Home About us Contact
|
Home About us Contact | ||
|
|
||
Stimulus Onset Asynchronies (stimulus + onset_asynchrony)
Selected AbstractsFast, but Error-Prone, Responses During Acute Alcohol Intoxication: Effects of Stimulus-Response Mapping ComplexityALCOHOLISM, Issue 4 2004Tom A. Schweizer Abstract: Background: Although moderate doses of alcohol can impair performance on tasks that require information processing, little is known about the locus of the alcohol effects within the processing stream. This study used a psychological refractory period paradigm to investigate the effect of alcohol on the central, cognitive stage of information processing when task complexity is manipulated by altering stimulus-response compatibility. Methods: Thirty-four healthy male social drinkers were assigned to one of two groups (n= 17) that performed two tasks. Each trial consisted of a task 1 stimulus (tone) followed by a task 2 stimulus (letter) that was presented after one of four stimulus onset asynchronies (50, 200, 500, or 1100 msec). A baseline test of performance was obtained before the groups received a beverage containing either 0.0 g/kg (placebo) or 0.65 g/kg alcohol. Both groups were retested when blood alcohol concentration (BAC) was increasing and was decreasing. Results: The alcohol group made significantly more errors in task 1 compared with their drug-free baseline measure during the ascending phase of the BAC curve, and error rates increased to a greater extent for the more complex arbitrary stimulus-response mapping condition. Moreover, this increase in errors continued unabated during the descending phase of the BAC curve. Increasing BACs also slowed performance (longer reaction time), but unlike errors, reaction time returned to drug-free baseline levels when BAC was decreasing. Conclusions: The results provide evidence that an acute dose of alcohol can impair one aspect of the central, cognitive stages of information processing. The possibility that errors in information processing remain during decreasing BACs even after processing speed has returned to drug-free levels has important practical implications relating to the detrimental consequences of acute alcohol intoxication. [source] Backward masking and visual mismatch negativity: Electrophysiological evidence for memory-based detection of deviant stimuliPSYCHOPHYSIOLOGY, Issue 4 2007István Czigler Abstract Sequences composed of two different colored checkerboard patterns (standard and deviant) were presented to adults. Each pattern was followed by a mask with stimulus onset asynchronies (SOAs) varying between 14 and 174 ms. ERPs were recorded to the deviant and standard stimuli while the participants detected changes of a cross, which was continuously present at the center of the screen. In further experiments, the participants performed a Go-NoGo task detecting the deviant checkerboards. Deviant stimuli elicited an occipital negative component with 124,132 ms mean latency (the visual mismatch negativity, vMMN) at test (standard or deviant)-to-mask SOAs longer than 27 ms. No vMMN amplitude increase was observed beyond 40 ms test-to-mask intervals, whereas detection of deviant checkerboard patterns improved up to 174-ms SOA. Therefore the processes underlying vMMN elicitation cannot fully explain the overt detection of visual deviance. [source] The relationship between prepulse detection and prepulse inhibition of the acoustic startle reflexPSYCHOPHYSIOLOGY, Issue 3 2001Peggy Postma Prepulse inhibition (PPI) of the startle reflex is defined as the attenuation of the startle response to a startling stimulus (pulse), when such a stimulus is briefly preceded by a stimulus of subthreshold intensity (prepulse). PPI is thought to be neither learned nor due to conscious response inhibition, as it occurs at stimulus onset asynchronies (SOAs) too short to enable the activation of a volitional response. The present study explored the latter of these assertions by investigating (a) the degree to which human subjects are able to detect prepulses at SOAs of 30, 60 and 120 ms, and (b) whether such detection is related to inhibition. Startle eyeblink reflex and detection were measured in 39 participants subjected to an acoustic startle paradigm. Results revealed a significant trend in prepulse detection according to SOA, with highest detection rates at the 120-ms SOA (75%). However, trials on which detection occurred did not differ from trials without detection on measures of startle inhibition. This suggests that PPI is independent of awareness of the prepulse. [source] Orienting of visual attention among persons with autism spectrum disorders: reading versus responding to symbolic cuesTHE JOURNAL OF CHILD PSYCHOLOGY AND PSYCHIATRY AND ALLIED DISCIPLINES, Issue 7 2009Oriane Landry Background:, Are persons with autism spectrum disorders (ASD) slower than typically developing individuals to read the meaning of a symbolic cue in a visual orienting paradigm? Methods:, Participants with ASD (n = 18) and performance mental age (PMA) matched typically developing children (n = 16) completed two endogenous orienting conditions in which the cue exposure time and response preparation time were