Applying Functional Holography to fMRI

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Applying Functional Holography to fMRI
Exploring functional asymmetry in the motor
cortex as a means of determining hemispheric
dominance
Amir Rapson, Eshel Ben-Jacob, Talma
HendlerSchool of Physics Tel Aviv University
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FH- Functional Holography

• A new approach for analyzing complex activity in
  biological networks in the space of functional
  correlations.
• Holography as in holograms, where a part of a
  hologram will still reveal an entire picture, we
  hope to gain the whole functional picture by
  sampling only part of the data
• Itay Baruchi, Vernon L. Towle and Eshel
  Ben-Jacob, Functional Holography of Complex
  Networks Activity From Cultures to the Human
  Brain, Complexity 2005

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FH- Functional Holography

• This is done by combining two parameters to find
  structural resemblance (affinity)
• Time propagation by computing correlations
  between time sequences -
• Functional properties by computing distances
  between correlations (correlation of
  correlations) -

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FH- Functional Holography

Combining the two is done by calculating the
Affinity matrix
Affinity
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FH- Functional Holography

By reducing the number of dimensions, we get the
FH manifold
PCA
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Applying FH to fMRI

• Motor Cortex Unilateral hand movements
• 5 hand movements for each hand
• 15 seconds for each movement
• Instructions to start and to end movements
• Rest period of 10 seconds between movements
• Every block of rest, instruction, movement, rest
  is analyzed as a single event

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Applying FH to fMRI

• Selection of ROIs, and calculating correlations
  between channels

R L
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Applying FH to fMRI

• Clustering and Focusing on larger groups

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Applying FH to fMRI

• Projecting the clusters on the brain

R L
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Applying FH to fMRI

• And computing the FH manifold

L Hemis
R L
R Hemis
L Handed I, R hand movement
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Determining Dominance

• Aim
• Exploring functional asymmetry in the motor
  cortex as a means of determining hemispheric
  dominance

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Determining Dominance

• Structural functional differences between
  hemispheres

L Hemis
R L
R Hemis
L Handed 1, R hand movement
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Determining Dominance

• Structural functional differences between
  hemispheres

L Hemis
R Hemis
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Determining Dominance

• Calculating RG

L Hemis
R Hemis
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Determining Dominance

• Calculating RG

L Hemis
R L
R Hemis
L Handed 1, R hand movement
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Determining Dominance

• Calculating RG

L Hemis
R Hemis
323.29
261.47
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Determining Dominance

• Calculating RG

L Hemis
R Hemis
323.29
261.47
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Determining Dominance

• Right handed subject Right hand movement

R Hemis
R Handed 2, R hand movement
L Hemis
R L
169.93
215.17
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Determining Dominance

• Right handed subject Left hand movement

R Handed 2, L hand movement
R L
L Hemis
291.4
R Hemis
151.06
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Determining Dominance

• Left handed subject Right hand movement

L Handed 1, R hand movement
L Hemis
R L
R Hemis
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Determining Dominance

• Left handed subject Left hand movement

L Handed 2, L hand movement
R L
L Hemis
R Hemis
254.79
120.5
Matrix
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Determining Dominance

• Average ratio nondominant/dominant of 4
  subjects

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Determining Dominance

• Average ratio nondominant/dominant of 4
  subjects
• Left handed 1 0.620.34
• Left handed 2 0.720.13
• Right handed 1 0.630.11
• Right handed 2 0.580.20

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Determining Dominance

• Discussion
• Degree of hemispheric dominance?
• Acquired dominancy?
• Functional rigidness and plasticity?

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Determining Dominance

• Future Tasks
• More Data
• Cross referencing
• Lots of other new routes to explore

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Applying FH to fMRI Other properties

• Functional Connectivity MapsConnectivity between
  M1s through SMA

SMA
R L
R M1
L M1
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Applying FH to fMRI

• Thanks to
• Itay Baruchi,
• Michal Kafri, Yaniv Assaf

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Determining Dominance