Final Exam Review Notes Flashcards
What is Psychophysics?
Relates individual’s mental experience (Psyche) with stimulus
energy (Physics)
Experimental psychology applied to perception
– Present stimulus
– Query subject on their perception
What is the method of constant stimuli
- Randomly present many stimuli of varying intensities
* Find the least intense stimulus the participant can detect
What is the method of limits
- Stimuli aren’t presented randomly
* Constantly increasing then decreasing
What is the method of adjustment
• Participant adjusts stimulus level
What is the method of magnitude estimation
• Participant assigns intensity rating to stimuli
What is Weber’s Law
The Just Noticeable Difference (JND) between two stimuli is a
constant proportion of stimulus intensity
– e.g. when comparing weights that were 10g, participants
could detect a 1g change, but if the weights were 100g, then
a 10g difference was the smallest
• The JND was always one tenth, a constant proportion
What is Fechner’s Law?
• We are less sensitive to stimulus change as the stimuli
become more intense
– Our perception of stimulus difference grows slower than
stimulus intensity
• Just says Weber’s law in a different way
– As the overall intensity I gets bigger, the JND ΔI has to get
bigger too to keep the constant K the same.
Stevens’ Power Law
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• Fechner put this in a mathematical formula
Fechner’s Law
• We are less sensitive to stimulus change as the stimuli
become more intense
– Our perception of stimulus difference grows slower than
stimulus intensity
• Just says Weber’s law in a different way
– As the overall intensity I gets bigger, the JND ΔI has to get
bigger too to keep the constant K the same.
What is Steven’s Power Law
• Steven’s found some violations of Fechner’s law and revised
the log function to the more general exponential function
• Sensation is exponentially related to stimulus intensity
– Sign of exponent determines shape of curve
• Green: b > 1
• Blue: b = 1
* Red: b < 1
What is signal detection theory
• Perceptual Sensitivity – Our ability to distinguish signal from signal+noise is our perceptual sensitivity • Called d’ (“dee prime”) – The better we can distinguish signal, the higher our d’ • Response Criterion – We set some level of perceptual certainty as our response criterion • Above that level of perceptual certainty, we respond "target" • Below we don't • Four types of responses – Two correct • Hits – target present and response • Correct rejections – target not present, no response – Two incorrect • Missed targets – target present, no response • False alarms – target not present, response Receiver Operating Curve • Plots hits (correct responses to targets) vs. false alarms (responding ‘target’ when no target is there) for given 4 5 6 1 2 7 4/18/14 3 • Hits – target present and response • Correct rejections – target not present, no response – Two incorrect • Missed targets – target present, no response • False alarms – target not present, response
What is Receiver Operating Curve
• Plots hits (correct responses to targets) vs. false alarms
(responding ‘target’ when no target is there) for given
perceptual sensitivities
– Each curve has the same perceptual sensitivity
– Different places on a curve reflect different response biases
• Lower left is very careful to not make any false alarms, at
the cost of missing targets
• Upper right you don’t miss many targets but you get lots of
false alarms
• Upper left is a balance between the two
What are sensory transducers?
• Transforms environmental stimuli to electrochemical activity in the brain – Light • Photons – Sound • Waves of compressed and rarified air – Touch • Mechanical deformation of the skin – Taste & Smell • Chemicals (odorants & tastants)
What is the brain structure for the hind and midbrain? and what do they do?
• Hindbrain – Medulla • Respiration – Cerebellum • Motor – Pons • Arousal – Reticular activating system • Midbrain – Tectum • Superior colliculus – Optic tectum » Visual orienting 7 8 9 1 2 4/18/14 4 – Medulla • Respiration – Cerebellum • Motor – Pons • Arousal – Reticular activating system • Midbrain – Tectum • Superior colliculus – Optic tectum » Visual orienting • Inferior colliculus – Auditory tectum » Auditory orienting – Tegmentum • Pain regulation – Periaquiductal gray
What is in the forebrain? and what do they do?
• Thalamus – Sensory relay • Lateral Geniculate – Visual • Medial Geniculate – Auditory • Ventral Posterior – Somatosensation – Taste • Medial Dorsal – Smell • Basal Ganglia – Motor – Motivation • Limbic System – Emotion • Cortex – Primary & secondary sensory cortex • Perception – Motor cortex – Association cortex • Puts multiple modalities together Cortical Lobes • Occipital – Visual 2 10 1 2 11 1 4/18/14 5 • Limbic System – Emotion • Cortex – Primary & secondary sensory cortex • Perception – Motor cortex – Association cortex • Puts multiple modalities together
What is in the cortical lobe? and what do they do?
