EFFECTS OF FEEDBACK CONTROL ON SLOW CORTICAL POTENTIALS AND RANDOM EVENTS

Transcription

1 Hnterberger, Houtkooper, & Kotchoubey EFFECTS OF FEEDBACK CONTROL ON SLOW CORTICAL POTENTIALS AND RANDOM EVENTS Thlo Hnterberger 1, Joop M. Houtkooper 2, & Bors Kotchoubey 1 1 Insttute of Medcal Psychology and Behavoral Neurobology, Unversty of Tübngen 2 Center for Psychobology and Behavoral Medcne, Unversty of Gessen ABSTRACT As known for more than two decades, humans can learn to acheve self-control over ther bran actvty such as the polarty of slow cortcal potental (SCP) shfts referred to as postvty or negatvty. Ths learnng process s supported by the vsual feedback of the SCP n a tme-locked tral structure. On the other hand, t has been repeatedly shown that humans are able to regulate the random dstrbuton of events, produced by an electronc random event generator (REG) as a psychoknetc effect. Ths procedure also entals feedback of the dstrbuton of bnary random events to the subject; however, contrary to the feedback of SCP, there s no known physcal connecton from the subject to REG. In both cases, the to-be-controlled functon should be changed n one of two alternatve drectons ( b-drectonal control ) by use of two dfferent cogntve strateges or states of conscousness. In the present experment the effect of a self-chosen strategy was examned for the regulaton of a feedback sgnal n a pseudorandomzed predefned drecton both on the SCP and the REG. Therefore, the system, called Thought Translaton Devce (TTD) provded feedback of the SCP or the REG. Ths modalty was changed every block of trals of 4.5 to 5s duraton each. The task requrement was assgned pseudorandomly. A correctly produced SCP or REG shft was rewarded wth a smly face. The smultaneous recordng of the Electroencephalogram (EEG) and the REG sgnal allowed nvestgatng psychophysologcal correlates of psychoknetc effects. Ths study focused on the dfferentaton between the two tasks of the REG or SCP sgnal when feedng back one of them. Four subjects performed n total 3500 trals wth SCP feedback and 3500 trals wth feedback of the REG. The average feedback value of all trals was analyzed and tested for beng dfferent from a baselne value taken before the start of the feedback n each tral usng a t-test. The prevous fndngs that human subjects can self-regulate ther SCP wthn the frst sessons were replcated. Hghly sgnfcant SCP control was acheved only by the hghly motvated subjects (S 2+S 3) who attended n more than one day. S 2 attaned a constant hgh correct response rate of 70 to 80 % durng the second and thrd tranng day. It was also shown that a temporary false feedback gven by the REG dd not necessarly dsturb the acquston of SCP self-control. Task-specfc lateralzaton of the SCP (whch was not fed back) was not sgnfcant. The hghly motvated subjects acheved hgher t-values n the REG control than S 1 and S 4. When consderng both feedback modes together, a sgnfcant correlaton between pre-defned task requrement and the devaton from chance expectancy produced by the REG (p=0.02) was produced. Ths can be nterpreted as a psychoknetc effect. The correlaton between task and REG result produced by the system when runnng the same number of trals was far from sgnfcance. Feedback of SCP seemed not to dsturb the postve correlaton between task and REG. Despte these smlartes between the behavor of the REG and the SCPs, the dfferentaton of the REG sgnal dd not sgnfcantly correlate wth SCP ampltudes or SCP lateralzaton. INTRODUCTION Slow cortcal potentals and ther meanng Slow cortcal potentals (SCPs) are potental shfts of the cerebral cortex, whch are settled n the frequency range below 1-2 Hz and can persst over several seconds. The SCPs can be measured usng the electroencephalography (EEG) or by means of the magnetoencephalography (slow cortcal magnetc felds). The ampltudes of the SCP shfts usually vary wthn a range of 10 to 100 µv RMS and reach a maxmum at vertex (electrode poston Cz of the nternatonal 10/20-system). The fact that the SCPs are not very localzed refers to a common actvty of expanded neuronal areas. SCPs emerge as synchronous dscharge of afferent exctaton of the apcal dendrtes of cortcal neurons. These dendrtes are located n the upper The Parapsychologcal Assocaton Conventon

