In the latest Hot Science piece, William Uttal takes on one of the most fundamental issues in cognitive neuroscience: Can cognitive functions be localized in the brain? Using the past as a guide, Uttal argues that it is critical for modern neuroscientists to re-open the entire localization debate. Uttal's goal is not to derail cognitive neuroscience, but rather alert us to the dangers implicit in asking questions at the wrong level.

Psychology has always been in search of metaphors and explanatory theories. Earlier we had to do with hydraulic, mechanical, electrical, and eventually computer models to serve as heuristics to help guide our thinking about the nature of cognition. In this century a new science - neurophysiology -- and a remarkable collection of new physiological recording tools have become available as an alternative to these older metaphors. We have gone through a series of physiological measures including, the galvanic skin response, the electroencephalograph, and the evoked brain potential, each of which promised to provide a material key to understanding mental activity. All of these methods were especially exciting for psychologists because they promised to provide a noninvasive means of correlating brain activity with mental actions. In the main, however, none of these methods has been successful in answering even the most basic questions of how the brain produces or encodes mental activity. The main reason for this failure has been the fact that these measures are asking questions as the wrong level. The ultimate basis of mental activity must be the informational state of a huge collection of neurons interacting, not en masse, but as a intricate web, a network in which the details of the intercommunicated information are salient. Measures of integrated activity such as the EEG or the EVBP simply do not assay the essence of the relationship between mind and brain.

The latest "new" methodology

Now there is another entry in the search for a metaphorical model. The availability of the PET and fMRI scanning procedures in the last decade has once again excited psychologists. Indeed, it has more than just excited them. Entire sections of experimental psychology in some of our most prestigious university departments have abandoned purely cognitive studies in favor of correlative studies of these images and behavioral tests. Furthermore, some departments have frighteningly over committed their resources to this single line of research. I believe this to be a programmatic error that is based upon an inadequate consideration of the basic assumptions and logic of the research that is emerging willy-nilly from this breathless attack on one of the most fundamental questions of psychobiology - the issue of whether or not mental processes can be localized in particular regions of the brain. It seems to me that there should be a cooling off period before we charge ahead into a research paradigm that has many unanswered questions and faces many conceptual, technical, and logical problems.

In the following paragraphs, my goal is to raise some cautions and to stimulate a bit of reflection about what is currently going on in many neuroscience laboratories. Some of the cautions are age-old ones, but some are associated with the most modern technical matters.
 

Six suggestions

First, perhaps the most difficult challenge that has to be faced by those who are comparing brain images and cognitive processes is the uncertainty involved in precisely defining the components of mental activity. Throughout the history of psychology, we have tried to define mental activity in an enormous number of different ways. Other than the antique and persisting trichotomy of "input-central-output", efforts to develop sharp definitions of mental modules have been notoriously unsuccessful. Every century defines their own mental components and few of these definitions are perpetuated into the next. A few very general terms persist - memory, emotions, percepts, etc. - but even these are fraught with lexicographic difficulties. Arguably, the mental modules that psychology currently uses are either a priori or ad hoc hypothetical constructs or are operationally defined by the experiments we use to study mental activity. At least one survey (Grafman, Partiot, and Hollnagel, 1995) goes on for seven pages listing the variety of cognitive processes that have been associated with the frontal cortex in particular! Clearly, an adequate classification of mental processes is not yet at hand.

Second, the findings that have emerged from the scanning-cognitive laboratories are not yet stable. Pulverm|ller (1999) has pointed out that the cognitive processing of word meanings has been "located" in all of the major lobes of the brain! Few studies are replicated under the same conditions, and often those that are do not support each other.

Third, there is ample evidence, especially that emerging from some of the newer event related scanning procedures that the cognitive processes are not localized but the result of widely distributed action in the brain.

Fourth, there is a host of technical uncertainties and a highly fragile logical chain between neural activity and the scanned outputs from fMRI and PET systems and even more concern about what these signals mean. Experts in the field are well aware of these difficulties, but often we psychologists take at face value some highly dubious steps in the logic. At the very least, it must be appreciated that it is a mathematical truism that any bounded field will exhibit a maximum. This means that there will always be a peak of activity someplace in, for example, a fMRI image. Correlations between behavior and cognitive activity are, therefore, guaranteed regardless of the actual biology of the situation. The emphasis on "hot spots" incorrectly directs attention away from critical changes of activity in other regions - both increases and decreases.
Fifth, The statistical and experimental design aspects of the scanning procedures are also matters of deep concern. Small shifts in criterion levels can force drastically different interpretations of data. Normalization and averaging procedures may produce spurious conclusions concerning localization. The frailty of the subtraction and double dissociation methods, and the elaborate processing necessary to see anything at all raise serious concerns about whether this new approach will fail in the same way that the older methods did to answer the most basic questions faced by cognitive neuroscience.

