1. Neuroimaging for Cognitive Research

2. Obtaining evidence from the Brain
Lesion studies (ling. aphaisiology)
Neuroimaging (CT, PET, SPECT, fMRI, EEG, MEG)
Direct manipulation
cell recordings (single and array)
electrical stimulation
neurochemical stimulation (barbiturates - Wada)

3. Imaging Approaches Functional Structural MRI fMRI SPECT X-ray PET
CT/CAT
EEG
ECG

4. Electro-Encephalograghy (EEG)
Electrical current originating in the cortical areas
Measured across scull and tissue - adjustments for physical properties - +
current

5. EEG Strengths: Weaknesses Relatively easy to administer and cheap
High temporal resolution (miliseconds)
Weaknesses
Hard to interpret (noise, artifacts)
Low spatial resolution

6. EEG signal analysis Event Related Potentials (ERP)
Electrical activity on an electrode or a group of electrodes averaged over many trials
Positive and negative peaks at different points in time from the stimulus presentation
0-150 ms - perception
ms - phonological/syntactic
ms - conceptual/semantic

7. ERP temporal resolution
From: brainvat.wordpress.com

8. ERP spatial resolution

9. ERP caveats
Signals from multiple sources (general body function unrelated to cognition)
Multiple presentations of the stimuli
Uncertainty of the signal source
Multiple “dipoles” may be responsible for the strength of signal at a given location
Source can be verified with other imaging methods (e.g., PET)

10. ERP components Three dimensional representation
Direction: Negative vs. Positive deflection
Latency: time from stimulus onset
Gross location: frontal, temporal, occipital, etc.
P1, N1, P2, N2, P3, N400, P600

11. ERP components P1 N1 P3
N400
P600 P2 N2

12. P1/N1 P1 N1 50ms – auditory, 100ms – visual General attention/arousal
Selective attention to stimulus characteristics
Stimulus discrimination

13. P2/N2 P2 – obligatory cortical potential N2
Low individual variability and high reproducibility
Stimulus classification
Sensitive to pitch and loudness (auditory) N2
Stimulus discrimination
Deviation of stimulus from expectation

14. P3 Stimulus classification and response preparation
Varies with stimulus complexity
Possibly associated with memory and attention

15. N400 Sensitive to language (not music) specific anomalies
Semantic but not syntactic processing
May reflect the degree of anticipation/preactivation
From Kutas & Hillyard 1980

16. P600
Memory and language
Old-new response (greater for old information)
Syntactic Positive Shift (Kutas and Hilliard, 1983)
Syntactic processing load due to parsing failure
Elicited with syntactic and morphosyntactic violations (agreement, phrase structure, subcategorization, syntactic ambiguity)

17. Magneto-Encephalography
Similar to EEG in some respects
Detects very weak magnetic fields resulting from electrical activity
Earth
Urban noise
Epileptic spike - 1,000
Sensory evoked response - 100
Tens of thousands of neurons firing in the same direction
Detected with Superconducting Quantum Interface Device (SQUID)
Orthogonal to EEG
Dipole source model

18. + -
current

20. MEG Strengths Weaknesses High temporal resolution
Sensitivity to magnetic interference
Hard to administer
Hard to interpret (noise, artifacts)

21. MEG and synchronous cognitive networks

22. Use Case: Study of Silent Meaning
Pylkkanen and McElree (JCN, 2007)
Semantic Compositionality
Strict/compositional version – semantics are always expressed in syntax
Alternative version – some semantic interpretations are non-compositional – independent of syntax

23. Compositional vs. Non-compositional Meaning
The author began the article
Activity (writing) is implied
“Coerced complement”
The author wrote the article
Activity is explicit
The author astonished the article
Semantically anomalous

24. Sources of Neural Response

25. Results
Anterior Medial Field response ( ms) sensitive to complement coercion
M350 component in the left temporal area is sensitive to semantic anomaly
Consistent with ERP findings for N400 component