Amphetamine and the adenosine A2A antagonist KW-6002 enhance the effects of conditional temporal probability of a stimulus in rats.

As the length of foreperiod preceding an imperative signal increases, reaction time decreases and anticipatory (prior to the signal) responding increases. The authors designed a task to dissociate the effect of elapsing time in the foreperiod and conditional temporal probability of the imperative stimulus. The effects of 2 drugs--amphetamine and KW-6002--known to enhance the effect of foreperiod were compared. Three groups of rats were trained to respond to an auditory signal presented at 1 of 3 foreperiods, unpredictable from trial to trial. The length of preparation time was different for each group, but conditional temporal probability was the same. Reaction times were faster as a function of increased preparation time, whereas anticipatory responses were strongly modulated by conditional probability. Both amphetamine and KW-6002 speeded reaction times and increased anticipatory responding. The pattern of behavior was consistent with the suggestion that they enhanced the motor preparatory effects of conditional probability rather than speeded a timing process. The authors concluded that preparation time and expectancy (conditional temporal probability of an imperative signal) have differential effects on performance and that amphetamine and KW-6002 enhance the effect of expectancy. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The dynamics of cognition and action: Mental processes inferred from speed-accuracy decomposition.

The interpretation of reaction time (RT) data requires strong assumptions about how Ss trade accuracy for speed of performance and about whether there is a discrete or continuous transmission of information from one component process to the next. Conventional RT and speed–accuracy trade-off procedures are not, by themselves, sufficiently powerful to test these assumptions. However, the deficiency can be remedied in part through a new speed–accuracy decomposition technique. The technique uses a hybrid mixture of (a) conventional RT trials in which Ss must process a given test stimulus with high accuracy and (b) peremptory response-signal trials in which Ss must make prompted guesses before stimulus processing has been finished. Data from this "titrated RT procedure" are then analyzed in terms of a parallel sophistication-guessing model, under which normal mental processes and guessing processes are assumed to race against each other in producing overt responses. With the model, the amount of partial information that Ss have accumulated about a test stimulus can be estimated at each intermediate moment during a reaction time trial. An application of speed–accuracy decomposition to 5 studies of word recognition illustrates the potential power of the technique. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Perceptual-motor expectancies interact with covert visual orienting under conditions of endogenous but not exogenous control.

Investigated whether the interaction between endogenous cueing and stimulus/response (S/R) would be obtained if attention was controlled exogenously, using 16 Ss. Central and peripheral cues were used to endogenously or exogenously direct the S's attention to the location at which an increase or decrease in the size of a peripheral object was most likely to occur. For each S, one size change was more likely to occur than the other, and the task was choice reaction time (RT; expansion/contraction). S/R probability (particular size change) interacted with cue condition (valid, neutral, and invalid) when the cues were central (endogenous), but the 2 variables were additive when the cues were peripheral (exogenous). Data suggest that controlled allocation of attention in response to a peripheral cue involves qualitatively different mechanisms from those associated with endogenous generation of an expectancy. (French abstract) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Serial position and set size in short-term memory: The time course of recognition.

Subjects viewed sequentially presented lists of 3–6 words, which were followed by a recognition probe. Memory retrieval speed (dynamics) and strength were measured in an interruption speed–accuracy trade-off (SAT) procedure and a collateral reaction time (RT) procedure. In SAT, item strengths depended on serial position, but only two retrieval speeds were observed: a fast rate for the last item in the study list (a case of immediate repetition between study and test) and a slow rate for all other items that was independent of serial position and set size. Serial-position-dependent strengths and set-size-dependent criterion shifts accounted for standard RT patterns that have been taken as evidence for serial scanning in short-term memory. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Use of partial stimulus information in response processing.

We examined the reaction time (RT) benefit that is obtained when salient features of the stimulus set and response set correspond. Components of the event-related brain potentials were used to measure the timing of stimulus-related and response-related processes in order to determine the locus of this effect. Of particular importance was the development of a new index of selective response preparation, the corrected motor asymmetry (CMA). We found no evidence for the use of preliminary, partial stimulus information in response preparation. These results suggest that the benefit is located primarily in response selection processes and probably reflects a more efficient algorithm for stimulus-response translation. Also, we found trial-to-trial variability in the duration of response selection to be the major determinant of variability in RT, whereas the durations of subsequent response-related processes were relatively invariant. Implications of these results for discrete and continuous models of choice reaction performance are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of stimulus intensity on the lateralized readiness potential.

