A neuronal model for syllable representation

BRAIN

AND

LANGUAGE

22, 167-177 (1984)

A Neuronal Model for Syllable Representation HARVEYM. SUSSMAN University

of Texas at Austin

A speculative neuronal template, equivalent to canonical syllable forms and independent of segmental representations, is offered to help account for (1) the inviolate nature of phonotactic constraints in aphasic speech output, and (2) left hemisphere specialization for speech sound access and output. The model, which attempts to relate plausible neuronal systems to linguistic function, is based on cell assemblies that are thought to develop by way of genetic predisposition and ontogenetic language experience, into configurations that can represent canonical slot positions for the consonants and vowel comprising a syllable. The syllable is assumed to be the basic organizational rhythmic unit for serial concatenation of sublexical segments. A scheme for neurological differentiation of vowels and consonants is offered. Phonotactic constraints can become “hard-wired” to help create the automaticity underlying phonological sound organization. Testable predictions are offered to substantiate the claims of the model.

The purpose of this note is to address two phonologically based neurolinguistic phenomena and to suggesta plausible neuroanatomical substrate that can account for both. Unfortunately, given our current understanding of brain organization and function, one cannot use evidence obtained at the behavioral level of language study to unequivocally constrain or motivate a specific brain-based model. Despite this obvious lack of “proof” in going from language events to underlying neuronal tissue, I believe that speculative behavioral-neural connections can serve as a useful exercise to generate research and thought. The core of the model is directly based on the production planning scheme of Shattuck-Hufnagel (1979, 1983). In her model, which was formulated to account for exchanges in speech errors, she suggests an independent “framework of serially ordered slots represented separately from the segments that will fill them” (Shattuck-Hufnagel, 1983, p. 133). The slot framework was conceptually viewed as a suprasegmental or rhythmic unit. I would like to further develop Shattuck-Hufnagel’s model Send requests for reprints to the author at: Department of Linguistics, University of Texas, Austin, TX 18112. 167 0093-934X184$3.00 Copyright 0 1984 by Academic Press, Inc. All rights of reproduction m any form reserved.

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and in so doing offer an expanded version as a parsimonious account for (1) the preservation of phonotactic constraints in aphasic output, and (2) left hemisphere specialization for speech sound access and output. Before the model is described a brief description of the two problems will be given. THE INVIOLATE

NATURE OF PHONOTACTIC

REPRESENTATIONS

Why is it, despite oftentimes extensive cortical and subcortical tissue destruction, an aphasic will not produce verbal output which violates the phonotactic constraints of his/her language? This phenomenon has been observed for a variety of cortically based language output disorders: phonemic paraphasias (Blumstein, 1973, 1978; Shewan, 1980); neologisms (Green, 1969; Kertesz & Benson, 1970; Lecours & Lhermitte, 1972; Buckingham & Kertesz, 1976;Buckingham, 1979)phonemic jargon (Brown, 1979; Perecman & Brown, 1980); thalamic logorrheic paraphasia (Mohr, 1975); and dementia (Irigaray, 1967, 1973; Whitaker, 1976; Schwartz, Marin, & Satfran, 1979). This claim is being made with an acute awareness of the inherent problems involved in making valid phonetic transcriptions of aphasic output, and in the face of occasional violations of this principle.’ The amazingly intact nature of intrasyllabic phonotactic strings represents a language output form that resists disruption from brain damage disproportionately to other language components that frequently undergo dissolution (e.g., syntax, semantics, lexical access and retrieval, reading, writing, articulator-y programming, and motor control). Why is phonotactic representation an apparent exception to neurological breakdown? LEFT HEMISPHERE

SPECIALIZATION AND OUTPUT

FOR SOUND ACCESS

Language theorists have been trying to account for left hemisphere language dominance ever since the first REA was obtained by Kimura (1961). Histological investigations (Geschwind & Levitsky, 1968; Wada, Clark, & Hamm, 1975; Galaburda, LeMay, Kemper, & Geschwind, 1978; Falzi, Perrone, & Vignolo, 1982) have found intriguing morphological differences in planum temporale and area 44 in favor of larger left hemisphere zones compared to right homologous zones. However, caution has been the rule in going from cytoarchitectonic findings to function in a cause and effect manner. Other theorists have hypothesized an inhibitory role of the left hemisphere, via the corpus callosum, to actively suppress linguistic development and function in the right hemisphere (Kinsbourne, 1975; Seines, 1974). To date, we still do not understand why language ’ 4 representative example of the incidence of violations of the integrity of phonotactic strings is the work of Blumstein (1978). She has reported that of 2802 phonological errors analyzed in aphasic speech, only 3.3% violated phonotactic constraints of English.

