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Sensory Processes 3270 Lecture 4 Slide 2 KEYWORDS from Lecture 3 Psychophysics Fechner, Weber, Threshold, Method of limits, staircase, Method of constant stimuli, two alternative forced choice, method of adjustment Signal detection theory, threshold as probability, sensitivity versus response bias, criterion, outcome matrix, hit/miss/false alarm or false positives/correct rejection, receiver operating characteristic curves (ROC curves), sensitivity, d-prime (d') Just noticeable difference, Weber fraction/law/constant, Fechner's law, Stevens' power law, magnitude estimation, standard stimulus, response compression, response expansion Slide 3 The difference threshold just noticeable difference (jnd) Webers law (1834) the just noticeable increment is a constant fraction of the stimulus Weber Fractions Taste0.08 8% Brightness0.088% Loudness0.055% Vibration0.044% Line length0.033% Heaviness0.022% Electric shock0.011% Fechners law (1860) sensation magnitude proportional to logarithm (stimulus intensity) assumption: all jnds are the same stood for 100 years! Stevens law (1961) (To honour Fechner and repeal his law) sensation magnitude proportional to (stimulus intensity) raised to a power Slide 4 Ernst Weber (1795-1878) Increase in intensity Intensity = constant Slide 5 Response compression Response expansion Slide 6 Gustav Fechner (1801-1887) Perceived magnitude Log (intensity) Slide 7 S.S. Stevens (1906-1973) Perceived magnitude (intensity) h Slide 8 Slide 9 Consequences of Stevens Law response compression response expansion linear on a log scale Slide 10 Somatosensory System section 3 Slide 11 Why? Perception--- body parts (proprioception) --- touch --- special --vibrissae antennae pain braille temperature Protection Temperature regulation Limb arrangement and control Head orientation (vestibular system) somatosensory Slide 12 How? Receptors Neural pathways Neural codes (remember those common features) somatosensory Slide 13 Coding in the somatosensory system detection identify modality (Mller's doctrine of specific nerve energies 1826; labelled lines); identify properties and spatial form magnitude intensity (APs/sec; frequency coding; population coding; thresholds); location (absolute, two-point discrimination, topographical coding) movement Slide 14 GLABROUS (non-hairy) SKIN MEISSNERS CORPUSCLE (RA) MERKELS DISK (SA) RUFFINI CORPUSCLE (SA) PACINI CORPUSCLE (very RA) Slide 15 MERKELS DISK (SA) Free nerve ending PACINI CORPUSCLE (very RA) Nerve ending around hair (RA) HAIRY SKIN MEISSNERS CORPUSCLE (RA) RUFFINI ENDING (SA) Slide 16 SA RA SA Slide 17 RA SA very RA SA Slide 18 stretching vibration fine detail hand grip control Slide 19 SPATIAL EVENT PLOTS SA (Merkel) RA (Meissner) RA (Pacinian) Slide 20 Slide 21 MERKEL (SA) PACINIAN (vRA) Slide 22 Somatosensory pathway Trigeminal system from face DORSAL COLUMNS 1st 2nd 3rd 4th CROSS OVER IN BRAIN STEM VENTRAL POSTERIOR LATERAL Nucleus of the thalamus SOMATOSENSORY CORTEX Slide 23 Slide 24 Slide 25 After a limb has been amputated, phantom sensations can sometimes be created by stroking other areas of skin. Slide 26 Demonstrates: 1 plasticity, 2 Mllers law of specific nerve energies Slide 27 Area of somatosensory cortex representing finger tip stimulate finger tip over many days Larger area now devoted to this finger tip DEMONSTRATES PLASTICITY Slide 28 PRESSURE THRESHOLDS Dont vary much Slide 29 POINT LOCALIZATION THRESHOLDS Slide 30 Slide 31 RECEPTIVE FIELDS ON THE ARM Slide 32 Afferent fibres SA RA PC Cortical cells in area 3b (SA) Slide 33 Slide 34 Lateral inhibition improves 2-point discrimination Slide 35 Somatosensory pathways 3a 3b 1 2 5 4 Trigeminal system from face DORSAL COLUMNS CROSS OVER Slide 36 3a 3b 1 2 5 4 Multiple representations 3a -- muscle spindles 3b -- SA (cutaneous) 1 ---- RA (cutaneous) 2 ---- joints Slide 37 LIMB SENSING ORGANS Muscle spindles, cutaneous mechanoreceptors and joint receptors cutaneous mechanoreceptors Muscle spindles Joint receptors Slide 38 3a 3b 1 2 5 4 Multiple representations 3a -- muscle spindles 3b -- SA (cutaneous) 1 ---- RA (cutaneous) 2 ---- joints Slide 39 Slide 40 Secondary Somatosensory cortex Secondary Somatosensory cortex Multiple representations 3a -- muscle spindles 3b -- SA (cutaneous) 1 ---- RA (cutaneous) 2 ---- joints Slide 41 Slide 42 superior colliculus Slide 43 Superior Colliculus Slide 44 Superior Colliculus Slide 45 Active vs passive touch active object passive sensation identifying cookies cutters active 95% correct passive 49% correct Slide 46 judged as same could distinguish JUDGING TEXTURE Slide 47 Meissners RA Pacinian vRA Meissners RA Pacinian vRA Meissners RA Pacinian vRA Slow freqnoneHigh freq ADAPT Slide 48 chance DEMONSTRATES THAT VIBRATION NEEDED FOR TEXTURE POST-ADAPT Slide 49 explore surface texture