Lecture Notes on Visual Motion and Neuroanatomy

Key Concepts

Importance of Motion Perception

• Motion perception is vital for humans to avoid predators and interact with the environment.
• Precision throwing is a uniquely human ability, while motion perception is shared with many animals.
• Lip reading may become necessary if audio quality is poor, highlighting the importance of visual cues in communication.

Facial Expressions

• Subtle facial expressions can convey complex emotions.
• Humans are sensitive to fleeting expressions, which can inform interpersonal interactions.

Biological and Ecological Relevance

• Motion perception may require specialized brain mechanisms due to its biological and ecological importance.
• Living in a world with strobe-like flickers could severely impair daily functioning and safety.

The Human Brain: Structure and Function

Overview

• The human brain contains approximately 100 billion neurons, which are energetically efficient (20 watts compared to 20,000 watts for IBM's Watson).

Neuron Basics

• Neurons consist of a cell body, nucleus, dendrites, and axon.
• Myelin sheaths increase the speed of neural signal transmission.

Major Components of the Brain

1. Brain Stem:
   • Primitive part shared with many animals; controls basic life functions (breathing, consciousness).
2. Cerebellum:
   • Involved in motor coordination; debated role in cognition.
3. Limbic System:
   • Includes structures like the hippocampus and amygdala.
4. White Matter:
   • Comprises axons connecting different brain regions; important for understanding brain connectivity.

Key Brain Structures

• Thalamus:
  • Acts as a relay station for most sensory information before it reaches the cortex.
  • Increasing evidence suggests it plays a role in cognitive processing.
• Hippocampus:
  • Involved in long-term episodic memory and navigation.
  • Notable cases: HM (lost episodic memory after surgery) and Lonnie Sue Johnson (viral infection leading to loss of episodic memory).
• Amygdala:
  • Key role in emotion, especially fear (Four F's: Fighting, Fleeing, Feeding, Mating).
  • Patient SM lost amygdala and cannot experience fear.

White Matter

• Comprises 45% of the brain; connects different regions.
• Essential for understanding brain function and organization.

Cortical Organization

Primary Sensory Regions

• Primary sensory regions (visual, auditory, somatosensory) have distinct maps corresponding to the sensory input they process.
• Retinotopic Maps: Visual cortex has a systematic layout that corresponds to visual input from the retina.
• Touch and Auditory Maps: Similarly organized in somatosensory and auditory cortices.

Criteria for Distinct Cortical Areas

1. Distinct Function: Neurons in a region respond to different stimuli than their neighbors.
2. Connectivity Fingerprint: Each region has unique connections to other brain areas.
3. Cytoarchitecture: Physical differences in structure when examined histologically.

Visual Area MT

• A region identified in monkeys that is specialized for motion detection.
• Evidence for area MT includes:
  • Individual neuron recordings showing directional sensitivity.
  • Functional MRI studies showing increased activity in response to motion.
  • The presence of specific connections and unique histological properties.

Conclusion

• The lecture covered the integration of motion perception, brain structure, and the importance of neuroanatomy in understanding functionality. The next section will build on these concepts.