# Presentation: 898498

## “Cutting Edge” of fMRI

- Extracting transient neuronal activity
- 	Peter Bandettini, NIMH, Bethesda, MD, USA
- Magnetic Source MRI
- 	Jin-Hu Xiong, San Antonio, TX, USA
- BOLD latency mapping and regional multivariate pattern extraction
- 	Rainer Goebel, Maastricht, Netherlands
- Physiologic parameter quantification based on T2’ mapping
- 	Hongyu An, Chapel Hill, NC, USA

## Extracting transient neuronal activity 

- Peter A. Bandettini, Ph.D
- Unit on Functional Imaging Methods
- &
- Functional MRI Facility
- Laboratory of Brain and Cognition
- National Institute of Mental Health

## Functional Neuroimaging Techniques

- Log Time (sec)

- Log Size (mm)

- Non-invasive

- Invasive

## Extracting transient neuronal activity 

- Initial transient mapping
- BOLD latency and width modulation/mapping
- Direct neuronal current imaging

## task

*task*

*task*

## Methods

- 16 s

- Stimulus Duration (SD)

- SD = 250 ms

- SD = 500 ms

- SD = 1000 ms

- SD = 2000 ms

- ...

- ...

- ...

- ...

- 20 s

- Blocked Trial

*Visual*

- SD = 500 ms

- SD = 1000 ms

- SD = 2000 ms

- SD = 4000 ms

*Motor*

- ...

## Brief stimuli produce larger responses than expected

- measured

- linear

- Signal

- 0.25 s

- 0.5 s

- 1 s

- 2 s

- 20 s

- Stimulus
- timing

- BOLD
- Response

*Brief stimuli produce larger responses than expected*

**R. M. Birn, Z. Saad, P. A. Bandettini, (2001) “Spatial heterogeneity of the nonlinear dynamics in the fMRI BOLD response.” *****NeuroImage*****, 14: 817-826.**

## BOLD response is nonlinear

*Short duration stimuli produce larger responses than expected*

- Observed response

- Linear response

## Spatial Heterogeneity of BOLD Nonlinearity

**R. M. Birn, Z. Saad, P. A. Bandettini, (2001) “Spatial heterogeneity of the nonlinear dynamics in the fMRI BOLD response.” *****NeuroImage*****, 14: 817-826.**

**Spatial Heterogeneity of BOLD Nonlinearity**

## Results – visual task

- Nonlinearity

- Magnitude

- Latency

**R. M. Birn, Z. Saad, P. A. Bandettini, (2001) “Spatial heterogeneity of the nonlinear dynamics in the fMRI BOLD response.” *****NeuroImage*****, 14: 817-826.**

## Results – motor task

- 2

- 4

- 6

- 8

- 0

- 1

- 2

- 3

- 4

- 5

- Stimulus Duration

- f (SD)

## Results – motor task

- Nonlinearity

- Magnitude

- Latency

## Reproducibility

- Nonlinearity2

- Nonlinearity1

- Nonlinearity2

- Nonlinearity1

*Visual task*

*Motor task*

- Experiment 1

- Experiment 2

- Experiment 1

- Experiment 2

**Notes:**
Even though we find a large variation in nonlinearity that is not significantly correlated with either magnitude or latency, the spatial maps of nonlinearity are reproducible, shown here for the computed nonlinearities plotted for two separate runs at all the stimulus durations.  

## Sources of this Nonlinearity

- Neuronal
- Hemodynamic
- Oxygen extraction
- Blood volume dynamics

- Volume

- Flow In

- Flow Out

- Oxygen Extraction

## BOLD Correlation with Neuronal Activity

**Logothetis et al. (2001) “****Neurophysiological investigation of the basis of the fMRI signal” ****Nature, 412, 150-157.**

**P. A. Bandettini and L. G. Ungerleider, (2001) “From neuron to BOLD: new connections.” Nature Neuroscience, 4:  864-866.**

## Simulation

- 0

- 1000

- 2000

- 3000

- 0

- 1

- 2

- 3

- Measured Amplitudes

- Stimulus Duration (ms)

- Amplitude (%)

- Estimated
- Neuronal
- activity

**a** = initial slope

**b** = final slope

- 200

*Simulation*

**Notes:**
Averaged over ROI (entire activated region) and across 5 subjects.  (Each subject showed a similar response, but noisier.)