Finally, despite its implicit acceptance by many researchers in this field, the localization versus distribution issue remains unresolved. There is a theoretical bias toward "localization" abroad in cognitive neuroscience these days that may be totally unjustified. The entire scanning-cognition effort is based upon the assumption that mental processes or modules are actually localized in particular regions of the brain. However, there is abundant evidence that this may be a misreading of the data. The brain is a highly interconnected, redundant, and nonlinear system that is more likely to use a distributed representation scheme than a highly localized one. Localization is an easy way out for experimental design, but it may be fundamentally incorrect in principle. Not in the sense of any obsolescent idea of "mass action" but, rather, in terms of a complex network of interacting parts. There is, in this regard, a great confusion in this field over such a simple matter as the necessity versus the sufficiency of a brain region's role in a cognitive process. Experiments may quite properly show that one region of the brain is necessary to carry out some mental task, but that does not rule out the possibility that many other regions are also required for the process to occur. The "necessary" region may not be "sufficient" to encode the cognitive act. The emphasis on associating one or a few regions with some cognitive task may thus produce an illusion of localization where none, in fact, exists.

Conclusion: The Challenge

I hope that my readers will not do the field of cognitive neuroscience the disservice of dismissing this essay as just a "pessimistic" view. Given the state of the science, it may be more realistic than pessimistic. At the very least, it seems to me that we should be considering these issues rather than plunging ahead into what may be an enormous waste of resources and time. Whether, my point of view is correct or not, there is an obligation to at least consider the questions that are raised here.

In this brief opinion piece, it is not possible for me to provide the scientific citations to support the assertions that I make. A much more complete rendition of the argument against an assumption of brain localization, and, thus, the importance of a considered evaluation of what psychologists are doing in scanning laboratories is presented in my forthcoming book - The New Phrenology: The Limits of Localizing Cognitive Processes in the Brain. (MIT Press. Spring 2001)

References:
Grafman, J., Partiot, A., & Hollnagel, C. (1995). Fables in the prefrontal cortex. In Behavioral and Brain Sciences, 18, 349-358.

Pulvermüller, F. (1999). Words in the brain's language. In Behavioral and Brain Sciences, 22, 253-336.

William R. Uttal
Professor Emeritus (Psychology) University of Michigan
Professor Emeritus (Engineering) Arizona State University
On the Limits of Localization of Cognitive Processes in the Brain.

What from where and when: How cognition can learn from the brain

Frederic Dick and Kara D. Federmeier
Department of Cognitive Science, University of California, San Diego

We fully agree with Dr. Uttal that functions emerge from - rather than reside in - the brain. Perception, action, and cognition are, of course, the products of dynamic, fast-changing temporospatial patterns of neurochemically-mediated electrical activity. So, given this fact, is there a point in trying to learn something about the spatial or temporal character of cognition's neural substrates? Whereas Dr. Uttal implies that there is not, we believe that mechanism can reveal much about process and that imaging can be used to understand cognition, rather than to simply localize its erstwhile components.

Even independent of their ability to measure the brain per se, non-invasive imaging of electromagnetic (EEG/ERP/MEG) or hemodynamic (fMRI/PET) changes has provided rich dependent variables for the study of perceptual and cognitive function. For example, ERPs, a continuous measure with millisecond-level temporal resolution, allow one to examine the unfolding of every word in a sentence, from primary sensory analysis to higher-level integration with other words and real-world, long-term knowledge bases, and to determine the relative timing of the processes involved (e.g., van Petten et al. (1999)).

