Hemisphere Dominance, memory, Basal Ganglia

Hemisphere Dominance

  • Definition: Hemisphere dominance refers to the preference for using one hemisphere of the brain for certain functions, particularly language-related activities such as speech, writing, and reading.

  • Key Functional Areas:

    • Broca's Area: Involved in language production (speech, writing).
    • Wernicke's Area: Involved in language comprehension (reading).

  • General Statistics:

    • Approximately 90% of individuals are left hemisphere dominant for language functions (using left Broca's and Wernicke's areas).
    • 90% of right-handed individuals are left hemisphere dominant.
    • 64% of left-handed individuals are left hemisphere dominant.
    • The remaining individuals:
    • 10% of right-handed individuals are right hemisphere dominant.
    • 20% of left-handed individuals are right hemisphere dominant.
    • 16% of left-handed individuals use both hemispheres equally.

  • Handedness and Brain Lateralization:

    • The notion that handedness correlates with hemisphere dominance is nuanced. While many right-handed individuals are left hemisphere dominant, left-handed individuals exhibit more variability in hemisphere usage.

  • Personal Anecdotes:

    • In-class discussions often reveal that many individuals have mixed dominance, for example:
    • Writing with one hand while being dominant in sports or other activities with the opposite hand.
    • Examples provided include someone ice skating who found strength in spinning in the opposite direction of their writing hand, illustrating complex interactions between hand preference and brain function.

  • Activity Suggestion:

    • Students are encouraged to assess their own handedness and hemisphere dominance through a quick non-scientific test linked on the course platform.

Memory

  • Definition: Memory is described as "a consequence of learning" and it plays a crucial role in brain activity and longevity.

  • Short-Term Memory:

    • Short-term memory involves temporary storage of information, where neurons are engaged in a circuit of connections.
    • Example: Meeting someone new and remembering their name briefly; neurons are active while engaged, but memory fades once attention shifts away.

  • Neural Activity in Memory:

    • Memory formation occurs in the hippocampus, which is involved in converting short-term memories into long-term ones.

  • Conversion to Long-Term Memory:

    • To maintain information, structural changes must occur in the brain, such as:
    • Increased release of neurotransmitters.
    • Formation of additional synapses.
    • Development of more spines on dendrites, enhancing the brain's wiring capacity.

  • Methods for Memory Retention:

    • Repetition: Essential for reinforcing memory.
    • Active Engagement Strategies:
    • Making flashcards.
    • Labeling diagrams.
    • Self-quizzing and peer quizzing.
    • Drawing diagrams or creating visual aids.
    • Active interaction with material solidifies memory by changing anatomical and physiological structures in the brain, leading to improved information retention.

Basal Ganglia

  • Definition: Basal ganglia are a group of nuclei located deep within the cerebral hemispheres, composed of gray matter.

    • Names of components include:
    • Caudate nucleus
    • Putamen
    • Globus pallidus

  • Function:

    • Responsible for the subconscious control of skeletal muscles, facilitating the initiation and cessation of voluntary motor activity.
    • These structures help maintain baseline muscle tension to prevent atrophy.

  • Mechanisms of Action:

    • Although voluntary actions are consciously commanded (e.g., getting up from a chair), basal ganglia facilitate muscle readiness without overt thought.

  • Clinical Relevance:

    • Parkinson's Disease:
    • Inhibition of the voluntary activity is mediated by the neurotransmitter dopamine.
    • Loss of dopamine production leads to impaired initiation of movement and the characteristic tremor associated with Parkinson's.
    • In a relaxed state, the involuntary contraction necessary to maintain tone is disrupted without sufficient dopamine, contributing to motor control issues.

  • Visual Location:

    • The basal ganglia are positioned deeper in the brain, below the cerebral cortex, playing a critical role in motor function and coordination.

Conclusion

  • Topics covered in the next segment will include a discussion on the diencephalon, the reticular formation, and the cerebellum.
  • Students are reminded of the interconnectedness of motor control, memory, and hemisphere dominance in understanding brain functionality and structure.