High-level Areas Research Articles

Temporal tuning of repetition suppression across the visual cortex.

The visual system adapts to its recent history. A phenomenon related to this is repetition suppression (RS), a reduction in neural responses to repeated compared with nonrepeated visual input. An intriguing hypothesis is that the timescale over which RS occurs across the visual hierarchy is tuned to the temporal statistics of visual input features, which change rapidly in low-level areas but are more stable in higher level areas. Here, we tested this hypothesis by studying the influence of the temporal lag between successive visual stimuli on RS throughout the visual system using functional (f)MRI. Twelve human volunteers engaged in four fMRI sessions in which we characterized the blood oxygen level-dependent response to pairs of repeated and nonrepeated natural images with interstimulus intervals (ISI) ranging from 50 to 1,000 ms to quantify the temporal tuning of RS along the posterior-anterior axis of the visual system. As expected, RS was maximal for short ISIs and decayed with increasing ISI. Crucially, however, and against our hypothesis, RS decayed at a similar rate in early and late visual areas. This finding challenges the prevailing view that the timescale of RS increases along the posterior-anterior axis of the visual system and suggests that RS is not tuned to temporal input regularities.NEW & NOTEWORTHY Visual areas show reduced neural responses to repeated compared with nonrepeated visual input, a phenomenon termed repetition suppression (RS). Here we show that RS decays at a similar rate in low- and high-level visual areas, suggesting that the short-term decay of RS across the visual hierarchy is not tuned to temporal input regularities. This may limit the specificity with which the mechanisms underlying RS could optimize the processing of input features across the visual hierarchy.

Network Representations of Facial and Bodily Expressions: Evidence From Multivariate Connectivity Pattern Classification.

Emotions can be perceived from both facial and bodily expressions. Our previous study has found the successful decoding of facial expressions based on the functional connectivity (FC) patterns. However, the role of the FC patterns in the recognition of bodily expressions remained unclear, and no neuroimaging studies have adequately addressed the question of whether emotions perceiving from facial and bodily expressions are processed rely upon common or different neural networks. To address this, the present study collected functional magnetic resonance imaging (fMRI) data from a block design experiment with facial and bodily expression videos as stimuli (three emotions: anger, fear, and joy), and conducted multivariate pattern classification analysis based on the estimated FC patterns. We found that in addition to the facial expressions, bodily expressions could also be successfully decoded based on the large-scale FC patterns. The emotion classification accuracies for the facial expressions were higher than that for the bodily expressions. Further contributive FC analysis showed that emotion-discriminative networks were widely distributed in both hemispheres, containing regions that ranged from primary visual areas to higher-level cognitive areas. Moreover, for a particular emotion, discriminative FCs for facial and bodily expressions were distinct. Together, our findings highlight the key role of the FC patterns in the emotion processing, indicating how large-scale FC patterns reconfigure in processing of facial and bodily expressions, and suggest the distributed neural representation for the emotion recognition. Furthermore, our results also suggest that the human brain employs separate network representations for facial and bodily expressions of the same emotions. This study provides new evidence for the network representations for emotion perception and may further our understanding of the potential mechanisms underlying body language emotion recognition.

المخاطر الجيومورفولوجية للسيول وأثرها في تغير الفئات الانحدارية لمناطق شرق العراق لمحافظتي واسط – والعمارة (دراسة حالة)

