Electrophysiological evidence for an early attentional mechanism in visual processing in humans

Francesco Di Russo, Donatella Spinelli

Research output: Contribution to journalArticlepeer-review


The effect of sustained spatial attention on a task-irrelevant grating displayed in the left visual field was studied by steady-state and transient visual evoked potentials (VEP). For the steady-state experiment, the task irrelevant grating was phase-reversed at different temporal frequencies. In the transient experiment the grating was reversed abruptly at low temporal frequency. In both conditions a target requiring visual attention was presented either in the left or in the right visual field, directing attention either to the left or to the right. VEPs amplitude enhancement by attention was observed on steady-state VEPs and on P100 and N140 transient VEPs components, confirming previous observations. Moreover, VEPs in the attended condition had shorter latency than VEPs in the unattended condition. The difference was about 15 ms with steady-state; with transient recording the lag was 7 ms for N60 and 10 ms for P100. The latency change of the N60 component, suggests that the modulation of attention on visual processing might be earlier than previously thought. A control experiment to assess the influence of eye movements on the test was also performed. Copyright (C) 1999 Elsevier Science Ltd.

Original languageEnglish
Pages (from-to)2975-2985
Number of pages11
JournalVision Research
Issue number18
Publication statusPublished - Sep 1999


  • Amplitude
  • Attention
  • Latency
  • Visual evoked potential

ASJC Scopus subject areas

  • Ophthalmology
  • Sensory Systems


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