applying functional holography to fmri exploring functional asymmetry in the motor cortex as a means...

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

Tel-Aviv Human Brain Mapping May 2005

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



• 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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Affinity

Combining the two is done by calculating the Affinity matrix:

ij

ijij D

CA



PCA

By reducing the number of dimensions, we get the FH manifold:


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


Applying FH to fMRI

• Selection of ROIs, and calculating correlations between channels

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L


Applying FH to fMRI

• Clustering and Focusing on larger groups


Applying FH to fMRI

• Projecting the clusters on the brain

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L


Applying FH to fMRI

• And computing the FH manifold

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L

L Hemis

R Hemis

L Handed I, R hand movement


Determining Dominance

Aim:

Exploring functional asymmetry in the motor cortex as a means of

determining hemispheric dominance



• Structural functional differences between hemispheres

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L

R Hemis

L Hemis

L Handed 1, R hand movement



• Structural functional differences between hemispheres

R Hemis

L Hemis


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L Hemis

• Calculating RG: ji

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Dominance

FunctionalStructure

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• Right handed subject: Right hand movement

215.17169.93

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• Right handed subject: Left hand movement

151.06291.4

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LR Hemis

L Hemis

R Handed 2, L hand movement



• Left handed subject: Right hand movement

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L

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• Left handed subject: Left hand movement

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Matrix

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L Handed 2, L hand movement



• Average ratio nondominant/dominant of 4 subjects:

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)( DOMG

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• Average ratio nondominant/dominant of 4 subjects:

– Left handed 1: 0.62±0.34– Left handed 2: 0.72±0.13

– Right handed 1: 0.63±0.11– Right handed 2: 0.58±0.20



Discussion

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


Applying FH to fMRI – Other properties

• Functional Connectivity MapsConnectivity between M1s through SMA

SMA

L M1

R M1R

L


Applying FH to fMRI

Thanks to:

Itay Baruchi,

Michal Kafri, Yaniv Assaf

applying functional holography to fmri exploring functional asymmetry in the motor cortex as a means...

Documents

fh functional holographythis

functional picture

hemispheresrlr hemisl

fh manifoldrll hemisr

rlr hemisl hemisr

computing correlations

right hand movement215

left hand movement151