Internntmnal
Journal
0 1991 Elsevier
PSYCHO
of Psychophysmlogy,
Science Publishers
11 (1991)
203
203-205
B.V. 0167-8760/91/$03.50
00344
Motor imagination - a model for motor performances? Thomas Instrtuteof
Weiss, Lothar Beyer and Ellen Hansen
Phystology,
Friedrich
Schiller
(Accepted
Kqv words:
Human;
Uniuersrty
4 September
CNS activation;
oJJenu.
D-6900
Jenu (F. R.G.)
1990)
EEG; Training
competition
The effect of training competition (TC) on central nervous activation was investigated in order to examine whether motor imagination could serve as a model for complex motor skills concerning information processing and motor control. EEG was recorded before and immmediately after the TC. The mean alpha frequency (MAF) was computed from the EEG power density spectra. A significant increase of MAF was found after the TC. Similar changes were found during motor imagination. Thus, motor imagination seems to be a good model to examine activation processes.
INTRODUCTION From a physiological point of view, motor performances consist of processes of information and motor control as well as energetic and metabolic processes. The physiological mechanisms and laws of central nervous information processing in connection with motor performances ask for further extensive exploration. However, it is very difficult to find an objective measure which characterizes changes within the central nervous system (CNS) in connection with complex motor skills. Some measurements need a trigger design (EP, ERP, Bereitschaftspotential - BP) and, in this way, a design which is difficult to realize during the performance of real motor skills. Other measurements give a feature for a short time only or/and are only available in situations when the head is not moved (EEG, EP, ERP, DC, BP). Therefore, we have studied physiological parameters in connection with motor imagination (or mental practise)
Correspondence: T. Weiss, Friedrich Schiller University, Department of Medicine. Institute of Physiology, Teichgraben 8, Jena o-6900, F.R.G.
(Beyer et al., 1990) and real motor performance in order to examine whether motor imagination could serve as a model for complex motor skills concerning information processing and motor control.
METHOD 12 elite wrestlers who went in for systematic training performed a training competition twice. A training competition consists of two rounds of real wrestling evaluated by coaches (each round - 3 min independent on the score, 1 min rest between the rounds). The recording conditions as well as the parameters for data conditioning and analysis are detailed elsewhere (Weiss et al., 1989), therefore we restrict ourselves to more general information. EEG was picked up by Ag-AgCl electrodes placed above the occipital and precentral regions of the cortex contralaterally to the preferred hand (all persons were right handed). Recordings were carried out with eyes closed in a separate, noiseshielded room 2 min before and 1 min after the end of the training competition using an adhesive electrode paste (Bentonit, DISA, Denmark). Each
204
I
I
0
lo
2’5
0
25 f(Hz)
10
f (Hz) Fig. 1. Example?,
of power spectres.
recording lasted The EEGs were
Left part: Precentral lead hefore (la) and after (lh) training lead before (2a) and after (2b) training competitmn.
60 s, EEG was analysed off-line
stored on tape. by their power
density spectra (FFT, Nicolet MED-80 computer) (Fig. 1). Similar to the recordings in connection with motor imagination (Beyer et al., 1990) the mean frequency within the alpha-range of EEG (mean alpha frequency (MAF)) was computed by way of the centre of gravity of the classical alpharange (8-13 Hz). This parameter was chosen because the MAF is known to be very stable (Gundel and Hilbrig, 1983). Pre-post differences of MAF were tested by means of the sign-test (Geigy Scientific Tables).
RESULTS The MAF
AND
before
The increase
of MAF
the training
compe-
tition amounted precentrally to 9.94 k 0.59 Hz, occipitally to 10.20 + 0.75 Hz. After the training competition, the precentral MAF was enhanced in
Right part:
Occipital
was interpreted
by the authors as a sign of a higher CNS activation. Thus, the MAF seems to be a good parameter to objectify changes in CNS activation processes which are necessary for optimal effort on motor performances. However, the parameter seems to be suitable only in elite sportsmen. for an untrained population main effects were found in the beta-frequency range of EEG (Nicolov et al., 1988). In relation to an untrained normal population the resting EEG of sportsmen showed a higher alpha index (unpublished data). The higher alpha index as well as different main men might be manifestations (acquired or previously existent) pensate for the everyday training fast relaxation and/ or different
DISCUSSION
measured
competition.
competltion.
effects in sportsof a distinct ability to comrequirements by activation proc-
esses due to physical load. It is interesting that the examined changes MAF during training competition are higher
of for
20 out of the 24 cases (P < 0.01). The mean increase of MAF amounted to 0.53 f 0.39 Hz. Over the occipital region MAF was enhanced in 22 investigations (P < 0.01) the mean increase was 0.49 + 0.25 Hz (Fig. 2). We found a significant increase of the MAF after the training competition. Similar changes were found in connection with bicycle ergometer load (Ascheron and Beyer, 1982), static muscle work (Krause et a1.,1983), and motor imagination (Beyer et al., 1990; Weiss et al., 1989), where the subjects imagined their own movements during
occ 0.49 ZO.25 Hz 92 % Fig. 2: Percentage of increases of the mean alpha frequency (MAF) and mean increase of MAF observed in connection with training competltion precentrally (pc) and occipitally (occ).
