Words in the Brain The Mental Lexicon Sydney Lamb Rice University lamb@rice

1. Words in the Brain The Mental LexiconSydney LambRice Universitylamb@rice.edu 8 November 2010 National Taiwan University

2. Information about a word • In ordinary dictionaries • an entry for each word • all the information pertaining to that word is given there • Phonological, graphic, grammatical, semantic • all together in one place • In the brain • The situation is entirely different • Each word is represented as a large network • Different kinds of information in different locations • So also each phrase that is learned as a unit

3. Why is this interesting? • Knowledge of how words are represented in the brain provides • the key to understanding linguistic structure • sheds light on how the brain works in general • Surprisingly, neuroscientists can’t tell us how the brain processes information • To ask them is like asking an electronic engineer how a computer calculates the orbit of a satellite or how a computer translates a weather report from Mandarin to English • For the latter question it is better to ask a linguist • Similarly, if you want to know how the human processes language, better to ask a neurocognitive linguist

4. Two views of the lexical entry • 1 – The compact entry (as in ordinary dictionaries) • All the information is there in one place – the lexical entry • Accessing the information • Retrieval • First, locate the information (requires searching) • Then “read” it • 2 – The distributed entry • The information is distributed among different locations • Accessing the information • Activation • Follow the connections (no search required)

5. The compact lexical entry(in an external lexicon) • Heading • Needed to locate the entry • A graphic representation • Exposition – the information – other than graphic • Phonological • Grammatical (e.g., Noun, Verb transitive) • Semantic – meanings • (also, etymological information)

6. The distributed “entry” (a functional web) • “Entry” is not the best term, since it is too closely associated with the familiar compact entry • Better: “Functional Web” (term from Pulvermüller 2002) • Kinds of information – in different parts of the web • Conceptual • Perceptual • Grammatical • Phonological • Production • Recognition • All of these are interconnected

7. Topics in this presentation Introductory neuroanatomy Functional webs Phonology in the brain Hierarchy and Cardinal Nodes Nouns and verbs

8. Topics Introductory neuroanatomy Functional webs Phonology in the brain Hierarchy and Cardinal Nodes Nouns and verbs

9. The brain Medulla oblongata – Myelencephalon Pons and Cerebellum – Metencephalon Midbrain – Mesencephalon Thalamus and hypothalamus – Diencephalon Cerebral hemispheres – Telencephalon Cerebral cortex Basal ganglia Basal forebrain nuclei Amygdaloid nucleus

10. Two hemispheres Right Left Interhemispheric fissure (a.k.a. longitudinal fissure)

11. Corpus Callosum Connects Hemispheres Corpus Callosum

12. Major Left Hemisphere landmarks CentralSulcus Sylvian fissure

13. Major landmarks and the four lobes CentralSulcus Parietal Lobe Frontal Lobe Occipital Lobe Temporal Lobe Sylvian fissure

14. Primary Areas Primary Somato- sensory Area CentralSulcus Primary Motor Area Primary Auditory Area Primary Visual Area Sylvian fissure

15. Divisions of Primary Motor and Somatic Areas Primary Somato- sensory Area Leg Primary Motor Area Trunk Arm Hand Fingers Mouth Primary Auditory Area Primary Visual Area

16. Higher level motor areas Primary Somato- sensory Area Actions per- Formed by leg Leg Actions performed by hand Trunk Arm Hand Actions performed by mouth Fingers Mouth Primary Auditory Area Primary Visual Area

17. Hierarchy in cortical development

18. Coronal Section Gray matter White matter

19. The gray matter • Color: gray • About 3 mm thick • Consists of columns of cell bodies 3 mm long • “Cortical columns” • Each column extends from top to bottom of the gray matter • Therefore, the gray matter, topologically, is a two-dimensional array of cortical columns

20. Layers of the Cortex From top to bottom, about 3 mm

21. The White Matter • Provides long-distance connections

22. Some long-distance fiber bundles(schematic)

23. Topological essence of cortical structure(known facts from neuroanatomy) The thickness of the cortex is entirely accounted for by the columns Hence, the cortex is an array of nodes A two-dimensional structure of interconnected nodes (columns) Third dimension for Internal structure of the nodes (columns) Cortico-cortical connections (white matter)

