2017-10-10 14:46:39

Today's topics

  • Sensation & Perception
  • Common principles of neural organization

Basic questions

  • Exteroception
    • What's out there?
    • Where is it? Now? Moving?
  • Interoception
    • How do I feel?
  • Response: What should I do about it?
    • Internal
    • External

Systems/information processing view

  • Input
  • Processing
  • Memory
  • Output

You vs. Your Smartphone

Multisensory processing in a smartphone

Multisensory processing in a smartphone

Dimensions of sensory processing

  • Interoceptive
    • How am I?
  • Exteroceptive
    • What's in the world, where is it?

Questions for interoception

  • Tired or rested?
  • Well or ill?
  • Hungry or thirsty or sated?
  • Stressed vs. coping?
  • Emotional state?

Questions for exteroception

  • Who/What is out there?
  • Where is it?

Who/what

  • Animate/inanimate?
  • Conspecific (same species)/non?
  • Threat/non?
  • Familiar/un?
  • Mate/non? or Friend/not?
  • Food source/non?

Where

  • Distance
    • Proximal
    • Distal
  • Elevation, azimuth
  • Coordinate frames
    • Self/ego (left of me)
    • Object (top of object)
    • Allo/world (North of College)
  • Where moving?

How

  • What kind of response?
    • External
    • Internal
  • Approach/avoid/freeze
  • Signal/remain silent
  • Manipulate

More than 5 senses

From world to brain

  • How do events/entitities generate patterns that sensors can detect?
    • Chemical
    • Photic/electromagnetic
    • Mechanical/acoustic

How sensory channels differ

  • What is the energy/chemical source
  • How does the channel inform
    • What is out there
    • Where it's located

Vision

  • Electromagnetic radiation
  • What is it?
    • Shape, size, surface properties (color, texture, reflectance, etc.)
    • Wavelength/frequency, intensity

Vision

  • Where is it?
    • Position: Left/right; up/down on retina
    • Near/far: retinal disparity, interposition, height above horizon…
    • Orientation, motion

Audition

  • Vibrations in air or water
  • What is it?
    • Pattern of frequencies, amplitudes, durations

Audition

  • Where is it?
    • Left/right or up/down: Interaural time/phase, intensity differences, pinnae filtering
    • Motion: Frequency shifts via Doppler effect

Chemosensation

  • Chemicals in mouth, nasal cavity
  • What is it?
    • Mixture of chemicals
  • Where is it?
    • Left/right; up/down; near/far via intensity gradients

Somatosensation

  • Thermal or mechanical stimulation of skin
  • What is it?
    • Shape, size, smoothness, mass, temperature, deformability: Pattern of stimulation
  • Where it it?
    • Pattern of cutaneous receptors on skin

Interoception

  • Hunger/thirst
    • Receptors for nutrient, fluid levels
  • Energy levels
    • Receptors for hormones, NTs
    • ANS responses
  • Temperature
  • Mating interest
    • Receptors for hormones, NTs
    • ANS responses

Features of sensory signals

  • Tonic (sustained) vs. phasic (transient) responses
  • Adaptation
    • Decline in sensitivity with sustained stimulation
    • Most sensory systems attuned to change
  • Information propagates at different speeds

Common principles

  • Sensors detect repeating signals
    • In space (textures)
    • In time

Spatial frequency/contrast sensitivity

Frequencies in sound

Common principles

  • Compare (>1) sensor for each channel
    • Eyes
    • Ears
    • Nostrils
    • Skin surface

Why is the snake's tongue forked?

Common principles

  • Sensory neurons have "receptive fields"
    • Area on sensory surface that when stimulated changes neuron's firing

Tactile receptive field

Visual receptive field

Common Principles

  • Topographic maps

Tonotopic (frequency) maps in auditory cortex

Retinotopic maps in visual cortex

Common principles

  • Non-uniform sensitivity

Two-point touch thresholds

Acuity variations across visual field

Hearing threshold varies across frequency

Hierarchical processing

Parallel processing

Parallel processing

Next time…

  • Digging deeper into perceptual systems