The Effects of Intermittent Photic Stimulation upon Respiration Rate and Anxiety

Transcription

1 Western Michigan University ScholarWorks at WMU Master's Theses Graduate College The Effects of Intermittent Photic Stimulation upon Respiration Rate and Anxiety Patricia Moulton Guilford Western Michigan University Follow this and additional works at: Part of the Psychology Commons Recommended Citation Guilford, Patricia Moulton, "The Effects of Intermittent Photic Stimulation upon Respiration Rate and Anxiety" (1985). Master's Theses This Masters Thesis-Open Access is brought to you for free and open access by the Graduate College at ScholarWorks at WMU. It has been accepted for inclusion in Master's Theses by an authorized administrator of ScholarWorks at WMU. For more information, please contact

2 THE EFFECTS OF INTERMITTENT PHOTIC STIMULATION UPON RESPIRATION RATE AND ANXIETY by P a tr i c ia Moulton G uilford A Thesis Submitted to the F aculty of The Graduate College in p a r t i a l fu lfillm e n t of the requirem ents fo r the Degree o f M aster of A rts Departm ent o f Psychology W estern Michigan U niversity Kalamazoo, Michigan A pril 1985

3 THE EFFECTS OF INTERMITTENT PHOTIC STIMULATION UPON RESPIRATION RATE AND ANXIETY P a tr ic ia Moulton G u ilfo rd, M.A. Western Michigan U n iv ersity, 1985 An experim ent was performed to examine the e f f e c ts of th e v is u a l stim ulus p ro p erty of f lic k e r on re s p ira tio n ra te and s ta te -a n x ie ty le v e l. Forty undergraduate co lleg e stu d en t v o lu n teers were randomly assigned to th re e groups which receiv ed in te rm itte n t p h o tic stim u latio n (IPS) and a c o n tro l group which did not receiv e IPS. Each IPS group received the range of f lic k e r freq u en cies, 4 cycles per second to 14 cycles p er second, in a d if f e r e n t p a tte rn. A ll su b je c ts were adm inistered measures fo r tr a it- a n x ie ty and changes in s ta te -a n x ie ty. R esults suggest th a t re s p ira tio n r a te p o s itiv e ly covaries w ith th e frequency o f the in te rm itte n t v is u a l stim ulus w ith in th is range of freq u en cies. exposure to IPS. The le v e l o f s ta te -a n x ie ty was not in creased by A ll su b je c ts showed a decrease in s ta te -a n x ie ty sco res. However, the high tr a it- a n x ie ty (HTA) su b je c ts showed s ig n if ic a n tly le s s v a r ia b ility in th e ir change scores on th e s ta t e - anxiety measure than did th e low tr a it- a n x ie ty (LTA) s u b je c ts.

4 ACKNOWLEDGEMENTS I owe debts of g ra titu d e to many people forem ost to F rederick P. G ault who suggested th is to p ic, provided th e la b o ra to ry space, scu rrie d a l l over Kalamazoo County to procure sp e c ia l equipment, and remained co n stan tly a v a ila b le fo r advice and moral support. To Chris Koronakos, X owe my thanks fo r h is c a re fu l e d itin g and h is s te a d fa s t co n v ictio n th a t my tumid prose could be transform ed in to an organized th e s is. And to my daughter, K irsten G uilford, I owe s p e c ia l thanks f o r "rounding up" th e v o lu n teers. P a tr ic ia Moulton G uilford i i

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9 TABLE OF CONTENTS ACKNOWLEDGEMENTS i i LIST OF TABLES v LIST OF FIGURES v i CHAPTER I. INTRODUCTION The E ffects o f IPS on B rain A c t i v i t y... 3 C lin ic a l R elatio n sh ip s to IPS S e n s itiv ity. 4 The E ffects o f IPS on Autonomic R e s p o n s e s... 7 I I. STATEMENT OF THE PROBLEM I I I. METHOD S ubjects Design Group I : A scending-d escending Sequence Group I I : Descending-Ascending Sequence Group I I I : Random Sequence Group IV: C ontrol Apparatus and Instrum ents R esp iratio n Measures Anxiety Measures Procedure IV. RESULTS The E ffects o f S e ria l P o sitio n i i i

10 CHAPTER The E ffe c ts of F lic k e r Frequency The R elationship Between Dysphoria and T rait-a n x iety V. DISCUSSION APPENDICES A. State-A nxiety Inventory B. T rait-a nxiety Inventory BIBLIOGRAPHY iv R ep ro d u ced with p erm issio n o f th e copyright ow n er. Further reproduction prohibited w ithout p erm issio n.

11 L IS T OF TABLES 1. C o rrelatio n s Between the S e ria l P o sitio n of th e F lic k e r Period and Mean R esp iratio n Rate as Measured by th e Time Occupied by th e F ir s t Five B reathing Cycles in each F lic k e r Period C o rrela tio n s Between the Frequency of IPS and Mean R esp iratio n Rate as Measured by th e Time Occupied by the F ir s t Five B reathing Cycles in Each F lic k e r P eriod A Comparison o f P re- and Post-E xperim ent Scores on th e S tate-a nxiety Inventory The D istrib u tio n of HTA S ubjects and LTA S ubjects fo r th e Three IPS Groups and the C ontrol Group Mean Change-Scores on the S tate-a nxiety Inventory fo r HTA S ubjects and LTA S ubjects in the IPS and C ontrol Conditions v

12 L IS T OF FIGURES 1. R esp iratio n Rate During IPS fo r Group I Ascending-Descending P a tte rn R esp iratio n Rate During IPS fo r Group I I Descending-Ascending P a tte rn R esp iratio n Rate During IPS fo r Group I I I Random Sequence P a tte rn v i

