A possible role for cholinergic neurons of the basal forebrain and pontomesencephalon in consciousness
David Bourget (Western Ontario)
David Chalmers (ANU, NYU)
Rafael De Clercq
Jack Alan Reynolds
Learn more about PhilPapers
Consciousness and Cognition 6 (4):574-596 (1997)
Excitation at widely dispersed loci in the cerebral cortex may represent a neural correlate of consciousness. Accordingly, each unique combination of excited neurons would determine the content of a conscious moment. This conceptualization would be strengthened if we could identify what orchestrates the various combinations of excited neurons. In the present paper, cholinergic afferents to the cerebral cortex are hypothesized to enhance activity at specific cortical circuits and determine the content of a conscious moment by activating certain combinations of postsynaptic sites in select cortical modules. It is proposed that these selections are enabled by learning-related restructuring that simultaneously adjusts the cytoskeletal matrix at specific constellations of postsynaptic sites giving all a similar geometry. The underlying mechanism of conscious awareness hypothetically involves cholinergic mediation of linkages between microtubules and microtubule-associated protein-2 . The first reason for proposing this mechanism is that previous studies indicate cognitive-related changes in MAP-2 occur in cholinoceptive cells within discrete cortical modules. These cortical modules are found throughout the cerebral cortex, measure 1–2 mm2, and contain approximately 103–104cholinoceptive cells that are enriched with MAP-2. The subsectors of the hippocampus may function similarly to cortical modules. The second reason for proposing the current mechanism is that the MAP-2 rich cells throughout the cerebral cortex correspond almost exactly with the cortical cells containing muscarinic receptors. Many of these cholinoceptive, MAP-2 rich cells are large pyramidal cell types, but some are also small pyramidal cells and nonpyramidal types. The third reason for proposing the current mechanism is that cholinergic afferents are module-specific; cholinergic axons terminate wholly within individual cortical modules. The cholinergic afferents may be unique in this regard. Finally, the tapering apical dendrites of pyramidal cells are proposed as primary sites for cholinergic mediation of linkages between MAP-2 and microtubules because especially high amounts of MAP-2 are found here. Also, the possibility is raised that muscarinic actions on MAP-2 could modulate microtubular coherence and self-collapse, phenomena that have been suggested to underlie consciousness
|Keywords||No keywords specified (fix it)|
|Categories||categorize this paper)|
Setup an account with your affiliations in order to access resources via your University's proxy server
Configure custom proxy (use this if your affiliation does not provide a proxy)
|Through your library|
References found in this work BETA
No references found.
Citations of this work BETA
No citations found.
Similar books and articles
Mark Solms (2000). Forebrain Mechanisms of Dreaming Are Activated From a Variety of Sources. Behavioral and Brain Sciences 23 (6):1035-1040.
J. Allan Hobson, Edward F. Pace-Schott & Robert Stickgold (2000). Dream Science 2000: A Response to Commentaries on Dreaming and the Brain. Behavioral and Brain Sciences 23 (6):1019-1035.
Lawrence Shapiro (2009). Making Sense of Mirror Neurons. Synthese 167 (3):439 - 456.
Emma Borg (2007). If Mirror Neurons Are the Answer, What Was the Question? Journal of Consciousness Studies 14 (8):5-19.
Nancy J. Woolf & Stuart R. Hameroff (2001). A Quantum Approach to Visual Consciousness. Trends in Cognitive Sciences 5 (11):472-478.
Mark Solms (2002). Dreaming: Cholinergic and Dopaminergic Hypotheses. In Elaine Perry, Heather Ashton & Allan Young (eds.), Neurochemistry of Consciousness: Neurotransmitters in Mind. Advances in Consciousness Research. John Benjamins. 123-131.
Mark Solms (2000). Dreaming and Rem Sleep Are Controlled by Different Brain Mechanisms. Behavioral and Brain Sciences 23 (6):843-850.
Daniel Collerton & Elaine Perry (2007). Do Multiple Cortical-Subcortical Interactions Support Different Aspects of Consciousness? Behavioral and Brain Sciences 30 (1):88-89.
Added to index2009-01-28
Total downloads24 ( #85,274 of 1,692,490 )
Recent downloads (6 months)1 ( #184,284 of 1,692,490 )
How can I increase my downloads?