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Graphs, visual representations outlining the relationships between different entities, concepts or variables, can be very effective in summarizing complex patterns and information. Past psychology studies suggest that the human brain stores memories and experiences following graph-like and structured patterns, specifically as a network of associations, also referred to as cognitive graphs.

These cognitive graphs are hypothesized to represent different concepts as “nodes” and the relationships between these concepts as edges connecting these nodes. By organizing information in a structured way, they can allow people to apply knowledge they have acquired in the past to new situations and draw conclusions about what is happening based on previous experiences.

The role of cognitive graphs has been widely investigated in the past, with most studies focusing on their contribution to the storage and retrieval of facts and knowledge (i.e., declarative memories). In contrast, the extent to which they influence the planning and control of movements remains poorly understood.

Researchers at Yale University recently set out to investigate the possibility that the human brain also stores memories related to movement as mental graph-like structures, which are then used to plan motor actions in response to visual stimuli. Their paper, published in Nature Human Behavior, presents new evidence suggesting that the brain stores visuomotor associations in structured ways and can then retrieve these associations to plan movements in specific situations.

“Much of human memory takes the form of cognitive graphs that allow us to relate and generalize knowledge,” wrote Juliana E. Trach and Samuel D. McDougle in their paper. “The influence of structured memory in the motor system is less clear. We examine how structured memory representations influence action selection when responses are retrieved from newly learned, hierarchical visuomotor maps.”

As part of their study, the researchers carried out a series of experiments involving 182 participants. These participants were asked to complete a task that required them to press specific buttons in response to different visual cues (e.g., geometrical objects with different shapes or colors) that appeared on a screen.

Notably, they were asked to quickly press a different combination of keys in response to what they saw. For some participants, the associations between what they saw and the keys they were asked to press followed a structured pattern, while for others they were random.

The researchers recorded the time it took for participants to press the correct key combinations. These response times were then analyzed to try to determine whether people were in fact using a mental graph to guide their actions during their experiment.

“Human participants learned visuomotor mappings with (or without) an imposed latent structure that linked visual stimulus features (for example, color or shape) to intuitive motor distinctions, such as hands and pairs of fingers,” explained Trach and McDougle.

“In participants who learned structured visuomotor mappings, transitional response times indicated that retrieving the correct response from memory invoked the ‘traversal’ of a structured mental graph.”

In some trials of the experiment, the researchers also asked participants to press the key combinations as fast as possible or at specific times to determine whether their performance changed when under pressure. Overall, the data they collected suggests that associations between visual stimuli and motor actions are represented as mental graphs, which can be retrieved to guide future actions, even under pressure.

“Forced-response experiments revealed similar computations within individual trials,” wrote Trach and McDougle. “Moreover, graph-like representations persisted even after multiple days of practice with the visuomotor mappings. Our results point to direct links between internal computations over structured memory representations and the preparation of movements.”

This recent study offers new interesting insights into the contribution of mental graphs to the planning and execution of movements. Future research could help to validate the team’s findings, while also potentially examining the role of these structured cognitive representations in a wider range of real-world scenarios.

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Data from CDC indicates this may be a bad tick season. Experts offer tips to reduce your chance of coming down with Lyme disease, ehrlichiosis and other tickborne diseases, and what to watch out for.

ANDREW LIMBONG, HOST:

It’s looking like a bad year for tick bites. Data from the CDC show people are seeking emergency care at the highest rates since 2019. So if you are planning a hike or a trip to the park and you want to avoid these blood-sucking bugs, NPR’s Pien Huang has some tips to help you fend them off.

PIEN HUANG, BYLINE: There are about a dozen different ticks in the U.S. that can cause problems for human health. In the northeast, mid-Atlantic and upper Midwest, the biggest problem is Lyme disease. Thomas Hart is an infectious disease microbiologist at Johns Hopkins University in Maryland. He says Lyme disease is transmitted by infected deer ticks.

THOMAS HART: You can encounter these ticks really at any time of the year, but they’re going to be the most active in warmer months, and they tend to live in woody or grassy areas.

HUANG: In the central and southeastern U.S., ehrlichiosis and spotted fever rickettsiosis are top concerns, along with a tick-induced allergy to red meat. Tick bites are less common in the west, but they also happen there and can spread Lyme disease, anaplasmosis and a few other things. So if all of this is making you itchy, Alison Hinckley, an epidemiologist with CDC, says there are precautions you can take.

ALISON HINCKLEY: You can wear insect-repellent-treated clothing. We call that permethrin-treated clothing. That’s a really easy thing to do.

HUANG: Cover up as much skin as possible and check yourself daily.

HINCKLEY: Showering when you come in from outside really has shown to be a good way to prevent tick-borne diseases.

HUANG: That’s because the longer a tick feeds on you, the higher the risk of infection. So if you find a tick, take it off right away. The best way is to use tweezers, grab it as close to the skin as you can, and find out what type of tick it is and how long it’s been feeding on you. If it’s a deer tick and you’re in an area where Lyme disease is common, Hinckley says see a doctor.

HINCKLEY: The only time you would get an antibiotic after a tick bite and before any symptoms, it would be to prevent Lyme disease. And in that case, we recommend just a single dose.

HUANG: Otherwise, watch for symptoms like fever, aches and rash. If those show up, Hinckley says, seek medical care. You wouldn’t be alone. Some 31 million people get tick bites each year.

Pien Huang, NPR News.

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How much nori, dulse, or arame approximates the recommended daily allowance for iodine?

