by OD JONES · 2009 · Cited by 136 — Some of the details of fMRI defy short descriptions, involve technical details NEUROSCIENCE 159 (2005); J.D. Trout, Seduction Without Cause: Uncovering
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Brain Imaging for Legal Thinkers: A Guide for the Perplexed Copyright © 2009 Stanford Technology Law Review. All Rights Reserved. Brain Imaging for Legal Thinkers: A Guide for the Perplexed O WEN D. J ONES , J OSHUA W. B UCKHOLTZ , J EFFREY D. S CHALL , R ENE M AROIS 1 C ITE AS : 2009 S TAN . T ECH . L. R EV . 5 http://st lr.stanford.edu/ pdf/ jones – brain – imaging .pdf INTRODUCTION ¶1 It has become increasi ngly common for brain images to be proffered as evidence in civil and criminal litigation. 2 This Article offers some general guidelines to legal thinkers about how to understand brain imaging studies or at least avoid misunderstanding them. And it annotate s a published brain imaging study by several of the present authors (and others) in order to illustrate and explain, with step – by – step commentary. 3 ¶2 Brain images are offered in legal proceedings for a variety of purposes, as Professors Carter Snead and Gary Marchant have usefully surveyed. 4 On the civil side, neuroimaging has been offered in constitutional, personal injury, disability benefit, and contract cases, among others. For example, in Entertainment Software . v. Blagojevich , 5 the court considere d whether a brain imaging study could be used to show that exposure to violent video games increases aggressive thinking and behavior in 1 Owen D. Jones is Professor of Law and Professor of Biological Sciences at Vanderbilt University. Joshua W. Buckholtz is a neuroscience graduate student at Vanderbilt University. Jeffrey D. Schall is E. Bronson Ingram Professor of Neuroscience at Vanderb ilt University. Rene Marois is Associate Professor of Psychology at Vanderbilt University. Jones, Schall, and Marois are members of the MacArthur Foundation Law and Neuroscience Project, of which Jones also serves as Co – Director. The first two authors cont ributed equally to this Article . Correspondence to: owen.jones@vanderbilt.edu or rene.marois@vanderbilt.edu. This Article was prepared for the Stanford Technology Law Review 2009 Symposium on Neuroscience and the Courts: The Implications of Advances in Neu rotechnology . We received helpful comments from Gary Marchant and Teneille Brown, as well as from participants at conferences of the MacArthur Foundation Law and Neuroscience Project, the 2008 and 2009 Conferences on Empirical Legal Studies, and the Arizo Bailey Spaulding and Francis Shen provided valuable research assistance. Preparation of this Article was supported b y the John D. and Catherine T. MacArthur Foundation, The Regents of the University of California, and Vanderbilt University. 2 For an overview of issues, see Jeffrey Rosen, The Brain on the Stand , N.Y. T IMES M AG . , Mar. 11, 2007, at 49; Stacey A. Tovino, Fu nctional Neuroimaging and the Law: Trends and Directions for Future Scholarship , 7 A M . J. B IOETHICS 44 (2007). A sampling of the rapidly – growing scholarship at the law/neuroscience intersection appears infra note 32. 3 The full complement of authors is: Jo shua W. Buckholtz, Christopher L. Asplund, Paul E. Dux, David Zald, John C. Gore, Owen D. Jones, and Rene Marois. The article was published as The Neural Correlates of Third – Party Punishment , 60 N EURON 930 (2008). 4 A very useful survey, on which we draw in part in the paragraphs that follow, has been prepared by Professor Carter Snead. See C ARTER S NEAD , N EUROIMAGING AND THE C OURTS : S TANDARD AND I LLUSTRATIVE C ASE I NDEX , (2006), http://www.ncsconline.org/d_research/stl/June06/Snead.doc . Our research also b enefitted from Gary Marchant, Brain Scanning and the Courts: Criminal Cases, Presentation to the Research Network on Legal Decision Making, MacArthur Foundation Law and Neuroscience Project (Oct. 11, 2008). 5 404 F. Supp. 2d 1051 (N.D. Ill. 2005). Stanford Technology Law Review