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output function is under the exclusive domain of the usually dominant, left hemisphere. THE SYLLABLE AS A PRIMARY CANDIDATE SPEECH PRODUCTION

FOR THE UNIT OF

The experimental search for the elusive invariant input unit underlying speech production has been and continues to be a very frustrating quest (Liberman, Cooper, Shankweiler, & Studdert-Kennedy, 1967). Despite the fact that data gathered at the phonetic-phonological level can never uniquely specify any linguistic entity as being the input unit to the neural programming operation, the syllable has received more widespread support as a potential candidate than any other linguistic construct. The syllable, despite its notorious resistance to be unambiguously defined (see Bell & Hooper, 1978), gathers support from diverse areas of linguistic inquiry. Results of phonological analysis (e.g., distributional constraints operating within the domain of the syllable; suprasegmental parameters such as stress, rhythm, and juncture being syllable bound; reduplication and deletion in child phonological development) has long found proponents of the supremacy of the syllable in segmental organization (Fudge, 1969; Moskowitz, 1970, 1971; Hooper, 1972, 1976). Recent work of Kent and Rosenbek (1982) and Kent, Netsell, and Abbs (1979) has explained the staccato, sing-song quality of apraxic and dysarthric speech as being due to dissociable, syllable-by-syllable output forms. The work of Sherzer (1976) studying linguistic games, has shown that the most prevalent and permutable unit in transfers during language-play games is the syllable. Broselow (1983a, 1983b) has summarized numerous examples illustrating how native language syllable structure constraints underlie pronunciation errors of second language forms. This wide diversity of supportive evidence guided the selection of the syllable as “the rhythmic unit” of ShattuckHufnagel’s slot framework scheme. THE SLOT-SEGMENT

MODEL OF THE SYLLABLE

The primary speculative assumption being put forth is that neuronal templates, equivalent to canonical syllable forms, can be envisioned as networks of neurons (short axon, dense dendritic processes) where each consonant and vowel position is associated with a specific cell assembly network. Segmental elements are independently represented by neuronal assemblies that eventually establish synaptic links with appropriate slots during sublexical serial ordering. If this “frame/content” mode of cerebral organization is a valid abstraction, then providing a neuronal conceptualization for this linguistic abstraction can contribute to our understanding of the rudiments of sublexical sound concatenation in speech production. There are numerous syllable structures found in the 4000 to 8000 distinct human languages spoken on earth (Ruhlen, 1975). The neuronal

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framework that I am suggesting can be universally applied to the formation of any syllable structure. Figure 1 schematically illustrates the canonical syllable form for English. Geometric and numerical configurations are completely arbitrary and only intended as a starting point for further discussion. Each cell assembly network comprising a slot forms a closed path of common excitability (or inhibition, if a given slot is not filled). Segmental elements come to fill slots by means of synaptic linkages to a given slot network. The phonemic inventory and phonotactic constraints of the target language(s) ultimately modulate and determine (1) the formation of the segmental representations, (2) the form of the slot frame, and (3) the specific linkages established between the two substrates. Development Synaptogenesis, the process by which axon terminals establish specific postsynaptic binding sites, has been described by Jacobson (1975) as guided by: (1) cytoaffinity; (2) proper timing of connections; and (3) functional efficiency. Jacobson states “axons may have a selective advantage if they arrive at the postsynaptic site first, or during a specific period of development, or if the pre- and postsynaptic cells have a physiochemical compatibility” (Jacobson, 1975, p. 113). I suggest that the language specific sound and syllable structures comprising the acoustic experience of the child during the critical years of language development form the input perturbation guiding the synaptogenesis of these slotsegment representations. The combination of (1) the specific external auditory stimulation, (2) the auditory self-stimulation from productive experience, and (3) the internal criteria establish the organizational rudiments of phonological development. The internal criteria are viewed as being controlled by a genetic predisposition for neuronal systems in language cortex to develop into slot frameworks incorporating target

CANONICAL

SYLLABLE

FRAME

FIG. 1. Schematic representation of the structural assumptions of the syllable slot/ segment conceptualization. The canonical syllable structure and consonantal phoneme inventory for English is used as an example.