2 Control of slow cortcal potentals and random event generator cortex layer. A negatve potental shft (negatvty) ndcates a lowerng of the exctatory threshold and s related to the moblzaton of resources for behavoral and cogntve tasks. Postve potental shfts (postvty) can be measured durng the executon of cogntve tasks (consumpton of resources) or n cogntvely nactve states (Brbaumer et al. 1990, Rockstroh et al. 1989). Lutzenberger et al. (1982), for example, showed that subjects could solve arthmetc problems faster after producng cortcal negatvty. Lkewse, response tmes were shortened f the task was presented durng cortcal negatvty (Rockstroh et al. 1982). The postvty can also result from postsynaptc exctaton n deeper cortcal layers. Thus frng of the pyramdal cells durng cerebral performance can lead to a postvty on the scalp. To sum, negatvty represents the moblzaton or readness, postvty represents ongong cogntve and neural performance or nhbton of neuronal actvty. The relatonshp between cortcal negatvty and readness s best seen n an S1/S2 paradgm whch produces the so-called contngent negatve varaton (CNV): A warnng stmulus S1 s presented to a subject and followed by an mportant mperatve stmulus S2. Then a cortcal negatvty appears 300 to 500 ms after S1, whch prepares the subject to perform a task after S2 (Walter et al., 1964; Rockstroh et al. 1989, pp. 99). In real lfe the CNV emerges, for nstance,. at a traffc lght when expectng the green lght and preparng for drvng; a postvty can be recorded, however, whle the bran s already busy wth processng of the stmulus. Although humans are usually not aware of these potental shfts, they can learn to change the ampltudes of the SCP voluntarly nto electrcally negatve or postve drecton. Ths can be acheved by feedback of SCP ampltude changes and postve renforcement for changes n the correct drecton (operant condtonng) (Brbaumer et al. 1981; 1984; 1988; 1992). After havng learnt to control the SCPs, humans can also acqure the ablty to conscously perceve them (Kotchoubey et al., 2002). SCP self-control has also been appled to communcaton by means of a drect nterface between bran and computer n completely paralyzed ndvduals (Brbaumer et al., 1999). These authors have developed a Thought Translaton Devce (TTD) n whch self-regulaton of slow cortcal potentals s used to generate a bnary sgnal. Ths sgnal can further be employed to choose letters and words on a computer menu. The TTD has already enabled several completely paralyzed patents dagnosed wth amyotrophc lateral scleross to communcate solely wth ther bran potentals (Perelmouter et al. 1999; Hnterberger et al., 2001). Intenton and random event generators In the last 30 years, studes have been carred out, where the correlatons between pre-stated ntentons and the output dstrbuton of dfferent knds of bnary random event generators (REGs) have been nvestgated. A meta-analyss of these studes yelded a hghly sgnfcant result (Radn & Nelson, 1989). An example of a consstent effort are the studes of Jahn et al. (1997), demonstratng comparable devatons of the mean results from chance expectaton n the order of 10-4 bts per bt processed. Although the absolute effect szes are qute small, these authors showed that the composte effect of a 12-year study exceeded 7 standard devatons, whch suggests a very hgh sgnfcance level. The effect does not depend on the dstance between subject and the REG devce. Even when subjects exerted ther efforts at dfferent tmes from collectng the REG data, the effect szes were smlar. It seems that solely the nformaton about the coherence between an human ntenton and a (classcal) physcally ndependent process s lnkng these together. The effect vanshed when fully determnstc random processes were used, such as the random number generator of a PC, where an algorthm calculates pseudo-randomzed numbers. REGs whch showed anomalous features were usng the thermal nose or quantum nose of electronc components (resstors or dodes) or other physcal random processes whch are determned by mcro-states (e.g. the throwng of dce). Ths approach led to speculatons about the role of conscousness n quantum physcs, specfcally about the possble nfluence of an ntent observer of a random physcal system (Walker, 1979; Houtkooper, 1983; Josephson & Pallkar-Vras, 1991). Although progress towards plausblty has been made (Houtkooper, 2002), a generally accepted explanaton for these effects s lackng. An approach to clarfy the nteractons between ntenton and ts effect on remote physcal processes s to nvestgate the correlatons between the anomalous effects of the REG and the physologcal correlates of 40 Proceedngs of Presented Papers

