Sensory Processes 3270 Lecture 6 (chemical senses)

1. Sensory Processes 3270 Lecture 6 (chemical senses)

2. KEYWORDS ---- VESTIBULAR I CANALS rotation, cupula, hair cells coded by looking at the difference between all three of them example of a CHANNEL CODING SYSTEM. OTOLITHS Translation, macula, hair cells, utricle, saccule Coded by looking across the activity of all fibres Example of a POPULATION CODING SYSTEM.

3. KEYWORDS ---- VESTIBULAR 2 eye movements (rotation), equal and opposite to head movement, three pairs of eye muscles whose direction of pull roughly corresponding to planes of the canals, mathematical integration required to change acceleration signal into a position signal (must be done by the brain) eye movements (translation), depend on (i) head movement (ii) direction of target (eg. left or right) and (iii) distance of target, geometry shown to be taken into account by system eye movements (neural pathway), hair cells > afferent nerve (VIII) > vestibular nucleus > oculomotor nuclei > oculomotor nerves (III, IV and VI) > eye muscles

5. Oculomotor III Abducens VI

6. The 12 Cranial Nerves 1 olfactory 2 optic 3 oculomotor 4 trochlear 5 trigeminal 6 abducens 7 facial 8 auditory and vestibular 9 glossopharyngeal 10 vagus 11 accessory 12 hypoglossal

7. III III Oculomotor nuclei (III) Vestibular nerve (VIII) VI VI Abducens nuclei (VI) VN VN

8. KEYWORDS ---- VESTIBULAR 3 vestibulo-spinal reflexes, primitive (evolutionarily), but capable of remarkable complexity (organized response with many muscles) multi-modal cues to self motion: vision and vestibular normally active together, vestibular nucleus responds to EITHER vision OR vestibular (or both), visual motion without actual motion causes linear or circular vection

9. KEYWORDS ---- VESTIBULAR 4 Self motion and ALCOHOL 1 alcohol -> canals 2 alcohol rises and moves the fluid 3 causes head to feel tilting DOWN 4 eyes move UP 5 retina past still world -> visual world moved DOWN 6 visual vection created suggesting head tiltingUP 7 head up and down at same time? 8 Must be poisoned. 9 GET RID OF IT!!!!

10. KEYWORDS ---- VESTIBULAR 5 motion sickness (sensory conflict): reading in vehicle, head movements in space, being below deck in a ship SPACE: navigation (path integration); artificial gravity; canals reacting to heat in absence of gravity; perception of linear motion

11. Sensory Processes 3270 Chemical senses TASTE

12. Taste primaries: sweet, sour, salty, bitter, umani

13. Figure 15.14 The contribution of each of the four basic tastes to the tastes of KCl and NaNO3, determined by the method of magnitude estimation. The height of the line indicates the size of the magnitude estimate for each basic taste. (From McBurney, 1969.) MAGNITUDE ESTIMATION

15. Tongue • Papillae • Taste buds • Taste cells • Receptors

16. THE TONGUE Chorda tympani (part of facial VII) Glossopharyngeal (IX) Bitter Sour Salt Sweet (Filiform have no taste buds)

18. Fungiform

19. Foleate

20. Circumvallate

21. TASTE BUDS

22. TASTE BUDS

23. CODING in the TASTE SYSTEM • Specificity (labelled lines) • or • Distributed code ???

24. RESPONSES OF TASTE FIBRES TO DIFFERENT SALTS sodium chloride potassium chloride ammoniumchloride

25. Now make potassium chloride aversive Rats avoid BOTH potassium chloride AND ammonium chloride But not sodium chloride Similar cell patterns seem to correspond to similar “perceptions”

26. Distributed • cells respond to more than one primary • across fibre patterns found • Specificity • cells broadly into 5 types • salt • sour • bitter • sweet • umani • …. Each with different channel mechanisms • salt deprived  salt cells quiet

27. RESPONSES OF TASTE FIBRES salt type fibres sweet type fibres

28. Sweet Salt Sour Bitter SPECIFICITY CODING IN TASTE

29. PTC tastes bitter to humans but not to mice. They can be cloned to find the taste of PTC aversive.

30. CONCLUSION: Both distributed and specificity (labelled line) codes are involved in determining taste

31. taste thresholds • depend on: • temperature (different primaries alter differently) • Tongue region

32. TASTE THRESHOLDS salt sweet sour THRESHOLDS bitter VARIATIONOVER TONGUE VARIATION WITH TEMPERATURE

33. taste thresholds • depend on: • temperature (different primaries alter differently) • Tongue region • genetics (phenylthiocarbamide: to 2/3rds of white western folk tastes bitter; 1/3rd no taste) • concentration (eg. saccharin low sweet; high bitter) • Age • adaptation

34. taste preferences, Humans: sweet (+); bitter (-) (mostly in place at birth) Cats /chickens: indifferent to sweet; rat/cat/rabbit/sheep: salt (+); hamster: salt (-) taste cravings, salt, calcium, potassium, etc.. specific changes in threshold when deprived (eg. for salt) cultural influences, conditioned taste aversion

35. TASTE PATHWAY • neural pathway (uncrossed) • taste cells, • VII cranial nerves (corda tympani division of facial nerve), IX cranial nerve (glossopharyngeal), • solitary nucleus • ventral posterior medial nucleus of thalamus, • taste cortex (near mouth representation of somatosensory cortex) 4. to cortex 3. to thalamus VII IX 1. receptors 2. nerves also brain stem vomit centres

37. Taste cortex Central sulcus TASTE AREA I TASTE AREA II Ventro-posterior medial thalamus