Alphabet Soup II Notes

Unpacking Techniques and Areas

Techniques and areas will be unpacked via:
- Kutas & Hillyard, 1980
- Binder et al, 1995
Brain areas:
- LIFG (Left Inferior Frontal Gyrus)
- pITG (posterior Inferior Temporal Gyrus)
- aSTG (anterior Superior Temporal Gyrus)
- ELAN (Early Left Anterior Negativity)
Techniques:
- fMRI
- tDCS

EEG: Measuring Electrical Activity

Technique: EEG (Electroencephalography)
- Measures electrical activity from the surface of the scalp using a special electrode cap.
- High temporal resolution, but poor spatial resolution.
  - The brain's wiggly surface makes it difficult to accurately measure signals from the scalp.
- Analyzed using ERPs (Event-Related Potentials), which are event-locked time windows.
- Measures time-locked signal passing between electrode and a reference: areas on head but not brain
- Common Reference Points:
  - A1 and A2: Located on the mastoid process (the bump behind the ear).
  - Similar logic to heart monitoring with two electrodes.
- Refer to the 10-20 system for EEG electrode placement: https://en.wikipedia.org/wiki/10%E2%80%9320system%28EEG%29

EEG: Observing Raw Waves

Easy to observe raw EEG waves.
- Frequency: The size of the wiggles from left to right on the plot (repetitions over time).
- Amplitude: The size of the wiggles up and down on the plot (amount of signal).
- Analysis involves subtracting two sets of waves from each other.

Kutas & Hillyard (1980) Experiment

Method:
- Recorded brain activity on the scalp while participants read sentences one word at a time (RSVP reading).
- Presentation rate: 1 word per second (1 Hz).
- Compared different types of sentences varied in the last word:
  - Normal
  - Anomalous
  - Large font
Example Sentences:
- Normal: "I take my coffee with cream."
- Anomalous: "I take my coffee with dog."
- Large font: "She put on her high heeled SHOES"

Kutas & Hillyard (1980) Results: N400 Component

N400:
- A negative (upward) deflection at about 400 ms from word onset.
- Observed in weird vs. normal sentences.
  - Example: "I take my coffee with cream and dog" vs. "She spread the warm bread with socks".
- Reflects unexpected meanings.
- Graded to the degree of semantic weirdness.
- Central and parietal distribution.
- Refer to the 10-20 system for EEG electrode placement: https://en.wikipedia.org/wiki/10%E2%80%9320system%28EEG%29

Kutas & Hillyard (1980) Results: P560 Component

P560:
- A positive (downward) deflection at about 560 ms from word onset.
- Observed in large font vs. normal sentences.
  - Example: "She put on her high heeled shoes".
- Not language-specific; related to the appearance of the stimulus.
- Dissociation allows linking of N400 to language processing.
- Central and parietal distribution.
- Refer to the 10-20 system for EEG electrode placement: https://en.wikipedia.org/wiki/10%E2%80%9320system%28EEG%29

Other ERP Components

P600:
- A long-lasting late positive deflection for ungrammatical things.
- Refer to Osterhout & Holcomb, 1992.
N1/P2:
- N1: Negative deflection at about 100 ms.
- P2: Positive deflection at about 200 ms.
- Related to attention to sensory processing (hearing, vision).
LAN (Late Anterior Negativity):
- Another syntactic processing component.
- Left-sided, negative, diffuse.
- Possible averaging artifact (Tanner, 2015).
LRP (Lateralized Readiness Potential):
- Increased activation on the brain controlling the side of the body with which the participant will respond (e.g., right/left hand).
- Signal of response being prepared.

Key ERP Components to Remember

N400: Meaning component.
P600: Grammar component.

fMRI: Measuring Blood Oxygenation

Technique: fMRI (functional Magnetic Resonance Imaging)
- Measures changes in blood oxygenation (BOLD) signal.
- High spatial resolution, but poor temporal resolution (blood flows slowly).
- Analysis involves subtracting activity during tasks.
- Identifies voxels (3D pixels) in the brain that are statistically associated with task A but not task B (dissociation).

fMRI: Experimental Designs

Block design is an older experimental design used in Binder et al.
Logic:
- Subtract activity during task A from activity during task B to see what A uses but B doesn't.
- Needs to account for the hemodynamic response (how the brain uses blood).

Binder et al. (1995) Study: Participants

Participants:
- 5 participants.
- All healthy young adults.
- All strongly right-handed.
- Handedness assessed via the Edinburgh Handedness Inventory.
  - Questions like: "Which hand do you use for writing, drawing, throwing a ball, combing your hair, brushing your teeth, sweeping with a broom, etc.?"

Binder et al. (1995) Study: Procedure

Procedure:
- Participants presented with blocks of various stimuli.
  - Rest: Sitting quietly with eyes closed.
  - Tone monitoring: Raise the left index finger if they hear two high-pitched tones within a set of 3-7 high and low-pitched tones.
    - Stimuli: beep boop beep boop boop boop beep boop
  - Semantic monitoring: Raise the left index finger if an animal name is native to the USA and used for food/clothing/other purposes.
    - Stimuli: turkey, tiger
- Measured BOLD activity in MRI scanner during these various blocks of stimuli.

Binder et al. (1995) Study: Analysis

Analysis:
- Compared activity in voxels in the brain across different tasks in two 'slices' of space taken at very close periods of time to each other.
- Logic:
  - If more active in tone monitoring vs. rest, it's a sound-related area.
  - If more active in semantic monitoring vs. tone monitoring, it's a language-related area.

Binder et al. (1995) Study: Results - Tone Monitoring

Tone monitoring (vs. rest) was associated with bilateral areas of signal enhancement.
Concentrated in the superior temporal gyri (STG) and lateral frontal lobes.
Included the primary auditory cortex of the transverse temporal (Heschl's) gyri (hiding above and behind STG) and more distributed cortex on the dorsal STG and the superior temporal sulcus in BA 22 (Wernicke’s Area).
Enhancement was observed in every subject in the dorsolateral frontal cortices bilaterally.
Concentrated on the precentral and inferior frontal sulci and was approximately symmetric.

Binder et al. (1995) Study: Results - Hearing

Hearing (vs. rest) recruits a lot of temporal and frontal brain areas, including Wernicke’s area, on both sides of the brain.

Binder et al. (1995) Study: Results - Semantic Monitoring

A different pattern emerged when semantic monitoring was alternated with tone monitoring.
The bilateral STG activity observed during tone monitoring was almost entirely absent in the semantic-tone subtraction.
Large cortical regions of the left lateral frontal lobe, including parts of BA 6, 9, and 44-47, showed MRI signal enhancement that was specifically related to periods of semantic monitoring performance.
- Includes LIFG (Left Inferior Frontal Gyrus), Broca’s Area (BA 44/45), and the Precentral Gyrus.
These active areas were concentrated along the left inferior frontal and precentral sulci, spreading more inferiorly (towards the ground) and anteriorly (towards the nose) than the lateral frontal activity associated with tone monitoring.

Binder et al. (1995) Study: Results - Language

Language (vs. hearing) recruits more of the left hemisphere, in widespread areas of frontal cortex, including Broca’s area.
It appears diffuse, suggesting we use parts of our whole brains for language (not just Broca’s & Wernicke’s areas).

Take-Aways

ERPs are a good tool to show when processing happens.
- Semantic processing/integration happens within 400 ms of stimulus onset (N400).
fMRI is a good tool to show where processing happens.
- Hearing is associated with the auditory cortex & STG.
- Language is associated with LIFG and other frontal areas.