3 Hnterberger, Houtkooper, & Kotchoubey ntenton. Such a correlate s produced n every physologcal varable whch can be self controlled, because self control s an act of ntenton. Such a varable s the slow cortcal potental shfts whch can be obtaned durng the SCP-self control tranng. For ths reason, the self-control of SCPs has been chosen to be compared wth the ntentonal control of REG output n ths study. TTD and REG: The TTD s a neurophysologcal feedback system that can feed back not only dfferent knds of EEG but any knd of sgnal such as an REG sgnal. The TTD program was modfed to read n the sgnals of the REG and handle t smultaneously wth the EEG sgnal processng. Thus the REG sgnal could be fed back to the subject and ts self-control could be traned, f possble. The ntenton was to collect physologcal varables whch sgnfcantly correlate wth REG control, and thereby to clarfy the ssue of physologcal processes possbly medatng psychoknetc (PK) effects. An advanced applcaton of such physologcal correlates could (reversely) rase the queston of whether t s possble to facltate PK effects by feedng back and tranng those varables. Ths study provdes nformaton concernng the followng questons: 1. Is there a correlaton between the requred ntenton and the result of the REG (the PK effect)? 2. Can ths PK-effect be mproved by the feedback of the REG result? 3. Is there also a sgnfcant PK-effect n case of feedng back the SCP? 4. How does the attempt to control the REG correlate wth the EEG (especally the SCP) of the subject? METHODS Feedback and SCP self control The feedback of slow cortcal potentals s provded n a setup shown n Fgure 1. The EEG-sgnal was conducted by means of Ag/AgCl electrodes placed at the vertex of the head and amplfed n the EEG amplfer that was connected to the TTD va an A/D converter. The mpedances of the electrodes were below 5 kohms. One central electrode (Cz; nternatonal 10/20-system) served as the actve electrode for the feedback. The potental at Cz was referred to the mastods at poston A1 and A2. Snce t has been shown that also lateralzed SCP self control can be learned (Kotchoubey et al., 1996a) the sgnals at the postons C3 and C4,.e. over the left and rght motor cortex were recorded too. The EEG was sampled wth 256 S/s and recorded wth a frequency range from 0.01 Hz to 40 Hz. The low cut-off frequency of 0.01 Hz was mportant snce very slow EEG components were fed back; therefore a tme constant of more than 10 s was requred. To control and correct artfacts caused by vertcal eye movements and blnks, two addtonal electrodes above and below one eye were attached (vertcal electro-oculogram, veog). The feedback-sgnal was calculated on-lne usng the mean of the channels Cz-A1 and Cz-A2 corrected wth the veog. The algorthm for the artfact correcton s descrbed n Kotchoubey et al. (1996b; 1997). Artfacts larger than 1 mv and EEG fluctuatons larger than 200 µv led to the cancellaton of a current tral (nvald data). The SCP feedback-sgnal was generated from low-pass flterng of the artfact-corrected EEG usng a sldng averagng wndow of 500 ms. Thus frequences above 2 Hz were fltered out, leadng to a smooth movement of the feedback cursor whch was updated 16 tmes per second. Ths cursor was symbolzed by a yellow crcle (ball) whose vertcal poston reflected the actual SCP value. Cortcal postvty moved the cursor downwards whereas cortcal negatvty lead to an upward movement. The screen also showed the randomly alternatng task requrements (negatvty versus postvty) by two rectangles ( goals ), dsplayed at the upper or lower edge of the screen. The llumnaton of a goal ndcated the drecton to whch the cursor should be moved. Successes were renforced wth a smley face. The operator was sttng n another room where he could control the experment (for detals see Hnterberger (1999)). The Parapsychologcal Assocaton Conventon

4 Control of slow cortcal potentals and random event generator Fgure 1: Expermental setup: An eght channel EEG-amplfer s connected to a personal computer wth the TTD-software. The random event generator s connected to the seral port. Both data types can be fed back to the subject as the movement of a yellow cursor on a second montor. The requred ntenton s ether to move the ball upwards or downwards. Feedback of random event generator sgnals The REG produced a sequence of bnary numbers. The proporton of ones and zeros was equally dstrbuted and was supposed to be psychoknetcally nfluenced. The bnary-coded data were transmtted nto the PC wth a data transmsson rate of 9600 Baud. Thus approx ones and approx zeros were generated per second and transferred. In the present experment, the dfference between the number of ones and zeros n a certan tme nterval served as the REG sgnal ampltude. Because the TTD was already successfully used as SCP tranng and feedback software, only small modfcatons were