ERPs can be used to observe aspects of cognition difficult or impossible to tap into with traditional behavioral methods; in memory paradigms, for example, one can find effects at the time of encoding that are predictive of later retrieval success (Paller, Kutas, & Mayes, 1987). Already, this measure has provided some of the clearest evidence regarding when and how attention acts to shape perceptual and cognitive processing (Hillyard, Teder-Saelejaervi, & Muente, 1998) and about the nature of partial information transfer to the response system (Osman, Bashore, Coles, & Donchin, 1992). Similarly, fMRI (a methodology still in its infancy) has revealed that the neural resources underlying linguistic and motor skill acquisition are surprisingly dynamic, and that quantitative changes in the "same" skill can result in the recruitment of qualitatively different constellations of neural resources (Petersen, van Mier, Fiez, & Raichle, 1998). In addition, both hemodynamic and ICMS imaging of human and non-human primates have shown that motor and sensory representations change in a relatively lawful manner as a result of use, learning, and/or alterations in the bodily environment (Karni et al., 1998; Nudo, Milliken, Jenkins, & Merzenich, 1996).

Thus, such methods provide unique windows into cognition in action -- and also allow us to study the normal human brain in ways that were previously impossible without using highly invasive techniques. We can now map out an individual human's visual cortices (Sereno et al., 1995) or look at compensatory neural reorganization in special populations (Neville & Lawson (Müller et al., 1998; 1987). In fact, one lesson such data should have taught us by now is precisely how distributed - in both time and space - higher (and even in some cases " lower") perceptual and cognitive functions are. For instance, the baseline fMRI response to a word or sentence involves a truly formidable chunk of the brain, and even "basic" variables like word frequency affect the ERP in different ways at multiple time points throughout a word's processing.

What these methods reveal, in fact, is that neural solutions to cognitive problems are not always the most obvious, the most efficient, or the most "logical". In other words, the brain often does not behave the way psychologists, computer scientists, linguists, or engineers might predict based on the kind of models they are used to working with. And herein lies the real promise of these methodologies: that they do provide a bidirectional link - direct (ERPs/MEG) or via hemodynamic responses (fMRI/PET) - between cognition and brain. We need such links ... not to pinpoint the location of our favorite psychological construct, but to constrain our understanding of what those functions might even be. Function may not be mapped out neatly on the brain's surface but the brain does contain structure and that structure constrains the functions that emerge from it.

The brain's structure, shaped by evolution, biology and experience, affects what mistakes will be made, how things will break down, and how processes interact, interfere, and divide resources and labor on-line. It affects how we parse our sensory information and how we parse a sentence, and reveals to us - via imaging - that those parsings are not independent (Federmeier & Kutas, 1999). Imaging methods currently offer our best view into the functioning human brain. Thus, instead of using neuroimaging to try to validate our current theories of cognition, perhaps what we need to do is to affect a reversal of phrenology: rather than simply overlaying cognitive processes on the brain, we can use the dynamic structure of the brain to mold and refine our understanding of cognitive processing.
 

Federmeier, K. D., & Kutas, M. (1999). A rose by any other name: Long-term memory structure and sentence processing. Journal of Memory & Language, 41(4), 469-495.

Hillyard, S. A., Teder-Saelejaervi, W. A., & Muente, T. F. (1998). Temporal dynamics of early perceptual processing. Current Opinion in Neurobiology, 8(2), 202-210.

Karni, A., Meyer, G., Rey-Hipolito, C., Jezzard, P., Adams, M. M., Turner, R., & Ungerleider, L. G. (1998). The acquisition of skilled motor performance: fast and slow experience-driven changes in primary motor cortex. Proceedings of the National Academy of Sciences of the United States of America, 95(3), 861-868.

Müller, R. A., Rothermel, R. D., Behen, M. E., Muzik, O., Mangner, T. J., & Chugani, H. T. (1998). Differential patterns of language and motor reorganization following early left hemisphere lesion: a PET study. Archives of Neurology, 55(8), 1113-1119.

Neville, H. J., & Lawson, D. (1987). Attention to central and peripheral visual space in a movement detection task: III. Separation effects of auditory deprivation and acquisition of a visual language. Brain Research, 405(2), 284-294.

Nudo, R. J., Milliken, G. W., Jenkins, W. M., & Merzenich, M. M. (1996). Use-dependent alterations of movement representations in primary motor cortex of adult squirrel monkeys. Journal of Neuroscience, 16(2), 785-807.

Osman, A., Bashore, T. R., Coles, M. G., & Donchin, E. (1992). On the transmission of partial information: Inferences from movement-related brain potentials. Journal of Experimental Psychology: Human Perception & Performance, 18(1), 217-232.

Paller, K. A., Kutas, M., & Mayes, A. R. (1987). Neural correlates of encoding in an incidental learning paradigm. Electroencephalography & Clinical Neurophysiology, 67(4), 360-371.

