Communicated by Terrence Sejnowski - Ricerca sull'intelligenza artificiale specializzata al MIT

Communicated by Terrence Sejnowski

Feelings Are the Source of Consciousness

Antonio Damasio
damasio@usc.edu
Hanna Damasio
hdamasio@usc.edu
Brain and Creativity Institute, Dornsife College of Letters, Arts and Sciences,
University of Southern California, Los Angeles, CA 90089-2921, U.S.A.

In this view, we address the problem of consciousness, and although we
focus on its human presentation, we note that the phenomenon is present
in numerous nonhuman species and use findings from a variety of animal
studies to explain our hypothesis for how consciousness is made.

Consciousness occurs when mind contents, such as perceptions
and thoughts, are spontaneously identified as belonging to a specific
organism/owner. Conscious minds are said to have a self that experiences
mental events. We hypothesize that the automatic identification that as-
sociates minds and organisms is provided by a continuous flow of home-
ostatic feelings. Those feelings arise from the uninterrupted process of
life regulation and correspond to both salient physiological fluctuations
such as hunger, pain, well-being, or malaise, as well as to states closer to
metabolic equilibrium and best described as feelings of life/existence,
such as breathing or body temperature. We also hypothesize that
homeostatic feelings were the inaugural phenomena of consciousness
in biological evolution and venture that they were selected because the
information they provided regarding the current state of life regula-
tion conferred extraordinary advantages to the organisms so endowed.
The “knowledge” carried by conscious homeostatic feelings provided
“overt” guidance for life regulation, an advance over the covert regu-
lation present in nonconscious organisms. Finalmente, we outline a mech-
anism for the generation of feelings based on a two-way interaction
between interoceptive components of the nervous system and a particular
set of nonneural components of the organism’s interior, namely, viscera
and circulating chemical molecules involved in their operations. Feelings
emerge from this interaction as continuous and hybrid phenomena, Rif-
lated simultaneously to two series of events. The first is best described
by the terms neural/representational/and mental and the second by the
terms nonneural/visceral/and chemical. We note that this account offers a
solution for the mind-body problem: homeostatic feelings constitute the
“mental” version of bodily processes.

Calcolo neurale 35, 277–286 (2023)
https://doi.org/10.1162/neco_a_01521

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1 What Consciousness Is and How Feelings Contribute to It

The problem of consciousness—what it is, how it is produced, where and
how it operates—continues to attract the attention of biologists, physicists,
and philosophers. The treatment of the problem remains controversial, E
to date, no solution has generated consensus (Baars, 1988; Crick & Koch,
1990; Chalmers, 1995; Dehaene & Changeux, 2011; Tononi, 2012; Seth & Fris-
ton, 2016; Solms & Friston, 2018). One might even venture that the situation
has worsened and that the lack of acceptance of biological treatments of the
problem has led to the idea that the solution might actually be found in the
realm of physics (Goff, 2019).

A major problem facing consciousness studies is the clarification of what
consciousness is and what it achieves. The multiplicity of meanings of the
term makes a comparison of proposed solutions and alleged failures diffi-
cult at best. It is apparent, Per esempio, that the term consciousness is often
used to signify mind and that the purpose of some alleged consciousness
studies is to elucidate processes behind complex mentation such as atten-
tion and integration of information.

And yet from our perspective, we believe that what consciousness pri-
marily achieves is distinct and unique. Consciousness identifies mental con-
tents as belonging to a specific organism and vice versa; it connects a mind with
its respective body and establishes mutual ownership. To be conscious consists
of experiencing a correspondence between mental contents and a specific
living organism.

In the normal awake state, the identification and connection happen au-
tomatically, not as a result of overt reasoning. We hypothesize that for rea-
sons we explain later, homeostatic feelings naturally provide the revealing
link between (1) events occurring in the “body” component of the part-
nership and (2) events experienced as occurring in the “mind” (Damasio,
2021UN, 2021B; Carvalho & Damasio, 2021; Damasio & Damasio, 2022). Noi
note that the spontaneous conscious nature of homeostatic feelings is the
consequence of physiological conditions that we describe in section 5.

This hypothesis results from placing some established facts in a novel
perspective. The first fact is that homeostatic feelings are spontaneously
conscious mental events. If homeostatic feelings were not conscious to be-
gin with, they would not have been useful from the standpoint of life
regulation. We also suggest that if feelings had not been conscious, Essi
would not have become selected features of life regulation in complex living
organisms.

