Introduction to Neural Coding

• Neural Coding Explained
  • Action potentials are uniform in height regardless of stimulation intensity (amplitude remains constant).
  • Increase in loudness = Amplitude Modulation (used to attract attention).

Types of Modulation

• Amplitude Modulation (AM)

  • Refers to the changing loudness of sound (e.g., yelling to get attention).
  • Expresses how amplitude affects the perception of sound but does not change action potential height.

• Frequency Modulation (FM)

  • Frequency of action potentials changes in relation to stimulus intensity.
  • Describes how differences in stimulus lead to varying action potentials:
  • Lifting lighter objects (like a pen) correlates with lower frequency.
  • Lifting heavier objects (like a chair) correlates with higher frequency.
  • Thus, stronger stimulation (greater weight) results in more frequent action potentials.

Neural Pools and Circuits

• Understanding circuit types necessary for body function:
  • Diverging Circuit: One neuron stimulates multiple neurons (e.g., one impulse leads to multiple actions).
  • Converging Circuit: Multiple neurons converge onto one neuron (e.g., sensory input merge into CNS).
  • Sequential Circuit: Nerve impulses follow a sequence (e.g., performing tasks in a sequence).
  • Parallel Processing: Simultaneous processing of multiple inputs (e.g., multitasking).
  • Reverberating Circuit: Feedback loop where impulses circulate through the same pathways (e.g., deja vu).

Memory Formation and Recall

• Creating Memories
  • A strong memory recall utilizes a reverse circuit – when a new memory is formed, it can activate the same pathways rapidly upon retrieval, akin to deja vu.
  • Engrams: Represent the memory pathways in the brain that are established by repeated learning.
  • Practice leads to smoother execution of tasks, such as using scissors, reinforcing neural pathways.

Synaptic Plasticity

• Synapses are dynamic, and changes to synapses enhance transmission effectiveness (synaptic plasticity).
• Types of Memory:
  • Immediate Memory: Quick recall (e.g., a series of numbers).
  • Short-term Memory: A few-hour retention (e.g., working memory).
  • Long-term Memory (LTM): Durable storage lasting for years which can be explicit (fact-based) or implicit (emotion-based).
  • Example: Baby powder or bubble gum relates to implicit memory.【6:20】

Memory Loss Mechanisms

• Long-term Depression:
  • Caused by low calcium levels; this affects dendritic spines.
• Alzheimer's Disease: Memory loss linked to hippocampus deterioration and mobility issues (e.g., 'pill rolling' tremor). Patients show challenges during tasks due to neural degradation.

Overview of the Spinal Cord and Nervous System

• Spinal Cord Anatomy:

  • Spinal column comprises cervical, thoracic, and lumbar regions.
  • Enlargements situated in cervical and lumbar regions for upper and lower body connectivity respectively.

• Protection and Structure:

  • Three meninges surrounding the spinal cord:
  • Dura Mater: Outer tough layer (composed of collagen), connects to the skull. Has an epidural space used for anesthesia.
  • Arachnoid Layer: Middle layer with trabeculae; has cerebrospinal fluid (CSF) in the subarachnoid space.
  • Pia Mater: Inner layer, intimately related to the spinal cord/brain surface.

Spinal Cord Components

• Spinal nerves consist of sensory (dorsal) and motor (anterior) roots.
• Gray (H-shaped) and white matter comprise functional areas:
  • Dorsal Horn: Concerns sensory processing.
  • Anterior Horn: Associated with motor control.
  • Lateral Horn: Connects to the visceral nervous system within thoracic vertebrae.