The objective of this study is to determine the geomorphological risks of the floods and their effect on changing the slope categories of the eastern regions of Iraq within Wassit and Maysan governorates. The study investigated the slope characteristics of the gradients and their trends, (ARC GIS 10.4), employing application programs and using topographic maps of the survey area (100000: 1). The applied equations were used to extract the intensity of water erosion and the size of erosion through application Equation (Douglass) and (Fournier) and equation (Bergsma) for Rift erosion (2000) and the SRTM (2014) model, which obtained the model of digital elevation by means of US satellite data. Comparison of the regression maps extracted from the two previous models shows that there is a clear variation between the categories. The category (0-1,9), which occupies an area of ​​25451.42 km2, is highlighted in the figure (flat surface) using the model (1996, GTOPO30) Using the SRTM model, it was found to be between 0-1.9, occupying an area of ​​32,614,43 km2, G in the flat surface It is clear from the difference in area that the heterogeneity between the surface and the high-level areas is apparent. The study area includes Wasit and Amara Governorates, which are part of the flood plain, which are located between the latitude (00 00-00 40 33 North) and the longitude (10,956.7 m). The area was characterized by varying degrees of regression according to Zink classification. Ranged between flat areas with a flat surface (0-1.9) to mountainous regions, With a high score of (more than 30)degree The direction of the gradient was determined as the trend of the south-east reached an area of ​​9779.81 km2 and 28.84%. The river levels reached 7 levels and were used to extract the amount of erosion. The water erosion was calculated by applying the equation (Doklas) and reached the highest limit in the station Badra up to (5,8), which is high value of the size of erosion, and applied the equation Vorneh for the evaluation of the severity of the tariff, as above in the station Badra (40.1 m / km 2) , While the study area was divided according to the law (Bergsma) to five degrees and it was determined that the degree of erosion of the fourth very high-scale is prevailing within the The area of ​​the study is 17979,74 km2, hence the reciprocal relationship between the slope categories, water erosion and the intensity of the floods.,.,

Wintering home range and habitat use of the whooper swans (Cygnus cygnus) in Sanmenxia Wetland, China

AbstractsHome range and habitat use are the central components of avian ecology, and studies on these aspects will be helpful for the conservation and management of avian populations. Sixty‐seven swans were global positioning system tagged at Sanmenxia Wetland of Henan Province to obtain detailed location data in winter from 2015 to 2016. The home range size of swans was the largest in the middle wintering period and followed by the early period and late period, and sizes were significantly different among the three wintering periods. There were significant differences in habitat use among the different wintering periods. In the early period, the swans mainly used the aquatic grasses and emergent plants zones, and they mainly relied on artificial supplementation because of a lack of natural feeding habitats in the middle period. In the late period, the swans mainly used the newly emerged terrestrial grasses zone. Except for the deep water, the use of other water levels was significantly different among the different wintering periods. In the early wintering period, the swans tended to prefer the low and high water level areas; in the middle period, they were mainly in the intermediate and high water level areas and they used all the water level areas except the deep water level in the late wintering period. It was concluded that some plants are preferred by the swans, such as reeds, cattails and barnyard grass, and that water depth should be suitable for the swans, with the water levels varying over a gradient.

Landslide Risk Reduction by Using Geographic Information System in District Kaligesing, Purworejo Regency

Landslide takes a charge about 614 phenomenon with 3,5 milion more victims as long as 2017 in Indonesia. This study aims to: 1) take a measurement of landslide risk level in District Kaligesing, Purworejo Regency, and 2) to arrange alternatives of landslide risk reduction in District Kaligesing, Purworejo Regency. This is a descriptive quantitative research with GIS analysis using Arc.GIS 10.3 application. This study uses spatial and ecological approach. This population study is 147 landuse units. This study using primary data to measure the capacity level of society on disaster and secondary data to measure the vulnerability level. Data collection using observation, documentation, and interview methods. The data analysis techniques is using GIS analysis by scoring and overlay. The results shows that: 1) the variation of landslide risk level in District Kaligesing, Purworejo Regency divided into three classes: high level (9,41 km2), medium level (37,55 km2), and low level (28,94 km2). The percentage of high level is 12.40%, percentage of medium level is 49.47%, and percentage of low level is 38.13%. The highest risk level of landslides is located in Donorejo covering 6.77 km2 or 71.92% of the high-level area and the lowest risk level of landslides is located in Sudorogo covering 0.17 km2 or 0.59% of the low-level areas; 2) the alternatives advice of landslide prevention given through preventive and persuasive methods. The prevention methods such as make any limitation of building plan, and relocation in higher-level areas, infrastructure development at the moderate level, and establishment of sister s and integrated evacuation sites in low-level institutions. Persuasive methods done through grinding functions with disaster management organizations, forming community-based and using social media to give more access information related to landslide disaster.

