some notes room change (as of thursday) geological sciences 135 6339 stores rd course website...
TRANSCRIPT
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?