Dairy milk supplies between a quarter and a half of the daily iodine requirement in the United States, though milk itself has “little native iodine.” The iodine content in cow’s milk is mainly determined by factors like “the application of iodine-containing teat disinfectants,” and the “iodine residues in milk originate mainly from the contamination of the teat surface…” Indeed, the teats of dairy cows are typically sprayed or dipped with betadine-type disinfectants, and the iodine just kind of leaches into their milk, as you can see at 0:35 in my video Friday Favorites: The Healthiest Natural Source of Iodine. 

Too bad most of the plant-based milks on the market aren’t enriched with iodine, too. Fortified soy milk is probably the healthiest of the plant milks, but even if it were enriched with iodine, what about the effects soy may have on thyroid function? When I searched the medical literature on soy and thyroid, this study popped up: “A Cost-Effective, Easily Available Tofu Model for Training Residents in Ultrasound-Guided Fine Needle Thyroid Nodule Targeting Punctures”—an economical way to train residents to do thyroid biopsies by sticking the ultrasound probe right on top a block of tofu and get to business, as you can see below and at 1:10 in my video. It turns out that our thyroid gland looks a lot like tofu on ultrasound.

Anyway, “the idea that soya may influence thyroid function originated over eight decades ago when marked thyroid enlargement was seen in rats fed raw soybeans.” (People living in Asian countries have consumed soy foods for centuries, though, “with no perceptible thyrotoxic effects,” which certainly suggests their safety.) The bottom line is that there does not seem to be a problem for people who have normal thyroid function. However, soy foods may inhibit the oral absorption of Synthroid and other thyroid hormone replacement drugs, but so do all foods. That’s why we tell patients to take it on an empty stomach. But you also have to be getting enough iodine, so it may be particularly “important for soy food consumers to make sure their intake of iodine is adequate.”

What’s the best way to get iodine? For those who use table salt, make sure it’s iodized. “Currently, only 53% of salt sold for use in homes contains iodine, and salt used in processed foods typically is not iodized.” Ideally, we shouldn’t add any salt at all, of course, since it is “a public health hazard.” A paper was titled: “Salt, the Neglected Silent Killer.” Think it’s a little over the top? Dietary salt is the number one dietary risk factor for death on planet Earth, wiping out more than three million people a year, twice as bad as not eating your vegetables, as you can see here and at 2:38 in my video. 

In that case, what’s the best source of iodine then? Sea vegetables, as you can see below and at 2:50. We can get a little iodine here and there from a whole variety of foods, but the most concentrated source by far is seaweed. We can get up to nearly 2,000 percent of our daily allowance in just a single gram, about the weight of a paperclip. 

“Given that iodine is extensively stored in the thyroid, it can safely be consumed intermittently,” meaning we don’t have to get it every day, “which makes seaweed use in a range of foods attractive and occasional seaweed intake enough to ensure iodine sufficiency.” However, some seaweed has overly high iodine content, like kelp, and should be used with caution. Too much iodine can cause hyperthyroidism, a hyperactive thyroid gland. A woman presented with a racing heartbeat, insomnia, anxiety, and weight loss, thanks to taking just two tablets containing kelp a day.

In my last video, I noted how the average urinary iodine level of vegans was less than the ideal levels, but there was one kelp-eating vegan with a urinary concentration over 9,000 mcg/liter. Adequate intake is when you’re peeing out 100 to 199 mcg/liter, and excessive iodine intake is when you break 300 mcg/liter. Clearly, 9,437 mcg/liter is way too much. 
 
As you can see below and at 3:57 in my video, the recommended average daily intake is 150 mcg per day for non-pregnant, non-breastfeeding adults, and we may want to stay below 600 mcg a day on a day-to-day basis, but a tablespoon of kelp may contain about 2,000 mcg. So, I’d stay away from kelp because it has too much iodine, and I’d also stay away from hijiki because it contains too much arsenic. 

This can give you an approximate daily allowance of iodine from some common seaweed preparations: two nori sheets, which you can just nibble on them as snacks like I do; one teaspoon of dulse flakes, which you can just sprinkle on anything; one teaspoon of dried arame, which is great to add to soups; or one tablespoon of seaweed salad.

If iodine is concentrated in marine foods, “this raises the question of how early hominins living in continental areas could have met their iodine requirements.” What do bonobos do? They’re perhaps our closest relatives. During swamp visits, they all forage for aquatic herbs.  

Doctor’s Note:

This is the second in a four-video series on thyroid function. If you missed the previous one, check out Are Vegans at Risk for Iodine Deficiency?.

Coming up are The Best Diet for Hypothyroidism and Hyperthyroidism and Diet for Hypothyroidism: A Natural Treatment for Hashimoto’s Disease.

What else can seaweed do? See the related posts below.

Haley Lyndes (she/her) is a shopping writer and editor with more than seven years of experience in the publishing space. Specializing in home and lifestyle, she covers everything from furniture and mattresses to beauty products and fitness gear. Previously, she was an SEO commerce writer for Apartment Therapy and The Kitchn. Her writing has appeared in Buzzfeed, Travel & Leisure, and Real Simple. When she’s not reviewing her latest home finds or interviewing celebrities, you’ll likely find her out for a run — she’s also a marathoner.

Marisa Petrarca (she/her) is a contributing editor for PS Shopping and has over seven years of experience writing and editing beauty, fashion, and lifestyle content. She was previously the senior beauty editor at Grazia USA and the style and beauty editor at Us Weekly. Now freelancing, her work has been featured in Cosmopolitan, Allure, Marie Claire, and more.

Chandler Plante (she/her) is an assistant health and fitness editor for PS. She has over four years of professional journalism experience, previously working as an editorial assistant for People magazine and contributing to Ladygunn, Millie, and Bustle Digital Group