Warren, D., Power, J., Bruss, J., Denburg, N., Waldron, E., Sun, H., Steven, P., Tranel, D. (2014). Network measures predict
neuropsychological outcome after brain injury. Proceedings of the National Academy of Sciences of the United States of America, 111(39), 14247-142520.
An investigation shows that damage to regions with higher system density produce higher deficits but damage to other locations produce certain deficits. Hubs are network components that indicate potential points of importance for network function but research cannot locate where hubs are. The geography of the brain is known for being able to locate brain damage and small lesions in the brain would have a bigger effect than what its thought to have. Following circumscribed lesions, severe cognitive and behavioral consequences of explanations would be broad. A view of hubs focuses on the number of connections between regions and another view is that regions of the default mode network(DMN) would have high ratings on measures of network importance. Degree measures the number of connections and a degree may not reflect the importance of a node to network function. It is predicted that lesions of brain regions showing activity with many brain systems would produce large effects on the brain and this is split into different systems based on activity from the fMRI. There are two predictions and the first one is that lesions located in higher density will affect processing and will produce impairment but the second prediction is that the lesions located with low scores will have less consequences.
An investigation took place with 30 patients, 19 with focal lesions to six target and 11 with focal lesions to two control, and the prediction of this investigation was that damage to the brain regions would be more direct to and participate with more brain systems. The results of this investigation was that lesion sizes were not very different between the two groups but the control group was larger than the target group. Neuropsychological reports were reviewed by psychologist to rate the patient’s degree of impairment. The results of the impairment ratings showed that all nine domains were present in the patients with target lesions but only seven of the nine domains were presents in the patients with lesions to target locations. The average domain of a target lesion producing impairment is 6.89 but the average domain of control lesions producing impairment is 2.64. Follow-up analysis were performed and no evidence was found that the main finding was accounted for by other factors other than location of the lesion.
The lesions were beyond the target and control regions of interest and locations which is why it is important to determine if the tissue that was lesioned had network properties that was needed to isolate the target and control locations. Lesion masks were used to extract the network properties of the corresponding tissues and measures of the sample degree was less well with expectations. When lesion sampling, neither idealized nor observed measure of degree predicted cognitive outcomes but participation was the best predictor. Severe and large cognitive impairment was produced when there was damage to target locations. Patients have different degrees of impairment and recover differently. Communication between functional systems can be affected by focal regions centered on high brain regions. Control lesions tended to damage less systems that target lesions would. Support was found when systems were affected by lesions. Degree does not identify regions of broad importance. Language impairment was common in the target group even though many target group patients had normal language. This investigation shows the differences in the effects of the groups and the location of the lesions.