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Breaking the barriers to manufacture thermoplastic microfluidics!

December 31, 2017 By

themoplastic microfluidics figure

Thermoplastics, such as Cyclin Olefin Copolymer, are used in commercial applications of microfluidics because they are biocompatible, have good material properties such as optical clarity, low fluorescence, high toughness and are cheap to mass produce. However, there are challenges for academic labs to make thermoplastic microfluidics devices. Fabricating molds for thermoplastics is expensive and other process steps, such as sealing the chip and interfacing the chip to the lab are difficult. In a recent publication, the Fraden lab described an inexpensive method for rapid prototyping of thermoplastic microfluidics suitable for academic labs for applications such as x-ray diffraction of protein crystals produced on the same chip in which they were crystallized, or for labs seeking to manufacture a thermoplastic prototype of a microfluidic device in order to demonstrate the potential for mass production. This process will facilitate the transfer of University developed microfluidics to commercialization.

Rapid prototyping of cyclic olefin copolymer (COC) microfluidic devices. S. Ali Aghvami, Achini Opathalage, Z.K. Zhang, Markus Ludwig, Michael Heymann, Michael Norton, Niya Wilkins, Seth Fraden. Sensors and Actuators B: Chemical. Volume 247, August 2017, Pages 940-949.

 

Filed Under: labs, Physics Tagged With: , , , , ,

Cross-Cultural Differences in Brain Activity of Specific and General Recognition

December 30, 2017 By
Results from paper

Results revealed regions in the left fusiform (left circle) and left hippocampus (right circle) emerged when comparing activity for correct same versus correct similar responses across cultures.

A recent publication from Paige, Ksander, Johndro, & Gutchess (Cortex, 2017) of the Aging, Culture, and Cognition Lab at Brandeis University has shed light on how culture affects brain activation when encoding information into memory. Prior work has suggested that culture influences how people perceive the world, including how much perceptual detail (e.g., size, shape, color, etc.) is remembered. It may not be surprising that culture shapes customs or even social interactions, but evidence also suggests that it shapes cognition. Because encoding details into memory necessitates the engagement of additional cognitive resources, comparing across cultures on the specificity of memory offers a glimpse into which processes and types of information are considered important across cultural groups.

Participants who originated from America or East Asia studied photos of everyday items in a magnetic resonance imaging (MRI) scanner and 48 hours later completed a surprise recognition test. The test consisted of same (i.e., previously seen in the scanner), similar (i.e., same name, different features; for example, a coffee mug that is a different shape or color than what the participant saw at encoding), or new photos (i.e., items not previously seen in the scanner) and participants were instructed to respond “same,” “similar,” or “new.”

Unlike other studies, culture did not disproportionately influence behavioral memory performance for specific information. However, East Asians showed greater activation in the left fusiform and left hippocampus relative to Americans for specific (items correctly recognized as same) versus general memory (items correctly recognized as similar). Additional follow-up analyses confirmed this cultural pattern was not driven by differential familiarity with the items across cultures. One possible explanation for this finding is cultural differences in prioritization of high (e.g., fine details, local information) versus low spatial information (e.g., coarser, global information). In the present study, increased activation in the left medial temporal regions for East Asians may be reflective of additional processes needed to encode specific details into memory, reflecting the greater demands of local, high spatial frequency processing. Current work in the lab is addressing this possibility.

Past work has failed to consider how cross-cultural differences can occur at both the behavioral and neural level. The present findings remedy that, suggesting that culture should be considered an individual difference that influences memory specificity and its underlying neural processes.

Paige, L. E., Ksander, J. C., Johndro, H. A., & Gutchess, A. H. (2017). Cross-cultural differences in the neural correlates of specific and general recognition. Cortex, 91, 250-261.

 

Filed Under: labs, Psychology Tagged With: , , , , ,

The Amygdala, Fraud and Older Adults

December 21, 2017 By

Figure from Zebrowitz-Gutchess paper

Figure 1. Peak amygdala activation as a function of face trustworthiness for older adult participants. Error bars represent standard errors. COPE is the contrast of parameter estimates [high or medium, or low trustworthy faces minus baseline fixation] from which peak values were extracted at the subject-level using FSL featquery. * p < .05.