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language syllabic structure and, simultaneously. independent segmental representations to become interactively linked with these neuronal slot frames. The crucial role of sensory experience in modulating emerging cellular development and function has been well documented in visual (Wiesel & Hubel, 1965: Blakemore & Van Sluyter, 1974; 1975; Banks, 1983) and auditory (Tees, 1967; Webster & Webster. 1977; Silverman & Clopton, 1977; Clopton & Silverman. 1978; Donaldson. 1891, 1892)primary cortex. The neurobiological development of cognitive systems, such as language in association cortex, are dependent on the sclme forms of sensory input. and as such, cannot be expected to significantly differ from these documented effects in both animal and human primary cortex. Perhaps in language development the innate framework could be the formation of canonical syllable networks. and the variable components arc the specific form of the syllable frame (CV, CVC. etc.) together with the phonemic inventory of the target language. The slot-segment model is congruent with the basic principles of child language acquisition: the near universality of initial CV preferences, the sensitivity of children to the number of syllables in adult words and their attempts to match them, the gradual emergence of increasingly complex syllabic forms, unstressed syllable deletions. consonant cluster reductions, reduplication, the development of disyllabic followed by trisyllabic concatenations, differential development of phonetic contrasts dependent on syllable position. the interactive. yet independent acquisition of new segmental elements together with increasingly complex syllabic forms (Ingram, 1978). The general developmental pattern from simple to complex (with abundant individual preferences) is theoretically consistent with a cell construct gradually branching into more complex configurations and eliminating nonfunctional connections. Consonants and vowels are different kinds of linguistic entities and seem to be under different motoric constraints (Perkell, 1969; Kozhevnikov & Chistovich, 1965; Ohman, 1966. 1967; Fowler, 1980). Unquestionably. the vowel holds a unique position within the syllable. Concepts such as “sonority peak” and vowel adherence have been invoked to describe the elusive essence of the syllable itself (Jespersen. 1926: Sigurd. 1965; Hooper, 1976). It has long been noted that vowels also seem to be more resistant to loss or misordering in speech errors (Blumstein, 1973). The differences that exist between vowels and consonants, both phonetic and phonological, should be reflected in differences at the level of the underlying neuronal substrates. The slot-segment model can suggest a number of alternative schemes to account for this segmental differentiation. One view is that the syllabic

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frame may contain the vowel as an intrinsic part of the frame itself. In other words, the vowel can come “prepackaged” with the selection of the frame. Canonical syllable frames can develop at the same time as vowel elements are developing, and the latter may become incorporated into the nucleus slot. Thus, syllable frame selection would be guided by the vowel needed per syllable. Vowel information can also be viewed as a place holder for the syllable wherein stress and duration information are first programmed. Another alternative to the “prepackaging” notion of the vowel is independent specification of the vowel and the syllable, but both occurring at a level prior to consonant specification.2 Some Operational Features of the Slot-Segment Scheme The operation of the slot-segment model is envisioned to take place at a premotor stage following (and most likely driven by) lexical selection. How the lexicon determines the specific sublexical serial ordering is still unknown and hence unspecified. The selection of syllable frames for eventual production are guided by the lexical targets and can be initially selected on the basis of the needed vocalic nucleus. Since all canonical slot frames are identical at this point in production, they are only contrasted by the vowel contained within. Slots are then “primed” or “nulled” depending on the specific syllable structure called for. It is at this point that phonotactic constraints can operate to reduce the “degrees of freedom” in segmental selection for slot occupancy. For example, in C,C2C3 prevocalic clusters /s/ is the only segment that can fill the C, slot3; the C2 slot is then limited to only voiceless stop /p,t,k/ segments; and the C3 slot limited to liquid/glide segmental selection. Similarly, place assimilation in postvocalic clusters reduces the number of choices for slot occupancy as well as what consonants can follow tense and lax vowels. Ontogenetic language experience can universally establish a quasi-automaticity in the serial ordering of consonant strings that of necessity obey phonotactic rules. In laying down these synaptic linkages of segments to slot positions the phonological operations of language production become “tightly wired” (Schwartz et al., 1979, p. 303) or “automatized” (Whitaker, 1983).4 ’ My thanks to Ray Kent who provided helpful suggestions related to this vowel representation issue. ’ Serially ordered phonemes within a syllable need not be envisioned as occupying adjacent slots. A given phoneme such as ls/, with specific phonotactic constraints, can be hard-wired to a fixed prevocalic consonant slot such as C,. If a lexical target item contains /s/ in prevocalic position, it-regardless of whether it is the initial member of a triple, double, or singleton cluster, the is/ can always be realized from a synaptic linkage to C,. C, or C, slots that are not needed (in sV-- forms) are simply nulled and the vowel can automatically follow the /s/. This type of hard-wired automaticity can reduce the necessary phonemic degrees of freedom. ’ Of considerable interest is the lessening of constraints, and hence degree of “automaticity” in sequencing postvocalic strings compared to prevocalic strings (e.g., “ask/ax”).

