On the Neurocognitive Basis of Syntax

Sydney Lamb

lamb@rice.edu

2010 November 12

Wenzao Ursuline College of LanguagesKaohsiung, Taiwan

Why is it important to consider the brain?

“I gather…that the status of linguistic theories continues to be a difficult problem. … I would wish, cautiously, to make the suggestion, that perhaps a further touchstone may be added: to what esxtent does the throry tie in with other, non-linguistic information, for example, the anatomical aspects of language? In the end such bridges link a theory to the broader body of scientific knowledge.”

Norman Geschwind “The development of the brain and the evolution of language” Georgetown Round Table on Languages and Linguistics, 1964

The two big problems of neurosyntaxHow does the brain handle..

1. Sequencing – ordering of words in a sentence– And ordering of phonemes in a word

2. Categories– Noun, Verb, Preposition, etc.

• Subtypes of nouns, verbs, etc.– What categories are actually used in syntax?– How are syntactic categories defined?– How represented in the brain?– How does a child build up knowledge of such categories

based on just his/her ordinary language experience?

First step: accounting for sequence

• Important not just for language– Dancing– Eating a meal– Events of the day, of the year, etc.– Etc., etc.

• In language, not just syntax (lexotactics)– Ordering of morphemes in a word

• Morphotactics – Ordering of phonological elements in syllables

• Phonotactics – Ordering of sememes in a thought

Neurological Structures for Sequence

• How is sequencing implemented in neural structure?

• For an answer, consider the structure of the cortical column

Lasting activation in minicolumn

Subcorticallocations

Connections to neighboring columns not shown

Cell Types

Pyramidal

Spiny Stellate

Inhibitory

Recurrent axon branches keep activation alive in the column –Until is is turned off by inhibitory cell

The ‘Wait’ Element

W

1

2

www.ruf.rice.edu/~lngbrain/neel

Lasting activation in minicolumn

Subcorticallocations

Connections to neighboring columns not shown

Cell Types

Pyramidal

Spiny Stellate

Inhibitory

Recurrent axon branches keep activation alive in the column –Until is is turned off by inhibitory cell

Simple notation for lasting activation

Thick border for a node that stays active for a relatively long time Thin border for a node

that stays active for a relatively short time

N.B.: Nodes are implemented as cortical columns

Recognizing items in sequence

This link stays active

a b

Node c is satisfied by activation from both a and b If satisfied it sends activation to output connections Node a keeps itself active for a whileSuppose that node b is activated after node a Then c will recognize the sequence ab

c

This node recognizes the sequence ab

Example: eat apple(structure for recognition)

eat apple

eat apple

(Just labels, not part of the structure)

Example: eat apple, eat banana(structure for recognition)

eat apple eat banana

eat apple banana

Producing items in sequence

ab

a b

Wait element

First a, then b

How does the delay element work?

• Remember: each node is implemented as a cortical column– Within the column are 75-110 neurons

• Enough for considerable internal structure• When node ab receives activation, it

– Sends activation on down to node a– And to the delay element, which

• Waits for activation from clock timer or feedback– Will come in on line labeled ‘f’ in diagram

• Upon receiving this signal, sends activation on to node b

Producing items in sequence

ab

a b

Delay element

Carries feedback or clock signal

f

Producing items in sequence

ab

a b

May be within one cortical column

f

Producing items in sequencea different means

a b

f

This would apply for items ‘a’ and ‘b’ in sequence where there is no ‘ab’ to be recognized as a unit.Example: Adjectives of size precede adjectives of color, which precede adjectives of material in the English noun phrase, as in big brown wooden box

Two different network notations

Narrow notation• Nodes represent cortical columns• Links represent neural fibers• Uni-directional• Close to neurological structure

Abstract notation• Nodes show type of relationship (OR,

AND)• Easier for representing linguistic

relationships• Bidirectional • Not as close to neurological structure

eat apple

eat apple

eat apple

eat apple

Two different network notationsNarrow notation

ab

a b

b

a b

Abstract notation Bidirectional

ab

a b f

Upward Downward

Constructions have meanings and functions

• They are also signs

Meaning/Function

Form/Expression

The sign relationship: a (neural) connection

The difference is that for a construction the expression is variable rather than fixed

The transitive verb phrase construction

CLAUSE DO-TO-SMTHG

Vt NP

Transitive verb phrase

Syntactic function

Semantic function

Variable expression

Linked constructions

CL

NP

DO-TO-SMTHG

Vt NP

Transitive verb phrase

The clause construction

Add a few more connections

CL

NP

DO-TO-SMTHG

Vt

Transitive verb phrase

ACTOR-DO

Add other types of predicate

CL

DO-TO-SMTHG

THING-DESCR

BE-SMTHG

be

NP

Vt

Adj

Vi

Loc

(A rough first approximation)

The other big problem for syntax

• Categories• Problems of categories are considered in a separate

presentation– “Categories in the Brain”

• Lexotactics uses very broad categories– We can say, e.g., “tried to eat a truck”

• For narrower categories, Semotactics– So the prototypical goals of EAT are edible objects