The detection of automated perimetric stimuli in ocular disease

Automated perimetry has made viable a rapid threshold examination of the visual field and has reinforced the role of perimetry in the diagnostic procedure. The aim of this study was twofold: to isolate the influence of certain extraneous factors on the sensitivity gradient, since these might limit the early detection and accurate monitoring of visual field loss and to investigate the efficacy of certain novel combinations of stimulus parameters in the detection of early visual field loss. The work was carried out with particular reference to glaucoma and to ocular hypertension. The effects of media opacities on the visual field were assessed by forward intraocular light scatter (n= 15) and were found to mask diffuse glaucomatous visual field loss and underestimate focal loss. Correction of the visual field indices for the effects of forward intraocular light scatter (n= 26) showed the focal losses to be, in reality, unaffected. Measurements of back scatter underestimated forward intraocular light scatter (n= 60) and the resultant depression of the visual field. Perimetric sensitivity improved with patient learning (n= 25) and exhibited eccentricity- and depth-dependency effects whereby improvements in sensitivity were greatest for peripheral areas of the field and for those areas which initially demonstrated the lowest sensitivity. The effects of practice were retained over several months (n= 16). Perimetric sensitivity decreased during prolonged examination due to fatigue effects (n&61 19); these demonstrated a similar eccentricity-dependency, being greatest for eccentricities beyond 30o. Mean sensitivities over the range of adaptation levels employed obeyed the Weber-Fechner law (n= 10) and, as would be expected, were independent of pupil size. No relationship was found between short-term fluctuation and adaptation level. Detection of diffuse glaucomatous visual field loss was facilitated using a size III stimulus of duration 200msec at an adaptation level of 31.5asb, compared with a size III stimulus of duration 100msec at an adaptation level of 4asb (n= 20). In a pilot study (n= 10), temporal summation was found to be higher in glaucomatous patients compared with age-matched controls, although the difference was not statistically significant.

Development of visual evoked responses to tritan,red-green and luminance stimuli in human infants

The principal aim of this work was to investigate the development of the S-cone colour-opponent pathway in human infants aged 4 weeks to 6 months. This was achieved by recording transient visual evoked responses to pattern-onset stimuli along a tritanopic confusion axis (tritan stimuli) at and around the adult isoluminant match. For comparison, visual evoked responses to red-green and luminance-modulated stimuli were recorded from the same infants at the same ages. Evoked responses were also recorded from colour-normal adults for comparison with those of the infants. The transient VEP allowed observation of response morphology as luminance differences were introduced to the chromatic stimuli. In this way, an estimate of isoluminance was possible in infants. Estimated isoluminant points for a group of six infants aged 6 to 10 weeks closely approximated the adult isoluminant match. This finding has implications for the use of photometric isoluminance in infant work, and suggests that photopic spectral sensitivity is similar in infants and adults. Abnormalities of the visual evoked responses to tritan, red-green and luminance-modulated stimuli in an infant with cystic fibrosis are reported. The results suggest abnormal function of the retino-striate visual pathway in this infant, and it is argued that these may be secondary to his illness, although data from more infants with cystic fibrosis are needed to clarify this further. A group of nine healthy infants demonstrated evoked responses to tritan stimuli by 4 to 10 weeks and to red-green stimuli by 6 to 11 weeks post-term age. Responses to luminance-modulated stimuli were present in all nine infants at the earliest age tested, namely 4 weeks post-term. The slightly earlier age of onset of evoked responses to tritan stimuli than for red-green may be explained by the relatively lower cone contrast afforded by red-green stimuli. Latency of the evoked response to both types of chromatic stimuli and to luminance-modulated stimuli decreased with age at a similar rate, suggesting that the visual pathways transmitting luminance and chromatic information mature at similar rates in young infants.

