Effects Of Delay Interval Research Articles

The effect of delay interval on the feedback control for a turbidostat model

In this paper, we propose a turbidostat model with delay interval on its output using a feedback control law, aiming to investigate how the delay interval affects the feedback control of the model. The delay interval is represented by two parameters, which describe the time delay distributed in a past sub-interval. We first prove the positivity and boundedness of solutions and the permanence of the model. Then, using the input flow rate as a feedback control variable, we discuss the asymptotical stabilization of a given state (i.e., the positive equilibrium) employing the method of Lyapunov functionals. Moreover, we further study the Hopf bifurcations induced by the two delay parameters. Our theoretical and numerical results all show that the delay interval can have a significantly different effect on the dynamics of a turbidostat model from other delay types.

Effect of delay interval on classical eyeblink conditioning in 5-month-old human infants.

Associative learning was evaluated in human infants with simple delay classical eyeblink conditioning. A tone conditioned stimulus (CS) was paired with an airpuff unconditioned stimulus (US) at three different delay intervals (250, 650, and 1,250 ms). Independent groups of healthy, full-term 5-month-old human infants were assigned to these three paired conditions and received two identical training sessions 1 week apart. The two longer delays resulted in associative conditioning, as confirmed by comparison with unpaired control groups. However, only at the 650-ms delay were associative eyeblinks adaptively timed to avoid the airpuff. The delay function at 5 months of age appears much sharper than is observed in adults. Together with the findings of A. H. Little, L. P. Lipsitt, and C. Rovee-Collier (1984), the present study suggests a downward shift in the optimal delay interval for associative eyeblink conditioning between 1 and 6 months of age. However, this delay remains longer than what is typically reported in adults.

The effects of delay interval, intertriai interval, amnestic drugs, and differential outcomes on matching-to-position in rats

A matching-to-position task was used to investigate the effects of numerous variables on spatial working memory in the rat. The primary interest was whether implementing the differential outcomes procedure (DOP), which correlates specific reinforcers with specific discriminative stimuli, would enhance memory performance under a variety of conditions (long delay intervals, short intertrial-intervals [ITIs], amnestic drugs). When working memory was taxed, either by excessive delay intervals or very short ITIs, the DOP did enhance performance. Scopolamine disrupted performance in a delay-dependent manner, regardless of either reinforcement or ITI condition; however, performance was worse in the group that was trained with nondifferential reinforcement. MK-801 also impaired performance, but the effect was different from that obtained with scopolamine. First, the effect of MK-801 was delay independent; second, the greatest disruption of performance was in the group of rats trained with differential reinforcement. These data suggest that scopolamine and MK-801 impair memory performance in very different ways, depending on the nature of the task.

Neonatal medial prefrontal lesions and recovery of spatial delayed alternation in the Rat: Effects of delay interval

We have previously shown that rats given medial prefrontal lesions on postnatal Day 10 show a performance deficit on spatial delayed alternation (2-s delay) when tested between Days 19 and 23, but show recovery of function by Days 27-33 (Freeman & Stanton, 1992). The present study attempted to (a) examine the effects of extending the delay interval from 2 s to 15 or 45 s on the ontogeny of spatial delayed alternation; and (b) determine whether these longer delays would alter the ontogenetic profile of recovery from medial prefrontal damage. Animals were given medial prefrontal lesions (mPFC) or sham surgery on Day 10. They received acquisition training on delayed alternation with a 2-s delay on Day 21 or Day 28, followed by "probe" tests at delays of 15 and 45 s on the following day (Day 22 or Day 29). On Days 21-22 there was an overall effect of lesion at the 2-, 15-, and 45-s delay intervals indicating an early deficit. However, on Days 28-29 there was no effect of lesion at the end of acquisition or at the 15- or 45-s delay intervals. Recovery of memory function by mPFC animals on this task appears to occur during the weanling period regardless of delay interval.

Comparison dimension cues in delayed matching by pigeons: The effect of delay interval and cue-presentation method

Pigeons were trained on a delayed matching task in which a cue (a circle or a triangle) superimposed on the sample stimulus (red or green) signaled whether the test consisted of color or line-tilt comparison stimuli. During probe testing sessions, accuracy was assessed on correctly cued (CO, incorrectly cued (IC), and no-cue (NC) trials. In Experiment 1, accuracy was lower on IC trials than on CC or NC trials. This cuing effect remained constant as the delay interval was increased. In Experiment 2, the cuing effect occurred only when the cue was superimposed on the sample. Experiment 3 revealed that presample and postsample presentation of the cue was ineffective in promoting a cuing effect. The results were inconsistent with a dual coding model that postulates that both prospective and retrospective coding occurs in this task. The data suggested that the cues and sample stimuli were processed and perceived as unitary configurations. Comparison cues do not function independently of the sample when they are superimposed on it during training.

Effects of Delay Interval and Pictorial Cues on a Sentence Imitation Task

40 preschool children performed a sentence imitation task under four conditions (10 subjects in each condition): immediate imitation of auditorily presented stimuli, delayed imitation of auditorily presented stimuli, immediate imitation of auditorily and pictorially presented stimuli, and delayed imitation of auditorily and pictorially presented stimuli. The subjects in the immediate imitation conditions produced fewer total errors and more verbatim responses than the subjects in the delay interval conditions. These findings are discussed in relation to prior findings.

The Effects of Delay Interval on Word Recall and Clustering

The Effects of Delay Interval on Word Recall and Clustering