In early history, researchers were not fortunate enough to explore the brain without having to do invasive procedures. A great example of a pioneer neurosurgeon that explored the human brain invasively was Wilder Penfield. In 1934 he founded the  Montreal Neurological Institute in Canada. In this institute he would perform procedures with precision. Penfield would have a patient that is fully awake with his/her brain exposed. Here, Penfield and his team would carefully record movements as well as verbal reports of the sensation that has been brought forth by an electric stimulus. This procedure provided the first direct, systematic evidence of how the human cerebral cortex is systematically organized. (Howard et al, 2012).

Now in order to see functions within the brain, researchers and or doctors can use noninvasive procedures. Within the last six decades, technology has advanced enough to allow researchers to examine the patients normal and impaired brain function by using these noninvasive procedures. We can go over a few examples.

One of the first noninvasive procedures that was developed was called Electroencephalography (EEG). This works by measuring the electrical activity across the humans scalp, measuring the flow of action potentials. The electroencephalogram (EEG) can help diagnose epilepsy, sleep disorders, and brain tumors.

Another technology that builds the map of the brain but is not recommended to be done often is the Positron emission tomography (PET) scan. This measures the brain based on changes in the flow of blood. PET scans can be extremely helpful by detecting cancers and other organs that are not working properly.

Not only can you use an MRI for other parts of the body, it can also be used for examining the brain. Magnetic Resonance Imaging (MRI) can also create a detailed map of the brain. A much extensive form to use is a Function Magnetic Resonance Imaging (fMRI).  According to Frontiers for Young minds, the fMRI can measure activity without opening the skull, thus being a noninvasive procedure. It functions by using the bloods magnetic properties, it can detect changes in blood flow related to brain activity. (Amanamba et al, 2020).

References:

Amanaba, U., Sojka, A., Harris, S., Bucknam, M., & Hegde, J. (2020). Retrieved from https://kids.frontiersin.org/articles/10.3389/frym.2020.484603#:~:text=fMRI%20can%20measure%20brain%20activity,are%20more%20active%20than%20others.

Department of Health & Human Services. (2002). Retrieved from https://www.betterhealth.vic.gov.au/health/conditionsandtreatments/eeg-test

Howard, M. A., Nourski, K. V., & Brugge, J. F. (2012). Retrieved from https://www.healthcare.uiowa.edu/Labs/hbrl-neurosurgery/pub_pdf/2012_Howard_Springer.pdf