Preparatory Interval Research Articles

Filling the preparatory interval with temporal information or visual noise: crossover effect in schizophrenics and controls.

Three variants of a simple reaction time task with regular and irregular series of different preparatory intervals (PIs) were presented to schizophrenics and a control group of alcoholics and normals: the visual warning signal (WS) either (1) remained fixed, (2) shrank at a constant rate, or (3) changed in size erratically. Time information provided by shrinking WSs reduced the average reaction time in all groups and attenuated the crossover effect (COE) of schizophrenics, although even here more schizophrenics than controls had COE-scores greater than or equal to 25 msec. Erratically changing WSs introduced the COE in controls. Within groups the COE was not related to general response speed, age, duration of hospitalization, or medication. Results are interpreted as indicating that schizophrenics eschew controlled anticipatory processes on the basis of WS- and PI-information which are crucial for motor preparation when PIs are too long to allow an automatic perceptual grouping of warning and imperative stimulus. This may also occur in controls when time estimation is impeded by distraction.

Effects of age on motor preparation and restructuring

Age-related decrements in motor plan restructuring were investigated. In this experiment older and younger adults performed a discrete aiming task that involved responses that were precued and responses that were modified at the time of an imperative signal. On 75% of the trials, the precue specified the response stimulus (valid trials) with respect to the movement parameters of arm (left or right) and direction (toward or away). On the remaining 25% of the trials, the response stimulus was different from the precue (invalid trials) in that the subject was required to modify a planned movement by changing the arm to be used and/or the direction of movement. The older subjects were slower than the younger in both the valid and invalid trials. Across preparatory intervals (PI) of 500, 1,000, 1,500, and 2,000 msec, older, but not younger subjects exhibited less reaction time cost for restructuring the motor plan for the direction-change condition than for the other parameter change conditions. Since there was little apparent cost of restructuring, these findings suggest that older adults did not prepare the direction of movement, and thus found it temporally more efficient to alter direction than arm or arm and direction combined.

The embedded set procedure. Comment on Galbraith, MacCrimmon, and Steffy.

The reaction-time crossover phenomenon discovered by Rodnick and Shakow has come to be studied mainly with the embedded isotemporal sets procedure and indexed by the difference in reaction time to regular and irregular trials at a 7-second preparatory interval (PI). A 1983 report in this journal by Galbraith et al. (J Nerv Ment Dis 171:670-675) demonstrated that the magnitude of crossover at this PI was influenced by the duration of the preparatory interval immediately prior (PPI) to the first trial of the 7-second isotemporal blocks. Secondary analyses reported here extend the examination of PPI influences and indicate: a) that the crossover phenomenon as assessed in the embedded sets procedure is due mainly to the very slow reaction time to the first trial of the 1-second isotemporal blocks; and b) that crossover in this paradigm is partially due to uncontrolled PPI influences across the 1-, 3-, and 7-second embedded blocks. These are further reasons for returning to the original Rodnick-Shakow method as Galbraith et al. recommended.

Sequence of preparatory set for response movement.

Electromyographic reaction times (EMG-RTs) of the right biceps brachii muscle were examined for two movement patterns, elbow flexion and forearm supination, in 8 healthy male subjects under simple and complex RT conditions with varied preparatory intervals (PIs): 0, 200, 400, 600, and 800 msec. In the simple RT condition, the subject was informed of the movement patterns to be performed prior to beginning the trials. In the complex RT condition the subject had to choose one of the two movement patterns at the time of the presentation of a warning signal. The results indicated that: (1) compared with the simple RT condition a delay of about 100 msec. in over-all mean EMG-RT was observed at PI = 0 msec. in the complex RT condition; (2) the difference of over-all mean EMG-RT between the two RT conditions disappeared when PI = 400 msec.; and (3) the difference in EMG-RTs between flexion and supination in the complex RT condition became the same as that in the simple RT condition when PI = 700 msec. It is assumed that the preparatory set for response movements is organized in an order, resulting in the differentiation of RT.