24. Dimensionality of the cortex • Two dimensions: The array of nodes • The third dimension: • The length (depth) of each column (through the six cortical layers) • The cortico-cortical connections (white matter)

25. Some things that are now well established The brain is a network Composed, ultimately, of neurons Neurons are interconnected Axons (with branches) Dendrites (with branches) Activity travels along neural pathways Cortical neurons are clustered in columns Columns come in different sizes The smallest: minicolumn – 70-110 neurons Each minicolumn acts as a unit When it becomes active all its neurons are active Locations of various kinds of “information” Visual, auditory, tactile, motor, …

26. Deductions from known facts All the information in the brain has the form of a network (the “human information system”) Therefore a person’s linguistic and conceptual system is a network (part of the information system) Every lexeme and every concept is a sub-network Term: functional web(Pulvermüller 2002)

27. Topics Introductory neuroanatomy Functional webs Phonology in the brain Hierarchy and Cardinal Nodes Nouns and verbs

28. Hypothesis I: Functional Webs A word is represented in the cortex as a functional web Spread over a wide area of cortex Includes perceptual information As well as specifically conceptual information For nominal concepts, mainly in Angular gyrus (?) For some, middle temporal gyrus (?) For some, supramarginalgyrus Plus phonological information

29. Example: The concept DOG We know what a dog looks like Visual information, in occipital lobe We know what its bark sounds like Auditory information, in temporal lobe We know what its fur feels like Somatosensory information, in parietal lobe All of the above.. constitute perceptual information are subwebs with many nodes each have to be interconnected into a larger web along with further web structure for conceptual information

30. Building a model of a functional web:First steps Each node in this diagram represents the cardinal node* of a subweb of properties For example C T M V *to be defined in a moment!

31. Add phonological recognition For example, FORK Labels for Properties: C – Conceptual M – Motor P – Phonological image T – Tactile V – Visual C T M P V These are all cardinal nodes – each is supported by a subweb The phonological image of the spoken form [fork] (in Wernicke’s area)

32. Add node in primary auditory area For example, FORK Labels for Properties: C – Conceptual M – Motor P – Phonological image PA – Primary Auditory T – Tactile V – Visual C T M P PA V Primary Auditory: the cortical structures in the primary auditory cortex that are activated when the ears receive the vibrations of the spoken form [fork]

33. Add node for phonological production For example, FORK Labels for Properties: C – Conceptual M – Motor P – Phonological image PA – Primary Auditory PP – Phonological Production T – Tactile V – Visual C T M P PP V PA Arcuate fasciculus

34. Part of the functional web for DOG(showing cardinal nodesonly) Each node shown here is the cardinal node of a subweb T M C For example, the cardinal node of the visual subweb PP P V PA

35. An activated functional web(with two subwebs partly shown) T C PP PR PA V M C – Cardinal concept node M – Memories PA – Primary auditory PP – Phonological production PR – Phonological recognition T – Tactile V – Visual Visual features

36. Ignition of a functional web from visual input T C PR Art PA V M

37. Ignition of a functional web from visual input T C PR Art PA V M

38. Ignition of a functional web from visual input T C PR Art PA V M

39. Ignition of a functional web from visual input T C PR Art PA V M

40. Ignition of a functional web from visual input T C PR Art PA V M

41. Ignition of a functional web from visual input T C PR Art PA V M

42. Ignition of a functional web from visual input T C PR Art PA V M

43. Ignition of a functional web from visual input T C PR Art PA V M

44. Ignition of a functional web from visual input T C PR Art PA V M

45. Ignition of a functional web from visual input T C PR Art PA V M

46. Ignition of a functional web from visual input T C PR Art PA V M

47. Ignition of a functional web from visual input T C PR Art PA V M

48. Ignition of a functional web from visual input T C PR Art PA V M

49. Ignition of a functional web from visual input T C PR Art PA V M

50. Speaking as a response to ignition of a web T C PR Art PA V M