There is a widespread belief that older adults are more vulnerable to consumer fraud than younger adults. Behavioral evidence supporting this belief is mixed, although there is a reliable tendency for older adults to view faces as more trustworthy than do younger adults.  One study provided supporting neural evidence by demonstrating that older adults failed to show greater amygdala activation to low than high trustworthy faces, in contrast to considerable evidence that younger adults do show this effect. This result is consistent with the argument for greater vulnerability to fraud in older adults, since the amygdala responds to threatening stimuli. More generally, however, the amygdala responds to biologically salient stimuli, and many previous studies of younger adults have shown that this includes not only threatening, low trustworthy faces, but also high trustworthy faces. The Zebrowitz Face Perception Lab therefore included medium trustworthy faces in order to detect separate effects of high trustworthiness and low trustworthiness on amygdala activation in older adults, something that the one previous study of older adults did not do. Consistent with that study we found that older adults did not show stronger amygdala activation to low than high trustworthy faces.  However, they did show stronger amygdala activation to high than to medium trustworthy faces, with a similar trend for low vs medium, although that difference was not strong enough to be confident that it would replicate (See Figure 1).

The fact that older adults did not show greater amygdala activation to low than medium or high trustworthy faces is consistent with the suggestion that older adults may be more vulnerable to fraud. However, an important question is whether vigilant responding to untrustworthy-looking faces could actually protect one from fraud.  Arguing against this possibility is the finding that although younger adults have consistently shown greater amygdala activation to people who look untrustworthy, they do not show greater activation to those who actually cheat.  On the other hand, some evidence indicates that facial appearance does provide valid cues to threat. Face shape not only influenced younger adults’ trust of potential exploiters, but it also proved to be a valid indicator of economic exploitation.  Furthermore, this face shape cue influenced both younger and older adults’ accurate impressions of aggressiveness. To shed further light on neural mechanisms for any age differences in vulnerability to fraud that may exist requires investigating: 1) the sensitivity of neural responses to actual differences in trustworthiness in the domain of economic exploitation, and 2) whether any age differences in those neural responses are related to differential vulnerability to economic exploitation.

Zebrowitz, L.A., Ward, N., Boshyan, J., Gutchess, A., & Hadjikhani, N. (2017).  Older adults’ neural activation in the reward circuit is sensitive to face trustworthiness.  Cognitve, Affective, and Behavioral Neuroscience.

 

 

Filed Under: labs, Neuroscience, Psychology Tagged With: , , , , ,

Communicating Memory Information Between the Hippocampus and Prefrontal Cortex

December 20, 2017 By

Jadhav paper full image

The brain has a remarkable capacity to record our daily experiences and recall this stored information to guide our behavior. For example, every time you decide to get a cup of coffee on campus, you immediately know where to go and then step toward your destination. The ability to successfully memorize paths and navigate in the environment is fundamental for animals searching for food (see Illustration), as well as for humans surviving in a complicated environment, especially when you don’t have your smartphone to rely on, but only your brain as the inner GPS! However, how does the brain learn and remember such plans that allow us to get from one place to another?

We know that a structure in brain called the hippocampus plays an important role in encoding and storing memories. The hippocampus is thought to replay remembered experiences during fast, ripple-like brain waves, termed sharp-wave ripples (SWRs), that occur during “down-time” for the brain, i.e., offline periods during sleep and during pauses in active behavior. It has been previously shown by Jadhav and colleagues that selectively disrupting these ripple oscillations using precisely-timed electrical impulses impairs the ability of animals to learn in spatial mazes, suggesting that this “mental replay” is important for navigation and memory (Jadhav et al., 2012, Science). Notably, mental replay is not isolated activity in the hippocampus, but works together with the prefrontal cortex (PFC), the executive center of brain involved in storing memories and making decisions (Jadhav et al., 2016, Neuron). However, exactly how such memory replay supports memory processing in waking and sleep states had remained elusive.

In a new article published in the Journal of Neuroscience (Tang et al., 2017), the Jadhav lab (the team included Neuroscience graduate students Wenbo Tang and Justin Shin) used high-density electrophysiology to record large numbers of neurons in both the hippocampus and prefrontal cortex in both sleep and awake states. They discovered that as rats learned a spatial memory task, the activity in the hippocampal-prefrontal network replayed recent experiences in a precise manner during SWRs that occurred when animals paused from actively exploring the maze. This structured mental replay related to ongoing spatial behavior is ideally suited for storing and retrieving memories to inform decisions. When animals were asleep after exploring the maze, the hippocampal-prefrontal replay, however, appeared “noisy” and mixed. This replay occurring during sleep periods can support the ability of the brain to consolidate memories, by selectively integrating related memories to build a coherent map for long-term storage (see Illustration). These findings show how memory information is communicated between the hippocampus and PFC during ripple oscillations, and indicate that mental replay during sleep and awake states serve distinct roles in memory. These studies collectively provide fundamental knowledge about the neural substrates of memories. They will thus provide important insights into memory deficits that are prevalent in many neurological disorders that involve the hippocampal-prefrontal network, such as Alzheimer’s disease and schizophrenia.

