Chantelle Lim^{1}, Baxter P Rogers^{2}, and Victoria L Morgan^{2}

To address the first goal, 3T MRI scans were acquired in 44 healthy controls (23 M, 39.3 yrs +/- 14.3 yrs) and 27 Temporal-Lobe epilepsy (TLE) patients (15 M, 35.8 yrs +/- 15.7 yrs, 4 left TLE and 20 right TLE). The MRI included a T2*-weighted fMRI Blood Oxygenation Level Dependent image at rest with eyes closed for FC (matrix = 80 x 80, field of view = 240 mm, 34 axial slices, echo time = 35 ms, repetition time = 2 sec, slice thickness = 3.5 mm/ 0.5 mm gap, 2 x 300 volumes, 10 minutes).

To compute ALFF, each voxel time series was transformed
into the frequency domain with a fast Fourier transform to obtain the power
spectrum. Then, the square root was calculated at each frequency in the power
spectrum, and the average square root was obtained across a standard frequency
band (0.01-0.08Hz) at each voxel^{3}. This
value was divided by the mean value of the whole brain to obtain the ALFF value
for each voxel (unitless). Groups were compared using a multi
regression model using Statistical Parametric Mapping (SPM) with age as a
covariate.

ALFF = mean(sqrt(ftc(0.01Hz-0.08Hz)))/(Mean ALFF of brain)

To address the second goal, three MRI
scans were acquired in 11 healthy controls (5M/6F, 18–23 years old). 1) CVR was
measured using fMRI during a hypercapnia challenge (units: %ΔBOLD/mmHg). 2)
Resting CBF was quantified using arterial spin labeling MRI methods (units:
ml/100g tissue/min). 3) ALFF was measured using resting-state fMRI. To compare
the different measures, a linear mixed-effects model was fitted to find the
relationship between ALFF, CBF and CVR. For significant relationships found in
the standard band, ALFF computations were then narrowed into four distinct
frequency bands (slow-5: 0.01-0.027 Hz; slow-4: 0.027-0.073 Hz; slow-3:
0.073-0.198 Hz; slow-2: 0.198-0.25 Hz)^{4} for further comparison.

[1] Z. Zhang et al, "FMRI Study of Mesial Temporal Lobe Epilepsy Using Amplitude of Low-Frequency Fluctuation Analysis," Human Brain Mapping, vol. 31, (12), pp. 1851-1861, 2010. \

[2] A. Reyes et al, "Restingāstate functional MRI distinguishes temporal lobe epilepsy subtypes," Epilepsia, vol. 57, (9), pp. 1475-1484, 2016.

[3] Yu-Feng, Wang, et al. "Altered Baseline Brain Activity in Children with ADHD Revealed by Resting-State Functional MRI." Brain and Development, vol. 29, no. 2, 2007, pp. 83-91.

[4] Zuo XN, Di Martino A, Kelly C, Shehzad ZE, Gee DG, Klein DF, Castellanos FX, Biswal BB, Milham MP(2010): The oscillating brain: Complex and reliable. Neuroimage 49:1432–1445.

Figure
1:
Control < R TLE. ALFF is significantly higher in R TLE patients (p <
0.001 uncorrected, extent threshold 10 voxels) in right hippocampus.

Figure 2: Control < L TLE. ALFF is significantly higher in L TLE patients (p < 0.001 uncorrected, extent threshold 10 voxels) in bilateral regions in the temporal lobe.

Table 1: p-values of the relationship
between cerebral hemodynamics and ALFF from a linear mixed-effects model. P
values highlighted in yellow indicate a significant relationship.

Figure 3: % unit change of ALFF per 10
units change of CBF estimate for four distinct frequency bands. ALFF was
multiplied by 100 to convert to % units; CBF was multiplied by 10. The error
bars for each data point show the 95% upper and lower confidence levels.