Information-processing models differ about whether stimulus intensity affects the speed of motor processes involved in response activation and execution. Previous studies of intensity are reviewed, but they are not decisive on this point because they have used indirect approaches requiring strong assumptions. Two experiments examined the effects of stimulus intensity on the lateralized readiness potential (LRP), a measure of hand-specific response activation. In Experiment 1, visual stimulus intensity influenced the time from stimulus onset to LRP onset but not the time from LRP onset to the keypress response. In Experiment 2, auditory stimulus intensity did not influence either of these time intervals, although it did influence the time from stimulus onset to the N100 and P300 components of the evoked potential. The results indicate that stimulus intensity does not influence the duration of motor processes in choice reaction time tasks. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The modulation of somatosensory evoked potentials during the foreperiod of a forewarned reaction time task

During the foreperiod of a forewarned reaction time (RT) task reflexes in the executing limb increase to a lesser extent than those in the contralateral limb. This is possibly due to input modulation. The present study investigates the possibility of cutaneous sensory modulation during motor preparation by studying the amplitudes of somatosensory evoked potentials (SEPs). Eighteen subjects performed a forewarned RT task with the same fingers as the ones which were electrically stimulated. SEPs evoked during the 4 sec preparatory period were compared to those evoked during movement execution and during the resting period after the motor response respectively. During response execution most SEP components showed smaller amplitudes, i.e., they were gated, which agrees with other studies. In the first part of the foreperiod no SEP modulation was observed. Towards the end of the foreperiod, 500 msec before the response stimulus (RS), the amplitude of the contralateral parietal N70-P100 was significantly decreased, while the P45-N70 showed a similar tendency. However, at the same time the P100-N140 was increased in amplitude. The decrease of the intermediate latency components towards the end of the foreperiod is discussed in terms of gating, while the increase in the long latency component is discussed with respect to a decrease in RT on trials where the fingers were stimulated just before the RS, pointing to the role of attentional mechanisms.     

The effects of immediate stimulus repetition on reaction time and event-related potentials in tasks of different complexity.

Examined the effect of immediate stimulus repetition in lexical decision, face recognition, letter search, face/nonface discrimination, and word/number discrimination tasks using reaction time (RT), accuracy, and event-related brain potential (ERP) measures. Repetition facilitated performance in all tasks and for all stimulus types. However, ERPs were strongly affected by repetition only in lexical decision, face recognition, and letter search, when relatively long stimulus analysis and decision making processes were required. The ERP repetition effect consisted of a significant increase in P300 amplitude and a shortening of its latency. Repetition also resulted in the attenuation of a negative component that was tentatively identified as N400. These results suggest that immediate repetition facilitates stimulus identification and eliminates the need for stimulus analysis processes including access to semantic memory while making categorical decisions. While both factors affected RT, ERPs were modulated primarily by the elimination of the need to access to semantic memory and by the consequent speeding of categorical decision processes. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Foreperiod duration, range, and ordering effects on acoustic LRT in normal speakers

One quantitative measure of vocal motor control is phonation onset latency relative to presentation of an external stimulus in a reaction time task. However, variables within the design of reaction time experiments can affect laryngeal reaction time (LRT) values. The present study examines effects of foreperiod characteristics on LRT for normal speakers. Foreperiod is the interval between presentation of warning and response cues. LRT was affected by absolute foreperiod duration, by the average foreperiod duration of a block of trials, and by the ordering and range of foreperiods within a block of trials. Results are discussed with respect to foreperiod effects on the subjective expectancy and objective probability of occurrence of the response cue and on the timing of neurophysiologic processes. Control of subjective effects is critical to assessment of neurophysiologic constraints on LRT.     

Incertitude temporelle, probabilité conditionnelle du signal de réponse et apprentissage d'une tache de temps de reaction simple chez le chat.

Conducted an auditory reaction time (RT) experiment with 11 cats. For an irregular series, with a rectangular distribution of frequencies, a clear decreasing gradient between RT and foreperiod duration was observed which implicated the importance of the objective distribution of conditional probabilities during the foreperiod. The nonlinear relationship between RT and this objective distribution is discussed. The effect of time uncertainty under conditions of constant conditional probability ("nonaging" foreperiods) was indicated by a progressively increasing relationship between RT and foreperiod duration. Ss demonstrated either of 2 starting strategies during learning which produced either an increasing or decreasing effect of time uncertainty on RT. Results show that an intervening adjustment was made by each S during learning which suggests that the reduction of temporal uncertainty was accompanied by a progressive adaptation of a preparatory mechanism to the fluctuations of objective probability. (18 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

La prise de décision rapide en situation de choix dichotomique: Une approche intégrée qui tient compte de l'amorce et de l'exécution de la réponse.

