The influence of adaptation and inhibition on the effects of onset asynchrony on auditory grouping

Onset asynchrony is an important cue for auditory scene analysis. For example, a harmonic of a vowel that begins before the other components contributes less to the perceived phonetic quality. This effect was thought primarily to involve high-level grouping processes, because the contribution can be partly restored by accompanying the leading portion of the harmonic (precursor) with a synchronous captor tone an octave higher, and hence too remote to influence adaptation of the auditory-nerve response to that harmonic. However, recent work suggests that this restoration effect arises instead from inhibitory interactions relatively early in central auditory processing. The experiments reported here have reevaluated the role of adaptation in grouping by onset asynchrony and explored further the inhibitory account of the restoration effect. Varying the frequency of the precursor in the range ± 10% relative to the vowel harmonic (Experiment 1), or introducing a silent interval from 0 to 320 ms between the precursor and the vowel (Experiment 2), both produce effects on vowel quality consistent with those predicted from peripheral adaptation or recovery from it. However, there were some listeners for whom even the smallest gap largely eliminated the effect of the precursor. Consistent with the inhibitory account of the restoration effect, a contralateral pure tone whose frequency is close to that of the precursor is highly effective at restoring the contribution of the asynchronous harmonic (Experiment 3). When the frequencies match, lateralization cues arising from binaural fusion of the precursor and contralateral tone may also contribute to this restoration. (PsycINFO Database Record (c) 2012 APA, all rights reserved)

Patients with early age-related macular degeneration exhibit signs of macro- and micro-vascular disease and abnormal blood glutathione levels

Background: This pilot study aimed to investigate systemic and retinal vascular function and their relationship to circulatory markers of cardiovascular risk in early age-related macular degeneration (AMD) patients without any already diagnosed systemic vascular pathologies. Methods: Fourteen patients diagnosed with early AMD and 14 age- and gender-matched healthy controls underwent blood pressure, carotid intima-media thickness (C-IMT) and peripheral arterial stiffness measurements. Retinal vascular reactivity was assessed by means of dynamic retinal vessel analysis (DVA) using a modified protocol. Blood analyses were conducted for glutathione levels and plasma levels of total cholesterol (CHOL), high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C) and triglycerides (TG). Results: The AMD patients showed significantly greater C-IMT (p = 0.029) and augmentation index (AIx) (p = 0.042) than the age-matched controls. In addition, they demonstrated a shallower retinal arterial dilation slope (Slope AD) (p = 0.005) and a longer retinal venous reaction time (RT) to flickering light (p = 0.026). Blood analyses also revealed that AMD patients exhibited higher oxidized glutathione (GSSG) (p = 0.024), lower redox index (p = 0.043) and higher LDL-C (p = 0.033) levels than the controls. Venous RT parameter correlated positively with blood GSSG levels (r = 0.58, p = 0.038) in AMD subjects, but not in the controls (p > 0.05). Conclusions: Patients diagnosed with early AMD exhibit signs of systemic and retinal vascular alterations that correlated with known risk markers for future cardiovascular morbidity. © 2013 Springer-Verlag Berlin Heidelberg.

Ocular signs of systemic hypertension:a review

Cardiovascular disease and stroke continue to be the chief causes of death in developed countries and one of the leading causes of visual impairment. The individual with systemic hypertension may remain asymptomatic for many years. Systemic mortality and morbidity are markedly higher for hypertensives than normotensives, but can be significantly reduced by early diagnosis and then efficient management. However, the ability of Optometrists to detect and appropriately refer systemic hypertensives remains generally poor. This review examines the disease, its effects and detection by observation of the retinal signs, particularly those considered to be pre-malignant. Previous methods of classifying retinal hypertensive signs are discussed along with more recent image analysis techniques. The role of the optometrist in detecting, monitoring and appropriate referral of systemic hypertensives is discussed in relation to current research. (C) 2001 The College of Optometrists. Published by Elsevier Science Ltd. All rights reserved.