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Brain Imaging for Legal Thinkers: A Guide for the Perplexed Copyright © 2009 Stanford Technology Law Review. All Rights Reserved. adolescents. In Fini v. General Motors Corp , 6 brain scans were proffered to help determine the extent of head injuries from a car accident. In Boyd v. Bert Bell/Pete Rozelle NFL Players Retirement Plan , 7 a former professional football player proffered brain scans in an effort to prove entitlement to neuro – degenerative disability benefits. And in Van Middlesworth v. Century Bank & Trust Co. 8 , involving a dispute over the sale of land, the defendant introduced brain images to prove mental incompetency, resulting in a voidable contract. ¶3 In criminal cases, brain images are sometimes invoked to support an argument that a defenda nt is incompetent to stand trial. In U nited S tates v . Kasim , for example, Kasim was found to be demented, and incompetent to stand trial for Medicaid fraud , on the basis of medical testimony that included brain images. 9 Brain images are also increasingly p roffered by the defense at the guilt – determination phase, in an effort to negate the mens rea element of a crime, and to thereby avoid conviction. For example, in People v. Weinstein , 10 a defendant accused of strangling his wife and throwing her from a twe lfth floor window sought to introduce images of a brain defect, in support of an argument that he was not responsible for his act. And in People v. Goldstein, 11 a defendant sought to introduce a brain image of an abnormality, in an effort to prove an insani ty defense, after he pushed a woman in front of a subway train, killing her. ¶4 Brain images have also been proffered at the sentencing phase of criminal cases, in furtherance of mitigation. For example, in Oregon v. Kinkel , 12 a boy convicted of killing and in juring fellow students in a high school cafeteria sought to introduce brain images of abnormalities, in an effort to secure a more lenient sentence. Brain images have been offered in Coe v. State , 13 for example to argue that a convicted murderer is not comp etent to be executed. And accessibility to brain imaging technology has even been litigated in Ferrell v. State 14 and People v. Morgan 15 for instance in the amount ed to ineffective assistance of counsel. ¶5 For better or worse, the full complement of cases at the intersection of neuroscience and law is now too large for comprehensive overview in part because many of the cases do not result in reported decisions. 16 While there is no denying that brain imaging is a powerful tool, whether used for medical or legal purposes, it is also clear that, like any tool, brain imaging can be used for good or for ill, skillfully or sloppily, and in ways useful or irrelevant. ¶6 We are co ncerned that brain imaging can be misused by lawyers (intentionally or unintentionally) and misunderstood by judges and jurors. Consequently, our aim in this Article is to provide information about the operation and interpretation of brain imaging techniqu es, in hopes that it will increase the extent to which imaging is properly interpreted, and conversely decrease the extent to which it is misunderstood or misused. We provide this information across two Parts and one Appendix. ¶7 Part I of the Article provide s some very brief background on modern brain imaging, with particular emphasis on one wide – spread and powerful technique, known as functional magnetic 6 No. 227592, 2003 Mich. App. LEXIS 884 (Mich. Ct. App. Apr. 8 2003). 7 410 F.3d 1173 (9th Cir. 2005). 8 No. 215512, 2000 Mich. App. LEXIS 2369 (Mich. Ct. App. May 5, 2000). 9 United States v. Kasim, No. 2:07 CR 56, 2008 U.S. Dist. LEXIS 89137 (N.D. Ind. Nov. 3, 2008). See also McMurtey v. Ryan, 539 F.3d 1112 (9th Cir. 2008); United States v. Gigante, 982 F. Supp. 140 (S.D.N.Y. 1997). 10 591 N.Y.S.2d 715 (N.Y. Sup. Ct. 1992). 11 786 N.Y.S.2d 428 (N . Y . Sup. Ct. 2004) , overruled on other grounds , 6 N.Y.3d 119, 843 N .E.2d 727, 2005 N.Y. LEXIS 3389 (2005) . 12 56 P.3d 463 (Or. Ct. App. 2002) . 13 17 S.W.3d 193 (Tenn. 2000) . 14 918 So.2d 163 (Fla. 2005) . 15 719 N.E.2d 681 (Ill. 1999) . 16 One of the many efforts under way, within the MacArthur Foundation Law and Neuroscience Pr oject, is a study by Hank Greely and Teneille Brown to find all actual and attempted uses of neuroimaging in criminal cases in California after January 1, 2006, regardless of whether such uses are mentioned in published opinions.
