Neuroimaging for Cognitive Research.ppt

1、Neuroimaging for Cognitive Research,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),Imaging Approaches,Str

2、uctural,Functional,X-ray,MRI,CT/CAT,fMRI,PET,SPECT,EEG,ECG,Electro-Encephalograghy (EEG),Electrical current originating in the cortical areas Measured across scull and tissue - adjustments for physical properties,current,+,-,EEG,Strengths: Relatively easy to administer and cheap High temporal resolu

3、tion (miliseconds) Weaknesses Hard to interpret (noise, artifacts) Low spatial resolution,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 stimulu

4、s presentation 0-150 ms - perception 150-350 ms - phonological/syntactic 350-600 ms - conceptual/semantic,ERP temporal resolution,From: ,ERP spatial resolution,ERP caveats,Signals from multiple sources (general body function unrelated to cognition) Multiple presentations of the stimuli Uncertainty o

5、f 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),ERP components,Three dimensional representation Direction: Negative vs. Positive deflection Latency: time from stimulus onset Gross l

6、ocation: frontal, temporal, occipital, etc. P1, N1, P2, N2, P3, N400, P600,ERP components,P1 N1,P2 N2,P3,N400,P600,P1/N1,P1 50ms auditory, 100ms visual General attention/arousal N1 Selective attention to stimulus characteristics Stimulus discrimination,P2/N2,P2 obligatory cortical potential Low indi

7、vidual variability and high reproducibility Stimulus classification Sensitive to pitch and loudness (auditory) N2 Stimulus discrimination Deviation of stimulus from expectation,P3,Stimulus classification and response preparation Varies with stimulus complexity Possibly associated with memory and att

8、ention,N400,Sensitive to language (not music) specific anomalies Semantic but not syntactic processing May reflect the degree of anticipation/preactivation,From Kutas & Hillyard 1980,P600,Memory and language Old-new response (greater for old information) Syntactic Positive Shift (Kutas and Hilliard,

9、 1983) Syntactic processing load due to parsing failure Elicited with syntactic and morphosyntactic violations (agreement, phrase structure, subcategorization, syntactic ambiguity),Magneto-Encephalography,Similar to EEG in some respects Detects very weak magnetic fields resulting from electrical act

10、ivity Earth - 1010 Urban noise - 1010 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,current,+,-,MEG,Strengths High temporal resolutio

11、n Weaknesses Sensitivity to magnetic interference Hard to administer Hard to interpret (noise, artifacts),MEG and synchronous cognitive networks,Use Case: Study of Silent Meaning,Pylkkanen and McElree (JCN, 2007) Semantic Compositionality Strict/compositional version semantics are always expressed i

12、n syntax Alternative version some semantic interpretations are non-compositional independent of syntax,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,Sources of Neural Response,Results,Anter