Stimulus Quality Research Articles

Young without plastic surgery: Perceptual adaptation to the age of female and male faces

Adaptation influences perception not only of simple stimulus qualities such as motion or colour, but also of complex stimuli such as faces. Here we demonstrate contrastive aftereffects of adaptation to facial age. In Experiment 1, participants adapted to either young or old faces, and subsequently estimated the age of morphed test faces with interpolated ages of 30, 40, 50 or 60years. Following adaptation to old adaptors, test faces were classified as much younger when compared to classifications of the same test faces following adaptation to young faces, which in turn caused subjective test face “aging”. These aftereffects were reduced but remained clear even when facial gender changed between adaptor and test faces. In Experiment 2, we induced simultaneous opposite age aftereffects for female and male faces. Overall, these results demonstrate interactions in the perception of facial age and gender, and support dissociable neuronal coding of male and female faces.

Visual word recognition: Evidence for global and local control over semantic feedback.

Two lexical decision experiments examined the joint effects of stimulus quality, semantic context, and cue-target associative strength when all factors were intermixed in a block of trials. Both experiments found a three-way interaction. Semantic context and stimulus quality interacted when associative strength between cue-target pairs was strong, and the interaction was eliminated when the strength was weak. These results support a role for a local mechanism that relies on trial specific information, in addition to a mechanism that makes use of global information available across a block of trials. The absence of an interaction between the joint effects of semantic context and stimulus quality is attributed to blocking the feedback from the semantic system to the orthographic system, functionally separating the orthographic and semantic modules.

Pattern of biphasic response to various noxious stimuli in rats ingesting sucrose ad libitum

Sucrose ingestion is reported to produce an initial (20–30 min) analgesia and late (<5 h) hyperalgesia. However, the influence of the characteristics of noxious stimuli and sweet substances on the pattern of transition from analgesia to hyperalgesia is not known. Therefore, we investigated the effect of sucrose (20%, sucrose fed group), saccharin (0.1%, saccharin fed group) and water ingestion (control group) on pain responses to various noxious stimuli for 5 h. Latency of motor response of tail (TFL), paws to noxious thermal stimuli, threshold for elicitation of motor responses to electrical stimulation of tail nociceptive afferents in 5 sessions (0, 0.25, 1, 3 and 5 h) and pain-related behavior to tonic noxious stimulus in 3 sessions at 1, 3 and 5 h were recorded. In sucrose fed rats as compared to controls, the TFL sequentially increased (9.29 ± 0.47 s from 8.41 ± 0.25; p < 0.01), recovered to base-line and decreased (6.61 ± 0.61 sec; p < 0.0001) in sessions II, III and V indicating analgesia, eualgesia and hyperalgesia, respectively. In saccharin fed rats the initial analgesia extended until session III followed by eualgesia and hyperalgesia in sessions IV and V. Pain related behaviour to tonic noxious stimulus also indicated an initial analgesia (0–5 min), intermediate eualgesia and late hyperalgesia (3–5 h) in sucrose fed rats, whereas only analgesia in saccharin fed rats. The results of our study suggest that sucrose ingestion for 5 h leads to a bi-phasic response to both phasic and tonic noxious stimuli, albeit there are variations in their durations. Therefore, the temporal relationship of the nociceptive responses to palatable food is a function of the stimulus quality of both.

The Effect of Early-Life Stress on Airway Inflammation in Adult Mice

Background/Aims: Neonatal stress induces permanent physiological changes that may influence the immune system. Early-life stress increases asthma disease severity in children. We investigated the effects of early-life stress on allergic airway inflammation using a murine model of asthma coupled to maternal separation as an early-life stress stimulus. Methods: Maternally separated (MS) and unseparated control (CON) mice were sensitized with ovalbumin (OVA) beginning at day 31 after birth. Results: Challenging mice with OVA increased airway hyperresponsiveness (AHR) and the number of inflammatory cells recovered in the bronchoalveolar lavage (BAL), compared to saline-challenged mice. Challenging MS mice with OVA resulted in less total inflammatory cells, eosinophils, interferon-γ, and interleukin-4 in BAL compared to CON mice. However, MS mice challenged with OVA exhibited AHR similar to CON mice challenged with OVA. In contrast, an enhanced stress protocol (MS+) involving removal of pups from their home cages following the removal of the dam resulted in inflammatory cell accumulation and cytokine levels in the BAL similar to CON mice and higher than MS mice. Conclusions: These findings indicate that the effect of early-life psychological factors on the development of airway inflammatory diseases such as asthma is very complex and depends on the quality of the psychological stress stimulus.