13 CHAPTER I INTRODUCTION The re la tio n s h ip between s tre s s and h e a lth i s an im portant are a of concern today. Of a l l th e various fa c to rs which have been identi f i e d as sources o f s tr e s s, th e workplace has received th e most a tte n tio n. W ithin th is l i t e r a t u r e, some r e la tiv e ly recent suggestio n s p o in t to th e use of the video d isp la y term in al (VDT) as a s ig n ific a n t element c o n trib u tin g to s tr e s s and h e a lth com plaints o f workers. Angina, ch e st pain caused by an inadequate supply o f oxygen to the h e a rt, was observed to occur a t te n times th e normal ra te among o perators who spent more than fo u r hours a t VDTs (Haynes, 1984). Eye, back and neck s tr a i n, headaches, fa tig u e, and tension have also been linked w ith VDT use (Quinn, 1983). Many s itu a tio n a l and s o c ia l fa c to rs asso c ia te d w ith the use of VDTs have been suggested as the causal agents fo r th e s tre s s and h e a lth com plaints: p ressu re to increase p ro d u c tiv ity, close q u a rte rs, l i t t l e human c o n ta c t, deperso n a liz a tio n, and monotony. But the a c tu a l v isu a l stim ulus p ro p e rtie s of the VDT i t s e l f, namely, b rig h tn e ss, g la re, or f lic k e r, have only been looked a t as p o ssib le explanations o f eye s tr a i n and n o t in re la tio n s h ip to any o f the o th e r com plaints. Yet, one of th e se v isu a l stim ulus p ro p e rtie s, f lic k e r, deserves more c a re fu l sc ru tin y because i t has been p rev io u sly linked to fe e lin g s of anxiety and i r r i t a t i o n (B ert & Courjon, 1949; U le tt, G le se r, W inokur, & Law ler, 1953), to 1 R ep ro d u ced with p erm issio n o f th e copyright ow n er. Further reproduction prohibited w ithout p erm issio n.

14 a ffe c tin g som atic responses (D avis, unpublished; Irm is, 1978), and to a lte rin g the e l e c tr i c a l a c tiv ity of the b ra in (Adrian & Matthews, 1934). F lic k e r i s s p e c if ic a lly defined as the in te rm itte n t fla sh e s of lig h t which c h a ra c te riz e th e v is u a l p re se n ta tio n of cathode ray tubes. F lic k e r or in te rm itte n t p h o tic stim u la tio n (IPS) would th e re fo re be p resen t when view ing te le v is io n and playing video arcade games as w ell as when working w ith the video d isp la y term inal of a computer. I f i t i s the case th a t s tr e s s and h e a lth com plaints of VDT u sers may be re la te d to a v is u a l stim ulus c h a r a c te r is tic of cathode ray tu b e s, a c lo se r look i s indeed w arranted n o t only fo r th e h e a lth of these workers but because we, as a n a tio n, a re l i t e r a l l y ad d icted to the use of such screen s. The Bureau of Census (1984) re p o rts th a t 98% of a l l households in America have te le v is io n, and th e average d a ily viewing time fo r each person is 6.8 hours. There are no fig u re s to r e f le c t home video game u se, but th e video arcade in d u stry brought in over 4 b illio n d o lla rs in revenues in The l i f e s t y l e of America is such th a t a m ajor p o rtio n of le is u r e time i s spent in fro n t of a cathode ray tube. I t is not c e rta in how many people are exposed to th is stim ulus in the workplace c u rre n tly. However, a tren d toward in creased use is apparent because th e s a le s of VDTs to business have in creased 400% in th e l a s t two y e a rs. Schools are a lso major buyers of VDTs. Computer b asics are req u ire d courses in many la rg e high sch o o ls, c o lle g e s, and u n iv e rs itie s. C om puter-assisted in s tru c tio n i s also the new fro n tie r in a v a rie ty o f ed u catio n al s e ttin g s : elem entary sc h o o ls, a lte rn a tiv e

15 3 sch o o ls, sp e c ia l ed u cation, stro k e recovery c e n te rs, and v o catio n al re h a b ilita tio n programs. There i s even a tre n d toward VDT use in m ental h ealth c lin ic s and h o s p ita ls. Softw are programs fo r assessm ent and diagnosis are re a d ily a v a ila b le. Among th e well-known instrum ents which can be adm inistered in th is fash io n a re th e Minnesota M ultiphasic Personali t y Inventory (MMPI), th e Beck D epression Inventory (BDI), and the V ocational Preference Inventory (VPI). T elev isio n and video games are g e n era lly a v a ila b le fo r in p a tie n t fre e time use o r can be earned i n token econom ies. What can sa fe ly be sa id i s th a t th e average American i s exposed to the v is u a l stim ulus p ro p e rtie s of a cathode ray tube se v e ra l hours every day e ith e r a t work o r sch o o l, a t home, o r more lik e ly in both p la ces. I f the s tr e s s and h e a lth com plaints of VDT operato rs in the workplace are re la te d to the p h y sical stim ulus p ro p e rtie s of th is exposure, sim ila r e ffe c ts may occur w ith le is u re use but go undetected because o f a tendency to overlook hazards asso c ia te d w ith fun. The E ffe c ts o f IPS on B rain A c tiv ity The v is u a l stim ulus p ro p erty of cathode ray tubes of most in te r e s t i s th a t of in te rm itte n t p h o tic stim u la tio n because of i t s known e ffe c ts upon the b ra in. through e l e c tr i c a l s ig n a ls. The b ra in tran sm its i t s messages By p lacin g ele c tro d e s over various p a rts of th e s k u ll, th ese sig n a ls can be am plified and recorded. The tra c ing which re s u lts is known as an electroencephalogram (EEG). The e l e c tr i c a l a c tiv ity of th e b ra in is very changeable w ith d is tin c t