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Brain Imaging for Legal Thinkers: A Guide for the Perplexed Copyright © 2009 Stanford Technology Law Review. All Rights Reserved. resonance imaging (fMRI). The physics of fMRI, and the statistics accompanying the analyses that generate brain images, are complicated. We will make no effort to provide a comprehensive or detailed exploration of the subject. There are many existing textbooks that cover this material to great depths, often far greater than legal thinkers will need to master, for the specific contexts in which brain images are (potentially) legally relevant. 17 ¶8 Instead, we will aim here to focus on what a lawyer needs to know, in order to have a basic understanding of what works how and why. Our goal is to present this in an acc essible way, recognizing (as we trust our readers to allow us) that simplifying discussions are illustrative of general principles, but obviously ignore the richer detail that enables deeper appreciation of important caveats and subtleties. ¶9 Part II of this Article then turns to provide, in brief and accessible overview, a variety of key concepts to understand about the legal, biological, and brain imaging contexts at this particular law/neuroscience intersection, as well as a variety of guidelines we (and i n some cases others) recommend to help avoid the various factual errors, logical traps, and analytic mis – steps that can all too quickly lead away from sound and sensible understandings of what brain images can mean and equally what they cannot. Make no mis take: we are not the only researchers concerned about potential misunderstandings of brain images. 18 A great many cautions have been swirling about in the literature, often offering multiple versions of key and basic points about the limitations of the tech nologies, and we hope here to distill some of those, add others, and explain the set in a way that we hope provides a concise and useful introduction to legal thinkers approaching this interdisciplinary nexus for the first time. ¶10 The Appendix to this Articl e then provides a concrete illustration of how to read an fMRI study. We will not over – claim. Some of the details of fMRI defy short descriptions, involve technical details unlikely to be relevant in legal contexts, or both. On the other hand, much of the technical jargon, and many of the basic concepts one will encounter in an fMRI study, are clear with just a little explanation, oriented toward the audience we anticipate. We attempt to provide this in an accessible, informative way assuming no particular scientific sophistication of the reader. ¶11 Specifically, the core of the Appendix is a 2008 fMRI study (co – authored by three of us and others) that used fMRI techniques to investigate how brains are activated during punishment decisions. Though we do not ant icipate that the substantive findings will necessarily find immediate utility in litigation, we believe that legal thinkers reading an fMRI study will learn most from a study 17 See, e.g. , S COTT A. H UET TEL ET AL ., F UNCTIONAL M AGNETIC R ESONANCE I MAGING ( 2d ed. 2009); A LFRED L. H OROWITZ , MRI P HYSICS FOR R ADIOLOGISTS : A V ISUAL A PPROACH (3d ed. 1995); F UNCTIONAL MRI: A N I NTRODUCTION TO M ETHODS (Peter Jezzard et al., 2001). Useful introductions to broader cog nitive neuroscience, of which brain – imaging is but a part, appear in: M ICHAEL S. G AZZANIGA ET AL ., C OGNITIVE N EUROSCIENCE : T HE B IOLOGY OF THE M IND (3d ed. 2008); J AMIE W ARD , T HE S TUDENT S G UIDE TO C OGNITIVE N EUROSCIENCE (2006); E SSENTIALS OF N EURAL S CIENCE AND B EHAVIOR (Eric R. Kandel et al. eds., 1995); M ARIE T. B ANICH , C OGNITIVE N EUROSCIENCE AND N EUROPSYCHOLOGY (2d ed. 2004); M ARK F. B EAR ET AL ., N EUROSCIENCE : E XPLORING THE B RAIN (3d ed. 2006); N EUROSCIENCE (Dale Purves et al. eds., 4th ed. 2007). 18 The limits of brain imaging techniques are widely known to brain imaging researchers, and many brain imaging researchers are broadly concerned about misunderstandings among laypeople. A non – exhaustive list of important cautionary and explanatory articles, whic h have influenced some of our approaches below, include: John T. Cacioppo et al., , 85 J. P ERSONALITY AND S OC . P SYCHOL . 650 (2003); Dean Mo bbs et al., Law, Responsibility, and the Brain , 5 PL O S B IOLOGY 693 (2007); Eric Racine et al., fMRI in the Public Eye , 6 N ATURE R EVS . N EUROSCIENCE 159 (2005); J.D. Trout, Seduction Without Cause: Uncovering Explanatory Neurophilia , 12 T RENDS C OGNITIVE S CI . 