Petersen, S. E., van Mier, H., Fiez, J. A., & Raichle, M. E. (1998). The effects of practice on the functional anatomy of task performance. Proceedings of the National Academy of Sciences of the United States of America, 95(3), 853-860.

Sereno, M. I., Dale, A. M., Reppas, J. B., Kwong, K. K., Belliveau, J. W., Brady, T. J., Rosen, B. R., & Tootell, R. B. (1995). Borders of multiple visual areas in humans revealed by functional magnetic resonance imaging. Science, 268(5212), 889-893.

Van Petten, C., Coulson, S., Rubin, S., Plante, E., & Parks, M. (1999). Time course of word identification and semantic integration in spoken language. Journal of Experimental Psychology: Learning, Memory, & Cognition, 25(2), 394-417.

Contributed by Fred Dick on September 02, 2000.

Imaging is a wonderful tool to help us in our understanding of how certain brain structures interact between and among one another during a specific task. As a tool, it can help us to understand a brain structure, in the same way that lesioning can help us to understand a brain structure's function and significance in its absence. I think that the effect and impact of certain psychotherapy methods during psychotherapy can also provide us with a window to view or perceive a brain structure's function. For example, hynotherapy imaging studies (Faymonville et al., 2000; Maquet et al., 1999; Rainville et al., 1999; Wik et al., 1999; Szechtman et al., 1998) have indicated involvement of the right anterior (mid) cingulate a/w/a areas 32 and 25. The spontaneous shift to these regions during hypnotic induction is of interest to me. I think that we need to appreciate all the tools available to us to help us in our understanding of human primate, non-human primate and non-primate animal responses. This may hopefully help us (in the future) to perfect the use of treatment modalities and to help us in planning service provision to those with emotional and mental illness.

Gail R. Berger Faymonville, ME, Laureys, S., Degueldre, C. et al. (2000): Neural mechanisms of antinociceptive effects of hypnosis. Anesthesiology, 92(5): 1257-67.

Maquet, P., Faymonville, M.E., Degueldre, C., Delfiore, G., Franck, G., et al. Functional neuroanatomy of hypnotic state. Biological Psychiatry, 45(3): 327-33.

Rainville, P., Hofbauer, R.K., Paus, T., Duncan, G.H., et al. (1999): Cerebral mechanisms of hypnotic induction and suggestion. Journal of Cognitive Neurosciences, 11(1): 110-25.

Szechtman, H., Woody, E., Bowers, K.S., Nahmaias, C. (1998): Where the imaginal appears real: a positron emission tomograpy study of auditory hallucinations. Proceedings National Academy of Sciences, USA, 95(4): 1956-60.

Wik, G., Fischer, H., Bragee, B., Finer, B., et al. (1999): Functional anatomy of hypnotic analgesia: a PET study of patients with fibromyalgia. European Journal of Pain, 3(1): 7-12.

Contributed by Gail Berger on September 06, 2000.

In contrast, it follows from the basic postulate of the theory of the organism-environment system that mental activity or consciousness will not be found in the brain, but in a system of relations including both the organism and environment, and the traditional psychological "functions" (such as sensation, perception, memory, etc.) describe only different aspects of the organization of the whole organism-environment system. This view questions the mainstream of cognitive science and neurophilosophy. The brain is not the only place (and not even the most important one) to look if we want to understand what it means to be conscious, and it is a serious conceptual confusion if we think that consciousness will be eventually "found" in the brain. The brain is an organ like the other organs of the body; there is no more "psyche" in the brain than in the heart, for example. The brain -- which can be neatly localized within the cranium only in anatomy books -- consists of a huge number of specialized living cells which are organized together over the whole body and carry out physiological, but not psychological processes.

Thus, it seems that many neuroscientists together with their supporting philosophers are simply looking for things in the place where they can never be found, and only because there happens to be such nice equipment for carrying out the measurements. Furthermore, there also seems to be a theoretical confusion in the thinking that in the near future we will be able to solve "the easy problem" (Chalmers, 1996), and describe all the events in the brain which constitute a simple perception. This day will never come if only the brain is studied, because perception is a process which cannot be limited to the brain (Gibson, 1979, Järvilehto, 1999).

In fact, neuroscientific theory is loaded with tautologies, and the value of experimental evidence for the location of consciousness in the brain is questionable. If we already from the beginning define the brain as a site where the elements for the system of consciousness may be found then it is clear that we will find these elements only in the brain. Nothing else is regarded as worth studying. However, if we take into account all possible factors which may contribute to our conscious existence then it may turn out that the processes in the brain have very little or no explanatory value, at least in respect to the content of our experience. [cut] Thus, modern brain research, [...], is faced with an impossible task when trying to find in the brain special areas for consciousness.

