Cold Water and the Brain - Oxygenation, cold and the awareness of limits

(Consciousness in First Person • Decolonial Neuroscience • Brain Bee • The Feeling and Knowing Taá)

The Feeling and Knowing Taá — entering the cold

I imagine my body entering very cold water.
Before any theory, I feel:

• the sudden gasp of air,
  
  

• the micro-panic in my chest,
  
  

• the skin burning and then almost disappearing,
  
  

• my attention shrinking to “now” and “survive”.
  
  

In this instant, Taá is raw: my body knows before I can explain.
It knows that temperature is not just a number;
it is a negotiation between life, blood flow and oxygen.

I also notice something else: my language for this experience was colonized.
I was taught to talk about “resilience”, “mental toughness”, “biohacking”,
as if cold water were just a personal challenge and not also
a story about class, territory, climate and who tem o privilégio de escolher o desconforto.

When I feel first and think after — when Taá appears —
I notice there is no real separation between Neuroscience, Politics and Spirituality
(Spirituality here as Utupe, Xapiri, living memory, not as dogma).
The way we narrate cold water can legitimize extreme sports for a few
or honour the daily cold of workers, povos originários and periférico bodies
que nunca foram “consultados” sobre esse experimento climático.

Cada descoberta científica, se lida com coragem, abre uma fresta:
rompe um pedaço da Zona 3 (ideologias, consumo, “heroísmo” sem contexto)
e devolve o corpo ao que sempre foi: território vivo de limites, medo, coragem e cuidado.

The study: cold water immersion, cerebral oxygenation and survival responses

A recent 2025 peer-reviewed study on cold-water immersion, cerebral oxygenation and survival-type responses used fNIRS to monitor how the brain and body negotiate extreme cold in real time.

I will refer to it here as:

“Cold water immersion, prefrontal oxygenation and cardio-respiratory responses in humans”
(search terms: cold water immersion cerebral oxygenation fNIRS prefrontal 2025)

The core scientific question is simple and powerful:

What happens to prefrontal cortex oxygenation and systemic physiology
when the body is suddenly exposed to very cold water,
and how does the brain manage the limit between adaptation and collapse?

For Brain Bee readers: it is like asking
“how far can my brain play with cold before my biology says enough?”

Methods and analysis — how the signals were read

Participants immersed (or had limbs immersed) in very cold water
while researchers recorded:

• fNIRS signals (changes in O₂-Hb and HHb) over prefrontal cortex,
  
  

• heart rate and blood pressure,
  
  

• breathing pattern,
  
  

• sometimes skin temperature and subjective discomfort.
  
  

On the analysis side, the pipeline followed the modern BrainLatam2026 standard:

• GLM (General Linear Model)
  
  

• modelling the task blocks of cold exposure vs baseline;
  
  

• estimating how much the hemodynamic response changes during immersion.
  
  

• Short-channels
  
  

• separating superficial scalp blood flow from deeper cortical signals;
  
  

• reducing the contamination by systemic vasoconstriction in skin vessels.
  
  

• HRF modelling
  
  

• allowing the Hemodynamic Response Function to adapt to slower or faster responses
  (cold changes vascular dynamics, so the HRF cannot be naive).
  
  

• ICA / PCA
  
  

• ICA to remove components clearly dominated by motion or heart beat;
  
  

• PCA to identify global trends (e.g. a big systemic drop in O₂-Hb)
  and focus on meaningful variance.
  
  

In some protocols, the analysis also leveraged multi-channel GLM
to see patterns across regions rather than only electrode-by-electrode.

Main findings — the brain between alertness and protection

The results converge on a clear picture:

• Cold water immersion triggers a strong autonomic response
  (heart rate spikes, breathing changes, blood pressure adjustments).
  
  

• Prefrontal O₂-Hb may show:
  
  

• an initial dip (the shock, the gasp, the “what is happening?”),
  
  

• followed by recovery or overcompensation,
  
  

• or, in some individuals, a more prolonged reduction in oxygenation.
  
  

• The balance between oxygen supply and vasoconstriction is critical:
  
  

• too much constriction → protection of core temperature,
  
  

• but risk of reduced cortical perfusion.
  
  

• Individuals differ a lot. Some brains show:
  
  

• efficient recovery of prefrontal oxygenation and stable behavior;
  
  

• others show persistent dysregulation, more discomfort and cognitive impairment.
  
  

In short:

Cold water is a laboratory of limits.
It reveals how each body negotiates survival, clarity and confusion moment by moment.

Reading the study through our concepts

Damasian Mind and the edge of awareness

In Damasian terms, consciousness emerges from interoception + proprioception.
Cold water hits both at once:

• skin and viscera screaming “danger”,
  
  

• muscles tightening,
  
  

• breath oscillating.
  
  

The fNIRS signal is a trace of how this storm is being regulated.
When prefrontal oxygenation stabilizes, it is the Damasian Mind
finding a new dynamic balance in a harsh environment.

Quorum Sensing Humano (QSH)

No one enters cold water alone, even when physically alone.
There is always an imagined audience:

• coaches,
  
  

• friends,
  
  

• Instagram,
  
  

• expectations of “strength”.
  
  

QSH appears in the way social narratives push us to go “beyond the limit”,
sometimes against our interoceptive warnings.
The hemodynamic curve shows when the body obeys the ritual
and when it starts to resist.

Eus Tensionais and Zones 1 / 2 / 3

In Zone 1, I might act automatically: jump in, because “that’s the protocol.”
In Zone 2, I can feel the cold, respect it, calibrate time and depth —
I negotiate with the environment.
In Zone 3, ideology takes over:
“pain is weakness”, “if you quit you are nothing”,
and my Eu Tensonal becomes captive of an external script.