281 (2008); Society of Nuclear Medicine Brain Imaging Council, Ethical Clinical Practice of Functional Brain Imaging , 37 J. N UCLEAR M ED . 1256 (1996); Michael S. Gazzaniga, The Law and Neuroscience , 60 N EURON 412 (2008); Joseph H. Baskin et al., Is A Pictu re Worth A Thousand Words? Neuroimaging in the Courtroom , 33 A M . J.L. & M ED . 239 (2007); Russell A. Poldrack et al., Guidelines for Reporting an fMRI Study , 40 N EURO I MAGE 409 (2008); Nikos K. Logothetis, What We Can Do and What We Cannot Do With fMRI , 453 N ATURE 869, (2008); W ILLIAM R. U TTAL , N EUROSCIENCE IN THE C OURTROOM : W HAT E VERY L AWYER S HOULD K NOW ABOUT THE M IND AND THE B RAIN (2008). One of the works most critical of how brain imaging results can be interpreted is W ILLIAM R. U TTAL , T HE N EW P HRENOLOGY : T HE L IMITS OF L OCALIZING C OGNITIVE P ROCESSES IN THE B RAIN (2003).
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Brain Imaging for Legal Thinkers: A Guide for the Perplexed Copyright © 2009 Stanford Technology Law Review. All Rights Reserved. that inherently addressed matters relevant to law in this case, the decision whet her or not to punish someone for criminal behavior and, if so, how much. ¶12 To facilitate that learning in this concrete application, the Stanford Technology Law Review has generously afforded us the unique opportunity to annotate the Article in the margin wi th explanations of various terms and contexts, as they appear throughout the study. I. BRAIN – IMAGING: A VERY BRIE F OVERVIEW ¶13 There are many kinds of brain images. All readers are likely familiar with the way x – rays, and the closely aligned technique known as computed tomography (CT) scanning, can show various structural anomalies in the body, including in the brain. In these techniques, radiation aimed at and passing through the body forms images on photographic film. The varying density of different tissue s in the body results in varying levels of radiation reaching the film creating, in turn, an image of internal structures. (For example, bone tissue appears as white, while soft tissue appears gray.) CT scanning varies from conventional x – rays by virtue of collecting images from multiple angles rotating around the body, which images are then combined by computers into cross – sectional representations. These techniques (like magnetic resonance imaging, which will be discussed in a moment) are used for informa tion about how various parts of the body are structured . They can show whether structures are intact, and can reveal damage, atrophy, intrusions, and developmental anomalies. They do not, however, collect or provide information about how those body parts a re actually functioning. ¶14 PET scanning , which refers to positron emission tomography , is one of the techniques that enable researchers to learn about how the brain functions , as it is actually doing so. With PET, a researcher injects a subject with radioact ive tracers that move through the bloodstream and accumulate in different locations and concentrations in the brain, over time, as different parts of the brain increase and decrease activity (such as glucose metabolism) that is associated with brain functi on. (A similar technique, known as SPECT , uses single photon emission computed tomography .) ¶15 EEG and MEG , short for electroencephalography and magnetoencephalography respectively , records electromagnetic fluctuations in various parts of the brain, as the br ain is functioning, using non – invasive sensors applied to the scalp. 19 In research laboratories, the EEG signals can be analyzed in relation to stimuli or responses to obtain event – related potentials (ERP) which were used before brain imaging was developed to make inferences about the brain processes underlying perceptual, cognitive and motor processes. 20 ¶16 fMRI (f unctional magnetic resonance imaging 21 ) uses the technology of regular magnetic resonance imaging adapted to detect changes in hemodynamic (literally properties of the brain occurring when the subject is engaged in very specific mental tasks. In a nutshell (and with a reminder that we are over – works. ¶17 At its most basic, fMRI can be under stood as a tool for learning which regions of the brain are working, how much, and for how long, during particular tasks. In much the same way that the body delivers more oxygen to muscles that are working harder, the body delivers more oxygen to brain reg ions that work harder. The fMRI technique measures blood oxygenation levels within small as those levels change across time with the 19 This signal is used in conjunction with measures like heart – rate and skin