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625 P300 and stimulus expectancies under decision shift condition
Abstracts
/International
Journal
i Psychobiology, University of Barcelona, Pg. Vall ln, 171, E-08035 Barcelona, Spain; Signals and Processes Laboratory, INSERM-U280; .ive Brain Research Unit, Department of Psychology, ;ity of Helsinki ch Negativity (MMN) is an event-related brain potenw) that reflects a pre-attentive sensory memory mecho detect automatically changes in the acoustic environAMN is generated by bilateral sources in the supratemuditory cortex, reflecting a mismatch process between rsical features of deviant stimuli and a neural sensoryy trace developed by repetitive standard stimuli. In n, it has been reported a right frontal contribution to that might be associated with the involuntary switching ntion following the automatic stimulus-change detec:chanism reflected by the supratemporal component. In .dy, cerebral contributions to MMN were studied in a ;m in which subjects were presented to auditory stimuli rd tones, p = 0.8; deviant tones, which differed from ,ds in frequency, p = 0.1; and natural novel sounds, 1,preceding imperative visual targets (letter or number, ach, in random order) by 300 ms. Subjects were inj to press a response button to visual stimuli and to auditory stimulation. During the task, ERPs were :d from 30 different scalp locations and analysed by :urrent density analysis (SCDa). Results revealed a ntal contribution to MMN, in addition to the well,hed contributions from bilateral sources located in the al and right-frontal cortex. lorted by EU contract BMH4-CT96-0819-COBRN, ;h DGES-UE96-0038, and Catalan CURZAI1200293.
)BJECT RECOGNITION CHANGES IN PATIENTS UNILATERAL BRAIN DAMAGE auskiene, R. Ruseckaite, B. Mickiene as Magnus University, Department of Computer SciKaunas, Lithuania lamage can impair not only elementaly visual functions 3 higher cognitive visual abilities. We examined persons #t and left damagtd temporal lobes of brain and right t hemineglect of visual fields. persons with damaged temporal lobes suffer from holous field disorders which impair reading and visual ltion of the hemifield corresponding to the defect. kis study we compared object recognition performance bersons with right and left damaged temporal lobes of md right and left hemineglect of visual fields. Age of J ranged from 18 to 45 years old. brding to the data of A. Bertulis and A. Bulatov [1994, tion 23, supplement 251 and R. Ruseckaite, G. Raskinis perception 26, supplement 631 we developed a comput-
of Psychophysiology
30 (1998)
95-271
237
erized interactive system in order to test the possibilities of visual perception of various forms of geometrical figures. The person that was being tested has to compare the size of one figure located on one side of the display to the another figure located on the another side of the display. We estimated the accuracy with which subjects judged the height of the figures being equal. Various figures with sizes from 0.2 to 3.0 deg. were generated on monitor. Persons viewed the patterns binocularly at a distance of 1 m and adjusted the size of one figure to make its height equal to another. The error value of perceived linear dimensions were measured as a function of stimulus size. The data obtained evidence that persons with hemineglect of the visual field were unable to concentrate their attention at two figures located on both sides of the monitor and persons with left hemisphere damage showed a more deficiency while those with right hemisphere damage.
