70 CHAPTER 2
function, such as structural changes associated with different levels of memory perfor-
mance, and various disorders and conditions including Alzheimer ’s disease, MS, and
traumatic brain injury (Hayes et al., 2016; Ly et al., 2016; Muthuraman et al., 2016; Wang
et al., 2016).MAPPING FUNCTION In addition to imaging the different parts of the brain to under-
stand what may or may not be present, examining the function of the brain is also
important in understanding behavior and mental processes.THE ELECTROENCEPHALOGRAM (EEG) As important as imaging brain structure is, it
is sometimes important to know how different brain areas function. A fairly harmless
way to study the activity of the living brain is to record the electrical activity of the
cortex just below the skull using a device called an electroencephalograph. The first
electroencephalogram (EEG) recording in humans was accomplished in 1924 by Hans
Berger (Niedermeyer, 2005). Recording the EEG involves using small metal disks or
sponge-like electrodes placed directly on the scalp and a special solution to help con-
duct the electrical signals from the cortex just below. These electrodes are connected to
an amplifier and then to a computer to view the information. The resulting electrical
output forms waves that indicate many things, such as stages of sleep, seizures, and
even the presence of tumors. The EEG can also be used to help determine which areas
of the brain are active during various mental tasks that involve memory and attention.
EEG activity can be classified according to appearance and frequency, and different
waves are associated with different brain activity. For example, alpha waves in the back
of the brain are one indication of relaxed wakefulness (seen in bottom two lines in Fig-
ure 2.11a). EEG waveforms are covered in more detail in Chapter Four. to
Learning Objective 4.5.
Another common EEG–based technique focuses on event-related potentials, or
ERPs. In ERP studies, multiple presentations of a stimulus are measured during an
EEG and then averaged to remove variations in the ongoing brain activity that is
normally recorded during the EEG. The result is a measurement of the response of
the brain related to the stimulus event itself, or an event-related potential. ERPs allow
the study of different stages of cognitive processing. For example, the use of ERPs
has allowed researchers to investigate differences in brain processing associated
with the recognition of facial expression of emotion in individuals with and without
schizophrenia (Lee et al., 2010). In other studies, ERPs are being studied as a possi-
ble method of lie detection (Hu et al., 2013; Labkovsky & Rosenfeld, 2014; Rosenfeld
et al., 2008).electroencephalogram (EEG)
a recording of the electrical activity
of large groups of cortical neurons
just below the skull, most often using
scalR electrodes.
Figure 2.11 Mapping Brain Function
Various methods for mapping brain function. An EEG record is shown in 2.11a, a PET scan image in 2.11b, and an image from an fMRI study in 2.11c. Data and
figure for 2.11a courtesy of N. White.
Interactive