Edges, colour and awareness in blindsight

It remains unclear what is being processed in blindsight in response to faces, colours, shapes, and patterns. This was investigated in two hemianopes with chromatic and achromatic stimuli with sharp or shallow luminance or chromatic contrast boundaries or temporal onsets. Performance was excellent only when stimuli had sharp spatial boundaries. When discrimination between isoluminant coloured Gaussians was good it declined to chance levels if stimulus onset was slow. The ability to discriminate between instantaneously presented colours in the hemianopic field depended on their luminance, indicating that wavelength discrimination totally independent of other stimulus qualities is absent. When presented with narrow-band colours the hemianopes detected a stimulus maximally effective for S-cones but invisible to M- and L-cones, indicating that blindsight is mediated not just by the mid-brain, which receives no S-cone input, or that the rods contribute to blindsight. The results show that only simple stimulus features are processed in blindsight.

On the joint effects of stimulus quality, regularity, and lexicality when reading aloud: New challenges.

A number of computational models have been developed over the last 2 decades that are remarkably successful at explaining the process of translating print into sound. Nevertheless, 2 of the most successful computational accounts on the table fail to simulate the results from factorial experiments reported in this article in which university students read aloud letter strings that varied in terms of spelling-sound regularity and lexicality (regular words vs. exception words vs. nonwords) and stimulus quality (bright vs. dim). Skilled readers yielded additive effects of regularity and stimulus quality and additive effects of lexicality and stimulus quality on both RT and errors when nonwords were mixed with words. When only words appeared in the list, there was an interaction in which exception words were less affected by low stimulus quality than regular words were; no existing account anticipates or explains these results. We advance a hypothesis that assumes a novel module that accommodates these data and provide an existence proof in the form of a simulation.

Novel approaches to treatment of generalized anxiety disorder

The present paper reviews recent studies on the clinical presentation of generalized anxiety disorder (GAD) and the current level of evidence for treatment with medications and psychotherapy. An apprehensive state of mind, regardless of the quality of stimuli, is at the core of GAD, causing a pervasive cognitive dysfunction that is separate from that seen in depression and obsessive compulsive disorder. When treatments reduce anxiety-related symptoms and insomnia, patients report a restoration of social functioning, probably as a consequence of improved decision-making, cooperative skills, and risk assessment. Late-onset GAD symptoms in the elderly may be caused or aggravated by cerebrovascular events, loneliness, bereavement, substance use, and the prospect of death. Insomnia in GAD may be primary or caused by common medications. Practice guidelines fail to capture the needs of the entire range of patients with GAD as they build on patients without comorbidity who have been selected for phase III trials. They are also biased to reduce cost. The past 10 years have seen a range of safe and effective treatments for GAD. Late-onset GAD presents a new challenge to researchers and practitioners. The current state of knowledge about GAD does not justify radical revisions of the diagnostic criteria in the ongoing revisions of the Diagnostic and Statistical Manual of Mental Disorders-IV and the International Statistical Classification of Diseases-10 nosologies.

Distinct effects of perceptual quality on auditory word recognition, memory formation and recall in a neural model of sequential memory

Adults with sensory impairment, such as reduced hearing acuity, have impaired ability to recall identifiable words, even when their memory is otherwise normal. We hypothesize that poorer stimulus quality causes weaker activity in neurons responsive to the stimulus and more time to elapse between stimulus onset and identification. The weaker activity and increased delay to stimulus identification reduce the necessary strengthening of connections between neurons active before stimulus presentation and neurons active at the time of stimulus identification. We test our hypothesis through a biologically motivated computational model, which performs item recognition, memory formation and memory retrieval. In our simulations, spiking neurons are distributed into pools representing either items or context, in two separate, but connected winner-takes-all (WTA) networks. We include associative, Hebbian learning, by comparing multiple forms of spike-timing-dependent plasticity (STDP), which strengthen synapses between coactive neurons during stimulus identification. Synaptic strengthening by STDP can be sufficient to reactivate neurons during recall if their activity during a prior stimulus rose strongly and rapidly. We find that a single poor quality stimulus impairs recall of neighboring stimuli as well as the weak stimulus itself. We demonstrate that within the WTA paradigm of word recognition, reactivation of separate, connected sets of non-word, context cells permits reverse recall. Also, only with such coactive context cells, does slowing the rate of stimulus presentation increase recall probability. We conclude that significant temporal overlap of neural activity patterns, absent from individual WTA networks, is necessary to match behavioral data for word recall.

