Human high intelligence is involved in spectral redshiftof biophotonic activities in the brainZhuo Wanga,b, Niting Wanga,b, Zehua Lia,b, Fangyan Xiaoa,c, and Jiapei Daia,b,c,1

aWuhan Institute for Neuroscience and Neuroengineering, South-Central University for Nationalities, Wuhan 430074, China; bDepartment of Neurobiology,The College of Life Sciences, South-Central University for Nationalities, Wuhan 430074, China; and cChinese Brain Bank Center, Wuhan 430074, China

Edited by Michael A. Persinger, Laurentian University, Canada, and accepted by Editorial Board Member Marlene BehrmannMay 20, 2016 (received for reviewMarch 24, 2016)

Human beings hold higher intelligence than other animals onEarth; however, it is still unclear which brain properties mightexplain the underlying mechanisms. The brain is a major energy-consuming organ compared with other organs. Neural signalcommunications and information processing in neural circuits playan important role in the realization of various neural functions,whereas improvement in cognitive function is driven by the needfor more effective communication that requires less energy.Combining the ultraweak biophoton imaging system (UBIS) withthe biophoton spectral analysis device (BSAD), we found thatglutamate-induced biophotonic activities and transmission in thebrain, which has recently been demonstrated as a novel neuralsignal communication mechanism, present a spectral redshift fromanimals (in order of bullfrog, mouse, chicken, pig, and monkey) tohumans, even up to a near-infrared wavelength (∼865 nm) in thehuman brain. This brain property may be a key biophysical basis forexplaining high intelligence in humans because biophoton spectralredshift could be a more economical and effective measure of bio-photonic signal communications and information processing in thehuman brain.

intelligence | ultraweak photon emissions | biophoton imaging |glutamate | brain slices

Despite remarkable advances in our understanding of brainfunctions, it is still unclear why human beings hold higher

intelligence than other animals on Earth and which brain propertiesmight explain the differences (1). Early studies have proposed thatbrain size and the degree of encephalization [encephalizationquotient (EQ)] might be related to the evolution of animal in-telligence, including that of human beings (2–4), but, so far, therelationship between relative brain size and intelligence is in-conclusive, and EQ is also not the best predictor of intelligence(1, 5–7). Communications and information-processing capacitybetween neurons in neural circuits play an important role in therealization of various neural functions, such as sensorimotorcontrol, learning and memory, consciousness, and cognition. Theneural network studies have indicated that neural signal trans-mission and encoding is in a nonlinear network mechanism (8–10), in which biophotons, also called ultraweak photon emission(UPE), may be involved (11). A recent study has demonstratedthat glutamate, the most abundant neurotransmitter in the brain,could induce biophotonic activities and transmission in neuralcircuits (12), suggesting that biophotons may play a key role inneural information processing and encoding and may be involvedin quantum brain mechanism (11, 13–16); however, the impor-tance of biophotons in relation to animal intelligence is not clear,in particular human high intelligence, such as problem-solvingand analytical abilities. We hypothesized that the spectral red-shift of biophotonic activities and transmission in the brain mayplay a key role. Here, we have provided experimental evidencethat glutamate-induced biophotonic activities and transmissionin brain slices present a spectral redshift feature from animals(bullfrog, mouse, chicken, pig, and monkey) to humans, which

may be a key biophysical basis for explaining why human beingshold higher intelligence than that of other animals.