Reviews models of response performance developed to explain the relation among overall reaction time (RT), motor RT, spatial precision of response, and accuracy of response. Emphasis is on the compromise between RT and response accuracy in choice situations and the compromise between movement speed and spatial precision in decisions involving dichotomous choices. An integrated model that considers that both RT and movement time can be modified as an S adapts to the demands of a given task is proposed. The model also allows for the prediction of speed, accuracy, and RT strategies for a particular decision-making situation. Recent research that supports the integrated response performance model is presented. (English abstract) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A random-walk model of accuracy and reaction time applied to three experiments on pigeon visual discrimination.

A random-walk model of visual discrimination is described and applied to reaction time (RT) distributions from three discrete-trial experiments with pigeons. Experiment 1 was a two-choice hue discrimination task with multiple hues. Choice percentages changed with hue discriminability; RTs were shortest for the least and most discriminable stimuli. Experiments 2 and 3 used go/no-go hue discriminations. Blocks of sessions differed in reward probability associated with a variable red stimulus in Experiment 2 and with a constant green stimulus in Experiment 3. Changes in hue had a large effect on response percentage and a small effect on RT; changes in reward shifted RT distributions on the time axis. The “random-walk, pigeon” model applied to these data is closely related to Ratcliff's diffusion model (Ratcliff, 1978; Ratcliff & Rouder, 1998). Simulations showed that stimulus discriminability affected the speed with which evidence accumulated toward a response threshold, in line with comparable effects in human subjects. Reward probability affected bias, modeled as the amount of evidence needed to reach one threshold rather than the other. The effects of reward probability are novel, and their isolation from stimulus effects within the decision process can guide development of a broader model of discrimination. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Effects of task variables on the amplitude and phase-locking of auditory gamma band responses in human

The present study was designed to assess the effects of stimulus certainty and motor task-relevance on auditory transient 40-Hz or gamma band responses. To study the effects of these factors in a balanced design, auditory event-related potentials (ERPs) of 9 young adults were recorded in a passive listening, simple reaction task, and choice-reaction task (target tone probability = 0.5) conditions. Amplitude and phase-locking of event-related gamma activity were analyzed separately at the level of single sweeps by applying a method that allows the independent quantification of phase synchronization between consecutive single responses. Major results demonstrated that (1) During auditory stimulus processing discernible gamma oscillation bursts were observed in three time windows of the poststimulus epoch: early (0-120) ms, middle (120-250 ms) and late (250-400 ms). (2) Early gamma response amplitudes were significantly largest for highly expected motor-task stimuli, whereas the phase-locking did not depend on either of the two variables. (3) The phase-locking of late gamma responses, however, was significantly stronger to targets than to nontargets. These results indicate that auditory gamma responses are functionally involved in the processing of task variables such as stimulus certainty and motor-task relevance. It is also demonstrated that single gamma response amplitude and phase-locking have independent functional significance as being affected in a different manner by different task conditions.     

Souplesse-inertie mentale et jugement de sens.

Studied the effects of cognitive styles (including mental flexibility, field dependence–field independence, perseverance, and responsiveness to stimulus variation) on the speed of verbal comprehension. Human subjects: 98 male and female French adults (university students). Each S's comprehension was assessed using a sentence completion task followed by a meaning judgment task. Cognitive styles were evaluated using a test of mental flexibility by M. Carlier (1973), the Embedded Figures Test by H. A. Witkin et al (1971), the Test de Persévération (Perseverance Test) by R. Zazzo and M. Stambak (1969), and the Test of Developed Designs by G. Tourette (1989). Differences in reaction time (RT) to sentence completion and meaning-judgment tests were evaluated according to cognitive styles. An analysis of variance (ANOVA) and other statistical tests were used. (English abstract) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The temporal dynamics of visual search: Evidence for parallel processing in feature and conjunction searches.

Feature and conjunction searches have been argued to delineate parallel and serial operations in visual processing. The authors evaluated this claim by examining the temporal dynamics of the detection of features and conjunctions. The 1st experiment used a reaction time (RT) task to replicate standard mean RT patterns and to examine the shapes of the RT distributions. The 2nd experiment used the response-signal speed-accuracy trade-off (SAT) procedure to measure discrimination (asymptotic detection accuracy) and detection speed (processing dynamics). Set size affected discrimination in both feature and conjunction searches but affected detection speed only in the latter. Fits of models to the SAT data that included a serial component overpredicted the magnitude of the observed dynamics differences. The authors concluded that both features and conjunctions are detected in parallel. Implications for the role of attention in visual processing are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Motor coactivation revealed by response force in divided and focused attention.