electrical conductance to constitute the polygraph procedure that is used commonly in a context of detecting dec eption. Although used commonly by the U.S. government and police departments, the fundamental limitations of these procedures have been thoroughly described. See, e.g. , C OMM . TO R EVIEW THE S CIENTIFIC E VIDENCE ON THE P OLYGRAPH , N AT L R ESEARCH C OUNCIL , T HE P OLYGRAPH A ND L IE D ETECTION (2003) 20 S TEVEN J. L UCK , A N I NTRODUCTION TO THE E VENT – R ELATED P OTENTIAL T ECHNIQUE (2005). Some have attempted to use ERP signals in legal settings, but the limitations of this approach are well – known and can serve as lessons for the interpretation of brain imaging information. 21 – case, by convention.
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Brain Imaging for Legal Thinkers: A Guide for the Perplexed Copyright © 2009 Stanford Technology Law Review. All Rights Reserved. varying metabolic demands of active neurons. 22 Changes in demand for oxygen are widely considered to be reliable proxies for inferring the fluctuating activity of the underlying neural tissue. 23 ¶18 The physical principles underlying fMRI are quite complex. But in general terms the technology works as follows: An fMRI machine creates a nd manipulates a primary magnetic field, 24 as well as several smaller magnetic fields (one in each three – dimensional plane) that can be quickly varied in orientation and uniformity. Recall (from basic physics) that protons within the nuclei of atoms spin on an axis and carry a positive charge. As they spin, these electric charges form what can be thought of as tiny magnets. When a person is inserted (typically horizontally) into the open bore of an fMRI machine, the previously random axes of spin, for many p rotons, align, like iron filings along a magnet. That is, the axes begin to point in the same direction. Researchers then administer to the small bird – temporarily. When the pulses stop, the axes gradually return to their original orientation, releasing aracteristics of the released energy affected by the relative concentrations of oxygenated and deoxygenated blood in local brain tissue. Crucially, as these concentratio ns are affected by regional changes in brain activity, they provide indirect markers of neural activity that form the basis of the fMRI signal. The machine enables localization of these signals in space by collecting them from man brain. And the technique enables localization of these signals in time by recording the signals many times over a period of several seconds for each mental event. A ole brain is acquired every couple of seconds or so, enabling the rapid collection of many of these three – experimental paradigm. II. KEY CONCEPTS AND GUIDELINES ¶19 This Part is divided into four se ctions. These address the legal context, the biological context, the intersection of law and biology, and finally, with that preparatory background, the brain imaging context. We proceed in this way because one cannot gain a clear understanding of brain im aging, and its intersection with the legal system, without first considering the underlying legal and biological contexts, and their background interactions. A. The Legal Context ¶20 With terrific , new , whiz – bang technology which can reveal inner structures an d workings of the brain it is all too tempting to jump past the more mundane legal issues, and to race to apply new techniques to solve new problems in new ways. ¶21 But hold the horses. Although our principal purpose here is to discuss how to read (and not re ad) brain imaging evidence, we would be remiss not to first anchor the discussion in the legal contexts in which those images might, arguably, be admissible. The territory here is broad, and could occupy us for some time. But to be brief, t here are a varie ty of questions to keep in mind, at the outset, in order to understand the specific legal context in which brain imaging might be considered in the courtroom. ¶22 The threshold consideration, of course, is: Are the proffered brain images relevant? Because beha vior comes from the brain, and the legal system often cares not only about how someone acted but also 22 See generally H UETTEL ET AL . , supra note 17 . 23 There are varying opinions in the neuroscience community about how conclusi ve an understanding there is of the fMRI beyond where brain activation occurred about behavior and mental states. See, e.g., Logothetis, supra note 18; Poldrack, supra not e 18. 24 Magnetic fields are described in Tesla units. A 3 – Tesla machine (which uses super – cooled electrical coils) generates a magnetic field roughly 60,000 times the magnetic field of the Earth.