This attempt is something similar to the effort of trying to find "steering" by looking only at the steering wheel of the car. This doesn't mean denial of the importance of the brain or the nervous system when consciousness is studied. However, locating consciousness in the brain leads to questions which cannot be answered, because for consciousness to exist we need much more than the brain alone. Of course, if we remove the brain one loses consciousness, but the same also happens if all other parts of the body, or of the total environment (with other people) are removed. On the other hand, even large parts (e.g. one hemisphere) of the brain may be dissected without any permanent loss of consciousness. The development of the nervous system was most probably important from the point of view of the advent of consciousness in the phylogeny, but this does not mean that consciousness is located in the neurons.

(From Integrative Physiological and Behavioral Science 1998, 33: 331-338. THE THEORY OF THE ORGANISM-ENVIRONMENT SYSTEM: II. SIGNIFICANCE OF NERVOUS ACTIVITY IN THE ORGANISM-ENVIRONMENT SYSTEM)
However, what do we mean exactly when we say that a certain function has a location in space?

Let’s look at the action of an artist when he is preparing a piece of art. Where is "painting" located when the fine movements of the hand and fingers create a picture on the canvas? In the brain, in the hands, in the paintbrush, or on the canvas? If we destroy some of these elements it becomes more difficult to create this piece of art. Some of these elements may be more easily substituted than some other, but in the act of painting they all are necessary. Can we say that the process of painting is located in the part which seems to be most active or important?
No, of course not, because painting is a process which is realized as a whole organization of elements which are located in different parts of the world. This organization is realized as a totality in the painting. If some element, even a very tiny one, was missing the painting would not be the same or it would not be ready at all. Therefore, all elements are active in relation to the result of action; none of them is passively participating in the result.

If we kick a ball only one leg seems to be active, because we see its movement. However, the other one, the supportive leg, is also an active part in relation to the result of action, which we will see at once if we remove this leg. Similarly, it is one of the most common mistakes to regard as active in the study of the brain only those parts in which we may find responses or other kinds of changes with our recording methods. From the point of view of the result of action all other parts (in which seemingly nothing happens) are also active if they are prerequisites for the behavioral result. From the point of view of the whole system this is also true of all environmental parts joining in the result. Thus, if all elements together form the result how could we say that the result is located in only one element of the system!

From this it does not follow that mental activity does not exist at all in reality. [...]. Although we cannot locate "painting" in any part of the painting process and cannot determine it in any other way than through an inspection of elements participating in the organization of the action, the concrete result of this process may be seen in the ready-made painting on the canvas. "Painting" is not something "fictional" or an epiphenomenon, but real behavior which is realized in the co-operation of many concrete elements. Therefore, painting cannot be something related only to the brain or body, because all behavior is a process in which parts of the body and environment intertwine.

The basic mistake in any locating of mental functions to the parts of the brain is very simple: some part of the complicated system is equated with the whole result of the system.
If it is thought that mental functions are located in parts of the brain, this does not make brain research easier, but more difficult, because such a theory, in fact, mystifies both neural and mental activity. If a thought or consciousness is located in the brain what does it exactly mean? Is it located in the cells or between them? Or is it imply activity of the neurons? Moreover, if it is a property of the activity of neurons, do all neurons have such a property? If not, how then do the neurons which have "conscious" properties differ from other neurons? Do only certain kinds of neurons have mental activity? Such questions are practically impossible to solve with any experimental method.

Timo Jarvilehto Professor of psychology
Contributed by Timo Jarvilehto on September 15, 2000.

For example, in our research, overlapping of these approaches is based on the assumption that mind-body (neuropsychological) system has two levels of organization. Every level has both mental phenomena and their physiological basis. The first, rather simple, neuronal-reflex level has local representations of isolated informational units (primary sensory reflections, instinctive drives, responses etc.) in the nervous system on the basis of neurons, their groups and associative networks. Against, second higher level, implementing conscious and subconscious mental processes, has distributed representation of a complex holistic informational picture, based on common oscillatory activity of higher departments of a brain. Those departments form the whole wave function (of a brain) that carries a whole conscious informational picture of a world. Modular-coordinate structure and the basic mechanisms of operation of this level require distributed organization of information for implementation of higher mental functions. Those mechanisms eliminate the possibility of localization of information (image, skill etc.), that can be watched at research of reflex chains and similar systems.