The second fact is that homeostatic feelings continuously express, mo-
ment by moment, the overall process of life regulation within the respective
organisms: prominent needs (hunger, thirst), alarm signals (pain, fever), op-
portunities for exploration (well-being). In healthy conditions, feelings tend
to hover near homeostatic equilibrium, express the continuity of life, E
signify existence. Feelings exhibit qualities that correspond to degrees of

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Feelings Are the Source of Consciousness

279

homeostatic efficiency (per esempio., pleasant, painful, neutro), as well as to varied
intensities. Because feelings occur continuously, they provide an equally
continuous mental translation for the dynamics of the organism in which
they occur.

In brief, we hypothesize that (1) homeostatic feelings inaugurated con-
sciousness in biological evolution and that (2) they were selected because
their spontaneous conscious nature enabled an evolutionary novelty: UN
strategy of life regulation based on overt information regarding the current state of
life in an organism. In other words, life regulation became grounded on the
“knowledge” provided by continuous homeostatic feelings, a novel cogni-
tive step generated by an affective process.

We also note that prior to the advent of homeostatic feelings, in uni-
cellular organisms as well as in relatively simple multicellular ones, con-
out nervous systems, homeostasis was maintained by covert mechanisms
only, relying exclusively on intelligent but nonconscious processes (Dama-
sio, 2018). After the advent of nervous systems and the appearance of feel-
ing, homeostasis also came to rely on the overt knowledge provided by
felt experiences. These experiences could operate as incentives or disincen-
tives relative to covert action goals and, eventually, as organisms became
more complex, draw on basic reasoning and deliberation to create novel re-
sponsorizzato. In sum, the arrival of feelings in evolution marked the beginning
of a dual strategy for life regulation, now dependent on a flexible combina-
tion of covert and overt mechanisms operating as needed to best maintain
homeostasis.

2 Distinguishing Consciousness from the Process of Sensing

and Detecting

Long before living organisms were capable of consciousness, they had the
possibility of sensing the conditions of their environment (which included
other organisms) and responding accordingly. This ability to sense/detect
is present in prokaryotes and even in plants. The sensing organism does not
need to have a nervous system and does not need to generate internal rep-
resentations of what is sensed or detected. In other words, simpler sensing
organisms do not need to create maps and images. We suggest that this is
manifestly different from what happens in organisms with consciousness,
a process that depends on mapped images generated by nervous systems
and where these images come to constitute minds. Sensing/detecting de-
pends on the physiology of cell membranes; still, it should be noted that its
simpler machinery is likely to be the foundation for the chain of processes
that eventually culminate in consciousness.

In between sensing/detecting and consciousness, we find the process
that we call minding. Minding consists of generating streams of sensory rep-
resentations, usually referred to as images, which require a nervous system
for their creation and display.

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UN. Damasio and H. Damasio

In essence, the images that constitute minds are of three kinds. The domi-
nant kind represents the world that surrounds each organism and includes
other living organisms and all varieties of objects and physical structures
and their interactions. These images are based on exteroceptive processes
such as vision, hearing, touch, smell, and taste. They correspond to an ex-
traordinary repertoire of objects and actions arising from the world external
to living organisms.

The second kind of images is less dominant but no less important. These
images are obtained via interoceptive channels and contribute to homeostatic
feelings. These images represent aspects of viscera and visceral states, come
as the heartbeat, the flow of air when one breathes, a gut colic, the contrac-
tion or dilation of blood vessels in the skin. They map intensity and quality,
pleasant or unpleasant, of what is being perceived. But as we explain in
section 3 and contrary to the way in which they are usually referred to, In-
teroceptive images are not mere perceptions.

A third perceptual channel represents muscular and skeletal structures
and the movements they execute. This channel, known as proprioceptive, also
contributes to homeostatic feelings but to a far lesser degree.

3 Explaining Consciousness

The essence of consciousness is the identification of a particular mind with
a particular organism. This “knowledge” is provided by the continuous ex-
perience of homeostatic feelings generated by the ongoing process of life
regulation as the organism attempts to maintain operations in the homeo-
static range. These include salient feelings such as pain, as well as the subtle
feelings of existence that are generated continuously in the awake state.

