CONFERENCE REPORT

-1he Bran and Lognitive 3ciences Joseph E. LeDoux, PhD, Laurie Barclay, MD, and Ann Premack

The brain and cognitive sciences have, until recently, shared a common legacy. Throughout history, many of the great students of the mind, such as Sigmund Freud and William James, have been physicians, and their psychology was founded in their knowledge of brain physiology. But in the early years of this century, the focus of psychological studies turned away from both mental and neurological processes and toward the study of overt behavior. During this period, psychology acquired a rigorous methodology and emerged as an experimental science in its own right. In more recent years, however, the tides have again shifted. Interest in the relation between cognitive and brain processes is surging in both psychology and medical physiology, with many signs pointing toward interdisciplinary reunifications that could foster a basic science of man. With this vision in mind, a group of brain scientists, clinical neurologists, and cognitive psychologists met in December, 1977, at Cornell University Medical College in New York to discuss the current and future relationships between brain research and cognitive science. The conference was organized by Dr Michael Gazzaniga and sponsored by the Alfred P. Sloan Foundation. Gazzaniga and the Sloan Foundation had several specific objectives in mind. One was to consider whether brain science does in fact have something to offer to psychology, and vice versa. It was hoped that the interactions among the various scientists might at least stimulate them to consider new perspectives on their work. A greater desire, however, was that the participants would begin to define how findings from studies of brain function can be used to guide and set limiting conditions for psychological theory, and how research into cognitive processes might suggest clues to basic brain function. A related objective was to foster the belief among the various participants that although they may speak in somewhat different technical languages and think in terms of different theoretical constructs, their common concerns enjoy considerable overlap. Such a realization would initiate a first step toward a common language and theoretical base for the brain and cognitive sciences. Finally, it was hoped that the meeting would initiate

interest in interdisciplinary ventures that might ultimately lead to a better understanding of the human condition, and even to some solutions for neurological and cognitive disorders. Discussion centered around several issues, including memory and its disorders, localization of cognitive processes in the brain, normal and aphasic language, and the relation between language and higher cognitive processes. This report summarizes the issues and indicates how recent advances may point toward further understanding.

Memory and Its Disorders One of the most devastating features of the cognitive decay occurring in states of brain disease involves derangements of the capacity to store and retrieve information. Recent methodological and theoretical advances at both the experimental psychological and neuropharmacological levels offer clues to the nature of memory processes and provide models that may be useful in approaching cognitive disorders and their treatment. Moreover, there is hope that in studying memory disorders, one may gain new insights into the mechanisms of normal memory. In memory tests involving lists of objects, normal subjects tend preferentially to remember items at the beginning or end of the list, resulting in a bimodal serial position curve. This curve forms the experimental substrate for the two-stage model of memory. Murray Glanzer of New York University and other proponents of the model argue that the curve reflects two components of memory: a short-term store and a long-term store. Items at the end of the list are preferentially remembered because they are being actively carried in short-term memory. Items at the beginning of the list have undergone further processing and can be retrieved from long-term memory. Presumably, the items in the middle of the list are forgotten because they have been displaced from short-term store but are not yet registered in longterm store. Glanzer found that different experimental variables selectively affect short- and long-term memory. These differential effects reinforce the validity of dividing memory into two compartments. In applying the two-stage model to memory disor-

