1.4C Psychology Slides

UNIT 1: Biological Bases of Behavior

Module 1.4C: The Brain: Damage Response and Brain Hemispheres

Learning Targets

  • LT 1.4-8: Explain how a damaged brain can reorganize itself, and describe neurogenesis.

  • LT 1.4-9: Explain what split brains reveal about the function of our two brain hemispheres.

LT 1.4-8: Brain Reorganization and Neurogenesis

  • Neurogenesis:

    • Definition: The formation of new neurons.

    • Neurogenesis occurs throughout the lifespan but is most significant in infancy and childhood.

  • Brain Adaptation:

    • The brain is capable of adaptation as it learns; this means it can adjust its functioning to accommodate new information and experiences.

    • After brain damage, the brain faces limitations in repairing itself. Severely injured regions, particularly in the spinal cord or brain, typically cannot regenerate or fully repair.

    • Some degree of reorganization can occur, especially in young children, demonstrating the brain's modest capacity for recovery and adaptation after damage.

  • Neuroplasticity:

    • Definition: The brain's ability to reorganize and restore some functions after damage or due to disability.

    • It highlights the brain's resilience in adapting to changes and recovering from injuries.

  • Sensory Disabilities and Brain Functioning:

    • Individuals with sensory disabilities (e.g., blindness, deafness) often exhibit enhanced functioning in other sensory modalities.

    • For instance, these individuals may have increased capacity in touch and motion detection as the brain reallocates resources to optimize functioning in remaining senses.

  • Debate on Neurogenesis:

    • Ongoing research into neurogenesis suggests hopeful findings regarding the potential for creating new neurons, presenting implications for recovery from brain injuries and age-related cognitive decline.

LT 1.4-9: Insights from Split-Brain Studies

  • Corpus Callosum:

    • Definition: A large band of neural fibers that connects the two brain hemispheres, facilitating inter-hemispheric communication.

  • Split Brain:

    • Definition: A condition resulting from surgical intervention that severes the fibers (predominantly the corpus callosum) connecting the two hemispheres of the brain. This procedure is generally considered in extreme cases of seizure disorders.

  • Lateralization of Brain Function:

    • Despite their anatomical similarity, the two hemispheres of the brain have specific functions and responsibilities. This division of labor is known as lateralization.

    • Communication: The two hemispheres communicate via the corpus callosum, maintaining coordination in sensory and motor tasks.

  • Research Findings by Michael Gazzaniga:

    • Gazzaniga's studies with split-brain patients revealed significant insights:

    • Most language abilities are localized in the left hemisphere.

    • Patients with a severed corpus callosum faced limitations in verbal communication about objects perceived in their left visual field, as that information could not be relayed to the language centers in the left hemisphere.

    • Unique Abilities of Split-Brain Patients:

    • Patients demonstrated remarkable capabilities such as simultaneously using both hands to draw different shapes, reflecting the independent functioning of the hemispheres when communication is disrupted.

Example of Split-Brain Research

  1. Experimental Procedure:

    • Subjects are shown two words separated by a dot:

      • (a) Visual Stimulation: Two words (e.g., "ART" and "HE") are momentarily projected on a visual display.

  2. Test Questions:

    • (b) Participants are asked to report which word they saw or to point with their left hand to the word they recognized.

  3. Understanding Outcomes:

    • If a red light flashes to the right hemisphere and a green light to the left:

      • (a) Each hemisphere perceives its respective color.

      • (b) The individual may not be aware of the color differences due to disconnection between hemispheres.

      • (c) The individual will only verbally report seeing the color perceived by the left hemisphere (associated with the right visual field).

    • This situation exemplifies the dissociation of knowledge and awareness in split-brain patients.

Functionality of Brain Hemispheres

  • In a functioning brain, each hemisphere is responsible for the opposite sides of the body regarding movement and sensory processing.

  • Left Hemisphere Functions:

    • Logical reasoning, mathematical processing, and language comprehension and production.

  • Right Hemisphere Specialties:

    • Facial recognition, spatial reasoning, and self-awareness.

  • Integration of Functions:

    • Human functions typically result from integrated activity from both hemispheres, emphasizing the cooperative nature of brain operation rather than strictly lateralized functions.