Visual Motion and Brain Regions

Jul 16, 2024

Lecture on Visual Motion and Brain Regions

Introduction

  • Key concept: The importance of visual motion for survival and daily function.
  • Humans have unique abilities such as precision throwing.
  • Motion detection is crucial, both for avoiding dangers (e.g., predators) and navigating spaces (e.g., crossing streets).

Motion Perception and Detail

  • Facial Expressions: Micro-expressions are subtle but detectable, play a key role in social interactions.
  • Understanding emotion through facial details.

Brain Machinery for Motion Processing

  • Evolutionary importance of motion processing suggests dedicated brain areas for it.
  • Speculative question: Could humans survive in a strobe-like environment all the time?
  • Real-life example: A woman who can't see motion will be discussed next.

Computational Inference in Perception

  • Little thought exercise: Imagine writing code to detect motion in video – what computations are needed?
  • Understanding such processes can provide insight into how the brain works.

Neuroanatomy Overview

  • Goals: Quick review to prepare for a brain dissection with a renowned neuroscientist, covering basics from previous courses (900/901).

Human Brain and Neurons

  • Neuron Basics: Neurons with cell body, axon, dendrites. Myelin sheath increases signal speed.
  • Synapses: 100 billion neurons, each with thousands of synapses.
  • Energy Efficiency: Brain operates on 20 watts compared to 20,000 watts for IBM's Watson.

Major Brain Components

  1. Brain Stem: Controls basic functions (breathing, consciousness). Essential for life.
  2. Cerebellum: Motor coordination, debated cognitive roles.
  3. Limbic System: Includes thalamus, hippocampus, amygdala.
    • Thalamus: Sensory relay station.
    • Hippocampus: Memory and navigation.
    • Amygdala: Emotion processing, particularly fear.
  4. White Matter: Axonal connections making up 45% of the brain.

The Cortex

  • Primary Sensory Regions: Visual, auditory, somatosensory, and motor cortex.
  • Mapping in the Brain: Maps for different sensory modalities (e.g., retinotopic map in visual cortex).

Visual Area: MT / V5

  • Roles and Criteria: Identified through function, connectivity, and physical structure.
  • Function: Directional sensitivity. Shown via neuron recordings and motion aftereffects.
  • Connectivity: Unique connections identified in wiring diagrams.
  • Cytoarchitecture: Distinct structure visible in stained brain sections.

Functional MRI and Motion Perception in Humans

  • fMRI experiments show higher response to moving vs. stationary dots.
  • Establishing direction selectivity using aftereffects and behavioral responses.

Patient Cases

  • Akinetopsia: Inability to perceive motion due to damage in Area MT.

Conclusion

  • Key Idea: Understanding these structures and functions is fundamental to understanding perception.
  • Brief overview of terminology and core takeaways from the lecture.

Key Terms: Neuron, synapse, myelin, brain stem, cerebellum, thalamus, hippocampus, amygdala, white matter, cortex, visual area MT, retinotopy, cytoarchitecture, aftereffect, akinetopsia.