Hierarchical Brain

An explanation of the human brain

First published 1st February 2024. This is version 1.5 published 2nd March 2024.
Three pages are not yet published: sleep, memory and an index.
Copyright © 2024 Email info@hierarchicalbrain.com

Warning - the conclusions of this website may be disturbing for some people without a stable mental disposition or with a religious conviction.

Efferent connections

Efferent connections (“efferent” meaning “conducting outwards”) is my term to describe the synapse connections between neurons that allows a flow of signals in the opposite direction from the direction of incoming data signals that are processed by the brain. The afferent processing (“afferent” meaning “conducting inwards”) of incoming sense data and data from processes within the brain is a hierarchical and recursive coincidence detection process that results in the creation of symbol schemas, but the same process also results in the creation of, or strengthening of, connections in the opposite direction, as shown in my afferent processing examples.

References For information on references, see structure of this website - references

  1. ^ Discovering the Brain - Ackerman 1992
    doi: 10.17226/1785 downloadable here or see GoogleScholar.
    Page 107: “A curious fact, as yet unexplained is that ...[in the primary visual cortex], a small number of cells project their axons backward, to the preceding stage. The function of this back projection, which allows cells to transmit signals back to the layer from which they came, has puzzled researchers for some time. Could this be some sort of cellular mechanism for checking the 'accuracy' of signals as each stage feeds into the next? At present, there are no major hypotheses directing investigations of the matter. But in the other direction - the main flow of signals from the retina to the visual cortex - scientific understanding has improved steadily over the past few decades.”
  2. ^ ^ On Intelligence and Google Book preview - On Intelligence - Jeff Hawkins with Sandra Blakeslee, St. Martin’s Press, New York 2004
    Page 25 in chapter 2 entitled “Neural networks”: “...for every fibre feeding information forward into the neocortex, there are ten fibres feeding information back toward the senses. Feedback dominates most connections throughout the neocortex as well. No one understood the precise role of this feedback, but it was clear from published research that it existed everywhere.”
    Pages 161-2 in chapter 6 entitled “How the cortex works” under the heading “Can feedback really do that?”: “We’ve known for decades that connections in the cortical hierarchy are reciprocal. If region A projects to regions B, then B projects to region A. There are often more axon fibres going backward than forward. But even though this description is widely accepted, the prevailing paradigm is that feedback plays a minor or 'modulatory' role in the brain.”
    (Unfortunately, this book does not give sources of information, although I have no reason to doubt these generalisations.)
  3. ^ Convergence and divergence in a neural architecture for recognition and memory - Meyer and Damasio 2009
    doi: 10.1016/j.tins.2009.04.002 No download available, but see GoogleScholar.
    Page 378, Box 1: “Reciprocal signaling in sensory systems has been firmly established and seems to be ubiquitous... In addition to top-down modulation, we propose another and very different role for backward projections: reconstruction of maps. Retro-activation does not simply modify bottom-up information that is already present in the early sensory cortices; rather, it uses information available in the association cortices and makes this information explicit by reconstructing maps in the early cortices. Retro-activation is not only at work during mental imagery, a process manifestly supported by top-down activation. Rather, backward signaling occurs incessantly during perception, when it permits the completion of maps resulting from bottom-up processing and the reconstruction of additional maps in early cortices not targeted by bottom-up signals. The retro-activated maps code various aspects of knowledge associated with the perceptual stimulus. It is the (more or less complete) reassembly of this knowledge base that permits recognition of the stimulus.”
    This article does list some uses of efferent connections, although using some different terminology - “reconstruction of maps” = “retro-activation” = reinstatement, “mental imagery” = imagination, and it also mentions perception.

Page last uploaded Sat Mar 2 02:55:43 2024 MST