How Is Flexible Working Memory Like Birds Flying in the Sky?

Random projections to higher cortical areas are key to flexible working memory.

Posted May 20, 2019

Have you ever visualized your higher cognitive thoughts "like birds flying through the sky?" I never did, until I saw a May 16 press release from the Princeton Neuroscience Institute about a new study, "A Flexible Model of Working Memory" by Flora Bouchacourt and Timothy Buschman. In the caption of an illustration (below) from this news release, the authors describe how representations of sensory stimuli "randomly project to higher cortical areas, where they are flexibly combined. This flexible workspace permits us to create higher cognitive thoughts, like birds flying through the sky."

 Credited to Flora Bouchacourt and Timothy Buschman of Princeton University.
Stimuli from our sensory world are processed separately through the prism of structured, ring-like, sensory networks in the brain. According to the new model of working memory from Princeton University's Flora Bouchacourt and Tim Buschman, these representations randomly project to higher cortical areas, where they are flexibly combined. This flexible workspace permits us to create higher cognitive thoughts, like birds flying through the sky.
Source: Credited to Flora Bouchacourt and Timothy Buschman of Princeton University.

This eye-grabbing illustration is credited to the Princeton neuroscientists, but also reminds me of Pink Floyd's iconic The Dark Side of the Moon album cover. The picture depicting Bouchacourt and Buschman's flexible model of working memory is definitely worth a thousand words. That said, the press release and abstract for this study are surprisingly laconic. The written words describing this new model of flexible memory leave a lot to the imagination.

The four-paragraph news release for the paper, "A Flexible Model for Working Memory," totals 228 words. Most of the statement directly quotes the 146-word study abstract with the addition of three short sentences: "A new article in Neuron from Flora Bouchacourt and Tim Buschman presents a new model of working memory. This work provides new insight into a core cognitive function in humans. Ongoing work hopes to understand how these mechanisms may be disrupted in neuropsychiatric diseases that disrupt working memory."

The Neuron article highlights four key aspects of this paper: (1) Random recurrent connections can support flexible working memory, (2) Overlap of connections causes interference between memories, limiting capacity, (3) [This] model captures many behavioral and physiological characteristics of working memory, (4) Structured sensory networks can constrain high-dimensional random representations. 

In the paper's abstract, Bouchacourt and Buschman provide a summary of their new model: 

     "Working memory is fundamental to cognition, allowing one to hold information 'in mind.' A defining characteristic of working memory is its flexibility: We can hold anything in mind. However, typical models of working memory rely on finely tuned, content-specific attractors to persistently maintain neural activity and therefore do not allow for the flexibility observed in behavior. Here, we present a flexible model of working memory that maintains representations through random recurrent connections between two layers of neurons: a structured “sensory” layer and a randomly connected, unstructured layer. As the interactions are untuned with respect to the content being stored, the network maintains any arbitrary input. However, in our model, this flexibility comes at a cost: The random connections overlap, leading to interference between representations and limiting the memory capacity of the network. Additionally, our model captures several other key behavioral and neurophysiological characteristics of working memory."

In my opinion, using symbolic illustrations to depict state-of-the-art neuroscience is refreshing. Currently, there's a movement to have younger students learn about well-established science by doing art projects (See, "Arts-Integrated Pedagogy May Enhance Academic Learning"). However, to the best of my knowledge, there aren't many neuroscientists using creative artistic expression to convey new models of how the brain works to a general audience. 

Drawbacks of Overthinking vs. Benefits of "Unclamping" Intellectual Machinery

Author's note: The following section of this post is a metacognition-based attempt to bring you inside the "flexible cognitive workspace" of my brain while holding lots of different ideas and information "in mind" about this new model of flexible working memory. 

As a science reporter, I read press releases for dozens of new studies every day. The recent press release from the Princeton Neuroscience Institute stood out, because there's so much food for thought in the breathtaking illustration provided by the authors. In my mind, the combination of these visuals with an unexpected reference to "birds flying through the sky" seemed to open up regions of my brain that facilitated a stream of consciousness and random free associations.

What follows is a spur-of-the-moment thought experiment purposely written in an "unclamped" style in the lobby of my gym. That being said, I apologize in advance for any non-sequiturs or if the following narrative doesn't unfold linearly or logically. The random "smorgasbord" of music, literary passages, and visuals in this section all emerged and coalesced in seemingly "structured" and "unstructured" parts of my working memory as I was processing the latest research from Princeton University on flexible working memory while jogging this morning.

Over the years, I've learned through trial-and-error that the best way for me to identify parallels between seemingly unrelated ideas is to take in a lot of evidence-based knowledge while sitting at my desk and then to go for a long jog. Running seems to facilitate daydreaming and mind-wandering in a way that helps my brain connect the dots of random ideas and increases the odds of having creative breakthroughs. I have a hunch that bipedal motion and aerobic activity may enhance the flexibility of working memory.

