Geological Processes

What fascinates me about geological processes is their cyclical nature. In a previous discussion, I examined the origins of coastal sand. Mountains and bodies of water engage in a dynamic interplay, with water usually leading this cycle.

The cycle can be summarized as follows: - Rain to river to ocean to cloud to rain. - Mountain to rock to sand to rock to mountain.

Desert sand, however, has a different story. It remains contained and compartmentalized. The sand at Eureka Dunes is static for an extended period.

Eureka Valley, where Eureka Dunes resides, is a flat basin enveloped by mountain ranges. Evidence of water runoff from these mountains can be observed on the valley floor (see the accompanying image or satellite view). Water erosion breaks down rocks, which the wind further erodes.

Certain rocks become small enough that powerful winds can transport them to the southern end of the valley, where they are deposited. The accumulation of sand has resulted in one of North America's tallest dunes, reaching heights of up to 680 feet.

This process is termed Aeolian, named after the Greek god of the winds, as these processes predominantly shape desert landscapes.

> “Wind. Wind strong enough to lift dust and clay thousands of feet; wind powerful enough to move rocks. It is wind that is the signature of the desert, if not its prime mover.” — Mary Hill, California Landscape: Origin and Evolution (1984).

Water remains the primary force, albeit infrequently. The Sierra Nevada mountains to the west intercept rainfall, with storms rarely extending beyond their ridges.

> “Most of the deserts of North America have been robbed of water by mountains that intercept rain before it can reach the thirsty deserts. In this manner, lands of eastern California and Nevada are left dry because they lie in the rain shadow of the high Sierra Nevada.” — Mary Hill.

Even when rain does occur, its primary role is to transport more rocks to the valley floor rather than to the ocean. While lighter particles may be carried away by wind, the heavier materials remain. Over time, the basin accumulates sand and salts. Only a significant flood, possibly due to climate change, could cleanse the basin of these materials.

Consciousness as a Cycle

Consciousness also exhibits cyclical characteristics. The state of being awake differs markedly from that of sleep. Although scientific literature often equates non-REM sleep with unconsciousness, this distinction is being reassessed. It is widely accepted that we experience heightened consciousness when awake, and that sleep is essential for restoring this state.

Are the brain's processes during sleep analogous to geological cycles? In geology, water serves as the key agent, transporting debris to the ocean for recycling. Interestingly, water plays a crucial role in the brain as well.

In a groundbreaking 2013 study, Maiken Nedergaard revealed how cerebrospinal fluid (CSF) infiltrates the mouse brain, navigates through cellular spaces, and subsequently drains out. This movement occurs rapidly through a convective exchange of CSF and interstitial fluid, rather than the slow process of diffusion.

Remarkably, this flushing of the brain only transpires during sleep or anesthesia. Upon awakening, this process halts.

> “Convection is basically like a river. It is fluid flow driven by a pressure gradient or gravity, for example. In convection, it does not matter whether you are a small peptide, like beta amyloid, that’s about 4 kilo dalton, versus a larger waste product, as tau, that is 10 times larger or 40 kilo dalton, because these proteins would flow with the same velocity as the fluid flow.” — Maiken Nedergaard, The Physiological Society (2018).

Nedergaard's research suggests that this "brain bath" is vital for clearing protein waste. The study indicated that amyloid beta, a protein associated with Alzheimer's disease, is eliminated more efficiently during sleep. Subsequent experiments have further corroborated this hypothesis.

This brain-cleansing mechanism mirrors the lymphatic system in the body. Glial cells, particularly astrocytic endfeet enveloping the majority of brain vasculature, play a significant role in regulating this process through aquaporin 4 water channels. Nedergaard has termed this the glymphatic system.

Before this discovery, it was thought that the brain could only eliminate debris through cellular degradation processes, such as autophagy. However, not all waste is cleared effectively.

The glymphatic system acts as the mechanism to reset this cycle, akin to how sand becomes trapped in Eureka Valley.

Energy Dynamics in Geology and Consciousness

Geological cycles hinge on energy transfer. A rock perched on a mountain possesses substantial potential energy, both gravitationally and chemically. Following the forces of wind, rain, rivers, and oceans, this energy is eventually expended.

