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Brain DC potentials: Effects of preceding slow potential shifts (pSPSs)
415 the two conditions were also analysed. There was a significant change over the first condition (F(1,44) = 14.46, p < .OOl), with HR decreasing from 88.50 BPM to 83.11 BPM. There were no other significant effects. These results thus indicate some significant effects associated with differences in levels of defensiveness. The data are discussed in terms of their support for the validity of the construct of “repression” as a personality variable modulating the expression of anxiety. Implications for the coaching of elite gymnasts are noted.
electrodes (time constant 6 set, low pass of 70 Hz). PSPSs (within 2 set before 51) were digitized with a 20 msec rate, the recordings after Sl with a 5 msec rate. Selected averages (vEOG corrected) for each channel were computed according to the slow potential shift within 2 set before Sl. The criterion was computed as the difference between the mean of the 2nd second minus the mean of the 1st second before S 1. Thus 3 averages were obtained: one for negative, one for positive and one for no shifts greater than 8 pV in the criterion. (For more detail see Trimmel, in press).
References
Asendorpf J.B. & Scherer K.R. (1983). The discrepant repressor: differentiation between low anxiety, high anxiety, and repression of anxiety by autonomic-facialverbal patterns of behavior. Journal of Personality and Social Psychology, 45, 1334-1346.
Weinberger D.A., Schwartz G.E., & Davidson R.J. (1979). Low-anxious, high-anxious, and repressive coping styles: Psychometric patterns and behavioral and physiological responses to stress. Journal of Abnormal Psychology, 88, 369-380.
BRAIN DC POTENTIALS: EFFECTS OF PRECEDING SLOW POTENTIAL SHIFTS (PSPSs) M. Trimmel, E. Groll-Knapp and M. Haider Department of Experimental Medical Psychology, University of Vienna, Kinderspitalg. 15, A- 1095 Vienna, Austria
Results 3 Sl-related peaks (N115, P236, N382) were dis-
covered. ANOVAs @SPS x electrode site) showed highly significant pSPS-effects for all ERP amplitudes as well as for the early (CNVO), late (CNVE) and terminal (CNVT) CNV. Of the different latency measures, only P236 was influenced by pSPSs. None of the pSPS-effects showed a significant interaction with electrode site. Post hoc comparisons (Tukey-HSD p=.O5 ranges) of amplitudes showed for N115 greater amplitudes after positive pSPSs (positive > no = negative), for N382 also after positive pSPSs (positive > negative = no), and for P236 greater amplitudes after negative pSPSs (negative > no = positive). Latency of P236 was found to be shortest after no pSPSs (224 msec), which was significantly shorter compared to negative pSPSs (245 msec) and also shorter compared to positive pSPSs (238 msec), yet without reaching level of significance. All CNV measures were found to be greater after positive pSPSs compared to negative pSPSs.
introduction
This paper summarizes experimental data conceming the effect of task-preceding DC shifts (preceding slow potential shifts, pSPSs) on CNV (Trimmel, 1987a) and on Sl-related ERPs (Trimmel, in press). Method 9 female and 9 male subjects (Ss) participated a
forewarned reaction time task. Ss performed 100 trials (regular IT1 6 set, IS1 2 sec. stimuli were 20 msec lasting sine waves of 2 kHz with an intensity of 75 dBA) and had to respond after S2 as fast as possible. All recordings (from F4, F3, Cz, P4, and P3 referred to linked mastoids) were done with sintered Ag/AgCl
Discussion
Results showed highly significant pSPS-effects on Sl-related amplitudes of N115, P236, N382 and on all CNV measures, as well as a significant pSPS-effect on latency of P236. The pSPS-effect on CNV measures was interpreted as the reflection of a regulatory process, responsible for an optimal or maybe desired level of activation (Trimmel, 1987a). The pSPS-effect on ERP amplitudes cannot be described by a ‘ceiling/floor effect’ of DC potentials, because ranges showed that negative peaks were enlarged only after positive pSPSs and the positive peak
416 was enlarged after negative pSPSs only. This result would not be explained by a limited capacity of negativity as stated by the ceiling hypothesis (Knott and Irwin, 1968), because for such an effect one would also expect smaller negative peak amplitudes after negative pSPSs compared to no pSPSs. A ‘floor effect’ is not supported either, because in this case one would expect a smaller positive peak amplitude after positive pSPSs compared to no pSPSs, which was not found in the results. The found pSPSs-effect on ERP amplitudes indicates that ERP peak amplitudes are mainly affected by preceding slow potential shifts towards the opposite polarity of the respective peak. This indicates an ‘activation correction mechanism’ which became effective if a cortical area was influenced by any prestimulus slow potential, against an event-related potential. The pSPS-effect on P236 latency and on N382 amplitude may indicate that information processing at this time is prolonged by positive as well as negative pSPSs compared to the no pSPS condition. This could mean that pSPSs themselves may be an expression of particular psychological processes and therefore affect information processing. Another explanation for the fact that P236 latency is shortest after no pSPSs would be given in terms of ‘optimal level of arousal’ (e.g., Luria, 1973). Seen from this point of view, the optimal level of arousal, for information processing at Sl, would be disturbed by negative as well as positive pSPSs and under such conditions information processing would be prolonged, as was found for P236 latency Finally it should be noted that pSPS-effects may reflect higher brain mechanisms. They could therefore be correlated with psychological dimensions, as found for the pSPS-effect on CNV (Trimmel, 1987b). References
Knott, J.R. and Irwin, D.A. (1968). Anxiety, stress and the contingent negative variation (CNV). Electroenceph. Clin. Neurophysiol., 24: 386-387.