Hippocampal-Prefrontal Reactivation during Learning Is Stronger in Awake Compared with Sleep States. Wenbo Tang, Justin D. Shin, Loren M. Frank and Shantanu P. Jadhav. Journal of Neuroscience 6 December 2017, 37 (49) 11789-11805.

 

Filed Under: labs, Neuroscience, Psychology Tagged With: , , , , , ,

DIY your own Programmable Illumination Microscope

January 22, 2016 By

The Fraden Group describes how to build your own Programmable Illumination Microscope in the American Journal of Physics

Have you ever marveled at the equipment used in a research lab? Have you ever wondered how a specialized piece of equipment was made? Have you ever wondered how much it would cost to build your own research microscope? Have you ever considered trying to make your own research microscope? The details on how the Fraden Group builds their Programmable Illumination Microscope for under $4000 was recently published in the American Journal of Physics.

apparatus300

The Programmable Illumination Microscope or PIM is a highly specialized microscope where the illumination for the sample being imaged comes from a modified commercial projector, nearly identical to the ones mounted in every classroom. For the PIM the lens that projects the image onto the screen is removed and replaced with optics (often the same lens in reverse) that shrinks the image down so that it can be focused through the microscope objective onto the sample. The light coming from the projector, which is the illumination source for the microscope, can be modified in realtime based on the image being captured by the camera. Thus the illumination is not only programmable but can also be algorithmic and provide active feedback.

This new publication in the American Journal of Physics, which is published by the American Association of Physics Teachers, is intended to help small teaching and research labs across the country develop their own PIMs to be built and used by undergraduate students. The paper includes schematics and parts lists for the hardware as well as instructions and demonstration code for the software. Any other questions can be directed to the authors Nate Tompkins and Seth Fraden.

Filed Under: Physics, teaching Tagged With: , , ,

Mitosis: One Polo controls it all

November 17, 2014 By

On November 6, 2014, Cell Cycle published a paper from the Yoshida lab entitled “The budding yeast Polo-like kinase Cdc5 is released from the nucleus in anaphase for timely mitotic exit.” This study was authored by Vladimir V. Botchkarev Jr., Valentina Rossio, and Satoshi Yoshida.

The cell cycle is one of the most fundamental biological processes whose ultimate goal is cell division with equal content of DNA in both daughter cells. The process of cell division is regulated by many intracellular events which must occur in a sequential order. These events include mitotic entry, faithful chromosome segregation, mitotic exit, and cytokinesis. Over the past 25 years, the Polo-like kinase (Polo) has been established to play important regulatory roles in each of these processes. Although many mitotic substrates of Polo have been discovered, the mechanism by which Polo can coordinate all of these mitotic events has remained largely elusive.

To understand the mechanism by which Polo can target its many substrates in a sequential order during mitosis, we decided to study the budding yeast Polo kinase Cdc5, which has high conservation with the human Polo-like kinase 1.

We found that Cdc5-GFP dynamically changes its localization during the cell cycle: Cdc5 is found in the cytoplasm in S- through early G2-phase, it accumulates in the nucleus at metaphase, and is released again to the cytoplasm in anaphase. Blocking nuclear import of Cdc5 in metaphase leads to a prolonged metaphase duration, suggesting that nuclear Cdc5 is required for chromosome segregation. In contrast, blocking nuclear release of Cdc5 in anaphase results in a prolonged anaphase duration, a defect in activation of the cytoplasmic Mitotic Exit Network, and a defect in cytokinesis. This indicates that Cdc5 is released from the nucleus to the cytoplasm in anaphase for timely mitotic exit and cytokinesis. We further found that activation of the Cdc14 phosphatase, a known nuclear substrate of Cdc5, is required for Cdc5 nuclear release in anaphase.

Collectively, our work reveals that the budding yeast Polo-like kinase Cdc5 controls the timing of mitotic events by dynamically changing its sub-cellular localization. Furthermore, our data suggests the existence of a positive feedback look between Cdc5 and Cdc14 to regulate timely mitotic exit. Read more …

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