16 p a tte rn s appearing and disappearing depending upon what th e person is doing. EEG rhythms a re d istin g u ish e d by th e ir frequency and am plitude. The frequency of alpha a c tiv ity, th e EEG rhythm a sso ciated w ith a relaxed but a l e r t s t a t e, v a rie s between 8 and 14 cycles p er second w ith waves o f V. F a ste r a c tiv ity, b e ta waves, is asso c ia te d w ith being e x c ite d ; slow er rhythms, th e ta o r d e lta waves appear in conjunction w ith drow siness o r lig h t sle e p. B right fla sh e s of lig h t are known to a ffe c t th e se p sy sio lo g ic a l p ro cesses. Adrian and Matthews (1934) f i r s t dem onstrated th a t b rig h t flic k e rin g lig h t would modify the EEG alpha rhythm of normal s u b je c ts. This v is u a l stim ulus was able to in c re ase o r decrease th e frequency of alpha a c tiv ity depending upon th e r a te o f stim u la tio n. The term s " d riv in g," " f o l low ing," and "photoentrainm ent" are commonly used to d escrib e th e se EEG responses from th e o c c ip ito - p a r ie ta l reg io n s a t ra te s corresponding to the fla s h frequency. For some in d iv id u a ls, the s e n s itiv ity to b rig h t fla sh e s of lig h t i s so pronounced th a t s e iz u re a c tiv ity can r e s u l t. A ctiv atio n of se iz u re s from viewing te le v is io n has been rep o rte d from a l l over th e w orld (Remond, 1976). More re c e n tly, re p o rts o f "space invader e p ile p sy," e le p tic seiz u re s a c tiv a te d by p layin g video arcade games, re a ffirm the potency o f th e in te rm itte n t v is u a l stim ulus (Rushton, 1981). C lin ic a l R elatio n sh ip s to IPS S e n s itiv ity In te rm itte n t p h o tic stim u la tio n is now a standard procedure in c lin ic a l EEG la b o ra to rie s. V ariatio n s in th e d riv in g phenomenon o r

17 the absence of i t a re d ia g n o stic aid s in a wide v a rie ty of c lin ic a l a p p lic a tio n s. For example, uremic p a tie n ts show unusual s e n s itiv ity to p h o tic d riv in g which can be used to d e te c t changes in c lin ic a l conditions (Hamel, Bourne, Ward, & Teschan, 1978). L ight s e n s itiv ity can be an in d ic a tio n o f neurologic d ise a se such as neuronal lip id o s is (Harden & Pam piglione, 1972) and Jak o b -C reu tzfeld t d isease (Remond, 1976). C ertain sy stem ic, m etabolic, o r e le c tro ly te d iso rd e rs and sed ativ e o r tr a n q u iliz e r drug w ithdraw al c o rre la te w ith th e photo- paroxysmal response (Remond, 1976). W ulff (1960) dem onstrates th a t p a tie n ts experiencing e ith e r b a rb itu ra te or alco h o l w ithdraw al syndromes show extreme s e n s itiv ity to in te rm itte n t p h o tic stim u la tio n. Of s p e c ia l i n t e r e s t is th e re la tio n s h ip between s e n s itiv ity to in te rm itte n t p h o tic stim u la tio n and p sychological d is o rd e rs. The photomyoclonic response (PMR), myoclonic je rk s induced by IPS, occur fiv e to twelve tim es more freq u en tly in su b jects diagnosed as having n e u ro tic d iso rd ers o r psychoses than in norm als. Paroxysmal d is charges are also s ix tim es more lik e ly to be induced by IPS in a population diagnosed as having a n e u ro tic d iso rd e r than in a normal co n tro l group. The n eu ro sis most o fte n im plicated was th a t of hyster i a, now known as conversion d iso rd e r. Conversion d iso rd e rs were once r e la tiv e ly common, but today they c o n s titu te only 5% o f a l l neuroses tre a te d (Coleman, B utcher, & Carson, 1980). This d eclin e in incidence has been a ttr ib u te d to a growing s o p h is tic a tio n about m edical d iso rd e rs. A conversion d iso rd e r is le s s lik e ly among those who no longer b e lie v e i t i s m edically probable th a t a person could be "stru ck " b lin d o r paralyzed. As a r e s u lt, to d a y 's conversion

18 d iso rd ers in c re a sin g ly sim ulate more e x o tic p h y sical d iseases th a t a re h ard er to diagnose. But th e im portant p o in t i s th a t conversion d iso rd e r i s g en erally explained as an attem pt to escape o r avoid the anxiety of a very s tr e s s f u l s itu a tio n. I t could be th e case th a t extreme s tr e s s and an x iety p redispose some in d iv id u a ls to be in c re a s in g ly lig h t s e n s itiv e. The d a ta from U le tt, G leser, Winokur, and Lawler (1953) study fu rth e r supports the co n ten tio n th a t th e way th e b ra in re a c ts to f lic k e r i s r e la te d to th e su sc e p tib le n e ss of the in d iv id u a l to develop anxiety under s tr e s s. EEGs were taken under re s tin g conditio n s and during in te rm itte n t p h o tic stim u la tio n fo r th re e groups who v aried in th e degree to which they experienced severe anxiety. The group in which anxiety was the most severe was composed o f p sy ch iatr i c p a tie n ts judged to have anxiety n eu ro sis or some p sy c h ia tric d iso rd e r in which an x iety was a m ajor fe a tu re. The o th e r two groups were normals c la s s ifie d as anxiety-prone or non-anxiety-prone as determ ined by p s y c h ia tric in te rv ie w and psychological t e s t s. The EEG in d ic a to rs th a t c o rre la te d h ig h ly w ith anxiety c h a ra c te ris tic s were th e p a tte rn o f fundamental p h o tic d riv in g responses and th e amount of su b je c tiv e dysphoria produced by in te rm itte n t p h o tic stim u la tio n. Verbal responses were recorded and ra te d during the f lic k e r p erio d s. There was a s ig n ific a n t c o rre la tio n between anxiety-proneness and the production o f a marked dysphoric se n sa tio n during p h o tic stim u latio n. Sensations rep o rted included sp in n in g, d iz z in e ss, a n x ie ty, and nausea w ith some cases so severe as to produce overt b eh av io ral m anifestatio n s such as angry g e stu re s. A p h y sio lo g ical co n d itio n re la te d to

