PYB102 Introduction to Psychology 1b Week 2 Lecture
PYB102 Introduction to Psychology 1b Week 2 Lecture Perception • perceptual psych. study the way we acquire info about the world via our various senses • bulk of perceptual research has been conducted in vision and audition domains
Vision
Light • for an object to be visible, it must emit or reflect light • The human eye is only capable of detecting light within a narrow range of wavelengths • Within this range of visible wavelengths, different wavelengths give rise to the perception of different colours
Gross anatomy of the eye • The pupil changes in diameter (dilates) to accommodate changes in lighting • Light is detected by receptors called rods and cones located at back of retina • Schultze proposed that rods and cones form two separate visual systems (Duplex Retina Theory); • Photopic: Bright light vision via cones • Scotopic: Dim light vision via rods • Von Kries (1895) observed that individuals without rods were night blind. • The reverse applies for individuals without cones
Normal colour vision in humans is trichomatic: Cones can contain either L (long), M (medium) or S (small). ←
• All the colours which you can see are due to this combination of signalling by rods and cones • Some animals have more advanced colour vision than humans ←
Colour deficiencies • Retinal "colour blindness" occurs in 8% of the male population (x-linked), neutral> congruent Reading is an automatic task o Semantic meaning of the words takes priority o Semantic interference occurs when asked to name the incongruent colour of the text o Colour naming is not automated -> additional cognitive load required which increases RT o Semantic facilitation when asked to name the congruent colour of the text, RT decreases
Taste • Sapid (tastable) substances must generally by water soluble • Most researches agree that there are four basic tastes: • Sweet, Sour, Bitter, Salty • Other researchers suggest metallic and unami (savoury) • These primary tastes are associated with substances w/ particular chemical properties Swe Generally associated with organic molecules like sugars & et alcohols. Many sweet substances (including non- organic ones) contain a component consisting of two negatively charged atoms and a positively charged hydrogen atom (AB,H system) Sour
Generally associated with acids
Bitte r
Often taste sweet in small amounts and often contain an AB,H system many bitter substances contain nitrogen
Salt y
Salty substances break into two electrically charged parts (ions) when dissolved they size of the negative ion determines the saltiness (lighter = more salty)
Overview of taste physiology Transduction of this chemical information into electrical signals occurs in taste buds: • Located in pits around papillae on the tongue, and on the soft palate • ~10000 taste buds, decreases with age • Taste buds contain a number (~50-150) of taste cells • Taste cells terminate in microvilli which project into the taste pore • Microvilli seem to be the site of reception for chemicals • Taste cells are replaced every few days • Nerve fibres exit from the back of the taste cells
Models of taste coding Most taste receptors seem to respond to all 4 basic tastes, although with different sensitivities (Kimura & Beidler, 1961) • The cross-fiber patterning model (e.g., Pfaffman, 1955) argues that each substance we can taste generates a different pattern of activity across nerve fibres leading to different taste perceptions • Erickson (1963) noted that the pattern for potassium chloride and ammonium chloride are similar but that for sodium chloride is different; • Groups of rats fed one of these accompanied by an electric shock o KCl rats subsequently avoided NH4CL and visa versa, but the NaCl rats did not avoid either of the other 2 salts o Thus pattern of neural activity seems to correlate with taste The labelled-line theory (Pfaffman, 1974); • Assumes a best stimulus model of nerve fibre activity where specific fibres encode one of the four basic tastes depending on the one they respond most strongly to o The taste of a substance is thus given by the pattern of activity across these four types of fibres o This is a more constrained version of cross-fiber patterning • Perhaps taste uses both mechanisms; o Labelled line mechanism differentiate between taste categories o Cross-fiber patterning to differentiate within taste categories
Olfactory stimuli • • • • •
Olfactory stimuli must be volatile and soluble in both water and lipids Not all substances which meet these criteria smell Most odorous substances are organic There is no clear classification of primary odours amongst the 10000 (or so) odour we can discriminate Olfaction seems to work in two modes; o as an adjunct to the perception of food flavour o as a "distnce sense" to gather info about stimuli in the environment many species secrete volatile chemicals (pheromones) to convey messages to others
Olfactory Physiology • •
• • • •
• • • •
