Week in Review: Number 27

How the Brain Relies on Sight in the Absence of Touch
Somatosensation, the combined sense of touch and proprioception, is integral to how we navigate our body in space. We are aware of our embodiment even when we close our eyes. But what happens when we lack this sensory experience from our body, and how does our brain adapt? How do other senses, notably sight, compensate to generate a sense of the body? Researchers recently had that opportunity to study two unique individuals without somatosensation, one case acquired, the other congenital. Ian from the U.K. developed a complete loss of his sense of touch and proprioception (the awareness of our body's position and movement) below the neck at age 19 after what is believed to be an autoimmune response after illness; Ian required months of rehabilitation to learn to move his body and limbs again. Kim from the U.S., on the other hand, was born without sensory nerve fibers to feel her body, consequently possessing neither touch sensation nor proprioception.

For the study, Ian and Kim, along with age-matched controls, participated in experiments designed to assess their mental image of their bodies and their unconscious sense of their bodies in space. The researchers found that Kim's representation of her hand was closer to that of the controls in that both were distorted; for the controls, this is due to a distorted sensory map. Ian, by contrast, had a more accurate representation of his hand compared to Kim and the controls. The investigators hypothesize that the greater accuracy is because Ian's hands are always under his conscious control. In an experiment related to body schema, the researchers looked at how the participants reacted when a visual target appeared near their hand, i.e., within their peri-personal space. Those with intact proprioception would react rapidly. They found that Kim's results closely matched the controls compared to Ian's, suggesting that Kim has an unconscious representation of her body despite never having been able to feel it. This is similar to the way a person will instinctively duck when a ball flies toward them, even before consciously processing what the object is. Ian, however, relies on much slower processes involving conscious visual perception. The differences between Ian's and Kim's conditions highlight how conscious compensatory mechanisms developed in adulthood after sensory loss differ from the neuronal reorganization that might occur in a person born without that sense. However, whether unconsciously or consciously, we all arrive at a sense of self. As one of the researchers concludes, "What we can learn from this is that you might not do it in the way that others do it, but you will find a way to make a body schema. You will find a way to make a sense of yourself."

Interhemispheric Transfer of Visual Working Memory
When we shift our gaze around to look at a scene, or even temporarily turn away, we rely on visual working memory to retain what we see in mind. The ability to hold that memory enables volitional control of our actions, allowing us to decide to react to something now or later. This visual working memory is a cognitively interesting feat, given that our left visual hemifields correspond to our right cerebral hemisphere, and our right visual hemifields correspond to our left cerebral hemisphere. New research by neuroscientists at MIT, using animal primate models, found that when an object shifts across our field of view, either because it moved or because our eyes did, the brain immediately transfers a memory of it to the opposite (contralateral) brain hemisphere, in particular, to a group of neurons in the prefrontal cortex. Remarkably, even though the new group of neurons encodes the object in the new position, the brain continues to recognize it as the same object that had been in the other hemisphere's field of view. That being said, results in monkeys indicate decreased performance in cases where the monkeys had to shift their gaze, suggesting that shifting gaze requires extra cerebral processing. This switch from one side of one's field of view to the other is accompanied by a signature change in the rhythm of brain wave frequencies to transfer the memory information from one side of the brain to the other. The news article explains, "As the transfer occurred, the synchrony across hemispheres of very low frequency 'theta' waves (~4-10 Hz) and high frequency 'beta' waves (~17-40 Hz) rose and the synchrony of 'alpha/beta' waves (~11-17 Hz) declined." The lead author of the study adds, “This is another form of gating. This time alpha/beta is gating the memory transfer between hemispheres.” Perhaps the most surprising discovery from the experiments was that the prefrontal cortex uses different neurons to encode the memory of an object depending on whether the object (in the same spot of the visual field) was initially seen at that location or transferred there from the other hemisphere. The scientific implication of that finding is the idea that even the same information could still be encoded by different, arbitrarily assembled ensembles of neurons.