necessary to use t for REG feedback. The REG data were read and handled as a separate EEG channel n the software. There was no electronc nterference between the analogue REG sgnal and the EEG sgnal, because the REG data were read n as an already dgtzed sgnal through the seral port whereas the EEG was dgtzed by an A/D-board n the computer. Ths zero correlaton between the two sgnals s of great mportance snce prevous data (Hnterberger, 1999) ndcate that task related dfferences n SCP may be very large, whereas task related dfferences n the REG sgnal, even f sgnfcant, are expected to be very small. Therefore, even a weak correlaton between the two channels mght lead to REG sgnal changes that would be erroneously nterpreted as a PK effect. A dgtal swtchng mechansm nsde the REG guaranteed that possble nfluences of slow waves on the analogue nose of the REG cannot dsturb the dgtal random dstrbuton. To make the feedback of the REG sgnal smlar to the feedback of SCPs, the same paradgm and the same calculaton method was appled to the dfference between ones and zeros as to the EEG. The screen for the feedback sgnal also was kept dentcal. The vertcal ball movement reflected the dfference between ones [1] and zeros [0] wthn the tme nterval of the last 500 ms. To acheve an upward movement more ones than zeros had to be produced, and a downward movement requred more zeros than ones. Each feedback value F (t), calculated from the last t FB =500 ms conssted of 3850 random bts: t (1) F ( t) = ([1] [0]) tn = F tn= t t FB The feedback was also updated each 1/16 s, leadng per tral of 4.5 s duraton to 72 feedback values. These are ndcated wth the tme ndces = Regardless of the sgnal used for feedback (SCP or REG), a data fle was created contanng both sgnals for off-lne analyss. Thus SCP shfts and other EEG components could be nvestgated whle the subject was tryng to control the REG and vce versa. 42 Proceedngs of Presented Papers

5 Hnterberger, Houtkooper, & Kotchoubey The feedback paradgm The feedback tranng of SCP and REG sgnals was conducted n a sequence of ndvdual trals wth no ntertral ntervals. 100 trals consttuted a run after whch a short restng perod was permtted. A tral lasted 4.5 to 5 seconds and conssted of two tme ntervals: 1. a preparatory nterval of 2 s duraton. The subject receved the nformaton about the followng task by llumnaton of the upper or lower rectangle on the screen. At the end of the preparatory nterval, the current sgnal level was set as baselne level, whch corresponded to the vertcal center poston of the ball as startng poston for the followng feedback. Ths nterval was followed by 2. the feedback nterval of a duraton between 2.5 to 3 seconds. Here the subject receved feedback over the SCP or the REG and had to move the ball towards the rectangle that was stll llumnated durng ths nterval, too. The movement of the ball was a lnear functon of the feedback value F. E.g., f the upper goal was lt, the ball should be moved upwards durng the 2.5 to 3 s feedback tme. Ths was acheved by producng cortcal negatvty n the case of SCP feedback or by producng more ones than zeros n the case of REG feedback. The reverse was true for the lower goal. If the average of all ball postons was n the correct half of the screen, the subject receved a postve renforcement by a smlng face ('smley '), whch was presented durng the fnal 500 ms of the tral after the feedback. Expermental desgn The two crtera for selecton of subjects were the ablty to concentrate durng the experment and the belef n parapsychologcal phenomena. Therefore, subjects were selected who had experence n transcendental medtaton (TM) for many years. Four subjects (two female and two male) rangng n age from 40 to 60 years took part at the study. The subjects were seated n a comfortable char n a small solated, electromagnetcally shelded room. Each subject partcpated n the experment on at least one tranng day comprsng 1000 trals. The subjects were nstructed that there were two knds of feedback sgnals (.e. A or B). They were nformed when there was a swtch between sgnals A and B, but they had no knowledge about the nature of these sgnals (.e., that the REG sgnal served as A and the SCP sgnal, as B). Beforehand, they only were nformed that ths was a parapsychologcal experment. Table 1: Each of the four subjects attended the study n one to three days, dependng on hs/her own motvaton. One tranng day comprsed about 1000 feedback trals of ether the REG or the SCP. The modalty was altered twce resultng n three tral blocks per day. tranng day S 1 (m) feedback sgnal, trals S 2 (m) feedback sgnal, trals