205
the precentral area whereas higher increases of MAF during motor imagination were found for the occipital area (Beyer et al., 1990). This is in accordance with different alpha-generators in the central and the posterior regions of the brain (Inouye et al., 1986; Ozaki and Suzuki, 1987) but also with changes in cerebral blood flow (CBF) where the only difference between CBF associated with voluntary finger movement and CBF associated with the imagery of the same movement was the activation of the primary motor cortex (Roland, 1985; Roland et al., 1980). However, the differences between the MAF of the two examined areas are not significant. Further investigations must give evidence whether precentrally measured MAF is a specific parameter of activation of the motor cortex or not. An increase of MAF is also known in connection with changes of the emotional state (Machleidt et al., 1987). It seems to be possible that changes caused by training competition are superimposed by changes of the emotional state of the sportsmen. In our study influences of the emotional state on MAF were not tested. However, the emotional changes produced by Machleidt’s paradigm are very strong. In our investigation such changes were not observed. In general, motor imagination seems to be a good model to examine activation processes because there are a minimum of artefacts and similar changes of MAF in connection with the motor performance (training competition) and motor imagination. Furthermore, in our opinion it seems to be possible that the well known problem of predictability of individual differences in activation processes in a field setting based on laboratory measures (Fahrenberg, 1987; Fahrenberg et al., 1986) could be, at least in part, solved by means of motor imagination.
REFERENCES Ascheron, R. and Beyer, L. (1982) Belastungsabhaengige Veraenderungen des ZNS auf der Grundlage rechnergestuetzter EEG-Analyse. Med. Sport 22: 49-51. Beyer, L., Weiss, T., Hansen, H., Wolf, A. and Seidel. A. (1990) Dynamic of central nervous activation during motor imagination. Inr. J. Psychophysiol. 9: 75-80. Fahrenberg, J. (1987) Theory in Psychophysiology: the multicomponent analysis of psychophysiological reactivity. J. Psychophysiol. 1: 9-12. Fahrenberg, J.. Foerster. F., Schneider, H.-J.. Mueller. W. and Myrtek, M. (1986) Predictability of individual differences in activation processes in a field setting based on laboratory measures. Psychophvsiology 23: 323-333. Gundel. A. and Hilbrig, A.(1983) Circadian acrophasis of powers and frequencies in the waking EEG. Inr. J. Neuroxi. 22: 125-134. Inouye. T., Shinosaki, K.. Yagasaki, A. and Shimizu, A. (1986) Spatial distribution of generators of alpha activity. Elecfroencephnlogr. Clin. Neurophysiol. 63: 353-360. Krause. G., Ullsperger, P., Beyer, L. and Gille. H.G. (1983) Changes in EEG power density spectrum during static muscle work. Eur. J. Appl. Ph_vsiol. 51: 61-66. Machleidt W., Gutjahr L., Muegge A. and Hinrichs H. (1987) Systematisierung affektiver Verlaeufe mit Spektralanalyse, In Weinmann H.-M. (Ed.), Zugung rum Verstoendms hoeherer Hirnfunktionen durch das EEG. ZuckschwerdtVerlag. Miinchen, Bern, Wien, San Francisco, pp. 108-127. Nikolov N.D., Ivanov M.. Aladjev M. and Duridanova V.: Late after-effects in human EEG following hyperventilation in subjects adapted to higher requirements. Prague. IV. Conference Int. Org. Psychophysml. 1988. Ozaki, T. and Suzuki, H. (1987) Transverse relationships of the alpha rhythm on the scalp. Electroencephalogr. C/in. Neurophysml. 66: 191-195. Roland, P.E. (1985) Cortical organization of voluntary behavior in man. Human Neurotml. 4: 115-167. Roland, P.E., Larsen, B., Lassen, N.A. and Skinkoj, E. (1980) Supplementary motor area and other cortical areas in organization of voluntary movements in man. J. Neuro physiol. 43: 118-136. Weiss T., Beyer L., Hansen E., Wolf A. and Haschke W. (1989) Aktivierungsverlauf bei ideomotorischem Training. Z. Ps_ychol. 197: 295-313.
