Introducing perception
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Introducing Perception. Of microbes and men. O rganisms from microbes to man must interact with the world F ind food and mates, avoid predators and physical harm. Representing the world.

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Introducing Perception

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Introducing perception

Introducing Perception

PSY 295 - Fall 2012 - Grinnell College


Of microbes and men

Of microbes and men

  • Organisms from microbes to man must interact with the world

  • Find food and mates, avoid predators and physical harm

PSY 295 - Fall 2012 - Grinnell College


Representing the world

Representing the world

  • Organisms extract information about the environment tobuild an internal representation of the environment

  • Representations guide their actions

from Russel & Norvig (1995)

PSY 295 - Fall 2012 - Grinnell College


Sources of useful information

Sources of useful information

  • Reflected light

  • Pressure/temperature

  • Sound waves

  • Chemical gradients

PSY 295 - Fall 2012 - Grinnell College


Representations

Representations

  • Sensory representations need not be sophisticated to be useful

  • Even single cell organisms respond to sensory cues

PSY 295 - Fall 2012 - Grinnell College


Euglena

Euglena

  • Single cell photo-synthetic organism

  • Has eyespot which is sensitive to light

  • Moves towards light – Phototaxis

PSY 295 - Fall 2012 - Grinnell College


Bacteria

Bacteria

  • Swim towards food and away from poisons

  • Chemotaxis

PSY 295 - Fall 2012 - Grinnell College


Nervous systems

Nervous systems

  • Sensation and action in single-cell organisms are mediated by biochemical pathways

  • In multicellular organisms, sensation and action are mediated by the nervous system

PSY 295 - Fall 2012 - Grinnell College


The neuron

The neuron

  • Nervous systems are comprised of neurons

  • Neurons are cells specialized for transmitting information

PSY 295 - Fall 2012 - Grinnell College


Neural networks

Neural networks

  • To perform complicated information-processing, neurons are arranged into neural networks

PSY 295 - Fall 2012 - Grinnell College


Sensation and action

Sensation and Action

  • World-representing only useful if the organism can move

  • Organisms that cannot move do not need nervous systems

PSY 295 - Fall 2012 - Grinnell College


Tunicates

Tunicates

  • Larval form is like a tadpole which swims around

  • Once it finds a suitable rock, it cements itself in place and proceeds to digest its own brain

PSY 295 - Fall 2012 - Grinnell College


Sensory motor transformations

Sensory-motor transformations

  • A simple example of sensation leading to action is a reflex

PSY 295 - Fall 2012 - Grinnell College


Interneurons

Interneurons

  • More sophisticated sensory-motor transformations require an intervening hidden layer of interneurons

PSY 295 - Fall 2012 - Grinnell College


Bending reflex in leech

Bending reflex in leech

from Churchland & Sejnowski 1992

PSY 295 - Fall 2012 - Grinnell College


Leech reflex circuit

Leech reflex circuit

from Churchland & Sejnowski 1992

PSY 295 - Fall 2012 - Grinnell College


Far side cartoon

Far Side Cartoon

“Stimulus, response, stimulus, response. Don’t you ever think?”

PSY 295 - Fall 2012 - Grinnell College


More sophisticated representation

More sophisticated representation

  • Building more accurate representations of the world like we do can provide great advantages

  • Remember, reason about, and simulate the world

PSY 295 - Fall 2012 - Grinnell College


Sources of useful information1

Sources of useful information

  • Reflected light

  • Pressure/temperature

  • Sound waves

  • Chemical gradients

PSY 295 - Fall 2012 - Grinnell College


Light

Light

  • Provides information about things far away from the organism

  • Organisms living in caves or in deep sea often lack eyes

Texas blind salamander

PSY 295 - Fall 2012 - Grinnell College


Evolution of eyes

Evolution of eyes

  • Eyespots are simplest ‘eyes’

  • Cup eyes give directionality

from Land & Ferdnald 1992

PSY 295 - Fall 2012 - Grinnell College


Evolution of eyes1

Evolution of eyes

  • Pinhole opening helps to focus light

  • Reduces amount of light entering eye

from Land & Ferdnald 1992

from Palmer 1999

PSY 295 - Fall 2012 - Grinnell College


Evolution of eyes2

Evolution of eyes

  • A lens focuses the image while permitting lots of light into eye

from Palmer 1999

from Land & Ferdnald 1992

PSY 295 - Fall 2012 - Grinnell College


Visual system

Visual system

  • A sophisticated eye and visual system permits detailed analysis and interpretation of the scene

from Hubel (1995)

PSY 295 - Fall 2012 - Grinnell College


This course

This course

  • We will study information processing and perception in mammalian sensory systems

  • Touch, vision, hearing, olfaction, taste

  • Strong emphasis on sensory neuroscience

  • Connections to machine vision, medicine and consciousness

PSY 295 - Fall 2012 - Grinnell College


Related courses

Related courses

  • Fall 2012

    • Machine Vision (CS-295-02)

    • Vision Science Seminar (NRS-495)

    • Physiological Psychology (PSY-246)

  • Spring 2013

    • Computational Neuroscience (PSY-395)

PSY 295 - Fall 2012 - Grinnell College


See you later

See you later!

PSY 295 - Fall 2012 - Grinnell College


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