1. Psychology 355 04 The Chemical Senses

2. Psychology 3552 Introduction I.Animals depend on the chemical senses to identify nourishment II.Chemical sensation A.Oldest and most common sensory system III.Chemical senses A.Gustation B.Olfaction C.Chemoreceptors

3. Psychology 3553 Taste The Basics Tastes 1.Saltiness 2.sourness, 3.sweetness, 4.bitterness, and 5.Umami Examples of correspondence between chemistry 1.Sweet—sugars like fructose, sucrose, artificial sweeteners (saccharin and aspartame) 2.Bitter—ions like K + and Mg 2+, quinine, and caffeine 3.Sour— Acidity (low Ph), H+ 4.Salt—Na+

4. Psychology 3554 Taste Advantage – Survival: Poisonous substances - often bitter Single-Trial Learning; Self-Balancing Diet

5. Psychology 3555 Taste The Basics Tastes 1.Saltiness 2.sourness, 3.sweetness, 4.bitterness, and 5.Umami chemistry 1.Sweet—sugars like fructose, sucrose, artificial sweeteners (saccharin and aspartame) 2.Bitter—ions like K + and Mg 2+, quinine, and caffeine 3.Sour— Acidity (low Ph), H+ 4.Salt—Na+ Advantage – Survival: Poisonous substances - often bitter

6. Psychology 3556 Taste The Basics Tastes A.Saltiness B.sourness, C.sweetness, D.bitterness, and E.Umami chemistry A.Sweet—sugars like fructose, sucrose, artificial sweeteners (saccharin and aspartame) B.Bitter—ions like K+ and Mg2+, quinine, and caffeine C.Sour— Acidity (low Ph), H+ D.Salt—Na+ Advantage – Survival: Poisonous substances - often bitter

7. Psychology 3557 Taste The Basic Tastes A.Steps to distinguish the countless unique flavors of a food 1.Each food activates a different combination of taste receptors 2.Distinctive smell 3.Other sensory modalities

8. Psychology 3558 Taste The Organs of Taste Tongue, mouth, palate, pharynx, and epiglottis

9. Psychology 3559 Taste Areas of sensitivity on the tongue 1.Tip of the tongue Sweetness 2.Back of the tongue Bitterness 3.Sides of tongues Saltiness and sourness

10. Psychology 35510 Taste The Organs of Tastes A.Papillae 1.Foliate papillae 2.Vallate papillae 3.Fungiform papillae Threshold concentration Just enough exposure of single papilla to detect taste

11. Psychology 35511 Taste I.Tastes Receptor Cells A.Apical ends  Microvilli  Taste pore B.Receptor potential: Voltage shift

12. Psychology 35512 Taste Mechanisms of Taste Transduction A.Transduction process 1.Taste stimuli (tastants) i.Pass directly through ion channels (Na+) ii.Bind to and block ion channels (sour-H+) iii.Bind to G-protein-coupled receptors (bitter, sweet, umami)

13. Psychology 35513 Taste Mechanisms of Taste Transduction Saltiness 1.Salt-sensitive taste cells i. Special Na + selective channel 2.Blocked by the drug amiloride

14. Psychology 35514 Taste Mechanisms of Taste Transduction Sourness 1.Sourness- acidity – low pH 2.Protons causative agents of acidity and sourness

15. Psychology 35515 Taste Mechanisms of Taste Transduction Bitter, Sweet, Umami A.G-protein coupled receptor B.Activates Phospholipase C C.Increases messenger inositol triphosphate (IP 3 ) D.CA 2+

16. Psychology 35516 Taste Mechanisms of Taste Transduction Bitterness 1.Families of taste receptor genes - TIR and T2R

17. Psychology 35517 Taste Mechanisms of Taste Transduction Sweetness 1.Sweet tastants natural and artificial 2.Sweet receptors i.T1R2+T1R3 ii.Expressed in different taste cells

18. Psychology 35518 Taste Mechanisms of Taste Transduction A.Umami 1.Umami receptors: i.Detect amino acids ii.T1R1+T1R3

19. Psychology 35519 Taste Central Taste Pathways A.Gustatory nucleus Point where taste axons bundle and synapse B.Ventral posterior medial nucleus (VPM) of the thalamus C.Primary gustatory cortex Receives axons from VPM taste neurons

20. Psychology 35520 Taste

21. Psychology 35521 Taste

22. Psychology 35522 Taste Central Taste Pathways (Cont’d) A.Localized lesions 1.Ageusia- the loss of taste perception B.Gustation 1. Important to the control of feeding and digestion i.Hypothalamus ii.Basal telencephalon

