Daniel C. Miller and John Flohr, Texas Woman's University

The purpose of this paper is to present the technology and methods used in topographic brain mapping, examine brain mapping applications to the study of music, and demonstrate the authors' research in music brain mapping. Topographic brain mapping (quantitative EEG) was developed in the late 1970's by Frank Duffy and his colleagues (Duffy, Burchfield, & Lombroso, 1979). The basic equipment needed to conduct quantitative EEG studies includes a personal computer, an analog-to-digital converter, amplifiers, and a mass storage device. There are a number of manufactures who sell quantitative EEG data collection and analysis devices ranging in cost from $15,000 to $150,000.

Brain electrical activity is recorded from electrodes attached to the scalp via paste or sewn into an electrocap. The number of electrodes used ranged from 1 to 128 and is dependent upon the cost of the basic equipment. The greater number of electrodes yields better spatial coverage of brain's functional activation.

During the first half of the 1980's most of the literature related to brain mapping dealt with basic sensory processing. Within the past few years researchers have begun to apply quantitative EEG in the investigation of higher cognitive processing including those involving music. There are several data collection and analyses techniques used in quantitative EEG studies. EEG may be collected during the performance of a cognitive task such as composing music in one's head. The EEG is then mathematically transformed using a Fast Fourier Transformation (FFT) technique. The FFT divides the EEG into common frequencies such as Delta (.5 - 4.0 hz), Theta (4.5 - 8.0 hz), Alpha (8.5 - 12.0 hz), and Beta (12.5+ hz). Researchers then evaluate changes in FFT frequencies as a function of cognitive states.

Another EEG data collection technique involves the creation of event-related potentials (ERPs). A stimulus (e.g., a musical melody) is repeatedly presented to the subject and time-locked EEG is recorded. When multiple trials of time-locked EEG are averaged together, only the activity related to the stimulus event remains.

Researchers have begun to apply these techniques to the study of the processes of music in musicians and non-musicians. It has been commonly suggested that the right cerebral hemisphere plays a dominant role in the processing of musical sounds. Dichotically presented stimuli of musical materials, such as melodies, chords, musical tones, popular songs, singing, and whistling have produced a left-ear advantage. San Martini & Rossi (1988) found a moderate degree of EEG power asymmetry favoring the left hemisphere during a chord recognition task in a sample of adults aged 17 - 30 yrs. However, their data failed to support the hypothesis that individual differences of ear advantage in a dichotic chord test significantly affect the EEG frequencies.

A study that measured the auditory perception of music by topographic brain mapping (Breitling, Gunenther, & Rondot, 1987), examined right-handed normal, adult subjects. Musical material was broken down into a single note, a scale, and a melody. The results of this study revealed a predominance of left mid-temporal electrical activity for the note and scale conditions, and a predominance of right mid-temporal and frontal electrical activity for the melody. Alpha wave production in musicians and non-musicians has been examined in several studies (Wagner, 1975; Wagner & Menzel, 1977; McElwain, 1974, 1979). Consistent findings in these experiments reveal that musicians characteristically produce overall higher levels of alpha rhythms than non-musicians.

Until recently few studies have involved young children. The time necessary to apply the electrodes to a child's head made the use of young subjects prohibitive. Recently, Flohr and Miller (1993) examined EEG differences in children between the ages of four and six between baseline EEG frequencies and EEG frequencies obtained during a psychomotor response to music stimuli. They found a significant increase in the relative power percentages for the theta frequency in the eyes open condition compared to the two music conditions in the sensory motor strip sites (C3 and C4). There were also significant differences within the theta frequency at the right temporal sites and the left anterior temporal site between the eyes open and music conditions which supports previous research findings. Alpha activity decreased at all of the reported sites from the eyes open to music conditions. The motoric output requirement of the task seemed to cause greater cognitive involvement therefore, less alpha activation. Beta II activation decreased at the same sites that showed theta increases which suggest a related effect.

Prior research suggests that although there is a general tendency for the right hemisphere to process musical sounds, the functional lateralization is ultimately determined by the listener’s interest, skills, and relationship to the stimuli. For example, Steinberg, et. al. (1992) found differences between musicians and non-musicians in the alpha frequencies when listening to simple sounds. Ross (1992) summarizes that the neurology underlying musical and artistic creativity is a very complex affair that involves the participation of the whole brain, rather than just the right hemisphere, as currently popularized in the press. Generally, results of experiments involving music processing have been highly dependent upon interacting variables such as the nature of the musical material or the nature of the task.

Participants at this paper session will learn about the application of quantitative EEG techniques to the study of music. The authors will review several illustrative studies within this emerging field including their own research.