Table 5.

Explanation of Imaging studies.

Imaging Study	How It Works
Single-photon emission C.T. (SPECT) [24]	It creates a 3D image by the representation of a radioactive tracer (e.g., technetium-99 m) inserted in the body, allowing the identification of functionality and perfusion of different tissues, in this case, the brain.
Functional M.R.I. (fMRI) [25]	It measures hemodynamic response induced by neuronal activity and measured though a blood oxygen level dependent (BOLD) signal which depends on oxy/deoxy haemoglobin concentration.
Fluorodeoxyglucose positron emission tomography (FDG-PET) [26]	F.D.G. is a glucose analog metabolized by tissues with a high glucose demand (e.g., cancers, heart, and brain) and is measured using a tracer. In that way, this study allows us to identify brain activity by measuring the uptake of F.D.G. and indirectly measuring the blood flow through the brain.