S 3 (f) feedback sgnal, trals S 4 (f) feedback sgnal, trals REG, 300 trals REG, 300 trals SCP, 300 trals SCP, 300 trals 1 st day SCP, 400 trals SCP, 400 trals REG, 400 trals REG, 300 trals REG, 300 trals REG, 300 trals SCP, 300 trals SCP, 200 trals - SCP, 300 trals REG, 300 trals - 2 nd day - REG, 400 trals SCP, 500 trals - - SCP, 300 trals REG, 300 trals - - REG, 300 trals rd day - SCP, 400 trals REG, 300 trals - - Table 1 llustrates the expermental schedule leadng to almost 7000 trals over all. Wth ths setup the followng questons and nteractons can be explored: 1. Analyss of the task specfc SCP-shfts: a) Can subjects learn to self-control ther SCP? b) Is ths learnng process crtcally dependent on the SCP feedback? The Parapsychologcal Assocaton Conventon

6 Control of slow cortcal potentals and random event generator 2. Analyss of the task specfc REG results: a) Can subjects sgnfcantly nfluence the REG result n the desred drecton? b) If yes, does ths effect depend on REG feedback? Analyss of task specfc SCP shfts: To analyze task specfc SCP-shfts, all trals were averaged n the tme doman, separately for the postvty task and the negatvty task, leadng to two average EEG waveforms for a tral. The ablty to selfcontrol the SCP can be seen n the ampltude dfference between the two tasks durng the feedback nterval. Ths dfference, called SCP dfferentaton (see fgure 3), was calculated as dfference between the mean ampltude durng the second half of the feedback nterval. A t-test was appled to calculate the sgnfcance of ths dfferentaton (see below, Eq. 5). Another measure for the ablty of SCP self-control s the correct response rate. It s the percentage of correctly classfed cursor movement responses. Durng on-lne tranng the classfcaton algorthm calculated a response for each tral as the ntegral of all cursor postons durng the feedback. A correct response was counted when the sgn of ths ntegral matched wth the task requrement (postvty or negatvty). An off-lne classfcaton usng a dscrmnant analyss (Hnterberger, 1999) nstead of a smple ntegral can lead to hgher correct response rates but needs nformaton of prevous runs. However, ths method supples more precse nformaton about the ablty to produce two dfferent sgnals and thus was used off-lne. As there was a strong correlaton between off-lne correct response rate and SCP dfferentaton (r=0.92), the SCP-dfferentaton can be regarded as a satsfyng measure for performance. Analyss of task specfc REG results: As already mentoned, each feedback value F was the dfference between approx ones and 1925 zeros. The standard devaton σ for F can then be estmated for equally dstrbuted values as (2) σ = 2 * [] [ ] The assumpton wth these formulas s that the number of ones s bnomally dstrbuted wth p=1/2. For our analyss the standard devaton was calculated usng the actual REG numbers. The uncertanty σ g, for the mean G over N g trals wth N g =N (1) +N (0) s (3) σ g, = σ 2 N g for G = F. can be estmated by (4) ( F G ( N ) N g 1) + ( N ( F (1) (1) 2 (0) (1) (0) N N ˆ = (1) (0) σ + 1) The means G (1) resp. G (0) of the F (1) resp. F (1) over N (1) resp. N (0) trals were calculated separately for each task. The sgnfcance of REG control was assessed by means of a t-test (Bortz, 1999). (1) (0) G G (5) t =, 1 1 ˆ σ + (1) (0) N N where G (1) and G (0) - the means for the tasks to produce more ones than zeros or more zeros than ones, respectvely; σˆ the correspondng standard devaton; N (1) and N (0) the number of trals of each task, n whch the correspondng σˆ and G were calculated. G (0) ) 2 44 Proceedngs of Presented Papers

7 Hnterberger, Houtkooper, & Kotchoubey RESULTS Analyss of task specfc SCP shfts: Subjects S 1 and S 4 were not very motvated and took part n the frst tranng day only. Wth the SCP feedback, S 1 could acheve an average SCP dfferentaton of 2 µv resultng n a maxmum correct response rate of about 60 %, whch s sgnfcantly better than 50 % expected by chance (t=4.0, N=400, p<0.001). The correct response rate for SCP durng REG feedback dd not dffer from chance. S 4 learned to self-control her SCP wth SCP feedback and attaned 60 and 67 % of correct responses (t= 5.92, p<0.001) n the 1st and 2nd block, respectvely (see Fgure 2). S 2 was hghly motvated and acheved remarkable self-control of SCP. SCP shfts and the correct response rates were hghly sgnfcant (p<0.001) n every block. Also the feedback of the REG sgnal had no negatve nfluence on the SCP self-regulaton. The subject produced SCP dfferentatons of more than 20 µv and acheved 70 to 80 % correct responses except for the frst tranng block, n whch the REG and