Matthew Potter

Back to Psych 204B Projects 2010

Timecourses vs. Multi-Voxel Patterns in Face- and Place-selective Regions

This project investigates the selectivity of the Fusiform Face Area (FFA), Occipital Face Area (OFA), Parahippocampal Place Area (PPA), and Temporo-Occipital Sulcus (ToS) in terms of timecourses and multi-voxel patterns, using the human motion area (MT), which is presumably not selective for these objects, as a control.

Background

Though certain regions of the brain show a preference for certain objects, e.g. faces or places, whether these regions are specialized for this task, or whether the task is distributed across a wider region of the brain, is a subject of debate. One facet of this debate is the use of regions of interest (ROIs), across which the mean beta response is generally calculated. Is this assumption reasonable, or is important information lost by not analyzing the distribution of activity across the individual voxels? Do the two methods lead to the same interpretation of the function of certain regions?

Methods

Subjects

One 22-year-old female participated in this study.

MR acquisition

Images for this study were acquired on a 3T GE Signa MRI scanner at Stanford University.

Figure 3: GLM design matrix We estimated a GLM with four regressors of interest. Two separate regressors were created for the time periods during which the subject were presented with the outcome of the trial, one for trials when the subject won, and another for when the subject lost. For trials in which the subject won, monetary outcome was used as a parametric modulator, which was the third predictor. A final regressor was included for the entry time period, i.e., the time during which participants made their bids based on private estimate and error information. This regressor was included to control for potential carryover effects of BOLD activity into the time window of interest, the outcome period. Six additional regressors of no interest were included for motion. Regressors were convolved with a canonical hemodynamic response function (SPM5). Figure 3 (right) shows a graphic representation of the GLM design matrix.

We examined the brain activation associated with the social value of winning/losing the auction (Win>Lose) by contrasting the regressors for the outcome period for win vs loss trials. We also ran one-sample t-tests to find brain regions which activated significantly during the outcome periods for win/lose trials to baseline (mean activation across all trials). A threshold of p<0.05 after FWE correction was applied (extent threshold = 4). Data at a more liberal threshold (p<0.001, uncorrected, extent threshold=4) is also presented.

MR Analysis

The MR data was analyzed using mrVista software tools.

Conclusions

Here is where you say what your results mean.