Fascinating research out of Harvard shows that the retina of the eye is an active player in visual environment processing:

Researchers at Harvard University have found evidence that the retina actively seeks novel features in the visual environment, dynamically adjusting its processing in order to seek the unusual while ignoring the commonplace. The scientists report in this week’s issue of the journal Nature on their finding that this principle of novelty-detection operates in many visual environments.
“Apparently our thirst for novelty begins in the eye itself,” says Markus Meister, the Jeff C. Tarr Professor of Molecular and Cellular Biology in Harvard’s Faculty of Arts and Sciences. “Our eyes report the visual world to the brain, but not very faithfully. Instead, the retina creates a cartoonist’s sketch of the visual scene, highlighting key features while suppressing the less interesting regions.”
These findings provide evidence that the ultimate goal of the visual system is not simply to construct internally an exact reproduction of the external world, Meister and his colleagues write in Nature. Rather, the system seeks to extract from the onslaught of raw visual information the few bits of data that are relevant to behavior. This entails the discarding of signals that are less useful, and dynamic retinal adaptation provides a means of stripping from the visual stream predictable and therefore less newsworthy signals.
For example, Meister says, in visual environments such as forests or fields of grass with many vertical elements but only rare horizontal features, the retina adjusts to suppress the routine vertical features while highlighting the singular horizontal elements.
Meister and his co-authors examined neural signals in retinal ganglion cells, which convey visual images from the eye to the brain. These cells generally record local spatial differences and changes over time rather than faithful renditions of momentary scenes. Scientists had interpreted this as a form of predictive coding, a strategy shaped by the forces of evolution in adaptation to the average image structure of natural environments.
“Yet animals encounter many environments with visual statistics different from this hypothetical ‘average’ scene,” Meister says. “We have found that when this happens, the retina adjusts its processing dynamically: The spatio-temporal receptive fields of retinal ganglion cells change after a few seconds in a new environment. These changes are adaptive, improving predictive coding by enhancing the ability of these receptive fields to pick out unusual features.”

The press release from Harvard…
The abstract…

The FDA warns about sudden blindness in one eye among rare patients on erectile dysfx drugs:

The Food and Drug Administration today approved updated labeling for Cialis, Levitra and Viagra to reflect a small number of post-marketing reports of sudden vision loss, attributed to NAION (non arteritic ischemic optic neuropathy), a condition where blood flow is blocked to the optic nerve.
FDA advises patients to stop taking these medicines, and call a doctor or healthcare provider right away if they experience sudden or decreased vision loss in one or both eyes. Further, patients taking or considering taking these products should inform their health care professionals if they have ever had severe loss of vision, which might reflect a prior episode of NAION. Such patients are at an increased risk of developing NAION again.
At this time, it is not possible to determine whether these oral medicines for erectile dysfunction were the cause of the loss of eyesight or whether the problem is related to other factors such as high blood pressure or diabetes, or to a combination of these problems.

More at WaPo….

The National Science Foundation is reporting about a study that is casting new light on how infection process occurs:

Using a novel system of microscopic channels, Harvard University researchers separated individual Escherichia coli cells from their typical “swarm” and videotaped them as they swam over different types of surfaces. A laboratory workhorse and common gastrointestinal bacterium, E. coli, preferred to swim near a gel-like porous surface with characteristics similar to biological tissues rather than near a glassy, solid one. In fact, they swam next to the porous surface for much longer periods of time.
First author Willow DiLuzio said, “Now that we’ve established the bacterium’s preference to swim toward a specific kind of surface, we hope to harness this basic information and focus on how to use it to direct movement in microfluidic, cell-based bioassays and sensors.”
The team developed a new technique to fabricate microchannels only 10 microns wide, or one-tenth the width of an average human hair. The walls of the channels were either a porous agar or a solid, commercially available silicone-rubber compound.
E. coli use long, whip-like structures called flagella to propel themselves. Motors in the cell’s wall spin the flagella into bundles that rotate counter-clockwise, creating a twist that causes the bacterium to rotate clockwise, or towards the right when viewed from above.
If cells were introduced to each end of the channel containing agar on the bottom, the cells preferentially swam on the right-hand side of the microchannel resulting in an ordered movement that resembled cars driving on a two-way street. And the microbes swimming closer to the agar surface moved faster than those swimming near the solid surface.
The authors propose that the bacteria closer to the porous surface experience less resistance and thus move faster.
“Because of E. coli’s size, relative to the spacing of surrounding water molecules, it’s analogous to a human trying to move through thick honey,” said DiLuzio. “Now, an entirely new set of hydrodynamic properties have to be considered in order to understand their movement as well as replicate it in man-made nano-devices.”
The surfaces of cells in the human body are often coated with a layer similar to agar. Future research into microbial movement will also be helpful in understanding how human infectious diseases develop and how infection might be halted in the body.

The press release…