Several lines of evidence suggests that searching a visual scene depends on an intrinsic periodicity.  We scan the scene by moving the spotlight of attention at regular intervals.  For example, Buschman and Miller (2009) found neurophysiological evidence in the frontal eye fields for regular shifts of attention at 25 Hz (i.e., every 40 ms).  Dugue et al (2014) have now found evidence in humans using EEG recording and TMS stimulation in humans.   They found successful search was associated with oscillations and phase resetting at 6 Hz.  TMS applied at different intervals found disruption of search at a periodicity corresponding to 6 Hz.  This was slower than reported by Buschman and Miller (2009), but that could be because Dugue et al used a more difficult search task.

This paper:
Theta Oscillations Modulate Attentional Search Performance Periodically
Laura Dugué, Philippe Marque, and Rufin VanRullen  Journal of Cognitive Neuroscience, 2014

For further reading:
Buschman, T.J. and Miller, E.K. (2009) Serial, covert, shifts of attention during visual search are reflected by the frontal eye fields and correlated with population oscillations. Neuron, 63: 386-396. View PDF »

About the Author

The Miller Lab uses experimental and theoretical approaches to study the neural basis of the high-level cognitive functions that underlie complex goal-directed behavior.