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ders, Glanzer points out that patients with bilateral temporal lobe lesions seem to have selective deficits in short-term memory whereas long-term memory is relatively intact. O n the other hand, patients with Alzheimer disease seem to have deficits in long-term memory. While some disagreement exists as to whether amnesia represents a deficit in registering new information or an inability to retrieve stored information, Glanzer believes that both registration and retrieval are damaged in amnesics. Full interpretation of new information requires active communication between short- and long-term storage. Michael I. Posner of the University of Oregon discussed the two-stage model of memory. He concludes that it fails to explain memory deficits in amnesia adequately. Although amnesics have severe deficits in long-term memory for most types of information, they seldom forget motor acts or perceptual skills. Accordingly, Posner suggests that many discrete “levels of processing” encode simple stimuli into memory traces. Some of the levels involved in recognizing a stimulus include: simple perception, comparison of the perception with stored information, generation of a name linked to that stored information, and semantic processing and classification. These steps need not occur in serial fashion, and formation of a memory trace at each successive level need not obliterate the preceding trace. Posner suggests that some levels of processing are compulsory in perceiving a stimulus, whereas others can be controlled by experimental conditions. Although registration of visual information is compulsory, rehearsal of learned information and generation of related information are control processes occurring only when the subject’s attention is channeled properly. Offering a hypothetical model of memory for consideration, Thomas K. Landauer of Bell Laboratories suggests that memory storage may occur randomly throughout the cortex. Landauer describes memory as a three-dimensional space containing many homogeneously distributed loci, or registers, in which data may be stored. The model is without organization in the sense that neither the place of storage nor the order of search during retrieval is influenced by the nature of the information being stored or retrieved. The locus available for new data entry at a given moment is described by the tip of an imaginary “pointer” moving slowly through the space in a threedimensional random walk. If two data entries occur near each other in time, then their corresponding storage loci will also be near each other. When stored information needs to be retrieved, a multidirectional “broadcast signal” is sent out from the pointer. The radius of this signal is probably smaller than the radius of the entire memory, and becomes progressively weaker as it spreads. Information-rich signals

may result in a larger effective search radius. If the broadcast signal encounters a storage register with the needed data as all or part of its contents, all the information in that location is returned to the pointer. Although this hypothetical memory system is structurally simple, it models many complex processes involved in memory and learning. Since a given datum can be stored in more than one place, multiple encounters with the same information lead to multiple copies of that datum at different locations. The probability of correct recall on a given trial increases with the number of different storage locations containing the needed datum, as there is a greater probability that the broadcast signal will reach at least one of these locations. Short-term forgetting of new memories occurs because as the pointer wanders away from the site of data entry, the probability that the datum will remain in the search radius decreases. If a finite number of storage registers is postulated, so that “overwriting” occurs when a new datum is entered into a previously filled register, the model also accounts for long-term forgetting. Landauer applied his model to disease states involving memory deficits. With focal brain lesions, the probability of destroying a particular memory would depend on the amount of tissue affected, not its location. Therefore, oft-repeated memories would be less likely to be affected by focal lesions since there would probably be other copies of the same memory outside the affected area. Retrograde amnesia could be explained by a suddenly displaced pointer, which would allow the subject to retrieve long-term memories but would impair retrieval of newly formed memories, as they would no longer be reached by the broadcast signal. A “stuck” pointer could account for deficits in short-term memory such as occur in Wernicke-Korsakoff disease. Presumably, a stuck pointer could not store new information without overwriting recently entered data. Most of long-term memory and immediate memory would therefore be intact, but short-term memory would be selectively impaired. David Drachman of the University of Massachusetts Medical Center pointed out that the brain comprises 14 billion neurons, with a density of approximately one trillion synapses per cubic centimeter of cortex. Interneuronal relationships are therefore so complex that they exceed the ability of a strict localizationist view to explain cognitive functions. Accordingly, Drachman turned his attention to pharmacological systems distributed throughout the cortex. To examine the role of cholinergic systems, he administered tests of memory and cognitive functions to normal subjects given cholinergic or anticholinergic drugs. Normal subjects given sco-

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polamine (anticholinergic) had difficulty storing new information; the similarity in their pattern of cognitive impairment to that in persons with aging changes or dementia suggests that those disorders may be related to decreased activity of central cholinergic systems. This difficulty was dramatically reversed by physostigmine (an antagonist to scopolamine). Similarly, he found that aged patients without known dementia performed somewhat better on cognitive tests when given physostigmine. Such observations suggest the possibility that memory disorders represent cholinergic malfunction. If so, treatment with the appropriate pharmacological agents may be possible. Localization of Cognitive Function Much work on brain and cognition has involved questions concerning the anatomical locus of psychological processes. Discussion of such questions focused on the visual functions of the temporal lobe, lateralized processes in the human brain, and new techniques for localizing function.