• Occipital – Visual • Parietal – Posterior • Visual “where” or “perception for action” • Association – Anterior • Somatosensation • Temporal – Inferior • Visual “what” or “perception for recognition: – Superior • Auditory • Language reception – Medial • Some smell (primitive) • Frontal – Motor – Language production – Smell
what are neurons? what is basic neuron structure? what do neurons do? What are the different types of neurons
• Basic neuron structure – Soma (cell body) • Metabolic center – Dendrites • Primary input to cell – Axon • Output pathway (nerves are bundles of axons) – Single output from soma – Multiple terminal branches (sometimes thousands) – Myelin sheath • Insulates axon – Terminal buttons • Output terminal • Types of neuron 11 1 2 12 1 2 4/18/14 6 • Metabolic center – Dendrites • Primary input to cell – Axon • Output pathway (nerves are bundles of axons) – Single output from soma – Multiple terminal branches (sometimes thousands) – Myelin sheath • Insulates axon – Terminal buttons • Output terminal • Types of neuron – Unipolar • One process from cell body • Sensory, primarily touch and pain – Bipolar • Two processes • Primarily sensory transduction – Multipolar • Multiple processes • Many different configurations • Ubiquitous in nervous system • Synapse – Small gap between neurons across which they communicate • Axo-dendritic • Axo-somatic • Axo-axonic • Dendro-dendritic
What are proteins in the neuron skin?
• Channel proteins
– Allow charged particles (ions) to flow in and out of neuron
• Chemically gated
– Ionotropic receptors
– Open in response to neurotransmitter binding
• Electrically gated
– Open in response to change in membrane potential
• Signal proteins
– Metabotropic receptors
• Initiates metabolic change inside neuron
– May produce second messenger
– May change the structure or function of the neuron or
synapse
Resting Potential
• The inside or a neuron is about -70 mV compared to outside
• Due to differential distribution of ions between the inside and
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– Open in response to neurotransmitter binding
• Electrically gated
– Open in response to change in membrane potential
• Signal proteins
– Metabotropic receptors
• Initiates metabolic change inside neuron
– May produce second messenger
– May change the structure or function of the neuron or
synapse
What is a neurons resting potential? What is resting potential?
• The inside or a neuron is about -70 mV compared to outside • Due to differential distribution of ions between the inside and outside – A- (large protein anions) • Negative charge • All inside cell • Primary source of resting potential – Na+ (sodium) ions • Positive charge • More outside cell • Does rising phase of action potential – K+ (potassium) ions • Positive charge • More inside cell • Does falling phase of action potential – Cl- (chloride) ions • Negative charge • More outside cell • Post-synaptic potentials
What is an action potential? how does one work?
• Depolarize the membrane from resting potential to threshhold – ~ -60mV • Voltage gated Na+ channels open – Na+ ions flow in – Membrane potential rises towards 40 mV • Na+ equilibrium potential • During rise, voltage gated K+ channels open – K+ flows out, slowing rise • At peak (40 mV) Na+ channels close – Na+ can’t flow in any more – K+ continues to flow out – Membrane potential falls towards -80 mV • K+ equilibrium potential • K+ channels close on the way down – Stops negative voltage fall • Excess negative charge dissipates 2 14 1 2 15 1 2 4/18/14 8 – Na+ ions flow in – Membrane potential rises towards 40 mV • Na+ equilibrium potential • During rise, voltage gated K+ channels open – K+ flows out, slowing rise • At peak (40 mV) Na+ channels close – Na+ can’t flow in any more – K+ continues to flow out – Membrane potential falls towards -80 mV • K+ equilibrium potential • K+ channels close on the way down – Stops negative voltage fall • Excess negative charge dissipates – Restores resting potential
What is synaptic transmission?
• Action potential travels down axon to terminal button
• Vesicles (little packages of chemicals) in button merge with
the cell membrane, dumping their contents (neurotransmitters)
into the synapse
• Transmitter molecules diffuse across the synaptic cleft
• Bind with receptor proteins in the postsynaptic membrane
– Ionotropic receptors
• Chemically gated ion channels
– Metabotropic receptors
• Second messenger systems
• Alter function and/or structure of receiving neuron
• Termination
– Deactivation
• Enzymes break transmitter down
– Reuptake
• Transmitter taken back up into sending neuron
Explain light in terms of perception
• Light as Particles
– Light behaves like discrete packets
• Photons
– Each photon is one quanta (piece) of light
• Light as Waves
– Light behaves like undulations in a medium
• Like waves in the ocean
• The visual system is sensitive to a small part of the
electromagnetic spectrum
– ~400 - 700 nm
– Different wavelengths of light correspond (under certain
conditions) to different perceived colors
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• Light as Particles
– Light behaves like discrete packets
• Photons
– Each photon is one quanta (piece) of light
• Light as Waves
– Light behaves like undulations in a medium
• Like waves in the ocean
• The visual system is sensitive to a small part of the
electromagnetic spectrum
– ~400 - 700 nm
– Different wavelengths of light correspond(under certain
conditions) to different perceived colors
What are our eyes? How do they work? What are the different parts of the eye and what do they do?