Four experiments examined effects of bimodal stimulation on response force (RF) in addition to reaction time (RT). In a divided-attention task (Exps 1–3), Ss were asked for a speeded response to either a visual or an auditory signal. In unimodal signal trials, either a visual or auditory signal was presented alone, and in redundant-signals trials, both signals were presented simultaneously. The same stimulus arrangement was used in a focused-attention task (Exp 4), but Ss had to withhold their response when an auditory signal was presented alone. In all experiments, the fastest RTs were attained in redundant-signals trials. In addition, RF was largest in redundant-signals trials, especially in the divided-attention task, suggesting a motor coactivation hypothesis. The results indicate that the type of stimulation influences not only when a response is initiated but also how the response is executed. This finding challenges the view, commonly held in mental chronometry, that late motoric processes remain untouched by experimental manipulations. A detailed analysis of the relationship between RT and RF revealed that these variables are not inherently redundant measures, and therefore, RF recording may supplement the traditional RT measurement in mental chronometry. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Serial retrieval processes in the recovery of order information.

The retrieval of temporal order and item information from short-term memory (STM) are examined with the cued-response speed–accuracy trade-off (CR-SAT) procedure and a complementary reaction time (RT) task. The retrieval of order information was examined with a 2-alternative forced-choice (2AFC), relative judgment of recency (JOR) task. Analyses of the pattern of mean RT, RT accuracy, and the overall shape of the RT distribution for correct JORs suggest that order information is retrieved by a serial retrieval mechanism. Analyses of SAT retrieval functions confirm that order information is retrieved by a recency-based, serial retrieval process. These results contrast with previous SAT analyses of STM item recognition (B. McElree and B. A. Dosher, see record 1990-09049-001), which indicate that item information is retrieved by a parallel or direct-access mechanism. The dissociation between item and order information retrieval was further documented in a 2AFC item recognition SAT study. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

évolution des effets d'une préparation motrice induite par amor?age in fonction de la quantité de pratique.

The goal of the present experiment is to assess the effects of motor preparation on reaction time (RT) as a function of practice. We used a priming procedure to induce different levels of motor preparation. In reaction to a visual signal, the 16 participants had to respond with a flexion or an extension of the right or left wrist. Each participant performed 6,120 successful trials divided into 34 experimental series. The first analysis of RT as a function of the type of cue (valid, neutral, or invalid) suggested that the time needed (a) to inhibit the prepared response and (b) to program the required one, remains stable throughout practice. A second analysis on the amount of information to be processed according to type of cue (0.42, 2.00, and 3.58 bits) indicated that central processing speed did not vary with practice. Indeed, only RT for the 0 bit condition decreased during the first 720 trials, suggesting that only the peripheral processes were influenced in early learning. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Motor processes in simple, go/no-go, and choice reaction time tasks: A psychophysiological analysis.

Psychophysiological measures were used to compare the response preparation and response execution processes of modified versions of F. C. Donders's (1868/1969) classic simple, go/no-go, and choice reaction time tasks. On all measures, differences between tasks were minimal prior to test stimulus onset, supporting the idea of equivalent motor preparation for the 3 tasks. In addition, the psychophysiological measures indicated that the time from the onset of motor processing to the keypress response was also approximately constant across tasks. These results support the assumption that the mean duration of motor processes can be invariant across simple, go/no-go, and choice tasks, at least for the present modified versions of these tasks. The findings emphasize the utility of psychophysiological measures for both examining preparatory processes preceding stimulus onset and for localizing effects on reaction time. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Visual offsets facilitate saccadic latency: Does predisengagement of visuospatial attention mediate this gap effect?

Saccadic reaction time (RT) is reduced when a fixation stimulus is extinguished 200 msec before a target appears. An attentional predisengagement theory (APT) may explain this gap effect: When covert attention is engaged (e.g., on fixation), the saccadic system is inhibited and RT is delayed; when the attended stimulus is extinguished, attention is disengaged, the inhibition is removed, and RT is facilitated. In 3 experiments covert attention was endogenously or exogenously cued to an object on the vertical meridian. Onset of a saccadic target on the horizontal meridian could be preceded by the offset of an attended or unattended object. Contrary to APT, RTs were identical after attended and unattended offsets. Results suggest that the gap effect has 2 components, and covert visual attention plays no role. One component is motor system preparation; the other is a fixation offset effect specific to the oculomotor system. (PsycINFO Database Record (c) 2010 APA, all rights reserved)