How Memory Works for the Navigationally Challenged

If this chart makes sense to you, watch the rest of the video here:

The Uses of Memory in Olfactory Search, Antonio Celani Senior Researcher at ICTP, MaLGa Colloquia series, 20th February 2023 (this screenshot taken at 22min)

https://www.youtube.com/watch?v=vlnY7CZXtqw

He uses a quote from Flatland, come on. The presenter, Antonio Celani, was a researcher for the French National Research Council (CNRS) in 2000 - and in 1999, CNRS had a European Symposium on Olfaction and Cognition.

But in other news:

Neuroscientists find that animals replay incidentally encoded episodic memories

Jan 2024, phys.org

https://medicalxpress.com/news/2024-01-neuroscientists-animals-replay-incidentally-encoded.html

(This breakthrough in neuroscience research expands on a 2018 study that first reported evidence that animals can replay past events)

Researchers gave nine rats a list of odors using many common household spices, like cinnamon and paprika. Then, the rats were given a memory assessment where they were presented with two scents from the previous list. The rats must then choose which scent was the third-to-last scent presented.

placed rats in a radial maze where they were confronted with scented lids covering food. After the rats foraged through the maze, they were presented with the opportunity to report the third-to-last scent, having to draw from memory the previously presented scents.

The rats remembered multiple pieces of putatively unimportant information and later replayed a stream of episodic memories when that information was needed to solve an unexpected problem. The first and only trial run ended with a 100 percent success rate.

"We remember information even though it was seemingly unimportant when it was encountered. When we happen to need that information, we replay the stream of events to identify the information needed to solve our current problem."

via Indiana University: Cassandra L. Sheridan et al, Replay of incidentally encoded episodic memories in the rat, Current Biology (2024). DOI: 10.1016/j.cub.2023.12.043

https://dx.doi.org/10.1016/j.cub.2023.12.043

You Don't Know What You're Missing

Attention and memory deficits persist for months after recovery from mild Covid

University of Oxford News, Jan 2022

https://www.ox.ac.uk/news/2022-01-19-attention-and-memory-deficits-persist-months-after-recovery-mild-covid

"Although our Covid-19 survivors did not feel any more symptomatic at the time of testing, they showed degraded attention and memory."

-Dr Sijia Zhao of the Department of Experimental Psychology, University of Oxford

Repasted from above article:

All the participants had previously suffered from Covid-19 but were not significantly different from a control group at the time of testing on factors such as fatigue, forgetfulness, sleep patterns or anxiety.

But, they displayed significantly worse episodic memory and a greater decline in the ability to sustain attention over time than uninfected individuals for 6-9 months.

Note, the COVID-19 survivors in this study were young, mean age around 28, n=136.

How bad was it? Here is a measurements for context: Over the course of the 9-minute experiment, control participants’ accuracy dropped from 78.5% to 75.4%, whilst COVID survivors started with a similar baseline at 75.5%, reducing to 67.8% ... For a 30-minute memory test, COVID-19 survivors showed a significant memory decrement which was larger than in controls by 9.2%.

And to be specific: The larger episodic memory decrement amongst COVID-19 survivors was driven by errors in which the wrong orientation was chosen for a correct item. This difference suggests that the deficit in episodic memory in the COVID group might be associated with a deficit in binding information in memory. 

Interesting: word-memory tasks showed no change. 

How it might happen, if you're interested: One investigation of COVID-19 survivors demonstrated that the most severely cognitively affected patients demonstrated a degree of cognitive impairment accompanied by hypometabolism in the frontoparietal regions. These brain regions are implicated in sustained attention as well as in episodic memory. Reassuringly, the follow-up study of Hosp et al. showed slow but evident improvement after 6 months.

Last thing: The good news is that COVID-19 survivors performed well in most cognitive abilities tested, including working memory, executive function, planning and mental rotation. 

via University of Oxford: Rapid vigilance and episodic memory decrements in COVID-19 survivors. Zhao et al. Brain Communications. Jan 2022. https://academic.oup.com/braincomms/article/4/1/fcab295/6511053

How Is This Related to Smell?