• A biological analog camera for focusing images (the proximal stimulus) of the distal stimulus (object) on the transducers (rods and cones in the retina) • Pupil – Controls amount of light allowed in • Lens – Focuses on close or distant objects • Accommodation – Change in shape of lens • Retina – Location of photosensitive receptors
What different kinds of cells are in the retina and what do they do?
• Rods & Cones – Phototransducers – At back of retina • Horizontal cells – Connect between transducers and bipolar cells – Provide convergence and lateral inhibition • Bipolar cells – Connect transducers to projection neurons • Retinal ganglion cells – Translate inhibition to excitation • Amacrine cells – Between bipolars & ganglion cells – Function unknown • Retinal ganglion cells – Carry signal to brain – Axons make up optic nerve Phototransduction • Rhodopsin – Rod photopigment – 2 submolecules 1 2 18 19 1 2 20 1 4/18/14 10 • Retinal ganglion cells – Translate inhibition to excitation • Amacrine cells – Between bipolars & ganglion cells – Function unknown • Retinal ganglion cells – Carry signal to brain – Axons make up optic nerve
What is phototransduction and how does it work?
• Rhodopsin – Rod photopigment – 2 submolecules • Opsin • Retinal (2 isomers) – 11-cis retinal – All-trans retinal • 1 photon of light converts one molecule of retinal from 11-cis to all trans isomer • Phototransduction is initially inhibitory – In the dark • Rhodopsin inactive • NA+ channels open • NA+ flows in, depolarizing membrane • Transmitter released – In the light • Rhodopsin active • NA+ channels close • NA+ flow blocked • Transmitter release stopped
What are lateral inhibition and mach bands? How do they work?
• Physical World
– Patches of uniform intensity adjacent to patches of different
intensity
• Psychological Response
– Perception of lighter and darker intensity bands at patch
boundaries
• Cognitive Model
– A computational network of convergent input with lateral
inhibition
• Biological Substrate
– The retinal mosaic has horizontal cells connected between
receptors and ganglion cells to provide convergence with
lateral inhibition
Retinal Ganglion and Lateral Geniculate Receptive Fields
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intensity
• Psychological Response
– Perception of lighter and darker intensity bands at patch
boundaries
• Cognitive Model
– A computational network of convergent input with lateral
inhibition
• Biological Substrate
– The retinal mosaic has horizontal cells connected between
receptors and ganglion cells to provide convergence with
lateral inhibition
What is the retinal ganglion and lateral geniculate receptive fields? How do they work?
• Retinal Ganglion Cells project to the Thalamus
– Lateral Geniculate Nucleus
• A Neuron’s Receptive Field
– That part of the visual field that can change the firing rate of
the cell (up or down) if the proper stimulus falls within it
• Retinal Ganglion and Lateral Geniculate cells respond best to
dots of light with a center/surround organization
– On-center/ Off-surround
– Off-center/ On-surround• Retinal Ganglion Cells project to the Thalamus
– Lateral Geniculate Nucleus
• A Neuron’s Receptive Field
– That part of the visual field that can change the firing rate of
the cell (up or down) if the proper stimulus falls within it
• Retinal Ganglion and Lateral Geniculate cells respond best to
dots of light with a center/surround organization
– On-center/ Off-surround
– Off-center/ On-surround`
What is the primary visual cortex of neurons? What different types of cells are in it and how do they work?
• Simple Cells – Oriented bars of light – Center surround • Complex Cells – Oriented bars of light – Moving in one, but not the other, direction – Not center surround • Hypercomplex Cells – Corner or end-stop cells – Oriented bars of light but only if end of bar is in receptive field • Hubel & Weisel’s model • A serial hierarchic model – Converge LGN input to make simple cell – Converge simple cell input to make complex cell – Converge complex cell input to make hypercomplex cell • Logically leads to ‘grandmother’ cell – Neuron that responds to one specific visual object • e.g. your grandmother Current Model • Parallel (rather than serial) – Multiple operations at once • Hierarchic 2 23 1 2 24 1 2 25 4/18/14 12 • Hubel & Weisel’s model • A serial hierarchic model – Converge LGN input to make simple cell – Converge simple cell input to make complex cell – Converge complex cell input to make hypercomplex cell • Logically leads to ‘grandmother’ cell – Neuron that responds to one specific visual object • e.g. your grandmother
What is the current model for how vision works?
• Parallel (rather than serial) – Multiple operations at once • Hierarchic – Build complex out of simple • Functionally segregated – Separate parts of the brain do different things
