Top Halves Research Articles

3D Modeling of interactions between Jupiter’s ammonia clouds and large anticyclones

The motions of Jupiter’s tropospheric jets and vortices are made visible by its outermost clouds, which are expected to be largely composed of ammonia ice. Several groups have demonstrated that much of this dynamics can be reproduced in the vorticity fields of high-resolution models that, surprisingly, do not contain any clouds. While this reductionist approach is valuable, it has natural limitations. Here we report on numerical simulations that use the EPIC Jupiter model with a realistic ammonia-cloud microphysics module, focusing on how observable ammonia clouds interact with the Great Red Spot (GRS) and Oval BA. Maps of column-integrated ammonia-cloud density in the model resemble visible-band images of Jupiter and potential-vorticity maps. On the other hand, vertical cross sections through the model vortices reveal considerable heterogeneity in cloud density values between pressure levels in the vicinity of large anticyclones, and interestingly, ammonia snow appears occasionally. Away from the vortices, the ammonia clouds form at the levels expected from traditional one-dimensional models, and inside the vortices, the clouds are elevated and thick, in agreement with Galileo NIMS observations. However, rather than gathering slowly into place as a result of Jupiter’s weak secondary circulation, the ammonia clouds instead form high and thick inside the large anticyclones as soon as the cloud microphysics module is enabled. This suggests that any weak secondary circulation that might be present in Jupiter’s anticyclones, such as may arise because of radiative damping of their temperature anomalies, may have little or no direct effect on the altitude or thickness of the ammonia clouds. Instead, clouds form at those locations because the top halves of large anticyclones must be cool for the vortex to be able to fit under the tropopause, which is a primary-circulation, thermal-wind-shear effect of the stratification, not a secondary-circulation thermal feature. A planetary-scale void of ammonia clouds persists in the model southward of -38° planetographic latitude, but may partially reflect the fact that we have not yet included a full complement of vortices, all condensable species or the underlying dry-convective forcing from Jupiter’s interior.

Comparison of Portland Cement (KS and API Class G) on Cement Carbonation for Carbon Storage

AbstractPortland cement is a common sealing material used in wellbores for geological carbon sequestration. Two types of portland cement were reacted with carbon dioxide (CO2) in supercritical, gaseous, and aqueous phases, under various pressure and temperature conditions, to simulate a cement-CO2 reaction along the wellbore from the carbon injection depth to the near surface. In this study, two types of cement were used: Korean Standard (KS) portland cement (Type I) and American Petroleum Institute (API) class G portland cement. The top halves of hydrated portland cement sample columns (14-mm diameter×90-mm long;water-to-cement ratio=0.5), including additives such as fly ash, were reacted with CO2 in an unsaturated (dry, no contact with water) condition. The bottom halves of the columns were reacted with CO2 in a saturated (wet, in contact with water) condition. These conditions were maintained under high pressure (8 MPa) and temperature (40°C) for 10 and 100 days to determine the potential of this pr...

Resource boom and inequality: Kazakhstan as a case study

Our research investigates the impact of a major resource boom on income inequality within Kazakhstan's regions using household-level data across the entire income distribution and within the top and bottom halves of the income distribution. In addition, we evaluate the inequality dynamics separately in urban and rural areas. The theoretical foundation shows that a resource boom will decrease income inequality through the labor market if the non-traded sector is relatively intensive in its use of unskilled labor. Government transfers financed by resource income can further reduce inequality. Our regression analysis indicates that resource booms lower inequality when we control for the effect of changing labor income, institutional quality, education levels, and public health care spending. In addition, quality of institutions is an important equalizing factor for the lower income households in urban areas, but not in rural areas. Public health programs decrease overall inequality in the rural areas; however, they do not affect the bottom half of the income distribution.