MON-374 Composite Pheochromocytoma: Look and You Shall Find...

Background: Composite pheochromocytoma (CP) is a rare tumor which is composed of pheochromocytoma (or paraganglioma) and a non-pheochromocytoma component of similar embryonic origin, such as ganglioneuroma, ganglioneuroblastoma, neuroblastoma, malign schwanoma and neuroendocrine carcinomas. : We report two cases of adrenal CP with association of pheochromocytoma and ganglioneuromas followed in the Endocrine and Pathology Services of our institution. Case 1: A 39-year-old female, evaluated in August/2003 with clinical signs of adrenergic hypersecretion, a predominance of paroxysmal hypertension, and biochemical exams suggestive of pheochromocytoma with a preponderance of altered urinary levels of adrenaline and noradrenaline. The abdominal computed tomography showed a heterogenous nodular expansive lesion with 3.9 cm in the left adrenal and the right gland with normal aspect. She was submitted to a left video laparoscopic adrenalectomy preceded by alpha-blocker preparation. The histopathological diagnosis was pheochromocytoma associated with ganglioneuroma and the post-surgical follow-up has presented no intercurrences. Case 2: A 29-year-old female, evaluated in January/2018 for abdominal pain, fatigue, and diarrhea, without arterial hypertension. Abdominal ultrasound showed a heterogeneous nodular isoechoic lesion of 68 x 55 mm in the right adrenal. Magnetic resonance imaging confirmed the lesion of 72 x 65 x 69 mm with a hemorrhagic area of high protein level of 32 x 23 mm. Biochemistry was characterized by altered levels of free plasmatic adrenaline and noradrenaline. She was submitted to a right video laparoscopic adrenalectomy. The histopathological diagnosis was pheochromocytoma and areas of peripheric differentiation of ganglioneuroma. Conclusion: The association of pheochromocytoma with tumors of similar embryonic origin most frequently involves ganglioneuromas - present as the second component in 70% of the cases of CP. Our two cases, despite the pathological similarity, had different clinical presentation and progression. Nevertheless, considering the embryonic origin, the authors question the rare character of CP and wonder if this tumor is not underdiagnosed in clinical practice.

Short-term effect of PM2.5/O3 on non-accidental and respiratory deaths in highly polluted area of China

ObjectiveTo investigate the effects of short-term exposure to PM2.5 and ozone in high-level areas on respiratory deaths and non-accidental deaths. MethodsTime-series analysis was used to investigate the association between PM2.5/O3 and non-accidental deaths and respiratory deaths at Hefei, China from 2013 to 2015. ResultsPM2.5 and O3 exposure were associated with elevated non-accidental and respiratory deaths. With every 10 μg/m3 increase in PM2.5, the rate of respiratory deaths and non-accidental deaths increased by 1.24% (95%CI: 0.29%–2.20%) and 0.36% (95%CI: 0.10%–0.63%), respectively. In addition, every 10 μg/m3 increase in ozone also associated with 2.22% (95%CI: 0.56%–3.90%) and 0.05% (95%CI: 0.42%-0.53%) increase in respiratory deaths and non-accidental deaths, respectively. The analysis of multi-pollutant model showed that the inclusion of ozone further increased the effects of PM2.5 on respiratory deaths. The inclusion of PM2.5 decreased the effects of O3 on respiratory deaths. In addition, the effects of PM2.5/O3 on daily respiratory and non-accidental deaths were more evident in the cold season, females and elderlies (65 years or older). ConclusionsShort-term exposure of high-level PM2.5 and ozone increased the risk of respiratory and non-accidental deaths. Females and elderlies are more susceptible to PM2.5/O3 exposure.

