Refresh my memory: Episodic memory reinstatements intrude on working memory maintenance

A fundamental question in memory research is how different forms of memory interact. Previous research has shown that people rely on working memory (WM) in short-term recognition tasks; a common view is that episodic memory (EM) only influences performance on these tasks when WM maintenance is disrupted. However, retrieval of memories from EM has been widely observed during brief periods of quiescence, raising the possibility that EM retrievals during maintenance-critically, before a response can be prepared-might affect short-term recognition memory performance even in the absence of distraction. We hypothesized that this influence would be mediated by the lingering presence of reactivated EM content in WM. We obtained support for this hypothesis in three experiments, showing that delay-period EM reactivation introduces incidentally-associated information ( context ) into WM, and that these retrieved associations negatively impact subsequent recognition, leading to substitution errors (Experiment 1) and slowing of accurate responses (Experiment 2). fMRI pattern analysis showed that slowing is mediated by the content of EM reinstatement (Experiment 3). These results expose a previously hidden influence of EM on WM, raising new questions about the adaptive nature of their interaction

A Low Cost Tactor Suit for Vibrotactile Feedback

We constructed low cost tactors for vibrotactile feedback across the human arm for the purpose of providing a physical sensation surrogate for virtual objects. The tactors were built from readily available commercial parts, and provide low amplitude vibration for tactile feedback. The tactors are Velcro mounted on a custom suit designed to ensure localized sensations of each tactor. The suit is designed to be compatible with standard motion capture devices. Our suit provides 24 vibratory tactors in a tactor array on the user’s right arm and hand, and can easily be expanded to include the entire torso and body

Enhanced Collision Perception Using Tactile Feedback

We used a custom designed tactor suit to provide full body vibrotactile feedback across the human arm for the purpose of enabling users to perceive a physical sense of collisions in a virtual world. We constructed a 3-D virtual environment to test arm reach movements. We present the results of human subject trials that test the benefit of using vibrotactile feedback for this purpose. Our preliminary results presented here show a small, but distinct, advantage with the use of tactors. With additional refinements to the system, improved performance results can be obtained

Collision Awareness Using Vibrotactile Arrays

What is often missing from many virtual worlds is a physical sense of the confinement and constraint of the virtual environment. To address this issue, we present a method for providing localized cutaneous vibratory feedback to the user’s right arm. We created a sleeve of tactors linked to a real-time human model that activates when the corresponding body area collides with an object. The hypothesis is that vibrotactile feedback to body areas provides the wearer sufficient guidance to acertain the existence and physical realism of access paths and body configurations. The results of human subject experiments clearly show that the use of full arm vibrotactile feedback improves performance over purely visual feedback in navigating the virtual environment. These results validate the empirical performance of this concept

Virtual Training via Vibrotactile Arrays

What is often missing from many virtual worlds and training simulations is a physical sense of the confinement and constraint of the virtual environment. We present a method for providing localized cutaneous vibratory feedback to the user’s right arm. We created a sleeve of tactors linked to a real-time human model; the tactors activate to apply sensation to the corresponding body area. The hypothesis is that vibrotactile feedback to body areas provides the wearer sufficient guidance to assume correct body configurations and ascertain the existence and physical realism of access paths. We present the results of human subject experiments that study both explicit and implicit training of skills using vibrotactile arrays. Implicitly, collision awareness is achieved by activating the appropriate tactor when a body part collides with the scene; thus, the user will attempt to correct his or her body configuration. Explicitly, we use the tactors to guide the body into the proper configuration. The results of human subject experiments clearly show that the use of full arm vibrotactile feedback improves performance over purely visual feedback for navigating the virtual environment, as well as allowing easy acquisition of new skills. These results validate the empirical performance of this concept

Biological Implications of Hydroxyapatite Coatings on 3D Printed Titanium Implants

This study sought to determine the growth of and viability of osteoblast cells on hydroxyapatite coatings of 3D-printed titanium implants. The experiment used twenty 3D-printed titanium disks each of which had a determined surface roughness. These disks were printed by Tangible Solutions, LLC (Fairborn, OH) and then sonicated. Ten of the disks were coated with hydroxyapatite through the process of electrodeposition using an open cell and a three lead potentiostat. Using the hydroxyapatite coated titanium disks and uncoated disks, two four-day growth trials were performed. Two trials used five control disks (uncoated titanium disks) and five coated disks each, making an n of 10 for the total experiment. The disks were each placed into the wells of a culture plate and each disk was seeded with 15,000 human osteoblast cells. After four days in the incubator, the cells were removed using trypsin and the counted using the CytoSmart Automated Hemocytometer. The cell count from each disk as well as the viability of the cells from each disk were recorded. Means comparison was performed using Tukey-Kramer method of analysis. Results from the cell count portion of the experiment showed that the mean of the hydroxyapatite group was not significantly greater than the control group (p=0.83). In addition, cell viability of the hydroxyapatite group was also not significantly different than the control group (p=0.31). This data was unexpected but may be due to a change in the surface roughness between the two groups caused by the hydroxyapatite coating decreasing the surface roughness. The surface roughness selected for the experiment was chosen due to it being the most ideal for osteoblast growth, but any less rough surfaces were shown to be less ideal for osteoblast cell growth. Future Experiments will remove the variable of surface roughness

Prospectus, March 18, 2009

https://spark.parkland.edu/prospectus_2009/1008/thumbnail.jp

Molecular chains under tension: Thermal and mechanical activation of statistically interacting extension and contraction particles

This work introduces a methodology for the statistical mechanical analysis of polymeric chains under tension controlled by optical or magnetic tweezers at thermal equilibrium with an embedding fluid medium. The response of single bonds between monomers or of entire groups of monomers to tension is governed by the activation of statistically interacting particles representing quanta of extension or contraction. This method of analysis is capable of describing thermal unbending of the freely jointed or wormlike chain kind, linear or nonlinear contour elasticity, and structural transformations including effects of cooperativity. The versatility of this approach is demonstrated in an application to double-stranded DNA undergoing torsionally unconstrained stretching across three regimes of mechanical response including an overstretching transition. The three-regime force-extension characteristic, derived from a single free-energy expression, accurately matches empirical evidence