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Joumalofpsychophysiology 12 (1998) 113-126
© 1998 Federation of European Psychophysiology Societies
Developmental changes in the theta response system:
a single sweep analysis
Juliana Yordanova and Vasil Kolev
Institute of Physiology, Bulgarian Academy of Sciences, Sofia, Bulgaria
Accepted for publication: March 13, 1997
Keywords: Event-related potentials, theta response, phase-locking, children, EEG
Abstract Recently, increased interest has been focused on the EEG frequency responses in the theta
(4-7 Hz) range because of their association with stimulus information processing. However, it is not known
whether the event-related theta response depends on the development of the spontaneous theta activity and
how it varies with age in children. In the present study, a single-sweep analysis was performed to assess
the developmental changes in event-related EEG theta activity. Auditory passive, oddball target, and
standard event-related potentials (ERPs) were recorded at Fz, Cz, and Pz from 50 children aged 6-11
years and 10 young adults. Theta responses were analyzed in two time windows of the post-stimulus epochs
for three single-sweep parameters: amplitude, phase-locking with stimulus, and enhancement relative to
prestimulus activity. For all three types of stimuli, adults had theta responses with lower amplitude, higher
enhancement, and stronger phase-locking than those of children. Unlike adults, no reliable differences
between the early and late theta response were found for children. Significant developmental changes were
observed for theta response amplitude, which decreased, and phase-locking of early theta responses, which
increased, with advancing age. These findings indicate that the theta component of the auditory ERP differs
remarkably between children and adults and undergoes developmental alterations, possibly reflecting
specific differences in stimulus information processing.
Introduction
After external stimulation oscillatory electro-
encephalographic (EEG) responses in differ-
ent frequency ranges (theta, alpha, gamma,
etc.) can be recorded from the brain (Ba§ar &
Bullock, 1992). These oscillatory EEG respons-
es have been proposed to originate from the
event-related reorganization of the ongoing
EEG as reflected by the synchronization, mag-
nitude enhancement or damping, and phase-
reordering of the EEG after stimulation
(Ba§ar, 1980,1992; Parvin, Torres, & Johnson,
1980; Sayers, Beagley, & Henshall, 1974). With-
in this framework, the EEG frequency re-
sponses are strongly associated with the back-
ground EEG activity. Given the natural chang-
es in the spontaneous EEG in the course of
development (Niedermeyer, 1993), as well as
the functional relevance of event-related oscil-
lations (Ba⅛>ar, Hari, Lopes da Silva, & Schiir-
mann, 1997; Pantev, Elbert, & Liitkenhoner,
1994), the analysis of the EEG frequency re-
sponses in children might provide a useful
physiological approach for studying develop-
mental brain functioning.
Event-related oscillations in the theta fre-
quency range (4-7Hz) define the theta fre-
quency component of the event-related brain
potentials (ERPs) or the EEG theta response.
Prominent theta responses have been ob-
served in various experimental conditions in
both humans and animals and have been as-
signed an important role in integrative stimu-
lus processing (Miller, 1991; Schiirmann &
Ba⅛ar, 1994). The scalp recorded theta respons-
es have been proposed to reflect the function-
ing of a diffuse and distributed theta system in
the brain (Ba§ar-Eroglu, Ba§ar, Demiralp, &
Schiirmann, 1992) involving primarily the hip-
pocampus and associative frontal cortex
(Ba§ar-Eroglu et al., 1992; Demiralp & Ba§ar,
1992; Klimesch, Schimke, & Schwaiger, 1994;
Miller, 1991) and generating both the sponta-
neous and elicited theta oscillations (Basar,
1992).