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PSYCO104 Study Guide - Final Guide: Thalamus, Binge Drinking, Orexigenic

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Blaine Mullins
Study Guide

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Chapter 4: Sensation and Perception
Sensation: bare awareness that something is happening (resulting from stimulation of a
!sense organ); no organization, do not know what the thing is that you are seeing.
!-- Begins with Transduction: conversion of physical energy to neural impulses
!--Sensory adaptation: reduced sensitivity after prolonged exposure to stimulus
Perception: knowing what something is; the organization, identification, interpretation of
!a sensation.
!-- Perceptual system uses 3 types of info: 1. properties of physical environment
!(specific wavelengths). 2. electrical activity in NS. 3. prior experience and
Cognition: being aware of, knowing, thinking, learning, judging, etc.; Mostly
!Sensation (light enters eye, retinal cells activated) --> Perception (object
!identified) --> Cognition (think about object, memories)
Synesthesia: stimulation of one sensory pathway results in the automatic activation of
!another sensory system. IE: see a #, and a colour as well.. taste something in
!response to a word.
!-- Most common: involving color in some way.. seems to occur from childhood
!experiences.. every 1/300 people.. 70% influenced by genes, rest by
!environment, so can have it if blind. This shows it occurs in the brain, not from
!what you see. V1 and V4- visual cortex part of brain are activated.
!-- Clinical test to diagnose: shown array of letters for limited time. If synesthetic,
!can see hidden shapes/letters.
Bottom-up processing: aka data-driven; interpretation of something that comes from the
!data; start simple, create something more complex.. combine several bits of
!sensory information and combine it together to interpret a situation.
Top-down processing: interpretation of info that comes from oneʼs expectations,
!attention, assumptions, knowledge, etc.; brain naturally fills missing part of
!picture.. what you think impacts what you see, you set up your own expectations.
Sensory Coding: representation of characteristics of the environment by the firing of
!neurons. 3 Theories: 1. Specific Theory: each neuron does a different thing;
!different perceptions signaled by activity in specific neurons.. Different neurons
!fire for different situations. If neuron is destroyed, you can no longer experience
!that situation. 2. Temporal Coding Theory: different perceptions signaled by
!temporal activity in neurons; several action potentials occur at once.
!3. Across-fiber pattern theory aka population coding: different perceptions
!signaled by pattern of activity in group of neurons over time.. different set of
!neurons firing together=different experiences.
Psychophysics: studies how we perceive stimuli based on their sensory characteristics;
!methods that measure the strength of a stimulus and the observerʼs sensitivity to
!a) Threshold: lowest point where stimulus produces a sensation (absolute
!threshold: minimal intensity needed to just barely detect stimulus or difference

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!threshold: minimal change in stimulus that can just barely be detected(JND:
!just-noticeable difference)) -- Weberʼs Law: JND of any stimulus is a constant
!proportion regardless of the intensity of the stimulus.
!b) Signal Detection theory: response to stimulus depends on sensitivity to
!stimulus in presence of noise and on a personʼs response criterion.
Visual Acuity: ability to see fine detail
Properties of Light Waves: Length- hue(color), Amplitude- Brightness, Purity- Saturation
Cornea: protection for iris and pupil; aid in focus of light
Lens: focuses light
Pupil: determines how much light enters the eye
Accommodation: adjustment of shape of lens to compensate for distance of objects
!from retina. Zonule Fibers (ligaments attached to and pulls on lens) contract for
!distant objects, ciliary muscles refract.. and refract for close objects, ciliary
!muscles contract
Retina: detects light and sends signals to brain
Macula: acuity is very good
Fovea: small put within macula; best acuity.. ONLY CONES(color) .. Rods(night vision,
!no color)
Optic Nerve: connects eye to brain
Vitreal Floaters: debris too large for phagocytic consumption; dead cells not broken up
!yet, blocking ray of light so you see a shadow floating in vitreous.

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- How far we see, depends on how far light travels.. we are all literally living in virtual
- If you are invisible, you would not be able to see anything either b/c light would not
enter eye.
Blind Spot: no rods or cones, therefore no mechanism to sense light
Pigment Epithelium: layer of cells containing enzymes that help remove worn out discs
!from receptors and helps process of pigment regeneration; allows us to see
!things. Without rods/cones being in back, we would not see because the rods/
!cones would be dead/worn out.
Rods: cannot see color; low spatial resolution, sensitive to light; corner of eye, periphery
!is only rods
Cones: high spatial resolution; allow us to see color
Receptive Field: area on sensory surface that neuron will respond to when stimulated
Lateral Inhibition: interaction between opposing responses of connected neurons.
!Inhibition is spread laterally across a nerve circuit.
Thrichromatic Theory: vision depends on 3 types of receptors, each sensitive to different
!wavelengths of light. Cones are maximally sensitive to : blue(419 nm), green(531
!nm), red(558 nm).. Not actually how vision works
Opponent-process theory: perception of colour is determined by activity of 2 opponent
!process mechanisms.
Negative after-image: stare at image, see image when you look at blank area.
Dorsal Stream (above): “where” pathway. If damaged, ID is ok, spacial defects.. goes to
!parietal lobe
Ventral Stream (below): “what” pathway. If damaged, Spatial is ok, canʼt ID things.. goes
!to temporal lobe
EYE --> Optic Nerve --> Lateral Geniculate Nucleus --> Visual Cortex
Cerebral Achromatopsia: canʼt see color
Visual Form Agnosia: canʼt ID objects
Optic Ataxia: canʼt reach for objects
Motion Agnosia: canʼt perceive motion, but can see objects
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