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

J Neurosci Methods. 2015 May 16;

Authors: Fajkus J, Mikl M, Shaw DJ, Brázdil M

Abstract
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 examination 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 prime hypothesis. Comparison with existing methods: The involvement of aforementioned technique extends the possibilities of conventional oddball task analysis and enables to explore the effects in the whole range of rare stimuli intervals.
CONCLUSION: This methodology can be efficiently applied to study wide range of associated cognitive mechanisms, such as decision making, expectancy and attention.

PMID: 25989317 [PubMed - as supplied by publisher]