Overweight status is associated with extensive signs of microvascular dysfunction and cardiovascular risk

The aim of this present study was to investigate if overweight individuals exhibit signs of vascular dysfunction associated with a high risk for cardiovascular disease (CVD). One hundred lean and 100 overweight participants were recruited for the present study. Retinal microvascular function was assessed using the Dynamic Retinal Vessel Analyser (DVA), and systemic macrovascular function by means of flow-mediated dilation (FMD). Investigations also included body composition, carotid intimal-media thickness (c-IMT), ambulatory blood pressure monitoring (BP), fasting plasma glucose, triglycerides (TG), cholesterol levels (HDL-C and LDL-C), and plasma von Willebrand factor (vWF). Overweight individuals presented with higher right and left c-IMT (p = 0.005 and p = 0.002, respectively), average 24-h BP values (all p <0.001), plasma glucose (p = 0.008), TG (p = 0.003), TG: HDL-C ratio (p = 0.010), and vWF levels (p = 0.004). Moreover, overweight individuals showed lower retinal arterial microvascular dilation (p = 0.039) and baseline-corrected flicker (bFR) responses (p = 0.022), as well as, prolonged dilation reaction time (RT, p = 0.047). These observations emphasise the importance of vascular screening and consideration of preventive interventions to decrease vascular risk in all individuals with adiposity above normal range.

Blur adaptation explained by a norm-based model of contrast adaptation

Adapting to blurred images makes in-focus images look too sharp, and vice-versa (Webster et al, 2002 Nature Neuroscience 5 839 - 840). We asked how such blur adaptation is related to contrast adaptation. Georgeson (1985 Spatial Vision 1 103 - 112) found that grating contrast adaptation followed a subtractive rule: perceived (matched) contrast of a grating was fairly well predicted by subtracting some fraction k(~0.3) of the adapting contrast from the test contrast. Here we apply that rule to the responses of a set of spatial filters at different scales and orientations. Blur is encoded by the pattern of filter response magnitudes over scale. We tested two versions - the 'norm model' and 'fatigue model' - against blur-matching data obtained after adaptation to sharpened, in-focus or blurred images. In the fatigue model, filter responses are simply reduced by exposure to the adapter. In the norm model, (a) the visual system is pre-adapted to a focused world and (b) discrepancy between observed and expected responses to the experimental adapter leads to additional reduction (or enhancement) of filter responses during experimental adaptation. The two models are closely related, but only the norm model gave a satisfactory account of results across the four experiments analysed, with one free parameter k. This model implies that the visual system is pre-adapted to focused images, that adapting to in-focus or blank images produces no change in adaptation, and that adapting to sharpened or blurred images changes the state of adaptation, leading to changes in perceived blur or sharpness.

A comparative and longitudinal analysis of the evolving relationship between the environment and the strategy, structure and performance of selected organisations in the British carpet industry 1959-1986:a firms in sector perspective of organisational adaptation

Orthodox contingency theory links effective organisational performance to compatible relationships between the environment and organisation strategy and structure and assumes that organisations have the capacity to adapt as the environment changes. Recent contributions to the literature on organisation theory claim that the key to effective performance is effective adaptation which in turn requires the simultaneous reconciliation of efficiency and innovation which is afforded by an unique environment-organisation configuration. The literature on organisation theory recognises the continuing confusion caused by the fragmented and often conflicting results from cross-sectional studies. Although the case is made for longitudinal studies which comprehensively describe the evolving relationship between the environment and the organisation there is little to suggest how such studies should be executed in practice. Typically the choice is between the approaches of the historicised case study and statistical analysis of large populations which examine the relationship between environment and organisation strategy and/or structure and ignore the product-process relationship. This study combines the historicised case study and the multi-variable and ordinal scale approach of statistical analysis to construct an analytical framework which tracks and exposes the environment-organisation-performance relationship over time. The framework examines changes in the environment, strategy and structure and uniquely includes an assessment of the organisation's product-process relationship and its contribution to organisational efficiency and innovation. The analytical framework is applied to examine the evolving environment-organisation relationship of two organisations in the same industry over the same twenty-five year period to provide a sector perspective of organisational adaptation. The findings demonstrate the significance of the environment-organisation configuration to the scope and frequency of adaptation and suggest that the level of sector homogeneity may be linked to the level of product-process standardisation.

