What am I looking at?

You are looking at a cognitive concept tree that shows the relative contribution of different cognitive concepts for a single location in the brain, an x,y,z coordinate called a "voxel" to a model generated at the voxel. Each circle represents a single cognitive concept, colored to indicate its importance for the voxel's model (darker = more important, blue = positive weight, red = negative weight), and sized by the number of statistical brain maps with the label that contributed to the model result.

What do you mean "relative contribution?"

We used a bunch a brain maps labeled with cognitive concepts to generate a sparse Logistic Regression model at each voxel (think an x,y,z coordinate in a 3D brain map), meaning that we found an optimal weighting of each cognitive concept to predict the voxel values across a large set of images. You are looking at the "relative contribution" (e.g., importance) of each concept for a particular voxel, represented by the weight (the beta or regression parameter) produced by the model. This importance is represented in color, and you will notice many faint or completely white nodes. Although these concepts exist, they were not relevant to the voxel's model.

What do these voxel-wise models do?

Having a model at each voxel means that we can use cognitive concepts to predict brain maps, and predict cognitive concepts from a new brain map. The model is sparse because the algorithm sets the weights of as many of the regression parameters (one for each cognitive concept) to zero. Thus, although there are a total 132 cognitive concepts, you will only see a small number of strongly blue or red nodes.

How do I find concepts?

Use our Concept Explorer button in the top right to select concepts you are interested in, and they will be highlighted in the tree.

Why aren't all of the nodes labeled?

Nodes with an importance value greater than a threshold of 0.5 and having more than 15 associated images are labeled automatically to not clutter the visualization. If you want more info on a node, simply mouse over it to see. If you want to view the concept in the Cognitive Atlas, simply click the node.

How do I explore different regions?

If you use the region selector in the bottom left, you will be taken to a random voxel within the region. Some regions are very large, meaning the model looks very different between voxels in the same region, and for this reason we encourage you to reload the same region multiple times to see the variance. Brain regions correspond to randomly selected MNI (x,y,z) coordinates from the AAL2 atlas resampled to 4mm with nearest interpolation. Data and labels were obtained courtesy of NeuroVault. Full script to generate coordinates is available.