625 P300 AND STIMULUS EXPECTANCIES DECISION SHIFT CONDITION
UNDER
Marc E. Lavoie*, Maryse Lassonde Department of Psychology, University of Montreal, C.P. 6128, succ Centre-Ville, Quebec, H3C 357, Canada The effect of stimulus probability on the P300 has been widely demonstrated from earlier studies. Usually, the P300 is elicited when rare stimuli are presented within a sequence of frequent stimuli. This effect is very robust and has been related to the chronometry of the evaluation (latency) and to the subjective probability of the stimulus (amplitude). According to the expectancy hypothesis, the P300 becomes larger in response to rare stimuli because subjects are surprised and tend to revise their expectancies. This effect has been demonstrated in studies in which a stimulus evoked the largest P300 when preceded by four repetitions of the frequent stimuli (XXXXO). It is assumed that the subject expects the previous stimulus to be repeated and then, “0” becomes less expected, evoking a larger P300. In order to further test this hypothesis, the present study analyzes the P300 effect under a modified oddball paradigm (decision switch version) in which the expectancy to a second consecutive rare stimulus was manipulated by dividing the infrequent condition in two equal number of categories (standard infrequent vs. decision switch infrequent). According to the expectancy theory, if subjects put more expectancies to the second rare than to the first, the P300 amplitude should be smaller to the second rare. On the other hand, if the subjects put less expectancies to the second rare than to the first, the P300 should be larger in amplitude to the second rare stimulus. Subjects were 12 paid righthander university students (9 girls - 21 years old). All subjects passed the Raven intelligence test and fall within the superior range limit (95th percentile). None of the subjects had a history of neurological problems nor undergone any pharmacological treatment that could affect measures. The experiments was
238
Abstracts
/International
Journal
physically similar than the classical oddball but-instructions were modified. Subjects had to respond to the frequent and to the first rare in the same manner with the same left hand but they have to switch and answer with the right hand to the successive rare. A total of 280 trials were presented. The odd were 75% (frequent - left), 12.5% (rare - left) and 12.5% (rare - right). The EEG was recorded from 28 tin electrodes mounted in an Electra-cap and all the electrodes were placed according to the guidelines nomenclature by the American EEG Society (1991) at AF3, AF4, F7, F3, Fz, F4, F8, FC3, FC4, T7, C3, Cl Cz, C2, C4, T8, TP7, CP3, CP4, TP8, P7, P3, Pz, P4, P8, 01, Oz and 02. The results revealed that the P3OO amplitude to the second rare (decision shift) was much larger than to the first rare. These data confirm the hypothesis that P3OO.are inversely related to the expectancies of the subject and are more salient when the rare stimuli are less expected.
626 THE INFLUENCE OF REDUCED CORTISOL ‘QN EVENT-RELATED BRAIN POTENTIALS AND PERFOW MANCE DURING MEMORY TASKS
J.R. Lehmann*, J. Edrich, R. Juergens, M. Muenstermann, J. Wegmann University of Ulm, Central Inst. Biome$ Eng. Slow Brain Potential Res. D-89069, Germany
Background: Recent findings from basic and clinical research suggest a higher degree of effectively regulating task-specific arousal in subjects naturally scoring low in cortisol. This study was aimed at clarifying the question wether event-related slow brain potential shifts (SPS), heart rate (HR), mood and task performance are influenced when cortisol levels were reduced artificially by using the Dexamethasone-Suppression-Test (DST) compared with a placebo. Methods: 26 healthy males were instructed to solve 180 memory tasks each on two different days according to a double-blind procedure. DC-EEG recordings were made from 9 positions according to the lo-20 system. In addition, 5 cortisol samples, HR, mood as well as reaction time and accuracy of task solution were assessed during each session. Results: The task-related P3OO elicited by signs which the subjects had to bear in mind as well as the CNV during the anticipation of the target and the CNV preceeding the feedback are larger following the DST. The subjects also reported higher motivation and activation. The HR was found enhanced under dexamethasone, but no major effects on task performance were found. Conclusions: There is no direct effect of the DST on task performance but on the level of arousal of the subjects. Generally speaking, they can better cope with experimental situations, but it cannot be concluded whether these effects were caused by reduced cortisol or enhanced dexamethasone.