Total Dissolved Solids in Water in Makurdi along Benue Valley-Nigeria: Effects on Potability and Compressive Strengths of Solid Concrete

Potable water is a scarce resource in many parts of the world. Also, construction works in modern-day buildings need strength to withstand various loads – and concrete’s versatility makes it an ideal material where strength is of importance. Water is a crucial binder in concrete making. A laboratory-controlled experimental approach was used to determine the effect of Total Dissolved Solids (TDS) in the water on the compressive strength of solid concretes in Makurdi and its metropolis. A concrete mix ratio of 1:2:3 was used for the experiment. Water samples were collected from rivers (uphill and downhill of River Benue) and wells in Wurukum, Wadata, High Level and North Bank areas of Makurdi and their TDS measured, using a digital TDS meter. Concrete cubes of uniform dimensions were cast with water from each water source and cured for 28 days. We found out that compressive strengths increased with time and peaked around the 28th day. The mass per litre of the dissolved solids does not appear to affect the compressive strength in a linear pattern, pointing to the nature of the dissolved solids as being responsible for the differences in the compressive strengths. Further study is recommended.

Elderly dementia patients, socioeconomic settings, care management and ICT adoption

Objective: This study investigated the socioeconomic characteristics of dementia patients in Greece and assessed whether these factors influence their healthcare. Methods: A cross-sectional observational study design was used. In total, data from 779 elderly dementia patients were reviewed. Results: On the whole, a larger proportion of primary health care facilities were used by patients with no educational level (Odds Ratio=10.91; 95%; Confidence Interval=3.21–37.14) or no/little income adequacy (Odds Ratio=2.13; 95%; Confidence Interval=1.18–3.86). Moreover, patients with a lower economic status (€0–6000) used primary health care facilities at a lower level (Odds Ratio=0.22; 95%; Confidence Interval=0.12–0.39). After controlling for confounding effects with a logistic regression method, tertiary education (Odds Ratio=7.68; 95%; Confidence Interval=2.76–21.35) was also a factor determining the frequency of patients visiting social care services, as was a higher economic status. In a logistic regression model, a higher educational level and rural areas were related to the use of information and communication technology and their devices (Odds Ratio=65.68; 95%; Confidence Interval=7.22–597.12, tertiary education) and (Odds Ratio=0.16; 95%; Confidence Interval=0.05–0.56). Conclusions: Socioeconomic status and area of residence are two major factors that affect various aspects of dementia care, while accessibility and availability of health structures determine the type of health care patients receive.

The Spatial and Heterogeneity Impacts of Population Urbanization on Fine Particulate (PM2.5) in the Yangtze River Economic Belt, China.

This paper addresses the effect of population urbanization on Fine Particulate (PM2.5) in the Yangtze River Economic Belt in China from 2006 to 2016 by employing PM2.5 remote sensing data and using the Stochastic Impacts by Regression on Population, Affluence and Technology (STIRPAT) model. The study contributes to the growing empirical literature by addressing heterogeneity, spillover, and dynamic effects in the dynamic spatial panel modeling process simultaneously. The empirical results show that population urbanization has a significant impact on PM2.5 with a positive spillover effect and a dynamic effect being detected and controlled. The heterogeneity effects of population urbanization on PM2.5 due to geographical positions show evidence of an obvious inverted U-shaped curve relationship in the upstream area and an increasing function curve in the midstream and downstream areas. The heterogeneity effects due to population urbanization levels show that an inverted N-shape curve relationship exists in low and medium urbanization level areas, while a U-shape curve relationship exists in high urbanization level areas. It is hoped that this study will inform the local governments about the heterogeneity of population urbanization and spillover effects of air pollution when addressing air pollution control.

