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COPYRIGHT 2006 University of South Alabama
Throughout the last twenty-five years studies have examined changes in electroencephalogram (EEG) laterality as elite athletes have prepared to execute a motor act, such as shooting a bow and arrow or rifle, or performing a golf putt (Bird, 1987; Hatfield, Landers, & Ray, 1984; Hillman, Apparies, Janelle, Hatfield, 2000; see Hatfield, Haufler, Hung, & Spalding, 2004 for a review). However, relatively few studies have examined the EEG correlates of performance for novice athletes during a similar preparatory period. This is largely due to the emphasis placed on research designed to investigate "peak" or "ideal" performance, with its direct application to providing a competitive edge in sports (Williams & Krane, 1998).
In addition, while social facilitation/inhibition is one of the oldest and most researched areas in sport psychology, there are virtually no studies that examine how the presence of an audience affects EEG lateralization patterns within the sports literature (see Saarela, 2000; and see Davidson, Marshall, Tomarken, & Henriques, 2000 for EEG and public speaking). This is particularly surprising given the aforementioned emphasis on researching issues relevant to competitive sport, which has as a hallmark the presence of an audience. The current study seeks to expand on the work of Crews and Landers (1993) by exploring the shifts in EEG laterality that occur prior to a golf putt made by novice golfers who were assigned to putt alone and also in front of an audience.
Electroencephalogram (EEG)
The electroencephalogram represents a record of fluctuations in the electrical activity of the brain recorded from the surface of the scalp. The EEG records potential changes, which are generated by the summed ionic currents of many thousands of cortical neurons. The EEG represents the excitatory and/or inhibitory post-synaptic potentials recorded primarily from the apical dendrites of pyramidal neurons in neocortex. The frequencies of the potentials recorded from the surface of the scalp of a normal human vary from 1 to 50 Hz, and the amplitudes typically range from 20 to 100uV (Neidermeyer & Lopez da Silva, 1999). Four dominant frequency ranges are typically observed: alpha, beta, delta and theta. Theta and delta activity predominate during sleep, and as such, are not reviewed further here. Since the present study focused on participants during a waking state, only alpha and beta were analyzed in the present study and will be reviewed further.
Beta waves are normally seen more diffusely during intense mental activity, and have frequencies ranging from 13 to 30 Hz. Beta waves have the smallest amplitudes of recorded EEG activity (Neidermeyer & Lopez da Silva, 1999). For the present study, beta was broken down into beta 1 (13 to 21 Hz) and beta 2 (21-30), in order to replicate previous research. Beta 2 frequencies seem to be particularly active in schizophrenics and highly anxious performers (Ramos, Cerdan, & Guevara, 2001).
Alpha waves, which range in frequency from 8 to 13 Hz, are sometimes called Berger rhythm, after Hans Berger who first identified them. Alpha waves are generally associated with a state of relaxed wakefulness, especially visible in occipital regions when the eyes are closed. An increase in alpha amplitude in a task has frequently been linked to cortical deactivation (Kimura et al., 2001), especially in the sport psychology literature (Hatfield et al., 1984; Rebert, Low, & Larson, 1984; Crews & Landers, 1993).
Studies of EEG Asymmetry Prior to the Execution of a Motor Act
Several investigations have explored the relationship between EEG asymmetry prior to performing a motor act and subsequent athletic performance. Hatfield and Hillman (2000, p. 362) provide an excellent review of this literature, which begins with the work of Pullum (1977) indicating that better shooting accuracy was associated with an "enhanced" alpha state. Hatfield went on to complete a series of studies to more thoroughly investigate changes in alpha activity as elite marksmen prepared to fire their rifles. Hatfield, Landers, Ray, and Daniels (1982) reported that the left hemisphere showed relatively greater alpha activity than the right hemisphere as the time to pull the trigger approached. This effect was replicated by Hatfield, Landers, and Ray (1984), who extended the prior findings to show that the alpha laterality effect was comprised of right temporal (T4) stability with relative left temporal (T3) alpha increase. They also reported a global "quieting" of the cortex as the time to pull the trigger neared as demonstrated by increased alpha power at temporal and occipital sites.
The interpretation provided by Hatfeld et al. (1984) for these findings was that left hemisphere processes became less important as the trigger pull approached, while right hemisphere processes became relatively more important. The exact processes have yet to be specifed, but Hat field et al. (1984) did include additional tasks designed to selectively engage the marksmens' verbal/analytical abilities or their visual/spatial abilities. They found that while the verbal/analytical tasks led to a relative increase in right hemisphere to left hemisphere alpha (LH activation), the visual/spatial task led to no significant changes in the alpha ratio. The authors interpreted their findings as consistent with the idea that right hemisphere (presumably visual/spatial) processes are critical in successful marksmanship. This general theory has been widely influential in the interpretation of the results of subsequent EEG laterality effects in the sport literature, including the study by Crews et al. (1993) upon which the current study is based.
One of the important differences between the present investigation and that of Crews et al. (1993) is that novice golfers were used instead of experts. Previous investigations that have examined the relationship between an athlete's skill level and the EEG correlates of performance allow us to make predictions about the findings in the present study. One of the general findings from EEG research in this area has been that an increase in alpha activity, commonly seen as skill level increases, is not simply indicative of cortical deactivation, but is indicative of neural reorganization concomitant with the acquisition of more efficient, task-specific cognitive and motor processes (Nunez, 1995; Smith, McEvoy, & Gevins, 1999).
Following this logic, Haufler, Spalding, Santa-Maria, and Hatfield (2000) investigated differences in EEG power between the left and right hemispheres of both novice and expert marksmen. They predicted that since novice shooters should lack task-specific strategies, they should rely more heavily on verbal mediation and effortful processing than the experts in the period prior to firing their rifles. Their prediction that these processing differences between skill groups would manifest in differential EEG laterality was partially born out by their finding that novices showed significantly reduced alpha in the LH, albeit in a restricted range of...
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