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Brain Imaging for Legal Thinkers: A Guide for the Perplexed Copyright © 2009 Stanford Technology Law Review. All Rights Reserved. why, it is tempting to assume that brain images of people important to the litigation will provide legally relevant information, of one sort or another. B ut this is, in fact, not a decision to reach lightly. ¶23 What specific legal questions do the images purportedly address? Contexts vary considerably, even within the civil and criminal halves of the docket (each of which bears differing underlying standards o f proof). Within civil cases, for example, there are a wide variety of different legal purposes into which brain images might conceivably plug. Are brain images proffered to help establish liability, such as in the case of a medical malpractice action? To demonstrate a pre – existing condition, such as in the case of a dispute over insurance coverage? To help estimate damages, such as in the case of a car accident? And within criminal cases, are brain images proffered during the liability phase , in an effort mental state requisite for conviction? Are they instead proffered during the sentencing phase, in an effort to mitigate penalty? Are they proffered as eviden ce of lying or truthfulness? ¶24 It is important to remember that the admissibility of brain images is not simply a matter of whether they are scientifically sound. The potential relevance and hence admissibility of brain images will vary, according to the spe cific legal issue at hand within civil and criminal contexts. Put another way, the admissibility of brain images depends largely on their perceived potential relevance (if any) to the issue to be determined , independent of (and often before) considering th e quality and interpretation of the specific images themselves. ¶25 What, specifically, do the images allegedly demonstrate, and how well does that connect to the legal issues at hand? Some of the many variables that may come into play here include: Are these structural or functional images? When were they taken? ( For example, before or after events in question? ) How recently? Under what circumstances were they procured? ( For example, what specific mental tasks was the subject executing during functional imagin g?) What is being compared to what? ( For example: A re these before and after images of the same brain? ; a group – avera ged composite, for contrast?) ¶26 What are the applicable standards for the admissibility of scientific evidence? As is well known, the federal and state systems can have (and often do have) different standards for the admission of scientific evidence. And the state standards vary among the states. It is therefore necessary to note that the backdr op of all that follows below is the specific legal regime under which images are to be evaluated for potential relevance, within the specific context of the specific matters in dispute. Although it is not our purpose here to explore the applicability of sc ientific evidence law to brain images, we would be remiss not to flag the centrality of evidentiary rules and contexts to all that follows. Interested readers will find comprehensive discussion of scientific evidence generally in the treatise M ODERN S CIENT IFIC E VIDENCE . 25 B. The Biological Context ¶27 Understanding the potential relevance of brain images to law also requires a few words of general background about the relationship between biology and behavior generally. Key things to keep in mind (generally spea king) include 26 : All behavior results from the interaction of genes, environments (including social contexts), developmental history, and the evolutionary processes that built the brain to function in the ways it does. Behavior originates in the physical an d chemical activities of the brain. 27 25 M ODERN S CIENTIFIC E VIDENCE : T HE L AW AND S CIENCE OF E XPERT T ESTIMONY ( David L. Faigman et al., eds., 2006). It examines the cases that established those tests and discusses subsequent cases that applied and further develope d those tests. 26 Interested readers can find further information about these background principles in a variety of sources (as well as in the citations that they, in turn, provide). See, e.g. , Jeffrey D. Schall, On Building A Bridge Between Brain And Beha vior , 55 A NN . R EV . P SYCH . 23 (2004). 27 Yes, the alert reader will point out that some behavior, such as reflexes, leaps right out of the spinal cord. In the text, w e are speaking in generalities.