     "Look around, choose your own ground. For long you live and high you fly. And smiles you'll give and tears you'll cry. And all you touch and all you see. Is all your life will ever be." —Lyrics to "Breathe” from The Dark Side of the Moon by Pink Floyd

From a meta-cognitive perspective, the millisecond I saw the illustration from the authors of the new paper, "A Flexible Model of Working Memory" (Bouchacourt & Buschman, 2019), I started humming "Breathe," which opens with sound effects that include a pounding heart and a cawing bird. As my mind’s eye visualized cognitive flexibility as birds flying through the sky for the first time, my brain was also flooded with an array of random memories from childhood, songs, poetic verse, other scientific studies, etc.

 Photo and illustration by Christopher Bergland (Circa 2009)
This rudimentary sketch is a hypothetical illustration of how cognitive flexibility might rely on bidirectional flow between cortical and subcortical regions in all four hemispheres.
Source: Photo and illustration by Christopher Bergland (Circa 2009)

At first glance, someone might assume that the illustration accompanying the new working memory study is a "right-brain" way to present "left-brain" empirical evidence. I don't see it that way. Back in the late-1970s, my father, Richard Bergland (1932-2007), got into some hot water when he agreed to be the medical expert for the bestselling book, Drawing on the Right Side of the Brain. At the time, Dad was chief of neurosurgery at Harvard Medical School’s Beth Israel Hospital, but he was also a writer and liked making brain sculptures out of the extra clay my mom (who was a potter) had in her ceramic studio. Around 2005, my father and I created a split-brain model we called "up brain-down brain." This model was intended to shift the focus from left-right to the divide between cortical regions in the cerebrum and microzones of the cerebellum.

In the 20th century, key elements of the "left brain-right brain" neuromyth took center stage as an overly simplified way to explain hemispheric differences between the left and right sides of the human cerebrum. The basic premise of Drawing on the Right Side of the Brain (1979) is that the "right cerebral hemisphere" is the seat of creative thinking and artistic expression. Of course, we know now that the whole brain works in concert to facilitate all types of thinking. And that neuroplasticity makes it possible for remote brain regions to pick up the slack for another area in a compensatory way, if necessary.

The illustration of "birds flying through the sky" depicting a new model of flexible memory triggered auditory flashbacks and images of me listening to The Dark Side of the Moon in my boarding school dorm room during adolescence. For some reason, the description in the caption also reminded me of a passage by William James (1842-1910) from The Gospel of Relaxation, along with visualizations of the "immersed chain" from one of my favorite Arthur Koestler (1905-1983) quotations about the creative process. Koestler once said, "True creativity begins where language ends." I agree.

Again, from a meta-cognitive perspective, the hodgepodge of visuals, sounds, and semantics that can float around simultaneously within our working memory is fascinating. The reason I've chosen to include this array of content is that these random connections are overlapping in my working memory, and (as the authors warned) the interference may be limiting my working memory capacity. Here's a quote by Koestler that addresses the "short-circuits" of reasoning: 

     "The moment of truth, the sudden emergence of a new insight, is an act of intuition. Such intuitions give the appearance of miraculous flushes, or short-circuits of reasoning. In fact they may be likened to an immersed chain, of which only the beginning and the end are visible above the surface consciousness. The diver vanishes at one end of the chain and comes up at the other end, guided by invisible links." —Arthur Koestler (The Act of Creation, 1964) 

In the next passage, William James seems to be promoting cognitive flexibility and a way to maintain flexible working memory by "unclamping" one's structured intellectual machinery. For some reason, in light of the new paper from Princeton, the word "unclamp" evokes an image in my mind's eye of freeing "birds of thought" from a cage: 

     “When once a decision is reached and execution is the order of the day, dismiss absolutely all responsibility and care about the outcome. Unclamp, in a word, your intellectual and practical machinery, and let it run free; and the service it will do you will be twice as good. Who are the scholars who get "rattled" in the recitation-room? Those who think of possibilities of failure and feel the great importance of the act. Who are those who recite well? Often those who are most indifferent. Their ideas reel themselves out of their memory of their own accord.” —William James (The Gospel of Relaxation, 1911)

 Giani/Pixabay
Birds flying through the sky at sunset.
Source: Giani/Pixabay

Although the new paper, "A Flexible Model of Working Memory" (2019), doesn't mention "Aha!" or "Eureka!" moments, the description of higher cognitive thoughts emerging from "a randomly connected, unstructured layer" reminds me of how Carola Salvi of Northwestern University differentiates between people solving problems via methodical analysis or a flash of insight.

Hypothetically, it seems that the sudden insight of an "Aha!" moment might have something to do with higher cognitive thoughts emerging from an unstructured, flexible workspace, "like birds flying through the sky." (See, "Where Do 'Eureka!' Moments Come From?," "Why Does Overthinking Sabotage the Creative Process?" and "The Neuroscience of Imagination.")

References

Flora Bouchacourt and Timothy J. Buschman. "A Flexible Model of Working Memory." Neuron (First published: May 15, 2019) DOI: 10.1016/j.neuron.2019.04.020