Radiology Insights into COVID-19 Ocular Abnormalities
The COVID-19 pandemic has affected the entire globe since its onset in early 2020, including impact in all specialties of healthcare. Within ophthalmology, SARS-CoV-2 has been linked with ocular complications from conjunctivitis to retinopathy. Insight from radiology provides additional clues of ocular abnormalities in individuals with severe COVID-19. A study by researchers at the French Society of Neuroradiology (SFNR), from a sample of 129 patients with severe COVID-19 who underwent brain MRI, found that nine of those patients, eight of whom had spent time in the intensive care unit (ICU) for COVID-19, had abnormal MRI findings of the globe. Specifically, the MRI scans showed one or more nodules in the posterior pole, the first time these findings have been described using MRI. The nodules occurred in the macular region in all nine patients, eight of whom showed a bilateral presentation and two of whom additionally had nodules beyond the macula. The mechanism of nodule formation is unknown, although the researchers speculate a relation to inflammation triggered by the virus as well as inadequate ocular venous drainage while prone or intubated during hospitalization. This study aligns with other research showing that COVID-19 has greater impact on those with preexisting health conditions; among the nine patients with eye nodules, two had diabetes, six were obese, and two had hypertension. Eight of the nine patients were men. The researchers will monitor the COVID-19 survivors to see if there is any visual impairment from the nodules. The first author of the study comments that because patients with severe COVID-19 are often being treated for much more severe, life-threatening conditions, eye problems could go unnoticed in the clinic. He states, “Our study advocates for screening of all patients hospitalized in the ICU for severe COVID-19. We believe those patients should receive specific eye-protective treatments.” Additionally, the researchers will conduct a prospective study with dedicated high-resolution MRI to explore the eye and orbit in patients with mild to moderate COVID-19.

Archeologists Examine a Color-Matching Device
Color perception, something most of us take for granted, is ultimately a subjective and individual experience. The ability to perceive and identify colors, however, becomes functionally relevant in some professions, such as interior design and cosmetology, or even archeology as in this case. Because color perception is subjective, scientists were excited when a handheld color-matching gadget called the X-Rite Capsure came on the market. Made by the same company that owns Pantone, they had hoped that it would offer a consistent way of determining color, free of human bias as well as variations in lighting, sample quality, and observer perspective. However, a study by archeologists, to whom the device was marketed to identify the color of artifacts and soil samples, found that the X-Rite Capsure often misreads colors readily distinguished by the human eye when tested against the Munsell color system, the current archeological standard for identifying colors using a binder of 436 unique color chips. The study specifically tested the Capsure's readings for all 436 color chips as well as 140 pottery briquettes for the three elements of Munsell’s system: a color’s general family (hue), intensity (chroma), and lightness (value). The details of how the X-Rite Capsure differed from human observers in determining color can be found in the articles. These differences are not functionally trivial, however, since identifying subtle differences in color gives information about a sample's composition, origins, and history of use. Highlighting a device that is functionally relevant within the field of archeology, the researchers argue, “We need to pay really close attention and record how we’re describing color in order to make good data. Ultimately, if we’re putting bad color data in, we’re going to get bad data out.” Because the device is nonetheless internally consistent in its color identifications, work remains to optimize the advantages of such devices and artificial intelligence to match human perception, arguably difficult for a quality as complex as color.

Literacy Screening Tool Developed for Young Children
“By screening early during pediatric clinic visits, especially in practices serving disadvantaged families, we can hopefully target effective interventions that help children better prepare for kindergarten and improve reading outcomes,” the author of a book called The Reading House  offers. The researchers at Cincinnati Children's Hospital developed the book (series) as a literacy screening tool for children ages 3 to 5 to facilitate the early identification of reading difficulties in primary care and preschool settings. The present study, involving 70 healthy children (34 boys and 36 girls) between 3 and 5 years of age from various socioeconomic backgrounds, sought to validate the book as a literacy screening tool. The children completed standardized assessments of literacy skills related to vocabulary, rhyming and rapid automatized naming. Fifty-two of these children also completed magnetic resonance imaging (MRI), including measurement of cortical thickness, with thicker cortices (especially in the left hemisphere involved with language processing) being predictive of better reading outcomes. They found thicker gray matter cortex in the cerebral left hemisphere in children with higher TRH scores. Higher TRH scores were also strongly correlated with higher vocabulary, rhyming and rapid naming scores, according to the researchers. Finally, the researchers found that children from lower-SES households had a less mature ("strained") cortical pattern and thinner cortices overall compared to children from higher-SES households.

In Other News
(1) Color vision in butterflies
(2) Comprehensive eye exams before going back to school
(3) Can an experimental eye disease drug treat COVID-19 associated lung problems?