The oddball paradigm is a method used in evoked potential research in which trains of stimuli that are usually auditory or visual are used to assess the neural reactions to unpredictable but recognizable events. The subject is asked to react either by counting or by button pressing incidents of target stimuli that are hidden as rare occurrences amongst a series of more common stimuli, that often require no response. It has been found that an event related potential across the parieto-central area of the skull that is usually around 300 ms and called P300 is larger after the target stimulus.
The P300 wave only occurs if the subject is actively engaged in the task of detecting the targets. Its amplitude varies with the improbability of the targets. Its latency varies with the difficulty of discriminating the target stimulus from the standard stimuli.
Detection of these targets reliably evokes transient activity in prefrontal cortical regions. Measuring hemodynamic brain activity in the prefrontal cortex using functional magnetic resonance imaging (fMRI) revealed that the dorsolateral prefrontal cortex is associated with dynamic changes in the mapping of stimuli to responses (e.g. response strategies), independently of any changes in behavior.
Since P300 has been shown to be an attention-dependent cognitive component in wakefulness, one might suppose that it would be absent during sleep; a time in which information processing of external stimuli is commonly thought to be inhibited. Research to date indicates that P300 can be recorded during the transition to sleep and then reappears in REM sleep. Stimuli that are rare and intrusive are more likely to elicit the classic parietal P300 in REM sleep. There is, however, little or no positivity at frontal sites. This is consistent with brain imaging studies that show frontal deactivation is characteristic of REM sleep. These findings indicate that while sleepers may be able to detect stimulus deviance in stage 1 and REM, the frontal contribution to consciousness may be lost.
Studies of cognition often use an oddball paradigm to study effects of stimulus novelty and significance on information processing. However, an oddball tends to be perceptually more novel than the standard, repeated stimulus as well as more relevant to the ongoing task, making it difficult to disentangle effects due to perceptual novelty and stimulus significance. Evaluating different brain ERP’s can decipher this effect. A frontro-central N2 component of ERP is primarily affected by perceptual novelty, whereas only the centro-parietal P3 component is modulated by both stimulus significance and novelty.
The classic auditory oddball paradigm can be modified to produce different neural responses and can therefore be used to investigate dysfunctions in sensory and cognitive processing in clinical samples.
A unique application of the oddball paradigm is being used heavily in Schizophrenia research to study the effects in neuronal generator patterns in continuous recognition memory, and the endophenotypes, which provide model on genetic relation of psychiatric diseases that represents phenotypes between manifest clinical syndrome and genetic underpinnings.
The Oddball paradigm has robust effects on pupil dilation, although scientists are unsure of the reason underlying this effect.
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- Beyond the Oddball in Schizophrenia Research: Neurophysiologic Studies of Memory and Language Processing. (2010). Psychophysiology, 47S10-S11.
- G.A. Book, M.C. Stevens, G. Pearlson, K.A. Kiehl - Fusion of fMRI and the Pupil Response During an Auditory Oddball Task - Accepted to the 2008 Conference of the Cognitive Neuroscience Society.