Preparatory interval effects on the reaction time performance of introverts and extraverts

This study examined the effect of preparatory interval (PI) lenght on the reaction time (RT) of extraverts (Es) and introverts (Is). In addition to displaying a significantly slower overall mean RT than Es, Is also tended to be more adversely affected by longer PI duration ( P = 0.06). That is, unlike Es, Is tended to show a much greater increase in RT to an 8-sec PI duration as compared to a 4-sec PI duration. Examination of the influence of psychoticism (P) and neuroticism (N) effects on the performance of Es and Is indicated that N had no effect for this sample of subjects. However, high levels of P tended to lead to a decrease in the overall mean RT of ES while it tended to increase the RT scores of Is. P did not, however, have an effect on the PI responding of Es and Is. Discussion of these results centered on certain parallels between the performance of introverts and schizophrenic subjects concerning deficits in attention during RT performance.

Impact of time estimation on the crossover effect in schizophrenia

To test the role of time estimation in the crossover effect (COE), reaction times (RTs) of schizophrenic, alcoholic, and normal subjects were collected in two conditions: a standard visual RT task with different preparatory intervals in regular or irregular series, and a time information condition with the intervals filled by a visual countdown analogue. In the standard condition, the COE was found not only for schizophrenics but also for alcoholics. Time information reduced RTs in all groups, but not the average COE in schizophrenics. The relationship between RTs and simultaneously collected event-related potentials was examined.

A comparison of the effects of fixed versus variable foreperiods on anticipatory cardiac deceleration prior to an exercise task in grade school children

Children's heart rate responses in anticipation of a signalled exercise task were examined. The use of fixed (15 s) vs varaible (10, 15 or 20 s) preparatory intervals (PI) was compared. The analysis across all subjects indicated that the children exhibited a stable deceleration immediately prior to the exercise task. A difference was found between the fixed and variable PI's. During the period immediately before the exercise task, those subjects receiving the variable PI exhibited a decrease across trials in the size of the anticipatory heart rate deceleration. The children receiving the fixed PI showed an increase across trials in the size of the deceleration.

Two Conditions of Uncertainty and Their Effects on Reaction Time of Mentally Retarded Adolescents

The effects of uncertainty of occurrence and uncertainty of time—use of catch-trials and preparatory intervals—in simple reaction time (RT) trials were investigated with nonhandicapped and mentally retarded subjects. The results showed that: (a) Catch-trials impaired the performance of this task, (b) catch-trials did not differentiate among groups of subjects, and (c) preparatory intervals differently affected RT latencies of nonhandicapped and mentally retarded subjects. Interpretation of findings suggests that the use of catch-trials induced preparation decrements and that preparation decrements may explain in part the poorer RT performance of retarded subjects.

Forearm blood flow responding prior to voluntary isometric contraction.

ABSTRACTSrain‐gauge plethysmography was used to study phasic forearm blood flow (FBF) responding, which has been presumed to occur in human subjects prior to voluntary muscular contraction. In a two‐group design, 10 subjects performed a 7‐s, fixed‐foreperiod, reaction‐time (RT) task in which static handgrip was the required RT response; 10 additional subjects in a High Incentive (HI) condition performed a more stressful delayed avoidance task. Bilateral FBF and HR were computer‐sampled over the preparatory interval (PI) and transformed into second‐by‐second measures. Mean FBF estimates were also obtained by averaging over the entire PI. HI subjects were found to manifest significantly greater mean FBF prior tro motor responding than did subjects performing the nonstressful RT taks. Such preparatory FBF responding was task‐specific, occurring only in the Arm to be performing the signalled RT response. Furthermore, this task‐specific, phasic increase in averaged mean FBF was observed to occur in subjects' left and right arms. Trend analysis and visual inspection of second‐by‐second FBF waveforms demonstrated a gradual decline in flow rate over the course of the preparatory interval under all experimental conditions. HR responding manifested the characteristic triphasic waveforms, with higher heart rate and augmentation of acceleratory and terminal deceleratory components exhibited by the HI group. the findings suggest that human phasic FBF responding can be influenced by motoric and motivational factors as well as by demands for sensory intake behavior.

