For in-phase targets at 177 ms, detection rates were also significantly higher for the rhythmic and variable conditions than the control condition, but the rhythmic and variable conditions did not differ. Detection rates were also significantly higher for the rhythmic than the variable condition. For in-phase targets at 83 ms, detection rates were significantly higher for the rhythmic and variable conditions compared to the control condition. In-phase targets (blue boxes) were detected more often than out-of-phase targets (pink boxes). (b) Target detection as a function of target lag. Lags of 36 and 130 ms, indicated by pink boxes, were out-of-phase, meaning that they represented time points directly between rhythmic stimuli if entraining had continued. Lags of 83 and 177 ms, indicated by blue boxes, were in-phase with the entrainment rhythm, meaning that they represented time points at which rhythmic stimuli would have occurred had entraining continued. Targets were then presented at one of seven randomly chosen lags after the entraining period. The control condition presented only two annuli at the beginning and end of the entraining period. Eight annulus stimuli were presented with a fixed, 83 ms SOA (12 Hz) in the rhythmic condition and a variable SOA in the variable condition. Each trial began with a fixation and blank screen, followed by an entraining period in which one of three conditions was presented. Participants were instructed to detect small circular targets that were backward-masked by an annulus. (a) SOA = stimulus onset asynchrony, eSOA = entrainer SOA, tSOA = target SOA, mSOA = mask SOA. Oscillatory phase remained entrained to the stimulation rhythm for several cycles after the last stimulus (adapted, with permission, from ).Ī recent study showing that the phase of entrained alpha oscillations affects stimulus detection (adapted, with permission, from ). Blue vertical lines represent stimuli and red lines represent when stimuli would have occurred if stimulation had continued. (b) Supragranular current source density trace recorded from a monkey showing entrainment of ongoing oscillations to rhythmic auditory stimuli. Oscillations remain entrained for several cycles after the last stimulus before eventually “falling out of phase” due to frequency changes. As a consequence of entrainment, neural ensembles are in a particular state of excitability when stimuli occur. The second stimulus establishes a rhythm, and oscillatory frequencies adjust such that phases become aligned to this rhythm. The phases of ongoing oscillations are reset by the first stimulus. The excitability of neural ensembles oscillates at various frequencies. (a) Stylized example of oscillatory entrainment by rhythmic auditory stimuli. Accordingly, we suggest that studying entrainment in selective-attention paradigms is likely to reveal mechanisms underlying deficits across multiple disorders.ĮEG attention-deficit/hyperactivity disorder dyslexia entrainment schizophrenia selective attention.Ĭopyright © 2014 Elsevier Ltd. Deficient entrainment has been found in schizophrenia and dyslexia and mounting evidence also suggests that it may be abnormal in attention-deficit/hyperactivity disorder (ADHD). Entrainment appears to form one of the core mechanisms of selective attention, which is likely to be relevant to certain psychiatric disorders. Moreover, selective attention to a particular rhythm in a complex environment entails entrainment of neural oscillations to its temporal structure. Intrinsic oscillations also entrain to external rhythms, allowing the brain to optimize the processing of predictable events such as speech. Oscillations of neural excitability shape sensory, motor, and cognitive processes.
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