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Brain Regions and Communication

• Communication in the Brain

  • Brain regions communicate via white matter.

  • Information travels through myelinated axons, which are bundled together.

  • Similar information travels within a single bundle of these axons.

Central Nervous System (CNS)

• Tracks and Nuclei

  • Tracks in the CNS are analogous to nerves in the peripheral nervous system (PNS).

  • Nuclei in the CNS function similarly to ganglia in the PNS.

Types of White Matter Tracts in the Brain

1. Association Tracts

   • Connect adjacent areas of the cortex (ipsilateral communication).

   • Involve primary cortex (receiving raw sensory data) and association areas (processing and integrating that data).

   • Example: Primary somatosensory cortex connects to secondary somatosensory areas for better sensory integration.

2. Commissural Tracts

   • Connect the two hemispheres of the brain.

   • Main structure involved: Corpus Callosum.

   • Important in facilitating communication between the left and right hemispheres.

3. Projection Tracts

   • Project information from the brain to other parts of the body.

   • Examples include motor pathways originating from the primary motor cortex to the spinal cord.

The Cerebral Cortex

• Structure

  • Composed predominantly of gray matter (outer 3 mm of the brain).

  • Contains gyri (ridges) and sulci (grooves), which increase surface area and accommodate more neurons.

• Neuronal Composition

  • Two main types of neurons:

    • Stellate Cells: Short axons, star-shaped, primarily local communication.

    • Pyramidal Cells: Pyramid-shaped, larger axons that can project information longer distances.

• Layers of the Cerebral Cortex

  • Layer I: Acellular, with minimal neuronal cell bodies.

  • Layers II & III: Contain smaller pyramidal cells.

  • Layer IV: Primarily comprised of stellate cells (granule layer).

  • Layers V & VI: Larger pyramidal cells involved in deeper projections.

Basal Nuclei and Fine Motor Control

• Basal Nuclei (Corpus Striatum)

  • Comprised of three nuclei: Caudate Nucleus, Putamen, and Globus Pallidus.

  • Responsible for fine motor control and coordination tasks.

  • Interacts with structures like the substantia nigra.

The Limbic System

• Function

  • Involved in memory and emotion.

  • Key structures:

    1. Cingulate Gyrus: Located above the corpus callosum, involved in emotional regulation.

    2. Hippocampus: Important for memory formation and retention.

    3. Amygdala: Processes emotional memories, particularly fear and pleasure.

Memory Formation

• Memories are formed through synaptic remodeling, reinforcing connections between neurons (engrams).

• Forgetting is also essential; it allows for prioritizing important information and avoiding overload.

Types of Amnesia

• Anterograde Amnesia: Inability to form new memories post-incident.

• Retrograde Amnesia: Inability to recall memories formed before a specific incident.

Brain Waves and Sleep

• EEG (Electroencephalogram) records brain wave patterns, indicating activity levels during various states.

• Stages of Sleep: Includes cycles of non-REM and REM sleep.

  • REM Sleep: Characterized by rapid eye movement and high brain activity, crucial for memory consolidation.

Cognition

• The cognitive process involves learning and memory.

• Majority (about 75%) of the brain consists of association areas that integrate sensory and cognitive information.

  • Lesions in specific areas lead to distinctive cognitive deficits:

    • Contralateral Neglect Syndrome: Ignoring one side of the body due to right parietal lobe damage.

    • Agnosia: Inability to recognize objects despite functional visual abilities.

    • Prosopagnosia: Difficulty recognizing faces due to damage in specific regions in temporal lobe.

    • Frontal Lobe Lesions: Changes in personality and behavior.