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Phonotactic Stability Within language cortex mediating the phonological-to-phonetic stage of production the neuronal substrates for the syllable frame and segmental representations may be redundantly overrepresented. In damaged tissue, residual populations of syllabic-frame networks, complete with their synaptic paths to segments, can mediate the correct syllable fragments that characterize the paraphasicjjargon output of aphasic speech. A severity continuum, ranging from literal paraphasic errors to phonemic jargon can be related to the integrity of these substrates within and around the loci of brain damage. The redundancy argument is admittedly not very elegant, but it does serve as a preliminary explanation for the inviolate nature of this language component. It would take total and widespread tissue death to fully eliminate this sublexical organizational substrate from operation during speech output. Impermissible consonant strings do not get produced in normal or damaged neural systems because the underlying wiring does not exist; they were never heard, never spoken, and never developed. Analogous constraints operate at the syntactic level as new closed class functors do not appear in language use, while new open class lexical items are constantly being created. Similarly, speakers experience great difficulty in “creating” a new vowel sound to occupy acoustic space in between two existing vowels. Left Hemisphere Specialization for Sound Access and Output What if the hypothesized neuronal networks underlying the formation and concatenation of syllables only developed in the left hemisphere? The known cytoarchitectonic asymmetries found in the brain reflect morphological differences possibly related to language lateralization. Anatomical asymmetry is present at the cellular level as seen in the work of Seldon (1981a, 1981b) who found larger diameters of columnar cell clusters and greater intercolumnar distances in left versus right human auditory cortex. Perhaps a major contributory factor underlying left language dominance is the exclusive presence of syllable frames and their privileged access to segmental entities in the left hemisphere. This notion unites morphology to function in a very specific fashion. A hemisphere devoid of such organizational substrates should not be expected to program language sound output. Such a hemisphere should only be expected to function on a holistic basis with primary dependence on semantic-lexical components of language. Without access to syllable frames containing a vowel nucleus, a hemisphere should be unable to rhyme. Levy (1972) and Zaidel (1981) found commissurotomy patients unable to indicate words/objects that rhyme with stimuli presented in the left visual field. Right hemispheres simply cannot access or evoke the sound image of an internally stored representation of a vowel for independent manipulation

