Olympic lightweight and open-class rowers possess distinctive physical and proportionality characteristics.

Rowers competing at the 2000 Olympic Games were measured for 38 anthropometric dimensions. The aim was to identify common physical characteristics that could provide a competitive advantage. The participants included 140 male open-class rowers, 69 female open-class rowers, 50 male lightweight rowers, and 14 female lightweight rowers. Body mass, stature, and sitting height were different (P < 0.01) between the open-class and lightweight rowers, as well as a comparison group of healthy young adults ("non-rowers", 42 males, 71 females), for both sexes. After scaling for stature, the open-class rowers remained proportionally heavier than the non-rowers, with greater proportional chest, waist, and thigh dimensions (P < 0.01). Rowers across all categories possessed a proportionally smaller hip girth than the non-rowers (P < 0.01), which suggested the equipment places some constraints on this dimension. Top-ranked male open-class rowers were significantly taller and heavier and had a greater sitting height (P < 0.01) than their lower-ranked counterparts. They were also more muscular in the upper body, as indicated by a larger relaxed arm girth and forearm girth (P < 0.01). For the male lightweight rowers, only proportional thigh length was greater in the best competitors (P < 0.01). In the female open-class rowers, skinfold thicknesses were lower in the more highly placed competitors (P < 0.01). In conclusion, the rowers in this sample demonstrated distinctive physical characteristics that distinguish them from non-rowers and other sports performers.

Lightness from contrast: a selective integration model.

As has been observed by Wallach (1948), perceived lightness is proportional to the ratio between the luminances of adjacent regions in simple disk-annulus or bipartite scenes. This psychophysical finding resonates with neurophysiological evidence that retinal mechanisms of receptor adaptation and lateral inhibition transform the incoming illuminance array into local measures of luminance contrast. In many scenic configurations, however, the perceived lightness of a region is not proportional to its ratio with immediately adjacent regions. In a particularly striking example of this phenomenon, called White's illusion, the relationship between the perceived lightnesses of two gray regions is the opposite of what is predicted by local edge ratios or contrasts. This paper offers a new treatment of how local measures of luminance contrast can be selectively integrated to simulate lightness percepts in a wide range of image configurations. Our approach builds on a tradition of edge integration models (Horn, 1974; Land & McCann, 1971) and contrast/filling-in models (Cohen & Grossberg, 1984; Gerrits & Vendrik 1970; Grossberg & Mingolla, 1985a, 1985b). Our selective integration model (SIM) extends the explanatory power of previous models, allowing simulation of a number of phenomena, including White's effect, the Benary Cross, and shading and transparency effects reported by Adelson (1993), as well as aspects of motion, depth, haploscopic, and Gelb induced contrast effects. We also include an independently derived variant of a recent depthful version of White's illusion, showing that our model can inspire new stimuli.

Visual cortical mechanisms of perceptual grouping: interacting layers, networks, columns, and maps.

The visual cortex has a laminar organization whose circuits form functional columns in cortical maps. How this laminar architecture supports visual percepts is not well understood. A neural model proposes how the laminar circuits of V1 and V2 generate perceptual groupings that maintain sensitivity to the contrasts and spatial organization of scenic cues. The model can decisively choose which groupings cohere and survive, even while balanced excitatory and inhibitory interactions preserve contrast-sensitive measures of local boundary likelihood or strength. In the model, excitatory inputs from lateral geniculate nucleus (LGN) activate layers 4 and 6 of V1. Layer 6 activates an on-center off-surround network of inputs to layer 4. Together these layer 4 inputs preserve analog sensitivity to LGN input contrasts. Layer 4 cells excite pyramidal cells in layer 2/3, which activate monosynaptic long-range horizontal excitatory connections between layer 2/3 pyramidal cells, and short-range disynaptic inhibitory connections mediated by smooth stellate cells. These interactions support inward perceptual grouping between two or more boundary inducers, but not outward grouping from a single inducer. These boundary signals feed back to layer 4 via the layer 6-to-4 on-center off-surround network. This folded feedback joins cells in different layers into functional columns while selecting winning groupings. Layer 6 in V1 also sends top-down signals to LGN using an on-center off-surround network, which suppresses LGN cells that do not receive feedback, while selecting, enhancing, and synchronizing activity of those that do. The model is used to simulate psychophysical and neurophysiological data about perceptual grouping, including various Gestalt grouping laws.

Visual brain and visual perception: how does the cortex do perceptual grouping?