Journal
0 1991 Elsevier
PSYCHO
of Psychophysmlogy,
Science Publishers
11 (1991)
203
203-205
B.V. 0167-8760/91/$03.50
00344
Motor imagination - a model for motor performances? Thomas Instrtuteof
Weiss, Lothar Beyer and Ellen Hansen
Phystology,
Friedrich
Schiller
(Accepted
Kqv words:
Human;
Uniuersrty
4 September
CNS activation;
oJJenu.
D-6900
Jenu (F. R.G.)
1990)
EEG; Training
competition
The effect of training competition (TC) on central nervous activation was investigated in order to examine whether motor imagination could serve as a model for complex motor skills concerning information processing and motor control. EEG was recorded before and immmediately after the TC. The mean alpha frequency (MAF) was computed from the EEG power density spectra. A significant increase of MAF was found after the TC. Similar changes were found during motor imagination. Thus, motor imagination seems to be a good model to examine activation processes.
INTRODUCTION From a physiological point of view, motor performances consist of processes of information and motor control as well as energetic and metabolic processes. The physiological mechanisms and laws of central nervous information processing in connection with motor performances ask for further extensive exploration. However, it is very difficult to find an objective measure which characterizes changes within the central nervous system (CNS) in connection with complex motor skills. Some measurements need a trigger design (EP, ERP, Bereitschaftspotential - BP) and, in this way, a design which is difficult to realize during the performance of real motor skills. Other measurements give a feature for a short time only or/and are only available in situations when the head is not moved (EEG, EP, ERP, DC, BP). Therefore, we have studied physiological parameters in connection with motor imagination (or mental practise)
Correspondence: T. Weiss, Friedrich Schiller University, Department of Medicine. Institute of Physiology, Teichgraben 8, Jena o-6900, F.R.G.
(Beyer et al., 1990) and real motor performance in order to examine whether motor imagination could serve as a model for complex motor skills concerning information processing and motor control.
METHOD 12 elite wrestlers who went in for systematic training performed a training competition twice. A training competition consists of two rounds of real wrestling evaluated by coaches (each round - 3 min independent on the score, 1 min rest between the rounds). The recording conditions as well as the parameters for data conditioning and analysis are detailed elsewhere (Weiss et al., 1989), therefore we restrict ourselves to more general information. EEG was picked up by Ag-AgCl electrodes placed above the occipital and precentral regions of the cortex contralaterally to the preferred hand (all persons were right handed). Recordings were carried out with eyes closed in a separate, noiseshielded room 2 min before and 1 min after the end of the training competition using an adhesive electrode paste (Bentonit, DISA, Denmark). Each
204
I
I
0
lo
2’5
0
25 f(Hz)
10
f (Hz) Fig. 1. Example?,
of power spectres.
recording lasted The EEGs were
Left part: Precentral lead hefore (la) and after (lh) training lead before (2a) and after (2b) training competitmn.
60 s, EEG was analysed off-line
stored on tape. by their power
density spectra (FFT, Nicolet MED-80 computer) (Fig. 1). Similar to the recordings in connection with motor imagination (Beyer et al., 1990) the mean frequency within the alpha-range of EEG (mean alpha frequency (MAF)) was computed by way of the centre of gravity of the classical alpharange (8-13 Hz). This parameter was chosen because the MAF is known to be very stable (Gundel and Hilbrig, 1983). Pre-post differences of MAF were tested by means of the sign-test (Geigy Scientific Tables).
RESULTS The MAF
AND
before
The increase
of MAF
the training
compe-
tition amounted precentrally to 9.94 k 0.59 Hz, occipitally to 10.20 + 0.75 Hz. After the training competition, the precentral MAF was enhanced in
Right part:
Occipital
was interpreted
by the authors as a sign of a higher CNS activation. Thus, the MAF seems to be a good parameter to objectify changes in CNS activation processes which are necessary for optimal effort on motor performances. However, the parameter seems to be suitable only in elite sportsmen. for an untrained population main effects were found in the beta-frequency range of EEG (Nicolov et al., 1988). In relation to an untrained normal population the resting EEG of sportsmen showed a higher alpha index (unpublished data). The higher alpha index as well as different main men might be manifestations (acquired or previously existent) pensate for the everyday training fast relaxation and/ or different
DISCUSSION
measured
competition.
competltion.
effects in sportsof a distinct ability to comrequirements by activation proc-
esses due to physical load. It is interesting that the examined changes MAF during training competition are higher
of for
20 out of the 24 cases (P < 0.01). The mean increase of MAF amounted to 0.53 f 0.39 Hz. Over the occipital region MAF was enhanced in 22 investigations (P < 0.01) the mean increase was 0.49 + 0.25 Hz (Fig. 2). We found a significant increase of the MAF after the training competition. Similar changes were found in connection with bicycle ergometer load (Ascheron and Beyer, 1982), static muscle work (Krause et a1.,1983), and motor imagination (Beyer et al., 1990; Weiss et al., 1989), where the subjects imagined their own movements during
occ 0.49 ZO.25 Hz 92 % Fig. 2: Percentage of increases of the mean alpha frequency (MAF) and mean increase of MAF observed in connection with training competltion precentrally (pc) and occipitally (occ).