What can be seen: 

## Slide 17

## Extracting transient neuronal activity 

- Initial transient mapping
- BOLD latency and width modulation/mapping
- Direct neuronal current imaging

## Latency

**Latency**

**Magnitude**

**+ 2 sec**

**- 2 sec**

**P. A. Bandettini, The temporal resolution of Functional MRI *****in*****  "Functional MRI" (C. Moonen, and P. Bandettini., Eds.), p. 205-220, Springer - Verlag,. 1999. **

**Venogram**

## Hemi-Field Experiment

**Right Hemisphere**

**Left Hemisphere**

## =

**=**

**+ 2.5 s**

**- 2.5 s**

**0 s**

**500 ms**

**500 ms**

**Right**** ****Hemifield**

**Left Hemifield**

**-**

## Proc. Nat'l. Acad. Sci. USA 100, 1415-1419 (2003).  

***Proc. Nat'l. Acad. Sci. USA *****100, 1415-1419 (2003).  **

## Regions of Interest

- Word vs. Non-word

- 0o, 60o, 120o Rotation

- Inferior Frontal Gyrus

- Precentral Gyrus

- Middle Temporal Gyrus

## Estimation of Delay, Width & Amplitude

**time (s)**

**Conv.**

**Adjust ********** to improve fit ****(Nelder-Mead simplex method)**

**5**

**10**

**15**

**0**

**0**

**20**

## Lexical effect

**Magnitude**

**Delay**

**Width**

**Lexical effect**

**Rotational effect**

**Words > Nonwords**
**Nonwords > Words**

**0 deg > 120 deg**
**120 deg > 0 deg**

## Extracting transient neuronal activity 

- Initial transient mapping
- BOLD latency and width modulation/mapping
- Direct neuronal current imaging

## Preliminary models suggest that magnetic field changes on the order of 0.1 to 1 nT are induced (at the voxel scale) in the brain.

**Preliminary models suggest that magnetic field changes on the order of 0.1 to 1 nT are induced (at the voxel scale) in the brain.**
**These changes induce about a 0.01 Hz frequency shift or 0.09 deg (@ TE = 30 ms) phase shift. **
**Question:**** Is this detectable?**

***Magn. Reson. Med***** 47: 1052-1058, (2002)***** ***

## Slide 28

## In Vitro Results

**In Vitro Results**

***Newborn rat brains have been found to exhibit spontaneous and synchronous firing at specific frequencies***

**Cortex**

**Striatum**

**Subthalamic nucleus**

**Globus Pallidus**

- Plenz, D. and S.T. Kital. Nature, 1999. **400**: p. 677-682.

**Notes:**
To test our hypothesis (based on theoretical modeling and phantom experiments previously presented at hbm plus publications, etc) that the effects of neuronal currents can be imaged with MRI we performed in vitro experiments on rat brain slices. The cultures contain cortical, and basal ganglia tissue and exhibit spontaneous synchronous activity at <2Hz. The activity initiates at roughly every 10 sec and occurs in a cascade from cortex to basal ganglia. This property combined with the fact that we can avoid physiological fluctuations, makes this physiological model ideal to examine the possibility of imaging neuronal current effects, and thus further develop acquisition and analysis methods specific to this contrast mechanism
Trace was obtained with a single-channel recording

## *: activity

- _Active_ state: 10 min, _Inactive_ state: 10 min after TTX admin.

- *

- *

- #

- *

- *

- #

- Culture

- CSF

- FSE image

**Hz**

**Hz**

**CSF**

**Culture**

*******:**** activity**
**#****:**** scanner pump frequency**

**Petridou et al. Poster #694**
**Poster discussion: Saturday, 9:42-9:54 AM**

**Notes:**
Note: each culture has a different on-off frequency (some of the cultures we had were epileptic, like this one, and I assume they had different activity patterns than non-epileptic ones). This spectrum was calculated with a sliding window fft of 150sec.