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PubMed1982

Duration of increment, magnitude estimation adaptation and a proposed loudness function.

In a previous experiment on the effects of loudness adaptation on magnitude estimation (M.E.), monaural loudness adaptation was demonstrated above 30 db SL (Weiler et al, Brit. J. Audiol., 1981, 15, 210-204). Adaptation was measured by a modified method of M.E. above the loudness limit proposed by Fishkin et al (J. Ac. Soc. Am., 1977, S61). The adapting signal, a continuous pure tone, did not produce statistically significant differences in loudness M.E. for the majority of listeners. The study of Weiler et al had results similar to those of Fishkin et el, but raised questions about the comparison signal increment, since when a 20-db comparison signal was superimposed, for 5 sec out of every 30, to an ongoing signal of 60 db SPL, the subsequent judgments demonstrated an immediate and cumulative adaptation effect. The present study investigated duration effects of the comparison signal on loudness adaptation through M.E. procedures. Normal-hearing Ss (N: 10, mdn age: 24 yrs) served. The first of 3 conditions (5-sec duration of a 20-db comparison signal) showed a sizable change in M.E. for loudness, and was significantly different from conditions using 1- or 0.5-sec durations, demonstrating that a reduction in the duration of the comparison signal significantly lessened the loudness adaptation effect of the adapting signal. A discussion of the results in comparison to other studies was provided.

Adult↗

PubMedDate not supplied

Adaptive computing for people with disabilities.

Adaptive computing is a relatively new area, and little has been written in the nursing literature on the topic. "Adaptive computing" refers to the professional services and the technology (both hardware and software) that make computing technology accessible for persons with disabilities. Nurses in many settings such as schools, industry, rehabilitation facilities, and the community, can use knowledge of adaptive computing as they counsel, advise, and advocate for people with disabilities. Nurses with an awareness and knowledge of adaptive computing will be better able to promote high-level wellness for individuals with disabilities, thus maximizing their potential for an active fulfilling life. People with different types of disabilities, including visual, mobility, hearing, learning, communication disorders and acquired brain injuries may benefit from computer adaptations. Disabled people encounter barriers to computing in six major areas: 1) the environment, 2) data entry, 3) information output, 4) technical documentation, 5) support, and 6) training. After a discussion of these barriers, the criteria for selecting appropriate adaptations and selected examples of adaptations are presented. Several cases studies illustrate the evaluation process and the development of adaptive computer solutions.

Computers↗

PubMed1997

Adaptive sampling in behavioral surveys.

Studies of populations such as drug users encounter difficulties because the members of the populations are rare, hidden, or hard to reach. Conventionally designed large-scale surveys detect relatively few members of the populations so that estimates of population characteristics have high uncertainty. Ethnographic studies, on the other hand, reach suitable numbers of individuals only through the use of link-tracing, chain referral, or snowball sampling procedures that often leave the investigators unable to make inferences from their sample to the hidden population as a whole. In adaptive sampling, the procedure for selecting people or other units to be in the sample depends on variables of interest observed during the survey, so the design adapts to the population as encountered. For example, when self-reported drug use is found among members of the sample, sampling effort may be increased in nearby areas. Types of adaptive sampling designs include ordinary sequential sampling, adaptive allocation in stratified sampling, adaptive cluster sampling, and optimal model-based designs. Graph sampling refers to situations with nodes (for example, people) connected by edges (such as social links or geographic proximity). An initial sample of nodes or edges is selected and edges are subsequently followed to bring other nodes into the sample. Graph sampling designs include network sampling, snowball sampling, link-tracing, chain referral, and adaptive cluster sampling. A graph sampling design is adaptive if the decision to include linked nodes depends on variables of interest observed on nodes already in the sample. Adjustment methods for nonsampling errors such as imperfect detection of drug users in the sample apply to adaptive as well as conventional designs.