Olfactory cilia are the site of transduction for smell The number of cilia per receptor and the number of receptors determine sensitivity to odours; o Dog: 200 million receptors with 100-150 cilia each o Human: 10 million receptors with 6-8 cilia each o The mucus surrounding the olfactory cilia contains a protein called olfactory binding protein (OBP) OBP may attach to odourant molecules and transport them to the receptors in the cilia There are at least two ways that odourants cause a neural response; Specific receptor proteins o Cyclic adenosine monophosphate (cAMP) is produced via a complex chain of chemical events when an odorant is encountered o The presence of cAMP allows positive sodium ions to flow into the cell o This depolarisation leads to action potentials A non-specific mechanism whereby various chemicals directly affect the cell membrane allowing ions to leak in The olfactory nerve passes through the cribiform plate to the olfactory bulb where complex clusters of connections called glomeruli form These cluster may be grouped according to the type of receptor or type of odorant molecule (Kauer, 1980, 1987) Two pathways leave the olfactory bulb; o One type of cell projects to the primary sensory cortex o Another type of cell projects to a range of sites in the lower brain These include the limbic system, which is involved in our memory and emotion
Pain (nociception)
• • • • • • • •
There is evidence that pain is a separate sensation; not simply the result of over stimulation of other modalities Mapping studies show regions which, when stimulated, only yield pain sensations Some individuals are completely pain-insensitive but have normal sensitivity to other skin stimuli Some researchers argue that pain is not a sensation but an emotion or bodily state akin to hunger or thirst Seems to be elicited by stimuli which are capable of damaging the body Seems to act as a survival mechanism; signals stimuli to be avoided now/in future induces appropriate behaviour; o initial lack of pain after serious injury facilitates flight o Pain during recovery phase promotes “rest” which may aid recovery o Pain-insensitive individuals often suffer repeated injuries o eg. biting the end of their tongue off and incurring orthopaedic injury through failure to control body posture
Pain cont. •
• •
The free nerve endings which seem sensitive to pain tend to respond only to “strong” stimuli; o Nerve endings in fat layer are shielded from weak stimuli o Nerve endings in epidermis are sheathed in Schwann cells which also act to filter weak stimuli Pain seems to be transmitted by different types of nerve fibres to those involved with other skin senses; Myelinated AB fibres (high transmission speeds: 40 m/s), follow both the lemniscal and spinothalamic pathways and respond well to “weak” (nonpain) stimuli
•
Myelinated Ab and unmyelinated C fibres (low transmission speeds: 2.5 20 m/s) are smaller and follow the spinothalamic pathway.
•
C fibres respond all noxious stimuli, A only to noxious mechanical stimuli.
•
These “pain” fibres project to the thalamus and areas SI and SII contralateral to the stimulated body site The double pain phenomena (Torebjork, & Hallin, 1973; Willis, 1985) highlights the operation of these two separate systems; A single painful stimulus invokes two separate sensations; o An initial sharp pain o A subsequent duller pain The initial sensation may be due to the response of the fast acting AB “touch” fibres The subsequent sensation may be due to the slower response from the Ab and C “pain” fibres
• • • • • •
Pain fibers project to the hypothalamus and areas SI and SII controlateral to the stimulated body site Somatosensory homunculus – sensory information
Melzack and Wall (1965, 1982) developed the gate-control theory of pain; • • • • • • • • •
Fast and slow fibers connect to the substantia gelatinosa and transmission cells (T-cells) in the spinal cord Fast fiber activity excites both these centres Slow fiber activity inhibits the substantia gelatinosa and excites the Tcells The substantia gelatinosa inhibits the T-cells Weak stimuli will thus inhibit the T-cells Strong stimuli will excite the T-cells The output of the T-cells determines pain signal strength The brain can control the activity of the gate system This model can explain why rubbing a wound reduces pain and why amputees suffer phantom pain
Phantom limb pain
o the sensation that an amputated limb, or organ is still attached to the body and is moving or behaving as it normally would o occurs in 60-80% of amputees o often painful sensations o Mirror therapy has proven useful
Multimodal Integration • Objects are perceived via multiple sensory modalities • Perceptual experiences require coherent representation of objects • e.g. eating a strawberry • The phsical world is a cacophony of noise (stimuli). • The problem of binding – how do we generate unified, coherent, stable percepts? • Theories of multimodal integration include • Visual dominance • Bayesian integration • Modality appropriateness • The superior colliculus in the midbrain contains maps of the visual, auditory and somatosensory senses
Synaesthesia
Condition’ in which stimulation of one sensory modality leads to an involuntary and automatic sensation of another sensory modality • Grapheme-colour: letters or numbers (graphemes) are perceived as coloured. Most common form • Lexical-gustatory: words/phonemes evoke tastes • Associations differ from person to person, even within subtypes, but are highly stable for an individual • Synaesthetes are often artistic, and percepts reported as neutral or even beneficial
