Effect Of Stimulus Saliency Research Articles

Factors Influencing Saccadic Reaction Time: Effect of Task Modality, Stimulus Saliency, Spatial Congruency of Stimuli, and Pupil Size.

It is often assumed that the reaction time of a saccade toward visual and/or auditory stimuli reflects the sensitivities of our oculomotor-orienting system to stimulus saliency. Endogenous factors, as well as stimulus-related factors, would also affect the saccadic reaction time (SRT). However, it was not clear how these factors interact and to what extent visual and auditory-targeting saccades are accounted for by common mechanisms. The present study examined the effect of, and the interaction between, stimulus saliency and audiovisual spatial congruency on the SRT for visual- and for auditory-target conditions. We also analyzed pre-target pupil size to examine the relationship between saccade preparation and pupil size. Pupil size is considered to reflect arousal states coupling with locus-coeruleus (LC) activity during a cognitive task. The main findings were that (1) the pattern of the examined effects on the SRT varied between visual- and auditory-auditory target conditions, (2) the effect of stimulus saliency was significant for the visual-target condition, but not significant for the auditory-target condition, (3) Pupil velocity, not absolute pupil size, was sensitive to task set (i.e., visual-targeting saccade vs. auditory-targeting saccade), and (4) there was a significant correlation between the pre-saccade absolute pupil size and the SRTs for the visual-target condition but not for the auditory-target condition. The discrepancy between target modalities for the effect of pupil velocity and between the absolute pupil size and pupil velocity for the correlation with SRT may imply that the pupil effect for the visual-target condition was caused by a modality-specific link between pupil size modulation and the SC rather than by the LC-NE (locus coeruleus-norepinephrine) system. These results support the idea that different threshold mechanisms in the SC may be involved in the initiation of saccades toward visual and auditory targets.

Effects of stimulus salience on the magnitude of latent inhibition after compound conditioning.

The effect of stimulus salience on latent inhibition (the retardation of conditioning produced by prior exposure to the event to be used as the conditioned stimulus [CS]) was examined in an experiment using rats as subjects and the conditioned suppression procedure. The stimuli were a more salient light and a less salient tone-rats trained with light as the CS showed more suppression than rats trained with the tone as the CS; and rats tested with tone and light separately after conditioning with a CS consisting of a tone + light compound showed more suppression to the light than the tone. This pattern of results was reversed, however, in subjects given a series of nonreinforced presentations of the tone and the light separately prior to conditioning with the compound. We conclude that latent inhibition develops more readily for the more salient stimulus and that its effects can outweigh those that derive from the intrinsic salience of the stimulus. Theories of latent inhibition that predict, or can accommodate, this conclusion are considered.

Effects of stimulus salience on touchscreen serial reversal learning in a mouse model of fragile X syndrome

Fragile X syndrome (FXS) is the most common inherited form of intellectual disability in males and the most common genetic cause of autism. Although executive dysfunction is consistently found in humans with FXS, evidence of executive dysfunction in Fmr1 KO mice, a mouse model of FXS, has been inconsistent. One possible explanation for this is that executive dysfunction in Fmr1 KO mice, similar to humans with FXS, is only evident when cognitive demands are high. Using touchscreen operant conditioning chambers, male Fmr1 KO mice and their male wildtype littermates were tested on the acquisition of a pairwise visual discrimination followed by four serial reversals of the response rule. We assessed reversal learning performance under two different conditions. In the first, the correct stimulus was salient and the incorrect stimulus was non-salient. In the second and more challenging condition, the incorrect stimulus was salient and the correct stimulus was non-salient; this increased cognitive load by introducing conflict between sensory-driven (i.e., bottom-up) and task-dependent (i.e., top-down) signals. Fmr1 KOs displayed two distinct impairments relative to wildtype littermates. First, Fmr1 KOs committed significantly more learning-type errors during the second reversal stage, but only under high cognitive load. Second, during the first reversal stage, Fmr1 KOs committed significantly more attempts to collect a reward during the timeout following an incorrect response. These findings indicate that Fmr1 KO mice display executive dysfunction that, in some cases, is only evident under high cognitive load.

Overshadowing of geometry learning by discrete landmarks in the water maze: Effects of relative salience and relative validity of competing cues.

The effects of stimulus salience and cue validity in the overshadowing of geometric features of an enclosed arena by discrete landmarks were investigated in rats using the water maze paradigm. Experiment 1 established that in a rhomboid-shaped arena, the acute corner was more salient than the obtuse corner. In Experiment 2, rats were trained to find a submerged platform either in one of the acute, or obtuse, corners. In addition to the information provided by corner angle, the platform was also signaled by the presence of a spherical landmark suspended above the platform for rats in the experimental group. The landmark was a more valid cue for predicting the location of the platform than the angle of the corner. This training resulted in overshadowing of learning about the angle of the corner by the presence of the landmark. The final experiment extended this result by showing that when the predictive validities of the angle and the landmark were matched in the experimental group, learning about geometry was still overshadowed by the presence of landmarks, but only in animals that were trained with the platform at an obtuse, but not acute, corner. These results uniquely demonstrate that learning about geometry can be overshadowed by discrete landmarks, and also that whether overshadowing is observed depends on the stimulus salience and the relative validity of the competing cues. These findings imply that learning based on geometric cues follows the same basic rules that apply to a wide range of other learning paradigms.

Overtraining and reversal learning in the rat: Effects of stimulus salience and response strategies.

Overtraining and reversal learning in the rat: Effects of stimulus salience and response strategies.