Elsevier

Biological Psychology

Volume 58, Issue 3, December 2001, Pages 263-277
Biological Psychology

The role of the left temporal region under the cognitive motor demands of shooting in skilled marksmen

https://doi.org/10.1016/S0301-0511(01)00116-8Get rights and content

Abstract

A number of investigators have reported elevated left temporal alpha power in marksmen during response preparation. This finding has been interpreted to indicate the suppression of irrelevant cognitive processes. However, lower-order motor processes have not been excluded as a possible explanation. Event-related alpha power (11–13 Hz) was examined at sites T3, T4, C3, and C4 in eight skilled marksmen during shooting and two control tasks varying in perceptual-motor complexity. Over an 8-s period preceding the trigger pull, the marksmen exhibited higher power and slope at T3 than at all other sites during shooting compared with the control conditions. No such difference between conditions was detected at C3 and C4. The relative synchrony of left temporal alpha power during shooting, in conjunction with the lack of change at central sites, is inconsistent with the explanation that the effect is accounted for by ‘lower-order’ motor processes exclusively involving the central region.

Introduction

The investigation of physiological response patterns can provide valuable insight into the real-time psychological processes associated with skilled motor performance. Self-paced motor tasks like target shooting have frequently been employed to examine such processes because of a number of methodological advantages over other tasks. Target shooting is an attentionally engaging task characterized by a relatively motionless state that enables psychophysiological recording. A major finding from research on participants of target shooting is that elevated left temporal electroencephalographic (EEG) alpha power is associated with skilled marksmanship. Hatfield et al. (1984) originally observed that broadband alpha power (8–12 Hz) increased over the left temporal region of skilled marksmen during the 7.5 s preceding the shot, while right temporal alpha power remained relatively constant over the same period. In a comparison between expert marksmen and novice shooters, Haufler et al. (2000) observed higher levels of left hemispheric alpha II power (10–11 Hz) during a 6-s period preceding the trigger pull in the experts compared with novices, with the greatest differences occurring in the temporal region. Further evidence of the relevance of left temporal alpha activity to target shooting skill was provided in a longitudinal study of archery students (Landers et al., 1994). The main findings were those of an increase in left, but no change in right, temporal alpha power (10–12 Hz) during the aiming period following 14 weeks of instruction and practice compared with a pre-test assessment. It should be noted, however, that skilled shooters’ best trials are associated with less than maximal levels of alpha power implying a point of optimal activity and the possibility of an inverted-U relationship between alpha power and performance (Hillman et al., 2000, Salazar et al., 1990). In summary, the existing evidence suggests that appropriate synchronization of EEG alpha power over the left temporal region serves a significant and adaptive role in the orchestration of visual-spatial and motor processes during target shooting.

A number of investigators have inferred that heightened left temporal alpha activity is related to the attenuation of covert verbal-analytical behavior (e.g. self-talk) and attentional focus on the perceptual-motor demands of shooting (Hatfield et al., 1984, Haufler et al., 2000, Landers et al., 1994, Lawton et al., 1998). This interpretation is derived primarily from two lines of research. First, cognitive neuroscience studies have provided evidence through ablation and neuroimaging methods that the left temporal region is associated with verbal-analytical processes (i.e. language processing and working memory, see Cohen, 1993). Second, the motor behavior literature suggests a reduction in such covert verbal processes (Fitts and Posner, 1967) and self-evaluative thoughts during highly skilled performances (Jackson, 1996, Ravizza, 1977, Williams and Krane, 1993). This reasoning is consistent with the idea that the verbal-analytical demands of target shooting, and the related verbal processing functions of the left temporal region, are likely to be minimal during skilled shooting in light of the achievement of behavioral automaticity. Several investigators have suggested that a reduction in regional cortical processing during task-specific engagement is related to inhibitory mechanisms (Kinsbourne, 1982, Pfurtscheller, 1992, Pfurtscheller et al., 1996, Smith et al., 1999). Thus, a reduction in verbal-analytical processes, at the neuronal level, may be accounted for by inhibitory mechanisms in the left temporal region. Consideration of the aforementioned studies implies that those cognitive processes that are not essential to the task of shooting are inhibited in skilled performers so as not to conflict with response preparation (Hatfield et al., 1984, Haufler et al., 2000, Landers et al., 1994, Lawton et al., 1998). More specifically, engagement in verbal-analytical processes during actual performance may interfere with, or compete for, the neural resources required to optimally execute the shot. The inhibition of such processes may function to facilitate the achievement of a stable response pattern and thereby decrease the variability of the performance. The hypothesis that covert verbal-analytical processes become inhibited as attention shifts to more task-relevant processes during shooting is hereafter referred to as verbal-suppression.