The study shows how Zone 3 can be dangerous:
pushing for more seconds or minutes when prefrontal oxygenation is clearly falling.

DANA — DNA as intelligence

DANA reminds me that my DNA did not evolve for TikTok challenges,
but for survival in varied climates.
The autonomic reflexes observed in the study —
peripheral vasoconstriction, respiratory drive, heart changes —
are DANA speaking: “I will keep you alive if you listen.”

Yãy hã mĩy (Maxakali, original meaning always mentioned)

Originally, Yãy hã mĩy (from the Maxakali people)
is the act of imitating and becoming the animal one wants to hunt.
In our extended sense, it is the process of becoming the state we train.

Cold-water practitioners, when conscious,
are doing a Yãy hã mĩy of survival physiology:
they rehearse controlled danger to expand their world.
The risk is when this becomes colonial spectacle instead of embodied wisdom.

Latin American art as mirror — Zé Ramalho and the inner ship

When I think of this article, a Latin American voice comes to me:
Zé Ramalho – “A Nave Interior”.

Cold water immersion can be read as this inner ship:
a journey into the most primitive layers of the body,
where fear, courage and limit are renegotiated.

Instead of seeing only “biohacking” in the North Atlantic style,
we can hear the song as a reminder:

• every physiological protocol is also a spiritual and political crossing;
  
  

• the question is: who is steering the ship —
  DANA and Taá, or the market of performance?
  
  

Avatares Referências — which lens helps most here?

For this study, I feel strongly guided by the Math/Hep avatar
(our reference for energy, metabolism and quantitative relations):

• cold as energetic constraint,
  
  

• oxygenation as currency,
  
  

• limits as nonlinear thresholds rather than simple “willpower”.
  
  

Alongside Math/Hep, DANA quietly holds the helm:
the DNA-level intelligence that, long before any protocol,
designed these emergency responses to keep bodies alive
em rios gelados, mares, tempestades.

I don’t need to name the avatars as a separate block;
I let them act as lenses while I read and reinterpret the curves.

Normative implications for LATAM

If we take this seriously for Latin America:

• Occupational health
  
  

• river workers, fishers, people em regiões frias ou de altitude
  need protocols guided by fNIRS-type knowledge,
  not only by imported “resilience” slogans.
  
  

• Sports and rehabilitation
  
  

• cold-water training should respect individual variability in oxygenation,
  not apply the same time and temperatures for all.
  
  

• Climate emergency
  
  

• extreme cold and heat waves both reshape cerebral oxygenation;
  
  

• our policies must consider the nervous system,
  not just “economic activity” and “infrastructure”.
  
  

• Decolonial neuroscience
  
  

• studies like this can move from “heroic exposure” narratives
  to conversations com povos originários sobre corpo, clima e limites,
  integrando saberes ancestrais de água, rio e frio.
  
  

Keywords for scientific search

“cold water immersion cerebral oxygenation prefrontal fNIRS 2025 autonomic responses hemodynamic GLM short channels HRF variability”

When Two Brains Receive the Same World - Cooperation, synchrony, and the shared rhythm of attention

Embodied Singing -Voice, interoception, and Body-Territory in vocal expertise

Pleasant Odors and the Breath that Organizes Us - How smell organizes brain–body coupling

Architecture That Thinks With Me - Turning corners and the attentional cost of built environments

Auditory Approach Bias From Birth - How newborns and adults code the desire to listen

Beta Waves and the Moment I Truly Decide - The prefrontal cortex as the space where "feeling" becomes "choosing"

How My Brain Encodes Voice in Midlife - F0, listening effort, and the vitality of human hearing

Learning Beside Another Brain - Hyperscanning and the pedagogy of co-presence

Reproducibility in fNIRS - When can I trust the hemodynamic curve I see?

HRfunc and the True Shape of the Hemodynamic Response - Why every brain breathes light in its own way

Mixed Reality and Decision-Making - How the brain evaluates prototypes and hybrid worlds

Intense Exercise and the Awakening of Zone 2 - The hemodynamics of effort and the body that generates intelligence

Buttoning a Shirt - Everyday actions as windows into attention, gesture, and consciousness

Depression, tDCS, and the Prefrontal Cortex - Reigniting silent circuits

Designing fNIRS Studies in Real-World Environments - Why science must step outside the laboratory to exist

Transformers and Virtual Short-Channels - AI cleaning brain signals and retelling hemodynamics

Mental Fatigue and Performance - When the head gives up before the body

Cold Water and the Brain - Oxygenation, cold, and the consciousness of the limit

Walking After Stroke - Cognitive–motor interference in everyday life

Balance and the Cerebellum in Parkinson’s Disease - Movement, tensions, and reorganization of the Body-Territory

Freezing of Gait and the Loss of the Body’s Own Quorum - When the body stops trusting the next step

Children With Cochlear Implants - Learning to hear through the brain, not just the device

Emotional Processing in Children With Oppositional Behavior - Regulation, conflict, and the birth of Tensional Selves

Mild Cognitive Impairment - Early hemodynamic signs and presence in the world

Pain, Apathy, and Depression in Dementia - When feeling and thinking stop walking together

Cognitive Load - How much does fNIRS really feel my mental effort?

The Brain in Daily Life -Assisted horsemanship, sport, and embodied enjoyment

Linguistic Jiwasa - When language thinks the world

Dialogical Multiplication and Indigenous Psychology - How to let psychology listen without erasing the Other

The Feeling and Knowing Taá of Christmas 

Republican Capitalism of Spirits without Bodies

NIRS fNIRS EEG ERP Multimodal NIRS-EEG

#Decolonial
#Neuroscience
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#Multimodal
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#Jiwasa
#Taa
#CBDCdeVarejo
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