Effect of pre-adapting spectral stimuli on visual responses

Electroretinograms (ERGs) were recorded following pre-adapting exposures to radiometrically and photometrically matched spectral stimuli. The magnitudes of three aspects of the ERG varied as a function of the pre-adapting wavelength. Longer wavelenght pre-adapting stimuli produced less suppression of the response magnitudes than stimuli from the short wavelenght end of the spectrum. The implications of the findings for display design and cockpit-light-source design and management are discussed.     

Influence of the presentation of remote visual stimuli on visual responses of cat area 17 and lateral suprasylvian area

Single units were recorded extracellularly from area 17 and lateral suprasylvian area (LSSA) in curarized cats. Visual stimuli, usually a 10 degree black spot, were introduced abruptly in the visual field remote from the discharge area of a neuron's receptive field and moved at a speed of about 30 degrees/sec. The effect of these remote stimuli (S2) on the reponse to a restricted visual stimulus (S1) crossing the discharge area was studied. It was found that most units in area 17 were not affected by the presentation of remote stimuli, the remainder being either slightly facilitated or slightly inhibited. In contrast the LSSA neurons were usually inhibited by the presentation of S2: this effect was strong, was present in all classes of LSSA neurons and was independent of the relative directions of movement of S1 and S2. On the basis of these data and those previously obtained from the superior colliculus it is concluded that the way the extrageniculate centres respond to a stimulus abruptly introduced in the visual field is substantially different from that of the striate cortex. Only in the extrageniculate centres a new stimulus, besides exciting the neurons which correspond to the position of the stimulus in the field, concomitantly decreases the responses of neurons located in positions of the visual field remote from that stimulus. Possible behavioral implications of the findings are discussed.     

Cardiac and visual responses to stimuli presented both foveally and peripherally as a function of moving stimuli.

Measured heart rate (HR) and visual fixation responses as indices of attention getting (AG) and attention holding (AH) in 17 15-wk-old infants. The stimulus situation was one in which a brief central stimulus was followed by either a brief peripheral stimulus (AG trials) or a prolonged peripheral stimulus (AH trials). The stimuli for both central and peripheral presentations were moving black and white bar patterns. The speed for the central stimulus was constant over trials and groups (at 6.6°/sec), whereas the peripheral stimuli were either 6.6 or 26°/sec. Results suggest that much of the observed HR change can be accounted for by the AG phase, whereas the AH phase was reflected in the time it took for the cardiac responses to return to prestimulus baseline values. Stimulus speed also affected both attention behaviors; the faster speed produced the greatest HR change. Latency of 1st fixation and duration of looking measures did not show any discrimination between stimuli of different speeds. (12 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Biographical and self-report correlates of female guilt responses to visual erotic stimuli.

Divided 60 female undergraduates into high- and low-sex guilt groups on the basis of their responses to D. L. Mosher's True-False Guilt Inventory. All Ss reported an increase in state of sexual arousal after viewing erotic stimuli. None of the Ss reported any significant difference in state of guilt after viewing the stimuli. Low-sex guilt Ss rated the masturbation, coitus, and petting stimuli as more sexually arousing, better, more pleasant, safer, and more appealing than did high-sex-guilt Ss. (21 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Cardiac and visual responses to moving stimuli presented either successively or simultaneously to the central and peripheral visual fields in 4-month-old infants.

Measured cardiac and visual orienting responses as indices of attention in 41 4-mo-old infants. Two stimulus situations were used. In the 1st situation, the presentation of a peripheral stimulus followed the offset of a central fixation stimulus. In the 2nd situation, the peripheral stimulus came on while the central fixation stimulus was on. Each stimulus comprised a horizontal black and white bar pattern. Corneal reflection was used to monitor infant gaze. The visual-response measure confirmed that with simultaneous presentation the probability of orienting to the peripheral stimulus decreased. The extent of this reduction was determined by the speed difference between the central and peripheral stimuli. The cardiac data indicate that on the trials in which the peripheral stimulus did not elicit lateral eye/head movements the stimulus was still being detected. Thus, cardiac change can reflect attentional processes without evidence of somatic orienting. (24 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of luminance, contrast, and blur on visual acuity

