Current Biology Vol 15 No 11R412

Meditation altersperceptual rivalryin TibetanBuddhist monks

O.L. Carter1, D.E. Presti2, C. Callistemon1, Y. Ungerer1, G.B. Liu1 and J.D. Pettigrew1

Neuroscientific studies of themind are likely to benefit from theinsights and skills of TibetanBuddhist monks who havepracticed the historic tradition ofmeditative training over manyyears — a point made recently ata forum between a selection ofBuddhist leaders anddistinguished scientists [1].Perceptual rivalries, such asbinocular rivalry [2] and motioninduced blindness [3], are beingused to study the neuralmechanisms underlyingconsciousness and attention [2,4],as they involve fluctuations inconscious awareness despiteunchanging external stimulation.Tapping into the ability of TibetanBuddhist monks to control theflow of items being attended toand accessing consciousness, wefound that meditation alters theinherent fluctuations in consciousstate associated with perceptualrivalry.

With the support of HisHoliness the Dalai Lama, a total of76 Tibetan Buddhist monksvarying in experience from 5 to 54years of training (including three‘retreatist’ meditators, each withat least 20 years experience inisolated mountain retreats) weretested using non-intrusiveperceptual measures at, or near,their mountain retreats in theHimalaya, Zanskar and LadakhiRanges of India. Binocular rivalrywas induced with head-mounteddisplay goggles (Figure 1A) thatpresented horizontal and verticalgreen stationary gratings to theright and left eye, respectively(see Supplemental data availablewith this article online). In caseswhere coordinated button-pressresponses were not possible,verbal reports were recorded.

Harnessing the skills of highlytrained monks to control their

mental state, we report resultsfrom 23 monks corresponding totwo types of meditation,approximately translated as‘compassion’ (a non-referentialcontemplation of suffering withinthe world combined with theemanation of loving kindness) and‘one-point’ (through themaintained focus of attention on asingle object, the mind is calmedand the distracting influences ofother internal and external eventsis reduced).

Consistent with a recent study[5] linking different types ofmeditation with distinct patternsof neural activity, we foundcompassion and one-pointmeditation had similarlydifferential ‘functional’ effects onthe visual switching during rivalry.In contrast to compassionmeditation, which led to noobservable change in rivalry rate,one-point meditation led toextreme increases in perceptualdominance durations that werereported by 50% of monks after aperiod of one-point meditation(reports collected via button-press, as shown in Figure 1C,D, orverbally).

Additional prolongation/stabilization was reported(verbally) by the monks when theyviewed the rivalry display duringone-point meditation (Figure 1B).Within this group, three (includingtwo of the ‘retreatists’) reported

complete perceptual stabilitythroughout the entire 5 minutemeditation period. There was noconsistent pattern in the dominantorientation favored. Duringperiods of stabilization, thereported percepts often differedfrom either of the two presentedgratings, with qualitative changesin depth, color and width.

In some cases the perceptualdominance was complete; inother cases the non-dominantimage remained partially visible.For example, one monk reportedthe stable dominance of thevertical gratings appearing asthree-dimensional columns thatwere wider, brighter and closerthan during normal viewingconditions. During this time thehorizontal gratings remainedfaintly visible: set back in depth,they appeared thin and pale witha slight blue coloration. Theseresults contrast sharply with thereported observations of over1000 meditation-naive individualstested previously.

Because most of the monksserved as their own controls byparticipating in the differentmeditation conditions, the findingthat the increase in prolongation/stabilization was specific to onlyone of the meditation types(Figure 1B) suggests that theeffect is real, rather then simplyreflecting miscommunication or ageneral incapability to perform

Figure 1. Effects ofmeditation on perceptualswitching.

(A) Retreatist meditatorwearing display goggles. (B)Proportion of monks report-ing changes in rivalry switchrate during compassion(Comp) meditation, afterand during one-point medi-tation (slower, light blue;faster, red; stabilization,dark blue; white, nochange). (C) A representa-tive frequency histogramshowing phase duration(time between perceptualswitch) for horizontal, verti-cal and mixed (grey) per-cepts after no meditationand (D) the same monkshowing longer durationsafter one-point meditation.

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the task. Furthermore it suggeststhat the prolongation of rivalrydominance observed results fromthe intense attentional focus andthe practiced ability to stabilizethe mind during one-pointmeditation, rather than theprocess of meditation per se.