How the brain generates visual percepts is a central problem in neuroscience. We propose a detailed neural model of how lateral geniculate nuclei and the interblob cortical stream through V1 and V2 generate context-sensitive perceptual groupings from visual inputs. The model suggests a functional role for cortical layers, columns, maps and networks, and proposes homologous circuits for V1 and V2 with larger-scale processing in V2. An integrated treatment of interlaminar, horizontal, orientational and endstopping cortical interactions and a role for corticogeniculate feedback in grouping are proposed. Modeled circuits simulate parametric psychophysical data about boundary grouping and illusory contour formation.

ART-EMAP: A neural network architecture for object recognition by evidence accumulation.

A new neural network architecture is introduced for the recognition of pattern classes after supervised and unsupervised learning. Applications include spatio-temporal image understanding and prediction and 3D object recognition from a series of ambiguous 2D views. The architecture, called ART-EMAP, achieves a synthesis of adaptive resonance theory (ART) and spatial and temporal evidence integration for dynamic predictive mapping (EMAP). ART-EMAP extends the capabilities of fuzzy ARTMAP in four incremental stages. Stage 1 introduces distributed pattern representation at a view category field. Stage 2 adds a decision criterion to the mapping between view and object categories, delaying identification of ambiguous objects when faced with a low confidence prediction. Stage 3 augments the system with a field where evidence accumulates in medium-term memory. Stage 4 adds an unsupervised learning process to fine-tune performance after the limited initial period of supervised network training. Each ART-EMAP stage is illustrated with a benchmark simulation example, using both noisy and noise-free data.

A neural theory of attentive visual search: interactions of boundary, surface, spatial, and object representations.

Visual search data are given a unified quantitative explanation by a model of how spatial maps in the parietal cortex and object recognition categories in the inferotemporal cortex deploy attentional resources as they reciprocally interact with visual representations in the prestriate cortex. The model visual representations are organized into multiple boundary and surface representations. Visual search in the model is initiated by organizing multiple items that lie within a given boundary or surface representation into a candidate search grouping. These items are compared with object recognition categories to test for matches or mismatches. Mismatches can trigger deeper searches and recursive selection of new groupings until a target object is identified. The model provides an alternative to Feature Integration and Guided Search models.

Relationship between physique and rectal temperature cooling rate.

Despite many attempts to relate components of physique to core temperature cooling rate, no consistent relationship has emerged. The inconsistencies among the reported findings may arise from unaccounted thermoregulatory responses or incomplete physique assessment or both. A study was designed to examine this relationship in the range of rectal temperatures (Tre) within which shivering and sweating are absent, defined as the null zone, thus minimizing the contribution of these effector responses. Twenty healthy subjects (10 male and 10 female), representing a variety of physiques, participated in the study. The anthropometric protocol included 5 heights, body mass, 8 skinfolds, 10 girths, and 4 breadths. This permitted derivation of a body surface-area-to-mass ratio and estimates of adipose and muscle tissue masses using a cadaver-validated mass fractionation model. Subjects were heated in a 40 degrees C bath followed immediately by cooling in a 30.6 degrees C bath. During the cooling, forehead sweating rate and oxygen uptake were monitored to establish the boundaries of the Tre null zone. In addition, on-line recordings were made of Tre, skin temperature, and surface heat flux at six sites. The rate of cooling of Tre (Tre), in the range of temperatures between thresholds for sweating and shivering, was correlated to the components of physique. Estimates of adipose and skeletal muscle tissue masses did not correlate to Tre in the range of core temperatures investigated. However, total mass exhibited a significant correlation (r = 0.5, P less than or equal to 0.05) with Tre, but gender seemed to distort this relationship, possibly due to differences in adipose tissue distribution.

Effects of skin thickness and skinfold compressibility on skinfold thickness measurement.

Variability in both skin thickness and skinfold compressibility affects the relationship between the skinfold caliper reading at a particular site on the body and the actual adipose thickness at that site, thus inducing error in the estimation of body fatness. To investigate this variability, skinfold thickness by caliper and incised depth of subcutaneous adipose tissue were measured at 13 skinfold sites in 6 male and 7 female unembalmed cadavers aged 55 to 94 years. All skin was then removed and its thickness measured at the exact sites of skinfold measurement. The regional patterns for skin thickness were similar in men and women, though women had significantly (P < .05) thinner skin than men at the biceps, chest, supraspinale, and abdominal sites. Mean (SD) skin thickness for each cadaver over all sites ranged from 0.76 mm (0.28 mm) to 1.47 mm (0.43 mm), with an overall mean for men of 1.22 mm (0.36 mm) and for women of 0.98 mm (0.36 mm). The thickness of a double layer of skin expressed as a percentage of skinfold thickness for all cadavers over all 13 sites ranged from 7.1% to 33.4%. Because of their leanness and thicker skin, the mean for men, 22.7% (10.1%), was significantly greater than that for women, 10.8% (6.2%) (P < .0001). Mean skinfold compressibility over all sites was 53.5% (16.4%) in men adn 51.9% (16.5%) in women (not significant). Such marked variability in skinfold compressibility and in the relative contribution of skin thickness to skinfold thickness suggests the need for caution in comparing estimates of fatness by skinfold caliper between different subjects. © 1992 Wiley-Liss, Inc.