Visual Functions of the Temporal Lobe It is now commonly accepted that the inferior temporal cortex of primates plays a critical role in visual processing. Over the past several years, Mortimer Mishkin and his colleagues at the National Institute of Mental Health have been concerned with identifying the nature of that role as well as with uncovering the anatomical and physiological mechanisms involved. Mishkin has found that when the inferior temporal cortices are removed bilaterally in monkeys, the loss leads to an impairment of visual discrimination habits. A tentative model of the higher visual system accounts for why these removals lead to such impairments. Output from the striate cortex is distributed to a variety of regions in the prestriate cortex, each of which contains a separate representation of the visual field. Certain dimensions of the visual stimulus, such as depth, color, size, and shape, are probably analyzed here, and the outputs representing the separately analyzed dimensions converge in the inferior temporal cortex, where they are integrated. In this region, as Charles Gross and his colleagues have shown, single neurons have a large visual receptive field that always includes the fovea. Dr Mishkin and his colleague, D r Charlene Jarvis, studied these neurons in awake monkeys, using panel keys onto which were projected a variety of simple colors and patterns that the monkeys were required to discriminate. About 40% of the neurons in the inferior temporal cortex were “driven” by these stimuli; notably, every neuron had its unique profile

of effective stimuli. Some of the neurons among that 40% responded to one, and only one, of the array of stimuli that were presented. Others responded to all of them, showing no differentiation. Most neurons, however, showed at least some differentiation. Frequently, the neurons responded briskly to a given item y e t failed to respond at all to similar stimuli. In contrast to this sensitivity to stimulus differences, only rarely did neurons in the inferior temporal cortex show sensitivity to reward differences; that is, during discrimination-reversal testing, most neurons responded the same whether the stimulus was positive (rewarded) or negative (unrewarded). These unit-recording results fit the idea that inferior temporal neurons participate in coding the physical attributes of visual stimuli, perhaps by serving as integrators of prestriate outputs. Further support comes from studies showing that inferior temporal ablation drastically limits a monkey’s visual recognition ability. An operated monkey cannot remember beyond an interval of a few seconds an object it has seen once before, whereas normal monkeys can remember long lists of such objects for several hours. Mishkin considers that the inferior temporal region is primarily involved in stimulus coding, permitting both efficient perception and, subsequently, efficient recognition. He proposes that in the act of perceiving a new object, a unique constellation of prestriate outputs (representing a unique constellation of physical attributes) converges on single inferior temporal neurons. This initial activation of inferior temporal neurons, constituting a novel perception, leaves a lasting effect such that the same neurons are likely to be activated again by that same constellation of attributes (i.e., the same object) on a later occasion. This reactivation constitutes recognition; and the part of the circuit that is reactivated whenever the same stimulus is presented again may be viewed as the central representation of that stimulus. Subsequently, by virtue of the output connections of inferior temporal cortex with still other structures, the central representations of visual stimuli are used in a variety of ways, that is, in association with nonvisual (e.g., tactual, olfactory) attributes of that stimulus, with its location in space, with rewards and punishments, and so on.

Cognition and the Cerebral Hemispheres Recent years have seen a surge in experimental interest in identifying functional differences between the cerebral hemispheres in man. This problem has been extensively studied‘in normal and neurologically impaired subject populations, and both types of studies were discussed at the conference. Morris Moscovitch of the University of Toronto