Effect of fatigue on consumers' advertising processing

Huge advertising budgets are invested by firms to reach and convince potential consumers to buy their products. To optimize these investments, it is fundamental not only to ensure that appropriate consumers will be reached, but also that they will be in appropriate reception conditions. Marketing research has focused on the way consumers react to advertising, as well as on some individual and contextual factors that could mediate or moderate the ad impact on consumers (e.g. motivation and ability to process information or attitudes toward advertising). Nevertheless, a factor that potentially influences consumers’ advertising reactions has not yet been studied in marketing research: fatigue. Fatigue can yet impact key variables of advertising processing, such as cognitive resources availability (Lieury 2004). Fatigue is felt when the body warns to stop an activity (or inactivity) to have some rest, allowing the individual to compensate for fatigue effects. Dittner et al. (2004) defines it as “the state of weariness following a period of exertion, mental or physical, characterized by a decreased capacity for work and reduced efficiency to respond to stimuli.’’ It signals that resources will lack if we continue with the ongoing activity. According to Schmidtke (1969), fatigue leads to troubles in information reception, in perception, in coordination, in attention getting, in concentration and in thinking. In addition, for Markle (1984) fatigue generates a decrease in memory, and in communication ability, whereas it increases time reaction, and number of errors. Thus, fatigue may have large effects on advertising processing. We suggest that fatigue determines the level of available resources. Some research about consumer responses to advertising claim that complexity is a fundamental element to take into consideration. Complexity determines the cognitive efforts the consumer must provide to understand the message (Putrevu et al. 2004). Thus, we suggest that complexity determines the level of required resources. To study this complex question about need and provision of cognitive resources, we draw upon Resource Matching Theory. Anand and Sternthal (1989, 1990) are the first to state the Resource Matching principle, saying that an ad is most persuasive when the resources required to process it match the resources the viewer is willing and able to provide. They show that when the required resources exceed those available, the message is not entirely processed by the consumer. And when there are too many available resources comparing to those required, the viewer elaborates critical or unrelated thoughts. According to the Resource Matching theory, the level of resource demanded by an ad can be high or low, and is mostly determined by the ad’s layout (Peracchio and Myers-Levy, 1997). We manipulate the level of required resources using three levels of ad complexity (low – high – extremely high). On the other side, the resource availability of an ad viewer is determined by lots of contextual and individual variables. We manipulate the level of available resources using two levels of fatigue (low – high). Tired viewers want to limit the processing effort to minimal resource requirements by making heuristics, forming overall impression at first glance. It will be easier for them to decode the message when ads are very simple. On the contrary, the most effective ads for viewers who are not tired are complex enough to draw their attention and fully use their resources. They will use more analytical strategies, looking at the details of the ad. However, if ads are too complex, they will be too difficult to understand. The viewer will be discouraged to process information and will overlook the ad. The objective of our research is to study fatigue as a moderating variable of advertising information processing. We run two experimental studies to assess the effect of fatigue on visual strategies, comprehension, persuasion and memorization. In study 1, thirty-five undergraduate students enrolled in a marketing research course participated in the experiment. The experimental design is 2 (tiredness level: between subjects) x 3 (ad complexity level: within subjects). Participants were randomly assigned a schedule time (morning: 8-10 am or evening: 10-12 pm) to perform the experiment. We chose to test subjects at various moments of the day to obtain maximum variance in their fatigue level. We use Morningness / Eveningness tendency of participants (Horne & Ostberg, 1976) as a control variable. We assess fatigue level using subjective measures - questionnaire with fatigue scales - and objective measures - reaction time and number of errors. Regarding complexity levels, we have designed our own ads in order to keep aspects other than complexity equal. We ran a pretest using the Resource Demands scale (Keller and Bloch 1997) and by rating them on complexity like Morrison and Dainoff (1972) to check for our complexity manipulation. We found three significantly different levels. After having completed the fatigue scales, participants are asked to view the ads on a screen, while their eye movements are recorded by the eye-tracker. Eye-tracking allows us to find out patterns of visual attention (Pieters and Warlop 1999). We are then able to infer specific respondents’ visual strategies according to their level of fatigue. Comprehension is assessed with a comprehension test. We collect measures of attitude change for persuasion and measures of recall and recognition at various points of time for memorization. Once the effect of fatigue will be determined across the student population, it is interesting to account for individual differences in fatigue severity and perception. Therefore, we run study 2, which is similar to the previous one except for the design: time of day is now within-subjects and complexity becomes between-subjects

Impaired sensitivity to dynamic stimuli in poor readers of a regular orthography

The mappings from grapheme to phoneme are much less consistent in English than they are for most other languages. Therefore, the differences found between English-speaking dyslexics and controls on sensory measures of temporal processing might be related more to the irregularities of English orthography than to a general deficit affecting reading ability in all languages. However, here we show that poor readers of Norwegian, a language with a relatively regular orthography, are less sensitive than controls to dynamic visual and auditory stimuli. Consistent with results from previous studies of English-readers, detection thresholds for visual motion and auditory frequency modulation (FM) were significantly higher in 19 poor readers of Norwegian compared to 22 control readers of the same age. Over two-thirds (68.4%) of the children identified as poor readers were less sensitive than controls to either or both of the visual coherent motion or auditory 2Hz FM stimuli. © 2003 Elsevier Science (USA). All rights reserved.

