Article: Knops, A., B. Thirion, et al. “Recruitment of an Area Involved in Eye Movements During Mental Arithmetic.” Science 324, no. 5934 (2009): 1583–85. DOI: 10.1126/science.1171599

Assignment: Read the assigned article carefully and think about it, then provide short answers to the questions below. You can do this by responding straight on this document or by submitting a separate document with numbered answers. Be clear and concise—points will be taken off for unnecessary words.

1. What is the central empirical claim of the paper in a single sentence?

Activations in the posterior parietal cortex can predict left or right eye movement. This classification can be used to predict whether the subject is performing addition or subtraction. This suggests that mental arithmetic uses the same mental circuitry as spatial coding.

1. Is the data in this paper consistent with the idea that a brain region exists that is specifically engaged in processing number and arithmetic only? Why or why not.

No because this same region is shown to used for spatial processing / saccades.

1. What is the contrast that Knops et al. used to identify the standard brain regions engaged in saccades (eye movements)? Is this contrast a minimal pair? Is that important for this study?

The contrast is between eye movements and fixation. Whether this is a minimal pair depends on how the localization study is performed.

This is important since these voxels are used to make predictions on saccades. If the wrong regions are selected, the accuracy of the classifier may be too low. If it is too low, we can’t determine whether a pattern is significantly higher than chance.

1. Can you think of a more general version of Knops et al.’s hypothesis, that applies not just to eye movements but to any rightward versus leftward movement? How might you test this hypothesis using motor cortex? What would the key prediction be?

Rather than saccades we can have the subjects perform various left right behaviors. This can include turning head, raising left or right hand, visual or auditory stimulation on left or right side. The same model can make predictions on all of this. We would need to carefully design the localization task. This would be evidence that addition/subtraction is correlated at a higher level with left/right spatial movement.