not the SCP was presented as feedback sgnal. Fgure 3 shows no consderable dfference between the waveforms obtaned durng SCP feedback and REG feedback. In trals wth requred postvty, S 2 produced a negatve potental shft durng the preparatory nterval whch caused a postvty relatve to that negatve baselne level n the feedback nterval. S 3 also attaned sgnfcant control of her SCP-shfts (t=6.1 and 6.7 n the frst and second SCP block; both p<0.001). However, she changed her strategy durng REG feedback leadng to a hghly sgnfcant SCP dfferentaton (all REG blocks: t=-7.1, p<0.001) n the wrong drecton. After repeated REG feedback, wth SCP feedback n the runs 14-16, she could not obtan SCP control any longer (s. Fgure 3). These runs were also contamnated wth eye movement artfacts. 20 Feedback sgnal: REG SCP t S 1 S 2 S 3 S Run No Fgure 2: Sgnfcance (t-values) of the devaton from chance for SCP dfferentaton durng SCP feedback (shaded bars) and REG feedback (flled bars). Blocks of 300 to 500 trals, conducted under equal condtons, were averaged for each of the four subjects separately and analyzed. Postve t-values stand for correct dfferentaton, negatve t-values ndcate dscrmnaton n the wrong drecton (e.g., larger negatve SCP shfts when postve shfts were requred). The Parapsychologcal Assocaton Conventon

8 Control of slow cortcal potentals and random event generator Ampltude [µv] REG feedback task requrement up down 0,0 0,5 1,0 1,5 2,0 2,5 3,0 3,5 4,0 4,5 SCP feedback 0,0 0,5 1,0 1,5 2,0 2,5 3,0 3,5 4,0 4,5 Tme [s] Fgure 3: Averaged (over all trals) SCP waveforms of subject 2, separately for two task requrements, durng REG feedback (top) and SCP feedback (bottom). The shaded area ndcates the baselne perod. Lateralzaton: Although the feedback of left-rght SCP-dfferences was not presented, n some blocks subjects showed sgnfcant lateralzed SCP shfts (see Fgure 4). Mostly, when a downward movement of the cursor (cortcal postvty durng the SCP feedback) was requred, ths postvty was larger over the rght hemsphere as compared wth the left hemsphere durng the feedback nterval. In addton, subject S 2 produced a sgnfcant rght hemsphercal negatvty durng the requred upward cursor movement durng the frst tranng day,. Ths effect vanshed n the followng tranng days. The correlaton between the dfferentaton of the central SCPs and the lateralsed SCPs was not sgnfcant (r=0.15, p=0.22, N=66). 6 4 S 1 S 2 S 3 S 4 Sgnfca nce [t] feedback sgnal REG SC P at C z Run No. Fgure 4: SCP lateralzaton measured at electrode postons C4-C3 durng feedback of SCP and the REG. Postve values ndcate that the left hemsphere s more postve whle the cursor should be moved upwards, whereas negatve values ndcate a left postvty whle the cursor should be moved downwards. Task specfc REG results: Fgure 5 shows the t-values of the devaton of the acheved REG results from chance, whch would be an equal number of ones and zeros. The REG changes were analyzed lke the SCP changes reported above and were taken as the dfference between the currently measured REG sgnal and the baselne level (.e. the mean of the 500 ms before the FB-nterval starts). 46 Proceedngs of Presented Papers

9 Hnterberger, Houtkooper, & Kotchoubey Subject S 1 started wth REG feedback and dd not attan a sgnfcant nfluence on the REG (t=0.62, p=0.27, Ng=1007; one taled t-test). Also S 4 showed no sgnfcant REG results (t=-0.66, p=0.75, Ng=507). In contrast, S 2 acheved a hgh correlaton between task requrement and REG result n the frst block wth REG feedback (t=2.4, p<0.01). The followng block wth SCP feedback yelded a szeable negatve result (t=-2.0, p=0.98). A hghly sgnfcant result (t=3.05, p<0.01) was then attaned n the 6th block wth SCP feedback. Although 7 of 9 blocks yelded postve t-values, S 2's data across all trals dd not reach the.05 sgnfcance level (t=1.48, p=0.07, Ng=2021). We test one-taled n the drecton of ntenton. Other ways of lookng at the data are the REG data wth REG feedback: 9 out of 11 'blocks' score n the postve drecton; the sgn test gves p =.09. The two negatve devatons occur wth the two subjects who acheved less SCP self-control and who were less motvated to contnue. The overall 16 postve out of 20 blocks has a p =.006 accordng to the sgn test (Segel, 1956). Subject S 3 acheved postve t-values n all sx tranng blocks wth an overall sgnfcant result of t=1.72 (p=0.04, Ng=2115). Across subjects, blocks wth REG feedback dd not lead to a sgnfcant result t=1.20, p=0.12) but blocks wth SCP feedback dd (t=1.69, p=0.046). Overall, postve t-values were obtaned n 16 of 20 blocks, resultng n a sgnfcant overall t=2.09 (N=6951, p=0.018). The mean correct response rate dd not dffer sgnfcantly from chance. Ths sgnfcant correlaton between REG feedback sgnal (whch s calculated as the dfference between the REG sgnal durng the feedback nterval referenced to the baselne) and the task requrement could be manly attrbuted to the REG behavor durng the baselne (t baselne (6950)=1.82, p=0.03) whle the REG result durng the feedback nterval dd not sgnfcantly contrbute to ths effect. The dfferentaton of the REG was found to correlate nether wth SCP ampltudes (across runs r=-0.063, p=0.62, N=66), nor wth the SCP lateralzaton (r=-0.044, p=0.73, N=66). To exclude that the system tself produces systematc correlatons between the task (determned by the software random number generator of the PC) and the REG result 7000 trals were collected wthout a subject watchng the feedback. The overall t(7000)=.17 (p=.43) was far from sgnfcance. 3 Feedback sgnal: REG SCP S 1 S 2 S 3 S t Run No. Fgure 5: Sgnfcance (t-values) of the devaton from chance of the REG result whle feedback of SCP (flled bars) and of the REG result (shaded bars) was presented. Blocks of 300 to 500 trals, conducted under equal condtons, were averaged for each of the four subjects separately and analyzed. The Parapsychologcal Assocaton Conventon

10 Control of slow cortcal potentals and random event generator DISCUSSION The ablty of humans to learn to self-control ther SCPs s already well known (Brbaumer, 1984; Rockstroh et al., 1989). Surprsngly, however, three of four subjects partcpatng n the present experment acheved ths self-control already n the frst runs. Moreover, the data of S 2 show that ths acqured ablty s not necessarly dsturbed or mpared when a random sgnal (such as the REG) s presented as the feedback. Ths stablty ndcates that the strategy may be more mportant than the feedback sgnal. Such an nterpretaton s n lne wth the self-control theory of Lacrox (1981) who suggested that durng operant condtonng of bodly functons, subjects frequently (at least on the frst stages of tranng) select a strategy from ther already exstent cogntve-behavoral repertore and keep ths strategy as long as t does not result n a clear falure. In the present data, such strategy (partcularly employed by S 2) was the development of a negatve SCP shft durng the baselne nterval to support subsequent postvty. Durng the baselne, watng for the stmulus ndcatng the onset of the feedback nterval served as a condton n whch a negatvty (.e., the contngent negatve varaton (CNV), see Walter et al., 1964) could easly be produced (see also Bruna, 1993). Ths stablty of self-regulatng strategy can also be a partcular trat of S 2, because n S 3, n contrast, the presentaton of the REG sgnal as feedback dd deterorate the already acqured SCP control. The present data do not allow to specfy factors whch mght determne the outcome of ths conflct. Agan n lne wth the data of the lterature (Radn & Nelson, 1989), a very small but sgnfcant (p<.02) effect of task requrement on the REG result, ndcates that the technque employed n the present study allows to control an electronc REG n the desred way. When reformulatng the hypothess to test for an nteracton between task (whch was connected to a certan cogntve strategy) and REG result n any drecton, the two-taled t-test stll remans sgnfcant (p=.04). Despte the stablty of ths PK effect, there s no generally accepted explanaton for t to date. Tentatvely, however, we mght suggest that such putatve factors as precognton or extra-sensory percepton could not play a role here because the task was not chosen by the subject but generated by the algorthm long before the start of the experment. Factually, a sgnfcant covaraton was found between the task generated by the software random number generator and the REG. However, an explanaton for such a correlaton s hardly thnkable. A non-sgnfcant correlaton between task and the REG feedback sgnal was found when the same number of trals were run wthout a human nteracton. Notably, the sgnfcant nfluence on the REG n the desred drecton was obtaned when SCP feedback was presented, but not when REG feedback was presented. Ths result may appear surprsng but t s, agan, n agreement wth the lterature data demonstratng consderable effects of motvaton and self-confdence on PK effects (Stanford, 1977). Durng SCP tranng, subjects successfully produced the requred shfts of the cortcal potental and were consstently rewarded for ther performance. They were not aware of the prncpal dfference between the two knds of self-control, that s, that n one case there was a physcal connecton between ther