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Brain Imaging for Legal Thinkers: A Guide for the Perplexed Copyright © 2009 Stanford Technology Law Review. All Rights Reserved. 1. Anatomical imaging and functional imaging are importantly different. ¶30 Two anatomical images, taken one minute apart, will ordinarily look identical. Yet two functional images, from data collected one minute apart, coul d look completely different. One reason this is so is simply that, in the latter case, brain activity changes rapidly. Another reason is because fMRI brain images are built statistically, not recorded photographically. In the typical fMRI case, h undreds of recordings are made of each voxel in the brain, at slightly different times (e.g., every two seconds). Each recording of each voxel within a given trial is analogous to a single frame in a movie. Learning what happens within each voxel, over time, is akin to watching motion seem to emerge from the observation of successive snapshots that comprise a moving picture. But that metaphor only captures part of the fMRI technique, because there are subsequently many repeat recordings of that voxel, under similar c onditions, on many consecutive trials the re sults of which are typically the n averaged across trials. Complicating matters further is that there are about one hundred thousand voxels within the brain, and what typically matters is how neural activity withi n those voxels is varying over time, in relation to some task the subject(s) undertake while being scanned. Furthermore, within each voxel are millions of neurons of different types, interacting in ways that could be mechanistically different but indisting uishable from the measure of fMRI. In the end, fMRI brain images lay the result of any one of many possible statistical tests overtop of an anatomical image of a selected slice of the brain. That is, an fMRI image is a composite of an anatomical image, of choosing. 2. Functional b rain imaging is not mind reading. ¶31 There is more to a thought than blood flow and oxygen . fMRI is very good at discovering where brain tissue is active (commonly by highlighting differences between brain activations during different cognitive tasks). But differences are not thoughts. fMRI can show differences in brain activation across locati ons, across time, and across tasks. But that often does not enable any reliable conclusion about precisely what a person is thinking. 30 3. ¶32 Images are only as good as the manner in whi ch the researcher designed the specific task or experiment, deployed the machine, collected the data, analyzed the results, and generated the images. It is important to remember that fMRI images are the result of a process about a process. Multiple choices and multiple steps go into determining exactly what data will be collected, how, and when as well as into how the data will be analyzed and how it will be presented. 4. Group – averaged and individual brain images are importantly different. ¶33 Most brain imagi ng research is directed toward understanding how the average brain , within a subject population, is activated during different tasks. This is not at all the same thing as saying either that all brains performing the same task activate in the average way, o r saying that the activation of a single brain can tell us anything meaningful about the operation of the average brain. Consequently: Do not assume that the scan of any individual is necessarily representative of any group. Do not as sume that the averaged scan of any group will necessarily be representative of any individual. 30 There appear to be some exceptions. See, e.g. , John – Dylan Haynes et al., Reading Hidden Intentions in the Human Brain, 17 C URRENT B IOLOGY 323 (2007) (determining through brain imaging, with up to 71% accuracy, which of two tasks a person is covertly intending to perform); Y. Kamitani & F. Tong, Decoding the Visual and Subjective Contents of the Human Brain , 8 N ATURE N EUROSCIENCE 679 (2005) (determining through brain imaging, with near 80% accuracy, which of two overlapping visual pa tterns a person is paying attention to); S. A. Harrison & F. Tong, Decoding Reveals the Contents of Visual Working Memory in Early Visual Areas, 458 N ATURE 632 – 35 (2009) (determining through brain imaging, with 83 – 86% accuracy, which of two visual patterns a person is actively maintaining in memory).