Should IQ, perceptual speed, or both be used to explain response time?

Vickers and Smith (1986) described inspection time (IT) as a single measure capable of capturing individual differences in performance. Since then, IT has been shown to correlate with intelligence quotient (IQ). In turn, IQ is a stronger correlate of response time (RT) for slower trials than for faster trials, and this is observed when IQ also correlates with the quality of stimuli or with the degree of caution from participants. The present study investigated whether IT correlates with RT and with quality of evidence or degree of caution in the same way as IQ does. Results showed that IT correlations differed from IQ correlations in a manner that could indicate task specificity. It is recommended that both IQ and IT be measured in future studies so that further empirical evidence can help establish a working hypothesis for IT and IQ as predictors of performance.

Taste, Reward, and Physiology

Taste is an intermediary between the traditional externally oriented senses and visceral sensation. It possesses typical features of other senses, such as identification of stimulus quality and intensity through a spatiotemporal code. But taste may be classified as a visceral afferent system according to its embryological, anatomical, and functional characteristics. The sense of taste may be viewed as the beginning of a body-long chemosensory tube with receptors throughout that are sensitive to the molecules being liberated by the digestive process. Chemicals stimulating taste receptors, however, are only candidates for ingestion—the commitment to accept them has not yet been made. Thus, it is the obligation of the taste system to assess the desirability of consuming a prospective food relative to the momentary physiological needs of the animal it serves. Vision and olfaction give evidence, but taste is the final arbiter in determining which subset of the unruly and often hostile chemical environment will be permitted entry into the tightly monitored biochemical world within. Thus, taste may be viewed as a Janus head, placed on an ancient city gate, one face turned outward to assess the goods and perils surrounding its walls, the other facing in to determine what its inhabitants need at the moment. Taste is well suited to its task of matching availability to need through its anatomy and function, which will first be described in chemically oriented rodents, then in visually dominated primates. The two will be treated separately because they use quite different strategies to carry out similar activities. Moreover, nearly all the hindbrain data are from rodents, and most of the forebrain data are from primates.

Symposium Overview

Symposium Overview

The gustatory cortex and multisensory integration

The central gustatory pathways are part of the brain circuits upon which rest the decision to ingest or reject a food. The quality of food stimuli, however, relies not only on their taste but also on properties such as odor, texture and temperature. We will review anatomical and functional evidence showing that the central gustatory system, in particular its cortical aspect, functions as an integrative circuit in which taste-responsive neurons also show sensitivity to somatosensory and olfactory stimulation. In addition, gustatory pathways are modulated by the internal state of the body, with neuronal responses to tastes changing according to variations in physiological parameters such as gastrointestinal hormones or blood glucose levels. Therefore, rather than working as the receptive field of peripheral taste receptor cells, the central gustatory pathways seem to operate as a multisensory system dedicated to evaluating the biological significance of intra-oral stimuli.

Translating nociceptive processing into human pain models

As volunteers can easily communicate quality and intensity of painful stimuli, human pain models appear to be ideally suited to test analgesic compounds, but also to study pain mechanisms. Acute stimulation of nociceptors under physiologic conditions has proven not to be of particular use as an experimental pain model. In contrast, if the experimental models include sensitization of the peripheral or central pain processing they may indeed mimic certain aspects of chronic pain conditions. Peripheral inflammatory conditions can be induced experimentally with sensitization patterns correlating to clinical inflammatory pain. There are also well-characterized models of central sensitization, which mimic aspects of neuropathic pain patients such as touch evoked allodynia and punctate hyperalgesia. The main complaint of chronic pain patients, however, is spontaneous pain, but currently there is no human model available that would mimic chronic inflammatory or neuropathic pain. Thus, although being helpful for proof of concept studies and dose finding, current human pain models cannot replace patient studies for testing efficacy of analgesic compounds.

Histamine H1 receptor blockade predominantly impairs sensory processes in human sensorimotor performance.