bran and the controlled cursor on the screen, and n the other case there was no. Rather, they just knew that they were nvolved n two dfferent, but equally challengng, self-regulaton tasks. They also experenced themselves beng qute successful n one of these tasks. Ths success may have encouraged subjects thereby resultng n a hgher PK effect. Ths motvatonal explanaton remans speculatve at present. In future PK experments usng a larger sample of subjects the motvaton should be drectly controlled by means of a psychologcal nstrument. Several parapsychologcal studes reported, further, that PK effects are the largest at the very begnnng of an experment and then decrease across trals (e.g., Irwn, 1994). Ths appears to hold true for our subjects S 1 and S 2 who started wth REG feedback and attaned good results n those frst runs that they could not repeat n further runs. In contrast, S 3 and S 4 who started wth SCP feedback, acheved better results n SCP runs later n the course of tranng. It appears, furthermore, that whle the PK effect decreased across blocks wth REG feedback, t ncreased n blocks wth SCP feedback, whch s also compatble wth the motvatonal explanaton gven above. 48 Proceedngs of Presented Papers

11 Hnterberger, Houtkooper, & Kotchoubey An alternatve to ths motvatonal explanaton may be, of course, some specfc effect of SCP changes, based on the fact that these changes at the central electrode are related to regulaton of exctablty of large cortcal regons as mentoned n the ntroducton. From the pont of vew of SCP tranng, REG feedback can be referred to as 'false feedback'. Partcularly, the small sze of the PK effect makes the task very frustratng, thus the subjects can resgnate and ther resgnaton can generalze to the easer SCP regulaton task. A better result mght be obtaned wth mxed feedback, whch would contan partly SCP and partly REG trals to support some level of success and to avod frustraton. Alternatng pure SCP wth mxed feedback (announcng t as a more dffcult task) or mxed feedback alone mght therefore be explored. In further studes, the presently used TTD can be extended to a generalzed program to feed back varous physologcal parameters correlated to PK-effects. Thereby self-regulaton of all these parameters can be traned to check ther nfluence on the PK-effect. Such a tranng program mght then enable people to develop ther PK abltes. ACKNOWLEDGEMENTS We thank our assstant Slavca von Hartleb for help n the measurements. We also thank the Insttut für Grenzgebete der Psychologe und Psychohygene, Freburg.Br., Germany for the fnancal support. REFERENCES Brbaumer, N. (1984). Operant control of slow bran potentals: a tool n the nvestgaton of the potental's meanng and ts relaton to attentonal dysfuncton. Pages n T. Elbert, B. Rockstroh, W. Lutzenberger, and N. Brbaumer, eds. Self-Regulaton of the Bran and Behavour. Sprnger-Verlag, Berln. Brbaumer, N., Elbert, T., Rockstroh B. & Lutzenberger, W. (1981). Bofeedback of event-related slow potentals of the bran. Internatonal Journal of Psychology 16, Brbaumer, N., Elbert, T., Canavan, A. G. M. & Rockstroh, B. (1990). Slow potentals of the cerebral cortex and behavor. Physologcal Revews 70, Brbaumer, N., Ghanaym N., Hnterberger, T., Iversen, I., Kotchoubey, B., Kübler, A., Perelmouter, J., Taub, E. & Flor. H. (1999). A spellng devce for the paralysed. Nature 398, Brbaumer, N., Lang, P. J., Elbert, T., Lutzenberger, W. & Rockstroh, B. (1988). Slow bran potentals, magery and hemspherc dfferences. Internatonal Journal of Neuroscence 39. Brbaumer, N., Roberts, L. E., Lutzenberger, W., Rockstroh, B., & Elbert, T. (1992). Area-specfc self-regulaton of slow cortcal potentals on the sagttal mdlne and ts effects on behavor. Electroencephalography and Clncal Neurophysology 84, Bortz, J. (1999). Statstk. Sprnger-Verlag, Berln, p Bruna, C. H. M. (1993). Watng n readness: Gatng n attenton and motor preparaton. Psychophysology 30, Hnterberger, T., Kaser, J., Kübler, A., Neumann, N. & Brbaumer, N. (2001). The Thought Translaton Devce and ts Applcatons to the Completely Paralyzed. In Debner, Druckrey &Webel: Scences of the Interfaces. Gensta- Verlag Tübngen. Hnterberger, T. (1999). Entwcklung und Optmerung enes Gehrn-Computer-Interfaces mt langsamen Hrnpotentalen. Dssertaton n der Fakultät für Physk an der Eberhard-Karls-Unverstät Tübngen, Schwäbsche Verlagsgesellschaft: ISBN Houtkooper, J.M. (1983) Observatonal theory: A research program for paranormal phenomena. Lsse, The Netherlands: Swets & Zetlnger. The Parapsychologcal Assocaton Conventon

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