Prism adaptation does not alter configural processing of faces

Patients with hemispatial neglect (‘neglect’) following a brain lesion show difficulty responding or orienting to objects and events on the left side of space. Substantial evidence supports the use of a sensorimotor training technique called prism adaptation as a treatment for neglect. Reaching for visual targets viewed through prismatic lenses that induce a rightward shift in the visual image results in a leftward recalibration of reaching movements that is accompanied by a reduction of symptoms in patients with neglect. The understanding of prism adaptation has also been advanced through studies of healthy participants, in whom adaptation to leftward prismatic shifts results in temporary neglect-like performance. Interestingly, prism adaptation can also alter aspects of non-lateralised spatial attention. We previously demonstrated that prism adaptation alters the extent to which neglect patients and healthy participants process local features versus global configurations of visual stimuli. Since deficits in non-lateralised spatial attention are thought to contribute to the severity of neglect symptoms, it is possible that the effect of prism adaptation on these deficits contributes to its efficacy. This study examines the pervasiveness of the effects of prism adaptation on perception by examining the effect of prism adaptation on configural face processing using a composite face task. The composite face task is a persuasive demonstration of the automatic global-level processing of faces: the top and bottom halves of two familiar faces form a seemingly new, unknown face when viewed together. Participants identified the top or bottom halves of composite faces before and after prism adaptation. Sensorimotor adaptation was confirmed by significant pointing aftereffect, however there was no significant change in the extent to which the irrelevant face half interfered with processing. The results support the proposal that the therapeutic effects of prism adaptation are limited to dorsal stream processing.

Prism adaptation does not alter configural processing of faces.

Patients with hemispatial neglect ('neglect') following a brain lesion show difficulty responding or orienting to objects and events on the left side of space. Substantial evidence supports the use of a sensorimotor training technique called prism adaptation as a treatment for neglect. Reaching for visual targets viewed through prismatic lenses that induce a rightward shift in the visual image results in a leftward recalibration of reaching movements that is accompanied by a reduction of symptoms in patients with neglect. The understanding of prism adaptation has also been advanced through studies of healthy participants, in whom adaptation to leftward prismatic shifts results in temporary neglect-like performance. Interestingly, prism adaptation can also alter aspects of non-lateralised spatial attention. We previously demonstrated that prism adaptation alters the extent to which neglect patients and healthy participants process local features versus global configurations of visual stimuli. Since deficits in non-lateralised spatial attention are thought to contribute to the severity of neglect symptoms, it is possible that the effect of prism adaptation on these deficits contributes to its efficacy. This study examines the pervasiveness of the effects of prism adaptation on perception by examining the effect of prism adaptation on configural face processing using a composite face task. The composite face task is a persuasive demonstration of the automatic global-level processing of faces: the top and bottom halves of two familiar faces form a seemingly new, unknown face when viewed together. Participants identified the top or bottom halves of composite faces before and after prism adaptation. Sensorimotor adaptation was confirmed by significant pointing aftereffect, however there was no significant change in the extent to which the irrelevant face half interfered with processing. The results support the proposal that the therapeutic effects of prism adaptation are limited to dorsal stream processing.

Eye-specific information biases perceived direction of bistable motion

While eye-of origin information is normally not accessible to observers, processing of visual information within a monocular channel does contribute to our final percept. Here we investigate if visual information is processed more efficiently when it is contained within a monocular channel or across two eyes and how it affects visual perception. Specifically, we used a bistable apparent motion display, a motion quartet, to investigate the role of eye-specific information in determining perceived motion direction. To an observer, this ambiguous display leads to the perception of either horizontal or vertical motion. We attempted to bias perceived direction by presenting separate spatial halves of the motion quartet to each eye. Our results show that observers were more likely to see horizontal motion when top and bottom halves of the quartet was presented to separate eyes. Similarly, when left and right halves were presented dichoptically, observers reported viewing more vertical motion. This change in proportion of observed motion direction indicates that eye specific information is processed more efficiently and can bias overall perception.

Differential Oculomotor Activity in Young Infants Viewing Pictures of Possible and Impossible Objects

We previously demonstrated that 4-month-old infants responded with increased looking and oculomotor activity toward pictures of impossible cubes relative to possible ones, and they fixated specifically within the critical region of impossible cubes (p<.01) where the anomalous junction occurred, an effect that was not observed reliably in younger infants. This suggested that 4-month-olds selectively respond to local vertices (T-, Y-junctions) diagnostic of global coherence. However, it left open the question of whether 4-month-olds would systematically respond with increased visual interest to other novel impossible figures varying in type of geometric contours (curvilinear vs. straight-edges). We recorded eye movements from 4-month-old infants as they viewed images of possible and impossible objects. We hypothesized that infants would engage in active comparison of the objects, and that impossible figures would evoke increased scanning to ascertain global structural integrity. Infants looked longer (p<.03) and directed a greater number of fixations (p<.05) on impossible relative to possible cubes. Preference scores indicated infants’ partiality for the impossible cube differed from chance (p<.05). The effect of increased visual interest toward impossible figures generalized to other straight-edged stimuli, but not curvilinear ones. Furthermore, across all object pairs, infants initiated a greater number of fixations and looked an average of 300 ms longer in the lower halves of impossible figures relative to their possible mates (p<.05), whereas there were no reliable differences in fixation behavior in the top halves. The high degree of variability in infants’ fixation behaviors may be due to individual differences in selective looking or emerging sensitivity to pictorial depth, or may be a stimulus-dependent response that manifests exclusively with specific shapes (impossible cubes with salient manipulations of T- and Y-junctions). Our findings suggest that several mechanisms for selectively analyzing local depth relations and ascertaining information about global 3D shape develop rapidly in early infancy. Meeting abstract presented at VSS 2013

