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Abstract

In crowded visual scenes, attention is needed to select relevant stimuli. To study the underlying mechanisms, we recorded neurons in cortical area V4 while macaque monkeys attended to behaviorally relevant stimuli and ignored distracters. Neurons activated by the attended stimulus showed increased gamma-frequency (35 to 90 hertz) synchronization but reduced low-frequency (<17 hertz) synchronization compared with neurons at nearby V4 sites activated by distracters. Because postsynaptic integration times are short, these localized changes in synchronization may serve to amplify behaviorally relevant signals in the cortex.
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Supplementary Material

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Animal care was in accordance with NIH guidelines. Standard procedures were used to record spike and LFP activity simultaneously from four extracellular electrodes in V4 of two monkeys (electrode separations of 650 or 900 μm; Plexon data acquisition system). The LFP (filtered at 1 to 100 Hz) reflects the average transmembrane currents of neurons in a volume of a few hundred micrometers radius around the electrode tip (41). Negative values of LFP correspond to neuronal activation. Spike waveforms were stored for offline sorting. We pooled all neurons recorded through a given electrode [≈2 to 10 neurons; see supplementary information (24)]. The resulting multi-unit almost always showed clear oscillatory synchronization. Analysis of single units revealed that some showed much stronger oscillatory synchronization than others. Whenever there was clear oscillatory synchronization, attention effects were essentially identical, irrespective of whether the spikes were pooled or from an isolated neuron.
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Published In

Science
Volume 291 | Issue 5508
23 February 2001

Submission history

Received: 5 September 2000
Accepted: 22 December 2000
Published in print: 23 February 2001

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Authors

Affiliations

Pascal Fries*
Laboratory of Neuropsychology, National Institute of Mental Health, National Institutes of Health, Building 49, Room 1B80, 9000 Rockville Pike, Bethesda, MD 20892–4415, USA.
John H. Reynolds
Laboratory of Neuropsychology, National Institute of Mental Health, National Institutes of Health, Building 49, Room 1B80, 9000 Rockville Pike, Bethesda, MD 20892–4415, USA.
Systems Neurobiology Laboratory, The Salk Institute for Biological Studies, 10010 North Torrey Pines Road, La Jolla, CA 92037–1099, USA.
Alan E. Rorie
Laboratory of Neuropsychology, National Institute of Mental Health, National Institutes of Health, Building 49, Room 1B80, 9000 Rockville Pike, Bethesda, MD 20892–4415, USA.
Robert Desimone
Laboratory of Neuropsychology, National Institute of Mental Health, National Institutes of Health, Building 49, Room 1B80, 9000 Rockville Pike, Bethesda, MD 20892–4415, USA.

Notes

*
To whom correspondence should be addressed. E-mail: [email protected]

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