with tool demonstrates use of vibration Slide 50 haptic perception Stereognosis: 3d object perception by haptic exploration Slide 51 Slide 52 Slide 53 Slide 54 SA RA SA BARE NERVE ENDINGS Slide 55 TEMPERATURE Normal = 34 Cold 5-40 Warm 30-45 Ratio (channel) coding Paradoxical cold at high temps cold fibres warm fibresbody temp skin temp response Slide 56 PAIN pain insensitivity = bad referred pain (eg. Angina to chest wall) sharp 1st followed by dull 2nd GATE theory (why rubbing helps) Slide 57 To brainThe Gate -ve+ve -ve +ve Slow pain fibres Fast mechano-receptor fibres Closed by rubbing So pain stopped from going to brain... Normally held closed Opened by pain fibres -ve Slide 58 phantom limb pain Acupuncture Hypnosis Expectation (cognitive factors) endorphins and enkephalins (natural opiates) Naloxone (antagonist) makes pain worse also reverses acupuncture endorphins up with stress.. PAIN pain insensitivity = bad referred pain (eg. Angina to chest wall) sharp 1st followed by dull 2nd GATE theory (why rubbing helps) Slide 59 Sensation and Perception II 3270 Revision For first midterm Slide 60 Electrode, Microelectrode, Micron (1/1000th mm), membrane, nucleus, cytoplasm, Neuron, axon, dendrite, Schwann cell/glial cell, myelin sheath, node of Ranvier, Synapse, synaptic cleft, vesicle, neurotransmitter, receptors, ions, permeability, ion channels, voltage-dependent sodium channels, neural threshold, positive feedback, sodium (Na+), potassium (K+), sodium-potassium pump, electrochemical equilibrium potentials, sodium (Na+) +55mv, potassium (K+) -75mv, resting potential -70mv, polarization/ depolarization/ hyperpolarization, inhibitory post-synaptic potential (IPSP), Excitatory post-synaptic potential (EPSP), integration, axon hillock, action potential (AP), all-or- none, neuron threshold -55mv, saltatory propagation, AP propagation KEYWORDS from NEURAL BASIS Slide 61 modality (Mller's doctrine of specific nerve energies 1826; labelled line); intensity (APs/sec; frequency coding; population coding; thresholds); duration (rapidly and slowly adapting neurones) location (absolute, two-point discrimination, topographical coding) Pacinian corpuscle Slide 62 KEYWORDS from NEURAL BASIS receptive fields, thalamus, cortex, sulcus, gyrus, brainstem, topographic (maps) representation, superior colliculus, inferior colliculus (those are the names of the bumps on the brain stem that deal with vision and hearing respectively), Brodmann, phrenology, areas of cortex: primary sensory areas (chemical, somatosensory, visual, auditory), motor cortex, association cortices (parietal, inferotemporal, frontal) Slide 63 KEYWORDS from PSYCHOPHYSICS Fechner, Weber, Threshold, Method of limits, staircase, Method of constant stimuli, two alternative forced choice, method of adjustment Signal detection theory, threshold as probability, sensitivity versus response bias, criterion, outcome matrix, hit/miss/false alarm or false positives/correct rejection, receiver operating characteristic curves (ROC curves), sensitivity Just noticeable difference, Weber fraction/law/constant, Fechner's law, Stevens' power law, magnitude estimation, standard stimulus, response compression. Slide 64 Receptors, hairy/glabrous skin, rapidly/slowly adapting (RA/SA), transduction, Meissner's corpuscles (RA), Merkel's discs (SA), Nerve ending around hair (RA), Pacinian corpuscle (RA), Ruffini Ending (SA), free nerve endings, receptive fields, dorsal root, dorsal columns, dorsal column nuclei, trigeminal nerve, thalamus, somatosensory cortex, homunculus, somatotopic representation/map spatial event plots, lateral inhibition, sharpening of receptive fields cortex, Brodmann areas 3a, 3b, 1, 2. Joint detectors, muscle spindles, RAs, SAs, convergence Secondary somatosensory cortex Keywords for SOMATOSENSORY SYSTEM Slide 65 KEYWORDS from SOMATOSENSORY 1 detection 2 identify (modality) 3 identify (properties, spatial form) 4 magnitude 5 location 6 movement which fibre?, mapping of location, identifying modality/ sub- modality what pattern? frequency coding of magnitude Slide 66 somatosensory psychophysics, detection thresholds, point threshold, two-point discrimination (larger than point thresholds because of need for unstimulated receptive field in between stimuli), texture perception: vibration and active motion important stereognosis, Haptic perception, variations over body surface, active touch/exploration, stereognosis, Aristotle's illusion, Temperature Pain (perception), Slide 67 As promised.. The following is a question that will appear on the midterm next week (no, I did not promise to ANSWER it too.! GOOD LUCK! Slide 68 A question from next weeks exam There will be 35 multiple choices: 1 point each = 91% There will be one label the diagram: 3.5 points= 9% Total = 38.5 points = 100% Counts for 30% or 40% if it is your best.