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and processing. The right hemisphere can successfully read and identify common nouns because it apparently has access to lexical content words. The right hemisphere cannot access the critical substrates that form the premotor stage of production by concatenation of sequential sound segments within a “building block” framework. TESTABLE PREDICTIONS If phonological development is predicated on the establishment of neuronal correlates for both canonical syllables and independent, but synaptically interactive, phonemic segments of the ambient language(s), then one should expect to find the following: (1) children acquiring simple syllabic forms (e.g., Hawaiian, CV) should develop a more adult-like phonological system earlier, and perhaps easier, than children whose native language consists of very complex syllable forms (e.g., Pame, an Indian language with CCCCVCCCCC syllables); (2) children acquiring native languages possessing relatively small phonemic inventories (e.g., Hawaiian) should approach mature adult forms earlier, and perhaps easier, than children learning more complex systems (e.g., Kartvelian); (3) children who are simultaneously acquiring two languages in a balanced bilingual environment should experience greater difficulty if the two languages are maximally contrastive in phonological organization (especially syllable structure and distributional constraints) compared to two languages sharing similar phonological systems. Of considerable interest in regard to the maturational pattern of phonological development vis-a-vis neuronal development is the apparent paradox between the two. Whitaker, Bub, and Leventer (1981), reviewing the literture on brain maturation have reported that, conservatively speaking, by the age of 6 years the child’s brain has reached 90% of adult values. An empirical resolution of this paradox will not be possible until better criteria become available with which to assessbrain maturation on a functional basis. The types of variables that have been used to date (e.g., cellular packing density, neuron volume, brain weight, myelination) are obviously not specific enough to relate in any meaningful way to underlying maturation of language development. The critical refinement of synaptic connectivities that subserve language development proceed throughout the first decade or so of life and cannot be expected to be detected by volume/density measures. Note added in proof. Shortly after submission of this manuscript I became aware of the recent and elegant histological work of Scheibel and his colleagues (Scheibel, A. P. Differentiating Characteristics of the speech area of the human cortex. Paper presented at the symposium “The Dual Brain: Hemispheric Specialization in the Human,” held January 19-21, 1984, by the Department of Continuing Education in Health Sciences, UCLA Extension and the School of Medicine, UCLA). This research group has systematically analyzed adult frontal language cortex in both hemispheres. Their initial efforts have focalized on the basilar dendritic structure of pyramidal neurons (Golgi I type) found in

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layer III of frontal opercula cortex (corresponding to Broca’s area on the left). While total dendritic length (TDL) was found to be equivalent in right and left cortex, statistically robust differences were noted when the composition of TDL was examined. Specifically, the greatest proportion of TDL in right frontal opercula was comprised of lower order branches (1st + 2nd + 3rd), whereas in left language cortex, the greatest proportion of TDL was made up of higher order branchings (4th + 5th + 6th). The same histological analysis carried out on pyramidal cells comprising precentral cortex (orofacial motor zone) failed to reveal this lateralized differentiation in dendritic arborization. As pointed out by Scheibel, the higher order branches of dendritic processes, being thinner and further away from the soma, represent later stages of growth and maturation compared to the thicker lower order branchings. Could Scheibel’s discovery be related to the long sought-after neurobiological correlate of the “critical maturation period” for language acquisition? Longitudinal analyses in infants and children are currently planned by Scheibel to document the growth of the dendritic arborizations vis-a-vis the age of the child (and hence indirectly the stage of language acquisition reached). It is not unreasonable, in light of Scheibel’s recent findings, to hypothesize that similarly emerging neuronal-dendritic-synaptic growth patterns, lateralized to the language dominant hemisphere, can underlie the functional realization of the syllabic/segmental structure of sound systems called language.

REFERENCES Banks, M. S. 1983. Visual perception. In M. Haith & J. Campos (Eds.), Biolngy and infancy handbook of child psychology. New York: Wiley. Bell, A., & Hooper, J. B. 1978. Syllables and segmenrs. Amsterdam: North-Holland. Blakemore, C., & Van Sluyters, R. C. 1974. Reversal of the physiological effects of monocular deprivation in kittens: Further evidence for a sensitive period. Journal of Physiology, 231, 195-216. Blakemore, C., & Van Sluyters, R. C. 1975. Innate and environmental factors in the development of the kitten’s visual cortex. Journal of Physiology, 248, 663-716. Blumstein, S. E. 1973. A phonological investigation of aphasic speech. The Hague: Mouton. Blumstein, S. 1978. Segment structure and the syllable in aphasia. In A. Bell & J. B. Hooper (Eds.), Syllables and segments. Amsterdam: North-Holland. Broselow, E. 1983. Non-obvious transfer: On predicting epenthesis errors. In S. Gass & L. Selinker (Eds.), Language transfer in language learning. Rowley, MA: Newbury House. (a) Broselow, E. 1983. An investigation of transfer in second language phonology. In press: International Review of Applied Linguistisics. (b) Brown, J. W. 1979. Language representation in the brain. In H. Steklis & M. Raleigh (Eds.), Neurobiology of social communication in primates: An evolurionaty perspective. New York: Academic Press. Buckingham, H. W., & Kertesz, A. 1976. Neologistic jargon aphasia. Amsterdam: Swets and Zeitlinger. Buckingham, H. W. 1979. Linguistic aspects of lexical retrieval disturbances in the posterior fluent aphasias. In H. Whitaker & H. A. Whitaker (Eds.), Studies in neurolinguisrics. New York: Academic Press. Vol. 4. Clopton, B. M., & Silverman, M. S. 1978. Changes in latency and duration of neural responding following developmental auditory deprivation. Experimental Brain Reseurch, 32, 39-47. Donaldson, H. H. 1891, 1892. Anatomical observations on the brain and several sense organs of the blind deaf mute, Laura Dewey Bridgeman. American Journal of Psychology, 3, 293-342; 4, 248-294.