Better Speech Recognition with Digital RF System in Study of Cochlear Implants

Better Speech Recognition with Digital RF System in Study of Cochlear Implants

Inversion Effects in Face-selective Cortex with Combinations of Face Parts

The face inversion effect has been used as a basis for claims about the specialization of face-related perceptual and neural processes. One of these claims is that the fusiform face area (FFA) is the site of face-specific feature-based and/or configural/holistic processes that are responsible for producing the face inversion effect. However, the studies on which these claims were based almost exclusively used stimulus manipulations of whole faces. Here, we tested inversion effects using single, discrete features and combinations of multiple discrete features, in addition to whole faces, using both behavioral and fMRI measurements. In agreement with previous studies, we found behavioral inversion effects with whole faces and no inversion effects with a single eye stimulus or the two eyes in combination. However, we also found behavioral inversion effects with feature combination stimuli that included features in the top and bottom halves (eyes-mouth and eyes-nose-mouth). Activation in the FFA showed an inversion effect for the whole-face stimulus only, which did not match the behavioral pattern. Instead, a pattern of activation consistent with the behavior was found in the bilateral inferior frontal gyrus, which is a component of the extended face-preferring network. The results appear inconsistent with claims that the FFA is the site of face-specific feature-based and/or configural/holistic processes that are responsible for producing the face inversion effect. They are more consistent with claims that the FFA shows a stimulus preference for whole upright faces.

The composite face illusion: A whole window into our understanding of holistic face perception

Two identical top halves of a face are perceived as being different when their bottom halves belong to different faces, showing that the parts of a face cannot be perceived independently from the whole face. When this visual illusion is inserted in a matching task, observers make more mistakes and/or are slower at matching identical top face halves aligned with different bottom halves than when the bottom halves are spatially offset: The composite face effect. This composite face paradigm has been used in more than 60 studies that have provided information about the specificity and nature of perceptual integration between facial parts (“holistic face perception”), the impairment of this process in acquired prosopagnosia, its developmental course, temporal dynamics, and neural basis. Following a review of the main contributions made with the paradigm, I explain its rationale and strengths, and discuss its methodological parameters, making a number of proposals for its optimal use and refinement in order to improve our understanding of holistic face perception. Finally, I explain how this standard composite face paradigm is fundamentally different than the application to facial parts of a congruency/interference paradigm that has a long tradition in experimental psychology since Stroop (1935), and which was originally developed to measure attentional and response interference between different representations rather than perceptual integration. Moreover, a version of this congruency/interference paradigm used extensively over the past years with composite faces lacks a baseline measure and has decisional, attentional, and stimulus confounds, making the findings of these studies impossible to interpret in terms of holistic perception. I conclude by encouraging researchers in this field to concentrate fully on the standard composite face paradigm, gaze contingency, and other behavioural measures that can help us take one of the most important challenges of visual perception research: Understanding the neural mechanisms of holistic face perception.

Behavioral and neural evidence of increased attention to the bottom half of the face in deaf signers

This study examined the effects of deafness and sign language use on the distribution of attention across the top and bottom halves of faces. In a composite face task, congenitally deaf signers and typically hearing controls made same/different judgments of the top or bottom halves of faces presented with the halves aligned or spatially misaligned, while event-related potentials (ERPs) were recorded. Both groups were more accurate when judging misaligned than aligned faces, which indicates holistic face processing. Misalignment affected all ERP components examined, with effects on the N170 resembling those of face inversion. Hearing adults were similarly accurate when judging the top and bottom halves of the faces, but deaf signers were more accurate when attending to the bottom than the top. Attending to the top elicited faster P1 and N170 latencies for both groups; within the deaf group, this effect was greatest for individuals who produced the highest accuracies when attending to the top. These findings dovetail with previous research by providing behavioral and neural evidence of increased attention to the bottom half of the face in deaf signers, and by documenting that these effects generalize to a speeded task, in the absence of gaze shifts, with neutral facial expressions.