of Psychophysiology300
(1998)
95-271
627 INTENDING TO IGNORE IN WAKING AND HYPNOSIS: INFLUENCE OF HYPNOTIZABILITY, SEX, STATE AND HAND USED ON CLASSIC FOREPERIOD REACTION TIME EFFECT
J.E. Horton’*, J. Lamar?, F. Valle-Inclan’, H.J. Crawford’ ‘Department of Psychology, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061, USA, ‘University of La Coruiia, La Corufia, Spain;
Recent research suggests that highly hypnotizable individuals (“highs”) have more efficient attentional processes than low hypnotizable individuals (“lows”). Highs may be able to partition their attention more effectively, ignoring irrelevant stimuli and attending to relevant stimuli. At the behavioral level, highs demonstrate faster reaction times with their dominant hand during complex decision-making tasks (Acosta and Crawford, 1985; Crawford, Kapelis, and Harrison, 1995; Ingram, Saccuzzo, McNeill, and McDonald, 1979; Saccuzzo, Safran, Mderson, and McNeill, 1982). Event-related potential (ERP) data suggest differential processing of to-be ignored stimuli: highs exhibited faster latencies of certain somatosensory (Crawford et al., 1997) and auditory (Crawford, Corby, and Kopell, 1996; Lamas, Crawford and Vendemia, submitted) ERP components. The present study investigated simple reaction times for the left and right hands when the foreperiod duration (time between preceding tone cue and visual stimulus that -must be responded to) is variable from trial to trial, often called the classic foreperiod effect. Under such conditions, simple reaction time tends to be greater for relatively shorter foreperiod durations (MO and George, 1977). Since the preceding tone cues may be considered distracters, we anticipated the foreperiod effect would be lower for highs than lows when asked to actively ignore the cues. Furthermore, we expected highs would demonstrate faster reaction times overall. Participants were 16 lows (8 women) and 16 highs (8 women), strongly right handed with no history of neurological disorders, who had been stringently screened on two standardized hypnotic scales. On separate days they were required to use either the left or right hand (counterbalanced across participants) during counterbalanced waking and hypnosis condition. In each condition they were asked to ignore the tones which were presented either 500, 1000, or 1500 msec prior to the target stimulus (white “ + “s on a black background) for a total of 180 trials. As anticipated, there was a strong foreperiod effect. Overall, reaction times were faster for the right hand in all conditions. There were strong trends involving both hypnotic level and condition. With their right hands, in contrast to lows, highs tended to be faster during waking and slower during hypnosis. With their left hands, there was no difference between lows and highs with the left hand during waking but during hypnosis highs tended to have slower reaction times. These data will be discussed in terms of possible differences in hemispheric organization and speed of information processing among highs and lows.
/International
Journal
i Psychobiology, University of Barcelona, Pg. Vall ln, 171, E-08035 Barcelona, Spain; Signals and Processes Laboratory, INSERM-U280; .ive Brain Research Unit, Department of Psychology, ;ity of Helsinki ch Negativity (MMN) is an event-related brain potenw) that reflects a pre-attentive sensory memory mecho detect automatically changes in the acoustic environAMN is generated by bilateral sources in the supratemuditory cortex, reflecting a mismatch process between rsical features of deviant stimuli and a neural sensoryy trace developed by repetitive standard stimuli. In n, it has been reported a right frontal contribution to that might be associated with the involuntary switching ntion following the automatic stimulus-change detec:chanism reflected by the supratemporal component. In .dy, cerebral contributions to MMN were studied in a ;m in which subjects were presented to auditory stimuli rd tones, p = 0.8; deviant tones, which differed from ,ds in frequency, p = 0.1; and natural novel sounds, 1,preceding imperative visual targets (letter or number, ach, in random order) by 300 ms. Subjects were inj to press a response button to visual stimuli and to auditory stimulation. During the task, ERPs were :d from 30 different scalp locations and analysed by :urrent density analysis (SCDa). Results revealed a ntal contribution to MMN, in addition to the well,hed contributions from bilateral sources located in the al and right-frontal cortex. lorted by EU contract BMH4-CT96-0819-COBRN, ;h DGES-UE96-0038, and Catalan CURZAI1200293.
