It has long been known that the brain uses topographic organization, meaning that parts of the brain that make similar types of computations are situated close to each other (also known as brain maps or spatial computation). However, in the case of pathology, these topographies may undergo re-organization. The researchers now show that it is the continuity of these brain maps which is disturbed. Moreover, this continuity can be quantified, allowing them to be used as a biomarker for detecting neuropsychiatric disease.
Using functional MRI, they studied two types of unique patient populations: patients with injury to one side of the spinal cord, which enabled comparison of disturbed and non-disturbed body sides, and patients undergoing surgical repair.
This approach enabled direct comparison in human patients with respect to their own self or before and after surgical intervention. Instead of inducing lesions in animals, the team could repair the human patients and check them before and after. Importantly, unlike animals, patients could report their subjective experience, which is crucial for understanding high cognitive functions and neuropsychiatry.
The researchers developed an algorithm that quantifies continuity of the patients' brain maps. Their results showed that in each individual patient, pathological processing was reflected by a discontinuity of topographic maps rather than signal reduction.
"These findings suggest that continuity is a primary principle in brain computation, but in pathological states the brain may give up on this principle in order to retrieve as much information as possible," said neuroscientist, who led the team. "Moreover, this may serve as a biomarker for neurological pathologies that we are now investigating."
The researchers are now fine-tuning their findings in neurosurgical patients in order to enable a better patient-tailored diagnosis and follow-up. In addition they are extending their findings to other kinds of brain processing such as vision, hearing, number processing and memory.