Although the verbal-suppression account is consistent with observations of elevated left temporal alpha power during skilled shooting (Hatfield et al., 1984, Haufler et al., 2000, Landers et al., 1994, Lawton et al., 1998), this response could also reflect processes associated with the motor demands. For example, the response could be indicative of volume conduction from established primary and/or secondary motor areas or from low-frequency electromyographic activity (or harmonics of high-frequency activity) from the neck or facial muscles associated with the shooting posture. Although few studies have attempted to test such competing explanations, Salazar et al. (1990) did examine whether elevation of left temporal alpha power during target shooting was related to motor processes associated with the muscular demands in a group of highly skilled archers. They found that left temporal alpha power (10–12 Hz) was significantly higher during actual target shooting compared with a control condition in which the archers were required to draw a bow of equal draw weight, but not to aim or shoot. They concluded that the increased alpha power during shooting was related to cognitive as opposed to motor processes. However, the main comparative condition did not entirely exclude the potential influence of motor processes. In this regard, the comparison condition described above required the participants to draw the bow, but did not require arrow release, which requires a relatively small yet distinct motor act. The actual shot execution would seem to require greater motor precision and integrative motor processing compared with the control condition. Additionally, volume conduction from adjacent cortical areas associated with motor control (i.e. somatomotor cortex) may have influenced the recordings at the temporal sites and Salazar et al. did not monitor activity at the central sites to assess the similarity of the EEG recordings. Konttinen and Lyytinen (1993) also investigated motor and aiming component processes in a group of sharpshooters by analyzing preparatory slow potentials (SPs) in frontal, central, and occipital regions. However, because of the site topography examined (Fz, C3, C4, and Oz) and the EEG measure analyzed (SP), their work is limited in terms of furthering our understanding of the functional basis of left temporal alpha synchronization during shooting. In light of these limitations, there is a need to further examine the potential influence of motor processes on left temporal alpha power during skilled shooting.

Observations of elevated left temporal alpha power may be related to (1) ‘lower-order’ motor control (i.e. processes such as those occurring in the primary motor area that are associated with the activation of muscles); (2) verbal-suppression; and/or (3) ‘higher-order’ sensorimotor processes during the preparatory period of shooting in skilled marksmen (i.e. processes that are relevant to the integration of visual, somatosensory, vestibular, and motor aspects; see Mulholland, 1995). In an attempt to reduce the number of possible explanations, the present study sought to determine whether the earlier observed increase in left temporal alpha power is related to lower-order motor control. To address this issue, EEG alpha power during shooting and two control conditions was examined. In the control conditions, the postural and movement demands were similar to those during shooting (i.e., required a trigger pull in one condition) but aiming demands were minimized (see Section 2). Furthermore, several design and methodological improvements were incorporated in an attempt to achieve a more accurate representation of the underlying processes in the left temporal region. First, activity over the somatomotor region (C3, C4) was recorded and the spatial resolution in that area was improved by applying an estimation of the Laplacian operator to supplement Cz-referenced data (Hjorth, 1975). Second, alpha band power was examined with greater specificity by independently examining lower (alpha I, 8–10 Hz) and upper (alpha II, 11–13 Hz) alpha. An increase in alpha I power has been shown to be associated with a generalized, or non-specific, increase in attentional processing during task engagement, whereas alpha II is associated with more task-specific attentional processing (Haufler et al., 2000, Klimesch, 1999, Pfurtscheller and Lopes da Silva, 1999, Smith et al., 1999). Third, the temporal resolution of alpha power estimates was improved to potentially reveal earlier obscured patterns in the time preceding the trigger pull. Finally, because of our specific interest in alpha II power over the left temporal region, absolute values were reported for each site rather than relative asymmetry indices between homologous left and right hemisphere sites. Attempting to segregate the component processes involved in shooting is difficult due to the increased motor precision demands required during actual target shooting relative to the comparative control conditions. However, inclusion of the triggering action in one of the control conditions, in addition to increased temporal and spatial resolution of the EEG measures, may help to provide valuable insight into the processes related to left temporal EEG activity during skilled target shooting.

Two lines of evidence would be needed to support the idea that left temporal alpha activity is related to either verbal-suppression or higher-order sensorimotor processes, and not to lower-order motor control processes. First, alpha II power should be greater in the left temporal region (T3) during the shooting condition relative to the motor control conditions. Second, the pattern of differences in left temporal alpha II power across conditions should be different from that observed in the somatomotor region (C3, C4) in terms of both mean levels and temporal dynamics, particularly when analyzed with increased spatial resolution (see Section 2). Alpha II power was also examined in the right temporal region (T4) but was not expected to differ across conditions. Additionally, because lower alpha power has been shown to be less sensitive to task-specific demands, alpha I power was also examined but not expected to differ between conditions.

Section snippets

Participants

Eight right-handed and right-eye-dominant skilled marksmen volunteered to participate. The age range of the participants was 20–32 year and formal shooting experience ranged from 5 to 12 years. All participants were screened for neurological disorders and were asked not to ingest nicotine or caffeine at least 4 h prior to data collection.

Procedures

Informed consent was obtained from all participants in accord with the institutional review board guidelines. Testing was conducted at a regulation indoor

Alpha II

Fig. 1 is a plot of the means and S.D. of the alpha II power-time curves over the 8-s periods. Table 2 provides the means and standard deviations of alpha I and II power and slope values (for both Cz- and Laplacian-referenced data).

Discussion

The synchronization of EEG alpha in the left temporal region during skilled target shooting has been consistently observed by a number of investigators (Hatfield et al., 1984, Haufler et al., 2000, Landers et al., 1994, Salazar et al., 1990). The general consensus advanced in the literature is that the increased left temporal alpha power during shooting is related to a reduction of covert verbal behavior or self-talk and an increased focus on the perceptual-motor demands of shooting. However,

Conclusions

Synchronized alpha activity over the left temporal region has been associated with marksmanship skill and the time to trigger pull suggesting the importance of the underlying processes during shooting. In other areas of research, the left parietal–temporal–occipital pathway (PTO) has been associated with attention, working memory, visual-associative operations, auditory processing, language, memory consolidation, emotional-motivational processing, feature extraction of spatial details, and the

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Partial support provided by the US Army Research Institute for the Behavioral and Social Sciences via contract MDA903-93-C-0054.

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