Anosognosia and disorders of bodily unawareness

The wiki has a great deal on awareness of the body as a graded ability — accuracy, sensibility, metacognition, measured in healthy people by counting heartbeats or detecting resistances. It has had nothing on what happens when the capacity is destroyed. Jones, Ward & Critchley (2010) supply it, and the answer relocates a claim the wiki had placed elsewhere.

The syndromes

• Anosognosia for hemiplegia — the patient denies being paralysed. Predominantly right-hemisphere. A major neuropsychological disorder in its own right: recovery and rehabilitation frequently depend on whether it is present.
• Anosognosia for hemianaesthesia — the patient denies having lost tactile sensation.
• Somatoparaphrenia — the patient disowns the limb. In Cereda et al.’s (2002) case 4, a woman with a focal right posterior insular lesion experienced delusions of being touched by a stranger’s hand and regarded her own upper limb as a foreign body.

Bisiach et al.’s (1986) framing, which Jones et al. adopt: these are not deficits of motor or sensory perception per se but disturbances at “the highest level of organisation” of a given function. The patient’s arm does not work and they cannot feel it; what is additionally missing is the registration that this is so.

Why they belong on this wiki

Because the anatomy is the interoceptive anatomy, and it is the wrong end of it.

Karnath et al. (2005) used lesion-overlay plots across stroke patients with anosognosia for hemiplegia against a group matched for clinical and demographic variables, and found the posterior insula the structure most commonly damaged — present in half the anosognosic patients. Spinazzola et al. (2008) and Golay et al. (2008) add right posterior insula for agnosia for hemianaesthesia and for neglect respectively (see the Table 1 summary on jones-2010-insula-lesions).

The insular-cortex page, following Craig, assigns awareness to the anterior insula: the posterior insula maps objective bodily state, the anterior re-represents it as subjective feeling and, on the strong version, constitutes the moment of awareness itself. Jones et al. record that “some previous reviews imply that anosognosia for hemiplegia/hemianaesthesia are disorders of emotional awareness that reflect anterior insula damage” — and that the lesion evidence puts them posteriorly.

Three ways to take that, none settled by anything in this wiki:

1. These are not failures of feeling but of monitoring. Spinazzola et al.’s reading, endorsed here: anosognosia, somatoparaphrenia and neglect are domain-specific disorders of consciousness, in which damage disrupts the self-monitoring processes that normally regulate awareness of one’s physical and cognitive status. On this reading the insula is a comparator detecting mismatch between predicted and actual peripheral feedback — and posterior insula is where the actual feedback arrives, so that is where the comparison breaks. This is the reading Jones et al. prefer, and it is why the page is relevant to feedforward-vs-predictive-interoception: an unawareness syndrome caused by losing the afferent term, not the predictive one.
2. Craig’s localization of awareness is too far forward. The straightforward reading, and the one the review does not draw.
3. Neither, because the lesions are too big. The authors’ own caveat, and it is serious: increasing anosognosia severity goes with larger lesions, suggesting damage to or disconnection of a distributed fronto-parietal network rather than any one region. Karnath’s patients sustained damage to multiple structures. Cereda’s focal case is the counterweight — one patient. See lesion-symptom-mapping.

The link to body ownership, and an experiment nobody has run

Somatoparaphrenia is body ownership failing pathologically, and it lands on the same structure the healthy paradigm implicates: right posterior insula activates during the rubber-hand-illusion (Tsakiris et al. 2007), and during PET when observed movement corresponds to executed movement, with activity falling as the sense of controlling the movement is reduced (Farrer et al. 2003).

Jones et al. propose the obvious test and note it has not been done: are patients with posterior-insula lesions resistant to the rubber hand illusion, relative to other lesion groups? The prediction is not straightforward in either direction, which is what makes it worth running. On the precision-competition account the wiki holds from Tsakiris via Quigley et al., lower interoceptive precision means a self-model more easily captured by exteroceptive input — so destroying interoceptive cortex should make patients more susceptible, not less. Jones et al. expect resistance. The two predictions are opposite and the experiment is cheap.

Placement

The wiki’s other acquired interoceptive deficit is acquired alexithymia after insular lesion (via Bonaz et al. 2021) — losing access to one’s emotional states. Anosognosia is losing access to one’s bodily ones. They plausibly belong to one family and no source here puts them together; recorded as an open seam.

Held at one remove throughout: Karnath, Cereda, Spinazzola, Bisiach and Farrer are all cited via Jones et al. and none is in raw/.