Consciousness is defined in the dictionary as: 1. the state of
being conscious; awareness of one's own existence, sensations, thoughts, surroundings,
etc. 2. the thoughts and feelings, collectively,
of an individual or of an aggregate of people: the moral consciousness of a nation.3.
full activity of the mind and senses, as in waking life: to regain consciousness
after fainting. 4. awareness of something for what it is; internal knowledge:
consciousness of wrongdoing. 5. concern, interest, or acute awareness: class
consciousness. 6. the mental activity of which a person is aware as contrasted
with unconscious mental processes. 7. Philosophy. the mind or the mental
faculties as characterized by thought, feelings, and volition. Idioms: raise
one's consciousness: to
increase one's awareness and understanding of one's own needs, behavior, attitudes,
etc., especially as a member of a particular social or political group.
Psychologists define consciousness as the quality or state
of awareness, or, of being aware of an external object or something within
oneself. The English philosopher John Locke defined it as “the perception of
what passes in a man's own mind.” It is also defined as: sentience, awareness,
subjectivity, the ability to experience or to feel, wakefulness, having a sense
of selfhood, and the executive control system of the mind. Despite the
difficulty in definition, many philosophers believe that there is a broadly
shared underlying intuition about what consciousness is. As Max Velmans and Susan Schneider wrote in
The Blackwell Companion to Consciousness: "Anything that we are aware of
at a given moment forms part of our consciousness, making conscious experience
at once the most familiar and most mysterious aspect of our lives."
Early views
In the early 19th century the concept was variously
considered. Some philosophers regarded it as a kind of substance, or “mental
stuff,” quite different from the material substance of the physical world.
Others thought of it as an attribute characterized by sensation and voluntary movement,
which separated animals and men from lower forms of life and also described the
difference between the normal waking state of animals and men and their
condition when asleep, in a coma, or under anesthesia (the latter condition was
described as unconsciousness). Other descriptions included an analysis of
consciousness as a form of relationship or act of the mind toward objects in
nature, and a view that consciousness was a continuous field or stream of
essentially mental “sense data,” roughly similar to the “ideas” of earlier
empirical philosophers.
Philosophers since the time of Descartes and Locke have
struggled to comprehend the nature of consciousness and pin down its essential
properties. Issues of concern in the philosophy of consciousness include
whether the concept is fundamentally coherent; whether consciousness can ever
be explained mechanistically; whether non-human consciousness exists and if so
how it can be recognized; how consciousness relates to language; whether
consciousness can be understood in a way that does not require a dualistic distinction
between mental and physical states or properties; and whether it may ever be
possible for computing machines like computers or robots to be conscious, a
topic studied in the field of artificial intelligence.
At one time consciousness was viewed with skepticism by many
scientists, but in recent years it has become a significant topic of research
in psychology, neuropsychology and neuroscience. The primary focus is on
understanding what it means biologically and psychologically for information to
be present in consciousness—that is, on determining the neural and
psychological correlates of consciousness. The majority of experimental studies
assess consciousness by asking human subjects for a verbal report of their
experiences (e.g., "tell me if you notice anything when I do this").
Issues of interest include phenomena such as subliminal perception, blind sight,
denial of impairment, and altered states of consciousness produced by drugs and
alcohol, or spiritual or meditative techniques.
Neurophysiological mechanisms
That consciousness depends on the function of the brain has
been known from ancient times. Although detailed understanding of the neural
mechanisms of consciousness has not been achieved, correlations between states
of consciousness and functions of the brain are possible. Levels of
consciousness in terms of levels of alertness or responsiveness are correlated
with patterns of electrical activity of the brain (brain waves) recorded by an
electroencephalograph. During wide-awake consciousness the pattern of brain
waves consists of rapid irregular waves of low amplitude or voltage. In
contrast, during sleep, when consciousness can be said to be minimal, the brain
waves are much slower and of greater amplitude, often coming in periodic bursts
of slow waxing and waning amplitude.
Both behavioral levels of consciousness and the correlated
patterns of electrical activity are related to the function of a part of the
brainstem called the reticular formation. Electrical stimulation of the
ascending reticular systems arouses a sleeping cat to alert consciousness and
simultaneously activates its brain waves to the waking pattern. It was once
supposed that the neurophysiological mechanisms subserving consciousness and
the higher mental processes must reside in the cortex. It is more likely,
however, that the cortex serves the more specialized functions of integrating
patterns of sensory experience and organizing motor patterns and that the
ascending reticular system represents the neural structures most critically
related to consciousness. The brainstem reticular formation should not,
however, be called the seat of consciousness. It represents an integrative
focus, functioning through its widespread interconnections with the cortex and
other regions of the brain. See also introspection; unconscious.
In medicine, consciousness is assessed by observing a patient's
arousal and responsiveness, and can be seen as a continuum of states ranging
from full alertness and comprehension, through disorientation, delirium, loss
of meaningful communication, and finally loss of movement in response to
painful stimuli. Issues of practical concern include how the presence of
consciousness can be assessed in severely ill, comatose, or anesthetized
people, and how to treat conditions in which consciousness is impaired or
disrupted.
(Adapted from Encyclopedia of Britannica and Wikipedia)