Luria, A.R. (1973) The working brain. Penguin Books, Middlesex. Trimmel, M. (1987a). Contingent negative variation (CNV) influenced by preceding slow potential shifts @SPSs). Electroenceph. Clin. Neurophysiol., 66: 7 l74.
Trimmel, M. (1987b). Psychological correlates of CNV operation characteristics (CNV OCs): a pilot study. Arch. Psychol., 139: 241-254. Trimmel, M. (in press). Event-related potentials (ERPs) of the brain influenced by preceding slow potential shifts @SPSs). J. Psychophysiol., 2.
PERCEIVED VISUAL NUMBER DEPENDS ON LOCAL SPATIAL PROPERTIES T. Tuulmets, J. Allik Department of Psychology Tartu State University Tartu, Estonia, USSR The estimated number of dots in a random constellation of dots does not depend only on their actual number but their spatial distribution as well. Several numerosity illusions have been reported so far (e.g. Taves 1941; Ginsburg, 1976; Frith and Frith, 1972) although these illusions are typically communicated by concrete exemplars of patterns rather than abstract distribution types. There are innumerable ways making spatial distribution of dots nonrandom. Loosely speaking, all methods of making order from a chaos can be classified as either global or local. The global methods impose restriction on the whole distribution of dots, specifying. for example, the general shape of their arrangement in space. The local methods, in the opposite, impose restrictions only on the individual dots and their immediate neighbors. In this paper a new striking numerosity illusion is reported which appears to arise from strictly local properties of dot arrangement in space. Method
Two random pattern of dots were presented as stimuli, the observer’s task being indicate which of these two patterns contain more dots. The number of dots, N, in a pattern was a variable (N = 20, 22, ... 32). A given number of dots were randomly positioned on a grid of 48 x 48 possible positions. Three different random pattern types were used, (1) Standard Random (SR) pattern was composed from N dots randomly distributed between available positions independently from each other, (2) Satellite-three (S3) pattern type consists of N dots where each dot had a neighbor
electrodes (time constant 6 set, low pass of 70 Hz). PSPSs (within 2 set before 51) were digitized with a 20 msec rate, the recordings after Sl with a 5 msec rate. Selected averages (vEOG corrected) for each channel were computed according to the slow potential shift within 2 set before Sl. The criterion was computed as the difference between the mean of the 2nd second minus the mean of the 1st second before S 1. Thus 3 averages were obtained: one for negative, one for positive and one for no shifts greater than 8 pV in the criterion. (For more detail see Trimmel, in press).
References
Asendorpf J.B. & Scherer K.R. (1983). The discrepant repressor: differentiation between low anxiety, high anxiety, and repression of anxiety by autonomic-facialverbal patterns of behavior. Journal of Personality and Social Psychology, 45, 1334-1346.
Weinberger D.A., Schwartz G.E., & Davidson R.J. (1979). Low-anxious, high-anxious, and repressive coping styles: Psychometric patterns and behavioral and physiological responses to stress. Journal of Abnormal Psychology, 88, 369-380.
BRAIN DC POTENTIALS: EFFECTS OF PRECEDING SLOW POTENTIAL SHIFTS (PSPSs) M. Trimmel, E. Groll-Knapp and M. Haider Department of Experimental Medical Psychology, University of Vienna, Kinderspitalg. 15, A- 1095 Vienna, Austria
Results 3 Sl-related peaks (N115, P236, N382) were dis-
covered. ANOVAs @SPS x electrode site) showed highly significant pSPS-effects for all ERP amplitudes as well as for the early (CNVO), late (CNVE) and terminal (CNVT) CNV. Of the different latency measures, only P236 was influenced by pSPSs. None of the pSPS-effects showed a significant interaction with electrode site. Post hoc comparisons (Tukey-HSD p=.O5 ranges) of amplitudes showed for N115 greater amplitudes after positive pSPSs (positive > no = negative), for N382 also after positive pSPSs (positive > negative = no), and for P236 greater amplitudes after negative pSPSs (negative > no = positive). Latency of P236 was found to be shortest after no pSPSs (224 msec), which was significantly shorter compared to negative pSPSs (245 msec) and also shorter compared to positive pSPSs (238 msec), yet without reaching level of significance. All CNV measures were found to be greater after positive pSPSs compared to negative pSPSs.