Clinical and etiological implications of a specific attention deficit in schizophrenia.

Forty-seven psychiatric inpatients, including 26 schizophrenics and 21 nonschizophrenics, were measured on four clinical factors (chronicity, premorbid adjustment, reported symptomatology, and diagnosis) and four indices of reaction time (RT) performance (mean RT, RT variance, and redundancy-associated deficit [RAD] at 3- and 7-second preparatory intervals [PIs] ). Each clinical factor was analyzed in turn as a dependent variable in multiple regression analyses. The RT indices comprised the predictor set in each multiple regression. RAD at 7-second PI is related to chronicity for psychiatric patients in general and for schizophrenic patients in particular. Diagnosis and premorbid adjustment are related primarily to mean RT. No evidence was found that RAD is an artifact of high intertrial variance or long RT latencies, but intertrial variance does play a role in moderating the implications of RAD. The different correlations within schizophrenic and nonschizophrenic groups suggest a) that the Elgin Scale has a different meaning when used with schizophrenics than with nonschizophrenics, and b) that it is not useful to treat schizophrenic and nonschizophrenic disorders on the same continuum. The results in general suggest that the vulnerability factor thought to be associated with RAD militates for greater chronicity across different types of patients. The RAD effect within schizophrenics is nevertheless relatively greater than within other patients.

Prepreparatory Interval Effects on Redundancy Deficit Reaction Time Patterns in Schizophrenic and Normal Subjects Using the Embedded-Set Procedure

The relative influence of genuine "redundancy deficit" and the artifactual effects of prepreparatory interval on measures of the redundancy deficit reaction time pattern (faster reaction time on trials with long preparatory intervals when the interval is of predictable vs. unpredictable length) was investigated in a study using the "embedded-set" procedure. Twenty normal and 20 schizophrenic subjects received two series of reaction time trials containing embedded sets (blocks) of four isotemporal 1-, 3-, and 7-second trials. The 7-second blocks (the blocks of interest for the calculation of redundancy deficit) were preceded by long prepreparatory intervals in one condition and by short intervals for the second. Each subject received both conditions, with the orders counterbalanced. The results indicated redundancy deficit for both schizophrenics and normals with short prepreparatory intervals, but in neither group with long prepreparatory intervals. This suggests that redundancy deficit in the embedded-set procedure (which is normally heavily biased with short prepreparatory intervals) may be more related to the enhancing effect of short prepreparatory intervals on the first (unpredictable) trial of the set than to impaired performance on the fourth (predictable) trial. The finding of similar effects in both schizophrenic and normal subjects raises questions about the specificity of redundancy deficit to schizophrenic reaction time performance. The results were discussed with reference to the original "long run" reaction time procedure for studying the same phenomenon, and theoretical issues related to the interpretation of results from the two procedures were considered.

Phasic heart rate responses and cardiac cycle time in auditory choice reaction time

This study investigated the cardiovascular-behavioral interaction under short and long stimulus interval conditions. In addition, the cardiovascular-behavioral interaction was studied as affected by cardiac cycle duration. Fourteen subjects performed a choice reaction time (RT) task employing a mixed speed-accuracy tradeoff design in which reactions were paced to coincide with a signal that occurs randomly at either 200 or 500 msec after the reaction stimulus. The preparatory interval between a warning stimulus and a lead-reaction stimulus complex was also varied (2 vs. 4.5 sec). Anticipatory deceleration ocurred within the 4.5 sec interval but not in the 2 sec interval. The depth of anticipatory deceleration did not discriminate between fast and slow reactions; but an earlier shift from deceleration to acceleration was associated with fast reactions. The effect of stimulus timing relative to the R-wave of the electrocardiogram was also analysed. Meaningful stimuli tended to produce cardiac slowing as previously described in the literature. Early occurring stimuli prolong the cycle of their occurrence more than late occurring stimuli. The latter prolong the subsequent cycle. Cardiac cycle time effects were absent for unattended stimuli. The results of anticipatory deceleration suggested that the depth of deceleration was regulated by time-uncertainty and speed-accuracy criterion.

