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Small Objects (small + object)
Selected AbstractsDifferential cortical activity for precision and whole-hand visually guided grasping in humansEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 4 2007Chiara Begliomini Abstract Effective grasping involves the remarkable ability to implement multiple grasp configurations such as precision grip (PG; opposition between the index finger and thumb) and whole-hand grasp (WHG), depending on the properties of the object grasped (e.g. size, shape and weight). In the monkey brain, different groups of cells in the anterior,lateral bank of the intraparietal sulcus (area AIP) are differentially active for various hand configurations during grasping of differently shaped objects. Visually guided grasping studies in humans suggest the anterior intraparietal sulcus (aIPS) as the homologue of macaque area AIP, but leave unresolved the question of whether activity in human aIPS reflects the relationship between object size and grasp configuration, as in macaques. To address this issue, a human fMRI study was conducted in which objects were grasped with the right hand while object size was varied. The results indicated that the left aIPS was active when the subjects naturally adopted a PG to grasp the small object but showed a much weaker response when subjects naturally adopted a WHG to grasp the large object. The primary motor cortex and somatosensory cortices were active for both PG and WHG. Our results suggest that, in humans, the aIPS is centrally involved in determining the type of grasp. [source] Level of purposeful hand function as a marker of clinical severity in Rett syndromeDEVELOPMENTAL MEDICINE & CHILD NEUROLOGY, Issue 9 2010JENNY DOWNS Aim, We investigated relationships between hand function and genotype and aspects of phenotype in Rett syndrome. Method, Video assessment in naturalistic settings was supplemented by parent-reported data in a cross-sectional study of 144 females with a mean age of 14 years 10 months (SD 7y 10mo; range 2y,31y 10mo), 110 of whom had a mutation of the methyl CpG binding protein 2 (MECP2) gene. Ordinal logistic regression was used to assess relationships between hand function and MECP2 mutation, age, a modified Kerr score, Functional Independence Measure for Children (WeeFIM), ambulation level, and frequency of hand stereotypies. Results, Approximately two-thirds of participants demonstrated purposeful hand function, ranging from simple grasping skills to picking up and manipulating small objects. In participants with a confirmed MECP2 mutation, those with the p.R168X mutation had the poorest hand function on multivariate analysis with C-terminal deletion as the baseline (odds ratio [OR] 0.19; 95% confidence interval [CI] 0.04,0.95), whereas those with the p.R133C or p.R294X mutation had better hand function. Participants aged 19 years or older had lower hand function than those aged less than 8 years (OR 0.36; 95% CI 0.14,0.92). Factors that were associated with better hand function were lower Kerr scores for a 1-point increase in score (OR 0.77; 95% CI 0.69,0.86), higher WeeFIM scores for a 1-point increase in score (OR 1.08; 95% CI 1.04,1.12), and greater ambulation than those completely dependent on carers for mobility (OR 22.64; 95% CI 7.02,73.08). The results for participants with a confirmed pathogenic mutation were similar to results obtained when participants without a mutation were also included. Interpretation, Our novel assessment of hand function in Rett syndrome correlated well with known profiles of common MECP2 mutations and overall clinical severity. This promising assessment could measure clinical responses to therapy. [source] Effects of Aging on Hand FunctionJOURNAL OF AMERICAN GERIATRICS SOCIETY, Issue 11 2001Vinoth K. Ranganathan MSE OBJECTIVES: The purpose of this study was to quantify age-induced changes in handgrip and finger-pinch strength, ability to maintain a steady submaximal finger pinch force and pinch posture, speed in relocating small objects with finger grip, and ability to discriminate two identical mechanical stimuli applied to the finger tip. DESIGN: A cross-sectional study. SETTINGS: Greater Cleveland area of Ohio. PARTICIPANTS: Healthy, independent, young (n = 27, range 20,35 years) and older (n = 28, range 65,79 years) subjects. MEASUREMENTS: Handgrip strength, maximum pinch force (MPF), ability to maintain a steady pinch force at three relative force levels (5%, 10%, and 20% MPF) and three absolute force levels (2.5 Newtons (N), 4 N, and 8 N), ability to maintain a precision pinch posture, speed in relocating pegs from a nearby location onto the pegboard, and the shortest distance for discriminating two stimuli were measured in both young and older groups. RESULTS: Compared with young subjects, the older group's handgrip force was 30% weaker (P < .001), MPF was 26% lower (P < .05), and ability to maintain steady submaximal pinch force and a precision pinch posture was significantly less (P < .05). The time taken to relocate the pegs and the distance needed to discriminate two identical stimuli increased significantly with age (P < .01). The decrease in the ability to maintain steady submaximal pinch force was more pronounced in women than men. CONCLUSION: Aging has a degenerative effect on hand function, including declines in hand and finger strength and ability to control submaximal pinch force and maintain a steady precision pinch posture, manual speed, and hand sensation. [source] Sodium MRI using a density-adapted 3D radial acquisition techniqueMAGNETIC RESONANCE IN MEDICINE, Issue 6 2009Armin M. Nagel Abstract A density-adapted three-dimensional radial projection reconstruction pulse sequence is presented which provides a more efficient k -space sampling than conventional three-dimensional projection reconstruction sequences. The gradients of the density-adapted three-dimensional radial projection reconstruction pulse sequence are designed