205
the precentral area whereas higher increases of MAF during motor imagination were found for the occipital area (Beyer et al., 1990). This is in accordance with different alpha-generators in the central and the posterior regions of the brain (Inouye et al., 1986; Ozaki and Suzuki, 1987) but also with changes in cerebral blood flow (CBF) where the only difference between CBF associated with voluntary finger movement and CBF associated with the imagery of the same movement was the activation of the primary motor cortex (Roland, 1985; Roland et al., 1980). However, the differences between the MAF of the two examined areas are not significant. Further investigations must give evidence whether precentrally measured MAF is a specific parameter of activation of the motor cortex or not. An increase of MAF is also known in connection with changes of the emotional state (Machleidt et al., 1987). It seems to be possible that changes caused by training competition are superimposed by changes of the emotional state of the sportsmen. In our study influences of the emotional state on MAF were not tested. However, the emotional changes produced by Machleidt’s paradigm are very strong. In our investigation such changes were not observed. In general, motor imagination seems to be a good model to examine activation processes because there are a minimum of artefacts and similar changes of MAF in connection with the motor performance (training competition) and motor imagination. Furthermore, in our opinion it seems to be possible that the well known problem of predictability of individual differences in activation processes in a field setting based on laboratory measures (Fahrenberg, 1987; Fahrenberg et al., 1986) could be, at least in part, solved by means of motor imagination.
REFERENCES Ascheron, R. and Beyer, L. (1982) Belastungsabhaengige Veraenderungen des ZNS auf der Grundlage rechnergestuetzter EEG-Analyse. Med. Sport 22: 49-51. Beyer, L., Weiss, T., Hansen, H., Wolf, A. and Seidel. A. (1990) Dynamic of central nervous activation during motor imagination. Inr. J. Psychophysiol. 9: 75-80. Fahrenberg, J. (1987) Theory in Psychophysiology: the multicomponent analysis of psychophysiological reactivity. J. Psychophysiol. 1: 9-12. Fahrenberg, J.. Foerster. F., Schneider, H.-J.. Mueller. W. and Myrtek, M. (1986) Predictability of individual differences in activation processes in a field setting based on laboratory measures. Psychophvsiology 23: 323-333. Gundel. A. and Hilbrig, A.(1983) Circadian acrophasis of powers and frequencies in the waking EEG. Inr. J. Neuroxi. 22: 125-134. Inouye. T., Shinosaki, K.. Yagasaki, A. and Shimizu, A. (1986) Spatial distribution of generators of alpha activity. Elecfroencephnlogr. Clin. Neurophysiol. 63: 353-360. Krause. G., Ullsperger, P., Beyer, L. and Gille. H.G. (1983) Changes in EEG power density spectrum during static muscle work. Eur. J. Appl. Ph_vsiol. 51: 61-66. Machleidt W., Gutjahr L., Muegge A. and Hinrichs H. (1987) Systematisierung affektiver Verlaeufe mit Spektralanalyse, In Weinmann H.-M. (Ed.), Zugung rum Verstoendms hoeherer Hirnfunktionen durch das EEG. ZuckschwerdtVerlag. Miinchen, Bern, Wien, San Francisco, pp. 108-127. Nikolov N.D., Ivanov M.. Aladjev M. and Duridanova V.: Late after-effects in human EEG following hyperventilation in subjects adapted to higher requirements. Prague. IV. Conference Int. Org. Psychophysml. 1988. Ozaki, T. and Suzuki, H. (1987) Transverse relationships of the alpha rhythm on the scalp. Electroencephalogr. C/in. Neurophysml. 66: 191-195. Roland, P.E. (1985) Cortical organization of voluntary behavior in man. Human Neurotml. 4: 115-167. Roland, P.E., Larsen, B., Lassen, N.A. and Skinkoj, E. (1980) Supplementary motor area and other cortical areas in organization of voluntary movements in man. J. Neuro physiol. 43: 118-136. Weiss T., Beyer L., Hansen E., Wolf A. and Haschke W. (1989) Aktivierungsverlauf bei ideomotorischem Training. Z. Ps_ychol. 197: 295-313.
