Can there be a science of consciousness?
The Introduction module of the Consciousness Studies Wikibook introduces the idea that consciousness has long been an object of study. What tools for studying consciousness were available to Aristotle? In his book De Anima, Aristotle described his own personal conscious experiences. As might be expected for a primate, Aristotle placed a heavy emphasis on visual perception. Introspective reports of conscious experiences remain an important source of information about consciousness, but reliance on subjective reports of personal experiences is not a very powerful tool for exploring the physical basis of consciousness. In fact, many people prefer to interpret their subjective experiences in terms of the activity of a supposed non-physical "conscious being" or soul.
In his book, The Astonishing Hypothesis, Francis Crick described the fact that many neuroscientists fully expect that it will eventually be possible to produce a satisfactory understanding of the physical basis by which human brains produce conscious experiences. What is the basis for this confidence? What tools in addition to introspective reports of normal conscious exist for study of consciousness?
One approach to the study of consciousness involves making correlations between abnormal conscious experiences and perturbations of the nervous system. For example, strokes can damage specific brain regions and result in altered patterns of conscious experience. For example, if a stroke damages part of the visual cortex that generates our normal sense of movement of seen objects, we can lose our normal ability to experience the sight of moving objects (see The Functional Organization of Extrastriate Visual Areas).
Humans have a long history of using drugs to modulate conscious experiences. By combining drugs with scans of brain activity, it is possible to relate the ability of drugs to alter consciousness to changes in the activity of particular brain regions (for example, see Preclinical Assessment of Candidate Analgesic Drugs: Recent Advances and Future Challenges). In addition to drugs, electrical stimulation of the brain and modification of brain activity using magnetic fields can be used to alter conscious experience by changing the function specific brain regions.
Genetic methods are also available for study of the physical basis of conscious experiences. For example, genetic mutations in a sodium channel gene can result in the abnormal experience of burning pain sensation (see Temperature dependence of erythromelalgia mutation L858F in sodium channel Nav1.7). Other mutations in the same gene can cause inability to sense pain (see An SCN9A channelopathy causes congenital inability to experience pain). Other well-characterized mutations can disrupt color perception.