Spikes analysis in EEG and MEG

1
Spikes analysis in EEG and MEG

• jfernan_at_det.ua.pt
• IEETA/DETI_at_UA

2
Spikes in EEG and MEG

• Question
• Are EEG spikes equal to those found in MEG?
• Methods
• Measure the shapes
• Normalized with background activity
• Selected Spikes
• Occurring in both EEG and MEG
• Occurring at same time (/- 35 ms)
• Compare measures

3
Spike model Measures
original signal

• Duration (Dur)
• PP1/PP2
• Sharpness (C)

first derivative
second derivative
4
They are statistically different
EEG
MEG
Duration
Sharpness
5
EEG and MEG spikes

• Dont trust the looks
• They are different
• MEG spike is
• smaller
• Shorter (take less time)

6
MEG spike is shorter than EEG

• Dont trust the looks
• They are different
• MEG spike is
• smaller (shrink)
• Shorter (take less time)

7
MEG spike is smaller

• Dont trust the looks
• They are different
• MEG spike is
• smaller (shrink)
• Shorter (take less time)

8
MEG spike is smaller

• Dont trust the looks
• They are different
• MEG spike is
• smaller (shrink)
• Shorter (take less time)

9
MEG spike is shorter

• Dont trust the looks
• They are different
• MEG spike is
• smaller (shrink)
• Shorter (take less time)

10
MEG spike is shorter

• Dont trust the looks
• They are different
• MEG spike is
• smaller (shrink)
• Shorter (take less time)

11
MEG spike is shorter

• Dont trust the looks
• They are different
• MEG spike is
• smaller (shrink)
• Shorter (take less time)

12
MEG spike is shorter

• Dont trust the looks
• They are different
• MEG spike is
• smaller (shrink)
• Shorter (take less time)

13
EEG and MEG spikes

• Dont trust the looks
• They are different
• MEG spike is
• smaller (shrink)
• Shorter (take less time)

EEG
MEG
Clinicians must take that into account
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Conclusions

• Results imply that the processes of visual
  inspection of MEG spikes and automatic spike
  detector algorithms should be modified in
  relation to those used in EEG.