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LA NEUROSINTAXIS11 ABR 2011 – DÍA 36Neurolingüística del español

SPAN 4270

Harry Howard

Tulane University

ORGANIZACIÓN DEL CURSO

http://www.tulane.edu/~howard/SPAN4130-Neurospan/

El curso es apto para un electivo en neurociencia.

Neurolinguistics and linguistic aphasiology está en reserva en la biblioteca.

Human Research Protection Program http://tulane.edu/asvpr/irb/index.cfm Before beginning research at Tulane University,

all research personnel must complete the CITI Training Program; this can be completed at www.citiprogram.org.

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REPASOHa sido la prueba.

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NEUROSINTAXIS

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EEG

Electroencephalography (EEG) is the measurement of electrical activity produced by the brain as recorded from electrodes placed on the scalp.

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SCALP (CUERO CABELLUDO) EEG

Scalp EEG is collected from tens to hundreds of electrodes positioned on different locations at the surface of the head.

EEG signals (in the range of millivolts) are amplified and digitalized for later processing.

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ERP (POTENCIA EVOCADA) Event-related brain potentials (ERPs) are positive

and negative voltage fluctuations (or components) in the ongoing EEG that are time-locked to the onset of a sensory, motor, or cognitive event.

ERPs reflect brain activity that is specifically related to some stimulus or other event.

This activity cannot be directly observed in the EEG the EEG is a composite of simultaneously occurring

brain activity it doesn't reflect just the activity associated with the

event of interest In other words, the "signal" (the brain response to

some event) is swamped by the "noise" (the brain activity that is unrelated to that event).

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SIGNAL AVERAGING The solution to this problem is to present not

just one instance of the event of interest, but many instances.

Epochs of brain activity, each one time-locked to the onset of an event, are then averaged together.

The "random" activity washes out during averaging, whereas the brain activity of interest - namely, what is constant over presentations of the event of interest - stays in the signal.

Through this signal-averaging procedure, it is possible to isolate the brain response that is specifically elicited in response to some event of interest.

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ERP PROCEDURE

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ERP COMPONENTSNAMED BY THEIR POLARITY AND PEAK LATENCY (IN MS)

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INVERSE SOLUTION

Ideally, one would like to identify the precise neural sources that generate the ERPs (known as the "inverse solution").

Unfortunately, the inverse solution is impossible to compute with certainty, because any given scalp distribution could, in principle, be generated by any number of source configurations within the brain.

However, researchers have developed powerful tools that provide good estimates of these neural sources, given some reasonable assumptions.

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LORETA

One such method is known as "LORETA", which provides an estimate of the current distribution throughout the entire 3-dimensional space within the brain.

An example of a LORETA solution, mapped onto a normalized brain space, is provided below.

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THE LINGUISTIC ERPSFriederici (2002)

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NEUROCOGNITIVE MODEL OF AUDITORY SENTENCE PROCESSING

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PHASES OF AUDITORY SENTENCE PROCESSING

The temporal scale along the bottom comes from ERP (and MEG) studies, which Friederici divides into three main phases, initiated by a ‘zeroth’ phase of phonological processing: N100: phase 0, phonological processing ELAN (early left anterior negativity): phase 1,

syntactic structure building N400/LAN: phase 2, establish semantic relations P600: phase 3, syntactic repair

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BRODMANN AREAS IN THE LEFT HEMISPHERE

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Inferior frontal gyrus (IFG) = green,

Superior temporal gyrus (STG) = red

Middle temporal gyrus (MTG) = blue

THE ELANEarly left anterior negativity

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INTRODUCTION

The first phase (100-300 ms) represents the time window in which the initial syntactic structure is formed on the basis of information about word category.

For instance, the insertion of a contracted preposition+article between an auxiliary verb and past participle in German, produces a significantly higher ERP amplitude during this period than the same sentence without the intrusive material Die Gans wurde (*im) gefüttert. The goose was (*in the) fed.

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PHRASES CAN BE PUT TOGETHER TO FORM SENTENCES

Striped orange cats slept soundly. Colorless green ideas slept furiously.

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SINCE THE MEANING DOESN’T MATTER, WE CAN WRITE WORD-ORDER RULES BASED ON CATEGORIES

A noun phrase (NP) consists of … ? An optional determiner followed by one or more

adjectives followed by a noun NP (Det) Adj (Adj) N

A verb phrase (VP) consists of … ? A verb followed by an adverb VP V Adv

A sentence consists of … ? A noun phrase followed by a verb phrase S NP VP

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BUT SUCH A REAL GRAMMAR IS FAIRLY COMPLEX

Perhaps too complex for direct study They can teach subjects a simplified set of

rules from a language that they do not know. But even better is to teach subjects an

artificial grammar (the syntactic analog of a nonsense word) which have easy-to-control properties.

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A REGULAR GRAMMAR

The rules S Xab X Xab X ab

How would you generate the string “ababab”?

This language is known as (ab)n. From fMRI we know that violations of this

grammar activate BA 44 and BA 6. The English grammar that we made up is

also of this type. So are the violations of German grammar.

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A CONTEXT-FREE GRAMMAR

The rules S aXb X aXb X ab

How would you generate the string “aaabbb”?

How would you generate the string “ababab”?

This language is known as anbn. From fMRI we know that violations of this

grammar activate BA 44, but not BA 6.

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EL PRÓXIMO DÍAMás neurosintaxis

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