Interval timing in children:effects of auditory and visual pacing stimuli and relationships with reading and attention variables

Motor timing tasks have been employed in studies of neurodevelopmental disorders such as developmental dyslexia and ADHD, where they provide an index of temporal processing ability. Investigations of these disorders have used different stimulus parameters within the motor timing tasks which are likely to affect performance measures. Here we assessed the effect of auditory and visual pacing stimuli on synchronised motor timing performance and its relationship with cognitive and behavioural predictors that are commonly used in the diagnosis of these highly prevalent developmental disorders. Twenty- one children (mean age 9.6 years) completed a finger tapping task in two stimulus conditions, together with additional psychometric measures. As anticipated, synchronisation to the beat (ISI 329 ms) was less accurate in the visually paced condition. Decomposition of timing variance indicated that this effect resulted from differences in the way that visual and auditory paced tasks are processed by central timekeeping and associated peripheral implementation systems. The ability to utilise an efficient processing strategy on the visual task correlated with both reading and sustained attention skills. Dissociations between these patterns of relationship across task modality suggest that not all timing tasks are equivalent.

A working memory bias for alcohol-related stimuli depends on drinking score

We tested 44 participants with respect to their working memory (WM) performance on alcohol-related versus neutral visual stimuli. Previously an alcohol attentional bias (AAB) had been reported using these stimuli, where the attention of frequent drinkers was automatically drawn toward alcohol-related items (e.g., beer bottle). The present study set out to provide evidence for an alcohol memory bias (AMB) that would persist over longer time-scales than the AAB. The WM task we used required memorizing 4 stimuli in their correct locations and a visual interference task was administered during a 4-sec delay interval. A subsequent probe required participants to indicate whether a stimulus was shown in the correct or incorrect location. For each participant we calculated a drinking score based on 3 items derived from the Alcohol Use Questionnaire, and we observed that higher scorers better remembered alcohol-related images compared with lower scorers, particularly when these were presented in their correct locations upon recall. This provides first evidence for an AMB. It is important to highlight that this effect persisted over a 4-sec delay period including a visual interference task that erased iconic memories and diverted attention away from the encoded items, thus the AMB cannot be reduced to the previously reported AAB. Our finding calls for further investigation of alcohol-related cognitive biases in WM, and we propose a preliminary model that may guide future research. © 2012 American Psychological Association.

Optical imaging of retina in response to grating stimuli in cats

We examined the intrinsic signals in response to grating stimuli in order to determine whether the light-evoked intrinsic signals of the retina are due to changes in the photoreceptor activities induced by the image projected on to the retina or are due to neural activities of the inner retina. The retinas of the left eye of 12 cats under general anesthesia were examined by a functional imaging fundus camera. Near infrared light was used to monitor the reflectance changes (RCs) of the retina. Vertical grating were used to stimulate the retina at 4 Hz. The spatial frequencies of the gratings were 0.05, 0.11, 0.22, 0.43, 0.86, 1.73, and 3.46 cycles/degree (cpd). Ten images were averaged and used to analyze the RCs to obtain the peak value (PV) of a two dimensional fast Fourier transfer of the RCs. The wavefront aberrations (WA) were measured with a compact wavefront aberrometer and the spatial modulation transfer function (MTF) of the eye was calculated. The retinal reflectance image had a grating pattern. The PV of the spatial sensitivity curve was highest at low spatial frequencies (0.05 and 0.11 cpd), and the sensitivity decreased steeply with an increase in the spatial frequency. RCs were not detectable at 3.46 cpd. The MTF decreased gradually with increases in the spatial frequencies and was 0.68 at 3.46 cpd. The reflectance pattern of the retinal intrinsic signal elicited by grating stimuli of different spatial frequencies was different from that of the MTF. This suggests that the intrinsic signal represents not only the response of the photoreceptors but also other neuronal or vascular changes in the retina.

Comparative study of dexamethasone and vancomycin release behavior from stimuli-sensitive microgel aqueous dispersions

Stimuli-sensitive microgels of poly(N-isopropylacrylamide-co-acrylic acid) (designated as P(NIPAAm-co-AA)) were prepared through precipitation polymerization. Their capacity to load and release different drugs under different conditions, including physiological, in a controlled manner was analyzed. Two drugs were assayed and compared: dexamethasone and vancomycin. The prepared microgel particles show good thermosensitivity. In addition, the amount of cross-linker used in the preparation of the microgels does not greatly influence the drug-release capability of P(NIPAAm-co-AA)), but the amount of drug used to load the microgels did result in bigger amounts of drug released afterwards. These results imply potential application of prepared stimuli-sensitive microgel dispersions as drug-delivery systems and tissue engineering materials.