19 th e fe e lin g s ta te v e rb a lly la b eled as anxiety may in c re ase lig h t s e n s itiv ity. Exposure to fla sh in g lig h ts may exaggerate th is conditio n. A sim ila r re la tio n s h ip between anxiety-proneness and EEG alpha a c tiv ity may also e x ist f o r auditory s tim u li. Nowak and Marczynski (1981) reported th a t high t r a i t anxiety su b je c ts as measured by the T aylor M anifest Anxiety S cale re a c t more stro n g ly to sounds on th e ir EEG p a tte rn s of alpha a c tiv ity than do low t r a i t anxiety su b je c ts. In o th e r words, th e p sy chological s ta te of an x ie ty may c re a te a physio lo g ic a l co n d itio n in which environm ental s tim u li can exacerbate th e p sychological s ta t e through purely p hysical means. In th e case o f the VDT u s e rs, s tr e s s may be induced in p a rt by th e c h a ra c te ris tic s of th e w orkplace, b u t i t may also be a r e s u lt o f in creased anxiety produced by in te rm itte n t v is u a l stim u la tio n over long periods of tim e. I f the above form ulations are tru e, we would expect to see o perators w ith high t r a i t anxiety to be a ffe c te d more q uickly and more adversely by t h i s exposure to IPS than non-anxiety- prone u sers. The E ffe c ts o f IPS on Autonomic Responses R elated to th is in trig u in g problem from what appears to be an e n tir e ly d iffe re n t p ersp ectiv e i s the potency o f the in te rm itte n t v is u a l stim ulus to a ffe c t o th er p h y sio lo g ical resp o n ses. While the in flu en ce o f p h o tic stim u la tio n on EEG a c tiv ity has been w ell documented, th e p o ssib le in flu en ce of such stim u la tio n on other physio lo g ic a l responses has receiv ed l i t t l e co n sid eratio n by laborato ry s c ie n t is ts. One e a rly stu d y (D avis, unpublished) described th e e f f e c t

20 o f such a stim ulus upon both autonomic and electroencephalographic a c tiv ity of a normal p o p u latio n. When exposed to IPS in a range of frequencies approxim ately eq u iv alen t to th a t of th e normal alpha range, a p e rfe c t p o s itiv e c o rre la tio n was observed between stim ulus frequency and re s p ira tio n r a te. H eart r a te also covaried p o s itiv e ly, whereas electrocardiogram and volume pulse measures were n eg ativ ely c o rre la te d. R esp iratio n am plitude showed no re la tio n s h ip to changes in the frequency of lig h t fla s h e s. Irm is (1978) a ls o rep o rted a p o s itiv e c o rre la tio n between fla s h frequency and h e a rt r a te in health y in d iv id u a ls. What i s being suggested by th e se fin d in g s is th a t the h e a lth com plaints o f the VDT u sers may b e a function o f the f lic k e r c h a r a c te r is tic of cathode ray tu b e s. If r e s p ira tio n r a t e is in creased by f a s t fla s h frequencies w hile th ere a r e no corresponding adjustm ents in re s p ira tio n am plitude, a ty p e of h y p e rv e n tila tio n may be occurring. In the Haynes (1984) study o f VDT u se rs angina was rep o rted to occur a t te n tim es the normal ra te. However, angina whose ch ie f symptom i s acute pain i n the chest occurs more freq u en tly in men than in women and in o ld e r th an in younger persons. The su b je c ts in th e Haynes (1984) stu d y were a l l fem ale. Secondly, the symptoms of h y p e rv e n tila tio n which a t th e o u tse t inclu d e a tig h tn e s s of th e ch est, a sen satio n of sm othering, and some degree of apprehension are f r e quently m isdiagnosed as o th e r conditions (Pincus & Tucker, 1978). And l a s t ly, o th e r symptoms of the h y p e rv e n tila tio n syndrome include headache, in a b ility to c o n c e n tra te, v is u a l d istu rb a n c e s, and fa tig u e. All o f these symptoms were also re p o rte d for th e VDT u se rs. The p h y sio lo g ical b asis fo r suggesting that v is u a l input may

21 in flu en ce th e re s p ira to ry system i s through neuronal a sso c ia tio n s in the b ra in stem. The m ajo rity o f a ffe re n t v is u a l fib e rs p ro je c t from the eye to the l a t e r a l g e n ic u la te nucleus of th e thalamus where they synapse w ith fib e rs p ro je c tin g to the o c c ip ita l lo b e, th e v is u a l cente r o f the co rte x. However, some v is u a l fib e rs p ro je c t d ir e c tly to the su p e rio r c o llic u lu s. The su p e rio r c o llic u lu s also re c e iv e s extensive p ro je c tio n s from th e v is u a l co rte x. turn p ro je c ts to th e r e tic u la r form ation. The su p e rio r c o llic u lu s in A fla s h of lig h t could a c tiv a te c e lls in th e r e tic u la r form ation v ia a descending in flu en ce from th e su p erio r c o llic u lu s (Naufa & F e irta g, 1979). The neurons which co n tro l re s p ira to ry a c tiv ity are also lo c a te d in the b ra in stem. Experiments suggest the e x iste n c e of sep arate in s p ira to ry and expiratory cen ters in th e v e n tra l r e tic u la r form ation, but th e re are no m orphologically id e n tif ia b le n u c le i corresponding to th ese areas (S elk u rt, 1971). The r e tic u la r form ation is composed of m ultim odal, nonspecific neurons whose d e n d rite s spread over sev e ra l m illim eters and th u s receive neuronal sig n a ls from many so u rces. This s tru c tu re in te g ra te s inform ation from innum erable s ite s fo r both a ffe re n t and e ffe re n t messages. Thus a fla s h of lig h t could in flu en ce th e mechanisms resp o n sib le fo r th e g eneration o f the re s p ira to ry rhythm which lie w ith in the b ra in stem.

22 CHAPTER I I STATEMENT OF THE PROBLEM The ra tio n a le fo r th is experim ent was to examine the e ffe c ts of the v is u a l stim ulus p ro p erty o f f lic k e r of cathode ray tubes ap art from th e ir o th e r p h y sic a l stim ulus c h a ra c te ris tic s and from th e environmental circum stances asso c ia te d w ith th e use o f VDTs, video games or te le v is io n. I t was hypothesized th a t r e s p ir a tio n ra te w ill covary stro n g ly w ith the frequency o f p h o tic stim u la tio n. And, increased re s p ira tio n ra te o r h y p e rv e n tila tio n may, in p a r t, explain some of the h e a lth com plaints a sso c ia te d w ith VDT use in th e workplace. Secondly, i t was hypothesized th a t exposure to f lic k e r, in te rm itte n t p h o tic s tim u la tio n, w ill in c re a se anxiety le v e ls. This re la tio n s h ip has never been measured o b je c tiv e ly fo r a normal population exposed to IPS. However, th e l i t e r a t u r e would suggest th a t increased anxiety measures may be a n tic ip a te d fo r only those in d iv id u a ls who are anxiety-prone. The experim ental sessio n s were b r i e f, being only 30 m inutes lo n g, as compared w ith th e average exposure time to a VDT a t work o r to th e average d a ily te le v is io n viewing tim e. The in te n tio n was to dem onstrate th a t th e experim ental v a ria b le, f lic k e r, has an immediate e ffe c t upon re s p ira tio n ra te and an x iety le v e ls. 10

