fMRI Group Natasha Matthews, Ashley Parks, Destiny Miller, Ziad Safadi, Dana Tudorascu, Julia Sacher. Adviser: Mark Wheeler

Aims Learn to implement block and event-related fMRI experimental designs Develop a thorough understanding of the major choice points in the analysis stream for fMRI data Learn fMRI data post-processing: GLM and group analysis

BlockER Design Pros: High detection power due to response summation Simple analysis Con: Can’t look at effects of single events (e.g., correct vs. incorrect trials; target present vs. absent) Pros: Good estimation of time courses and reasonable detection Enables post hoc sorting (e.g., correct vs. incorrect; target present vs. absent) Con: Some loss of power for the contrast between trial types.

Task: Median Nerve Stimulation A nerve stimulation device is place on the subjects wrist above their median nerve An electrical pulse is applied, resulting in activation of the nerve

Data Acquisition Scanner : Siemens 3T Trio Number of subjects: 3 Anatomical Scan T1 (MPRAGE) Slices : 38 Functional Scan (Block design) Whole Brain Scan Slices : 38 Volumes:144 Voxel Size : 4 mm x 4 mm x 3.2mm Interleaved Acquisition TR : 2s T2* Contrast Scanner : Siemens 3T Trio Number of subjects: 3 Anatomical Scan T1 (MPRAGE) Functional Scan (Event-related design) Whole Brain Scan Slices : 38 Volumes run 1: 256 Volumes run 2: 256 Voxel Size : 4 mm x 4 mm x 3.2mm Interleaved Acquisition TR : 2s T2* Contrast Scanner : Siemens 3T TrioNumber of subjects: 3 Anatomical Scan T1 (MPRAGE) Slices : 38 Voxel Size: 0.5mm x 0.5mm x 1.0mm

Blocked Design

… Time 0 s……....……….22s…….32s…………54s……64s…………86s……..96s……………. …278s Task Volumes……………….11.…….16..…….……27.……32..…………43.……...48.……………. …139 (+5 extra) Rest ZAP Median Nerve Stimulation Localizer Task Design Goal: Determine Motor Cortex Activation Region for Event Related Task

Nerve Stimulation Localizer Task

Data Preprocessing for individual subjects Data Format: convert scanner images to format readable by AFNI Dicom data, reformat to BRICK &.HEAD Time Shift (slice timing correction): interpolation of time series to a specific point in TR (Fourier transformation: most accurate). Spatial Registration (motion correction): of all images in the time series to a base image: we chose 6 th image of run (close to structural image). Smoothing: We investigated 4mm, 8mm, 12mm.

Spatial Smoothing

Box-car Model

Model Fit: No smoothing

Model Fit: 4mm smooth

Model Fit: 8mm smooth

Model Fit: 12 mm smooth

Data Preprocessing: Preparing for group analysis Normalize time series: Regression coefficients now expressed as % signal change. For each run divide each time point by the mean and multiply by 100. Original dataNormalized data

Preparing data for group analysis Registration to standard space: Can be done manually or automatically

Atlas Templates TT_N27+tlrc: AKA “Colin brain”. One subject (Colin) scanned 27 times and averaged. TT_avg152T1+tlrc: Montreal Neurological Institute template, average volume of 152 normal brains.

Group t-test (zap > baseline)

Event-related Design

Event Related Design: Stimulation with 3 different frequencies 2 Hz 3.85 Hz 9 Hz Zap ON Inter-stimulus jitter - 2, 4, 6 seconds

Data from a representative subject 2 Hz3.8 Hz9 Hz

Comparison of 9 Hz Event Related Design and Block Design Block design Event related design

Creation of ROI masks to explore event- related data ROI from functional results (localizer task) ROI based on atlas coordinates

Time courses extracted from functionally defined ROI Peak of the activation Area under the curve

Results of ANOVA on event related data using the PEAK of the time course

Results of ANOVA on event related data using the AREA UNDER THE CURVE

Thank you Mark Wheeler Seong-Gi Kim Tomika Cohen Rebecca Clark Fellow MNTPers!