Additional resources and the default mode network: Evidence of increased connectivity and decreased white matter integrity in amyotrophic lateral sclerosis

Abstract

In amyotrophic lateral sclerosis (ALS), cognition is affected. Cortical atrophy in frontal and temporal areas has been associated with the cognitive profile of patients. Additionally, reduced metabolic turnover and regional cerebral blood flow in frontal areas indicative of reduced neural activity have been reported for ALS. We hypothesize that functional connectivity in non-task associated functional default mode network (DMN) is associated with cognitive profile and white matter integrity. This study focused on specific cognitive tasks known to be impaired in ALS such as verbal fluency and attention, and the relationship with functional connectivity in the DMN and white matter integrity. Nine patients and 11 controls were measured with an extensive neuropsychological battery. Resting-state functional magnetic resonance imaging (fMRI) and diffusion tensor imaging (DTI) data were acquired. Results showed that ALS patients performed significantly worse in attention and verbal fluency task. Patients showed increased functional connectivity in parahippocampal and parietal areas of the non-task associated DMN compared to controls. The more pronounced the cognitive deficits, the stronger the increase in functional connectivity in those areas. White matter integrity was reduced in frontal areas in the patients. In conclusion, increased connectivity in the DMN in parahippocampal and parietal areas might represent recruitment of accessory brain regions to compensate for dysfunctional frontal networks.

Key words::

• Default mode network
• cognition
• amyotrophic lateral sclerosis (ALS)
• cortical plasticity
• fMRI

Acknowledgements

This was an EU Joint Programme – Neurodegenerative Disease Research (JPND) project. The project is supported through the following organizations under the aegis of JPND – www.jpnd.eu, e.g. Germany, Bundesministerium für Bildung und Forschung (BMBF, FKZ), Sweden, Vetenskaprådet Sverige, and Poland, Narodowe Centrum Badán i Rozwoju (NCBR). This work was supported by the Deutsche Forschungsgemeinschaft and the BMBF.

Declaration of interest: The authors declare that they have no conflict of interest. The authors alone are responsible for the content and writing of the paper.