but not for global stimulus features. ⋯ The two groups recognized emotions similarly from non-filtered faces and from dynamic vs. static facial expressions. In contrast, the participants with AS were less accurate than controls in recognizing facial emotions from very low-spatial frequencies. The results suggest intact recognition of basic facial emotions and dynamic facial information, but impaired visual processing of global features in ASDs.
-
Comparative Study
Perceptual load affects spatial and nonspatial visual selection processes: an event-related brain potential study.
One major question toward understanding selective attention regards the efficiency of selection. One theory contends that this efficiency in vision is determined primarily by the perceptual load (PL) imposed by the relevant stimuli; if this load is high enough to fill attentional capacity, irrelevant stimuli will be excluded before they interfere with task performance, but if this load is lower the spare capacity will be directed automatically to the irrelevant information, which will then interfere with task performance. ⋯ PL was manipulated by varying the similarity between the target/deviant and standard stimulus, and increases in PL were found to increase the magnitude of the relevant-irrelevant difference waveforms in both tasks at predicted temporal windows. These findings suggest that PL affects attentional selection that is tonically maintained across many experimental trials, and does so not only when selection is spatially based but also when it is based upon nonspatial cues.
-
The hippocampus is the brain structure of highest and earliest structural alteration in Alzheimer's disease (AD). New developments in neuroimaging methods recently made it possible to assess the respective involvement of the different hippocampal subfields by mapping atrophy on a 3D hippocampal surface view. In this longitudinal study on patients with mild cognitive impairment (MCI), we used such an approach to map the profile of hippocampal atrophy and its progression over an 18-month follow-up period in rapid converters to AD and "non-converters" compared to age-matched controls. ⋯ Moreover, the CA1 subfield also showed highest atrophy rates during follow-up, in both rapid converters and "non-converters" although increased effects were observed in the former group. This study emphasizes the differences between normal aging and AD processes leading to hippocampal atrophy, pointing to a specific AD-related CA1 involvement while subiculum atrophy would represent a normal aging process. Our findings also suggest that the degree of hippocampal atrophy, more than its spatial localization, predicts rapid conversion to AD in patients with MCI.
-
A recent study showed that motor imagery was compromised after right congenital hemiparesis. In that study, posture of the displayed stimuli and the actual posture of the hand making the response were incongruent. Ample evidence exists that such an incongruency may negatively influence laterality judgements in a mental rotation task. ⋯ However, reaction times for the participants with hemiparesis were consistently slower compared to controls and no asymmetry in responding between the affected and less-affected hand was found, suggesting a visual imagery strategy. Collectively, these results suggest that the ability to mentally rotate stimuli is still intact in right hemiparesis. The results are discussed in relation to two strategies that may have been used to solve the task: visual imagery and motor imagery.
-
Recent observations indicate that sex and level of steroid hormones may influence cortical networks associated with specific cognitive functions, in particular visuo-spatial abilities. The present study probed the influence of sex, menstrual cycle, and sex steroid hormones on 3D mental rotation and brain function using 3-T fMRI. Twelve healthy women and 12 men were investigated. ⋯ Our study provides evidence that fMRI-related activity during performance of cognitive tasks varies across sex and phases of the menstrual cycle. The variation might be partly explained by better task performance in men, but our results indicate that further explanations like basic neuronal or neurovascular effects modulated by steroid hormones must be considered. Both estradiol and testosterone levels may influence fMRI signals of cognitive tasks, which should affect selection of subjects for future fMRI studies.