• Strong environmental influence ← ←
Vision
Light • for an object to be visible, it must emit or reflect light • The human eye is only capable of detecting light within a narrow range of wavelengths • Within this range of visible wavelengths, different wavelengths give rise to the perception of different colours
Gross anatomy of the eye • The pupil changes in diameter (dilates) to accommodate changes in lighting • Light is detected by receptors called rods and cones located at back of retina • Schultze proposed that rods and cones form two separate visual systems (Duplex Retina Theory); • Photopic: Bright light vision via cones • Scotopic: Dim light vision via rods • Von Kries (1895) observed that individuals without rods were night blind. • The reverse applies for individuals without cones
Normal colour vision in humans is trichomatic: Cones can contain either L (long), M (medium) or S (small). ←
• All the colours which you can see are due to this combination of signalling by rods and cones • Some animals have more advanced colour vision than humans ←
Colour deficiencies • Retinal "colour blindness" occurs in 8% of the male population (x-linked), neutral> congruent Reading is an automatic task o Semantic meaning of the words takes priority o Semantic interference occurs when asked to name the incongruent colour of the text o Colour naming is not automated -> additional cognitive load required which increases RT o Semantic facilitation when asked to name the congruent colour of the text, RT decreases
Taste • Sapid (tastable) substances must generally by water soluble • Most researches agree that there are four basic tastes: • Sweet, Sour, Bitter, Salty • Other researchers suggest metallic and unami (savoury) • These primary tastes are associated with substances w/ particular chemical properties Swe Generally associated with organic molecules like sugars & et alcohols. Many sweet substances (including non- organic ones) contain a component consisting of two negatively charged atoms and a positively charged hydrogen atom (AB,H system) Sour
Generally associated with acids
Bitte r
Often taste sweet in small amounts and often contain an AB,H system many bitter substances contain nitrogen
Salt y
Salty substances break into two electrically charged parts (ions) when dissolved they size of the negative ion determines the saltiness (lighter = more salty)
Overview of taste physiology Transduction of this chemical information into electrical signals occurs in taste buds: • Located in pits around papillae on the tongue, and on the soft palate • ~10000 taste buds, decreases with age • Taste buds contain a number (~50-150) of taste cells • Taste cells terminate in microvilli which project into the taste pore • Microvilli seem to be the site of reception for chemicals • Taste cells are replaced every few days • Nerve fibres exit from the back of the taste cells
Models of taste coding Most taste receptors seem to respond to all 4 basic tastes, although with different sensitivities (Kimura & Beidler, 1961) • The cross-fiber patterning model (e.g., Pfaffman, 1955) argues that each substance we can taste generates a different pattern of activity across nerve fibres leading to different taste perceptions • Erickson (1963) noted that the pattern for potassium chloride and ammonium chloride are similar but that for sodium chloride is different; • Groups of rats fed one of these accompanied by an electric shock o KCl rats subsequently avoided NH4CL and visa versa, but the NaCl rats did not avoid either of the other 2 salts o Thus pattern of neural activity seems to correlate with taste The labelled-line theory (Pfaffman, 1974); • Assumes a best stimulus model of nerve fibre activity where specific fibres encode one of the four basic tastes depending on the one they respond most strongly to o The taste of a substance is thus given by the pattern of activity across these four types of fibres o This is a more constrained version of cross-fiber patterning • Perhaps taste uses both mechanisms; o Labelled line mechanism differentiate between taste categories o Cross-fiber patterning to differentiate within taste categories
Olfactory stimuli • • • • •
Olfactory stimuli must be volatile and soluble in both water and lipids Not all substances which meet these criteria smell Most odorous substances are organic There is no clear classification of primary odours amongst the 10000 (or so) odour we can discriminate Olfaction seems to work in two modes; o as an adjunct to the perception of food flavour o as a "distnce sense" to gather info about stimuli in the environment many species secrete volatile chemicals (pheromones) to convey messages to others
Olfactory Physiology • •
• • • •
• • • •