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employed the levels-of-processing approach to hemisphere function. He argued that in both hemispheres, the first level of processing of sensory input consists of extracting low-level, precategorical, “sensory” or “physical” properties. This level of processing occurs equally well in both hemispheres. Further steps in processing operate selectively on this “sensory” information and classify it into higher-order, more abstract categories. Unless “sensory” information is subjected to further processing, it is lost in 100 to 200 msec if the stimulus is visual and in 2 seconds if it is acoustic. Although both hemispheres process information similarly, differences emerge at higher levels of processing. The right hemisphere is superior at processing complex visual information, whereas the left hemisphere excels at language comprehension. For example, perception and recall of music are selectively impaired when the right hemisphere is damaged, whereas perception and recall of words are selectively impaired in left hemisphere injury. However, perception of the simple acoustic features of either speech or music is affected equally by damage to either hemisphere. In one study, Moscovitch examined hemispheric asymmetry in face recognition. Normal subjects were presented with a sample face at fixation so that both hemispheres received the same initial input. Since their exposure to the stimulus was sufficiently prolonged (500 msec), subjects were thought to have access to a low-level, short-lived visual trace (icon) as well as a more stable, higher-order memory representation. After the stimulus was removed, an additional face was presented to either the right or the left visual field, and subjects were asked to indicate as quickly as possible whether it matched the initial sample. At intervals less than 100 msec after disappearance of the stimulus, both hemispheres presumably had access to the visual icon, and both hemispheres performed the match-to-sample task with equal speed and accuracy. At longer intervals, however, there was a clear left visual field-right hemisphere superiority in the matching task. Once the icon decays, the right hemisphere evidently has preferential access to the more deeply encoded, higherlevel representation of the visual memory. Moscovitch also found that degrading the icon prematurely by presenting a mask (visual noise) during the interstimulus interval led to right hemisphere superiority even at intervals of less than 100 msec. Moscovitch implies that the hemispheres perform low levels of processing equally well but that the left hemisphere excels at higher levels of verbal processing, whereas the right hemisphere is superior at analyzing complex nonverbal stimuli. Gazzaniga presented a different view concerning

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hemisphere asymmetry. As a result of his studies of split-brain patients, in whom each hemisphere can be studied independently of the contaminating effects of the other half-brain, Gazzaniga argued that hemisphere differences in nonverbal skills have been overemphasized. In addition, he challenged the popular view that lateralization involves the presence of a unique cognitive style in each hemisphere (analysis in the left, synthesis in the right). Instead, Gazzaniga prefers to deal with specific functions and concludes that the key difference between the hemispheres involves the dominance of the left hemisphere for language. In addition, Gazzaniga questioned the value of data from split-brain patients concerning the issue of whether language is normally present in the right hemisphere. All split-brain patients who can be shown to have any measurable degree of right hemisphere language are known to have a left temporal lobe disorder from early life, and the typical consequence of such damage is to reduce or eliminate the dominance of the left hemisphere for language. Sally Springer addressed the question of the role of genetic and nongenetic factors in determination of variations in direction and degree of hemispheric asymmetry for speech. Evidence suggesting the importance of genetic factors may be found in recent studies showing that children as young as 3 weeks of age have a right ear advantage, presumably reflective of left hemisphere dominance for speech, in dichotic listening tasks. There is also anatomical evidence that 90% of fetuses have a larger left hemisphere in regions important for speech and language in adults. Springer’s study of monozygotic and dizygotic right-handed twins, however, failed to find any evidence for heritability of the ear asymmetry in dichotic listening. These data suggest that variation in direction and degree of hemispheric asymmetry for speech in right-handers is nongenetic in origin. A smaller study of twin pairs discordant for handedness suggested that mirror imaging in monozygotic twins may be reflected in brain organization, thus implicating the importance of biochemical gradients in the elaboration of such asymmetries in the developing embryo. New Techniquesfor Localizing Cognitive Function Over the years, neurologists have had the opportunity to observe specific defects in psychological processes as a consequence of focal brain damage. While verification of the lesion locus was long based on either relatively crude estimates of radiographic studies or postmortem analysis, Fred Plum and Jerome B. Posner of Cornell University Medical