Although previous investigations have reported that changes in background luminance, stimulus contrast, and dioptric blur can each affect visual acuity independently, it has not been shown how these three variables interact to influence visual acuity. This is a particularly important issue if one is interested in predicting how individuals with different refractive characteristics will be able to perform acuity-based tasks in degraded visual environments with low background lighting and contrast levels. To investigate these relations, we conducted a series of experiments in which measurements of visual acuity were obtained for four subjects using Landolt C targets of varying contrast at several background luminances for levels of blur between 0 and 8 diopters (D). Our results show that visual acuity is significantly affected by all three factors, and that their effects are essentially additive. At all luminance and contrast levels, the reduction in visual acuity is greatest for dioptric blur up to 2.0 D, with a more gradual reduction in visual acuity for dioptric blur of greater than 2.0 D. At all blur and luminance levels, visual acuity decreases gradually for contrast levels down to 20%, and decreases sharply for lower contrast levels. Over the range of background luminances we tested (75.0 to 0.075 cd/m2), visual acuity decreases linearly with reductions in luminance. The additive effects of dioptric blur, contrast, and luminance provide a basis for predicting visual acuity-related task performance for individuals in different visual environments. For example, an individual with 6/6 (20/20) visual acuity under high luminance-high contrast conditions will fall to 6/18 (20/60) acuity for low luminance conditions and 6/30 (20/100) for low luminance-low contrast conditions. Similarly, an individual with an uncorrected visual acuity of 6/30 (20/100) under optimal conditions will fall to approximately 6/120 (20/400) under low luminance conditions and 6/240 (20/800) under low luminance-low contrast conditions.     

Effects of motivationally significant stimuli on the regulation of dominant responses.

In 4 experiments, Ss responded as quickly as possible to indicate whether character strings consisted of letters or numbers. Following a warning stimulus that was or was not designated to trigger a motivational–emotional response in particular subgroups (namely, those with high anxiety, discrepant self-concepts, and eating disorders), strings were presented in a central (dominant) location on 75% of the trials or in 1 of 4 peripheral (nondominant) locations. Consistent with hypotheses, response times to peripherally located strings were significantly slower following motivationally significant than following neural warning stimuli. Contrary to hypotheses, such sitimuli did not facilitate responding to centrally located strings. It is proposed that motivationally significant stimuli engender a temporary reduction in control processing that hinders regulation of dominant responses. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of suramin on neuroendocrine and behavioural responses to conditioned fear stimuli

Conditioned fear stimuli suppress motor activity. The fear stimuli suppress vasopressin and facilitate oxytocin and prolactin release. These fear responses are impaired by selective destruction of noradrenergic neurones. Adenosine 5'-triphosphate is co-released from noradrenergic nerve terminals with noradrenaline. Thus the possibility arises that the behavioural and neuroendocrine responses may be mediated by purinergic rather than noradrenergic synapses. We examined whether suramin, an inhibitor of P2 and NMDA receptors, blocks conditioned fear responses. Suramin injected i.c.v. 30 min before testing stimuli impaired conditioned fear responses. The role of purinergic P2 receptors in expression of the behavioural and neuroendocrine responses to conditioned fear stimuli is discussed.     

The effects of learning on the ventilatory responses to inspiratory threshold loading

Progressive threshold loading (PTL) is frequently used to assess inspiratory muscle endurance in health and disease. We and others have noted a systematic increase in endurance with the first few exposures to the task in subjects previously na?ve to PTL, which may not be related to conditioning of the muscles themselves. The purpose of this study was to investigate the mechanisms responsible for this increased endurance by examining the ventilatory responses to 3 PTL tests, each > 24 h apart, in 18 healthy subjects. During PTL, threshold pressure (Pth) was increased by approximately 10% every 2 min until task failure. Subjects were allowed to adopt any breathing pattern. Respiratory muscle strength (maximal inspiratory pressure [PImax]) was unchanged over successive tests while maximal Pth (Pthmax) during PTL increased (69 +/- 17, 77 +/- 16, and 86 +/- 11% of PImax, respectively, p < 0.05) (mean +/- SD), indicating that the increased Pthmax could not be attributed to improved respiratory muscle strength. Breathing pattern changed with successive tests, so that for comparative loads inspiratory time (TI), respiratory frequency (f ), and duty cycle (TI/Ttot) decreased. This change in breathing pattern did not alter respiratory muscle efficiency (respiratory muscle V O2/work), which was similar in each test (2.4 +/- 2.2%), but perceived effort (Borg Score), which was maximal at task failure in each test, decreased at comparative loads with successive tests. Thus, Pthmax during initial tests appeared to be limited by discomfort rather than respiratory muscle function. These findings suggest that the increased Pthmax with successive tests is a consequence of differences in the breathing pattern adopted, reflecting neuropsychological rather than respiratory muscle conditioning. Measurements from PTL should only be used to assess respiratory muscle performance after allowing time for learning.     