Behavior↗

PubMed1990

Rod and cone contribution to adaptation processes in cat retinal ganglion cells.

Extracellular ganglion cell responses were recorded to investigate mechanisms of light adaptation. Monochromatic test spots (575 nm) were projected onto the receptive field center of off-center cells and superimposed on a steady blue-green Ganzfeld background (Schott Filter BG 28), the strength of which was increased in steps of 0.5 log units to adapt rods. Response vs. log intensity functions were determined over a range of 7 log units of test light irradiance at each background level. At higher adaptation levels response thresholds followed the typical Weber function. Surprisingly at lower adaptation levels the sensitivity of the cell increased by about 0.7 log units, most markedly in a range of 1 log unit of moderate light adaptation when the background was changed from dark to the dimmest detectable background (10(-5) lm/m2). In the dark-adapted state a small off-response of long latency (40-100 ms at 10(2) quanta.s-1.microns-2) is observed at low rod stimulating test light irradiances. A transition to a cone-dominated transient response of 2 to 5 ms duration occurred at high intensities (10(5) quanta.s-1.microns-2). At mesopic levels the two responses seem to cancel each other, rendering a delayed off-response that is probably the result of rod-cone interaction. As in psychophysics, saturation can be observed at very high background intensities (10(6) quanta.s-1 microns-2). These data suggest interactions between rods and cones that determine the sensitivity of cat retinal ganglion cells at low levels of adaptation for suprathreshold stimuli.

Action Potentials↗

PubMed1978

[Influence of adaption level upon oscillatory potential in the electroretinogram (author's transl)].

Oscillatory potentials (OP's) were recorded using constant energy stimulating from 2.5 J at different levels of adaptation from 400 to 30 fl, as well as pre-dark adaptation. O1, O2, and O3 regularly appear in the ascending branch of the b-wave complex, and after pre-dark adaptation the less differentiated O4 and O5 appear as well, exhibiting variable potental heights and durations as the dark time progresses. With intensive pre-light adaptation there is a relative reduction of potential, as is also true following weak prelight adaptation or dark adaptation; the culmination time in the former case being more rapid, and in the latter case slower. Good discrimination of the OP with a concurrent diminution in the amplitudes was only observed after a pre-dark adaptation.

Adaptation, Physiological↗

PubMed1998

Adaptation-dependent plasticity of rod bipolar cell axon terminal morphology in the rat retina.

We chose synaptic terminals of rat rod bipolar cells as a model system to study activity-related changes in the overall morphology and the fine structure of synaptic sites. Using confocal laser scanning microscopy in conjunction with three-dimensional reconstruction and electron microscopy, we examined the effect of light and dark adaptation on axon terminals identified by protein kinase C (PKC) immunoreactivity. Rod bipolar cell axon terminals consisted of 2-3 polymorphic boutons situated close to the ganglion cell layer and a single ovoid swelling located more distally. Both components of the terminal complex showed adaptation-dependent differences in the distribution of PKC immunoreactivity and in their morphology. In light-adapted rod bipolar cell axon terminals, PKC immunoreactivity was homogeneously distributed throughout the cytoplasm, whereas terminals from dark-adapted animals showed PKC immunoreactivity preferentially localised in the submembrane compartment and a reduced staining of the more central cytoplasm. In three-dimensional reconstructions of optical sections and at the ultrastructural level, the shape of light-adapted axon terminals was round and smooth and exhibited more convexly curved synaptic membranes. In contrast, dark-adapted terminals had irregular contours, numerous dimples and a concave synaptic curvature. No spinules of bipolar cell terminals were observed in dark-adapted material. These observations are discussed in the context of activity-related morphological plasticity of central nervous system synapses and of the functions of PKC in the cycle of vesicle fusion and retrieval at the tonically active ribbon synapses of the rod bipolar axon terminal.

Adaptation, Ocular↗

PubMed1996

Left and right visual field advantages are a function of scotopic and photopic retinal adaptation, respectively, in simple reaction time to near-threshold targets.

