Prediction: depending on the site of imaging, cytochrome oxidase (CO) blobs and orientation preference will show different relationships. The upper image shows the prediction that when imaging is done in the fovea (red dot), CO blobs and singularities will tend to coincide. The lower image shows the prediction that when imaging is done outside the fovea (red dot), CO blobs will tend to have an orientation preference equal to the polar angle of the imaging site. In this case, imaging at the horizontal meridian leads to the prediction that CO blobs will tend to have a horizontal orientation preference.

Contextual modulation of neuronal activity is measurable in V1 from distal stimuli extending over large regions of the visual field. Optical imaging studies in the early visual system of the cat have shown that context-only orientation preference and texture defined boundaries are both mapped into the same topographic structure as orientation preference. The mapping of contextual inputs is therefore closely related to the structure of orientation preference pinwheels. A novel prediction of this mapping, in the monkey, is that the orientation preference within CO blobs will change systematically with retinotopic location within V1. We re-analysed data from Vanduffel et al. (2002), who used double-label deoxyglucose (DG) techniques to measure orientation preference over large regions of V1. The analyses showed that CO blobs along the horizontal meridian of V1 had a strong tendency to coincide with regions of horizontal orientation preference, while interblob regions tended to have vertical orientation preference.

A related prediction can be tested for DG imaging from the vertical meridian of monkey V1: CO blobs in this region will tend to have a vertical orientation preference.