Reaction-time crossover in psychiatric outpatients

Simple reaction time (SRT) was measured in schizophrenic, bipolar affective disorder, and never-psychotic outpatients to determine the specificity of SRT crossover to schizophrenia. A crossover pattern like that reported in other studies was found among the schizophrenics, but the average curve was not different from that of the other groups. Schizophrenics tended to have higher rates of crossover at the 7-second preparatory interval (47% vs. 17%–28%) but not substantially so. These data question the specificity of this behavioral trait to schizophrenics.

Preparatory interval influences on reaction-time of elderly adults.

The influence of regularity of preparatory interval (PI) on simple reaction-time (RT) in elderly persons was studied in a sample of 25 women between 65 and 88 years of age. RTs to regular and variable PIs of 1, 3, 7, 9, and 13 seconds were compared using Steffy's embedded isotemporal blocks method. The advantage of PI regularity was lost at 13 sec, where performance was faster for irregular trials. The RT-PI functions were similar to those found by Botwinick and his associates who used Shakow's paradigm, even though overall RT was slower in this sample. The similarity of results across the two paradigms suggest that the point of RT function crossover is interval dependent and unrelated to response latency in elderly adults.

Learning disability: an inability to sustain attention.

Administered a complex reaction time task to 47 learning-disabled and 41 control children, aged 8 to 10 1/2. The preparatory interval between a warning and act light was manipulated for length and regularity. Groups differed only as a function of number of trials. It appears that the inability to sustain attention over time, rather than momentary inattentiveness, distinguished the two groups.

Age and simple reaction time.

Although simple reaction time (RT) to a tone showed a statistically significant increase between 18 and 93 years of age in a sample of 220 men and women, the amount of increase was slight, less than 2 msec/decade. Consequently, the appreciable slowing of more typical behavior with age does not seen attributable to some general process in the central nervous system as has been argued. This degree of stability found for simple RT with age, unexpected from the body of previous work, may reflect equivalence of age groups and use of optimal RT technique. In a second study eight old participants (73 to 84 years) matched on the optimal technique with eight young participants (18 to 24 years) were markedly slower with a long constant preparatory interval but not with elimination of timing cues. Together, the two studies show that simple high level of preparation was either easy of impossible to attain. Behavioral slowing with age can result from ineffective control processes.

Locus of reaction time change in schizophrenics and normal subjects.

Simple reaction time (RT) obtained from trials presented in isotemporal series (preparatory intervals of the same duration) were partitioned into premyographic and myographic time components for 20 schizophrenic and 20 normal subjects according to a previously developed procedure. This procedure allowed for an examination of the relative contributions made by these RT components to: a) overall mean reaction time; and b) the crossover pattern of responding as first observed by David Shakow. In addition, a within-subject comparison of the traditional press-release motor task and an alternative press-only motor task was made. Differential predictions were made as to the effect of the task manipulation from: a) the loss of major set; and b) the reactive inhibition interpretational positions. It was found that the schizophrenics' crossover pattern of responding was specific to the press-release task. Furthermore, it was apparent that both premyographic and myographic components of the RT interval contributed to: a) their overall longer mean RTs, as well as b) their increased magnitude of crossover. The results were seen as supporting the view that inhibitory processes triggered by the increased levels of arousal during the isotemporal series are responsible for the schizophrenics' crossover pattern of responding on the press-release task. It was noted that the loss of major set explanation need not be seen as incompatible with a reactive inhibition explanation of the crossover effect.

