A network-level approach of cognitive flexibility impairment after surgery of a right temporo-parietal glioma.

OBJECTIVE: The right "non-dominant" temporo-parietal junction is usually not considered as a highly eloquent area. This contrasts with its mirrored left "dominant" counterpart, which is known as highly eloquent regarding language function. The question arises about which functions should be monitored when operating lesions of the right temporo-parietal junction under awake conditions. METHODS: We report the case of a patient who underwent a surgical resection of a glioma located in the right temporo-parietal junction. Cognitive evaluations were performed preoperatively and 4 months after surgery, as well as resting state fMRI and diffusion-based tractography. RESULTS: Long-term postoperative cognitive examination revealed an important deterioration of cognitive control abilities, especially regarding set-shifting abilities as measured by Trail making test part B. Based on pre- and postoperative resting state fMRI and diffusion-based tractography, we demonstrate that surgical resection massively impacted structural and functional connectivity of the right fronto-parieto-temporal network, a network that is classically involved in cognitive control, reasoning and working memory. CONCLUSION: This case clearly illustrates how a white matter focal lesion can generate a neuropsychological deficit by remotely disconnecting distant cortical areas belonging to a functional network. Furthermore, our observation strongly supports the use of intraoperative cognitive control tests during surgery of the right temporo-parietal junction and promote the interest of pre and postoperative resting state functional connectivity to explore the potential mechanisms causing cognitive deficits.

Sex differences in frontal lobe connectivity in adults with autism spectrum conditions.

Autism spectrum conditions (ASC) are more prevalent in males than females. The biological basis of this difference remains unclear. It has been postulated that one of the primary causes of ASC is a partial disconnection of the frontal lobe from higher-order association areas during development (that is, a frontal 'disconnection syndrome'). Therefore, in the current study we investigated whether frontal connectivity differs between males and females with ASC. We recruited 98 adults with a confirmed high-functioning ASC diagnosis (61 males: aged 18-41 years; 37 females: aged 18-37 years) and 115 neurotypical controls (61 males: aged 18-45 years; 54 females: aged 18-52 years). Current ASC symptoms were evaluated using the Autism Diagnostic Observation Schedule (ADOS). Diffusion tensor imaging was performed and fractional anisotropy (FA) maps were created. Mean FA values were determined for five frontal fiber bundles and two non-frontal fiber tracts. Between-group differences in mean tract FA, as well as sex-by-diagnosis interactions were assessed. Additional analyses including ADOS scores informed us on the influence of current ASC symptom severity on frontal connectivity. We found that males with ASC had higher scores of current symptom severity than females, and had significantly lower mean FA values for all but one tract compared to controls. No differences were found between females with or without ASC. Significant sex-by-diagnosis effects were limited to the frontal tracts. Taking current ASC symptom severity scores into account did not alter the findings, although the observed power for these analyses varied. We suggest these findings of frontal connectivity abnormalities in males with ASC, but not in females with ASC, have the potential to inform us on some of the sex differences reported in the behavioral phenotype of ASC.