Olfactory cilia are the site of transduction for smell The number of cilia per receptor and the number of receptors determine sensitivity to odours; o Dog: 200 million receptors with 100-150 cilia each o Human: 10 million receptors with 6-8 cilia each o The mucus surrounding the olfactory cilia contains a protein called olfactory binding protein (OBP) OBP may attach to odourant molecules and transport them to the receptors in the cilia There are at least two ways that odourants cause a neural response; Specific receptor proteins o Cyclic adenosine monophosphate (cAMP) is produced via a complex chain of chemical events when an odorant is encountered o The presence of cAMP allows positive sodium ions to flow into the cell o This depolarisation leads to action potentials A non-specific mechanism whereby various chemicals directly affect the cell membrane allowing ions to leak in The olfactory nerve passes through the cribiform plate to the olfactory bulb where complex clusters of connections called glomeruli form These cluster may be grouped according to the type of receptor or type of odorant molecule (Kauer, 1980, 1987) Two pathways leave the olfactory bulb; o One type of cell projects to the primary sensory cortex o Another type of cell projects to a range of sites in the lower brain These include the limbic system, which is involved in our memory and emotion
Pain (nociception)
• • • • • • • •
There is evidence that pain is a separate sensation; not simply the result of over stimulation of other modalities Mapping studies show regions which, when stimulated, only yield pain sensations Some individuals are completely pain-insensitive but have normal sensitivity to other skin stimuli Some researchers argue that pain is not a sensation but an emotion or bodily state akin to hunger or thirst Seems to be elicited by stimuli which are capable of damaging the body Seems to act as a survival mechanism; signals stimuli to be avoided now/in future induces appropriate behaviour; o initial lack of pain after serious injury facilitates flight o Pain during recovery phase promotes “rest” which may aid recovery o Pain-insensitive individuals often suffer repeated injuries o eg. biting the end of their tongue off and incurring orthopaedic injury through failure to control body posture
Pain cont. •
• •
The free nerve endings which seem sensitive to pain tend to respond only to “strong” stimuli; o Nerve endings in fat layer are shielded from weak stimuli o Nerve endings in epidermis are sheathed in Schwann cells which also act to filter weak stimuli Pain seems to be transmitted by different types of nerve fibres to those involved with other skin senses; Myelinated AB fibres (high transmission speeds: 40 m/s), follow both the lemniscal and spinothalamic pathways and respond well to “weak” (nonpain) stimuli
•
Myelinated Ab and unmyelinated C fibres (low transmission speeds: 2.5 20 m/s) are smaller and follow the spinothalamic pathway.
•
C fibres respond all noxious stimuli, A only to noxious mechanical stimuli.
•
These “pain” fibres project to the thalamus and areas SI and SII contralateral to the stimulated body site The double pain phenomena (Torebjork, & Hallin, 1973; Willis, 1985) highlights the operation of these two separate systems; A single painful stimulus invokes two separate sensations; o An initial sharp pain o A subsequent duller pain The initial sensation may be due to the response of the fast acting AB “touch” fibres The subsequent sensation may be due to the slower response from the Ab and C “pain” fibres
• • • • • •
Pain fibers project to the hypothalamus and areas SI and SII controlateral to the stimulated body site Somatosensory homunculus – sensory information
Melzack and Wall (1965, 1982) developed the gate-control theory of pain; • • • • • • • • •
Fast and slow fibers connect to the substantia gelatinosa and transmission cells (T-cells) in the spinal cord Fast fiber activity excites both these centres Slow fiber activity inhibits the substantia gelatinosa and excites the Tcells The substantia gelatinosa inhibits the T-cells Weak stimuli will thus inhibit the T-cells Strong stimuli will excite the T-cells The output of the T-cells determines pain signal strength The brain can control the activity of the gate system This model can explain why rubbing a wound reduces pain and why amputees suffer phantom pain
Phantom limb pain
o the sensation that an amputated limb, or organ is still attached to the body and is moving or behaving as it normally would o occurs in 60-80% of amputees o often painful sensations o Mirror therapy has proven useful
Multimodal Integration • Objects are perceived via multiple sensory modalities • Perceptual experiences require coherent representation of objects • e.g. eating a strawberry • The phsical world is a cacophony of noise (stimuli). • The problem of binding – how do we generate unified, coherent, stable percepts? • Theories of multimodal integration include • Visual dominance • Bayesian integration • Modality appropriateness • The superior colliculus in the midbrain contains maps of the visual, auditory and somatosensory senses
Synaesthesia
Condition’ in which stimulation of one sensory modality leads to an involuntary and automatic sensation of another sensory modality • Grapheme-colour: letters or numbers (graphemes) are perceived as coloured. Most common form • Lexical-gustatory: words/phonemes evoke tastes • Associations differ from person to person, even within subtypes, but are highly stable for an individual • Synaesthetes are often artistic, and percepts reported as neutral or even beneficial
• Strong environmental influence ← ←