We already know that changes in our ability to smell were the primary symptom of the initial varieties of covid. Some of us still deal with these changes. But something we also know, regardless of any pandemic, is that smell is tightly linked to episodic memory -- "grandma's attic" or "first boyfriend's cologne" -- and a subset called autobiographical memory. These type of memories tie together people, places, feelings and smells into the olfactory cluster. Chemosensation enabled the first navigation, as primordial protists sniffed their way through the soup of early Earth. Chemosensation enabled the first social experience, when you detected your mother's immunity profile via her amniotic fluid. And chemosensation enabled your primate ancestors to remember where that really ripe fruit tree was. 

So it does seem appropriate that a virus attacking your olfactory neurons would also affect your episodic memory.

Image credit: Just astrocytes, upsplash

Post Script:

For those who haven't heard about this enough already, here's a good reminder of what Long Covid is: People who survive COVID-19 infection present a significantly higher risk of major neurological and psychiatric conditions, particularly if they were hospitalized. These include acute cerebrovascular events such as ischaemic stroke and intracerebral haemorrhage. In addition to severe neurological conditions, there can also be more chronic, longer-term consequences such as fatigue, low motivation, disturbed mood and poor sleep—all commonly reported symptoms amongst survivors, the so-called long-COVID (see recent review). -source

Your Mother

Word.

Somewhere in England they are now programming smoke alarms with your mother's voice instead of an ear piercing siren, because it gets you out of bed quicker. The precious seconds saved could also save lives.

The reason the sound of your mother's voice can turn on your inner alarm faster than a fog horn, has a lot to do with our nature as social creatures, and of course, our limbic systems.

The limbic system is the part of us that takes flight in a dangerous situation. It is a brain inside our brain, and if it had a brain inside it, that would probably be the amygdala; I'm sure you've heard of it. It also holds the hippocampus, also known as the memory bank.

The limbic system operates beyond our conscious control. It has to, because it's a big part of what keeps us alive before we even become "conscious." It learns from its environment, and responds accordingly. A major part of that environment is the people around us.

Our status as social animals makes us very sensitive to the people around us, and especially those who take care of us, and especially even more those who take care of us when we're young.

This is because our limbic system is, shall we say, very open to suggestion when we're young. It's kind of like a blank slate of a book, or an instruction manual, where every word that's written starts out really big, and gets smaller and smaller as we age.

And who is one of the first people to write in this book? Your mother. She codes her voice so deep into your autonomic nervous system that the sound of it can activate your limbs faster than flash of lightning.

So it only makes sense that if we are looking for a shortcut to the body-control-system, this would be it.

Notes

Mum's voice makes better smoke alarm for children

Oct 2018, BBC

Robet Sapolski's Stanford lectures in Human Behavioral Genetics are a great place to learn about this kind of thing; he is a skilled and engaging lecturer.

Millions on prescription sleeping pills would sleep through a fire alarm
Jan 2019, phys.org

Post Script

Consider this idea in light of the developments we see today in robotics, or in any instance of digitally-mediated human assistance. Robots that take care of the elderly in the absence of their progeny, or who take care of people of reproductive age in the absence of a mate. The limbic system is a powerful thing, and it will certainly be exploited.

Post Post Script

Elon Musk did a surprisingly interesting job of describing all ^this in his infamous interview on the Joe Rogan show.

Post Post Post

Amygdalic is a word, but it doesn't do what you want it to in this context. It comes from chemistry and it means made of almonds, or rather the amygdalin contained therein. And now you got me started, almonds do also contain cyanide, but not enough to kill you, you robust biological specimen! If you ever had a rotten almond, you can pretend that's the cyanide in your mouth. Not totally sure about that, but there is another species of almond, actually called the bitter almond, that has more cyanide in it, and is also the almond used to make almond fragrance. The amygdala got its name because it is shaped like an almond.

