Musicians often say that they not only hear, but also “feel” music. To explore the contribution of tactile information in “feeling” musical rhythm, we investigated the degree that auditory and tactile inputs are integrated in humans performing a musical meter recognition task. Subjects discriminated between two types of sequences, ‘duple’ (march-like rhythms) and ‘triple’ (waltz-like rhythms) presented in three conditions: 1) Unimodal inputs (auditory or tactile alone), 2) Various combinations of bimodal inputs, where sequences were distributed between the auditory and tactile channels such that a single channel did not produce coherent meter percepts, and 3) Simultaneously presented bimodal inputs where the two channels contained congruent or incongruent meter cues. We first show that meter is perceived similarly well (70%–85%) when tactile or auditory cues are presented alone. We next show in the bimodal experiments that auditory and tactile cues are integrated to produce coherent meter percepts. Performance is high (70%–90%) when all of the metrically important notes are assigned to one channel and is reduced to 60% when half of these notes are assigned to one channel. When the important notes are presented simultaneously to both channels, congruent cues enhance meter recognition (90%). Performance drops dramatically when subjects were presented with incongruent auditory cues (10%), as opposed to incongruent tactile cues (60%), demonstrating that auditory input dominates meter perception. We believe that these results are the first demonstration of cross-modal sensory grouping between any two senses.
Human embryonic stem cell (hESC) cultures are heterogeneous and constituting paracrine signals are required to maintain pluripotency. The cellular interplay and dynamic nature of this heterogeneity is not understood. Here, long-term hESC imaging and tracking revealed that hESC heterogeneity is dynamic and hESC self-renewal is dependent on colony-proximal distributions of paracrine signals. Tracking of hESCs forming colonies revealed that a biologically distinct cell type arises at the colony periphery in the absence of feeders. Higher rates of cell death occur in these hESC-derived cells, leading to clonal selection of colony reestablishing cells. hESC-derived feeders co-transferred during passaging promoted rapid colony recovery and expansion and reduced overall clonal selection of self-renewing hESCs. Our findings demonstrate that hESCderived feeders arise from a distinct subpopulation of hESCs that respond to paracrine cues at the colony periphery that are required to sustain and establish clonal hESC self-renewal. ' 2010 International Society for Advancement of Cytometry Key termslive cell imaging; cell tracking; lineage analysis; human embryonic stem cells; human embryonic stem cell niche STEM cell developmental potential is maintained by self-renewal, which is thought to be partially controlled in vivo through extrinsic signals that regulate stem cell survival, self-renewal, and differentiation. Similarly, recent evidence has demonstrated that human embryonic stem cell (hESCs) both create and are reliant on a supportive in vitro niche (1,2). Similar to in vivo stem cell niches, the hESC in vitro niche consists of supportive differentiated cells, including hESC-derived fibroblast-like cells (hdFs), paracrine signals, and interactions with extracellular matrix (1-3). Recently, multiple niche-independent hESC cultures have demonstrated a variety of features suggestive of early transformation events, including growth factor independence, increased proliferation, and dramatically reduced differentiation potential (4). These results illustrate the importance of the in vitro niche, and that niche components are defining factors regulating hESC fate within the culture. However, the cellular dynamics involved in hESC niche regulation are not well understood.Differentiation of hESCs to hdFs is observed in all hESC culture formats, but it is more prevalent as the culture becomes more defined and feeder layer-free (i.e. moving from mouse embryonic feeder (MEF) layers, to conditioned media, to defined media) (5). Repeated passaging for expansion of hESC cultures causes disruption of the hESC microenvironment and requires the reestablishment of the cellular and noncellular niche (such as ECM produced by hESCs) (6). To establish a cellular niche in the absence of MEFs, hESCs generate hdFs (1,7). This reestablishment period, in which niche signals for survival are suboptimal, appears to invoke significant cell death, based on observed cell debris following passage and the established disparity between hESC
Musicians often say that they not only hear, but also “feel” music. To explore the contribution of tactile information in “feeling” musical rhythm, we investigated the degree that auditory and tactile inputs are integrated in humans performing a musical meter recognition task. Subjects discriminated between two types of sequences, ‘duple’ (march-like rhythms) and ‘triple’ (waltz-like rhythms) presented in three conditions: 1) Unimodal inputs (auditory or tactile alone), 2) Various combinations of bimodal inputs, where sequences were distributed between the auditory and tactile channels such that a single channel did not produce coherent meter percepts, and 3) Simultaneously presented bimodal inputs where the two channels contained congruent or incongruent meter cues. We first show that meter is perceived similarly well (70%–85%) when tactile or auditory cues are presented alone. We next show in the bimodal experiments that auditory and tactile cues are integrated to produce coherent meter percepts. Performance is high (70%–90%) when all of the metrically important notes are assigned to one channel and is reduced to 60% when half of these notes are assigned to one channel. When the important notes are presented simultaneously to both channels, congruent cues enhance meter recognition (90%). Performance drops dramatically when subjects were presented with incongruent auditory cues (10%), as opposed to incongruent tactile cues (60%), demonstrating that auditory input dominates meter perception. We believe that these results are the first demonstration of cross-modal sensory grouping between any two senses.
Precise information about the size, shape, temporal dynamics, and spatial distribution of cells is beneficial for the understanding of cell behavior and may play a key role in drug development, regenerative medicine, and disease research. The traditional method of manual observation and measurement of cells from microscopic images is tedious, expensive, and time consuming. Thus, automated methods are in high demand, especially given the increasing quantity of cell data being collected. In this article, an automated method to measure cell morphology from microscopic images is proposed to outline the boundaries of individual hematopoietic stem cells (HSCs). The proposed method outlines the cell regions using a constrained watershed method which is derived as an inverse problem. The experimental results generated by applying the proposed method to different HSC image sequences showed robust performance to detect and segment individual and dividing cells. The performance of the proposed method for individual cell segmentation for single frame high-resolution images was more than 97%, and decreased slightly to 90% for low-resolution multiframe stitched images. ' 2010 International Society for Advancement of Cytometry Key terms microscopic image sequence; hematopoietic stem cell; cell uropodia; automated cell shape analysis; watershed segmentation; inverse problem; biomedical image analysis ADVANCED techniques in digital image processing and pattern recognition can potentially be applied to a large number of digital cytometry systems to improve our understanding of cellular and intercellular events and to direct new discoveries in biological and medical research.Hematopoietic stem cells (HSCs) form blood and immune cells and are responsible for the constant renewal of blood. To produce new blood cells, HSCs proliferate and differentiate to different blood cell types (1). To analyze stem-cell behavior and infer cell features, the localization, segmentation, and tracking of HSCs in culture is crucial. In our previous work we addressed cell detection/localization (2,3) and the association of detected cells (4). Yet to infer the cell features, we need to outline the boundaries of individual, touching, and dividing cells.Previously, in vitro time-lapse video microscopy has been used to identify phenotypic traits associated with in vivo HSC functionality. Specifically, longer cellcycle times were correlated with the retention of HSC activity, and the presence of lagging posterior projections (uropodia) was correlated with the loss of HSC activity (5).Various time-lapse studies were conducted on HSCs to provide information on their morphology, migration, and localization. For example, individual immature hematopoietic cells were examined to determine the differences in migration mechanisms caused by the primitive nature of the cells (6). This helped to explain the loss of phenotypic function during stem cell differentiation. Also a time-lapse video
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