P10 04/06/11 1 SPAN 4130 - Harry Howard - Tulane University.
-
Upload
claude-nichols -
Category
Documents
-
view
216 -
download
2
Transcript of P10 04/06/11 1 SPAN 4130 - Harry Howard - Tulane University.
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.
04/06/11
3
SP
AN
4130 - Harry H
oward - T
ulane University
EEG
Electroencephalography (EEG) is the measurement of electrical activity produced by the brain as recorded from electrodes placed on the scalp.
04/06/11S
PA
N 4130 - H
arry How
ard - Tulane U
niversity
6
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.
04/06/11S
PA
N 4130 - H
arry How
ard - Tulane U
niversity
7
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).
04/06/11
8
SP
AN
4130 - Harry H
oward - T
ulane University
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.
04/06/11
9
SP
AN
4130 - Harry H
oward - T
ulane University
ERP COMPONENTSNAMED BY THEIR POLARITY AND PEAK LATENCY (IN MS)
04/06/11
11
SP
AN
4130 - Harry H
oward - T
ulane University
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.
04/06/11
12
SP
AN
4130 - Harry H
oward - T
ulane University
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.
04/06/11S
PA
N 4130 - H
arry How
ard - Tulane U
niversity
13
NEUROCOGNITIVE MODEL OF AUDITORY SENTENCE PROCESSING
04/06/11
15
SP
AN
4130 - Harry H
oward - T
ulane University
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
04/06/11
16
SP
AN
4130 - Harry H
oward - T
ulane University
BRODMANN AREAS IN THE LEFT HEMISPHERE
04/06/11
17
SP
AN
4130 - Harry H
oward - T
ulane University
Inferior frontal gyrus (IFG) = green,
Superior temporal gyrus (STG) = red
Middle temporal gyrus (MTG) = blue
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.
04/06/11
19
SP
AN
4130 - Harry H
oward - T
ulane University
PHRASES CAN BE PUT TOGETHER TO FORM SENTENCES
Striped orange cats slept soundly. Colorless green ideas slept furiously.
04/06/11
20
SP
AN
4130 - Harry H
oward - T
ulane University
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
04/06/11
21
SP
AN
4130 - Harry H
oward - T
ulane University
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.
04/06/11
22
SP
AN
4130 - Harry H
oward - T
ulane University
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.
04/06/11
23
SP
AN
4130 - Harry H
oward - T
ulane University
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.
04/06/11
24
SP
AN
4130 - Harry H
oward - T
ulane University