By Gregory Brown, MD/PhD Candidate
In neurology, we are taught localization, localization, localization. Each region of the brain serves a certain function. And damage to those regions, causes dysfunction.
Damage to a region called Broca’s area leads to difficulty forming and reading sentences. Patients speak in short one-word sentences, called telegraphed speech. On the other hand, damage to a region called Wernicke’s area causes patients to speak in meaningless babble, or word vomit.
However, evidence suggests the brain is not simply individual regions with individual functions. The brain actually works in a network, and damage to any part of the network can lead to dysfunction.
Scientists from Harvard Medical School identified that lesions in brain networks, instead of specific regions, could explain functional impairments.
Patients with similar symptoms of visual hallucinations received MRI of their brain. Indeed, these patients’ brains had lesions (areas of damage), but the lesions did not overlap. The damage could not be localized to an individual region.
But when the scientists investigated the brain connections. They realized the damage was within the same visual circuit. This finding indicates that damage at any point in a brain circuit can result in similar types of problems.
This is a powerful advancement in the field of neurology. Understanding the brain as a connected network as opposed to modular regions is a big change in thinking.
But logically, we understand the highly connected nature of the brain and the multiple pathways that exist. People have shown outstanding capability to recovery from brain injury due to these redundant pathways.
The application for this work is to identify methods to intervene in network-based damage.
This could be used to identify how disease may damage a network, but individual hubs may be a target for treatment.
For example, random lesions in the brain actually resulted in relief of patients’ essential tremor. These lesions were all in a network that included the thalamus as a hub. The thalamus was identified as an important region for essential tremor by years of trial and error.
Future work into other diseases, may help identify these hubs faster and easier.
Methods currently exist to modulate brain activity. These include deep brain stimulation for Parkinson’s disease or transcranial magnetic stimulation for depression. Determining which network is damaged could provide a target for the therapies.
A better understanding of how regions of the brain is important for knowing about brain function.
But it is also nice to see direct work with clinical applications related to the diagnosis and treatment of brain diseases.
Maybe this work may help us understand other brain illnesses that are more diffuse. Such as depression or bipolar disease.
Neurology might still have the localize mindset, but now it will be localization to brain networks, instead of specific regions.