Source
- Damasio & Damasio (2022), Homeostatic feelings and the biology of consciousness, LIT-628, in NOTE-507 (Skimmed): every section, Table 1 and the references, but through a fetch tool that returned section-by-section accounts, not the text. Nothing below quotes it; the essay is paraphrased, and cited by section heading.
- Damasio & Carvalho (2013), The nature of feelings, LIT-388, read in NOTE-330: the section on the neural substrates of feeling (C4–C5) and the cellular proposal (C7).
What was actually shown
Nothing was shown in the experimental sense. The essay argues from a definition, an anatomical contrast and cited clinical observations; the 2013 review argues from lesion cases. What each contributes:
The identification. Damasio & Damasio (LIT-628, “Consciousness”) define consciousness as the spontaneous identification of what is perceived, recalled and thought as belonging to a particular owner, the organism in its body. They set this against the mere integration of images, the scale of that integration and attention to some images over others, which they say it should not be confused with.
Feelings supply it. On their hypothesis (“How is consciousness made”), the continuous flow of homeostatic feelings, salient ones such as hunger, thirst, pain, well-being and malaise and near-equilibrium ones they call feelings of existence, provides the identification of a mind with its organism. Above a threshold, such feelings are generated continuously while awake. Each is conscious of itself, not by borrowing consciousness from another process, and they confer consciousness on exteroceptive images: visual cortex builds the maps, but for those images to be conscious, the essay proposes, feelings must be present as well. Self-consciousness is a later step, when perceptions, memories and reasoning are connected to the organism and its history.
Why feelings can do this: the hybrid. Exteroceptive maps cannot interact with what they map; a map of a landscape does not touch the landscape. Interoceptive ones can. Table 1 of the essay contrasts the two kinds of pathway: interoceptive axons poorly or not myelinated (Aδ and C), non-synaptic as well as synaptic transmission, time scales of seconds to hours as well as fast ones, a blood–brain barrier absent or with large gaps, monoamines, acetylcholine and neuropeptides; exteroceptive, movement and cognitive pathways well myelinated, predominantly synaptic, very fast, behind a continuous barrier, using glutamate and GABA. So viscera and circulating molecules can reach the neurons that map them, and the brain can act back on the source. Map and object interact, and the authors call the resulting feeling a hybrid of body and neural map (“How do living organisms generate homeostatic feelings?”). Damasio & Carvalho (LIT-388) had proposed the cellular half nine years earlier, as speculation: that feeling begins in unmyelinated interoceptive fibres open to ions and ligands along their length (C7 in NOTE-330).
Where it is lost. The essay places the first integration of body signals in the posterior upper brainstem (nucleus tractus solitarius, parabrachial nucleus, periaqueductal grey), and says that small lesions there abolish consciousness, by compromising integrated body representations and severing their links to exteroceptive contents, while even extensive cortical lesions may not (“Impaired consciousness”, citing Parvizi and Damasio 2001 and 2003). Damasio & Carvalho (LIT-388) give the lesion pattern first-hand from the literature they review: damage to the posterior half of the upper brainstem gives coma or a vegetative state in which feeling and sentience are abolished, and damage to the ventral half gives locked-in syndrome with feeling spared (C5 in NOTE-330). The essay adds that general anaesthetics act at the membrane-level sensing below feeling, suspending interoception and exteroception together.
What could have come out otherwise: the lesions that abolish consciousness could have been cortical while brainstem lesions spared it, or the interoceptive pathways could have been built like the exteroceptive ones. Neither is the case as the sources report it. Neither outcome tests the identification itself.
What this does not say
- It does not show that feelings make contents conscious. The identification is a definition, and the lending claim is argued from it (C1–C2 in NOTE-507, a definition and weak). A theory of access or of integration is not refuted by being told consciousness is something else (NOTE-507, Limitations).
- Coma and anaesthesia do not discriminate. Brainstem lesions and anaesthetics abolish arousal and every cortical process downstream, so their effects are what every theory predicts. The plant evidence shows that anaesthetics act on membranes, not where in an animal their effect on consciousness lies.