ResultsBiophoton Spectral Imaging, Calibration, and Reference. Because ofthe ultraweak intensity feature of biophotons, it is usually diffi-cult to analyze biophoton spectral characteristics spatiotempo-rally, particularly in brain tissues. This paper introduces a methodto resolve this problem, allowing analysis of the spectral charac-teristics of glutamate-induced biophotonic activities and trans-mission by combining the recently developed ultraweak biophotonimaging system (UBIS) (12) with a new biophoton spectral anal-ysis device (BSAD).The BSAD consists of a slit and a transmission grating and is

placed just above the sample during biophoton imaging such thatthe biophoton spectral images can be obtained with UBIS whenbiophotons pass a slit and then a grating (Fig. 1). First, it isnecessary to determine the special spectral images for calibrationand reference, and such images were captured with UBIS byapplying various known-wavelength laser and light-emitting di-ode (LED) light sources for imaging. Under conditions of nor-mal and ultraweak intensity laser and LED imaging, we obtainedtwo types of photon spectral images: normal photon intensityspectral images (Fig. 2 A and B, Top) and ultraweak photonintensity spectral images (Fig. 2 A and B, Bottom). A light-reducing device was used to produce the ultraweak intensityphotons from various laser and LED light sources, and thephoton intensities were reduced to these levels (100–400 photons

Significance

It is still unclear why human beings hold higher intelligencethan other animals on Earth and which brain properties mightexplain the differences. The recent studies have demonstratedthat biophotons may play a key role in neural informationprocessing and encoding and that biophotons may be involvedin quantum brain mechanism; however, the importance ofbiophotons in relation to animal intelligence, including that ofhuman beings, is not clear. Here, we have provided experi-mental evidence that glutamate-induced biophotonic activitiesand transmission in brain slices present a spectral redshiftfeature from animals (bullfrog, mouse, chicken, pig, and mon-key) to humans, which may be a key biophysical basis forexplaining why human beings hold higher intelligence thanthat of other animals.

Author contributions: J.D. designed research; Z.W., N.W., F.X., and J.D. performed re-search; Z.W. and J.D. analyzed data; Z.L. contributed new reagents/analytic tools; andJ.D. wrote the paper.

The authors declare no conflict of interest.

This article is a PNAS Direct Submission. M.A.P. is a Guest Editor invited by the EditorialBoard.

Freely available online through the PNAS open access option.1To whom correspondence should be addressed. Email: jdai@mail.scuec.edu.cn.

This article contains supporting information online at www.pnas.org/lookup/suppl/doi:10.1073/pnas.1604855113/-/DCSupplemental.

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per square centimeter per second), similar to those of glutamate-induced biophotonic emissions in mouse brain slices (12).A spectral image presents three clear bands (one zero-order

fringe and two first-grade fringes) under the imaging condition ofthe present study based on the principle of grating imaging (Fig.2 A and B). We analyzed the distribution of gray values (GVs) ofzero-order and first-grade fringes in various laser spectral grayimages (SI Methods) and defined the relative central distance(△Lc) and minimum (△Lmin) and maximum (△Lmax) edge dis-tances from one of the two first-grade fringes to the center of thezero-order fringe (Fig. 2C and Fig. S1). We found that the laserwavelength (λ) is highly correlated to the △Lc, △Lmin, and△Lmax under conditions of normal and ultraweak light-intensityimaging (Fig. 2 D and E and Table S1). Therefore, a samplewavelength range can be calculated according to the △Lc,△Lmin, and △Lmax values of the sample and the following threelinear regression equations (SI Methods):

λave = 8.167ΔLc − 15. 47, [1]

λmin = 7.42ΔLmin + 151.8, [2]

λmax = 9.79ΔLmax − 296.6, [3]

where λave, λmin, and λmax are the average, minimum, and max-imum wavelength, respectively, under the conditions of ultra-weak photon intensity.We have verified the reliability using data from various LED

spectral images (Fig. 2B), and the results show that the calculatedwavelength ranges (λave, λmin, and λmax) of four LED light sourcesaccording to the regression equations above and the measuredvalues of △Lc,△Lmin, and △Lmax under the conditions of ultraweaklight intensities are approximately equal to or within the known-wavelength ranges (Fig. 2F) measured by a spectrometer (Fig. S2).Then, we tested the emission spectra from a small piece of

green leaves of sweet-scented osmanthus tree under the excita-tion condition of ambient light before imaging and found thatthey are 797 nm (λmin), 850 nm (λave), and 927 nm (λmax) (Fig. 2G and H), indicating that the detected spectra belong to therange of the phosphorescence and fluorescence emission spectraattributable to photosynthesis (17, 18).