Centrally active antihistamines impair cognitive performance, particularly sensorimotor performance. The aim of the present study was to further elucidate the scarcely studied subprocesses involved in sensorimotor performance, which may be affected by H1 receptor blockade. Better knowledge about the cognitive deficits associated with histamine dysfunction can contribute to better treatment of clinical disorders in which histamine hypofunction may be a contributing factor, such as in schizophrenia. Interactions of dexchlorpheniramine with specific task manipulations in a choice reaction time task were studied. Task demands were increased at the level of sensory subprocesses by decreasing stimulus quality, and at the level of motor subprocesses by increasing response complexity. A total of 18 healthy volunteers (9 female) aged between 18 and 45 years participated in a three-way, double-blind, crossover design. Treatments were single oral doses of 4 mg dexchlorpheniramine, 1 mg lorazepam and placebo. Behavioural effects were assessed by measuring reaction times and effects on brain activity by event-related potentials. Dexchlorpheniramine significantly slowed reaction times, but did not significantly interact with task manipulations. However, it did significantly interact with stimulus quality, as measured by event-related potentials. Lorazepam slowed reaction times and interacted with perceptual manipulations, as shown by effects on reaction times. The results confirm that the histamine system is involved in sensory information processing and show that H1 blockade does not affect motoric information processing. Histamine hypofunction in clinical disorders may cause impaired sensory processing, which may be a drug target.

Enhanced post-learning memory consolidation is influenced by arousal predisposition and emotion regulation but not by stimulus valence or arousal

Emotionally arousing stimuli are more memorable than neutral ones and arousal induced after learning enhances later retrieval. However, there is as yet little study of how stimulus qualities might interact with induced arousal and how individual differences might influence the modulation of memory. Thus, the present study examined the effect of arousal induced after learning on memory for words that varied in both arousal and valence quality, as well as the influence of three individual differences factors that are known to influence arousal response: emotional suppression, emotional reappraisal, and arousal predisposition. Seventy-six adults (57 female) viewed and rated 60 words that normatively ranged from high to low in arousal and valence. Ten minutes later, they viewed a 3-min comedic or neutral video clip. Arousal induced after learning enhanced 1-week delayed memory, spanning the lengthy task without preference for word type or serial position, contrasting with reports of arousal effects interacting with stimulus qualities. Importantly, being predisposed to arousal led to greater enhancement of long-term memory modulation, while the use of emotional reappraisal, which reduces arousal responding, inhibited the ability of arousal to induce memory enhancement. Thus, individual differences that influence arousal responding can contribute to or interfere with memory modulation.

Reading aloud: Evidence for contextual control over lexical activation.

Can readers exert control (albeit unconsciously) over activation at particular loci in the reading system? The authors addressed this issue in 4 experiments in which participants read target words aloud and the factors of prime-target relation (semantic, repetition), context (related, unrelated), stimulus quality (bright, dim), and relatedness proportion (RP; high, low) were manipulated. In the high RP condition (RP = .5), an interaction between semantic context and stimulus quality was observed in which low stimulus quality slowed unrelated targets more than related ones, replicating previous work. In contrast, the low RP condition (RP = .25) yielded additive effects of semantic context and stimulus quality. However, when low RP was examined within the context of repetition priming, context and stimulus quality once again interacted. These results are discussed in the context of a widely endorsed framework with the addition of the central assumption that there is control over feedback between various levels.