Modulation of stimulus luminance in a tachistoscopic face discrimination task has been found to significantly invert visual hemifield advantage in reaction time (RT) (Sergent, 1982a, Sergent, 1982b). However, there is no more physiological rationale for that than for a similar effect, say, of retinal adaptation, and it is even conceivable that the latter may have confounded the former in past experiments. The experiments reported here were therefore designed to tease out the relative contributions of stimulus luminance and of background illumination (i.e., retinal adaptation) in a simple RT task. Two equally difficult conditions of dim targets were set up, one with light-adapted subjects and one with dark-adapted subjects. Similarly, two equally difficult conditions of bright targets were set up with light and dark-adapted subjects. It was found that dim targets (near detection threshold) yielded a significant right visual field RT advantage in light-adapted subjects and that dim targets (equally near detection threshold) yielded a significant left visual field RT advantage in dark-adapted subjects. Future experiments will determine whether cone-mediated RT to detection is left hemisphere dominant and whether rod-mediated RT to detection is right hemisphere dominant.

Adaptation, Ocular↗

PubMed1987

D1 dopamine receptors in the rat retina: effect of dark adaptation and chronic blockade by SCH 23390.

Chronic administration of SCH 23390 (0.03 mg/kg s.c., three times daily), a selective D1 dopamine (DA) receptor blocker, markedly increased the [3H]SCH 23390 binding in the rat retina. As revealed by the Scatchard plot analysis of saturation data from retinal homogenates, chronic SCH 23390 increased the total number of binding sites by 34% when compared to tissue from solvent-treated rats but failed to change the apparent affinity of [3H]SCH 23390 for its binding sites. The up-regulation of [3H]SCH 23390 binding sites was paralleled by an increase in the sensitivity of retina DA-sensitive adenylate cyclase. In fact, DA (5 X 10(-6) M to 10(-4) M) produced a higher accumulation of cyclic AMP (from 58 to 128%) in the retina of SCH 23390-treated rats as compared to the accumulation (from 35 to 80%) found in tissue from solvent-treated rats. Since dark adaptation decreases dopaminergic function in the rat retina, the influence of environmental lighting on [3H]SCH 23390 binding and DA-sensitive adenylate cyclase activity was studied. After 4 h of dark adaptation the density of [3H]SCH 23390 binding sites was higher (32%) than that from light-adapted rats. On the other hand, dark adaptation failed to change the apparent affinity of [3H]SCH 23390 for its binding sites. Moreover, DA elicited a greater stimulation of adenylate cyclase activity in homogenates of retina from dark-adapted rats. Thus, the maximum adenylate cyclase response to DA resulted higher in the retina of dark-adapted rats (152%) than that found in the retina of light-adapted animals (97%).(ABSTRACT TRUNCATED AT 250 WORDS)

Adaptation, Physiological↗

PubMed1993

Light adaptation of human rod receptors: the leading edge of the human a-wave and models of rod receptor activity.

The human rod receptors can be studied by measuring the leading edge of the rod a-wave of the ERG. Computational models, previously shown to fit the recordings from single rods, are fitted to dark-adapted a-wave responses. A model proposed by Lamb and Pugh [(1992) Journal of Physiology, 499, 719-758] fits slightly better than the traditional models based upon n-stage exponential filters. To test alternative models of rod light adaptation, a-waves were recorded to flashes presented upon steady adapting lights. Steady adapting lights decrease the rods' sensitivity. Human rods must adapt as response compression alone predicts far greater decreases in sensitivity. The evidence suggests that the mechanism(s) of adaptation include a change in the time-course of the rod's response. Human rods appear to adapt in much the same manner as do the rods of other vertebrates.

Adaptation, Ocular↗

PubMed1995

Adaptation mechanisms in spatial vision--I. Bleaches and backgrounds.