Falzi, G., Perrone, P., & Vignolo, L. A. 1982. Right-left asymmetry in anterior speech region. Archives of Neurology, 39, 239-241.

176

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Fowler, C. A. 1980. Coarticulation and theories of extrinsic timing. Journal ofphonerics, 8, 113-133. Fudge, E. C. 1969. Syllables. Journal of Linguistics, 5, 253-286. Galaburda, A. M., LeMay, M., Kemper, T. L., & Geschwind, N. 1978.Right-left asymmetries in the brain. Science, 199, 852-856. Geschwind, N., & Levitsky, W. 1968. Human brain: Left-right asymmetries in temporal speech region. Science, 161, 186-187. Green, E. 1969. Phonological and grammatical aspects of jargon in an aphasic patient: A case study. Language and Speech, 12, 103-118. Hooper, J. B. 1972. The syllable in phonological theory. Language, 28, 525-540. Hooper, J. B. 1976.An introduction to natural generative phonology. New York: Academic Press. Ingram, D. 1978. The role of the syllable in phonological development. In A. Bell & J. B. Hooper (Eds.), Syllables and segmenrs. Amsterdam: North-Holland. Irigaray, L. 1967. Approache psycho-liguistique du Iangage des dement. Neuropsychologia, 5, 25-52. Irigaray, L. 1973. Le langage des demerits. The Hague: Mouton. Jacobson, M. 1975. Brain development in relation to language. In E. H. Lenneberg & E. Lenneberg (Eds.), Foundations of language development. New York: Academic Press. Jespersen, 0. 1926. Lehrbuch der phonerik. Leipzig/Berlin: Teubner. Kent, R. D., Netsell, R., & Abbs, J. 1979. Acoustic characteristics of dysarthria associated with cerebellar disease. Journal of Speech and Hearing Research, 22, 627-648. Kent, R. D., & Rosenbek, J. C. 1982. Prosodic disturbance and neurologic lesion. Bruin and Language, 15, 259-291. Kertesz, A., & Benson, D. 1970. Neologistic jargon: A clinicopathological study. Cortex, 6, 362-386. Kimura, D. 1961. Some effects of temporal lobe damage on auditory perception. Canadian Journal of Psychology, 15, 156-165. Kinsbourne, M. 1975. Minor hemisphere language and cerebral maturation. In E. H. Lenneberg & E. Lenneberg (Eds.), Foundations of language development. New York: Academic Press. Kozhevnikov, V. A., & Chistovich, L. A. 1965. Rech’ nrtikuliatsia i vospriiatie, MoscowLeningrad. Transl. Speech: articulation and perception. Washington, D.C.: Joint Publication Research Service. Lecours, A. R., & Lhermitte, F. 1972. Recherches sur le language des aphasiques: Analyse d’un corpus de neologismes; notion de paraphasie monetique. Encephale, 61, 295315.

Levy, J. 1972. Lateral specialization of the human brain: Behavioral manifestations and possible evolutionary basis. In Proceedings of the 32nd Annual Biology Colloquium on the Biology of Behaviors. J. A. Kiger (Ed.). Corvallis: Oregon State Univ. Press. Liberman, A., Cooper, F. S., Shankweiler, D. P., & Studdert-Kennedy, M. 1967.Perception of the speech code. Psychological Review, 74, 431-461. Mohr, J. P. 1975. Thalamic hemorrhage and aphasia. Brain and Language, 2, 3-17. Moskowitz, A. 1970. The acquisition of phonology. Working Paper, 34. Berkeley: LanguageBehavior Research Laboratory, University of California. Moskowitz, A. 1971.The acquisition ofphonology. Unpublished Ph.D. dissertation, University of California, Berkeley. Ohman, S. E. G. 1966. Coarticulation in VCV utterances: Spectrographic measurements. Journal of Acoustical Society of America, 39, 151-168. Ohman, S. E. G. 1%7. Peripheral motor commands in labial articulation. Quarterly progress and status report, 4, 30-63. Stockholm, Sweden: Speech Transmission Laboratory, Royal Institute of Technology.