Limbic Fitness and The Aging Brain

We all know that memory function decreases as we age. One of the ways in which this is evidenced is in the correlation between how much our eyes move and the brain activity that comes with it. You see grandpa's eyes skipping around the room, from one face to another, but he isn't recording any of it. (Exaggeration of course, depends how old he is, and his mental capacity.)

It's normal for people of all ages that the more we look at the same thing, the less and less brain activity there is in our memory-forming hippocampus. But in older folks, they can dart their eyes all over the place, and yet generate no information about what they see. No matter how many times they look at a thing, it can remain unfamiliar.

Despite the fact that smell is typically associated with airtight bear-trap memories, we can experience similar diminishing effects with our sense of smell. The relationship is so intimate that our olfactory perception is used to forecast dementia decades in advance.

It is certainly possible that your 60-year old self can be transported 50 years into the past by the mere wisp of familiar a molecule. But your 110-year old self will be less likely to transport so swiftly back to your 60's - the older we get, the less robust the memory-complex formed by each sensation.

This is covered pretty thoroughly in Hidden Scents. Olfaction, the limbic system and our episodic memory form a powerful complex of stored experience. But this system works less and less as we age-out of episodic memory and begin to rely more regularly on semantic memory for our day to day activities.

Episodic memories, i.e., the collection of feelings in your body during a particular episode in your life, are very powerful when recalled. Ironically, they cannot be recalled at will. They must come to us from outside, unlocked by a face, a voice, or a smell. The name of a friend from first grade doesn't do it. The smell of the inside of your first lunchbox, that'll do it.

You're way less likely to be brought to tears at the re-smelling of your first new car (if you were to somehow recreate that, or be so lucky as to be exposed to it later in life). Your dad's first new car - the one you got to ride in when you were 8 - smelling that might get emotional.

Notes:

Link between what we see and how we remember 'breaks' as we get older

Oct 2018, phys.org

Zhong-Xu Liu et al, Age-related changes in the relationship between visual exploration and hippocampal activity, Neuropsychologia (2018). DOI: 10.1016/j.neuropsychologia.2018.07.032

Image source - link

On Potent Memories vs Weak Memories

Image source

Lots of discoveries have been popping up on the subject of memory. UK scientists won the Brain Prize for showing how memories are stored in the brain, based on the “fire together, wire together” theory.

Some recent work on how we forget has come up that reminds us why our smell memories stay potent forever. The idea that we forget memories after repeatedly recalling similar memories has been around for a while, but for the first time, scientists show evidence of active repression.

In Hidden Scents: The Language of Smell in the Age of Approximation, the potency and tenacity of our smell memories are discussed as an analogy to the concept of lossy data in computer science. In the study linked above, memories that are repeatedly accessed have a negative lasting effect of on the fidelity of similar memories. In computer science, every time a .jpg is opened and re-saved, it loses some of its data due to compression. This is what lossy data compression is about.

For smell memories however, where the memory is instigated by a unique signature of aroma compounds (one that might represent your grandparents’ attic, for example), this process of retrieval and re-saving does not happen for perhaps forty years. And then one day: You know that feeling – it’s called the Proustian moment, after the most widely recognized description of olfactory memory in literary fiction – it’s when you walk into a room and you’re hit, halted in your tracks, and assaulted by your past, captured in a moment that consumes your awareness.

“Oh my….oh…that’s…that’s my grandparents’ attic – I haven’t thought about that in forty years.”

And you shiver, you time-traveler, re-living a most personal page in your autobiography. Again, the reason smells can do this to us is because these instigating signatures, these unique aroma profiles, are such a complex and nuanced combination of molecules that the chances of your encountering them on a regular basis can be very small. There is no opportunity to rewrite the data. It just sits there forever, waiting.

There’s more to the story of course, like the fact that these memories are a holistic conglomerate of spatiotemporal, physiological data about the precise state of your body at the moment of encoding, but that’s already too much for today.

Notes:

Repeated remembering 'wipes similar memories'

March 2016, BBC News

http://www.bbc.com/news/science-environment-31909935

Pericytes in the Neurovasculature

Nature Neuroscience, May 2016

'Brain Prize' for UK research on memory mechanisms

March 2016, BBC News