manipulated within a consistent series of cue-target stimulus onset asynchronies (SOAs). Results:, Participants with ASD displayed facilitation effects at all SOAs, whereas typically developing children displayed facilitation effects only at shorter SOAs. The magnitude of the facilitation effect was greater for the group with ASD at 400ms SOA. Both groups showed similar effects of condition, with similar patterns of facilitation in both conditions. Conclusion:, Persons with ASD were not slower to read the symbolic cue, as the effect was elicited by brief cues within longer SOAs before target onset. The participants with ASD were also less efficient in using the predictability of the cues to guide responding. The difficulties of participants with ASD on endogenous orienting occur at the response selection level, not the perceptual level. [source] Constituent-morpheme priming: Implications from the morphology of two-kanji compound wordsJAPANESE PSYCHOLOGICAL RESEARCH, Issue 2 2002Terry Joyce Abstract: The diversity in the morphological structure of two-kanji compound words is a matter of special concern for models of the Japanese mental lexicon. This study discusses two proposals for models of the Japanese mental lexicon ,Hirose's (1992, 1994, 1996) hypotheses and a Japanese lemma-unit version of the multilevel interactive-activation framework , in terms of their ability to cope with this diversity. As the proposals make different predictions concerning constituent-morpheme priming, patterns of facilitation were examined in two experiments with five word-formation principles as experimental conditions. Experiment 1, using the long stimulus onset asynchrony (SOA) of 3000 ms employed by Hirose (1992), only found significant differences between the first- and second-element conditions in one of the word-formation conditions. Experiment 2, using a short SOA of 250 ms, confirmed the pattern of priming obtained in Experiment 1. These results are more consistent with the prediction from the Japanese lemma-unit model. [source] Loudness summation and the mismatch negativity event-related brain potential in humansPSYCHOPHYSIOLOGY, Issue 1 2006Attila Oceák Abstract Infrequently omitting a sound from a repetitive sequence elicits the mismatch negativity (MMN) ERP response when the stimulus onset asynchrony (SOA) is less than 200 ms. We contrasted two alternative explanations of omission MMN. (1) Each sound starts a separate temporal integration process. Omissions violate the constancy of the temporal structure within the integration window. (2) Sounds preceding an omission are perceived to be louder than those followed by a sound within the integration period, because omissions allow the full stimulus aftereffect to be included in perceived loudness. We varied the SOA between 117 and 217 ms. For this case, the temporal structure explanation predicts that no MMN will be elicited, whereas the loudness summation explanation predicts that MMN will be elicited. MMN was elicited by tone omissions with random SOA, suggesting that loudness summation plays an important role in the elicitation of omission MMN. [source] Effect of quetiapine on cognitive function in schizophrenia: a mismatch negativity potentials studyACTA NEUROPSYCHIATRICA, Issue 1 2009Guo-zhen Yuan Objective:, The purpose of this study was to investigate whether the effects of quetiapine on abnormalities of early auditory processing in patients with schizophrenia were reflected by mismatch negativity (MMN). Methods:, Subjects were 23 patients with schizophrenia and 23 controls. Psychopathology was rated in patients with the Positive and Negative Syndrome Scale (PANSS) at baseline and after 4-week and after 8-week treatments with quetiapine. Auditory stimuli for event-related potentials consisted of 100 ms/1000 Hz standards, intermixed with 100 ms/1500 Hz frequency deviants and 250 ms/ 1000 Hz duration deviants. A stimulus onset asynchrony of each was 300 ms. Electroencephalograph was recorded at Fz. BESA 5.1.8 was used to perform data analysis. MMN waveforms were obtained by subtracting waveforms elicited by standards from those elicited by frequency- or duration-deviant stimuli. Results:, Quetiapine decreased all PANSS scores. Patients showed smaller mean amplitudes of frequency and duration MMN at baseline than did controls. A repeated measure analysis of variance with sessions (i.e. baseline and 4- and 8-week treatments) and MMN type (frequency versus duration) as within-subject factors revealed no significant MMN type or MMN type × session main effect for MMN amplitudes (for MMN type: F = 0.704, df = 1, p = 0.403; for MMN type × session: F = 0.299, df = 2, p = 0.796). Session main effect was significant (F = 3.576, df = 2, p = 0.031). Least square difference tests showed significant differences between MMN amplitudes at 8 weeks and those at both baseline (p = 0.025) and 4 weeks (p = 0.020). MMN amplitudes at 8 weeks were higher than those at baseline. Conclusions:, Quetiapine improved the amplitudes of MMN after the 8-week treatment. MMN offers objective evidence that treatment with the quetiapine may ameliorate preattentive deficits in schizophrenia. [source] | |||||||||||||