23. Psychology 35523 Taste The Neural Coding of Taste A.Labeled line hypothesis 1.Individual taste receptor cells for each stimuli 2.In reality, neurons broadly tuned 3.Population coding i.Roughly labeled lines ii.Temperature iii.Textural features of food

24. Psychology 35524 Smell Pheromones A.Smell— a mode of communication B.Important signals 1.Reproductive behavior 2.Territorial boundaries 3.Identification 4.Aggression C.Role of human pheromones

25. Psychology 35525 Smell The Organs of Smell Olfactory epithelium Olfactory receptor cells, supporting cells, and basal cells

26. Psychology 35526 Smell

27. Psychology 35527 Smell The Organs of Smell A.Odorants: Activate transduction processes in neurons B.Olfactory axons constitute olfactory nerve C.Cribriform plate: A thin sheet of bone through which small clusters of axons penetrate, coursing to the olfactory bulb D.Anosmia: Inability to smell E.Humans: Weak smellers Due to small surface area of olfactory epithelium: Dogs have about 170 cm 2 compared to 10 cm 2 in humans, and about 100 times more receptors per unit area

28. Psychology 35528 Perception of Smell The dimensions of smell

29. Psychology 35529 Perception of Smell (cont.) I.We can distinguish between about 10,000 different smells Different threshold levels for different smells II.Two thresholds for each smell -low threshold for the existence of a chemical, somewhat higher threshold to discriminate one smell from another

30. Psychology 35530 Perception of Smell I.Adaptation - Olfactory fatigue - cross-adaptation II.Smell Constancy - receptors are more stimulated during a deep sniff than a shallow one - the judgment of odor intensity does not change -

31. Psychology 35531 Smell

32. 32 Pheromones: Mammals Powerful effects on behavior, specifically sexual behavior, territorial behavior and identification of kin Mammals I.Most mammals only become sexually aroused in the presence of pheromones II.Increased likelihood of pregnancy III.Synchronization of estrus cycles IV.Mutual recognition of mother and offspring V.Territory marking (e.g. dogs)

33. Psychology 35533 Pheromones: Mammals I.Releasers - trigger a specific behavioral response II.Primers - trigger a hormone response which increases the likelihood of certain types of behaviors

34. 34 Pheromones: Humans Humans I.infants can correctly identify their own mother's milk and are much more likely to nurse when its their own mother II.female menstrual cycles can be altered by pheromones - the sorority effect III.male and female behavior is highly influenced by pheromones t-shirt experiment - musky versus sweet - IV.the musky odor is rated by males and females as unpleasant and is thought to serve as a territorial marker among males

35. Psychology 35535 Pheromones: Humans Increase sexual arousal in males I.Increases male perception of female attractiveness women in photographs were rated as significantly more sexually attractive when judges were first exposed to alpha androstenol II.Increases willingness of females to initiate social contact with males females exposed to alpha androstenol were much more receptive to male-initiated contact more likely to seek out male company less likely to seek female company

36. Psychology 35536 Smell Olfactory Receptor Neurons A.Olfactory Transduction

37. Psychology 35537 Smell Olfactory Receptor Neurons Olfactory Transduction Oderant to receptor protein Stimulates G (olf) -protein Activates adenylyl cyclase cAMP Opens Na + Ca 2+ channels Opens Cl - channels (out) Depolarization

38. Psychology 35538 Smell Olfactory Receptor Neurons Olfactory Transduction

39. Psychology 35539 Olfactory Transduction Adaptation: Decreased response despite continuous stimulus Smell

40. Psychology 35540 Central Olfactory Pathways Smell

41. 41 Olfactory Bulb Olfactory bulb - organ which houses all the nerves which receive inputs from the olfactory receptors Limbic and Thalamic connections Olfactory cortex (frontal lobe)

42. Psychology 35542 Central Olfactory Pathways Smell

43. Psychology 35543 Central Olfactory Pathways A.Axons of the olfactory tract: Branch and enter the forebrain B.Neocortex: Reached by a pathway that synapses in the medial dorsal nucleus Smell

44. Psychology 35544 Central Olfactory Pathways A.Axons of the olfactory tract: Branch and enter the forebrain B.Neocortex: Reached by a pathway that synapses in the medial dorsal nucleus Smell

45. Psychology 35545 I.Spatial and Temporal Representations of Olfactory Information A.Olfactory Population Coding B.Olfactory Maps (sensory maps) C.Temporal Coding in the Olfactory System Smell

46. Psychology 35546 Concluding Remarks I.Transduction mechanisms A. Gustation and olfaction II.Similar to the signaling systems used in every cell of the body III.Common sensory principles - broadly tuned cells A.Population coding B.Sensory maps in brain IV.Timing of action potentials A.May represent sensory information in ways not yet understood

47. Psychology 355 End of Presentation