Governance and disaster: Analysis of land use policy with reference to Uttarakhand flood 2013, India

The flood risks are crucially increasing in developing countries around the globe due to intense development activities and climate change. The extreme casualties and losses wrought by the flood events in June 2013 in the Uttarakhand (India) have raised the governance issues in policy-making and implementation for controlling human activities. Besides extreme rainfall, the unplanned development, weak legal framework and governance issues were claimed as responsible for triggering the disaster. The present study has evaluated the environmental aspects of existing policies related to regulate land use change and development activities when considered in relation to flooding. Analyzing the governance perspective by addressing policy, guidelines and mitigation strategies, this study highlighted the gaps in policies and practice that could be reshaped to reinforce resilience. This study also tried to delineate the high flood level and flood risk area along the Bhagirathi river using hydrological and hydrodynamic models for the event of 2013 that can assist in policy-making process. In summary, the study found that rampant construction at riverside in absence of effective building regulations and hydropower policy in the state has increased the magnitude of the disaster. The lack of multi-institutional coordination in formulating and practice of regulatory measures was found as a failure of governance in disaster preparedness and flood management. This study strongly suggests for compliance of local planning authorities and stakeholders with state and national policymakers for establishing collaborative governance. This article may help to bridge the gap between administrators and researcher for formulizing effective flood risk governance.

Spatial Distribution of Urban Transportation Capacity and Its Influencing Factors: A Case Study of Guangdong

Using spatial autocorrelation analysis method, the spatial and temporal evolution of the overall development of Guangdong’s transportation capacity during 2001-2016 is analyzed. There is no large displacement between high-level and low-level agglomeration areas between cities, and there is obvious path dependence. According to the development level of transportation capacity of 21 prefecture-level cities in 2010-2016, the factors affecting the development level of transportation capacity are discussed. The results show that: Guangdong’s overall transportation capacity has increased with time, and transportation resources have been concentrated in Guangzhou in recent years. Cities in the high-level transportation capacity segment and cities in the low-level transportation capacity segment are relatively fixed, and there is path dependence; transportation fixed assets investment, transportation industry employees, and economic development level improve the transportation capacity. There is a significant positive impact; government fiscal expenditure and industrial structure have a significant negative impact on transportation development, reflecting the ineffectiveness and mismatch in the process of government fiscal expenditure and the unreasonable industrial structure; population density has no obvious development of transportation capacity. As the population density increases, traffic congestion in the city will not produce a good effect on the improvement of transportation capacity.

Vestibular System and Self-Motion.

Detection of the state of self-motion, such as the instantaneous heading direction, the traveled trajectory and traveled distance or time, is critical for efficient spatial navigation. Numerous psychophysical studies have indicated that the vestibular system, originating from the otolith and semicircular canals in our inner ears, provides robust signals for different aspects of self-motion perception. In addition, vestibular signals interact with other sensory signals such as visual optic flow to facilitate natural navigation. These behavioral results are consistent with recent findings in neurophysiological studies. In particular, vestibular activity in response to the translation or rotation of the head/body in darkness is revealed in a growing number of cortical regions, many of which are also sensitive to visual motion stimuli. The temporal dynamics of the vestibular activity in the central nervous system can vary widely, ranging from acceleration-dominant to velocity-dominant. Different temporal dynamic signals may be decoded by higher level areas for different functions. For example, the acceleration signals during the translation of body in the horizontal plane may be used by the brain to estimate the heading directions. Although translation and rotation signals arise from independent peripheral organs, that is, otolith and canals, respectively, they frequently converge onto single neurons in the central nervous system including both the brainstem and the cerebral cortex. The convergent neurons typically exhibit stronger responses during a combined curved motion trajectory which may serve as the neural correlate for complex path perception. During spatial navigation, traveled distance or time may be encoded by different population of neurons in multiple regions including hippocampal-entorhinal system, posterior parietal cortex, or frontal cortex.