NEURONAL

MODEL FOR SYLLABLE

REPRESENTATION

177

Perecman, E., & Brown, .I. W. 1980. Phonemic jargon: A case report. In J. W. Brown (Ed.), Jargon aphasia. New York: Academic Press. Perkell, J. S. 1969.Physiology of speech production: Results and implications of a quantitative cineradiographic study. (Research monograph, No. 53). Cambridge, MA: MIT Press. Ruhlen, M. 1975. A guide to the languages of the world, language universals project. Stanford, CA: Stanford University Press. Schwartz, M. F., Marin, 0. S. M., & Saffran, E. M. 1979. Dissociations of language function in dementia: A case study. Brain and Language, 7, 277-306. Seldon, H. L. 1981a. Structure of human auditory cortex. I. Cytoarchitectonics and dendritic distributions. Brain Research, 229, 277-294. Seldon, H. L. 1981b. Structure of human auditory cortex. II. Axon distributions and morphological correlates of speech perception. Bruin Research, 229, 295-310. Seines, 0. A. 1974. The corpus callosum: Some anatomical and functional considerations with special reference to language. Bruin and Language, 1, 111-139. Shattuck-Hufnagel, S. 1979. Speech errors as evidence for a serial order mechanism in sentence production. In W. E. Cooper & E. C. T. Walker (Eds.), Sentence processing. Hillsdale, NJ: Erlbaum. Shattuck-Hufnagel, S. 1983. Sublexical units and suprasegmental structure in speech production planning. In P. F. MacNeilage (Ed.), The production af speech. New York: Springer-Verlag. Sherzer, J. 1976. Play languages: Implications for (socio-) linguistics. Speech play, B. Kirshenblatt-Gimblett, (Ed.), Philadelphia: Univ. Pennsylvania Press. Pp. 19-36. Shewan, C. M. 1980. Phonological processing in broca’s aphasics. Bruin and Language, 10, 71-88. Sigurd, B. 1965. Phonotactic structures. Lund: Berlingska. Silverman, M. S., & Clopton, B. M. 1977. Plasticity of binaural interaction. I. Effect of early auditory deprivation. Journal of Neurophysiology, 40, 1266-1274. Tees, R. C. 1967.Effects of early auditory restriction in the rat on adult pattern discrimination. Journal

of Comparative

Physiology,

63, 389-393.

Wada, J. A., Clark, R., & Hamm, A. 1975. Cerebral hemispheric asymmetry in humans: Cortical speech zones in 100 adult and 100 infant brains. Archives of Neurology, 32, 239-246. Webster, D. B., & Webster, M. 1977. Neonatal sound deprivation affects brain stem auditory nuclei. Otolaryngology, 103, 392-396. Whitaker, H. 1976. A case of isolation of the language function. In H. Whitaker & H. A. Whitaker (Eds.), Studies in Neurolinguistics. New York: Academic Press. Vol. 2. Whitaker, H. A. 1983. Towards a brain model of automatization: A short essay. In R. A. Magi11 (Ed.), Memory and control of action. Amsterdam: North-Holland. Whitaker, H. A., Bub, D., & Leventer, S. 1981. Neurolinguistic aspects of language acquisition and bilingualism. In H. Winitz (Ed.), Native language and foreign language acquisition. Annals of the New York Academy of Science, 379, 59-74. Wiesel, T. N., & Hubel, D. H. 1965. Comparison of the effects of unilateral and bilateral eye closure on cortical unit response in kittens. Journal of Neurophysio/ogy, 28, 10201040.

Zaidel, E. 1981. Phonological encoding and ideographic reading by the disconnected right hemisphere: Two case studies. Bruin and Language, 14, 205-234.