Class # 9: Sens Mech,Smell & Taste, p. 1

SENSORY MECHANISMSGeneral Aspects and Terminology

Some mechanisms are common elements for most types of sensation and perception. These eleements include:

A. The process of transduction

B. The process of coding

C. The relationship between stimulus and perception

SENSORY MECHANISMS

TransductionTransduction

Class # 9: Sens Mech, Smell & Taste, p. 2

SENSORY MECHANISMS

CodingCoding

Class # 9: Sens Mech, Smell & Taste, p. 3

SENSORY MECHANISMS

Coding (cont’d)Coding (cont’d)

BUT>>>>>>

Class # 9: Sens Mech, Smell & Taste, p. 4

Are perceptions copies of physical stimuli?

SENSORY MECHANISMS

The relationship between stimulus The relationship between stimulus and perceptionand perception

Cartoons associated with the case of Mr. Amadou Diallo, an emigrant from West Africa, who, returning home after work one evening in 1999, was shot to death by undercover New York police officers when he reached into his pocket to pull out a small dark object. The police were were looking for an armed rapist. The object turned out to be Diallo’s wallet. Cartoons from the following website: cagle.slate.msn.com/news/diallo/

Class # 9: Sens Mech, Smell & Taste, p. 5

Are perceptions copies of physical stimuli?

SENSORY MECHANISMS

The relationship between stimulus The relationship between stimulus and perception (cont’d)and perception (cont’d)

Obviously, the answer is an emphatic NO!!

Perceptions are constructions by our CNS, that are influenced by the

nervous system’s ability to learn and its dynamic integration, modulation,

and flexible controls of stimulus information.

We will discuss some of these abilities during class.

Class # 9: Sens Mech, Smell & Taste, p. 6

CHEMOSENSES: CHEMOSENSES: SMELL (olfaction) and TASTE (gustation)SMELL (olfaction) and TASTE (gustation)

Class # 9: Sens Mech,Smell & Taste, p. 7

CHEMOSENSES: Olfaction

Class # 9: Sens Mech, Smell & Taste, p. 8

CHEMOSENSES: Olfaction (cont’d)Receptors

Telereceptors Located in the nose The transduction part of the receptor looks like a dendrite with cilia ~60 day life cycle more than 1,000 types

Class # 9: Sens Mech, Smell & Taste, p.9

CHEMOSENSES: Olfaction (cont’d)

Class # 9: Sens Mech, Smell & Taste:, p. 10

CHEMOSENSES: Olfaction (cont’d)Routes of information transfer through the CNS

and submodality coding

1st synapse in olfactory bulbSubmodality coding = “spatiotemporal pattern in the glomuli of the olfactory bulb.”

Cranial nerve I to the olfactory bulb

(mitral cells and glomeruli)

Patterns of activation of glomeruli in the rat olfactory bulb produced by exposure of the olfactory mucosa to three different odorants.

(From: Rubin BD, Katz LC Neuron 1999;23:499-511) Class # 9: Sens Mech, Smell & Taste, p. 11

Routes through CNS

(1) Cranial nerve I olfactory bulb (mitral cells & glomeruli)

(2) From olfactory bulb to parts of paleocortex in the telencephalon, including the:

Amygdala (emotions)

Entorhinnal, pyriform, & orbitofrontal cortex.

(3) From there the information goes to

Hypothalamus (emotions, motivations),

Hippocampus (in temporal lobe: memory)

CHEMOSENSES: Olfaction (cont’d)Routes of information transfer through the CNS

Class # 9: Sens Mech, Smell & Taste, p. 12

CHEMOSENSES: TASTE

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CHEMOSENSES: TASTE (cont’d)

Class # 9: Sens Mech, Smell & Taste, p. 14

[ Umami? Carbohydrate?Glutamate? ]

Bitter

Salty

Sour

Sweet

Circumvallate

Foliate

Foliate

Fungiform

Types of papillae

CHEMOSENSES: TASTE (cont’d)

Which peripheral receptor?

Class # 9: Sens Mech, Smell & Taste, p. 15

CHEMOSENSES: TASTE (cont’d)Routes of information transfer through the CNS

Primary ‘gustatory’ cortex (near region where the mouth is represented)

Also to: amygdala, hypothalamus, orbital prefrontal cortex

Class # 9: Sens Mech, Smell & Taste, p. 16

CHEMOSENSES: TASTE (cont’d)Routes of information transfer through the CNS

Class # 9: Sens Mech, Smell & Taste, p. 17

Don’t forget!

I strongly encourage you to read Module 7.3 (p. 215-227)

thoroughly.

It contains loads of interesting information about smell and taste

as well as pheromones and synesthesia!

Class # 9: Sens Mech + Taste & Smell., p. 18