ASPECTS OF DIAGNOSTIC ACTIVITIES IN PATIENTS WITH DYSFUNCTION OF TEMPOROMANDIBULAR JOINTS AND SIGNS OF BRUXISM

Aim. The research was conducted to develop and implement the complex of diagnostic activities in patients with dysfunction of temporomandibular joints with signs of bruxism.Materials and methods. To achieve this aim we conducted a comprehensive diagnosis of 61 patients aged 20-29 years with bruxism and temporomandibular joints dysfunction (TMJD), the patients were divided into two groups. To diagnose and analyze the results of the disease treatment in patients we used a computer analysis with visualization of changes of the osteoarticular surface and parameters of the joint gap in the TMJ. Depending on the ratio of prognostic risk criteria and the development of bruxism, we distinguished the area of low, medium and high level of risk of disease progression.Results. Comparison of the treatment results of patients with bruxism from two groups in 12-24 months showed that patients from the second group had good treatment results. Patients of the second group underwent a complex of diagnostic activities and its data increased the treatment effectiveness. The results obtained from the treatment of patients from the first group indicate the lack of data from the standard examination of patients with bruxism.Conclusion. The developed complex diagnostic activities in patients with bruxism in combination with dysfunction of the TMJ and occlusive attrition of teeth allow to assess not only the local status but also to determine the functional state of dentoalveolar system and the cerebral cortex which affects the amount of therapeutic activities in the patient.

Construction and Level Measurement of the Evaluation Index System of Heilongjiang Province’s Coordinated Development Between Green and Low-carbon for New Urbanization

This paper takes Heilongjiang Province as an example to construct the evaluation index system of Heilongjiang Province's coordinated development between green and low-carbon for new urbanization. The entropy weight method was used to measure the coordinated development level of green and low-carbon for new urbanization in 12 prefecture-level cities in Heilongjiang Province. The results show that Harbin is the highest level area of coordinated development between green and low-carbon for new urbanization, Daqing and Qiqihaer belong to the higher level areas of coordinated development between green and low-carbon for new urbanization, Mudanjiang and Jiamusi belong to the lower level areas of coordinated development between green and low-carbon for new urbanization, Jixi, Yichun, Shuangyashan, Qitaihe, Hegang, Suihua and Heihe belong to the lowest level areas of coordinated development between green and low-carbon for new urbanization.

Visualization of information encoded by neurons in the higher-level areas of the visual system

This paper introduces an application of artificial neural networks for visualization of functions of neurons in the higher visual areas of the brain. First, a model that enables the prediction of an evoked neural response was implemented. The model has a correlation coefficient of up to 0.82 for certain cortical columns. Then, an approach to explaining representations encoded by neurons was proposed. The approach is based on generating images maximizing an activation in the model. A comparison of the visualization results with the experimental data suggests that the approach can be used to study the properties of the higher-level areas of the visual cortex.

Parietal Representations of Stimulus Features Are Amplified during Memory Retrieval and Flexibly Aligned with Top-Down Goals.

In studies of human episodic memory, the phenomenon of reactivation has traditionally been observed in regions of occipitotemporal cortex (OTC) involved in visual perception. However, reactivation also occurs in lateral parietal cortex (LPC), and recent evidence suggests that stimulus-specific reactivation may be stronger in LPC than in OTC. These observations raise important questions about the nature of memory representations in LPC and their relationship to representations in OTC. Here, we report two fMRI experiments that quantified stimulus feature information (color and object category) within LPC and OTC, separately during perception and memory retrieval, in male and female human subjects. Across both experiments, we observed a clear dissociation between OTC and LPC: while feature information in OTC was relatively stronger during perception than memory, feature information in LPC was relatively stronger during memory than perception. Thus, while OTC and LPC represented common stimulus features in our experiments, they preferentially represented this information during different stages. In LPC, this bias toward mnemonic information co-occurred with stimulus-level reinstatement during memory retrieval. In Experiment 2, we considered whether mnemonic feature information in LPC was flexibly and dynamically shaped by top-down retrieval goals. Indeed, we found that dorsal LPC preferentially represented retrieved feature information that addressed the current goal. In contrast, ventral LPC represented retrieved features independent of the current goal. Collectively, these findings provide insight into the nature and significance of mnemonic representations in LPC and constitute an important bridge between putative mnemonic and control functions of parietal cortex.SIGNIFICANCE STATEMENT When humans remember an event from the past, patterns of sensory activity that were present during the initial event are thought to be reactivated. Here, we investigated the role of lateral parietal cortex (LPC), a high-level region of association cortex, in representing prior visual experiences. We find that LPC contained stronger information about stimulus features during memory retrieval than during perception. We also found that current task goals influenced the strength of stimulus feature information in LPC during memory. These findings suggest that, in addition to early sensory areas, high-level areas of cortex, such as LPC, represent visual information during memory retrieval, and that these areas may play a special role in flexibly aligning memories with current goals.