23 CHAPTER I I I METHOD Subjects Forty undergraduate v o lu n te e rs, 18 to 38 years o f age (mean age 20), were se le c te d on th e b a sis o f absence o f e p ile p sy, fam ily h is to ry of e p ile p sy, b ra in damage, or cu rren t use of drugs. There were 20 men and 20 women. Design S ubjects were randomly assigned by sex to one o f four groups: th re e groups which were exposed to IPS and one group which was n o t. The th ree IPS groups were used to look a t th e re la tio n s h ip between f lic k e r frequency and r e s p ir a tio n ra te. The fo u rth group which received no in te rm itte n t photic stim u la tio n served only as a c o n tro l fo r th e an x iety m easures. The th re e IPS groups were exposed tw ice to fla s h frequencies o f 4, 6, 8, 10, 12, and 14 cycles per second. This range of frequen cies roughly approxim ates th e alpha range. A ll IPS periods and in te rv a ls between IPS periods were one minute in d u ratio n. The three IPS groups d iffe re d o n ly in th e o rd er in which th e d iffe re n t f lic k e r frequencies were p resen ted. The Davis (unpublished) paradign attem pted to is o la te th e e ffe c ts of the s e r i a l p o s itio n of th e v is u a l stim ulus by combining d a ta from two groups, one whose order of 11

24 p resen tin g f lic k e r frequencies follow ed an ascending-descending p a t te r n and one whose o rd e r of p re sen tin g f lic k e r freq u en cies followed a descending-ascending p a tte rn. This experiment follow ed the Davis paradigm w ith the a d d itio n of a th ir d group whose o rd er o f presen tin g f lic k e r freq u en cies was randomly determ ined. By combining data from th re e d iffe re n t p a tte rn s of f lic k e r p re s e n ta tio n, e f f e c ts due to the s e r i a l p o s itio n of the f lic k e r p erio d independent o f the frequency or e ffe c ts due to the f lic k e r frequency independent o f s e r ia l p o sitio n could be determ ined. I t was hypothesized th e re would be strong e ffe c ts on re s p ira tio n r a te due to th e frequency o f the photic stim u la tio n b u t no e ffe c ts due to th e s e r ia l p o sitio n o f the flic k e r p erio d. Group I : A scending-d escending Sequence Subjects in th is IPS conditio n received the range o f f lic k e r frequencies in an ascending-descending o rd er. That i s, in te rm itte n t p h o tic stim u la tio n began with one minute of th e low est frequency (4 cy cles per second) and proceeded w ith one m inute in te r v a ls up to the h ig h e st frequency (14 cycles p e r second) and then by ste p s back again to th e low est frequency. T herefore, each f lic k e r frequency was presented tw ice fo r one minute p erio d s. Group I I : D escendirg-a s cending Sequence Subjects in th is IPS conditio n received the range o f f lic k e r frequencies in a descending-ascending order. IPS began w ith one m inute of th e h ig h e st freq u en cy (14 cycles p e r second) and proceeded

25 w ith one m inute in te r v a ls to th e low est frequency (4 cycles p e r second) and then by ste p s back again to th e h ig h e st frequency. Each f lic k e r frequency was presen ted tw ice f o r one minute p erio d s. Group I I I : Random Sequence S ubjects in th is IPS co n d itio n received two f lic k e r periods of 4, 6, 8, 10, 12, and 14 cy cles p e r second i n a random o rd e r. The ord er determ ined by random s e le c tio n was 6, 8, 12, 4, 4, 10, 14, 6, 10, 8, 12, 14. This sequence was used fo r a l l su b je c ts in th is group. Group IV; C ontrol Subjects in th is conditio n received no in te rm itte n t v is u a l stim u la tio n. This group served as a c o n tro l group fo r the an x iety measures. Apparatus and Instrum ents The experim ent was conducted in a clo sed, a ir-c o n d itio n e d labo rato ry room f i t t e d w ith a one-way m irro r. The su b je c ts sa t i n a c h a ir facing the m irro r which was blackened out except fo r th e area of th e bulb fo r the p h o tic stim u la to r. Poor lig h tin g was absent during the IPS sessio n s to prevent v is u a l d is tr a c tio n s. This conditio n does n o t p a r a lle l th a t of th e ty p ic a l VDT u s e r 's w orkplace of a w ell lig h te d open room. However, ambient lig h tin g has been shown to have no e ffe c t on s e n s itiv ity to in te rm itte n t p h o tic stim u latio n (Van Egmond, B innie, & V eldhuizen, 1980). The a ir-c o n d itio n in g u n it

26 14 provided a mask fo r extraneous au d ito ry s tim u li. P hotic s tim u la tio n was performed w ith a Grass PS-2 p h o tic stim u la to r a t a d ista n c e of approxim ately 1 m eter from th e nasion and an in te n s ity o f 100 n it.s e c / f la s h. The su b jects were in s tru c te d to remain seated w ith th e ir eyes clo sed. IPS experim ents are ty p ic a lly c a rrie d out under both eyes open and eyes closed co n d itio n s. The v is u a l stim ulus does not lo se i t s potency under the eyes closed conditio n, on th e co n trary th e a c tiv a tin g e ffe c t i s somewhat increased (Van Egmond e t a l., 1980). The eyes closed co ndition was used to reduce the anxiety of th e experim ental s itu a tio n i t s e l f ; su b jects were w orried about eye damage from a b rig h t lig h t but were re le iv e d when to ld they were to keep th e ir eyes closed. Since i t was hypothesized th a t exposure to p h o tic f lic k e r w ill in c re ase an x iety le v e ls, i t was im portant to elim in ate o th e r known anxiety-producing varia b le s. The su b je c ts were in s tru c te d to avoid head or eye movements. No re s tra in in g devices were used as th ese might c o n trib u te to fe e lin g s of an x iety. Compliance by each su b je c t in term s of head and eye movement could be observed by th e experim enter through the one-way m irro r area l e f t open f o r the b u lb. R esp iratio n r a te was recorded through a d ire c t coupled Grass Model 7P1 p re a m p lifie r having an in p u t of 1.5 megohms a t PGR p o s itio n v ia a Fenwall E le c tro n ic s th e rm isto r w ith a re s is ta n c e o f 50,000 to 150,000 ohms a t 25 C. The th e rm isto r was secured under the rig h t n o s tr il of th e su b je c t by s tr ip s o f hypoallerg en ic m edical tape. Wires from th e th e rm isto r were connected to a term inal board which led