Effect of luminance contrast on BOLD fMRI response in human primary visual areas

In this study, we examined the effect of stimulus luminance contrast on blood-oxygenation-level-dependent (BOLD) functional magnetic resonance imaging within human visual cortex (V1 and extrastriate). Between experiments, the calibrated luminance of a single red LED covering 2 degrees of the subject's visual field was changed relative to a constant background luminance. This stimulus provided a different foveal luminance contrast for each experiment. We used an echo planar imaging sequence to collect blood-oxygenation-sensitive images during and in the absence of the presented stimulus. Our results showed that within V1 there was an increase in the spatial extent of activation with increasing stimulus contrast, but no trend was seen within extrastriate. In both V1 and extrastriate, the local mean activation level for all activated image pixels remained constant with increasing luminance contrast. However, when we investigated activated pixels common to all luminance contrast levels, we found that there was an increase in the mean activation level within V1, but not within extrastriate. These results suggest that there is an increase in the activity of cells in V1 with increasing luminance contrast.     

Effects of oral deprivation on responses to subliminal and supraliminal verbal food stimuli.

The effect of 2 kinds of oral deprivation on reactions to a subliminal and supraliminal food stimulus was investigated. Varying hours of food deprivation (1-5 or more) constituted the 1st independent variable; smoking frequency constituted the 2nd. Different groups of Ss were exposed to a word list preceded by: (a) no stimulus, (b) the subliminal stimulus CHEESE, and (c) the supraliminal stimulus CHEESE. The stimulus word was associatively linked to 10 of the words on the recall list. Relative recall of stimulus-related associates was a function of hours of deprivation in the subliminal and supraliminal conditions, and a function of smoking frequency in the subliminal condition. Other nutritional and oral variables were also investigated. (21 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of gaze on apparent visual responses of frontal cortex neurons

Previous reports have argued that single neurons in the ventral premotor cortex of rhesus monkeys (PMv, the ventrolateral part of Brodmann's area 6) typically show spatial response fields that are independent of gaze angle. We reinvestigated this issue for PMv and also explored the adjacent prearcuate cortex (PAv, areas 12 and 45). Two rhesus monkeys were operantly conditioned to press a switch and maintain fixation on a small visual stimulus (0.2 degree x 0.2 degree) while a second visual stimulus (1 degree x 1 degree or 2 degrees x 2 degrees) appeared at one of several possible locations on a video screen. When the second stimulus dimmed, after an unpredictable period of 0.4-1.2 s, the monkey had to quickly release the switch to receive liquid reinforcement. By presenting stimuli at fixed screen locations and varying the location of the fixation point, we could determine whether single neurons encode stimulus location in "absolute space" or any other coordinate system independent of gaze. For the vast majority of neurons in both PMv (90%) and PAv (94%), the apparent response to a stimulus at a given screen location varied significantly and dramatically with gaze angle. Thus, we found little evidence for gaze-independent activity in either PMv or PAv neurons. The present result in frontal cortex resembles that in posterior parietal cortex, where both retinal image location and eye position affect responsiveness to visual stimuli.     

Effects of contrast on attraction of the housefly, Musca domestica, to visual targets

There is evidence that the treatment of bacterial meningitis with antibiotics liberates harmful bacterial products in the subarachnoid space (SAS). This enhances meningeal inflammation and in particular the recruitment of leukocytes into the cerebrospinal fluid (CSF), which has been shown to be more harmful than beneficial in this disease. In this study, we used a rabbit meningitis model based on intracisternal injection of live Streptococcus pneumoniae. Ampicillin (40 mg/kg of body weight given intravenously [i.v.] 16 h after induction of meningitis) caused a fivefold increase in CSF leukocytes over a 4-h period. Inhibition of leukocyte rolling by treatment with the polysaccharide fucoidin (10 mg/kg, i.v.) prevented the enhanced leukocyte extravasation into the SAS and attenuated the leakage of plasma proteins over the blood-brain barrier. These results suggest that certain polysaccharides that block leukocyte rolling have the potential to reduce leukocyte-dependent central nervous system damage in bacterial meningitis.     