)BJECT RECOGNITION CHANGES IN PATIENTS UNILATERAL BRAIN DAMAGE auskiene, R. Ruseckaite, B. Mickiene as Magnus University, Department of Computer SciKaunas, Lithuania lamage can impair not only elementaly visual functions 3 higher cognitive visual abilities. We examined persons #t and left damagtd temporal lobes of brain and right t hemineglect of visual fields. persons with damaged temporal lobes suffer from holous field disorders which impair reading and visual ltion of the hemifield corresponding to the defect. kis study we compared object recognition performance bersons with right and left damaged temporal lobes of md right and left hemineglect of visual fields. Age of J ranged from 18 to 45 years old. brding to the data of A. Bertulis and A. Bulatov [1994, tion 23, supplement 251 and R. Ruseckaite, G. Raskinis perception 26, supplement 631 we developed a comput-
of Psychophysiology
30 (1998)
95-271
237
erized interactive system in order to test the possibilities of visual perception of various forms of geometrical figures. The person that was being tested has to compare the size of one figure located on one side of the display to the another figure located on the another side of the display. We estimated the accuracy with which subjects judged the height of the figures being equal. Various figures with sizes from 0.2 to 3.0 deg. were generated on monitor. Persons viewed the patterns binocularly at a distance of 1 m and adjusted the size of one figure to make its height equal to another. The error value of perceived linear dimensions were measured as a function of stimulus size. The data obtained evidence that persons with hemineglect of the visual field were unable to concentrate their attention at two figures located on both sides of the monitor and persons with left hemisphere damage showed a more deficiency while those with right hemisphere damage.
625 P300 AND STIMULUS EXPECTANCIES DECISION SHIFT CONDITION
UNDER
Marc E. Lavoie*, Maryse Lassonde Department of Psychology, University of Montreal, C.P. 6128, succ Centre-Ville, Quebec, H3C 357, Canada The effect of stimulus probability on the P300 has been widely demonstrated from earlier studies. Usually, the P300 is elicited when rare stimuli are presented within a sequence of frequent stimuli. This effect is very robust and has been related to the chronometry of the evaluation (latency) and to the subjective probability of the stimulus (amplitude). According to the expectancy hypothesis, the P300 becomes larger in response to rare stimuli because subjects are surprised and tend to revise their expectancies. This effect has been demonstrated in studies in which a stimulus evoked the largest P300 when preceded by four repetitions of the frequent stimuli (XXXXO). It is assumed that the subject expects the previous stimulus to be repeated and then, “0” becomes less expected, evoking a larger P300. In order to further test this hypothesis, the present study analyzes the P300 effect under a modified oddball paradigm (decision switch version) in which the expectancy to a second consecutive rare stimulus was manipulated by dividing the infrequent condition in two equal number of categories (standard infrequent vs. decision switch infrequent). According to the expectancy theory, if subjects put more expectancies to the second rare than to the first, the P300 amplitude should be smaller to the second rare. On the other hand, if the subjects put less expectancies to the second rare than to the first, the P300 should be larger in amplitude to the second rare stimulus. Subjects were 12 paid righthander university students (9 girls - 21 years old). All subjects passed the Raven intelligence test and fall within the superior range limit (95th percentile). None of the subjects had a history of neurological problems nor undergone any pharmacological treatment that could affect measures. The experiments was
238
Abstracts
/International
Journal
physically similar than the classical oddball but-instructions were modified. Subjects had to respond to the frequent and to the first rare in the same manner with the same left hand but they have to switch and answer with the right hand to the successive rare. A total of 280 trials were presented. The odd were 75% (frequent - left), 12.5% (rare - left) and 12.5% (rare - right). The EEG was recorded from 28 tin electrodes mounted in an Electra-cap and all the electrodes were placed according to the guidelines nomenclature by the American EEG Society (1991) at AF3, AF4, F7, F3, Fz, F4, F8, FC3, FC4, T7, C3, Cl Cz, C2, C4, T8, TP7, CP3, CP4, TP8, P7, P3, Pz, P4, P8, 01, Oz and 02. The results revealed that the P3OO amplitude to the second rare (decision shift) was much larger than to the first rare. These data confirm the hypothesis that P3OO.are inversely related to the expectancies of the subject and are more salient when the rare stimuli are less expected.