27 to th e p ream p lifier in the room on th e o th e r s id e o f the one-way m irro r. R esp iratio n Measures Two measures of re s p ira tio n were taken fo r each su b je c t during each f lic k e r p e rio d, one a t the beginning of each stim ulus period and one a t the end. Davis (unpublished) showed th e time o f maximum e ffe c t on re s p ira tio n r a te to be in the e a rly p a r t of th e stim ulus periods as compared w ith th e la te r p a r t. In o th e r words, a g re a te r e ffe c t on breath in g was observed in the polygraph tra c in g each time the p h o tic stim u la to r is turned on as compared to the responses which are recorded a f te r th e lig h t flash es have occurred for 20 seconds or more. The f i r s t measure involved recording the tim e occupied in seconds by the f i r s t fiv e com plete b reath in g cy cles in each f lic k e r p erio d. Since th e re were 12 periods of IPS exposure fo r each su b je c t, th ere were 12 estim ates of r e s p ira tio n r a te : two estim ates fo r each of th e s ix d iffe re n t freq u en cies o f p h o tic stim u la tio n. However, the p h y sio lo g ic a l responses recorded during the onset of a stim ulus period may be confounded by the o rie n tin g response. The o rie n tin g response is known to decrease the frequency of re s p ira tio n. T herefore, a second measure o f re s p ira tio n ra te was taken in each f lic k e r period to re p re se n t th e end of the stim ulus p erio d. The second measure was taken by counting the number o f breath in g cycles during th e la s t 30 seconds o f each f lic k e r p erio d. Again, since th ere were 12 perio d s of IPS exposure fo r each s u b je c t, th e re were 12 estim ates of re s p ira tio n r a te rep resen tin g the l a t e r p a rt of the

28 stim ulus p erio d s. There were two estim ates f o r each of the s ix d i f fe re n t frequencies of p h o tic stim u la tio n fo r each su b je c t. Therefo re, 24 se p a ra te re p re sen ta tio n s of r e s p ir a tio n r a te were c o lle c te d fo r each o f the 30 p a rtic ip a n ts exposed to in te rm itte n t p h o tic stim u la tio n : 12 which re p re sen te d the onset o f each o f th e f lic k e r p erio d s and 12 which rep resen ted the l a t e r p a r t of each of th e f lic k e r p erio d s. A nxiety Measures Anxiety was measured by th e S ta te -T ra it Anxiety Inventory (STAI) adm inistered tinder th e t i t l e "S elf-e v alu atio n Q uestionnaire" (S p ie lb e rg e r, Gorsuch, & Lushene, 1968). This instrum ent co n tain s two s e lf - r e p o r t s c a le s, th e State-A nxiety Inventory and th e T r a it- A nxiety Inventory. Each scale i s composed of 20 s h o rt questions having four p o ssib le responses o f d iffe re n t w eights. The S ta te - Anxiety Inventory p ro v id es an o p e ra tio n a l measure of th e anxiety f e l t by an in d iv id u a l a t a p a rtic u la r moment in tim e. S ta te anxiety i s thought o f as a tr a n s ito r y em otional co n d itio n c h a ra c te riz e d by fe e lin g s o f tensio n and apprehension which vary in in te n s ity and flu c tu a te over tim e. S ince i t was hypothesized th a t exposure to phot i c f lic k e r w ill in c re a se an x iety, the S tate-a nxiety Inventory was adm inistered p re- and p o st-ex p erim en tally fo r a l l groups. This instrum ent was chosen because exten siv e norm ative d a ta are a v a ila b le fo r undergraduate c o lle g e stu d e n ts, the read in g a b i lity le v e l required i s 6 th -g rad e, i t has been shown to be s e n s itiv e enough to d e te c t changes in anxiety le v e l asso c ia te d w ith p a r tic ip a tio n in experim ents,

29 n and i t has been shown to c o rre la te h ig h ly w ith another well-known anxiety measure, th e Taylor M anifest Anxiety S cale. The T rait-a nxiety Inventory measures a r e la tiv e ly s ta b le behavio r a l d is p o s itio n. T ra it anxiety o r anxiety-proneness re fe rs to d iffere n ces between people in th e ir tendency to respond to s itu a tio n s o f s tr e s s w ith e le v a tio n s in s ta te an x iety. Scores on the T ra it- Anxiety Inventory over 40 a re considered H igh-t rait A nxiety. The c h a ra c te ris tic s of H ig h -T rait Anxiety (HTA) v ersu s Low-Trait Anxiety (LTA) was not an experim ental v a ria b le in th is design. Such a th re a t to v a lid ity was th e o re tic a lly c o n tro lle d by th e method o f random assignm ent. However, th e T rait-a nxiety Inventory was adm inistered to a l l su b je c ts to id e n tify any anxiety-prone su b je c ts in th e sample of 40 undergraduates. The li te r a t u r e suggests IPS may be s tr e s s f u l fo r only anxiety-prone in d iv id u a ls. The in d iv id u a l records o f the HTA su b jects were examined to see i f th e re was support fo r th is supposition. Procedure Upon a r r iv a l a t th e la b o ra to ry, the su b je c t was seate d a t a desk in the te s tin g room w hile the experim enter explained th e procedures. Then th e S tate-a nxiety Inventory and th e T rait-a nxiety Inventory forms were administered to th e su b je c t. Following com pletion, th e su b ject was asked to s i t in a com fortable arm chair a t the o th e r end of the te s tin g room facin g the one-way m irro r which had been p a r tia lly blackened o u t. The th e rm isto r was attach ed and a d d itio n a l in s tru c tio n s about head and eye p o s itio n s were given. A no-stim ulus t r i a l run was