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College noted in two talks that recent advances have made possible accurate and rapid access to anatomical information concerning the site of damage. Of particular relevance is the computerized transaxial (CT) scan of the head and brain. This technique allows for radiological examination of neuropathology in the living patient. In addition to being a valuable aid in medical decision-making, the CT scan is proving to have tremendous value to those interested in correlating damaged structure and deranged function. One problem that arises in any discussion concerning the correlation between lesion locus and functional disorders involves the question of whether the function of the damaged tissue can be inferred from the observed disorder. Other technological advances mentioned by Plum provide solutions to such problems by allowing one to study the function of specific anatomical loci in the undamaged brain. For example, the multidetector regional blood flow technique developed in Scandinavia allows one to measure changing rates of blood flow to various parts of the cerebral cortex during various functional states. Inferences drawn from this technique are based on the assumption that changes in blood flow reflect alterations in metabolic activity of the tissue, and that metabolic activity, in turn, reflects the functional activity of the same tissue. By injecting a radioactive isotope into the circulatory system and measuring the behavior of the isotope with detectors placed on the surface of the skull, it is possible to index regional blood flow, and thus regional neural activity, during functional states in the normal human. A related method that allows for direct evaluation of regional glucose metabolism is positron emission scanning. This technique uses the CT scan principle in conjunction with radioactive compounds whose uptake reflects glucose utilization in specific brain regions. While this approach has the advantage of actually measuring regional metabolism (and presumably the physiological activity of neural tissue) instead of inferring metabolic activity from blood flow, it presently is incompletely developed and expensive to implement. Nevertheless, these new approaches to functional localization provide promising methods for future exploration of the neural substrates of cognitive functions. Normal and Aphasic Language Language, being the ultimate cognitive process, was extensively discussed. Normal and aphasic speech processes were examined within the analytical framework of psycholinguistics, and the relation between language and other cognitive processes was considered.

Psycholinguistic Analyses of Normal a n d Aphasic Speech Mechanisms Clinicians have long realized that one can divide aphasics into two groups on the basis of the anatomical distribution of their lesions. Patients with lesions in Broca’s area (third frontal convolution of the dominant hemisphere) speak effortfully and agrammatically, omitting function words and not inflecting verbs and nouns. Broca aphasics, however, can follow commands, and they give the clinical impression of intact comprehension. In contrast, patients with lesions in Wernicke’s area (posterior region of the first temporal gyrus) are characterized as paragrammatical. They speak fluently but omit nouns and inappropriately juxtapose lexical items. Alfonso Caramazza of the Johns Hopkins University has made use of this anatomical and clinical knowledge while attempting to characterize more precisely the deficit associated with anterior and posterior lesions. Broca aphasics appear to have intact comprehension, suggesting that their problem is a deficit in performance rather than in competence. In other words, it has been argued traditionally that in Broca’s aphasia, syntactical knowledge is intact, allowing good comprehension, but cannot be retrieved, resulting in production of agrammatical speech. Unsatisfied with this explanation, Caramazza gave aphasics sentence-picture matching tasks designed to test syntactical comprehension. The sentences used were either reversible or nonreversible in that the lexical items alone either allowed or did not allow additional readings if syntactical constraints were ignored. When only lexical knowledge was needed to interpret the sentences correctly, anterior aphasics matched correctly 90% of the time. However, their performance dropped to chance levels on sentences requiring syntactical processing for correct comprehension. In a thoughtful experiment involving transitionalerror-probability analysis, Caramazza demonstrated that anterior lesions selectively impair syntactical comprehension while sparing semantic processing. This experiment was based on the hypothesis that if processing of grammatical items by anterior aphasics is relatively shallow compared to their processing of lexical items, then grammatical words should leave less stable memory traces than content words. Subjects were given a sentence followed by a probe word, and were asked to name the word that followed the probe word in the sentence. Transitionalerror-probability analysis revealed that anterior aphasics were markedly different from normal subjects in that content words were much less effective at probing function words than vice versa. Accordingly, Caramazza concluded that anterior aphasics