- The hybrid is an interpretation. The anatomy of Table 1 is cited (to Carvalho and Damasio 2021) with no numbers, and that the anatomy makes feeling partly constituted by the body is the authors’ reading of it (C4–C5 in NOTE-507). In 2013 the cellular link was “we propose”.
- It is not checked against the text. The essay was reached only through a fetch tool that would not reproduce it, so every detail here is as that tool returned it, and the essay is held Skimmed.
- It does not include the evolutionary claim. The essay also holds that homeostatic feelings were the first conscious phenomena, selected because they let life regulation be guided overtly. That is an adaptive story with no comparative evidence (C3 in NOTE-507) and is left out of this account.
It extends THEORY-045
THEORY-045 holds that felt affect is the experience of the body’s
regulatory state, present throughout waking experience, and it leaves
open whether what is felt is a prediction of that state or a map of it.
It explicitly does not claim that consciousness is grounded in feeling.
This account builds on it in two ways. It widens it: the same felt body
state is what makes any content conscious, not only what affect is. And
it refines the open question with a reading THEORY-045 does not list:
neither a prediction nor only a map, but a feeling partly constituted by
the body state it maps. Damasio & Carvalho (LIT-388) are a source of both
accounts. The essay supports THEORY-045’s “throughout waking experience”
clause with its feelings of existence, continuous while awake. It says
nothing about prediction, so it does not decide against Barrett’s version
(LIT-542); it adds a third option. It is a widening of the same
mechanism, not a rival, so the relation is extends.
It rivals THEORY-096
The global-availability account holds that a content becomes conscious when it ignites a core of long-range cortical hub neurons and is broadcast, and it takes global availability to be what is experienced. This account holds that a content becomes conscious when homeostatic feeling identifies it as the organism’s own, and the essay sets consciousness apart from the attention given to some images over others and from integration, naming Dehaene’s account among those that study such mechanisms in place of consciousness (“The problem of consciousness”). The two give incompatible answers to what makes a content conscious, and incompatible answers about what is lost when it is lost. The workspace review (LIT-631) ties the level of consciousness to frontal-parietal hubs and argues that anaesthetics of different molecular classes share a disconnection of that network. The essay puts the critical site in the posterior brainstem, says extensive cortical lesions may spare consciousness, and puts the anaesthetics’ action at membrane-level sensing below feeling. Neither tests the other; the essay never engages the workspace’s evidence and the review never mentions interoception. The rivalry holds only on the reading of the workspace that identifies experience with availability, which is the reading that account states; read as a theory of access alone, it would answer a different question.
Connections
- THEORY-090 (subcortical alarm consciousness) shares the subcortical clause: a basic affective consciousness realised in the upper brainstem and thalamus, sourced partly from LIT-388 as this account is. The essay adds the clinical form for consciousness itself. It does not take a side on that account’s function clause (alarm, without choice) or its rival’s (THEORY-101, valence as a common currency for trade-offs): its feelings are knowledge for overt regulation, and its examples are corrections, neither overrides nor trade-offs. No relation is declared: this account does not build on ALARM, and the two can both be right.
- IIT (LIT-445). The essay names integration of information among the mechanisms that are not consciousness, and denies consciousness to inanimate objects however complex; LIT-628 declares the rivalry at the level of the works. No theory in the record states IIT.
- The self-model (THEORY-064). Metzinger likens the transparent self-model to Damasio’s core self and anchors it in continuous internal input. On this account ownership of contents comes first and self-consciousness after; the two agree that a felt sense of one’s own body is what contents are referred to, and differ on whether a model or a hybrid feeling does it. Not declared.
- AI consciousness (THEORY-023). The essay concludes that consciousness needs a partnership of a nervous system with the body it serves and is absent from inanimate objects of any complexity. On this account a system with no body whose state can act on its own maps has no consciousness, which is the biological side of the deadlock that account describes, stated without an argument the other side would accept.