Sensory Processes 3270 Lecture 4 KEYWORDS from Lecture

Sensory Processes 3270 Lecture 4

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

The difference threshold • just noticeable difference (jnd) • Weber’s law (1834) the just noticeable increment is a constant fraction of the stimulus • Fechner’s law (1860) Weber Fractions sensation magnitude Taste proportional to 0. 08 logarithm (stimulus. Brightness intensity) 0. 08 assumption: all jnd’s are the same Loudness 0. 05 stood for 100 years! Vibration 0. 04 • Steven’s law (1961) Line length 0. 03 (“To honour Fechner and. Heaviness repeal his law”) 0. 02 sensation magnitude proportional to Electric shock 0. 01 (stimulus intensity) raised to a power 8% 8% 5% 4% 3% 2% 1%

Increase in intensity = constant Intensity Ernst Weber (1795 -1878)

Response compression Response expansion

Perceived magnitude Gustav Fechner (1801 -1887) Log (intensity)

Perceived magnitude S. S. Stevens (1906 -1973) (intensity) h

Consequences of Steven’s Law • response compression • response expansion • linear on a log scale

Somatosensory System section 3

Why? • Perception --- body parts (proprioception) --- touch --- special -- vibrissae antennae pain braille temperature • Protection • Temperature regulation • Limb arrangement and control • Head orientation (vestibular system) somatosensory

How? • Receptors • Neural pathways • Neural codes (remember those ‘common features’…) somatosensory

Coding in the somatosensory system • detection • identify modality (Müller'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

MEISSNER’S CORPUSCLE (RA) MERKEL’S DISK (SA) RUFFINI CORPUSCLE (SA) PACINI CORPUSCLE (very RA) GLABROUS (non-hairy) SKIN

MEISSNER’S CORPUSCLE (RA) MERKEL’S DISK (SA) Free nerve ending HAIRY SKIN Nerve ending around hair (RA) PACINI CORPUSCLE (very RA) RUFFINI ENDING (SA)

SA RA

RA SA very RA SA

fine detail stretching hand grip control vibration

SPATIAL EVENT PLOTS SA (Merkel) RA (Meissner) RA (Pacinian)

MERKEL (SA) PACINIAN (v. RA)

SOMATOSENSORY CORTEX 4 th Trigeminal system from face CROSS OVER IN BRAIN STEM DORSAL COLUMNS 1 st 3 rd VENTRAL POSTERIOR LATERAL Nucleus of the thalamus 2 nd Somatosensory pathway

After a limb has been amputated, “phantom” sensations can sometimes be created by stroking other areas of skin.

Demonstrates: 1 plasticity, 2 Müller’s law of specific nerve energies

Area of somatosensory cortex representing finger tip stimulate finger tip over many days Larger area now devoted to this finger tip DEMONSTRATES PLASTICITY

PRESSURE THRESHOLDS Don’t vary much

POINT LOCALIZATION THRESHOLDS

RECEPTIVE FIELDS ON THE ARM

Afferent fibres SA RA PC Cortical cells in area 3 b (SA)

Lateral inhibition improves 2 -point discrimination

Trigeminal system from face CROSS OVER 1 4 3 b 2 5 3 a DORSAL COLUMNS Somatosensory pathways

Multiple representations 1 4 3 b 3 a 2 5 3 a -- muscle spindles 3 b -- SA (cutaneous) 1 ---- RA (cutaneous) 2 ---- joints

cutaneous mechanoreceptors Muscle spindles Joint receptors LIMB SENSING ORGANS Muscle spindles, cutaneous mechanoreceptors and joint receptors

Multiple representations 1 4 3 b 3 a 2 5 3 a -- muscle spindles 3 b -- SA (cutaneous) 1 ---- RA (cutaneous) 2 ---- joints

Secondary Somatosensory cortex Multiple representations 3 a -- muscle spindles 3 b -- SA (cutaneous) 1 ---- RA (cutaneous) 2 ---- joints Secondary Somatosensory cortex

superior colliculus

Superior Colliculus

Superior Colliculus

Active vs passive touch active “object” passive “sensation” identifying cookies cutters active 95% correct passive 49% correct

could distinguish judged as same JUDGING TEXTURE

ADAPT none Meissner’s RA Pacinian v. RA Slow freq Meissner’s RA Pacinian v. RA High freq Meissner’s RA Pacinian v. RA

POST-ADAPT chance DEMONSTRATES THAT VIBRATION NEEDED FOR TEXTURE

explore surface texture with tool demonstrates use of vibration

haptic perception Stereognosis: 3 d object perception by haptic exploration

SA RA BARE NERVE ENDINGS

TEMPERATURE response • Normal = 34 • Cold 5 -40 • Warm 30 -45 • Ratio (channel) coding • Paradoxical cold at high temps body temp cold fibres skin temp warm fibres

PAIN • pain insensitivity = bad • referred pain (eg. Angina to chest wall) • sharp 1 st followed by dull 2 nd • GATE theory (why rubbing helps)

Slow pain fibres The Gate -ve +ve To brain -ve +ve Fast mechano-receptor fibres +ve • Normally held closed • Opened by ‘pain fibres • Closed by ‘rubbing’ • So pain stopped from going to brain. . .

PAIN • pain insensitivity = bad • referred pain (eg. Angina to chest wall) • sharp 1 st followed by dull 2 nd • GATE theory (why rubbing helps) • 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. .

Sensation and Perception II 3270 Revision For first midterm

KEYWORDS from NEURAL BASIS Electrode, Microelectrode, Micron (1/1000 th 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+) +55 mv, potassium (K+) -75 mv, resting potential -70 mv, polarization/ depolarization/ hyperpolarization, inhibitory post-synaptic potential (IPSP), Excitatory post-synaptic potential (EPSP), integration, axon hillock, action potential (AP), all-ornone, neuron threshold -55 mv, saltatory propagation, AP propagation

KEYWORDS from NEURAL BASIS • modality (Müller'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

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)

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.

Keywords for SOMATOSENSORY SYSTEM 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 3 a, 3 b, 1, 2. Joint detectors, muscle spindles, RAs, SAs, convergence Secondary somatosensory cortex

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/ submodality what pattern? frequency coding of magnitude

• 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),

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!

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. A question from next week’s exam