Effects of certainty, modality shift and guess outcome on evoked potentials and reaction times in chronic schizophrenics

1978 ◽  
Vol 8 (1) ◽  
pp. 81-93 ◽  
Author(s):  
Rolf Verleger ◽  
Rudolf Cohen
Keyword(s):  
Reaction Time ◽  
Evoked Potentials ◽  
Reaction Times ◽  
Random Order ◽  
Verbal Information ◽  
Group Interactions ◽  
Chronic Schizophrenics ◽  
Modality Shift ◽  
Normal Controls

SynopsisEvoked potentials and reaction times were obtained from chronic schizophrenics and normal controls to light and sound stimuli presented in random order. In the ‘ certain’ condition subjects were told what the next stimulus would be, in the ‘uncertain’ condition they were asked to guess. Amplitudes were usually larger for normals than for schizophrenics, for ‘uncertain’ than for ‘certain’ conditions, and in cross- than in ipsimodal stimulus-sequences. The effect of certainty was stronger in normals across 4 leads; so was the effect of modality shift at vertex. While these findings replicate earlier results from acute schizophrenics, no condition x group interactions could be found in the reaction time measures.Two additional results were interpreted as showing basically different attitudes with respect to the predictability of events: (1) there was a slow positivity between the verbal information and the following stimuli which was largest for schizophrenics in the conditions of certainty; (2) while normals showed long-term habituation only in N1- but not in P3-amplitudes, the reverse was true for schizophrenics.

From Simple to Complex or Vice Versa: Sequence Effects on the Detection of Embedded Figures

Perception ◽  
1997 ◽  
Vol 26 (1_suppl) ◽  
pp. 247-247
Author(s):  
I Ludwig
Keyword(s):  
Reaction Time ◽  
Error Rate ◽  
Reaction Times ◽  
Random Order ◽  
Error Rates ◽  
Presentation Order ◽  
The Other ◽  
Embedded Figures ◽  
Sequence Effects ◽  
Mean Reaction Time

In a series of studies concerning part - whole perception we have investigated effects of perceptual learning, and of systematically varied presentation orders on the detection of embedded figures. In the present study the effects of increasing and decreasing complexity orders on detection performance are reported. Stimuli were 170 pairs of whole and part figures. Half of them were positive items, ie the searched part was contained in the (simultaneously presented) whole. The other half were negative items, ie the searched part was not contained in the whole. The difficulty of all figure pairs was determined from earlier data. On the basis of these difficulty parameters three presentation orders were created: (1) increasing difficulty (from simple to complex), (2) decreasing difficulty (from complex to simple), and (3) randomised order. Sixty subjects performed each of these tasks in three sessions separated by one week. Effects of practice and samples were balanced by permutating the order of the three tasks. The reaction times and error rates for all presentations were registered. The results showed marked differences between the three tasks: The lowest mean reaction time was obtained in the presentation order with increasing difficulty. Error rate, on the other hand, was lowest in the decreasing-difficulty presentation order. For the random-order presentation error rate and reaction time was in between the other orders. Furthermore, differences in benefit from practice were observed between the three orders of difficulty. Results are discussed with respect to the question of how efficient search strategies may be learned and whether one can learn to bend the rules of Gestalt organisation if required.

Functional Locus of Intensity Effects in Choice Reaction Time Tasks

2009 ◽  
Vol 23 (3) ◽  
pp. 126-134 ◽  
Author(s):  
Piotr Jaśkowski ◽  
Izabela Szumska ◽  
Edyta Sasin
Keyword(s):  
Reaction Time ◽  
Evoked Potentials ◽  
Response Selection ◽  
Visual Stimuli ◽  
Reaction Times ◽  
Auditory Stimuli ◽  
Response Choice ◽  
Selection Processes ◽  
Functional Locus ◽  
Readiness Potentials

Long reaction times (RT) paradoxically occur with extremely loud auditory stimuli ( Van der Molen & Keuss, 1979 , 1981 ) or with ultrabright and large visual stimuli ( Jaśkowski & Włodarczyk, 2006 ) when the task requires a response choice. Van der Molen and Keuss (1981 ) hypothesized that this effect results from an arousal-driven elongation of response-selection processes. We tested this hypothesis using visual stimuli and chronopsychophysiological markers. The results showed that the latency of both early (P1 recorded at Oz) and late (P300) evoked potentials decreased monotonically with intensity. In contrast, the latency of stimulus-locked lateralized readiness potentials (LRP) abruptly increased for the most intense stimuli, thus mirroring the reaction time–intensity relationship. Response-locked LRPs revealed no dependency on intensity. These findings suggest that the processes responsible for the van der Molen-Keuss effect influence processing stages that are completed before the onset of LRP. The van der Molen-Keuss effect likely occurs later than those represented by early sensory potentials. This is in keeping with the hypothesis of van der Molen-Keuss.