In the case of sand reaching the ocean, these small rocks are ultimately recycled into new rock formations. Conversely, the sand in Eureka Valley remains for an extended period, yet it too will eventually face a flood that allows for recycling. Once the cycle concludes, the potential energy of the rock is rejuvenated.

I contend that the mechanisms underlying consciousness also rely on the interplay between potential and kinetic energy. Nedergaard's findings suggest that while our consciousness is inactive, the glymphatic system rejuvenates our brain. Her research has primarily focused on the mechanisms facilitating this process and the clearance of proteins related to neurodegenerative diseases. However, various waste products accumulate in the brain.

I propose that the glymphatic system restores the brain to a state of optimal potential energy. Throughout our waking hours, this potential energy diminishes as metabolites are utilized, and neurons signal to each other, releasing ions and proteins into the extracellular space—similar to how mountains erode into sand.

Interestingly, recent findings from Nedergaard's lab indicate that lactate, a byproduct of glucose metabolism, is also cleared through the glymphatic system. What other substances could this system remove? Neuromodulators, neurotransmitters, ions, and signaling molecules trapped in the extracellular matrix are all possibilities ripe for exploration.

To comprehend how the fundamental components of consciousness are utilized and recycled, we must investigate what transpires in the spaces between neurons—the brain's extracellular environment.

This is an exhilarating era for researching the diffusion and convection of various molecules within the brain's extracellular space. Laboratories worldwide are now acquiring the necessary technologies to explore these inquiries in living organisms and humans.

Some intriguing questions to consider might include: - What materials store the potential energy essential for consciousness generation? - What forms of kinetic energy contribute to the emergence of consciousness? - How does the breakdown of identified raw materials affect that energy? - In what ways is potential energy replenished in the system?

The Phenomenon of Singing Sand

Though the sand at Eureka Dunes is immobilized, it is in a state of constant change. Eureka Dunes ranks among 40 recognized "booming" dunes. During the summer heat, the top layer of dry sand sometimes cascades down the dune's slip face. This avalanche produces an audible sound that persists for several minutes after the event. The booming resembles musical notes, characterized by a dominant frequency accompanied by harmonics, akin to the vibration of a plucked cello string. The prevalent dominant frequency is around 85 Hz (+/- 4 Hz), corresponding to either the musical notes E or F.

> “Where the music is heard in circumstances which admit of no mechanical or artificial causation, the wind is capable by itself of playing upon the chords, and producing the vibration that is necessary for the manufacture of the sound.” — Curzon (1923).

According to Melany Hunt, the booming sound arises from the dunes' non-uniform structure. The interior is compacted and damp, while the surface layer is loose and dry. An impact on the top layer generates an acoustic pulse that triggers a wave. Acoustic waves become trapped between the air and the damp interior, functioning as a waveguide that amplifies the sound. The booming occurs only when sufficient energy is provided, which an avalanche supplies. The gravitational energy of cascading sand transforms into kinetic energy, enhancing the acoustic waves through constructive interference. If conditions align such that the threshold for booming frequency is reached, some energy escapes into the atmosphere as sound.

Hunt has expanded on this concept by developing a mathematical model to describe the phenomenon. See her works, “The waveguide theory for booming sand dunes” and “Linear and nonlinear wave propagation in booming sand dunes.”

The sound emitted by the dunes can be regarded as an emergent property, as it results from the collective behavior of the system. A single grain of sand cannot produce sound, but the combined vibrational energy of many grains can.

Consciousness as an Emergent Property

Many neuroscientists and philosophers investigating consciousness posit that it too is an emergent property. However, what constitutes consciousness? At what level can it be discerned? What energy propels it, and what type of energy transformation occurs to manifest consciousness? These questions remain unanswered.

One prevalent theory suggests that synchronization of brain oscillations across different regions generates consciousness. Of particular interest is the synchronization of thalamocortical networks, which consist of bidirectional connections between neurons in the thalamus and cortex, each specialized for processing distinct information.

Brain oscillations, or brain waves, can be observed when monitoring the activity of large groups of neurons simultaneously. These neuron populations oscillate between states of high activity (elevated likelihood of firing) and low activity (decreased likelihood of firing), creating rhythmic patterns. Brain oscillations occur at specific resonant frequencies, and significant research has focused on the functional implications of various frequency bands.