Face Perception is Whole or None: Disentangling the Role of Spatial Contiguity and Interfeature Distances in the Composite Face Illusion

Compelling evidence that faces are perceived holistically or configurally comes from the composite face illusion: identical top halves of a face are perceived as being different if they are aligned with different bottom halves. The visual illusion disappears when the top and bottom face halves are spatially misaligned. Whether this is because the two halves no longer form a whole face (ie they form two segmented parts), or because of an increase in interfeatures distance in the misaligned condition (eg eyes-mouth distance) remains unclear. Here, thirty-four participants performed a delayed matching composite task in which the amount of spatial misalignment between face halves varied parametrically (from 8.33% of face width to 100%). The difference in performance between aligned and misaligned faces (ie the composite face effect) was already of full magnitude at the smallest level of misalignment. These results imply that a small spatial misalignment is sufficient to measure the composite face effect. From a theoretical standpoint, they indicate that it is the breaking of a whole configuration rather than the increase in relative distance between the face parts that explains the presence or absence of the composite face effect, clarifying an outstanding issue concerning the nature of holistic face perception.

Configurational Information in Face Perception

A new facial composites technique is demonstrated, in which photographs of the top and bottom halves of different familiar faces fuse to form unfamiliar faces when aligned with each other. The perception of a novel configuration in such composite stimuli is sufficiently convincing to interfere with identification of the constituent parts (experiment 1), but this effect disappears when stimuli are inverted (experiment 2). Difficulty in identifying the parts of upright composites is found even for stimuli made from parts of unfamiliar faces that have only ever been encountered as face fragments (experiment 3). An equivalent effect is found for composites made from internal and external facial features of well-known people (experiment 4). These findings demonstrate the importance of configurational information in face perception, and that configurations are only properly perceived in upright faces.

Use of2H2O for estimating rates of gluconeogenesis: determination and correction of error due to transaldolase exchange

The use of deuterated water as a method to measure gluconeogenesis has previously been well validated and is reflective of normal human physiology. However, there has been concern since the method was first introduced that transaldolase exchange may lead to the overestimation of gluconeogenesis. We examined the impact of transaldolase exchange on the estimation of gluconenogenesis using the deuterated water method under a variety of physiological conditions in humans by using the gluconeogenic tracer [U-(13)C]propionate, (2)H(2)O, and (2)H/(13)C nuclear magnetic resonance (NMR) spectroscopy. When [U-(13)C]propionate was used, (13)C labeling inequality occurred between the top and bottom halves of glucose in individuals fasted for 12-24 h who were weight stable (n = 18) or had lost weight via calorie restriction (n = 7), consistent with transaldolase exchange. Similar analysis of glucose standards revealed no significant difference in the total (13)C enrichment between the top and bottom halves of glucose, indicating that the differences detected were biological, not analytical, in origin. This labeling inequality was attenuated by extending the fasting period to 48 h (n = 12) as well as by dietary carbohydrate restriction (n = 7), both conditions associated with decreased glycogenolysis. These findings were consistent with a transaldolase effect; however, the resultant overestimation of gluconeogenesis in the overnight-fasted state was modest (7-12%), leading to an error of 14-24% that was easily correctable by using either a simultaneous (13)C gluconeogenic tracer or a correction nomogram generated from data in the present study.

Left–right holistic integration of human bodies

Holistic integration of faces has been widely studied. More recently, investigations have explored whether similar processing is used for human bodies. Here we show that holistic processing, as measured by the composite task, does occur for bodies but is stronger for left and right halves than for top and bottom halves. We also found composite effects for left-right halves of inverted bodies. Standard composite effects were found for top halves of faces, tested as a control. We argue that our results suggest that holistic processing of faces and bodies might not exclusively occur for identification, but instead may also have evolved to aid communication and/or decisions about mate choice (through judging symmetry).

