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.

To define face-, place-, and motion-selective regions of interest, three localizer experiments were performed. For the face- and place-selective localizer, a GLM with two regressors, alternating blocks of faces and places presented to the fovea, was estimated. For the motion-selective localizer, a GLM with two regressors, alternating blocks of expanding and contracting low-contrast gratings, was estimated. Next, regressors were convolved with the SPM hemodynamic response function. Lastly, an independent run consisting of alternating blocks of faces, places, and objects was used to investigate the brain activation in associated with these items in the regions of interest defined by the localizers.

Figure 1: HRF and Design Matrix

MR Analysis

For each region of interest, the timecourse and multi-voxel pattern responses were computed using mrVista.

Results

Legend

For the figures in this section, the following abbreviations are used:

CH: Child's Face
M: Adult Male's Face
I: Indoor Scene
O: Outdoor Scene
CA: Car
A: Abstract Object

Parahippocampal Place Area (PPA)

Figure 2: Defined PPA ROIs, Beta Responses, and Cross-correlation Matrices

Conclusions

Here is where you say what your results mean.