introduction
This paper summarizes experimental data conceming the effect of task-preceding DC shifts (preceding slow potential shifts, pSPSs) on CNV (Trimmel, 1987a) and on Sl-related ERPs (Trimmel, in press). Method 9 female and 9 male subjects (Ss) participated a
forewarned reaction time task. Ss performed 100 trials (regular IT1 6 set, IS1 2 sec. stimuli were 20 msec lasting sine waves of 2 kHz with an intensity of 75 dBA) and had to respond after S2 as fast as possible. All recordings (from F4, F3, Cz, P4, and P3 referred to linked mastoids) were done with sintered Ag/AgCl
Discussion
Results showed highly significant pSPS-effects on Sl-related amplitudes of N115, P236, N382 and on all CNV measures, as well as a significant pSPS-effect on latency of P236. The pSPS-effect on CNV measures was interpreted as the reflection of a regulatory process, responsible for an optimal or maybe desired level of activation (Trimmel, 1987a). The pSPS-effect on ERP amplitudes cannot be described by a ‘ceiling/floor effect’ of DC potentials, because ranges showed that negative peaks were enlarged only after positive pSPSs and the positive peak
416 was enlarged after negative pSPSs only. This result would not be explained by a limited capacity of negativity as stated by the ceiling hypothesis (Knott and Irwin, 1968), because for such an effect one would also expect smaller negative peak amplitudes after negative pSPSs compared to no pSPSs. A ‘floor effect’ is not supported either, because in this case one would expect a smaller positive peak amplitude after positive pSPSs compared to no pSPSs, which was not found in the results. The found pSPSs-effect on ERP amplitudes indicates that ERP peak amplitudes are mainly affected by preceding slow potential shifts towards the opposite polarity of the respective peak. This indicates an ‘activation correction mechanism’ which became effective if a cortical area was influenced by any prestimulus slow potential, against an event-related potential. The pSPS-effect on P236 latency and on N382 amplitude may indicate that information processing at this time is prolonged by positive as well as negative pSPSs compared to the no pSPS condition. This could mean that pSPSs themselves may be an expression of particular psychological processes and therefore affect information processing. Another explanation for the fact that P236 latency is shortest after no pSPSs would be given in terms of ‘optimal level of arousal’ (e.g., Luria, 1973). Seen from this point of view, the optimal level of arousal, for information processing at Sl, would be disturbed by negative as well as positive pSPSs and under such conditions information processing would be prolonged, as was found for P236 latency Finally it should be noted that pSPS-effects may reflect higher brain mechanisms. They could therefore be correlated with psychological dimensions, as found for the pSPS-effect on CNV (Trimmel, 1987b). References
Knott, J.R. and Irwin, D.A. (1968). Anxiety, stress and the contingent negative variation (CNV). Electroenceph. Clin. Neurophysiol., 24: 386-387.
Luria, A.R. (1973) The working brain. Penguin Books, Middlesex. Trimmel, M. (1987a). Contingent negative variation (CNV) influenced by preceding slow potential shifts @SPSs). Electroenceph. Clin. Neurophysiol., 66: 7 l74.
Trimmel, M. (1987b). Psychological correlates of CNV operation characteristics (CNV OCs): a pilot study. Arch. Psychol., 139: 241-254. Trimmel, M. (in press). Event-related potentials (ERPs) of the brain influenced by preceding slow potential shifts @SPSs). J. Psychophysiol., 2.
PERCEIVED VISUAL NUMBER DEPENDS ON LOCAL SPATIAL PROPERTIES T. Tuulmets, J. Allik Department of Psychology Tartu State University Tartu, Estonia, USSR The estimated number of dots in a random constellation of dots does not depend only on their actual number but their spatial distribution as well. Several numerosity illusions have been reported so far (e.g. Taves 1941; Ginsburg, 1976; Frith and Frith, 1972) although these illusions are typically communicated by concrete exemplars of patterns rather than abstract distribution types. There are innumerable ways making spatial distribution of dots nonrandom. Loosely speaking, all methods of making order from a chaos can be classified as either global or local. The global methods impose restriction on the whole distribution of dots, specifying. for example, the general shape of their arrangement in space. The local methods, in the opposite, impose restrictions only on the individual dots and their immediate neighbors. In this paper a new striking numerosity illusion is reported which appears to arise from strictly local properties of dot arrangement in space. Method
Two random pattern of dots were presented as stimuli, the observer’s task being indicate which of these two patterns contain more dots. The number of dots, N, in a pattern was a variable (N = 20, 22, ... 32). A given number of dots were randomly positioned on a grid of 48 x 48 possible positions. Three different random pattern types were used, (1) Standard Random (SR) pattern was composed from N dots randomly distributed between available positions independently from each other, (2) Satellite-three (S3) pattern type consists of N dots where each dot had a neighbor