Elevated striatal and decreased dorsolateral prefrontal cortical activity in response to emotional stimuli in euthymic bipolar disorder:no associations with psychotropic medication load

To examine abnormal patterns of frontal cortical-subcortical activity in response to emotional stimuli in euthymic individuals with bipolar disorder type I in order to identify trait-like, pathophysiologic mechanisms of the disorder. We examined potential confounding effects of total psychotropic medication load and illness variables upon neural abnormalities.

Impaired executive functioning in subclinical compulsive checking with ecologically valid stimuli in a working memory task

We previously showed that working memory (WM) performance of subclinical checkers can be affected if they are presented with irrelevant but misleading information during the retention period (Harkin and Kessler, 2009, 2011). The present study differed from our previous research in the three crucial aspects. Firstly, we employed ecologically valid stimuli in form of electrical kitchen appliances on a kitchen countertop in order to address previous criticism of our research with letters in locations as these may not have tapped into the primary concerns of checkers. Secondly, we tested whether these ecological stimuli would allow us to employ a simpler (un-blocked) design while obtaining similarly robust results. Thirdly, in Experiment 2 we improved the measure of confidence as a metacognitive variable by using a quantitative scale (0–100), which indeed revealed more robust effects that were quantitatively related to accuracy of performance. The task in the present study was to memorize four appliances, including their states (on/off), and their locations on the kitchen countertop. Memory accuracy was tested for the states of appliances in Experiment 1, and for their locations in Experiment 2. Intermediate probes were identical in both experiments and were administered during retention on 66.7% of the trials with 50% resolvable and 50% irresolvable/misleading probes. Experiment 1 revealed the efficacy of the employed stimuli by revealing a general impairment of high- compared to low checkers, which confirmed the ecological validity of our stimuli. In Experiment 2 we observed the expected, more differentiated pattern: High checkers were not generally affected in their WM performance (i.e., no general capacity issue); instead they showed a particular impairment in the misleading distractor-probe condition. Also, high checkers’ confidence ratings were indicative of a general impairment in metacognitive functioning. We discuss how specific executive dysfunction and general metacognitive impairment may affect memory traces in the short- and in the long-term.

An investigation of psychological and physiological changes apparently elicited by musical stimuli

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Speech and non-speech stimuli in the prediction of early reading skills:the influence of processing demands and response-type

Purpose: Both phonological (speech) and auditory (non-speech) stimuli have been shown to predict early reading skills. However, previous studies have failed to control for the level of processing required by tasks administered across the two levels of stimuli. For example, phonological tasks typically tap explicit awareness e.g., phoneme deletion, while auditory tasks usually measure implicit awareness e.g., frequency discrimination. Therefore, the stronger predictive power of speech tasks may be due to their higher processing demands, rather than the nature of the stimuli. Method: The present study uses novel tasks that control for level of processing (isolation, repetition and deletion) across speech (phonemes and nonwords) and non-speech (tones) stimuli. 800 beginning readers at the onset of literacy tuition (mean age 4 years and 7 months) were assessed on the above tasks as well as word reading and letter-knowledge in the first part of a three time-point longitudinal study. Results: Time 1 results reveal a significantly higher association between letter-sound knowledge and all of the speech compared to non-speech tasks. Performance was better for phoneme than tone stimuli, and worse for deletion than isolation and repetition across all stimuli. Conclusions: Results are consistent with phonological accounts of reading and suggest that level of processing required by the task is less important than stimuli type in predicting the earliest stage of reading.

Target spatial frequency determines the response to conflicting defocus- and convergence-driven accommodative stimuli

Asthenopia, or visual fatigue, is a frequent complaint from observers of stereoscopic three-dimensional displays. It has been proposed that asthenopia is a consequence of anomalous oculomotor responses generated by conflict between accommodative and convergence stimuli. The hypothesis was examined by measuring accommodation and convergence continuously with a Shin-Nippon SRW5000 infrared autorefractor and a limbus tracking device. Subjects viewed a high contrast Maltese Cross target at three levels of Gaussian filter target blur under conditions of relatively low- and high-conflict between accommodation and convergence stimuli, the latter inducing the sensation of stereopsis. Under the low-conflict conditions accommodation was stable, but convergence-driven accommodation was dominant when the target was extremely blurred. Under the high-conflict conditions the role of convergence-driven accommodation increased systematically with the degree of target blur. It is proposed that defocus-driven accommodation becomes weak when the target comprises low spatial frequency components. Large accommodative overshoots to step stimuli that are not blurred or only mildly blurred were consistently observed and are attributed to the initial accommodative response being convergence-driven. Whereas the possibility that high-conflict conditions are a cause of asthenopia has been previously reported, this is the first evidence that they specifically affect accommodative responses while viewing stereoscopic displays. © 2005 Elsevier Ltd. All rights reserved.