To examine how the mechanisms of bleaching and background adaptation affect spatial pattern vision, contrast detection thresholds were measured in the fovea for sinusoidal (increment-Gabor) targets, during long-term dark adaptation following full bleaches, and against steady adapting backgrounds of various intensities. The dark-adaptation curves were found to be invariant in shape over the range of spatial frequencies tested (1-15 c/deg); in other words, the amplitude sensitivity functions were invariant during dark adaptation. These results support the hypothesis that bleaching adaptation is local and multiplicative. On the other hand, the background-adaptation curves measured for different spatial frequencies were found to converge as background intensity increased; the amplitude sensitivity functions became flatter. These results reject the equivalent-background hypothesis.

Adaptation, Ocular↗

PubMed2004

A long-lasting improvement of somatosensory function after prism adaptation, a case study.

Previous studies have observed a reduction of visual and representational neglect symptoms after visuo-manual adaptation to rightward displacing prisms. Recently, improvements have also been observed on somatosensory tasks, such as locating the centre of a haptically explored circle and tactile double simultaneous stimulation. In the current single case study we assessed whether prism adaptation with the ipsilesional hand improved two aspects of contralesional somatosensory function, pressure sensitivity and proprioception. After the first application of prism adaptation improvements in pressure sensitivity and proprioception were observed. A second prism adaptation confirmed the improvements in contralesional somatosensory function. The effects of prism adaptation on position sense were longer lasting than have been reported previously, but consistent with reductions of visual neglect symptoms after prism adaptation. The current findings suggest that prism adaptation can have a non-spatial effect on neglect-related supra-modal deficits.

Adaptation, Physiological↗

PubMedDate not supplied

Horizontal cell sensitivity in the cat retina during prolonged dark adaptation.

The effects of dark adaptation on the response properties of ganglion cells have been documented extensively in the cat retina. To pinpoint the different retinal mechanisms that underlie these effects, we studied the response characteristics of cat horizontal (H) cells during prolonged dark adaptation. H-cell responses were recorded intracellularly in the optically intact, in vivo eye. To disentangle rod and cone contributions, sensitivity changes during dark adaptation were tracked with white light and with monochromatic lights that favored either rod or cone excitation. Stable, long-lasting recordings allowed us to measure changes of sensitivity for adaptation periods up to 45 min. Thresholds for white light and 503-nm monochromatic light decreased steadily and in parallel. The maximum increase of sensitivity, after extinguishing a photopic adaptation light, was 1.8 log units only, reached after about 35 min. Sensitivity for 581-nm lights also increased steadily, but at a shallower slope. The steady increase of sensitivity was concomitant with a linear shift in resting membrane potential and with an increase in relative rod contribution to the threshold responses. Even though small-amplitude responses were rod dominated after prolonged dark adaptation, sensitivity to rod signals remained relatively low, compared to sensitivity of cone responses or to the absolute sensitivity of ganglion cells. This suggests that the cone-H-cell pathway plays no role in the dark-adapted cat retina.

Adaptation, Ocular↗

PubMedDate not supplied

Comparison of the responses of AII amacrine cells in the dark- and light-adapted rabbit retina.