Physique characteristics of Pan American Games lightweight rowers.

The emergence of lightweight rowing as an international sport has made the optimization of physique within the weight restrictions a matter of primary importance in selection and training of the participants. The occasion of the Xth Pan American Games provided opportunity to obtain comprehensive anthropometric data on 20 male and 13 female lightweight rower finalists including most of the medal winners. Anthropometric characteristics, somatotype, and proportionality profiles showed the male rowers to be similar in most aspects to a student control sample, with the exception of short sitting height and large transverse chest breadth. The females, on the other hand, appeared to be very different from the control sample, having a number of characteristics similar to those of Olympic rowers. The female lightweight rowers also uniquely demonstrated two distinct physique prototypes.

Relationship of the body mass index with skinfolds, girths, and bone breadths in Canadian men and women aged 20-70 years.

The relationship of Quetelet index (w/h2), or body mass index (BMI), with the sum of skinfolds at five sites, two skinfold-corrected limb girths, and two bone breadths were studied in a cross-sectional sample of 12,282 men and 6,593 women aged 20-70 years. The correlations of the BMI with skinfolds (0.50), bone breadths (0.51), and girths (0.58) were too low for individual prediction. Contingency tables of the BMI and sum of skinfold categories further indict its use for the purpose of assessing adiposity status or monitoring change in individuals.

The design of a parallax-correcting anthropometer for replication in nonspecialized machine shops.

A fixed-rod, slider with a window, a double-scribed line for viewing a measuring tape affixed to the rod, and a sturdy footpiece are design features of an anthropometer for measuring projected lengths. The new instrument is designed to replace contemporary models which may be inaccessible to investigators with limited budgets or currency restrictions. None of the design features are beyond the ingenuity of local machinists to modify, find alternate materials, and use different machine procedures. The same principles of construction can be applied in making sliding calipers with straight and recurved branches. While there is some loss in portability of the fixed-length anthropometer, the improved stability and superior visual scale more than compensate for the disadvantages and make the new anthropometer a candidate for the instrument of choice in obtaining projected length measurements.

Prediction of body fat by skinfold caliper: assumptions and cadaver evidence.

A series of assumptions required for use of skinfold calipers for the estimation of human body composition is examined in terms of direct evidence from the measurement and dissection of 6 male and 7 female cadavers. Skinfold compressibility showed significant inter-subject and inter-site differences with the highest values (64.7 percent and 63.8 percent) at the spinale and biceps sites and the lowest (33.6 percent and 34.4 percent) at the front thigh and medial calf. Skin thickness as a percentage of skinfold thickness was highest at the subscapular site (28.1 percent). Adipose tissue patterning showed great variability, indicating the importance of using skinfold caliper readings from a variety of different sites including upper limb, lower limb and trunk. Further sources of error include variability in fat content of adipose tissue (estimated at 20 percent in our sample) and in the internal and subcutaneous fat deposition. Recommendations for the use of skinfold calipers to assess adiposity and monitor change are made in the light of these findings.

Specificity of psychiatric manifestations in relation to neurotoxic chemicals.

Previous impressions of specificity of psychiatric manifestations in relation to particular chemical intoxications have been confirmed by comparisons of the symptoms and signs of two groups of individuals. Nine persons exposed to inorganic mercury had "erethism" and xenophobia in addition to non-specific features of central nervous system poisoning. Twelve men with heavy exposure to organotins, in contrast to ten men with light or no exposure, more frequently presented an unique alternation between outbursts of range and deep depression, the later lasting from a few hours to a few days. The more heavily exposed men also had a greater number of nonspecific symptoms from neurotoxins.

Neurotoxic effects of occupational exposure to organotins.

The authors gave 22 chemical workers neurological, psychiatric, and neuropsychological examinations and placed them in one of two groups according to their degree of exposure to trimethyltin chloride spillage during January 1978. Other chemicals to which they had been exposed were dimethyltin dichloride and methyl chloride. Specific and nonspecific symptoms of intoxication of the CNS showed a significantly greater frequency in the highly exposed group, including cycles of depression and destructive rage, each lasting a few hours. These observations should alert diagnosticians to this type of occupational exposure.