CONEUR-459; NO OF PAGES 7 The role of neuronal synchronization in selective attention Thilo Womelsdorf and Pascal Fries Attention selectively enhances the inﬂuence of neuronal responses conveying information about relevant sensory attributes. Accumulating evidence suggests that this selective neuronal modulation relies on rhythmic synchronization at local and long-range spatial scales: attention selectively synchronizes the rhythmic responses of those neurons that are tuned to the spatial and featural attributes of the attended sensory input. The strength of synchronization is thereby functionally related to perceptual accuracy and behavioural efﬁciency. Complementing this synchronization at a local level, attention has recently been demonstrated to regulate which locally synchronized neuronal groups phase-synchronize their rhythmic activity across long-range connections. These results point to a general computational role for selective synchronization in dynamically controlling which neurons communicate information about sensory inputs effectively. Addresses FC Donders Centre for Cognitive Neuroimaging, Radboud University Nijmegen, Kapittelweg 29, 6525 EN Nijmegen, The Netherlands Corresponding author: Womelsdorf, Thilo (t.womelsdorf@fcdonders.ru.nl) Current Opinion in Neurobiology 2007, 17:1–7 This review comes from a themed issue on Cognitive neuroscience Edited by Keiji Tanaka and Takeo Watanabe 0959-4388/$ – see front matter # 2006 Elsevier Ltd. All rights reserved. DOI 10.1016/j.conb.2007.02.002 Introduction Voluntary ‘top-down’ attention is a key mechanism to select relevant subsets of sensory information for detailed and effective processing and to actively suppress distract- ing irrelevant sensory information. The behavioural con- sequences of attentional selection are manifold and include faster processing and reaction times, higher accuracy levels, enhanced sensitivity for ﬁne changes and increased apparent contrast. These behavioural con- sequences of attention are accomplished by highly selec- tive modulation of neuronal responses at two spatial scales of processing: within and across cortical regions. First, attention enhances the neuronal representation of attended sensory input within the local neuronal popu- lations that are tuned to the attended spatial [1] or featural [2] dimensions. Second, selective attention regulates the communication among neuronal groups in spatially distant areas, ultimately enhancing effective interactions among those neuronal groups that convey the behaviou- rally relevant information [3]. Growing evidence suggests that both of these neuronal characteristics of selective attention depend on selective neuronal synchronization. Attention selectively modulates which neurons synchronize their responses with the rhyth- mic ﬂuctuation of a local functional group of neurons that represents the attended stimulus feature or position. Like- wise, the inﬂuence of selective attention to shape neuronal interactions among distant neuronal populations is likely to recruit selective synchronization. Such long-range synchro- nization of locally enhanced neuronal representations has long been implicated in attention, but only recent studies demonstrate that neuronal representations that pertain to attended, relevant information are mutually phase-syn- chronized across long distances. In this article we review evidence, gathered over the past two years from animal and human studies, that suggests a functional role for local and long-range selective synchro- nization of rhythmic neuronal activity. The view emer- ging from these studies is that synchronization might reﬂect a basic computational principle that underlies the dynamic control of effective interactions along selec- tive subsets of the anatomically possible neuronal con- nections [4]. Selective synchronization and spatial attention Investigating the inﬂuence of selective attention on neuronal synchronization depends on tasks in which there is identical sensory stimulation across conditions but covert attention is directed to different aspects of this sensory input. Based on such tasks, visual cortical neurons that have receptive ﬁelds overlapping with an attended stimulus synchronize their spiking responses more strongly with the local ﬁeld potential (LFP) than do neurons that are activated by a non-attended stimu- lus [5]. This early ﬁnding from monkey visual area V4 has recently been extended by showing a rather continu- ous relationship between the strength of selective syn- chronization and behavioural performance [6  ]. In this study, attention was spatially cued to select one of two stimuli to detect a colour change of the attended stimulus. The speed of detecting the behaviourally relevant colour change in an attended stimulus varied across trials and could be partially predicted by the degree of synchroni- zation in response to that stimulus. Notably, synchroniza- tion in the gamma-frequency band (40–100 Hz) predicted the speed of change detection shortly before the colour www.sciencedirect.com Current Opinion in Neurobiology 2007, 17:1–7 Please cite this article in press as: Womelsdorf T, Fries P, The role of neuronal synchronization in selective attention, Curr Opin Neurobiol (2007), doi:10.1016/j.conb.2007.02.002