We studied the light-evoked responses of AII amacrine cells in the rabbit retina under dark- and light-adapted conditions. In contrast to the results of previous studies, we found that AII cells display robust responses to light over a 6-7 log unit intensity range, well beyond the operating range of rod photoreceptors. Under dark adaptation, AII cells showed an ON-center/OFF-surround receptive-field organization. The intensity-response profile of the center-mediated response component followed a dual-limbed sigmoidal function indicating a transition from rod to cone mediation as stimulus intensities were increased. Following light adaptation, the receptive-field organization of AII cells changed dramatically. Light-adapted AII cells showed both ON- and OFF-responses to stimulation of the center receptive field, but we found no evidence for an antagonistic surround. Interestingly, the OFF-center response appeared first following rapid light adaptation and was then replaced gradually over a 1-4 min period by the emerging ON-center response component. Application of the metabotropic glutamate receptor agonist APB, the ionotropic glutamate blocker CNQX, 8-bromo-cGMP, and the nitric oxide donor SNAP all showed differential effects on the various center-mediated responses displayed by dark- and light-adapted AII cells. Taken together, these pharmacological results indicated that different synaptic circuits are responsible for the generation of the different AII cell responses. Specifically, the rod-driven ON-center responses are apparently derived from rod bipolar cell synaptic inputs, whereas the cone-driven ON-center responses arise from signals crossing the gap junctions between AII cells and ON-center cone bipolar cells. Additionally, the OFF-center response of light-adapted AII cells reflects direct synaptic inputs from OFF-center cone bipolar cells to AII dendritic processes in the distal inner plexiform layer.

6-Cyano-7-nitroquinoxaline-2,3-dione↗

PubMed1970

Visual adaptation in the retina of the skate.

The electroretinogram (ERG) and single-unit ganglion cell activity were recorded from the eyecup of the skate (Raja erinacea and R. oscellata), and the adaptation properties of both types of response compared with in situ rhodopsin measurements obtained by fundus reflectometry. Under all conditions tested, the b-wave of the ERG and the ganglion cell discharge showed identical adaptation properties. For example, after flash adaptation that bleached 80% of the rhodopsin, neither ganglion cell nor b-wave activity could be elicited for 10-15 min. Following this unresponsive period, thresholds fell rapidly; by 20 min after the flash, sensitivity was within 3 log units of the dark-adapted level. Further recovery of threshold was slow, requiring an additional 70-90 min to reach absolute threshold. Measurements of rhodopsin levels showed a close correlation with the slow recovery of threshold that occurred between 20 and 120 min of dark adaptation; there is a linear relation between rhodopsin concentration and log threshold. Other experiments dealt with the initial unresponsive period induced by light adaptation. The duration of this unresponsive period depended on the brightness of the adapting field; with bright backgrounds, suppression of retinal activity lasted 20-25 min, but sensitivity subsequently returned and thresholds fell to a steady-state value. At all background levels tested, increment thresholds were linearly related to background luminance.

Adaptation, Ocular↗

PubMed2025

Integrative Genomic, Transcriptomic and Epigenomic Analysis Reveals cis-regulatory Contributions to High-altitude Adaptation in Tibetan Pigs.

The Qinghai-Tibet Plateau, characterized by its extreme environmental conditions, presents significant challenges to life, making it an ideal region for studying adaptation and evolution. Tibetan pigs, known for their high genetic diversity and exceptional adaptability to high altitudes, serve as excellent models for investigating high-altitude adaptation. While previous studies have extensively identified genetic determinants associated with high-altitude adaptation, the molecular mechanisms, particularly cis-regulatory patterns, remain poorly understood. Here, we conducted a selective sweep analysis using 484 genomes from Chinese and Western pig breeds across various altitudes, revealing 38.56 Mb of genomic regions under selection in Tibetan pigs. Enrichment analysis identified the lung as the primary functional tissue involved in high-altitude adaptation, supported by tissue-specific transcriptional and regulatory patterns observed between Tibetan and Meishan pigs (low altitude). By integrating genomic, RNA-seq, ATAC-seq, and H3K27ac HiChIP data, we constructed comprehensive enhancer-promoter regulatory maps of candidate genes and pinpointed promising genetic determinants associated with high-altitude adaptation, including SNPs in EPAS1, KLF13, SPRED1, and CFD. These loci were predicted to influence chromatin accessibility and the interactions of regulatory elements, with altered binding strength of relevant transcription factors. Further in vitro experiments confirmed that these loci function as allele-specific enhancers, modulating the expression of target genes. Our findings elucidate the regulatory basis of high-altitude adaptation in Tibetan pigs and provide valuable insights for exploring hypoxia-related diseases in livestock and humans.