In thalamocortical networks, the high-frequency gamma band (typically around 40 Hz, but ranging from 25 to 100 Hz) has garnered interest, as gamma oscillations synchronize during challenging cognitive tasks. It is believed that constructive interference between these synchronous waves amplifies signals.

For years, brain oscillations were dismissed as mere background noise. However, it has become evident that a certain level of oscillatory activity is necessary for perceiving incoming stimuli, although this remains a topic of debate. For more insight, refer to the review article, “Neural oscillations and the initiation of voluntary movement.”

If my assertions hold, these oscillations can be likened to the avalanche, essential for generating the energy required to produce the emergent property of consciousness.

The Brain as a Sand Dune

The brain is a remarkably intricate structure. Ongoing efforts aim to catalog specialized cell types in the brain, serving as a foundation for understanding their collaborative functions (see the Allen Brain Atlas). There is a vast diversity of cell types, and even within them, individual variations abound. As a molecular and cellular neuroscientist, I have always perceived the brain this way. It is captivating and significant, but what if we considered the brain from a different perspective—one akin to a sand dune?

Now, for a bit of philosophical speculation. The following thoughts are not definitive truths but rather an invitation to explore a new framework for understanding consciousness.

Could the brain possess a straightforward internal structure that elucidates consciousness, similar to the damp sand beneath the dry surface? Damp sand is denser, while the dry sand above is more fluid and free to vibrate. Is the brain analogous?

To begin, let’s examine the fundamental architecture of a neuron. Neurons feature a cell body with a branched process called a dendrite and a singular unbranched process known as an axon. Dendrites resemble filter feeders in the ocean, capturing various neurochemical signals present in the extracellular fluid. Axons, in contrast, function like extension cords, essential for transmitting signals over long distances. Axons that relay signals to the same destination group into nerve bundles, or axon tracts, which terminate at specific brain regions or peripheral locations.

I find myself pondering an intriguing question—does the propagation of an action potential along the axon induce a physical vibration?

Action potentials indeed travel along the axon like waves. The influx of ions alters the osmolarity within the cell, potentially causing extracellular fluid to rush in and slightly swell the axon. This notion isn’t far-fetched. However, as most axons are insulated with myelin, they exchange ions with the extracellular space solely at small gaps known as the nodes of Ranvier. Still, myelin can be likened to a water balloon rich in lipids and proteins. If the axon swells or vibrates at these nodes, might this effect be amplified by such a structure?

The energy generated by even minor movements could be further amplified if multiple axons within a nerve bundle fire simultaneously. Is there a sensitive capacitive displacement sensor capable of detecting these subtle vibrations? How might we measure other forms of energy produced during the coordinated activity of axons within a nerve bundle?

Could the axon tracts be likened to a cello string, with consciousness representing the audible note?

Taking a broader view, a relatively new imaging technique known as diffusion tensor imaging specifically visualizes axon tract structures in the brain. Examining these images with the notion of energy traveling through wet and dry sand, I observe a few notable features (see for yourself).

First, many major tracts within the brain’s interior do not follow straight paths; they curve. This may be due to their surrounding gray matter structures, or perhaps this configuration provides advantages for nerve transmission.

The bilateral symmetry of the brain is remarkable. Some curving tracts nearly form circles or egg shapes when viewed in both hemispheres. The thalamic radiations, in particular, are stunning. While it’s tempting to envision the synchronous activity of layered, circular axon tracts as an electromagnetic coil, I don’t believe this is the case.

Second, the interior brain tracts are typically dense, tightly packed bundles, whereas the thin tracts extending outward into the cortex resemble a koosh ball.

Similar to a sand dune, axon tracts consist of a densely packed core with a relatively spacious outer layer. It seems plausible that these thin tracts, dispersed in a grid-like pattern throughout the cortex, exhibit distinct physical properties and may transfer energy to surrounding tissue in unique ways.

And that concludes my reflections for today. I invite you to continue this exploration. The hope in juxtaposing the brain with a sand dune is to inspire innovative ways of conceptualizing brain function. Please feel free to critique this post and share what I may have overlooked.