An fMRI investigation into the effect of preceding stimuli during visual oddball tasks

Jiří Fajkus*, Michal Mikl, Daniel Joel Shaw, Milan Brázdil

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review


Background: This study investigates the modulatory effect of stimulus sequence on neural responses to novel stimuli. A group of 34 healthy volunteers underwent event-related functional magnetic resonance imaging while performing a three-stimulus visual oddball task, involving randomly presented frequent stimuli and two types of infrequent stimuli - targets and distractors. New method: We developed a modified categorization of rare stimuli that incorporated the type of preceding rare stimulus, and analyzed the event-related functional data according to this sequence categorization; specifically, we explored hemodynamic response modulation associated with increasing rare-to-rare stimulus interval. Results: For two consecutive targets, a modulation of brain function was evident throughout posterior midline and lateral temporal cortex, while responses to targets preceded by distractors were modulated in a widely distributed fronto-parietal system. As for distractors that follow targets, brain function was modulated throughout a set of posterior brain structures. For two successive distractors, however, no significant modulation was observed, which is consistent with previous studies and our primary hypothesis. Comparison with existing methods: The addition of the aforementioned technique extends the possibilities of conventional oddball task analysis, enabling researchers to explore the effects of the whole range of rare stimuli intervals. Conclusion: This methodology can be applied to study a wide range of associated cognitive mechanisms, such as decision making, expectancy and attention.

Original languageEnglish
Pages (from-to)56-61
Number of pages6
JournalJournal of Neuroscience Methods
Publication statusPublished - 5 Aug 2015


  • Attention
  • FMRI
  • Oddball
  • Parametric modulation
  • Stimulus sequence
  • Target


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