Glutamate-Induced Biophotonic Activities and Spectral Redshift fromAnimals to Humans. Biophotonic emissions in mouse brain slicepresent four typical periods or stages (initiation, maintenance,washing, and reapplication, respectively) after the application of50 mM glutamate, and the origin of these stages is mainly at-tributable to the biophotonic activities and transmission alongaxons (12), suggesting that the analysis of the spectral charac-teristics of these biophotons may provide a new way to exploretheir importance in neural functions. In addition, the reasons forthe application of such a concentration of glutamate to activateand maintain the biophotonic activities and transmission alongneuronal axons or in neural circuits in mouse brain slices havebeen emphatically discussed in a previous study (12). In thepresent study, we investigated the spectral characteristics ofglutamate-induced biophotonic emissions in bullfrog, mouse,chicken, pig, rhesus monkey, and human brain slices. The prepa-rations of sagittal brain slices from bullfrogs, mice, and chickens andthe particular brain slices from six different brain regions (fivecortical areas and the hippocampus) in pigs, rhesus monkeys, andhumans are detailed in Fig. 3 A–C and SI Methods. Sevenpostmortem human brains obtained from the Chinese BrainBank Center (CBBC) were used for this study (Table S2). Therecovery of neural cells from postmortem brain materials withsuitable in vitro treatment is a key method to achieve glutamate-induced biophotonic emissions in human and pig brain slices,which is described specifically in SI Methods. Four typical stagesof biophotonic emissions after the application of 50 mM gluta-mate to a mouse brain slice, a postmortem pig hippocampusslice, and a human motor cortical slice present a similar pattern,as shown in Fig. 3D. Biophoton spectral images were obtained byimaging biophotonic emissions across the maintenance, washing,and reapplication periods (Fig. 3D and SI Methods), and thefirst-grade fringe presents a trend away from the zero-order andbecomes broader from bullfrog to human (in the order of bull-frog, mouse, chicken, pig, monkey, and human; Fig. 3E). Aspectral redshift trend was significantly obvious for λave and λmaxfrom animals to humans (Fig. 3 F–I), and the λmax is even up to anear-infrared wavelength (∼865 nm) in humans (Table 1). Theindividual differences of spectral values within the same speciesare very small, with nearly identical values in five bullfrogs,chickens, and mice. In addition, there were no significant dif-ferences in λave, λmin, or λmax between the different brain areas inthe pig and human (Fig. 3 J and K and Table S3), with the ex-ception of λmin between the certain areas (frontal cortex vs.motor cortex or temporal cortex, and motor cortex vs. hippo-campus) in the human brain (Table S3). Although statisticalanalysis could not be carried out for the monkey because onlythree brains were tested due to strict restrictions of the numberof rhesus monkeys for experimental research, the values of λave,λmin, or λmax obtained from different brain regions in threemonkeys were nearly identical, suggesting that the conclusionfrom the pig might apply to the monkey.

DiscussionIn the present study, the special prepared brain slices wereallowed to analyze the spectra of glutamate-induced biophotons,which has been proven to be the active biophotons (12), but notthe background biophotons that are generally believed to be aresult of oxidative metabolism and oxidative stress (19–21) be-cause the increase of biophotonic emissions by the application ofglutamate is not correlated to the change in aerobic metabolismbecause the initiation and maintenance of glutamate-inducedbiophotonic emissions cannot completely blocked by cytochromec oxidase inhibitor but could be significantly decreased by theapplication of protein phosphatase 2A (PP2A) inhibitor (okadaicacid potassium salt), which can induce the hyperphosphorylationof microtubule-associated protein tau and interferer with thefunction of microtubules (22).