When we feel pain or hunger or well-being, we are necessarily conscious
of each of those particular states. Each homeostatic feeling is itself sponta-
neously and automatically conscious. Our mind is offered important and
conscious information about how life is progressing inside the organism
and about what the organism needs. Based on that qualitative and graded
knowledge, we can respond accordingly by making helpful corrections; for
esempio, pain signals the possibility of tissue damage, while hunger sig-
nals the need for additional energy sources; well-being indicates that the
organism can engage in exploration. If feelings had not been spontaneously
conscious, they would not have been able to assist the process of curating
life.

It is likely that homeostatic feelings were the inaugural phenomena of
consciousness in evolution and that they were selected because the knowl-
edge was a major evolutionary advantage. The knowledge available to con-
scious homeostatic feelings made deliberate life regulation possible.

Homeostatic feelings are conscious inherently, and they make conscious-
ness possible for other sensory material, such as exteroceptive sensory

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281

images. But we can be conscious of those images only when the feelings
that they generate are also present. No additional mechanism is needed to
provide consciousness for large arrays of contents. Consciousness emerges
from the homeostatic feelings of the subjective owner as triggered by few
or many imagetic contents on any theme.

Consciousness cannot be found in inanimate objects, regardless of how
complex they may be. It is found instead in the minds of living organisms
capable of constructing sensory representations of components or states
of their own bodies. We propose that consciousness cannot be found in
organisms limited to sensing/detecting and not provided with nervous
systems.

Because nervous systems are necessary for true consciousness to emerge,
we caution against the idea that nervous systems would be solely respon-
sible for consciousness. Consciousness requires a partnership of nervous
systems with the bodies they serve. It does not depend on nervous systems
alone.

4 Generating Homeostatic Feelings

Attributing consciousness to homeostatic feelings might appear as a dis-
traction from the fundamental problem and leaving the mystery unad-
dressed. We believe, Tuttavia, that it is possible to address the question of
how living organisms generate homeostatic feelings: as the result of a two-
way interaction between the nervous system and nonneural components of
the organism (Damasio, 2021UN, 2021B; Carvalho & Damasio, 2021). Homeo-
static feelings are a novel kind of process that generally describes aspects of
visceral anatomy but also documents the qualities and intensity of the phe-
nomena that take place in viscera—for example, the duration and intensity
of pain localized to a particular sector. Feelings are not the consequence
of plain perceptual processes but rather the result of hybrid interactions
between neural and nonneural bodily events. The continuous representa-
tions of the state of the organism identify the living organism in which they
emerge, and let the mind know of their origin.

The physiological setting of interoception is distinct from that of extero-
ception and helps explain the nature of feelings. Whereas exteroception at-
tempts to produce detailed maps of structures and events occurring outside
the organism, interoception describes structures and events inside those or-
ganisms. Interoception allows nervous systems to produce mapped repre-
sentations of internal structures and events. Neural and chemical signals
travel from viscera to the brain and produce “imagetic” representations, Ma
the brain can respond to such signals. We find no equivalent to this process
in the world of exteroception. This particular physiological setting suggests
that the nature of the feeling imagery produced by interoception is different
from the exteroceptive variety.

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UN. Damasio and H. Damasio

Tavolo 1: Contrasting Interoceptive and Exteroceptive/Cognitive/Motor Struc-
tures.

Interoceptive Structures

Motor Structures

Exteroceptive/Cognitive/

Type of axon

Unmyelinated (Aδ/C) O
poorly myelinated

Mode of transmission
Timescale
Specific processes

Predominantly nonsynaptic
Mostly slow (sec/min/hours)
Interoception, feelings,

emozioni

Well myelinated (Aα/Aβ)

Predominantly synaptic
Very fast (μsec − millisec)
Fine perception, apprendimento

and memory, reasoning,
math, lingua

Blood-brain barrier
Main neural

Absent or with major gaps
Monoamines (dopamine,

Continuous
Glutamate, GABA

transmitters, neural
modulators

noradrenaline, serotonin),
ACh, neuropeptides

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Just as important, the neural elements responsible for interoceptive in-
teractions are also quite distinct. Per esempio, interoceptive axons are not
insulated by myelin and make frequent nonsynaptic contacts. Inoltre, In-
teroceptive neurons are not systematically protected by a blood-brain bar-
rier. The consequence of these physiological conditions is that components
of the body’s interior, such as viscera and circulating chemical molecules,
can have direct access to interoceptive neurons because of the protective
barriers provided by myelin and the blood-brain barrier are absent.

