• Olfactory bulb receives input from olfactory receptors which contact mucus in nasal cavity

Smell

• There are thousands of different receptors for different kinds of molecules

Smell

• Pheromones are not smells• Pheromones are chemical signals sent from

one animal to another

Pheromones

• Pheromones either induce a behavior in another animal or cause some physiological change

• Very common in insects...not so common in mammals...unclear role in humans

Pheromones

• For example: Androstenone, found in male pig saliva, causes a female pig to allow the male to mate with her

Fun Facts about Pheromones

• androstenone is also found in the sweat of human males!

• Does androstenone (or pheromones in general) affect humans?

• Design an (ethical) experiment…

Fun Facts about Pheromones

• Kirk-Smith & Booth (1980) sprayed some of the seats in a dentist’s waiting room with androstenone

• Compared to a control condition, more women used the androstenone seat

Fun Facts about Pheromones

• Fewer men used the androstenone seat !

Fun Facts about Pheromones

• Other possible ways in which pheromones influence humans:– synchronization of menstrual cycles– mate selection - attraction to opposite major

histocompatibility complex

Pheromones

• Pheromones do not control behavior!• Human behavior is largely under top-down

influences, but may be affected subtly by pheromones

• It is unclear whether molecules such as androstenone even qualify as pheromones - they may be just like other odour molecules

Pheromones

• “It is now possible to manufacture synthetic human pheromones and such compounds are often used in research as they are relatively easy to make, convenient to store, and easy to apply.”

Pheromones

Upcoming:

Read article by Gregory for February 16th

Read chapter by Pinker for February ~28th

Vision

Seeing

• Seeing is the process of converting electromagnetic radiation into a conscious mental event

Seeing

• visual system faces many challenges– too much information– too little information– conflicting information– ambiguous information

Seeing

• too much information

Seeing

• too little information

Seeing

• Conflicting Information

Seeing

• Ambiguous information

Seeing

• We will consider two aspects of vision to explore how the brain overcomes these challenges:

– Seeing depth– Seeing in color

Seeing

• Remember that the only information the brain gets is a 2D pattern of light on each retina

Seeing

• Remember that the only information the brain gets is a 2D pattern of light on each retina

• Our rich vivid visual experience is built out of those sparse inputs!

Seeing

• Remember that the only information the brain gets is a 2D pattern of light on each retina

• Our rich vivid visual experience is built out of those sparse inputs!

• Put another way, everything your brain needs to “see” is encoded in those patterns of light energy

Seeing

• Remember that the only information the brain gets is a 2D pattern of light on each retina

• Our rich vivid visual experience is built out of those sparse inputs!

• Put another way, everything your brain needs to “see” is encoded in those patterns of light energy

• …well almost everything

• Light is an oscillation (a wave) in the electromagnetic field

Light

• What are some characteristics of light waves?

Properties of light

• What are some characteristics of light waves?– amplitude/intensity - how big of a fluctuation in

the field/how many waves– frequency - how many fluctuations (waves) pass

by a certain point in a given period of time– polarization - the orientation of the waves

Properties of light

•What perceptions are associated with those physical properties?

Properties of light

•What perceptions are associated with those physical properties?–Intensity is associated (loosely) with brightness–Frequency is associated (very loosely) with color–Polarization isn’t sensed by humans (but it is by some insects and birds!)

Properties of light

Light

• The spectrum is the range of frequencies of electromagnetic waves

• The eye– curved

cornea– lens– retina– fovea– optic disk

Using Light

• Light is focused on the retina by the curvature of the cornea and the lens– Flat lens (relaxed muscles) focuses distant points

Using Light

• Light is focused on the retina by the curvature of the cornea and the lens– Accomodation: Bulged lens (muscles flexed) focuses on near points

Using Light

• Light is focused on the retina by the curvature of the cornea and the lens

• Constriction of the pupil limits how much light gets in AND reduces the amount of focusing required of the lens

Using Light

• photoreceptors transduce incoming light• ganglion cells send signals along to the brain

The Retina has layers of cells