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have a selective deficit in syntactical processing, while semantic processing and other cognitive functions are spared. Since this syntactical deficit is not modality specific but involves both speech production and comprehension, Broca’s aphasia seems to be a deficit in competence rather than in performance. Oscar S. M. Marin of Baltimore City Hospitals and the Johns Hopkins University referred to the efforts of his group to establish the heuristic value and general validity of studies of cognitive functions and language dissociations in brain-injured individuals as a means of understanding normal cognitive functions. He illustrated some of the cognitive and language dissociations studied by his group: the severe disorder of lexicon with preservation of syntax shown by some anomics; the converse preservation of lexicon with disorganization of syntax observed in agrammatism; and the surprising preservation of language instrumentalities (orthography, syntax) observed in some demented patients in whom the semantic aspect of language has been reduced to an incredible degree. With respect to agrammatism, Marin reviewed several of the persistent problems: Is it a pure performance production defect, as some authors seem to believe? Or is agrammatical production one aspect of it? In this he agreed with Caramazza that the production defect has a counterpart in defective comprehension. However, it remains to be established how parallel or interdependent the two aspects are, and even further, what the comprehension syntactical disorder consists of. He described the work of Dr Myrna Schwartz contrasting the syntactical difficulties in the comprehension of function words per se and those originated by word order. The latter, if unaided by lexical clues, is remarkably altered, while the former (i.e., interpretation of prepositions) is in general much better preserved and depends to a large extent on the semantic complexity of the relation described by the functor. In this respect, Marin comments that some agrammatics seem to be particularly hampered by functors that imply deictic relations (i.e., give versus take, t o versus from, go versus come). Discussing the compensatory strategies used by agrammatical patients, he described the results obtained by Eleanor Saffran of his group, which suggest the strong semantic factors influencing the verbal production of these patients. The levels-of-processing approach described by Posner in relation to memory can also be applied to speech comprehension and production. Specifically, language involves phonological, semantic, and syntactical levels of processing. Sheila Blumstein of Brown University discussed her research on the role of phonological processing in aphasia. Aphasics often make errors of substituting t for d, or vice versa, as

the only difference between the two sounds is that d is voiced whereas t is voiceless. In other words, the two phonemes differ in voice-onset time (VOT). When normal persons produce these two sounds, their productions fall into two distinct groups differing in VOT, and there is no overlap between the groups. Although Wernicke aphasics make phonemic errors by substituting d for t while reading, their productions fall within either the voice or the voiceless category and not in the overlap zone. O n the other hand, Broca aphasics make phonetic rather than phonemic errors. Their voiced and voiceless productions both overlap in the range where no VOT responses are found in normal persons. Blumstein suggests that phonetic errors in Broca aphasics reflect their deficit in articulatory programming of speech sounds. Phonemic errors in Wernicke aphasics indicate that they are unable to select the appropriate phoneme but can then correctly program the articulatory commands for the substituted phoneme. When normal subjects are asked to discriminate synthetic speech sounds differing in VOT, they cannot distinguish subtle differences in VOT but hear either d or t . Wernicke aphasics can discriminate between d and t as well as normal persons but cannot reliably label the different sounds as d or t . Since patients with poor auditory comprehension had normal scores on VOT perception tasks, Blumstein concludes that the deficit in speech comprehension is probably not at a phonological level. To confirm this hypothesis, she tested the ability of aphasics to make phonemic discriminations between real words and nonsense syllables. She again found no correlation between auditory comprehension and the ability to perform phonemic discriminations. The comprehension deficit in Wernicke aphasics does not result from defective phonemic hearing, but may be related to impaired linguistic encoding of speech sounds in the auditory association area. Alvin Lberman of the Haskins Laboratory postulates that speech is not processed like other sounds but is heard through a distinctive “phonetic mode.” Although speech can be understood at rates of 400 words per minute, or 30 phonemes per second, it would be impossible to perceive a string of 30 discrete sounds in one second. Therefore, man could not understand speech if each phoneme were cued by a single sound. Phonemes must be encoded such that a single acoustical cue carries information in parallel about successive phonemic segments. Phonemic perception therefore requires a special decoder, which may identify phonemes by referring incoming speech sounds to the set of neuromuscular commands normally used for articulation. In other words, the phonetic mode acts as if it understands how the vocal tract functions.