5 The Physiology of Interoception Is the Enabler of Consciousness

The core physiology behind interoception is quite different from the
paradigmatic exteroceptive physiologies behind visual, auditory, and tac-
tile perception, and even from proprioception (the perception of the
movements executed by striated muscles in the limbs and trunk). The inte-
roceptive processes behind homeostatic feelings and consciousness rely on
a merging and comingling of elements in nonneural body structures with
elements in neural structures capable of generating a novel class of hybrid
phenomena (Carvalho & Damasio, 2021). This is the origin of the “double
face” of feelings, which are “physical” processes and yet yield subjective
“mental experiences.”

The anatomical and physiological features responsible for the functional
novelties introduced by interoception are summarized in Table 1, dove noi
list some of the key differences between interoceptive and exteroceptive
processes relative to (1) types of axons, (2) mode of signal transmission,
(3) timescales, (4). absence or presence of blood-brain barrier, E (5) main
chemical molecules engaged in the process. The following sources were

Feelings Are the Source of Consciousness

283

used in compiling the supportive facts: Foley & DuBois, 1936; Hoffman
& Schnitzlein,1961; Friede & Samorajski, 1967; Lieberman, 1976; Mantyh,
1982; Vizi, Gyires, Somogyi, & Ungváry, 1983; Leslie, 1986; Prechtl & Pow-
ley, 1990; Amir & Devor, 1996; Syková & Chvátal, 2000; Bokil, Laaris, Blin-
der, Ennis, & Keller, 2001; Craig, 2002; Oh & Weinreich, 2002; Moalem,
Mulpuri, Damasio, & Spigelman, 2005; Syková, 2005; Lang & Grafe, 2007;
Jimenez-Andrade et al., 2008; Fields, 2011; Nieuwenhuys, 2012; Damasio &
Carvalho, 2013; Carvalho, Mulpuri, Damasio, & Spigelman, 2019; Arcilla &
Tadi, 2020; Stakenborg et al., 2020; Tsakiris & de Preester, 2020).

6 The Hard Obstacles in Consciousness Studies

We suggested that one reason that current solutions for the problem of con-
sciousness fail to generate consensus is the lack of agreement on the defini-
tion of consciousness itself. Yet another hurdle comes from the conventional
and virtually universal view of the problem, which calls for the nervous
system alone to provide the answer. That is a most unlikely prospect. Being
conscious is an inherently cooperative state, that connects a nervous system
and the mind process it generates, with a nonneural entity, the organism or
body, for short.

The unusual physiological features that enable feelings, and thus con-
sciousness, depend on the presence of a nervous system but not on an iso-
lated nervous system. Organisms without nervous systems, capable of taking
intelligent actions to regulate their lives but not able to represent such ac-
tions or their consequences, appear to be nonconscious. Their intelligences
are covert. But conscious organisms such as ours are remarkably different:
(1) they are able to represent in mind the actions they take as well as their
consequences, (2) they have feelings, E (3) they can overtly represent the
consequences of those feelings (Damasio, 2018).

In our proposal, the generation of homeostatic feelings relies on both
neural and bodily processes, specifically on features such as phylogeneti-
cally old neurons (Quale, thanks to poor or absent myelination are open
to nonsynaptic contacts and comingle the nonneural flesh with the ner-
vous system) and on the fact that the body and the brain compartments
of the organism cross-signal abundantly. Di conseguenza, although neural inte-
roceptive channels generate body representations within the central ner-
vous system, those representations are themselves the target of ongoing
body processes that can modulate them. The central nervous system can
react to the presence of those representations by altering the body states
that originated them and consequently altered their subsequent represen-
tations. Rather than merely perceiving the body, the brain participates in a
comprehensive dialogue with structures that harbor, surround, and support
the body. Of note, spinal cord and brainstem nuclei are far more involved
than the cerebral cortices in this dialogue (Parvizi & Damasio, 2001, 2003).

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Received January 4, 2022; accepted April 13, 2022.

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