Fig. 1. Schematic drawing of the UBIS and BSAD. UBIS was described indetail in a previous report (12). BSAD consists of a slit (1 mm wide and 1 cmlong) and a transmission grating (1,200 per millimeter) and is placed justabove the sample during biophoton imaging. The right plane is an enlargeddrawing of the BSAD in the left plane. The brain slice is incubated in achamber containing perfusion solution (also see SI Methods).

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The tendency of the spectral redshift of glutamate-inducedbiophotonic emissions in this study is in the order of frog, mouse,chicken, pig, monkey, and human, which is almost consistentwith the phylogenetic tree. Although the present imaging tech-nique could not distinguish and determine what types of neurons

emit what types of spectral biophotons or whether a neuron ortype of neurons emit different spectral biophotons, we indeedobserved the evolutionary conservation in glutamate-inducedbiophotonic emissions in the near-blue spectra (λmin) fromchicken to pig to monkey to human (Fig. 3 F and H).

Fig. 2. Photon spectral images for calibration and reliability confirmation. (A and B) Photon spectral images were obtained from three wavelength lasers(405 nm, 532 nm, and 650 nm) (A) and four wavelength LED lights (blue, green, yellow, and red) (B) under conditions of normal intensities (up planes) andultraweak intensities (down planes) (also see the detailed explanation in SI Methods), showing one zero-order fringe and two first-grade fringes. The twofirst-grade fringes present a trend away from the zero-order fringe from short to long wavelengths (blue to red). (C) Schematic drawing of a spectral image toanalyze the relative central distance (△Lc), minimum (△Lmin), and maximum (△Lmax) edge distances from the first-grade fringe (digit 1) to the center of thezero-order fringe (digit 0) with an image analysis software (also see Fig. S1A ). (D and E) There are linear relations between the wavelengths and △Lc, △Lmin,or △Lmax in three lasers under the conditions of normal (D) and ultraweak (E) intensities. The linear regression coefficients (R2) are 0.9999, 0.9989, and 0.9978for△Lc,△Lmin, and △Lmax, respectively, in D, and 0.9999, 0.9996, and 0.9990, respectively, in E; P = 0.005–0.042 (also see Table S1). (F) The relations betweenthe calculated wavelengths (λave, λmin, and λmax) of four LED light sources (bigger color symbols) based on the spectral images under the conditions ofultraweak light intensities and the known pick and wavelength ranges [smaller black symbols; 451 nm (410–492 nm; blue), 518 nm (450–586 nm; green), 590 nm(555–625 nm; yellow), and 632 nm (595–669 nm; red)] measured with a spectrometer (also see Fig. S2). The calculated λave is almost same as the known pickwavelength of each LED light. (G) Representative biophoton spectral image obtained from a tree leaf (sweet-scented osmanthus tree), showing the clearzero-order fringe and two first-grade fringes (60-s imaging time). (H) The calculated wavelengths (λave, λmin, and λmax) from five leaves of this type of treeaccording to regression Eqs. 1–3.

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There is no universally accepted definition of animal intelligenceand no procedure to measure and compare the differences in dif-ferent species; however, using mental and behavioral flexibility as acriterion for intelligence, it is generally accepted that, at least in

problem-solving and language abilities rather than the specializedbehaviors, to survive in their natural and social environments, hu-man beings are assumed to be more intelligent than monkeys andthat intelligence is decreasingly ordered as monkey > pig > (chicken