P300 and Reaction-Time Measures in Senile Dementia of the Alzheimer Type

1991 ◽  
Vol 159 (3) ◽  
pp. 410-414 ◽  
Author(s):  
P. A. Williams ◽  
G. H. Jones ◽  
M. Briscoe ◽  
R. Thomas ◽  
P. Cronin
Keyword(s):  
Reaction Time ◽  
Evoked Potentials ◽  
Cognitive Processing ◽  
Auditory Evoked Potentials ◽  
Response Selection ◽  
Senile Dementia ◽  
Reaction Times ◽  
Reaction Time Task ◽  
Alzheimer Type ◽  
Stimulus Evaluation

Auditory evoked potentials were recorded in a choice reaction-time task. This test paradigm elicited the attention-related P300 component and was used to study cognitive processing. Compared with age-matched controls, 17 patients with dementia of the Alzheimer type were shown to have significantly longer reaction times as well as delayed latencies of several components of the auditory evoked potentials. The fractional increase in the reaction times was much greater than that of the P300 peak latency. The latter is commonly accepted as an index of stimulus-evaluation time. These findings suggest a delay in both response selection and stimulus evaluation.

Contextual Effects on Choice Reaction Time and Accuracy in Acute and Chronic Schizophrenics Impairment in Selective Attention or in the Influence of Prior Learning?

1991 ◽  
Vol 159 (3) ◽  
pp. 415-421 ◽  
Author(s):  
Steven H. Jones ◽  
David R. Hemsley ◽  
Jeffrey A. Gray
Keyword(s):  
Reaction Time ◽  
Selective Attention ◽  
Choice Reaction Time ◽  
Contextual Effects ◽  
Error Rates ◽  
Prior Learning ◽  
Left Hand ◽  
Cue Validity ◽  
Chronic Schizophrenics ◽  
Normal Controls

Two hypotheses were tested concerning the nature of the cognitive dysfunction in schizophrenia: (a) that there is a broadening of selective attention; and (b) that there is an impairment in associational learning. RDC-diagnosed acute and chronic schizophrenics and normal controls carried out a choice reaction time (RT) task in which conflict between the correct response to a target (a letter in the centre of a computer screen) and that cued by simultaneously presented flankers (two letters either side of the target) increased RT. For 80 (‘valid’) trials, flankers and targets were consistent in the response cued (pressing a button with either left or right hand); on 8 (‘invalid’) trials they conflicted. On invalid trials there was a slowing of RT, and an increase of errors for left-hand responses. Chronic schizophrenics showed the same reactions to cue validity as normal controls, both groups differing significantly from acute schizophrenics. For the latter, the RT data supported hypothesis (b), but the error rates appeared to support hypothesis (a).

Evoked Potentials in Reaction Time with a Variable Foreperiod

1973 ◽  
Vol 25 (3) ◽  
pp. 323-334 ◽  
Author(s):  
John Boddy
Keyword(s):  
Reaction Time ◽  
Evoked Potentials ◽  
Contingent Negative Variation ◽  
Random Sequence ◽  
Reaction Times ◽  
Warning Signal ◽  
Auditory Warning

The reaction times (RTs) of 12 subjects were recorded in a design where a visual or auditory warning signal preceded an auditory RT signal by one of four short foreperiods 500, 750, 1000 or 1250 ms long, which occured in a random sequence. For the 16 trials at each foreperiod, with each modality of warning signal, the average of the 2-s long EEG samples following the warning signal was computed so that the record showed the scalp recorded (vertex–-left mastoid) evoked potentials (EPs) to both warning and RT signals, and also the contingent negative variation or expectancy wave occurring during the foreperiod. Differences between RTs with different foreperiods were not reflected in negatively correlated differences in the amplitude of the RT signal EPs, taking the major positive going deflection between peaks N1 and P2 at mean latencies of 126 and 231 msec after the RT signal. Furthermore RT signal EPs preceded by a warning signal were highly attenuated in amplitude relative to control EPs which were not preceded by a warning signal, whether or not an RT response was required. This was despite the fact that alerted RTs were slightly faster than non-alerted RTs, so that these findings contradict previous findings associating augmented EPs with responding versus not responding and with speeded RTs. However, it was also found that RT signal EP amplitudes were greater with the more effective modality of warning signal than the less effective, which was consistent with previous findings. The divergence from previous findings when comparing EPs preceded by a warning with those having no prior warning is tentatively accounted for in terms of persisting physiological refractoriness following the warning signal EP.

scholarly journals Comparison of Reaction Response Time between Hand and Foot Controlled Devices in Simulated Microsurgical Testing

2014 ◽  
Vol 2014 ◽  
pp. 1-8 ◽  
Author(s):  
Marcel Pfister ◽  
Jaw-Chyng L. Lue ◽  
Francisco R. Stefanini ◽  
Paulo Falabella ◽  
Laurie Dustin ◽  
...  
Keyword(s):  
Reaction Time ◽  
Simple Reaction Time ◽  
Reaction Times ◽  
Random Order ◽  
Medical Professionals ◽  
Clinical Correlation ◽  
Level Of Education ◽  
Time Test ◽  
The Mean ◽  
Reaction Time Test

