Biomedical subjects

Itzhak Aharon

Publications and source records attributed to Itzhak Aharon.

5 recordsLinked to original sources

PubMed2006

Brain activation during semantic processing in autism spectrum disorders via functional magnetic resonance imaging.

Language and communication deficits are core features of autism spectrum disorders (ASD), even in high-functioning adults with ASD. This study investigated brain activation patterns using functional magnetic resonance imaging in right-handed adult males with ASD and a control group, matched on age, handedness, and verbal IQ. Semantic processing in the controls produced robust activation in Broca's area (left inferior frontal gyrus) and in superior medial frontal gyrus and right cerebellum. The ASD group had substantially reduced Broca's activation, but increased left temporal (Wernicke's) activation. Furthermore, the ASD group showed diminished activation differences between concrete and abstract words, consistent with behavioral studies. The current study suggests Broca's area is a region of abnormal neurodevelopment in ASD, which may be linked with semantic and related language deficits frequently observed in ASD.

Adult↗

PubMed2005

Probing reward function in post-traumatic stress disorder with beautiful facial images.

Reward dysfunction may be implicated in post-traumatic stress disorder (PTSD). This study applied a behavioral probe, known to activate brain reward regions, to subjects with PTSD. Male heterosexual Vietnam veterans with (n = 12) or without (n = 11) current PTSD were administered two tasks: (a) key pressing to change the viewing time of average or beautiful female or male facial images, and (b) rating the attractiveness of these images. There were no significant group differences in the attractiveness ratings. However, PTSD patients expended less effort to extend the viewing time of the beautiful female faces. These findings suggest a reward deficit in PTSD.

Beauty↗

PubMed2004

Early visual cortex organization in autism: an fMRI study.

Autism is a neurodevelopmental disorder characterized by preserved visual abilities as well as a special profile for visual cognition. We examined the visual cortex of high-ability individuals with autism in order to assess whether the presence of abnormalities at the primary sensory level in autism could be the basis of their unusual pattern of visual cognitive abilities. We found that the early sensory visual areas are normally organized in individuals with autism, with a normal ratio between central versus peripheral visual field representation. We conclude that the differences observed in the visual capacities of individuals with autism are likely to arise from higher-level cognitive areas and functions, and are the result of top-down processes.

Adolescent↗

PubMed2004

Activation of the fusiform gyrus when individuals with autism spectrum disorder view faces.

Prior imaging studies have failed to show activation of the fusiform gyrus in response to emotionally neutral faces in individuals with autism spectrum disorder (ASD) [Critchley et al., Brain 124 (2001) 2059; Schultz et al., Arch. Gen. Psychiatry 57 (2000) 331]. However, individuals with ASD do not typically exhibit the striking behavioral deficits that might be expected to result from fusiform gyrus damage, such as those seen in prosopagnosia, and their deficits appear to extend well beyond face identification to include a wide range of impairments in social perceptual processing. In this study, our goal was to further assess the question of whether individuals with ASD have abnormal fusiform gyrus activation to faces. We used high-field (3 T) functional magnetic resonance imaging to study face perception in 11 adult individuals with autism spectrum disorder (ASD) and 10 normal controls. We used face stimuli, object stimuli, and sensory control stimuli (Fourier scrambled versions of the face and object stimuli) containing a fixation point in the center to ensure that participants were looking at and attending to the images as they were presented. We found that individuals with ASD activated the fusiform face area and other brain areas normally involved in face processing when they viewed faces as compared to non-face stimuli. These data indicate that the face-processing deficits encountered in ASD are not due to a simple dysfunction of the fusiform area, but to more complex anomalies in the distributed network of brain areas involved in social perception and cognition.

Adult↗

PubMed2003

Cerebral blood flow in depressed patients: a methodological comparison of statistical parametric mapping and region of interest analyses.

Functional brain imaging has assumed a leading role in neuropsychiatric research. However, findings reported for mental disorders often vary. Whether this reflects diversity in pathophysiology or heterogeneity of imaging techniques and data-analytic procedures is still unknown. This study compares region of interest (ROI) and statistical parametric mapping (SPM) analyses of a Tc99m-HMPAO single photon emission computed tomography (SPECT) imaging study of 23 depressed and 21 control subjects. Reduced regional cerebral blood flow (rCBF) was demonstrated by both methods in the right parietal and occipital lobes, but additional regions were identified only on ROI analysis (left temporal) and only on SPM analysis (left parietal). To investigate the contribution of SPM spatial normalization to these discrepancies, further ROI analyses were performed, applying the original ROI templates to normalized images, and applying regions identified by SPM to the original images. This study demonstrated considerable overlap in findings of SPM and ROI analyses. Differences between these methods may be mostly related to subjective placement of ROIs in ROI analysis, and standardized warping inherent in normalization in SPM. Given the advantages and drawbacks of each procedure, the choice of methodology should be determined in accordance with the study design, and complementary use of both methods may be considered.

Adult↗