Over the years, a large compilation of fMRI data from hundreds of studies has essentially allowed for a road map of different brain networks in healthy individuals. fMRIs have elucidated these networks by allowing researchers to observe different regions of the brain when they "light up" during different cognitive tasks through measuring levels of oxygenated blood flow in different regions of the brain. The 6 patients in this study underwent high quality fMRI scans in order to compare their remaining neuro-networks with those understood in healthy individuals. Seven brain regions responsible for major functions such as attention, movement, and vision were observed and measured for activity levels (Kliemann et al., 2019). Researchers were shocked to find increased connectivity between different networks, especially since the global precedent for networks in healthy individuals is general stronger connectivity within individual networks with comparatively less connectivity between different network regions (Kliemann et al., 2019). Kliemann and his team actually expected to possibly find a rearrangement of the networks in the single hemisphere of these patients.
For all of the work done in trying to understand the integration and segregation of brain networks, these findings have added an intriguing component (Kliemann et al., 2019). Understanding the different connections and networks in the brain are key for understanding the cognitive changes in various brain injuries as well as understanding current and future treatment options.
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| Figure 1. Hemispherectomy Brain Anatomy (Kliemann et al.) |
References:
Kliemann, D., Adolphs, R., Tyszka, J. M., Fischl, B., Yeo, B. T. T., Nair, R., … Paul, L. K. (2019). Intrinsic Functional Connectivity of the Brain in Adults with a Single Cerebral Hemisphere. Cell Reports, 29(8), 2398-2407.e4. https://doi.org/10.1016/j.celrep.2019.10.067
I did a brain dissection in undergrad on a brain that had a an 1/8 of the cerebrum missing from a stroke. Even with severe tissue loss, the individual lived for years after, which was evident through the scar tissue. But with the study you describe, I was very interested to learn that hemispherectomies cause little to no cognitive impairment in individuals. Originally I thought that the recovery of full cognition was due to the fact that this study focused on children who had this procedure. Children's brains are incredibly plastic, so a full recovery after such an intense procedure seems possible. However, cohort studies show that even adults who undergo hemispherectomies have surprisingly few cognitive disabilities afterwards (Schusse, Smith & Drees, 2018). My biggest question regarding hemispherectomies, is how do surgeons deal with brain areas that are unilateral in adults? Some language and motor areas do not exist on both sides of the brain, so in a fully differentiated adult brain, what happens when this brain area is taken out and how is function not impaired?
ReplyDeleteThis was a very interesting article, thank you for sharing!
References:
Schusse, C. M., Smith, K., & Drees, C. (2018). Outcomes after hemispherectomy in adult patients with intractable epilepsy: institutional experience and systematic review of the literature. Journal of Neurosurgery, 128(3), 853–861. doi: 10.3171/2016.9.jns151778