Inferotemporal cortex multiplexes behaviorally-relevant target match signals and visual representations in a manner that minimizes their interference.

Finding a sought visual target object requires combining visual information about a scene with a remembered representation of the target to create a “target match” signal that indicates when a target is in view. Target match signals have been reported to exist within high-level visual brain areas including inferotemporal cortex (IT), where they are mixed with representations of image and object identity. However, these signals are not well understood, particularly in the context of the real-world challenge that the objects we search for typically appear at different positions, sizes, and within different background contexts. To investigate these signals, we recorded neural responses in IT as two rhesus monkeys performed a delayed-match-to-sample object search task in which target objects could appear at a variety of identity-preserving transformations. Consistent with the existence of behaviorally-relevant target match signals in IT, we found that IT contained a linearly separable target match representation that reflected behavioral confusions on trials in which the monkeys made errors. Additionally, target match signals were highly distributed across the IT population, and while a small fraction of units reflected target match signals as target match suppression, most units reflected target match signals as target match enhancement. Finally, we found that the potentially detrimental impact of target match signals on visual representations was mitigated by target match modulation that was approximately (albeit imperfectly) multiplicative. Together, these results support the existence of a robust, behaviorally-relevant target match representation in IT that is configured to minimally interfere with IT visual representations.

Serial dependence in the perception of visual variance.

The recent history of perceptual experience has been shown to influence subsequent perception. Classically, this dependence on perceptual history has been examined in sensory-adaptation paradigms, wherein prolonged exposure to a particular stimulus (e.g., a vertically oriented grating) produces changes in perception of subsequently presented stimuli (e.g., the tilt aftereffect). More recently, several studies have investigated the influence of shorter perceptual exposure with effects, referred to as serial dependence, being described for a variety of low- and high-level perceptual dimensions. In this study, we examined serial dependence in the processing of dispersion statistics, namely variance—a key descriptor of the environment and indicative of the precision and reliability of ensemble representations. We found two opposite serial dependences operating at different timescales, and likely originating at different processing levels: A positive, Bayesian-like bias was driven by the most recent exposures, dependent on feature-specific decision making and appearing only when high confidence was placed in that decision; and a longer lasting negative bias—akin to an adaptation aftereffect—becoming manifest as the positive bias declined. Both effects were independent of spatial presentation location and the similarity of other close traits, such as mean direction of the visual variance stimulus. These findings suggest that visual variance processing occurs in high-level areas but is also subject to a combination of multilevel mechanisms balancing perceptual stability and sensitivity, as with many different perceptual dimensions.

Retinal-specific category learning.

Virtually all cognitive theories of category learning (such as prototype theory1-5 and exemplar theory6-8) view this important skill as a high-level process that uses abstract representations of objects in the world. Because these representations are removed from visual characteristics of the display, such theories suggest that category learning occurs in higher-level (such as association) areas and therefore should be immune to the visual field dependencies that characterize processing of objects mediated by representations in low-level visual areas. Here we challenge that view by describing a fully controlled demonstration of visual-field dependence in category learning. Eye-tracking was used to control gaze while participants either learned rule-based categories known to recruit prefrontal-based explicit reasoning, or information-integration categories known to depend on basal-ganglia-mediated procedural learning9. Results showed that learning was visual-field dependent with information-integration categories, but we found no evidence of visual-field dependence with rule-based categories. A theoretical interpretation of this difference is offered in terms of the underlying neurobiology. Finally, these results are situated within the broad perceptual-learning literature in an attempt to motivate further research on the similarities and differences between category and perceptual learning.