Relating the Neural Representation and Perceptual Quality of Olfactory Stimuli

Event Abstract Back to Event Relating the Neural Representation and Perceptual Quality of Olfactory Stimuli John P. McGann1* 1 Rutgers University, Department of Psychology, United States The mouse olfactory bulb provides a powerful system for exploring the olfactory system because it permit the direct observation of physiological responses to odorants on both the population and single-cell levels while relating those responses to the corresponding perception of the odorant using behavioral olfactory psychophysical experimentation. Fig. 1A shows a fluorescence image of the right olfactory bulb of an anesthetized mouse expressing the exocytosis indicator synaptopHluorin [1] in the axon terminals of its olfactory receptor neurons (ORNs). The image shows the dorsal surface of the bulb visualized in vivo through a cranial window. Note that individual olfactory bulb glomeruli are visible in both the lower (left) and higher (right) magnification views. Fig. 1B (left) illustrates how the presentation of the odorant methyl valerate induces an increase in fluorescence (indicating transmitter release from ORN terminals) in a subset of the glomeruli shown in 1A (right). This pattern of response is odorant-specific, thus serving as the primary sensory representation of the odorant. In this session I will show how changes in this sensory representation may be induced experimentally, though pharmacological manipulation or sensory experience, and how these changes can be linked to olfactory perception. Fig. 1B illustrates how the application of the GABAB receptor antagonist CGP35348 (which blocks the GABA-mediated presynaptic inhibition of neurotransmitter release from ORN terminals) alters the representation of methyl valerate by increasing the magnitude of odor-evoked synaptic input without changing the relative responses across glomeruli [2]. In separate behavioral experiments, mice received bilateral infusions of CGP while performing behavioral tasks designed to quantify their perception of odor intensity and to evaluate their ability to discriminate between chemically similar odorants. The results demonstrate that CGP infusion produces changes in olfactory perceptions that are predictable from its effects on the neurophysiology of odorant responses. These experiments show how this combination of experimental techniques can successfully link the neural representation of odorants with the behaviorally-observed perception of odor intensity and quality. fig1

Additive and interactive effects of stimulus degradation: No challenge for CDP+.

S. O'Malley and D. Besner (2008) showed that additive effects of stimulus degradation and word frequency in reading aloud occur in the presence of nonwords but not in pure word lists. They argued that this dissociation presents a major challenge to interactive computational models of reading aloud and claimed that no currently implemented model is able to simulate additive effects in these conditions. In the current article, it is shown that the connectionist dual process model (CDP+) can simulate these effects because its nonlexical route is thresholded. The authors present a series of simulations showing that CDP+ can not only simulate the precise dissociation observed by O'Malley and Besner but more generally can produce additive effects for a wide range of parameter combinations and different sets of items. The nonlexical route of CDP+ was not modified post hoc to deal with the effects of stimulus quality, but it had been thresholded for principled reasons before it was known that these effects existed. Together, the effects of stimulus quality on word frequency do not challenge CDP+ but rather provide unexpected support for its architecture and processing dynamics.

Additivity of factor effects in reading tasks is still a challenge for computational models: Reply to Ziegler, Perry, and Zorzi (2009).

J. C. Ziegler, C. Perry, and M. Zorzi (2009) have claimed that their connectionist dual process model (CDP+) can simulate the data reported by S. O'Malley and D. Besner. Most centrally, they have claimed that the model simulates additive effects of stimulus quality and word frequency on the time to read aloud when words and nonwords are randomly intermixed. This work represents an important attempt given that computational models of reading processes have to date largely ignored the issue of whether it is possible to simulate additive effects. Despite CDP+'s success at capturing many other phenomena, it is clear that CDP+ fails to capture the full pattern seen with skilled readers in these experiments.

Cortical activation in response to pure taste stimuli during the physiological states of hunger and satiety

This event-related functional magnetic resonance imaging (er-fMRI) study investigated BOLD signal change in response to a series of pure gustatory stimuli that varied in stimulus quality when subjects were hungry and sated with a nutritional pre-load. Group analyses showed significant differences in activation in the hunger minus satiety condition in response to sucrose, caffeine, saccharin, and citric acid within the thalamus, hippocampus, and parahippocampus. When examining the hunger and satiety conditions, activation varied as a function of stimulus, with the majority of the stimuli exhibiting significantly greater activation in the hunger state within the insula, thalamus, and substantia nigra, in contrast to decreased activation in the satiated state within the parahippocampus, hippocampus, amygdala, and anterior cingulate. Region of interest (ROI) analysis revealed two significant interactions, ROI by physiology and ROI by physiology by stimulus. In the satiety condition, the primary (inferior and superior insulae) and secondary (OFC 11 and OFC 47) taste regions exhibited significantly greater brain activation in response to all stimuli than regions involved in processing eating behavior (hypothalamus), affect (amygdala), and memory (hippocampus, parahippocampus and entorhinal cortex). These same regions demonstrated significantly greater activation within the hunger condition than the satiety condition, with the exception of the superior insula. Furthermore, the patterns of activation differed as a function taste stimulus, with greater activation in response to sucrose than to the other stimuli. These differential patterns of activation suggest that the physiological states of hunger and satiety produce divergent activation in multiple brain areas in response to different pure gustatory stimuli.