626 THE INFLUENCE OF REDUCED CORTISOL ‘QN EVENT-RELATED BRAIN POTENTIALS AND PERFOW MANCE DURING MEMORY TASKS
J.R. Lehmann*, J. Edrich, R. Juergens, M. Muenstermann, J. Wegmann University of Ulm, Central Inst. Biome$ Eng. Slow Brain Potential Res. D-89069, Germany
Background: Recent findings from basic and clinical research suggest a higher degree of effectively regulating task-specific arousal in subjects naturally scoring low in cortisol. This study was aimed at clarifying the question wether event-related slow brain potential shifts (SPS), heart rate (HR), mood and task performance are influenced when cortisol levels were reduced artificially by using the Dexamethasone-Suppression-Test (DST) compared with a placebo. Methods: 26 healthy males were instructed to solve 180 memory tasks each on two different days according to a double-blind procedure. DC-EEG recordings were made from 9 positions according to the lo-20 system. In addition, 5 cortisol samples, HR, mood as well as reaction time and accuracy of task solution were assessed during each session. Results: The task-related P3OO elicited by signs which the subjects had to bear in mind as well as the CNV during the anticipation of the target and the CNV preceeding the feedback are larger following the DST. The subjects also reported higher motivation and activation. The HR was found enhanced under dexamethasone, but no major effects on task performance were found. Conclusions: There is no direct effect of the DST on task performance but on the level of arousal of the subjects. Generally speaking, they can better cope with experimental situations, but it cannot be concluded whether these effects were caused by reduced cortisol or enhanced dexamethasone.
of Psychophysiology300
(1998)
95-271
627 INTENDING TO IGNORE IN WAKING AND HYPNOSIS: INFLUENCE OF HYPNOTIZABILITY, SEX, STATE AND HAND USED ON CLASSIC FOREPERIOD REACTION TIME EFFECT
J.E. Horton’*, J. Lamar?, F. Valle-Inclan’, H.J. Crawford’ ‘Department of Psychology, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061, USA, ‘University of La Coruiia, La Corufia, Spain;
Recent research suggests that highly hypnotizable individuals (“highs”) have more efficient attentional processes than low hypnotizable individuals (“lows”). Highs may be able to partition their attention more effectively, ignoring irrelevant stimuli and attending to relevant stimuli. At the behavioral level, highs demonstrate faster reaction times with their dominant hand during complex decision-making tasks (Acosta and Crawford, 1985; Crawford, Kapelis, and Harrison, 1995; Ingram, Saccuzzo, McNeill, and McDonald, 1979; Saccuzzo, Safran, Mderson, and McNeill, 1982). Event-related potential (ERP) data suggest differential processing of to-be ignored stimuli: highs exhibited faster latencies of certain somatosensory (Crawford et al., 1997) and auditory (Crawford, Corby, and Kopell, 1996; Lamas, Crawford and Vendemia, submitted) ERP components. The present study investigated simple reaction times for the left and right hands when the foreperiod duration (time between preceding tone cue and visual stimulus that -must be responded to) is variable from trial to trial, often called the classic foreperiod effect. Under such conditions, simple reaction time tends to be greater for relatively shorter foreperiod durations (MO and George, 1977). Since the preceding tone cues may be considered distracters, we anticipated the foreperiod effect would be lower for highs than lows when asked to actively ignore the cues. Furthermore, we expected highs would demonstrate faster reaction times overall. Participants were 16 lows (8 women) and 16 highs (8 women), strongly right handed with no history of neurological disorders, who had been stringently screened on two standardized hypnotic scales. On separate days they were required to use either the left or right hand (counterbalanced across participants) during counterbalanced waking and hypnosis condition. In each condition they were asked to ignore the tones which were presented either 500, 1000, or 1500 msec prior to the target stimulus (white “ + “s on a black background) for a total of 180 trials. As anticipated, there was a strong foreperiod effect. Overall, reaction times were faster for the right hand in all conditions. There were strong trends involving both hypnotic level and condition. With their right hands, in contrast to lows, highs tended to be faster during waking and slower during hypnosis. With their left hands, there was no difference between lows and highs with the left hand during waking but during hypnosis highs tended to have slower reaction times. These data will be discussed in terms of possible differences in hemispheric organization and speed of information processing among highs and lows.