Interocular transfer of spatial adaptation is weak at low spatial frequencies

Adapting one eye to a high contrast grating reduces sensitivity to similar target gratings shown to the same eye, and also to those shown to the opposite eye. According to the textbook account, interocular transfer (IOT) of adaptation is around 60% of the within-eye effect. However, most previous studies on this were limited to using high spatial frequencies, sustained presentation, and criterion-dependent methods for assessing threshold. Here, we measure IOT across a wide range of spatiotemporal frequencies, using a criterion-free 2AFC method. We find little or no IOT at low spatial frequencies, consistent with other recent observations. At higher spatial frequencies, IOT was present, but weaker than previously reported (around 35%, on average, at 8c/deg). Across all conditions, monocular adaptation raised thresholds by around a factor of 2, and observers showed normal binocular summation, demonstrating that they were not binocularly compromised. These findings prompt a reassessment of our understanding of the binocular architecture implied by interocular adaptation. In particular, the output of monocular channels may be available to perceptual decision making at low spatial frequencies.

Stereoacuity as an indicator of prism adaptation

Purpose: The purpose of this study was to determine whether stereoacuity can be used as an indicator of prism adaptation. In particular, we wanted to know whether the time required for stereoacuity to return to the initial level after viewing through a prism can be used to determine the degree of adaptation. Materials and Methods: Eighteen subjects participated in this study. Stereoacuity and dissociated phoria were determined using the TNO stereotest and the Maddox rod, respectively. Prism vergences were measured using a prism bar. For each participant, prism power equivalent to the blur point of base-in (BI) and base-out (BO) fusional vergence at 40 cm was divided and placed in front of both eyes. At 0, 3, 6, 9 and 12 min after prism introduction, the stereoacuity was measured, and at 0 and 12 min, the heterophoria was measured. Results: The repeated measures ANOVA showed a significant difference between the mean stereoacuity for BI and BO prisms at the different measurement times (p < 0.05). For BO prism, the initial value was different between 0 and 3 min after the prism introduction, whereas for BI prism, a difference in stereoacuity was found between the pre-prism value and the value at 0, 3 and 6 min. The size of the heterophoria with BO and BI prisms was different from 0 to 12 min (p < 0.05). Conclusion: The time required for stereoacuity to return to baseline level was more than 3 min for BO, and more than 6 min for BI prism. In addition, the time required to return to baseline values was not similar for the stereoacuity and heterophoria. The recovery of stereoacuity is slower when adapting to divergence, as when looking from near to far. This implies that stereopsis responds faster to near targets than to distant one, and may precede complete phoria adaptation. © 2014 Informa Healthcare USA, Inc. All rights reserved: reproduction in whole or part not permitted.

Resilience and adaptation of small and medium-sized enterprises to flood risk

Purpose – The UK has experienced a number of flood events in recent years, and the intensity and frequency of such events are forecast to further increase in future due to changing climatic conditions. Accordingly, enhancing the resilience of small and medium-sized enterprises (SMEs) – which form an important segment in a society – to flood risk, has emerged as an important issue. However, SMEs often tend to underestimate the risk of flooding which tends to have a low priority in their business agenda. The purpose of this paper is to undertake an investigation of adaptation to the risk of flooding considering community-level measures, individual-level property protection, and business continuity and resilience measures. Design/methodology/approach – A total of four short case studies were conducted among SMEs to identify their response to flood risk, and what measures have been undertaken to manage the risk of flooding. Findings – It was observed that SMEs have implemented different property-level protection measures and generic business continuity/risk management measures, based on their requirements, to achieve a desired level of protection. Practical implications – SMEs are likely to positively respond to property-level adaptation following a post-flood situation. It is important that information such as costs/benefits of such measures and different options available are made accessible to SMEs affected by a flood event. Social implications – Implementation of property-level adaptation measures will contribute towards the long term adaptation of the existing building stock to changing climatic conditions. Originality/value – The paper contributes towards policy making on flood risk adaptation and SME decision making, and informs policy makers and practitioners.