Mixed emotions: Holistic and analytic perception of facial expressions

In the face literature, it is debated whether the identification of facial expressions requires holistic (i.e., whole face) or analytic (i.e., parts-based) information. In this study, happy and angry composite expressions were created in which the top and bottom face halves formed either an incongruent (e.g., angry top + happy bottom) or congruent composite expression (e.g., happy top + happy bottom). Participants reported the expression in the target top or bottom half of the face. In Experiment 1, the target half in the incongruent condition was identified less accurately and more slowly relative to the baseline isolated expression or neutral face conditions. In contrast, no differences were found between congruent and the baseline conditions. In Experiment 2, the effects of exposure duration were tested by presenting faces for 20, 60, 100 and 120 ms. Interference effects for the incongruent faces appeared at the earliest 20 ms interval and persisted for the 60, 100 and 120 ms intervals. In contrast, no differences were found between the congruent and baseline face conditions at any exposure interval. In Experiment 3, it was found that spatial alignment impaired the recognition of incongruent expressions, but had no effect on congruent expressions. These results are discussed in terms of holistic and analytic processing of facial expressions.

The Composite-Face Effect Survives Asymmetric Face Distortions

In two experiments, we investigated whether adults use holistic processing even for faces that are grossly distorted because their eyes have been moved asymmetrically to violate the common layout of a face (distorting its first-order relations). To this end we used a compelling demonstration that faces are processed as wholes, the composite-face effect. Specifically, adults judged the similarity of sequentially presented top halves of normal (original condition) and distorted faces with one eye (one-eye condition) or two eyes (two-eyes condition) shifted up by an abnormal amount. Trials were either blocked by type of distortion (experiment 1) or intermixed within the experiment (experiment 2). In both experiments, participants demonstrated a composite-face effect of the same magnitude in the three conditions, a pattern suggesting that they processed holistically even faces whose first-order relations were violated.

Hemisphere-dependent holistic processing of familiar faces

In two behavioral experiments involving lateralized stimulus presentation, we tested whether one of the most commonly used measures of holistic face processing—the composite face effect—would be more pronounced for stimuli presented to the right as compared to the left hemisphere. In experiment 1, we investigated the composite face effect in a verbal identification task, similar to its original report ( Young, Hellawell, & Hay, 1987). Aligning top and bottom halves of composite face stimuli led to performance decreases irrespective of hemifield, indicating holistic processing of comparable magnitude for inputs provided separately to either hemisphere. However, when matching of the same top parts was required in experiment 2, an alignment-dependent performance decrease was found for stimuli presented in the left, but not right visual field. These observations suggest that the right hemisphere dominates in early stages of holistic processing, as indexed by the composite face effect, but that later processes such as face identification and naming are based on unified representations that are independent of input lateralization. Moreover, the composite face effect may not rely on the exact same representation(s) when measured in matching and identification tasks.

Block tensors and symmetric embeddings

Well known connections exist between the singular value decomposition of a matrix A and the Schur decomposition of its symmetric embedding sym(A)=([0A;AT0]). In particular, if σ is a singular value of A then +σ and -σ are eigenvalues of the symmetric embedding. The top and bottom halves of sym(A)’s eigenvectors are singular vectors for A. Power methods applied to A can be related to power methods applied to sym(A). The rank of sym(A) is twice the rank of A. In this paper we develop similar connections for tensors by building on L.-H. Lim’s variational approach to tensor singular values and vectors. We show how to embed a general order-d tensor A into an order-d symmetric tensor sym(A). Through the embedding we relate power methods for A’s singular values to power methods for sym(A)’s eigenvalues. Finally, we connect the multilinear and outer product rank of A to the multilinear and outer product rank of sym(A).

Evidence for holistic processing of facial age

A composite face, produced by pairing the top and bottom halves from two different faces, produces a strong percept of a “new” face: It is difficult to identify either half in isolation. Three experiments examined whether a similar “composite face effect” (CFE) occurs with age judgements. Composites contained halves from faces of different ages. Participants tried to judge the age of the top half, ignoring the bottom. Experiment 1 found that age estimates for the composites’ top halves were biased towards the bottom halves’ chronological ages. Inverting the stimuli attenuated this effect but did not eliminate it entirely. The CFE for age perception is not based on skin texture information, since it persists when texture is eliminated by blurring or random noise (Experiments 2 and 3). Methodological differences preclude too detailed a comparison with other CFEs, but possibly the CFEs for age, recognition, and expression perception are all based on a common initial “holistic” encoding phase in face processing.