Fig. 3. Spectral redshift of glutamate-induced biophotonic emissions in brain slices presents an evolutional trend from animals to human. (A) Schematic drawing of thepreparation of a particular sagittal brain slice (∼2mm thickness) from a hemisphere of the mouse brain, which is identical in bullfrog and chicken brains. (B) The detailedregions of brain gyri dissected from primary occipital, motor, and sensory cortexes, the medial frontal cortex, and superior temporal cortex in a representative monkeybrain (arrows), which are also similar in pig and human brains. (C) The preparation of a cortical slice (∼3mm thickness) from a block of cortical gyrus of pig, monkey, andhuman; the dotted line indicates the cut position. This cortical slice contains all of the cortical layers and could ensure that the cut ends of the projection fibers originatingfrom cortical neurons are directed toward the lens of the UBIS during imaging. (D) The representative dynamic change of biophotonic activities was demonstrated byrelative GVs (RGVs) after the application of 50 mM glutamate in a mouse brain slice (blue curved line), a pig hippocampus slice (Pig-Hi) (green curved line), and a humanmotor cortical slice (human-Mc) [red curved line; CBBC no. 20160107; Table S2], presenting the four typical stages (initiation, maintenance, washing, and reapplication).These two human and pig brain slices were stored in modified ACSF (M-ACSF) at 0–4 °C for 12 and 24 h, respectively, before imaging. Real-time imaging is 120 min forregular biophoton images (an image every 1minwithout BSAD) and 100min for biophoton spectral images (an image every 25minwith BSAD) through the periods ofmaintenance (0–170 min), washing (171–195 min), and reapplication (196–220 min). The arrows indicate the start and stop time points for capturing biophotonspectral images. (E) Representative biophoton spectral images in animal and human brain slices. The first-order fringes present a trend away from the zero-orderfringes in the order of bullfrog, mouse, chicken, pig, monkey, and human, indicating a spectral redshift from animals to humans. (F) Change trends of glutamate-induced biophoton spectral ranges (λave, λmin, or λmax) in the bullfrog, mouse, chicken, pig, monkey, and human. (G–I) Comparison of the spectral differences in λave(F = 399; P < 0.0001) (G), λmin (F = 82; P < 0.0001) (H), or λmax (F = 569; P < 0.0001) (I) in the bullfrog, mouse, chicken, pig, monkey, and human. (J and K) Comparison ofthe spectral differences in λave, λmin, or λmax in different brain regions in the pig (J) and human (K). Data show the means ± SEM. The number of brain slices in F–I:bullfrog (n = 5), mouse (n = 5), chicken (n = 5), pig (n = 34), monkey (n = 11), and human (n = 31). The number of brain slices in different brain regions (N): 6, 6, 5, 7, 4,and 6 for frontal cortex (Fc), motor cortex (Mc), sensory cortex (Sc), primary occipital cortex (Oc), temporal cortex (Tc), and hippocampus (Hi), respectively, in the pig and6, 5, 4, 6, 3, and 7 for Fc, Mc, Sc, Oc, Tc, and Hi, respectively, in the human. Asterisks indicate a significant difference between the neighboring two groups in G–I: *P <0.01; **P < 0.001; ***P < 0.0001. Asterisks indicate a significant difference in different areas in J: Fc vs. Mc (**); Fc vs. Tc (*); Mc vs. Hi (*). *P < 0.05. **P < 0.01.

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and mouse) > bullfrog. Such a trend is consistent with our finding ofa spectral redshift. Interestingly, we found that the chicken exhibitsmore redshift than the mouse, raising the question whether chickenshold higher cognitive abilities than those of mice. It has been sug-gested that birds might have evolved from a certain type of dinosaur(23) and that dinosaurs, which dominated on Earth for a long time,should hold certain advanced cognitive abilities over other animals.Based on this theory, it may be true that poultry have higher cog-nitive abilities than rodents, at least in language abilities, becausecertain birds, such as parrots, are able to imitate human words.The neocortex in the brain is organized into columnar mod-

ules, which seem to be units of information processing (24),analogous to chips in a computer. The work of the brain involvesneural information processing that is mainly transmitted alongaxons and dendrites, which are analogous to optic fibers. Theneural information-processing capacity is an expensive adapta-tion for the economy of brain, and the improvement of cognitivefunctions such as language is driven by the need for more ef-fective communication that requires less energy (25). We foundobvious spectral redshift of glutamate-induced biophotonicemissions in the human brain cortex and hippocampus. Based onrecent knowledge of the level of intelligence, which is relatedanatomically to the number of cortical neurons and physiologi-cally to the speed of conductivity of neural pathways, the spectralredshift means that the human brain may use lower energybiophotons (longer spectra) to carry out neural signal commu-nications between neurons to be more effective and economical.It should be emphasized that despite the use of entangled

