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Electroencephalography and Sport; Review and Future Directions |
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Quantitative electroencephalography, QEEG , simultaneously measures a large number of electrode sites then the waves are digitized and mathematically analysed. Coloured three dimensional maps of the brain are usually produced to illustrate the specific brain frequencies in the various brain regions. Only one study was located which used QEEG in sport related setting.
Since background EEG contains so many signals which could be related to innumerable events, researches devised a method to determine what part of the EEG signal is a response to a particular event or an evoked response potential (ERP). They do this by repeatedly presenting the same stimulus, such as squeezing a trigger in archery / shooting or initiating a putt in golf, and observing the background EEG for a brief period of time before and after the presentation. With enough repetitions, most of the background EEG potentials will cancel each other out. What remains is a signal that is specifically related to only the stimulus that was used to elicit the response. This signal is generally measured immediately prior to and following the stimulus and the resulting electrical spikes, called positive and negative, are generally named according to the milliseconds that occur before or after the stimulus: for example, P300 is a positive spike 300 milliseconds following the stimulus. This technique can help clarify the athlete's response to a particular display and help identify the various components of the ERP such as readiness to respond, different types of attentional and cognitive focussing. Evoked potentials have the disadvantage of not being able to determine the complexity of the total brain/body involvement in the sport process.
Pre-performance
Background EEG
Early work by Lander's group (Hatfield, Landers & Ray 1984) established that rifle shooters had an increase in temporal alpha activity in the left hemisphere immediately prior to trigger pulls resulting in good scores. They hypothesised that this was indicative of more efficient mental processing and perhaps represented mental quieting through less self talk. This reduction in activation, particularly of the left hemisphere was also noted in later studies of rifle shooters(Bird,1987, Hatfield et al, 1987) archers (Salazar et al, 1990) and golfers (Crews and Landers,1993) and was attributed to the attentional demands being processed in the right hemisphere. The last study also found increased activity in the right hemisphere which they believe is due to both hands being required to execute the motor skill unlike the previous skills.
Contrary to the Lander's group, Collins, Powell and Davies (1990, 1991a, 1991b) demonstrated increased alpha power in the temporal and central locations in both hemispheres prior to successful performance in karate, soccer and cricket tasks performed in the laboratory. Trials deemed failures were associated with decreased alpha activity in both hemispheres. The differences may be due to the demands of the tasks since Landers used predominately skills that were self initiated actions while Collins used skills that required responses to others. The use of the right hemisphere for processing visual-perceptual information has been documented in pilots by Sterman et al (1994) and would explain the increased processing in Collin's work compared to Landers..
Using computer generated tasks designed to elicit spread attention (broad), selective attention (narrow), readiness period and reaction period believed to represent open skill sport attentional situations, Fontani, Voglino and Girolami (1996) report using central EEG electrodes(sites not specified) to assess the differences among females from volleyball, basketball, swimming and a sedentary control group. All groups showed an increase in alpha activity from spread to selective attention with the swimmers showing the lowest alpha throughout all tests and the highest proportion of beta. All groups showed an increase in alpha in the readiness and reaction periods. Volleyball players had the largest frequency band variability across tests and differed from the other groups by having high levels of low frequency during the first second of the readiness period but prevailing beta bands in the last second of the readiness period. The authors (Fontani, et al, 1989) claim that this is a replication of reduction in frequency during the readiness period as measured "on field' for fencers and volleyball players and may represent anticipation of a response. While the authors fail to explain the inconsistencies to be expected for "open' skills versus "closed skills', the study does suggest that one must be aware of the different attentional skills necessary for different sports.
Evoked Response Potentials (ERP)
Rossi and Zani (1990) have reviewed an extensive series of their ERP studies which were used to demonstrate the interface between cognitive and sport psychology. They reported the exogenous, responses that are automatically evoked without conscious processing and believed related to sustained attention, ERP's of fencers, pentathletes and clay pigeon shooters showed a predominance of the right hemisphere. They also noted that the time of day, noise and menstrual cycles of the females affected the speed of processing of information.
In studies of endogenous, responses that represent mental processing, the development of strategies or styles, ERP's of athletes Rossi and Zani (1990) found differences in information processing between specialist in various sport disciplines. They suggested that this demonstrates that the attention styles of athletes are a function of their experience in the sport. For example, younger athletes have less ability to make use of information and have more problems with programming and inhibiting motor responses than older athletes in the same sport. Based upon the amplitude and latency of N2 and P300 they suggest that skeet shooter's EEG excelled at the prediction of information while trap shooter's EEG patterns suggest constant vigilance. Both these patterns of responses are congruent with the requirements and training of their respective sports.
Konttinen and Lyytenen(1992) used the event-related potential method to assess the EEG differences (Fz, C3,C4 & Oz) in experienced rifle shooters prior to the trigger pull. They found a decrease in negativity in successful shots which they explained as being a state of lowered but optimal arousal. In a follow-up study to determine whether the results were due to the actual movement needed to control the rifle or due to the aiming task, they used inexperienced shooters in a variety of holding and aiming tasks. In summary, they found that motor activity necessary for gun stabilization was associated with slow-wave positivity while the aiming task had frontal-central negativity. These results replicate Deecke"s,et al (1984) findings for a laboratory tracking task. They suggest that the balance between movement control and aiming is dependent upon the strategy, skill and experience of the shooter .
During the Event
Only one abstract was located which reported using EEG during competition. (Fontani, Tarricone,Vigni & Zalaffi, 1989) in which they report using EEG telemetry on the prefrontal cortical areas of three female fencers during competition. They report finding that the higher frequency bands were found in the higher skill level athletes.
Sterman's work with pilots in a simulator may provide direction as to the development of valid and reliable tests which nearly duplicate the conditions of the task . One must be cautious about simulations as one can not duplicate the emotions of competition. The perception of the athlete of the importance of the competition is a prime factor in their cognitive and motor responses. Only when the EEG can be easily and reliably used in high level competition will the true nature of brain functioning under the stress of competition be determined.
Prior to Post Event EEG
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Sue is a retired professor of York University, where she taught sport psychology, coaching, and self-regulation courses. Her experience includes Biofeedback and Neurofeedback in a medical center, counseling center, businesses, and in schools. For (more...)
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