The distinguishing of these levels and their mechanisms gives way for effective usage of both approaches (local and distributed). Besides, the analysis of interlevel interaction gives the basis for objective integration of these approaches in the whole research. The saving of the local approach to a particular level of organization of the system allows to use knowledge and effective architectures of models based on localization approach, and to supplement them by advanced designs based on the concept of the distributed system.

Besides, as Fred Dick remarked in his commentary, even the distributed system has local structures. In our model these simple structures (modules) implement some simple and local «sub-mental» functions and due to this participate in forming the nonlocal mental function. Therefore, even for investigation of the distributed system, the analysis of local structures and functions can give the important knowledge of mechanisms of nonlocal mental function. And these tasks make the application of ERP, fMRI and other methods very useful even in research of the distributed system.

The described overlapping of the localization and concept of the distributed system has difficulties and can call criticism (and hearing it would be interesting for us). Nevertheless, now this complex approach allows us to bypass many limitations (characteristic for each approach taken separately) and to find out new original theoretical results and architectures of computer models. Unfortunately, I did not meet in the literature any description of other researches targeted on the integration of that two approaches for multilevel analysis and simulation. Therefore as an example I can refer now only to the brief description of our research (www.nevsky.net/~sm/icp2000.htm). I will be grateful, if someone will correct me and point out other investigations combining both approaches discussed here.

Contributed by Sergey Miroshnikov on September 18, 2000.

The enthusiasm of researchers using new methods of noninvasive brain imaging is well understandable. After all, we all involved in the study of different cognitive processes want to have something more to say about their nature than, say, 'x is the state of a person/brain of a person doing x'. Prof. Uttal draws our attention to the (sad) fact that the PET, MEG or fMRI cannot be used to answer such questions at all.

Worse still, there is growing evidence that the old talk about uniquely definable cerebral centers of various mental activities is factually incorrect - consider e.g. what happened to Broca's area, once thought to be concerned with the motor aspects of speech, then assumed to be the locus of syntax (see recently Embick et al. 2000)and now supposed to be connected only with highly specific syntactic operations (Grodzinsky 2000).(Note that this does not undermine the modular approach - which finds growing support - but only, not surprisingly, a naive view of anatomically definable centers for different mental activities.) That does not mean, however, that new techniques are useless (nor does Prof. Uttal want us to think so, pace Dick & Federmeier): they may provide supportive evidence for theoretically plausible solutions and, much more importantly, there is hope (if very slight still) that they may help to FALSIFY theories (see Phillips, Pellathy & Marantz 2000; Phillips 2000 for a clear overview and interesting examples from the field of phonology; Grodzinsky 2000 and Grodzinsky & Finkel 1998 about, even more elusive, relevance of such data for syntactic theory).

It seems to be beyond doubt, however, that brain imaging will not answer questions about precise localization of mental phenomena (rather, it may show how much such phenomena are distributed and how much plasticity neuronal structures exhibit) - hence the stress on 'time' as apposed to 'place' in much current research - nor will it reveal HOW they are encoded. What should especially worry us is the degree of dependence of the ERP study on specific, theory-internal claims: the situation in which we are left with no 'hard' non-trivial facts threatens to undermine the whole enterprise. Thus, there should be more effort to obtain unequivocal results that could clearly falsify theoretical claims. Nowadays, the design of experiments and their interpretation are obviously too unstable and theory-dependent to be really reliable.

Embick, D. et al. (2000). A syntactic specialization for Broca's area. Proc. Nation. Acad. Sc. 97:11 6150-6154

Grodzinsky, Y. (2000). The neurology of syntax: Language use without Brocas area. Ms, submitted to Behavioral and Brain Sciences

Grodzinsky, Y. , Finkel, L. (1998). The neurology of empty categories: aphasics' failure to detect ungrammaticality. Journal of Cognitive Neuroscience 10.2, 281-292

Phillips, C. (2000). Levels of Representation in the Electrophysiology of Speech Perception. Ms, University of Delaware

Phillips, C., Pellathy, T., Marantz, A. (2000). Phonological Feature Representations in Auditory Cortex. Ms. University of Delaware & MIT

Jaroslaw Jakielaszek
Warsaw University
Contributed by Jaroslaw Jakielaszek on September 21, 2000.