Purpose. We hypothesized that reaction times (RTs) for a switch release are faster for hand-controlled than for foot-controlled switches for physiological and anatomical reasons (e.g., nerve conduction speed). The risk of accidental trauma could be reduced if the surgeon reacted quicker and therefore improve the surgical outcome.Method. We included 47 medical professionals at USC. Demographics and handedness were recorded. Under a microscope, a simple reaction time test was performed, testing all extremities multiple times in a random order. Additionally, a subjective questionnaire was administered.Results. The mean RTs for hands are 318.24 ms±51.13 and feet328.69±48.70. The comparison of hand versus foot showed significant shorter RTs for the hand (P=0.025). Partially significant differences between and within the experience level groups could be demonstrated by level of education (LE) and microscopic surgeries/week (MSW) (P=0.57–0.02). In the subjective questionnaire, 91.5% (n=43/47) of test subjects prefer to use hand controls.Conclusion. Our data show that the RT for hands is faster than feet. Similarly the subjective questionnaire showed a greater preference for hand actuation. This data suggest a hand-controlled ophthalmic instrument might have distinct advantages; however, clinical correlation is required.

Retrieval from Memory or Procedural Strategies for Addition Problems

2011 ◽  
Vol 70 (1) ◽  
pp. 35-39 ◽  
Author(s):  
Muriel Fanget ◽  
Catherine Thevenot ◽  
Caroline Castel ◽  
Michel Fayol
Keyword(s):  
Reaction Times ◽  
Long Term Memory ◽  
Verbal Reports ◽  
Term Memory ◽  
Simple Addition ◽  
Memory Traces ◽  
Addition Problem ◽  
Retrieval From Memory ◽  
Calculation Procedures

In this study, we used a paradigm recently developed ( Thevenot, Fanget, & Fayol, 2007 ) to determine whether 10-year-old children solve simple addition problems by retrieval of the answer from long-term memory or by calculation procedures. Our paradigm is unique in that it does not rely on reaction times or verbal reports, which are known to potentially bias the results, especially in children. Rather, it takes advantage of the fact that calculation procedures degrade the memory traces of the operands, so that it is more difficult to recognize them when they have been involved in the solution of an addition problem by calculation rather than by retrieval. The present study sharpens the current conclusions in the literature and shows that, when the sum of addition problems is up to 10, children mainly use retrieval, but when it is greater than 10, they mainly use calculation procedures.

Modeling Within-Person Variance in Reaction Time Data of Older Adults

GeroPsych ◽  
2011 ◽  
Vol 24 (4) ◽  
pp. 169-176 ◽  
Author(s):  
Philippe Rast ◽  
Daniel Zimprich
Keyword(s):  
Reaction Time ◽  
Cognitive Aging ◽  
Reaction Times ◽  
Reaction Time Task ◽  
Reaction Time Data ◽  
Scale Model ◽  
Time Data ◽  
Time Task ◽  
The Mean ◽  
Second Wave

In order to model within-person (WP) variance in a reaction time task, we applied a mixed location scale model using 335 participants from the second wave of the Zurich Longitudinal Study on Cognitive Aging. The age of the respondents and the performance in another reaction time task were used to explain individual differences in the WP variance. To account for larger variances due to slower reaction times, we also used the average of the predicted individual reaction time (RT) as a predictor for the WP variability. Here, the WP variability was a function of the mean. At the same time, older participants were more variable and those with better performance in another RT task were more consistent in their responses.

The Level of Reaction Time Determines the ERP Correlates of Auditory Negative Priming

2006 ◽  
Vol 20 (3) ◽  
pp. 186-194 ◽  
Author(s):  
Susanne Mayr ◽  
Michael Niedeggen ◽  
Axel Buchner ◽  
Guido Orgs
Keyword(s):  
Reaction Time ◽  
Negative Priming ◽  
Effect Size ◽  
Priming Effect ◽  
Reaction Times ◽  
Negative Priming Effect ◽  
Episodic Retrieval ◽  
Time Level ◽  
Fast Reactions ◽  
Priming Condition

Responding to a stimulus that had to be ignored previously is usually slowed-down (negative priming effect). This study investigates the reaction time and ERP effects of the negative priming phenomenon in the auditory domain. Thirty participants had to categorize sounds as musical instruments or animal voices. Reaction times were slowed-down in the negative priming condition relative to two control conditions. This effect was stronger for slow reactions (above intraindividual median) than for fast reactions (below intraindividual median). ERP analysis revealed a parietally located negativity of the negative priming condition compared to the control conditions between 550-730 ms poststimulus. This replicates the findings of Mayr, Niedeggen, Buchner, and Pietrowsky (2003) . The ERP correlate was more pronounced for slow trials (above intraindividual median) than for fast trials (below intraindividual median). The dependency of the negative priming effect size on the reaction time level found in the reaction time analysis as well as in the ERP analysis is consistent with both the inhibition as well as the episodic retrieval account of negative priming. A methodological artifact explanation of this effect-size dependency is discussed and discarded.

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