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Brain Imaging for Legal Thinkers: A Guide for the Perplexed Copyright © 2009 Stanford Technology Law Review. All Rights Reserved. 5. There is no inherent meaning to the color on an fMRI brain image. ¶34 fMRI does not detect colors in the brain. fMRI images use colors of whatever segment of the rainbow the researcher prefers to signify the result of a statistical test . By convention, the brighter the color (say, yellow compared to orange) the greater the statistical significance of the differences in brain activity between two conditions. Put ano ther way, the brighter the color, the less likely it is that the differences in brain activity in that voxel or region, between two different cognitive tasks, was due to chance alone. As with any color – coded representation, accurate interpretation requires knowing exactly what each color represents in absolute terms. The researcher specifies what each color will represent, and this matters. Yellow might mean that there is only one chance in one thousand that the difference between brain activations in this voxel, between condition, is due to random chance. Or, yellow might mean that there is one chance in twenty that the difference is due to random chance. 31 6. fMRI brain images do not speak for themselves. ¶35 No fMRI brain image has automa tic, self – evident significance. Even well – designed, well – executed, properly analyzed, properly generated images must have their import, in context, interpreted. 7. Classification of an anatomical or behavioral feature of the brain as normal or abnormal is not a simple thing. ¶36 Because we have learned a great deal about the brain, from dissection, imaging, and the like, we have some confidence about what a typical brain looks like, and how a typical brain functions. But even without full anatomical scans of ev eryone on the planet, we know there is considerable variation both anatomically and functionally within some general parameters. That means that it can be (with some exceptions, such as a bullet lodged in the brain) difficult to say with precision how unco mmon a given feature or functional pattern may be, even if it appears to be atypical. Base rates for anatomical or functional conditions are often unknown. For example: suppose brain images show that a defendant has an abnormal brain feature. We often do n ot have any idea how many people with nearly identical abnormalities do not behave as the defendant did. How, then, to make a reasonable conclusion about the causal effect of the brain condition? 8. Even when an atypical feature of function is identified, understanding the meaning of that is considerably complex. ¶37 them is rarely self – evident. Determining which of those are important, and how, depends not only on the l egal context for which the images are offered, but also on expert analysis of what the images do and do not mean. For example, suppose that measurement of the fMRI – detected signal during a given cognitive task indicates that a person has less neural activi ty in a given region than does the average person. Does that mean that the person is somehow cognitively impaired in that region? Or might it alternatively indicate that the person has more expertise or experience than average, requiring less cognitive eff ort? 9. Correlation is (still) not causation. ¶38 The fact that two things vary in parallel tells us little about whether the two are necessarily causally related and, if so, which causes which. For example, suppose brain imaging reveals that 31 Consider this quote from a popular account: With PET, for example, a depressed brain will show up in cold, brain – inactive deep blues, dark purples, and hunter greens; the same brain when hypomanic however, is lit up like a Christmas tree, with vivid patches of bright reds and yellows and oranges. Never has the color and structure of science so completely captured the cold inward deadness of depression or the vibrant, active engagement of mania. K AY R EDFIELD J AMISON , A N U NQUIET M IND : A M EMOIR OF M OODS AND M ADNESS 196 (1995). Our point here is that the colors used are arbitrary, and may have been represented in this way to create precisely this impression.
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