of smell Bente G. Berg, Dept. of Psychology, NTNU, Trondheim

Transcription

1 The sense of smell

2 Smell and taste flavour

3 Outline What characterizes the odor stimulus? Anatomical organization of the olfactory pathway Encoding mechanisms the logic of smell Pheromones Universal principles across vertebrates and invertbrates

4 Outline What characterizes the odor stimulus? Anatomical organization of the olfactory pathway Encoding mechanisms the logic of smell Pheromones Universal principles across vertebrates and invertbrates

5 Some components forming the odor of an orange Limonene Octanol Sabinene Alpha-pinene Linalool Myrcene Small volatile molecules discontinuous

6 Headspace volatiles Identifying relevant plant odorants carbon filter FID Air Computer O Frequency meter TR II L pump sucking air I A adsorbent GC Insect antenna Physiological identification Chemical identification Verification 100 ikes/s spi 0 Activity of a single receptor neurone min Single cell activity: Stranden, Røstelien, Mustaparta, Chem Senses 50 Spikes/ /s 0

7 Outline What characterizes the odor stimulus? Anatomical organization of the olfactory pathway Encoding mechanisms the logic of smell Pheromones Universal principles across vertebrates and invertbrates

8 The main olfactory epithelium is located dorsally in the nasal cavity Scientific American 1995, Axel

9 Visualization of a sensory neuron in the olfactory epithelium Axon (not visible) Cell body A small bipolar neuron Cilia (detection area) Dendrite Scientific American 1995, Axel

10 The detection area of the sensory neuron (dendrite with cilia) Scientific American 1995, Axel

11 The olfactory receptor protein Buck 2004

12 The genes coding for olfactory receptors are distributed ib d on various chromosomes Buck 2004

13 The sensory axons from the olfactory epithelium make up the olfactory nerve. This nerve, Cranial nerve I, projects to the olfactory bulb, the primary olfactory integration center of the brain. Haug, Sand og Sjaastad

14 The olfactory bulb

15 The olfactory bulb has an anatomical organisation characterized by so-called glomeruli. These spherical structures are synaptic areas of input- and output-neurons. Scientific American 1995, Axel

16 The olfactory tract The information is mediated from the olfactory bulb to the olfactory cortex via the olfactory tract.

17 The olfactory information is mediated to phylogenetically old regions of the temporal lobe

18 The olfactory information is mediated to phylogenetically old regions of the temporal lobe The olfactory cortex (piriform cortex, entorhinal cortex, lateral amygdala) and dhippocampus

19 The orbitofrontal cortex, a region of the neocortex that processes olfactory information i

20 Brain areas involved in processing olfactory information (horizontal view) Purves et al..

21 The olfactory pathways (rough overview) Buck 2004

22 The insect olfactory system Almaas In the insect olfactory system, sensory neurons are housed in numerous sensilla covering the antennae. These neurons project directly to the primary olfactory center of the brain, here called the antennal lobe Berg et al. J. Comp. Neurol.

23 Outline What characterizes the odor stimulus? Anatomical organization of the olfactory pathway Encoding mechanisms the logic of smell Pheromones Universal principles across vertebrates and invertbrates

24 What takes place in the periphery? Does each sensory neuron express several types of receptor proteins or only one type?

25 Each sensory neuron expresses only one type of olfactory receptor and each neuron type is distributed in the olfactory epitheliumt (within one of four zones) (mouse, whole mount, sagittal view)

26 What takes place in the olfactory bulb? Do the different types of sensory neurons have a particular address in the olfactory bulb?

27 Sensory neurons expressing one type of receptor project to one (or a few) glomeruli in each olfactory bulb (mouse, whole mount, sagittal view) Chemotopic/odotopic organisation

28 The pattern of activated glomeruli will, at any time, be a representation of the stimuli present (mouse, whole mount, sagittal view) A spatial map in the olfactory bulb

29 Outline What characterizes the odor stimulus? Anatomical organization of the olfactory pathway Encoding mechanisms the logic of smell Pheromones Universal principles across vertebrates and invertbrates

30 Pheromones are chemical signals acting between individuals, id a sender and a receiver, within one species. The first pheromone identified was bombykol, produced by the silk moth female, Bombyx mori. (Butenandt 1959).

31 The Silk Moth Bombyx mori BOMBYKOL:(E,Z)-10,12-Hexadecadien-1-ol (C 16 H 30 O)

32 The moth has developed a male-specific system for pheromone information Almaas Pheromone-sensitive receptor neurons in long sensilla Particularglomeruli, the macroglomerular complex (MGC), are the address of the pheromone-sensitive receptor neurons Berg et al. J. Comp. Neurol.

33 A male specific structure in the antennal lobe (the macroglomerular complex, MGC) Berg et al. J. Comp. Neurol.

34 The male possesses pheromone-specific neurons Z9-14:AL, substance B Berg et al. J. Comp. Physiol.

35 The axon of each pheromone-neuron projects to the MGC Z9-14:AL, substance B Berg et al. J. Comp. Physiol.

36 The odotopic organization also applies to insect Z9-14:AL, substance B Berg et al. J. Comp. Physiol

37 Chemosensory subsystems in the nose of the mouse Main olfactory epithelium Vomeronasal organ Septal organ of Masera Gruenberg ganglion Brennan and Zufall; Nature 2006

38 MHC-associated cues as individuality signals These kind of signals may be relevant for mate choice and parent-offspring interactions. It has been indicated that the MHG genotype influences the volatile constituents of urine. The so-called carrier hypothesis suggests that the MHG genotype influences body odour.

39 The Bruce effect Brennan and Zufall; Nature 2006

40 Behavioral responses elicited by the vomeronasal system Bruce effect: A pregnancy disruption, in which exposure of a female to an unknown male results in abortion. Lee-Boot effect: A suppression, via an estrogen-depentent pheromone, of the the menstrual cycle of female mice housed in groups and isolated from males. Whitten effect: A synchronization of the menstrual cycle of female mice caused by a male-produced pheromone.

41 Flehmen behavior

42 The vomeronasal system Receptor neurons in the vomeronasal organ (VNO) project to the acesessory olfactory bulb (AOB). From the AOB, the information is mediated via secondary neurons to the ventral amygdala (VA). Amygdala is connected to regions of the hypothalamus (H). The accessory olfactory system (the vomeronasal system) Brennan and Zufall; Nature 2006

43 The two olfactory pathways in vertebrates The main olfactory system The vomeronasal system (the accessory olfactory system) Brennan and Zufall; Nature 2006

44 Do human pheromones exist?

45 Do human pheromones exist?

46 Outline What characterizes the odor stimulus? Anatomical organization of the olfactory pathway Encoding mechanisms the logic of smell Pheromones Universal principles across vertebrates and invertbrates

47 Diversity of life Evolution of the insects, Grimaldi and Engel

48 The four 3-D images showing the glomerular structures of the brain olfactory center and stained neurons therein, i.e. a local interneuron, a projection neuron, and a modulatory neuron type, is not included in this PDF-file. (Your visual system should, however, manage to recall an image )

49 The Silk Road

50 The founder of The Silk Road! Grimaldi and Engel, 2004

51 Du har to øyne Du har to øyne som du kan se med, og munnen kan du blant annet le med, og du kan smake og du kan høre, og selv bestemme hva du vil gjøre. Og du kan lukte en appelsin, og du kan føle med hånden din.