Effects of attention on infants' preference for briefly exposed visual stimuli in the paired-comparison recognition-memory paradigm.

This study examined the effect of attention on 3- to 6-mo-olds' responses to briefly exposed visual stimuli. In Study 1, stimuli presented at 2.5 or 5.0 s resulted in a familiarity preference in a subsequent paired-comparison procedure. A novelty preference was found with 10.0- or 20.0-s exposure durations. In Study 2, a Sesame Street movie elicited heart-rate-defined attention phases and stimuli replaced Sesame Street during sustained attention, attention termination, or 5.0 s following attention termination. For 20 and 26-wk-olds, stimuli presented for 5.0 s during sustained attention resulted in a novelty preference similar to that found when exposure time was 20.0 s. The duration of stimulus exposure during sustained attention in the familiarization phase was positively correlated with the preference for the novel stimulus in the paired-comparison procedure. Thus, processing of briefly presented visual stimuli differs depending on the type of attention in which the infant is currently engaged. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Type A and Type B attentional responses to aesthetic stimuli: Effects on mood and performance.

Recent investigations of the Type A (coronary prone) behavior pattern have found that Type A's focus their attention on a central task and actively inhibit attention to peripheral distracting stimuli. This attentional difference has resulted in greater performance for Type A's than for Type B's (noncoronary prone behavior). However, research on aesthetic stimuli suggests that the focused attention of Type A's may not always be adaptive for solving frustrating cognitive tasks, particularly when paying attention to a peripheral stimulus could enhance performance by reducing negative emotions. Simple, predictable, aesthetic stimuli can have a soothing effect, which reduces negative emotions and enhances performance. The present study, conducted with 62 undergraduates (mean age 24 yrs) who had completed the Jenkins Activity Survey for Health Prediction, found that Type B's had improved affect and performance from attending to a soothing peripheral stimulus (simplex melodies) while working on a frustrating cognitive task (anagrams). Neither the performance nor the affect of Type A's was influenced by the simplex music, because they apparently suppressed paying attention to these melodies. (32 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Coordinating responses to aversive stimuli: Introduction to a special section on the development of emotion regulation.

Introduces special section and provides an overview of research on infant and child emotion regulation, beginning with consideration of emotion as a set of responses to particular stimuli, such as aversive events. Emotional responding is noted as occurring simultaneously within each of three response systems, including neurophysiological-biochemical, motor-expressive, and experiential-cognitive domains. Emotion regulation is the process through which activation in one response domain serves to alter, titrate, or modulate activation in another response domain. During the course of development, the child acquires skill not only in responding within domains, but also in coordinating and regulating responses across domains. Mechanisms of development include fortuitous learning, repetition, and active socialization by a caregiver. Individual differences can be observed in the child's capacity for regulation, and major life events can intrude on development, the latter leading to dysregulation of emotional responding. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The effect of dark-rearing, strobe-rearing and acute visual cortex removal on the visual responses in the superficial superior colliculus of the guinea-pig

The interaction of zinc and vitamin A in rats receiving a regional diet of Manaus, supplemented with vitamin A, zinc and zinc and vitamin A was studied. The regional diet was elaborated according to data of Shrimpton and Giugliano (6), for families receiving less than two minimum salaries. The biological test to study the interaction was based on the depletion of zinc and vitamin A in rats in the period of lactation, and a period of repletion where supplements of zinc (0.82 mg%) and vitamin A (94.2 micrograms %) were given, either separately or together, according to the recommendations of the Committee on Laboratory Animal Diets (7). From the results, it was concluded that there was an interaction of these nutrients in terms of mobilization of hepatic vitamin A. Although the regional diet of Manaus did not meet the zinc RDA, the amount present was enough to utilize the available vitamin A. Although the amount of zinc present in the diet, as determined by parameters of bioavilability, such as growth, concentration in organs and zinc-dependent enzymes, was adequately used by the animals, probably due to promoting factors in the diet. The Manaus regional diet needs to be supplemented with vitamin A in order to maintain the hepatic reserves, and with zinc, to maintain the normal levels of vitamin A in plasma.