photons has realized quantum teleportation (transmission) (26),however, it is still not clear how the brain carry out neural in-formation transfer, coding and storage via biophotons. Recentexperimental results have shown that biophotons may transmitalong neural fibers and in neural circuits (12), and theoreticalanalyses have proposed that it is possible to realize the intensityand spectral coding and quantum computation via microtubulesbased on the physical features of biophotons (27, 28). In addi-tion, although the biophotonic intensity is very weak, this maynot affect them as a quantum information carrier because,according to the assumption and current experiential findings

of the quantum teleportation (transmission), the change ofquantum state would likely lead to information transfer if sucha state is in quantum entanglement (26).We hope that these findings can bring a new viewpoint to

understand the mechanisms of brain information transmissionand information processing and provide an explanation for whyhuman brains are better than those of other animals in someadvanced cognitive functions, such as language, planning, prob-lem-solving, and analytical abilities.Overall, if biophotonic activities and transmission dominate

the information neural processing and encoding mechanism inthe brain, then biophoton spectral redshift could improve andstrengthen cognitive abilities, which may not only provide animportant theoretical basis for understanding why human beingscould hold such a high degree in our intelligence but also providenew ideas for the development of artificial intelligence productsand models of a functioning brain.

MethodsThis study was carried out under strict accordance with the recommendationsin the Guide for the Care and Use of Laboratory Animals of the NIH (29). Theprotocol was approved by the Committee on the Ethics of Animal Experimentsof South-Central University for Nationalities. Detailed information regardingmaterials and methods is described in SI Methods. Human brain materials wereobtained from the CBBC by autopsy through the human body donation pro-gram, which is organized and implemented by the Wuhan Red Cross Society.According to the protocol of CBBC and the human body donation program,specific permission for brain autopsy and use of the brain material and medicalrecords for research purposes were obtained either from the donors them-selves or from relatives, and also approved by the Biomedical Research EthicsCommittee of South-Central University for Nationalities. When a body donorwas deceased, the donation program office at Wuhan Red Cross Society wasfirst informed by either from doctors or from relatives usually by telephone.Then donation program coordinators would arrange the transport of donatedbody to an approved autopsy center, where the brain was carefully removedaccording to a standard procedure and collected by CBBC.

ACKNOWLEDGMENTS. This work was supported by National Natural ScienceFoundation of China Grant 31070961, Sci-Tech Support Plan of HubeiProvince Grant 2014BEC086, and the research team fund of the South-Central University for Nationalities (Grant XTZ15014).

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Table 1. Spectra in various species

Species (N)

Spectra

λave, nm λmin, nm λmax, nm

Bullfrog (5) 600.3 ± 0.82 522.1 ± 0.74 691.2 ± 0.98Mouse (5) 646.9 ± 1.53*** 591.1 ± 2.78*** 711.8 ± 0.0**Chicken (5) 667.3 ± 2.00*** 607.4 ± 2.97* 739.2 ± 1.96***Pig (34) 682.3 ± 0.68*** 604.9 ± 1.29 777.7 ± 0.75***Monkey (11) 696.9 ± 0.85*** 609.8 ± 1.76 806.1 ± 1.49***Human (31) 714.6 ± 1.59*** 595.6 ± 2.13*** 865.3 ± 2.74***F value; P value F = 399; P < 0.0001 F = 82; P < 0.0001 F = 569; P < 0.0001

λave, λmin, and λmax are the average, minimum, andmaximumwavelength, respectively; N, the number ofbrain slices. Asterisks indicate a significant difference between the neighboring two groups: *P < 0.01; **P <0.001; ***P < 0.0001.

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