Animals↗

PubMed2004

Evaluating evidence of psychological adaptation: how do we know one when we see one?

Evolutionary psychologists argue that human nature contains many discrete psychological adaptations. Each adaptation is theorized to have been functional in humans' ancestral past, and empirical evidence that an attribute is an adaptation can come from showing it possesses complexity, efficiency, universality, and other features of special design. In this article, we present a tutorial review of the evidentiary forms that evolutionary psychologists commonly use to document the existence of human adaptations. We also present a heuristic framework for integrating and evaluating cross-disciplinary evidence of adaptation. Pregnancy sickness, incest avoidance, men's desires for multiple sex partners, and an easily learned fear of snakes are evaluated as possible human adaptations using this framework. We conclude that future research and teaching in evolutionary psychology would benefit from more fully utilizing cross-disciplinary frameworks to evaluate evidence of human adaptation.

Adaptation, Biological↗

PubMed1996

Spectral plasticity of H1 horizontal cells in carp retina: independent modulation by dopamine and light-adaptation.

It was shown previously that the spectral sensitivity of luminosity/H1-type horizontal cells (HCs) in carp retinae reflects the absorption spectrum of red-sensitive cones for long wavelengths but can appear highly variable and "truncated' in the short-wavelength region of the spectrum. We have found that light-adaptation sharpened the red-sensitive spectral peak and decreased the blue/red response amplitude ratio (B/R ratio), mainly by decreasing the response to short-wavelength stimuli. The adaptation effect was more pronounced for red background light than for blue. During dark adaptation, the B/R ratio increased steadily. Exogenous dopamine (DA; 5 microM) changed the spectral response profile in a similar way to light-adaptation. However, the effect of light-adaptation in reducing the B/R ratio was still seen in retinae bathed in 5 microM DA. This effect of background adaptation was also recorded in retinae bathed in 37 microM haloperidol, as well as in retinae pretreated with 6-hydroxydopamine (i.e. DA-depleted). The results suggest that (i) short-wavelength-sensitive cones play a dynamic role in determining the spectral response profile of H1 HCs and (ii) spectral response characteristics are modulated independently by exogenous DA and an unknown endogenous neuromodulator which is activated by light-adaptation.

Adaptation, Ocular↗

PubMed2025

Genome sequencing and population genetics provide insights into local adaptation of Opisthopappus species on cliff environments of Taihang Mountains.

Local adaptation represents a pivotal theme in evolutionary biology. The Opisthopappus genus, comprising Opisthopappus longilobus and O. taihangensis, thrives on the cliffs of the Taihang Mountains. During their evolutionary history, two species are hypothesized to have locally adapted to their cliff habitats. In the present study, we employed a combined approach of whole-genome sequencing of O. taihangensis and population genomic analysis from both species to gain deeper insights into their patterns of local adaptation. Our results revealed that the expansive genome of O. taihangensis (3010.18 Mb), a consequence of a whole-genome duplication (WGD) event, coupled with a high proportion of repetitive sequences (82.70%), was postulated as one of its adaptive strategies. A clear differentiation between O. taihangensis and O. longilobus was observed, with the two species diverging approximately 17.57 million years ago (Mya), with O. longilobus serving as the ancestor. Since their divergence, limited gene flow was observed between the two species. Post-divergence, the effective population sizes of both species expanded, yet underwent a dramatic reduction at approximately 0.07 Mya. Furthermore, a total of 798 adaptive genes were identified, of which 207 overlapped with expanded genes, and eight genes were found to be under positive selection. These genes primarily regulated the growth and development of both species via pathways such as oxidation-reduction and ubiquitin-proteasome, enabling them to withstand climate changes. These findings provide profound insights into the local adaptation of Opisthopappus species to the cliff environments and offer valuable clues for further exploring the local adaptation among various cliff-dwelling organisms.

Adaptation, Physiological↗