Synchronization: Making sense of the data


Phillips W (2001) Synchronization: Making sense of the data. Commentary on: Fries, P. et al. Modulation of oscillatory neuronal synchronization by selective visual attention. Science. 2001; 291: 1560–1563. Trends in Cognitive Sciences, 5 (7), p. 285.

First paragraph: The brain receives a great flood of data by which it would be overwhelmed if it did not have procedures for selecting the salient parts. Furthermore, the parts selected must be organized into coherent subsets, such as those dealing with a particular object. Studies that relate attention to synchronized neural activity by Singer and Fries and others have previously revealed that, in the case of binocular rivalry, the signals generated by the selected eye are more synchronized than are those generated by the non-selected eye. Now, new experiments carried out by Fries and co-workers on the visual cortex of awake behaving monkeys suggest that dynamic grouping and the attentional control of salience may be closely related1. They recorded the spiking activity of several small clusters of cells in visual area V4 of macaques.The clusters responded to particular stimuli, which in this case were small patches of horizontal or vertical bars presented within specific areas of the visual field. On different trials the monkey's attention was directed either to the stimulus to which the cluster responded, or to a different stimulus. Cells within clusters responding to the attended stimulus synchronized their activity to a greater extent than did cells within clusters responding to unattended stimuli. This increased synchronization was seen for high-frequency activity in the gamma-band (35–90 Hz). Synchronization of low-frequency activity was reduced by attention. An increase in high-frequency synchronization would be a good way to increase the impact of the population activity of a cluster, because the rapid decay of post-synaptic potentials ensure that inputs will summate at their projection sites much more effectively if they are synchronized. A good analogy is that of a group of people trying to push a car over – they will do so much more effectively if they push in synchrony, rather that at unrelated times.

Cognitive science

Trends in Cognitive Sciences: Volume 5, Issue 7

Publication date31/07/2001
Publication date online19/06/2001
Item discussedFries, P. et al. Modulation of oscillatory neuronal synchronization by selective visual attention. Science. 2001; 291: 1560–1563