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To illustrate his point, Liberman described research in which normal subjects were presented with the sibilants followed by the syllable lit. If the interval between s and lit is less than 60 msec, normal subjects hear the sounds as “slit.” If the silent interval is longer, however, normal persons interpose a stop consonant and identify the sounds as “split.” Liberman suggested that normal persons know the silent period provides enough time for closure of the vocal tract to occur and therefore hear the silent interval as a stop consonant. This type of knowledge, utilized by the phonetic mode of speech comprehension, suggests that there is normally a close link between speech production and speech comprehension. What is the role of semantic processing in speech output? William Labov of the University of Pennsylvania described an experiment carried out by Caramazza and his colleagues that was designed to examine the relative roles of functional context and perceptual features in naming objects. Specifically, these investigators presented subjects with pictures of food containers to be designated cup, glass, or bowl depending on depth-to-width ratio, presence or absence of a handle, and type of food being poured into the container. Normal subjects and anterior aphasics were influenced in naming by both perceptual features and functional context, whereas posterior aphasics named most items inconsistently even on the basis of perceptual features. Semantic processing in naming seems to require correlation of perceptual data with stored information about the function and attributes of an object. Labov suggests that naming an object consists of performing a mental match-to-sample task. In other words, is the object the “same” as or “different” from the subject’s stored representation of what a given name represents? By analyzing the verbal productions of a girl child from age 6 months to 2 v 2 years, Labov concluded that children also perform match-to-sample tasks in naming objects. “Mama” was the name given to all members of her immediate family, whereas “cat” was what she called any round-headed animal without spots. When taken to the zoo, she called an owl “cat” but did not use the name for cheetahs, leopards, or other spotted felines. As is evident from Caramazza’s work, syntactical processing is an important component of speech comprehension in adults. How d o children acquire knowledge of syntactical processing? To elucidate this process, Labov studied the child’s attempts to form wh- questions. She perfected the ability to form questions properly over a 2X-year period, during which she produced 2,000 questions. In adult grammar, wh- questions are formed by placing the question word who, what, when, where, or why in front of a noun phrase and then inverting the verb

form from the indicative to the interrogative mood. Early questions from Labov’s subject, such as “What that?,” may have been imitated, but she eventually produced original constructions in her attempt to form questions consistent with grammatical rules. Labov concluded that children are naturally endowed with the ability to perform formal operations and can therefore use rules in acquiring natural language. Language and Cognition in the Chimpanzee How rich is the store of information that an animal can hold in memory? According to David Premack of the University of Pennsylvania, a word is not a simple association between an object and its name, but an association between the name and all the information stored concerning the object. The more elaborate the information store concerning an object, the more powerful will be the object’s name in retrieving information from memory. Premack evaluated the capacity of chimpanzees to store information about objects and then to retrieve the information with words. He tested several chimps using a match-tosample procedure involving part-whole relations. The animals were able to put together an apple and its appropriate stem, a pear with its seed, and so forth. Later, when symbols (words) were substituted for the fruit (the chimps had earlier been taught a visual language system), the animals were able to retrieve as much information in response to the words as they had previously retrieved with the actual fruits. Thus, not only can the chimp recognize the properties of a real situation-a red card on a green card-but it can also understand an abstract representation of that situation. Premack noted that he believes claims for chimp language have been heavily exaggerated. While the chimp is probably not a useful model for normal human language, it may be a model for pathological human conditions such as global aphasia and mental retardation, in which there is need for education or reeducation in the use of language. Language and Conscious Experience What is the nature of human conscious experience? This global question was tackled by Gazzaniga on the basis of his split-brain studies over the years. While it was always obvious that the mental properties of the left hemisphere, to which one could actually talk, were deserving of conscious status, the mute right hemisphere did not seem to be an equal partner on the dimension of consciousness. Recently, however, Gazzaniga and his colleagues had the opportunity to observe a patient who seemed to be separately and uniquely conscious in each hemisphere. While only the left hemisphere could talk, both hemispheres had extensive linguistic comprehension skills, and the