Load compensating responses of human abdominal muscles.

1. We studied abdominal muscle responses to positive pressure loads applied suddenly to the external airway while subjects held a constant lung volume against steady pressure. The pre-loading holding pressure was 6 cm H(2)O, and the loading pressures were 6 or 12 cm H(2)O lasting for 2 sec.2. Surface electromyograms (e.m.g.) were recorded over the internal oblique, external oblique, and rectus abdominis muscles. The latency and pattern of the e.m.g. reactions were studied by measuring the raw record for each loading trial, and by averaging the rectified e.m.g. for many trials.3. No responses were obtained if subjects were instructed not to respond to the loads. When instructed and trained to maintain their pre-load position in spite of the load, a two-phase compensatory response was found. The initial response (phase I) was 100-300 msec in duration; it was followed by a continuous e.m.g. discharge (phase II) which continued to the offset of the pressure load. Subjects were also trained to make a single respiratory effort as quickly as possible after the load onset or after just an auditory stimulus. These were simple reaction time tasks of a traditional kind and the e.m.g. responses elicited were single, brief bursts.4. For all subjects and experimental conditions the e.m.g. response of the internal oblique occurred first, followed by the external oblique and then the rectus abdominis. For the ;maintain position' task, phase I latencies (internal oblique) averaged 66-90 msec for individual subjects, but for single trials with optimal conditions of practice and preparatory intervals these ranged from 42 to 110 msec with a third of the reactions occurring within 50-60 msec.5. The latencies for reaction time responses to loading were about 6 msec shorter than the phase I latencies. The latency distributions for the two types of responses were similar, and both were affected to the same degree by practice, and changing the length and variability of the preparatory interval. Because of these similarities we suggest that the phase I reaction was a learned response of a ;simple reaction time' type, and not comparable to late stretch reflexes such as the M2 of limb muscles.6. Arm muscle responses to respiratory pressure changes were measured in three subjects under identical conditions used to obtain load reaction times of abdominal muscles. These simple reaction times averaged 61-71 msec, and ranged from 42 to 97 msec. Therefore very short proprioceptive reaction times are not peculiar to the respiratory system, or to load perturbations of the responding muscle.7. Mechanical adjustments of airway pressure and lung volume in response to loading are first expressed at the mouth about 90 msec after abdominal muscle activity begins. In the ;maintain position' task, the accuracy with which pressure and volume adjustments were made during the last 1.5 sec of the loading period approximated that reported in the literature for trained singers holding a tone using constant expiratory pressure.

The left-to-right difference in warned reaction times of finger movements

The electromyographic reaction times (RTs) in bilateral finger movements and their left-to-right (l-r) difference were measured in right-handed subjects under conditions of different preparatory intervals (PIs), i.e., periods between warning and command signal. RTs without warning were always longer than warned RTs with PIs of 2–15 sec. Consistent right or left leading l-r differences occurred for PIs ranging from 2 to 6 or 7 sec, but were reduced for longer PIs. Significant l-r differences in warned RTs were consistently maintained regardless of the sensory modality of command signals, and even between separately performed right and left movements. In these tests RTs and their l-r difference changed independently. It is suggested that the warning signal acts on RTs and their l-r difference through two separate facilitatory mechanisms in the central information processing.

Anticipatory cardiac deceleration prior to total body movement in grade school children

A total of 16 males (mean age = 10.9 years) were tested on six trials of a signaled, running time task while heart rate was recorded. The preparatory interval varied randomly among 10, 15, or 20 sec. The response consisted of running a distance of 4.62 m. A triphasic heart rate response (deceleration-acceleration-deceleration) occurred following the warning signal. A stable deceleration below pre-stimulus levels was observed during the 5-sec period prior to the respond signal. Heart rate responses were not related to running time.