Consciousness, Thought, and Memory

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Consciousness, Thought, and Memory

• Cristina Krage, Anthony Kurland, and Malynda Clark

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What is Consciousness?

• Consciousness is a difficult concept to
  define. Even today, not everything regarding its
  complexities is fully understood. However, we do
  know that it is graded on a continuum, ranging
  from alertness at the highest state, through
  drowsiness/lethargy, stupor, and coma at the
  lowest state. It involves the voluntary
  initiation and control of movement, the
  perception of sensation, and higher mental
  processing (memory, logic, judgment, etc). To be
  functional, simultaneous stimulation of large
  areas of the cerebral cortex must occur. This
  activity is superimposed on other types of
  neuronal activity. This activity can be both
  regional and/or involved in cognition. In any
  case, the idea of consciousness is holistic and
  totally interconnected within the cerebrum.

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What is Memory?

• Memory is the storage and retrieval of
  information. The two stages of memory are short
  term (STM) and long term (LTM). STM is the first
  step, and is limited to seven or eight chunks of
  information. Some 5 of sensory input is
  transferred to the STM. The LTM is of limitless
  capacity, but its ability to store and retrieve
  information declines with aging. The transfer of
  information from STM to LTM is affected by
  emotional state, rehearsal (repetition),
  association (tying new information to old), and
  automatic memory (memory that is not consciously
  formed). The consolidation of memory involves
  fitting new facts into various categories of
  knowledge already stored in the cerebral cortex.
  These newly stored memories are usually filed
  along with the context in which they were learned.

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Categories of Memory

• Declarative (fact) memory- learning specific
  information (names, faces, words, and dates)
  related to conscious thought and the ability to
  manipulate symbols and language.
• Nondeclarative memory- less conscious or
  unconscious learning. This type of memory
  contains 3 subcategories procedural (skills)
  memory, motor memory, and emotional memory. These
  are acquired through experience and repetition,
  and do not preserve the circumstance of learning.

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Brain Structures involved in Memory

• Specific pieces of memory are stored near
  regions of the brain that need them.
• Pathway of Memory Storage Association cortices
  -gt medial temporal lobe (hippocampus and temporal
  cortical areas) -gt thalmus and prefrontal cortex
  lt-basal forebrain
• Memories are retrieved when the same sets of
  neurons that were initially involved in memory
  formation are stimulated.

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Mechanisms of Memory

• During learning
• 1. Neuronal RNA content is altered and newly
  synthesized mRNAs are delivered to axons and
  dendrites
• 2. Dendritic spines change shape.
• 3. Unique extracellular proteins are
  depositited at synapses involved in LTM
• 4. The number and size of pre-synaptic
  terminals may increase
• 5. More neurotransmitters are released by
  pre-synaptic neurons.

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Alzheimers Disease

• In this disease, normal storage and retrieval
  of memory is disrupted by plaques, which
  accumulates between neurons, and tangles, twisted
  sections of the protein tau (which normally
  supports neuronal structure), causing cell damage
  and death. People afflicted with this disease
  present all the symptoms one would expect from a
  disorder of its nature forgetfulness,
  personality changes, poor judgment, etc. These
  symptoms demonstrate the complexity of the
  nervous system, particularly the cerebrum as it
  pertains to consciousness and memory. If the
  slightest element should become ineffective, the
  entire system often follows soon after.

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Thought

• The phenomena of thought has been puzzled over
  by philosophers, scientists, and other men of
  great learning for thousands of years. Despite
  the great advances we have made in technology and
  available data, exactly how and why we think is
  mostly still a mystery. However, it is often
  equated to awareness of the subconscious, which
  encompasses all actions performed without the
  conscious decision to do so, and conscious mind.

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Sources

• Human Anatomy and Physiology, Seventh Edition.
  Marieb, Elaine N. and Hoehn, Katja. 2007.
• Pukamble.tripod.com
• MayoClinic.com