30 done to in su re accurate polygraph read in g s. Then th e te s tin g room lig h ts were extinguished and th e experim enter l e f t th e room. The sessio n s la s te d about 25 m inutes fo r the IPS groups. The c o n tro ls fo r the anxiety measures a lso s a t in th e darkened room fo r about 25 m inutes; however, they were asked to s i t q u ie tly w ith th e ir eyes closed fo r about a h a lf an hour w hile measures o f th e ir re s p ira tio n ra te would be recorded. No explan atio n about IPS was given sin c e they were never exposed to the lig h t fla s h e s. At the com pletion o f the se ssio n, each su b je c t was asked to complete th e S tate-a nxiety Inventory fo r th e second tim e.

31 CHAPTER IV RESULTS The E ffects of S e ria l P o sitio n I t was hypothesized th a t re s p ira tio n r a te w ill covary p o s itiv e ly w ith th e frequency o f in te rm itte n t p h o tic stim u la tio n. To e s ta b lis h th is re la tio n s h ip i t must f i r s t be shown th a t th e s e r i a l p o sitio n of th e f lic k e r period i s n o t the cau sal v a ria b le. Data fo r stim ulus p re sen ta tio n s in the same o rd in a l rank were considered to g e th e r to determ ine the e ffe c t o f s e r ia l p o s itio n. Since a l l th re e IPS groups received the f lic k e r frequencies in a d iffe re n t p a tte rn, th is procedure should d e te c t e f f e c ts due to s e r ia l p o sitio n independent of th e frequency of th e lig h t fla s h e s. The median response a t each o f the 12 o rd in a l ranks was determ ined fo r each of th e IPS groups. These median resp o n ses were th e n combined to form an average a t each o rd i n a l rank. These 12 averages were then compared to the 12 s e r ia l p o sitio n s to o b tain a Pearson c o rre la tio n c o e ffic ie n t. Data were also combined fo r re g re ssio n analyses using the mean response a t each o rd in a l rank fo r a l l su b je c ts combined and fo r v arious subgroups based upon the p a tte rn of IPS exposure and sex. With th ese procedures, a la rg e r number o f observations would be employed in the re g re ssio n an aly ses which may r e s u lt in a sm aller e rro r term due to the in c re ase in degrees of freedom. 19

32 Since th e re were two measures of r e s p ira tio n r a te, one a t the beginning of th e stim ulus p erio d s and one a t th e end of the stim ulus p e rio d s, and two methods of combining d a ta, one using th e median and one using the mean, th e re were four p o ssib le d a ta s e ts to consider regarding the re la tio n s h ip between re s p ira tio n r a te and th e s e r ia l p o sitio n of th e f lic k e r p e rio d s. These were th e median and mean re s u lts o f th e measure taken a t stim ulus onset and th e median and mean re s u lts o f th e measure taken a t th e end o f th e f lic k e r p erio d s. However, the means fo r th e second m easure, th e number of complete b reath in g cycles in th e l a s t 30 seconds of each f lic k e r p erio d, were not reported. Averaging th e se re s u lts to d eriv e means re s u lte d in mixed numbers (whole numbers w ith fra c tio n s ) which were in c o n siste n t w ith th e ra tio n a l fo r th is measure. Only com plete b reath in g cycles were counted f o r t h i s m easure, so o nly th e medians were u sed. Therefo re, th e median and mean analyses fo r the f i r s t measure of re s p ira tio n r a te and th e median a n a ly sis fo r th e second measure of re s p ira tio n r a te w ill be rep o rte d. The measure of re s p ira tio n taken a t the beginning o f the stim ulus p re se n ta tio n s was rep resen ted by the time in seconds req u ired by the f i r s t fiv e complete b re a th in g cycles in each f lic k e r p erio d. Since th is is an in v erse m easure, a p o s itiv e re la tio n s h ip between re s p ira tio n r a te and th e o rd in a l rank of the stim ulus would be rep resented num erically by a n eg ativ e v alu e. The a c tu a l c o rre la tio n c o e ffic ie n t obtained using th e median d ata combined from a l l th re e of the IPS groups was r = , a s t a t i s t i c a l l y n o n sig n ific a n t r e s u lt. The c o rre la tio n c o e ffic ie n t between re s p ira tio n r a te and th e s e r ia l

33 21 p o s itio n of the stim ulus using the mean d a ta combined from a l l th ree o f the IPS groups was a lso s t a t i s t i c a l l y n o n sig n ific a n t, r = However, two subgroups showed s ig n ific a n t e f f e c ts. The c o rre la tio n c o e ffic ie n ts fo r th e v ario u s subgroups a re presen ted in Table 1. Table 1 C o rrelatio n s Between the S e ria l P o sitio n o f th e F lic k e r Period and Mean R esp iratio n Rate as Measured by the Time Occupied by th e F ir s t Five B reathing Cycles in Each F lic k e r Period 3 Groups combined-females 3 Groups combined-males *.0563 Group I : Group I : Group I I : Group I I : Group I I I : Group I I I : A scending-d escending-fem ales A scending-d escending-m ales D escending-a scending-fem ales D escending-a scending-m ales Random Sequence-females Random Sequence-males *.0306 * P <.05 The measure of re s p ira tio n r a te taken a t th e end of th e stim ulus periods was rep resen ted by th e number of complete b reath in g cycles in the l a s t 30 seconds of each f lic k e r p e rio d. T herefore, a p o s itiv e re la tio n s h ip between r e s p ira tio n r a te and the o rd in a l rank of th e stim ulus would be rep resen ted num erically by a p o s itiv e value using th is measure. The a c tu a l c o rre la tio n c o e ffic ie n t obtained using the

