Some notes Room Change (as of Thursday)

Geological Sciences 135 6339 Stores Rd

Course website http://www.psych.ubc.ca/~whitney

New course outline (corrected formatting)

Missing page in Dronkers, Redfern & Knight

Questions for Thursday

Language & the Brain

Adults

Outline of Lecture Language & the brain: a history

Gall, Broca, Wernicke, Lichtheim The classical model of aphasia Problems with the classical model Neuroimaging

Focus on ERPs

Franz Joseph Gall (late 1700’s)

Phrenology: the linking of human characteristics with the relative size of skull areas

Believed the language faculty to be located in the two frontal lobes

Paul Broca (1861, 1865)

Patient “Tan” Right hemiparesis and loss of speech Comprehension okay Brain viewed at autopsy

Tan’s Brain

Paul Broca (1861, 1865)

Patient “Tan” Lesion site claimed to be in the left

frontal lobe• Broca’s area

Ignored the other damage Concluded (with 5 more similar

patients) that left frontal lobe (in right handers) that controlled the ability for speech

Broca’s Area

Third frontal convolution of the inferior frontal gyrus

Broca’s Aphasia

Carl Wernicke (1874)

2 patients with profound deficits in comprehension and fluent incomprehensible speech Lesion found in the posterior part of the

superior temporal gyrus• Posterior to primary auditory cortex

Wernicke’s Area

Posterior part of the superior temporal gyrus

Carl Wernicke (1874)

Wernicke’s area was associated with the storage of the “auditory memory for words”

A distinction is now drawn between “expressive” aphasia (Broca’s) and “receptive” aphasia (Wernicke’s)

Wernicke’s Aphasia

Wernicke-Lichtheim Model (1874)Geschwind (1970, 1985)

Explanation of aphasic syndromes

Geschwind

Conclusion from History of Aphasia

Until recently, most aphasia studies had only a weak connection to the brain. The important fact was that brain damage of some sort could produce selected loss of function (most interestingly, double dissociations). So deficit studies can provide evidence for the neural organization of language independent of any evidence for the specific localization of the damage causing the deficit.

Important Concept Double dissociation

Patient A is okay on task 1 but not on task 2 Patient B in not okay on task 1 but okay on

task 2

The lesion pattern may suggest what neural structures underlie such a dissociation

Current Status of the Model

Left dominance Involvement of Broca’s area Involvement of Wernicke’s area

Introduction to Imaging ERP: Event-related potentials MEG: Magneto-encephalography

PET: Positron Emission Topography fMRI: functional Magnetic Resonance

Imaging

Non-invasiverecording fromhuman brain(Functionalbrain imaging)

Positron emissiontomography (PET)

Functional magneticresonance imaging (fMRI)

Electro-encephalography(EEG)

Magneto-encephalography(MEG)

Excellent spatialresolution (~1-2mm)Poor temporalresolution (~1sec)

Poor spatialresolution (~1cm)Excellent temporalresolution (<1msec)

Hemodynamictechniques

Electro-magnetictechniques

Neuroimaging Methods

Techn. VariableTime

resolutionSpatial

resolutionComments

PET [15-O] water/rCBF

15sec – 1min 5mm Multiple runs

fMRI Blood oxygenation

A few sec. 2mm Many runs

ERPscalp-recorded

electric potential

1msec Very coarse Many trials

MEG Magnetic field 1 msec A few mmMany trials/ non-unique

solution

PET & fMRI vs. ERP & MEG PET & fMRI are indirect measures of

neural activity Blood flow increases as activity

increases

ERP & MEG are direct measures of neural activity The activity of groups of neurons can

be picked up directly

Focus on ERPs ERPs are measured via the online

EEG A group of neurons (that are

oriented in the same direction) give off an electromagnetic energy that can be measured at the scalp

Non-invasive

ERPs: Event-Related Potentials

This methodology makes use of EEG to measure event related electrical activity of the brain over time. Timelocking

To do this, a number of electrodes are placed at various sites on the scalp.

The 10-20 Electrode Placement System

10-20 vs 10-10 Systems

ERPs: Event-Related Potentials

Averaging across many trials and many subjects must occur before a pattern is seen. Averaging is a transformation of your

data - it will change the shape of your waveforms, flattening anything which is not time-locked to the event

EEGs and ERPs

Averaging

ERP Components Features of waveforms which are

related to experimental events or conditions

Naming of ERP Components Positive “P” Negative “N”

Look for whether negative is plotted up or down!!!

Naming of ERP Components

1st, 2nd, or 3rd: “P1”, “P2” or “P3” Precise latency: “P300”

Latency of peak or of onset Topography is important

Frontal N2, Occipital N2

Inferring Neural Activity from ERP Components

Amplitude: strength of activity Latency: timing of activity Topography: location of activity

Compare these variables across experimental conditions

2 Language Components N400 P600

The N400 (Kutas & Hillyard, 1980)

The pizza was too hot to ???

eat/drink/cry.

The N400 (Kutas & Hillyard, 1980)

Negative plotted up

The N400 (Kutas & Hillyard, 1980)

Polarity: negative Latency: 400ms Topography: Full scalp distribution

Semantic processing

The P600 (Hagoort & Brown, 1999)

The spoilt child

are/is

throwing the toy on the ground.

The P600 (Hagoort & Brown, 1999)

The boiled watering can

smokes/smoke

the telephone in the cat.

The P600 (Hagoort & Brown, 1999)

A positive deflection in the brain wave that reaches it maximum at approximately 600ms after the related event.

Affected by morpho-syntactic anomalies: The P600 is larger for ungrammatical sentences.

The P600 (Hagoort & Brown, 1999)

Polarity: positive Latency: 600ms Topography: Posterior distribution

Syntactic processing

Relation to Classical Model Can these ERP findings tell us

anything about the classical model?

N400 – Semantic processing P600 – Syntactic processing

(Left) Anterior NegativitiesLAN

Occurs within the N400 range 300-500 ms But, can be as early as 125 ms

But, more frontally distributed Usually larger over left than right The conditions that elicit this are

related to syntactic processing

LAN & the Classical Model Left frontal activations is possibly

related to processing of syntactic information in Broca’s area.

Second Language (L2) Processing & ERPs

Comparing native speakers to adult second language learners.

What are some of the possibilities?

L2 Grammatical Gender (Sabourin, 2003)

Research questions1. How do L2 speakers process

grammatical gender information?2. Is there an effect of native language

on this processing?