Comment on the article “Spatially-extended nucleation-aggregation-fragmentation models for the dynamics of prion-like neurodegenerative protein-spreading in the brain and its connectome 486 (2020) 110102”

AbstractThe prion-like hypothesis of neurodegenerative diseases states that the accumulation of misfolded proteins in the form of aggregates is responsible for tissue death and its associated neurodegenerative pathology and cognitive decline. Some disease-specific misfolded proteins can interact with healthy proteins to form long chains that are transported through the brain along axonal pathways. Since aggregates of different sizes have different transport properties and toxicity, it is important to follow independently their evolution in space and time. Here, we model the spreading and propagation of aggregates of misfolded proteins in the brain using the general Smoluchowski theory of nucleation, aggregation, and fragmentation. The transport processes considered here are either anisotropic diffusion along axonal bundles or discrete Laplacian transport along a network. In particular, we model the spreading and aggregation of both amyloid-β and τ molecules in the brain connectome. We show that these two models lead to different size distributions and different propagation along the network. A detailed analysis of these two models reveals the existence of four different stages with different dynamics and invasive properties.

Download Full-text

Brain World or Life World? Critique of Neuroconstructivism

10.1093/oso/9780192898197.003.0007 ◽

2021 ◽

pp. 144-156

Author(s):

Thomas Fuchs

Keyword(s):

External World ◽

Point Of View ◽

Phantom Limb ◽

Rubber Hand ◽

Life World ◽

Body Experience ◽

The World ◽

Spatially Extended ◽

The Subject ◽

The Brain

From a neuro-constructivistic point of view, the brain creates an internal simulation of the external world which appears as the phenomenal world in consciousness. This view presupposes in particular that the subjective body and the organic or objective body belong to two fundamentally different worlds, the mental and the physical. The spatiality of the subject-body must then be declared an illusion, for example by referring to dissociations of the subject- and object-body as in the rubber hand illusion or the phantom limb. However, this alleged virtuality of body experience can be refuted by the intersubjectivity of perception, which confirms the co-extensivity of subject-body and object-body. Subjectivity thus proves to be as embodied as it is spatially extended, that means, as bodily being-in-the-world.

Download Full-text

Is the world in the brain, or the brain in the world?

Behavioral and Brain Sciences ◽

10.1017/s0140525x03420098 ◽

2003 ◽

Vol 26 (4) ◽

pp. 427-429 ◽

Cited By ~ 1

Author(s):

Max Velmans

Keyword(s):

Phenomenal World ◽

The World ◽

Spatially Extended ◽

The Brain

Lehar provides useful insights into spatially extended phenomenology that may have major consequences for neuroscience. However, Lehar's biological naturalism leads to counterintuitive conclusions, and he does not give an accurate account of preceding and competing work. This commentary compares Lehar's analysis with that of Velmans, which addresses similar issues but draws opposite conclusions. Lehar argues that the phenomenal world is in the brain and concludes that the physical skull is beyond the phenomenal world. Velmans argues that the brain is in the phenomenal world and concludes that the physical skull is where it seems to be.

Download Full-text