34 median d ata combined from a l l th re e o f the IPS groups was r = , a c o rre la tio n which is n o t s t a t i s t i c a l l y s ig n if ic a n t. The E ffe c ts o f F lic k e r Frequency To e s ta b lis h the e f f e c t o f the f lic k e r frequency upon re s p ira tio n r a te, data f o r lik e frequencies were considered to g e th e r. The form at fo r these analyses was id e n tic a l to th a t previously described fo r s e r ia l p o s itio n. The f i r s t measure o f re s p ira tio n was rep resen ted by th e time in seconds fo r the f i r s t fiv e complete b re a th in g cycles in each f lic k e r p erio d. Since th i s is an inverse measure, a p o s itiv e re la tio n s h ip between r e s p ira tio n r a te and th e f lic k e r frequency would be represen ted num erically by a negative v alu e. The Pearson c o rre la tio n c o e ffic ie n t obtained u sin g the median data combined from a l l three IPS groups was r = , a s t a t i s t i c a l l y n o n sig n ific a n t re s u lt. The re s u lts using the mean d ata combined for a l l th re e IPS groups were also n o n s ig n ific a n t, r = Only one subgroup showed a s ig n ific a n t e f f e c t. The c o rre la tio n c o e ffic ie n ts fo r the various subgroups are p resented in Table 2.

35 Table 2 C orrelatio n s Between the Frequency of IPS and Mean R esp iratio n Rate as Measured by the Time Occupied by th e F ir s t Five B reathing Cycles in Each F licker Period 3 Groups combined-females 3 Groups combined-males Group I : Group I : Group I I : Group I I : Group I I I : Group I I I : A scending-d escending-fem ales A scending-d escending-m ales D escending-a scending-fem ales D escending-a scending-m ales Random Sequence-fem ales Random Sequence-m ales * *p <.05 However, th e second measure of re s p ira tio n r a t e, the number of com plete b reath in g cy c le s in the l a s t 30 seconds o f each f lic k e r p e rio d, showed a very stro n g p o s itiv e c o rre la tio n. The a c tu a l c o r r e la tio n c o e ffic ie n t o b tain ed using the median r a te combined fo r a l l th re e IPS groups was r =.8558 which is s ig n if ic a n t a t th e.03 le v e l. The s t a t i s t i c a l d e s c rip tio n of these d a ta is based upon a hypothe siz e d lin e a r monotonic re la tio n s h ip. The r e s u lts suggest a stro n g p o s itiv e re la tio n s h ip between the frequency of p h o tic s tim u la tio n and r e s p ira tio n r a te only when th e median responses o f the second measure i s considered. Corresponding median and mean analyses o f the f i r s t R ep ro d u ced with p erm issio n o f th e copyrigh t ow ner. Further reproduction prohibited w ithout p erm issio n.

36 measure are n o t su p p o rtiv e. However, a v is u a l p re s e n ta tio n of th e d ata from the f i r s t measure suggests a stro n g re la tio n s h ip but one which i s not m onotonic. Figures 1, 2, and 3 d e p ic t th e median response during the f i r s t and second p re se n ta tio n of each f lic k e r frequency fo r each IPS group. While th ese fig u re s do n o t suggest a monotonic r e la tio n s h ip, they do support th e notio n th a t th e ra te of re s p ira tio n i s a ffe c te d by th e frequency o f the p h o tic stim u la tio n. In a l l th ree IPS groups, th e p a tte rn of th e median responses fo r th e f i r s t p re sen ta tio n c lo se ly resem bles th e p a tte rn o f th e median responses fo r th e second p re s e n ta tio n irre s p e c tiv e of th e order in which th e d iffe re n t f lic k e r frequencies were d e liv e re d. There appears to be a c u rv ilin e a r p a tte rn w ith in c re ased re s p ira to ry responses occurring to frequency p re sen ta tio n s around 10 to 12 cycles per second and f a llin g o ff w ith freq u en cies below or above th is le v e l.

37 2 5 F ir s t p re s e n ta tio n o f stim u lu s fre q u e n c ie s 43.0 Second presentation o f stim ulus frequencies 42.0 SECONDS PER 5 BREATHING CYCLES F igure 1. R e sp ira tio n ra te d u rin g IPS f o r Group I : A scending-d escending p a tte rn

38 F i r s t p re s e n ta tio n o f stim u lu s freq u en cies Second p re s e n ta tio n o f stim u lu s fre q u e n c ie s SECONDS PER 5 BREATHING CYCLES t F ig u re 2. R e sp ira tio n r a t e d u rin g IPS fo r Group I I : D escending-a scending p a tte r n

39 27 F i r s t p r e s e n ta tio n of stim u lu s frequencies 39.4 Second p re s e n ta tio n o f stim u lu s freq u en cies 38.4 SECONDS PER 5 BREATHING CYCLES F ig u re 3. R e sp ira tio n r a t e d u rin g IPS fo r Group I I I : Random Sequence p a tte rn

40 I t was fu rth e r hypothesized th a t exposure to in te rm itte n t p h o tic stim u la tio n would in c re a se s ta te anxiety le v e ls. I f th is were the case, the th re e IPS groups should have s ig n if ic a n tly h ig h er scores on the second ad m in istra tio n o f the State-A nxiety Inventory than on th e f i r s t ad m in istra tio n as compared w ith th e c o n tro l group. This was n o t the case. In f a c t, a l l groups showed a s ig n ific a n t decrease in th e ir le v e ls of s ta te -a n x ie ty. These re s u lts are p resen ted in Table 3. Table 3 A Comparison o f P re- and Post-Experim ent Scores on the State-A nxiety Inventory IPS Group I : IPS Group I I : IPS Group I I I : C ontrol Group: A scending-d escending D escending-a scending Random Sequence No IPS t * t ** t ** t = ** *p<.05 **p <.01 An an a ly sis o f v arian ce on th e change sco res on th e State-A nxie.ty Inventory was s t a t i s t i c a l l y n o n sig n ific a n t (ANOVA F **.7276, p =.5422). In o th e r w ords, a l l su b je c ts had s ig n if ic a n tly lower s ta te -a n x ie ty le v e ls a f te r the experim ental sessio n s were completed reg ard less o f w hether or n o t they were exposed to in te rm itte n t p h o tic stim u latio n. In ad d itio n, th e re were no v erb al re p o rts o f extreme an x iety,