Chemistry and consciousness/Neurochemistry
Welcome to the second lesson in the "Chemistry and consciousness" learning project. This lesson has guided reading and discussion of the neurochemistry of consciousness.
We can rapidly shift our attention between different components of conscious experience that are generated by the brain. Visual cortex regions towards the back of the head are required for us to experience color vision or normal consciousness of objects moving in the visual field. Auditory cortex regions at the side of the head generate conscious experience of sounds. Normal sensation of touch is requires neuronal activity in the somatosensory cortex. The various brain regions that generate various types of conscious experience are connected by axons and coordinated by electrical signals that rapidly travel along axons. These long-distance and rapid signals in the brain are called action potentials.
The sodium-potassium pump is particularly important in the chemistry that makes possible the action potentials that carry rapid long distance signals in the brain. This enzyme uses available chemical energy inside neurons to move sodium ions out of cells and push potassium ions inside. Once these imbalances of electrically charged ions are established across the cell membrane, the energy stored in those transmembrane ion gradients can be used to produce rapidly propagating electrical signals, action potentials, that move down axons.
During sleep, it is common to have altered consciousness, demonstrated by the poor ability to remember dreams that are experienced during sleep. Even periods of sleep without dreams have similar energy use and numbers of action potentials. Neurons in the brain do not become inactive during the altered consciousness of sleep, but there are subtle alterations in the pattern of action potentials in cortical neurons. What kinds of "subtle" effects can be modulated so as to alter the relationship between action potentials and conscious experiences? In the brain, the effects of action potentials are mediated through the complex chemistry of neurotransmission.
Memory can be divided into two general forms: short-term working memory, and long-term consolidated memory. In terms of generating conscious experience, both are essential: the former in generating a baseline level of situational awareness and a cohesive understanding of temporarily (i.e. not constantly trapped in the present), and the latter in processes ranging from one's ability for recognition and comprehension to establishing a sense of a sense of self based on autobiographical knowledge.
For an overview of the basic forms and mechanisms of memory, please visit the Fundamentals of Neuroscience page until this wikiversity project has been completed.
- Chemistry and consciousness - main page for the Chemistry and consciousness learning project
- Is consciousness a chemical process? - first page in the series; introduction to the idea of distributed brain processes as the source of consciousness.
- Basic Neurochemistry: Molecular, Cellular and Medical Aspects Sixth Edition by George J. Siegel, Edward Hines Jr., Bernard W. Agranoff, Stephen K. Fisher, R. Wayne Albers and Michael D. Uhler (1999) ISBN 0-397-51820-X
- It is difficult to define metabolic equivalents of consciousness, mental work and sleep, in Basic Neurochemistry by George J. Siegel, et al.
- An information integration theory of consciousness by Giulio Tononi in BMC Neuroscience (2004); 5: 42.