Cortical Functional Mapping by High-Resolution EEG - Quantitative EEG Analysis Methods and Clinical Applications - page 355

CHAPTER 13
Cortical Functional Mapping by
High-Resolution EEG

Laura Astolfi, Andrea Tocci, Fabrizio De Vico Fallani, Febo Cincotti, Donatella
Mattia, Serenella Salinari, Maria Grazia Marciani, Alfredo Colosimo, and
Fabio Babiloni

We present a methodology to assess cortical activity by estimating statistically sig-
nificant sources using noninvasive high-resolution electroencephalography
(HREEG). This implies the estimation of the cortical distributed sources of the
HREEG data acquired during the execution of different tasks and the estimation of
the cortical power spectra in the selected frequency bands relative to each task
A nalyzed. The aim of the procedure developed is to assess straightforwardly signifi-
cant differences between the cortical activities related to different experimental
tasks. Such information is not appreciable by using conventional mapping proce-
dures in the time domain. Furthermore, the same methodology allows us to separate
from the cortical activity caused by the normal activity of the brain any statistically
significant current density estimates related to the experimental task.

13.1 HREEG: An Overview

Information about brain activity can be obtained by measuring different physical
variables arising from the brain processes, such as the increase in consumption of
oxygen by the neural tissues or a variation of the electric potential over the scalp
surface. All of these variables are connected in direct or indirect ways to the ongoing
neural processes, and each variable has its own spatial and temporal resolution. The
different neuroimaging techniques are thus confined to the spatiotemporal resolu-
tion offered by the variables being monitored. Human neocortical processes involve
temporal and spatial scales spanning several orders of magnitude, from the rapidly
shifting somatosensory processes characterized by a temporal scale of milliseconds
and a spatial scale of few square millimeters to the memory processes, involving
time periods of seconds and spatial scale of square centimeters. Today, no
neuroimaging method allows a spatial resolution on a millimeter scale and a
temporal resolution on a millisecond scale.

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