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right was able to express its mental content by arranging Scrabble letters to spell words. By making use of this expressive capacity, it was determined that this special mute hemisphere had a sense of self, a social sense, a sense of the future, and goals and aspirations for the future. As this is the first split-brain patient who can unequivocally be viewed as possessing a conscious right hemisphere, Gazzaniga raised the possibility that the factor distinguishing the patient’s right hemisphere from other right hemispheres might lie at the heart of human conscious experience. That factor, as noted, is the unique representation of language in this special patient’s right hemisphere. Such observations are consistent with the view that the human’s capacity for language plays a major and perhaps overwhelming role in the human’s capacity for self-awareness.

Conclusions A fruitful approach to a better understanding of the human condition involves interdisciplinary efforts of the brain sciences and cognitive sciences. Because these two disciplines ultimately seek answers to similar questions, an escalation in the amount of interaction would be mutually beneficial. Cognitive processes are a direct manifestation of brain function. Thus, cognitive science offers a rich source of information for students of the nervous system about how the brain expresses its functions. Moreover, cognitive psychologists, armed with rigorous methodological skills and an understanding of normal cognitive processes, are well suited to tackle the problems of delineating the nature of the mental deterioration produced by focal and diffuse disease of the nervous system. Clearly defining the problem is the first step in evolving a viable therapeutic approach. At the same time, the clinical neurological population provides a powerful opportunity to validate psychological theory. Observations of clinical disorders allow cognitive psychologists the opportunity to witness the normal systems in disarray, and thereby to see if these systems fall apart in ways predicted by cognitive theory.

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Efforts such as this conference on the Brain and Cognitive Sciences will strengthen the ties between the two disciplines. Furthering of this alliance will undoubtedly help to achieve a better understanding of the nature of man’s brain and may lead to medical solutions that will improve the quality of human life in the future.

The conference and this report were made possible by a grant from the Alfred P. Sloan Foundation.

Selective Bibliography 1. Blumstein SE, Cooper WE, Zurif EB, et al: The perception and production of voice-onset time in aphasia. Neuropsychologia 15:371-383, 1977 2 . Caramazza A, Zurif EB: Dissociation of algorithmic and heuristic processes in language comprehension: evidence from aphasia. Brain and Language 3:572-582, 1976 3. Gazzaniga MS, LeDoux JE: The Integrated Mind. New York, Plenum, 1978 4 . Glanzer M: Storage mechanisms in recall. Psychology of Learning and Motivation 5:129-193, 1972 5 . Landauer TK: Memory without organization: properties of a model with random storage and undirected retrieval. Cog Psycho1 7:495-531, 1975 6. LeDoux JE, Wilson DH, Gazzaniga MS: A divided mind: observations on the conscious properties of the separated hemispheres. Ann Neurol 2:417-421, 1977 7. Liberman AM, Cooper FS, Shankweiler D, et al: Perception of the speech code. Psycho1 Rev 74:431-461, 1967 8. Marin OS, Saffran CM, Schwartz MF: Dissociation of language in aphasia: implications for normal function. Ann N Y Acad Sci 280:868-884, I976 9. Mishkin M: Cortical visual areas and their interaction, in Karczman AG, Eccles JC (eds): Brain and Human Behavior. New York, Springer, 1972, p p 187-195 10. Moscovitch M: Information processing and the cerebral hemispheres, in Gazzaniga MS (ed): The Handbook of Behavioral Neurobiology, Handbook of Neuropsychology. New York, Plenum (in press) 11. Posner MI: Abstraction and the process of recognition, in Bower GH, Spence JT (eds): The Psychology of Learning and Motivation. New York, Academic, 1969, pp 43-100 12. Premack D: Mechanisms of intelligence: preconditions for language. Ann N Y Acad Sci 280:544-561, 1976

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