such that the averaged sampling density in each spherical shell of k -space is constant. Due to hardware restrictions, an inner sphere of k -space is sampled without density adaption. This approach benefits from both the straightforward handling of conventional three-dimensional projection reconstruction sequence trajectories and an enhanced signal-to-noise ratio (SNR) efficiency akin to the commonly used three-dimensional twisted projection imaging trajectories. Benefits for low SNR applications, when compared to conventional three-dimensional projection reconstruction sequences, are demonstrated with the example of sodium imaging. In simulations of the point-spread function, the SNR of small objects is increased by a factor 1.66 for the density-adapted three-dimensional radial projection reconstruction pulse sequence sequence. Using analytical and experimental phantoms, it is shown that the density-adapted three-dimensional radial projection reconstruction pulse sequence allows higher resolutions and is more robust in the presence of field inhomogeneities. High-quality in vivo images of the healthy human leg muscle and the healthy human brain are acquired. For equivalent scan times, the SNR is up to a factor of 1.8 higher and anatomic details are better resolved using density-adapted three-dimensional radial projection reconstruction pulse sequence. Magn Reson Med, 2009. © 2009 Wiley-Liss, Inc. [source] Dynamic in-hand movements in adult and young juvenile chimpanzees (Pan troglodytes)AMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY, Issue 3 2009Jessica Crast Abstract Descriptions of manual function in nonhuman primates have largely focused on static precision and power grasping (as first defined by Napier,1956), while identification and description of dynamic manual function are rare and incomplete. Here, we describe several forms of in-hand movements used by chimpanzees (Pan troglodytes) when manipulating small objects. In-hand movements are defined as the movement of an object within one hand via manipulation of the digits. We presented adult and young juvenile chimpanzees (ages 5,29 years) with a task that required inserting small objects through correspondingly shaped cutouts in a transparent Plexiglas panel. While attempting to insert the objects through the cutouts, the subjects used at least two forms of in-hand movements to change their grip on the object for more precise alignment. We describe in detail the in-hand movements they used and the variability observed in form and execution among the subjects. In general, the adult subjects used in-hand movements more frequently and used a wider variety of forms than did the young juvenile subjects, suggesting that in-hand movements are in the process of fine-tuning around the age of 5 years in chimpanzees. The dexterity exhibited by the adults, however, shows that the neuromuscular and morphological requirements for relatively complex digital manipulation are present in the adult chimpanzee. Am J Phys Antropol, 2009. © 2008 Wiley-Liss, Inc. [source] Direction selectivity in V1 of alert monkeys: evidence for parallel pathways for motion processingTHE JOURNAL OF PHYSIOLOGY, Issue 2 2007Moshe Gur In primary visual cortex (V1) of macaque monkeys, motion selective cells form three parallel pathways. Two sets of direction selective cells, one in layer 4B, and the other in layer 6, send parallel direct outputs to area MT in the dorsal cortical stream. We show that these two outputs carry different types of spatial information. Direction selective cells in layer 4B have smaller receptive fields than those in layer 6, and layer 4B cells are more selective for orientation. We present evidence for a third direction selective pathway that flows through V1 layers 4Cm (the middle tier of layer 4C) to layer 3. Cells in layer 3 are very selective for orientation, have the smallest receptive fields in V1, and send direct outputs to area V2. Layer 3 neurons are well suited to contribute to detection and recognition of small objects by the ventral cortical stream, as well as to sense subtle motions within objects, such as changes in facial expressions. [source] Infinite Recess: perspective and play in Magritte's La Condition HumaineART HISTORY, Issue 1 2002Eric Wargo The paintings of Rene Magritte, with their unsettling of common-sense relationships among objects, images and words, have been compared by many critics to the writings of Ludwig Wittgenstein. The 1933 painting La Condition Humaine, for instance, depicts a painting that exactly covers a ,real' landscape outside a window , thus raising questions about the ,location' of perception and thought. But Magritte's uncanny use of perspective, and his depictions of spaces that have ambiguous depth, suggest that an equally helpful interpretive framework to that of Wittgenstein may be that of psychoanalysis, particularly the object-relations theory of D.W. Winnicot and the latter's concept of ,transitional phenomena'. La Condition Humaine, for example, exemplifies how, by both negating and affirming the opacity of the picture plane, perspective transforms the painting into a transitional object that is both ,there' and ,not there' simultaneously. Many of the painter's works, his ,window' series in particular, suggest approaching Albertian perspective itself as a question of object-relating, the simultaneous search for autonomy and ontological security through play. An understanding of how Magritte's ambiguous spaces suggest both security as well as open-ended possibility can help to link his work not only with the traditions of Renaissance perspective and its modernist critics, but also with the aesthetic of the sublime and its iconography of colossal, indifferent nature. Sublimity may be interpreted psychoanalytically as nostalgia for the scale of childhood experience , for the world viewed as an enormous room in which small objects assume monumental physical and symbolic proportions. [source] | |||||||||||||