Volunteers were also tested onmotion induced blindness prior toany meditation (see Supplementaldata for details) and the meandisappearance duration reportedwas 4.1 s (s.d. ± 3.9 s), comparedto 2.6 s (s.d. ± 1.6 s) recordedfrom a group of 61 meditation-naive volunteers tested previously[6] (t = 2.8, p < 0.001) (Figure 2).The most extreme finding camefrom the ‘retreatist’ volunteer withthe most experience at meditation(25 years intense practice inmountain retreats). After a periodof ‘passive’ viewing hecommented that he couldmaintain the disappearanceindefinitely. So we suggested heattempt to ‘actively’ maintain thedisappearance and afterrecommencing, he reported thefirst reappearance of any of thethree yellow target dots after723 s of sustained motioninduced blindnessdisappearance!

The primary result of this studyis that individuals trained inmeditation can measurably alterthe normal fluctuations inconscious state induced bybinocular rivalry and motion-induced blindness. Themeditation specific changes in

visual function observed hereprovide new evidence in supportof recent electrophysiologicalstudies suggesting that differenttypes of meditation and trainingduration lead to distinguishableshort- and long-term changes atthe neural level [5,7].Furthermore, the reportedassociation between ‘focused’styles of meditation and changesin neural activity in prefrontalregions of the cortex [7,8] —regions that have been similarlyimplicated in sustainedattentional [9] and binocularrivalry [10] — supports claims ofhigh-level, top-down modulatoryeffects in perceptual rivalry [2],and strengthens recent linksbetween rivalry and attentionalmechanisms [4].

This study offers an initialcontribution towards increasedunderstanding of the biologicalprocesses underlying meditationand rivalry, while additionallyhighlighting the synergisticpotential for further exchangebetween practitioners ofmeditation and neuroscience inthe common goal ofunderstanding consciousness.

AcknowledgmentsThis investigation was financiallysupported by the Heffter ResearchInstitute, Santa Fe, New Mexico, USA,and a Stanley Foundation grant to J. D.Pettigrew. We would like to thank HisHoliness the Dalai Lama for his supportand help in facilitating the study, TenzinGeyche and Tenzin Sherab for essentiallogistical assistance and TseringTopgyal for recruitment of monks. Wewould also like to thank TashiChoephel, Kelsang Wangmo, NgodupBurkhar, Tenzin Sherab and DorjeeDhondup who assisted with Tibetan andLadakhi translations and the monksfrom the Institute of Buddhist Dialecticsand the Namgyal and Thikseymonasteries for their participation.

Supplemental data Supplemental data containing furtherexperimental details are available athttp://currentbiology.com/cgi/content/full/15/11/R412/DC1

References1. Barinaga, M. (2003). Buddhism and

neuroscience. Studying the well-trained mind. Science 302, 44–46.

2. Blake, R., and Logothetis, N.

(2002). Visual competition. Nat.Rev. Neurosci. 3, 13–21.

3. Bonneh, Y., Cooperman, A., andSagi, D. (2001). Motion inducedblindness in normal observers.Nature 411, 798–801.

4. Mitchell, J., Stoner, G., andReynolds, J. (2004). Object-basedattention determines dominance inbinocular rivalry. Nature 429,410–413.

5. Lehmann, D., Faber, P.L.,Achermann, P., Jeanmonod, D.,Gianotti, R.R., and Pizzagalli, D.(2001). Brain sources of EEGgamma frequency duringvolitionally meditation-induced,altered states of consciousness,and experience of the self.Psychiatry Res. 108, 111–121.

6. Carter, O., and Pettigrew, J. (2003).A common oscillator for perceptualrivalries? Perception 32, 295–305.

7. Lutz, A., Greischar, L.L., Rawlings,N.B., Ricard, M., and Davidson, R.(2004). Long-term meditators self-induce high-amplitude gammasynchrony during mental practice.Proc. Natl. Acad. Sci. USA 101,16369–16373.

8. Newberg, A., Alavi, A., Baime, M.,Pourdehnad, M., Santanna, J., andd’Aquili, E. (2001). Themeasurement of regional cerebralblood flow during the complexcognitive task of meditation: apreliminary SPECT study.Psychiatry Res. 106, 113–122.

9. Pardo, J.V., Fox, P.T., and Raichle,M.E. (1991). Localization of ahuman system for sustainedattention by positron emissiontomography. Nature 349, 61–64.

10. Lumer, E.D., Friston, K.J., andRees, G. (1998). Neural correlatesof perceptual rivalry in the humanbrain. Science 280, 1930–1934.

1Vision, Touch and Hearing ResearchCentre, University of Queensland, StLucia, Australia 4072.E-mail: o.carter@uq.edu.au2Department Molecular and CellBiology, University of California,Berkeley, California 94720, USA.

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Figure 2. Histogram showing thefrequency of respective disappearanceintervals during motion-inducedblindness for monks tested in thecurrent study (red) compared to a groupof 61 meditation-naive volunteers (blue)tested previously (for details see [6]).The two extreme values were notincluded in the statistical analysisreported in the text.

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