- Attributes of each trial:
- [iArtifacts]: if the current trial is considered as a "bad" trial due to artifacts, ∈ (0: good trial; 1: bad)
- [iTrialType]: trial type {1,2,3,4,-1}
- [iInstructionLength]: length of the instruction period, ∈(100:1000 ms), source: presentation log 5xxx.
- [iOffIndex]: the block index number for current trials's light off in eegData02, ∈(1:191)
- [iOffOffset]: the offset index number for current trials's light off in each block in eegData02, ∈ (1:12500)
- [iOnIndex]: the block index number for current trials's light on in eegData02, ∈(1:191)
- [iOnOffset]: the offset index number for current trials's light on in each block in eegData02, ∈ (1:12500)
- Attributes with respect to the raw markers (markerData(1, x).trial & time)
- [lightOnTimeClean]: clean events of light on events (with double trigger events manually removed)
- [lightOnCleanIndex]: index of clean events in the originally markers -- gData.markerData(1,1).trial
- [lightOffTimeClean]: clean events of light off events (with double trigger events manually removed)
- [lightOffCleanIndex]: index of clean events in the originally markers -- gData.markerData(1,2).trial
- EEG channel working data
- [eegData02]: EEG working data. {Column 1: left&Right. Column2: up&down. Column3: info channel}
- Column3 info channel data format: [condition].[iTrialtype] e.g. 54.1 = light off for proleft, 52.3 = light on for antileft
Blog S.-H. Wang
Tuesday, December 6, 2011
data dict
Global var [scannerdata]
Sunday, December 4, 2011
MEGANTI - Preprocessing
[Presentation sce file]
In total 14 blocks, each block has 80 trials, each trial has following four events recorded in the log file:
Subjects
SW - [2010-08-11] - Old system no parallel code
raw: S02_MEG54_VEF_02.ds
stim log (raw): sw32-110810-SO2-Pro+Anti-saccade task.log
Problems in the data:
In total 14 blocks, each block has 80 trials, each trial has following four events recorded in the log file:
- [Start]: duration 1000 ms, code 0, port_code 1
- [Pro] or [Anti] initiation: LightOn, (green pro, red anti) duration 100 ms, code 54, port_code 54,
- [pro5xxx] or [anti5xxx]: randomized length, code: 5+ [100:50:1000], e.g. 5100, 5250..., port_code [101:1:117]
- [GO cue ∈ 1 | 2 | 3 | 4] : duration 20 ms, LightOff
- 1: greyboxproleft, port_code 201 -- prostim left
- 2 :greyboxproright, port_code 202 -- prostim right
- 3: greyboxantileft, port_code 203 -- antistim left
- 4: greyboxantiright, port_code 204 - -- antistim right
Subjects
SW - [2010-08-11] - Old system no parallel code
raw: S02_MEG54_VEF_02.ds
stim log (raw): sw32-110810-SO2-Pro+Anti-saccade task.log
Problems in the data:
- The stim log has 195 missing event condition, all replaced with -1.
- The lightOn marker has 130 extra double triggers - fixed (lightOnTimeClean:1121)
- The lightOff marker has 3 extra double triggers - fixed (lightOffTimeClean:1120)
- Verify by comparing the time diff between on and off with the event code, 121.40
Saturday, October 15, 2011
re: Thesis Overview
TASK RELATED NEUROMAGNETIC ACTIVITY UNDERLYING THE VISUAL PERCEPTION OF VELOCITY CHANGE: A MEG STUDY
Supervisor: Dr. JFX DeSouza (link)
MEG Analyses Mentor: Dr. P Ferrari
Research questions
Supervisor: Dr. JFX DeSouza (link)
MEG Analyses Mentor: Dr. P Ferrari
Research questions
Part 1: Motion perception (fast & slow moving dots)
- Is there different cortical representation for fast & slow motion?
- Are there different temporal dynamics for fast & slow motion?
Part 2: Decision-making
- Subjects need to detect a change in the motion velocity and respond with button press
- When and where in the brain is a visual perception (velocity change) transformed into the neural signals for action?
Experiment
- Prior to the imaging sessions, I conducted a perceptual thresholds test (N=22) to acquire the minimal detectable increase and decrease in motion velocity for the subjects
- I set up the experimental environment and collected MEG & MRI data (N=12) with the helps from S. Bells and M. Lalancette at Toronto Sickkids hospital.
- Velocity change in the experiment was set according to each subject's perceptual thresholds, so the correct and incorrect responses could be compared
- A delayed motor response paradigm was used to separate decision-making signals from motor related signals.
Analyses
Results
Part 1 - Motion Perception
No difference in the MT+ locations (Talairach) for fast and slow motion was found (Hotelling's T2 for two multivariate independent samples)
Fig - MT+ locationsFig - comparing the MT+ locations with previous studies
No temporal dynamics for source peak amplitude and latency found
- Velocity and visual display had no effects (3-way ANOVA)
- The amplitude and latency btw the three ROIs were different (P<.05)
- Multiple-comparison showed cuneus had higher amplitude & earlier latency than V3A & MT+
Part 2 - Decision-making
Comparing the grand average event-related beamformer images:
- In the correct responses, the frontoparietal sources were observed at various time points after the velocity change onset (left column, perm-test, P<.05)
- No significant frontoparietal activations were observed in the incorrect responses (right column)
Comparing the time-frequency plots for correct and incorrect responses from IPL and SMC sources:
- IPL source showed a beta power difference between correct and incorrect responses from 200 - 400 ms (area encircled in dotted line)
- The initiation of IPL beta ERS was aligned with the high beta ERD increase in SMC after 400 ms (dotted line)
Friday, May 27, 2011
Problem: # 12 subject
sub#12 has noisy sensor data, but the beamformer reported good MT activation.
Scatter plot: outlier sub#12 is in the black box
When sub#12 is excluded :
(-30 -68 1)
Other subjects' RMS can be found here
Scatter plot: outlier sub#12 is in the black box
When sub#12 is excluded :
Individual virtual sensor time course at MT+, please look at sub#12:
Left Fast
Left Slow
Right Fast
Right Slow
Cuneus
Left Fast
Left Slow
Right Fast
Right Fast
Sunday, May 22, 2011
Monday, May 16, 2011
Glassbrain movies
[A001] Aligned to [motion stimulus] onset
All movies are made with neurological orientation in Tal coordinates from onset (0 ms) of visual stim to 500 ms after onset.
AB
AK
CM
Left_Fast: weak MT+
DA
Left_Fast: interesting, contraL cuneus -> contraL V3A -> ipsiL MT+ -> contraL MT+
ES
JD
Left_Fast:contraL MT+ then moved to ipsiL MT+
PD
Left_Fast: V3A prior to V1 activation
SL
ST (this subject had no strong V3A activation)
SW
Right_Slow
SX
WW
Left_Fast: V3A prior to cuneus
[B002] Group avg for velocity change onset
[A002] Group avg for GO cue onset
[C] Group avg for button press
Incorrect response
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