33 research outputs found
Zigzag Turning Preference of Freely Crawling Cells
The coordinated motion of a cell is fundamental to many important biological
processes such as development, wound healing, and phagocytosis. For eukaryotic
cells, such as amoebae or animal cells, the cell motility is based on crawling
and involves a complex set of internal biochemical events. A recent study
reported very interesting crawling behavior of single cell amoeba: in the
absence of an external cue, free amoebae move randomly with a noisy, yet,
discernible sequence of ‘run-and-turns’ analogous to the
‘run-and-tumbles’ of swimming bacteria. Interestingly, amoeboid
trajectories favor zigzag turns. In other words, the cells bias their crawling
by making a turn in the opposite direction to a previous turn. This property
enhances the long range directional persistence of the moving trajectories. This
study proposes that such a zigzag crawling behavior can be a general property of
any crawling cells by demonstrating that 1) microglia, which are the immune
cells of the brain, and 2) a simple rule-based model cell, which incorporates
the actual biochemistry and mechanics behind cell crawling, both exhibit similar
type of crawling behavior. Almost all legged animals walk by alternating their
feet. Similarly, all crawling cells appear to move forward by alternating the
direction of their movement, even though the regularity and degree of zigzag
preference vary from one type to the other
Priming Picture Naming with a Semantic Task: An fMRI Investigation
Prior semantic processing can enhance subsequent picture naming performance, yet the neurocognitive mechanisms underlying this effect and its longevity are unknown. This functional magnetic resonance imaging study examined whether different neurological mechanisms underlie short-term (within minutes) and long-term (within days) facilitation effects from a semantic task in healthy older adults. Both short- and long-term facilitated items were named significantly faster than unfacilitated items, with short-term items significantly faster than long-term items. Region of interest results identified decreased activity for long-term facilitated items compared to unfacilitated and short-term facilitated items in the mid-portion of the middle temporal gyrus, indicating lexical-semantic priming. Additionally, in the whole brain results, increased activity for short-term facilitated items was identified in regions previously linked to episodic memory and object recognition, including the right lingual gyrus (extending to the precuneus region) and the left inferior occipital gyrus (extending to the left fusiform region). These findings suggest that distinct neurocognitive mechanisms underlie short- and long-term facilitation of picture naming by a semantic task, with long-term effects driven by lexical-semantic priming and short-term effects by episodic memory and visual object recognition mechanisms