Announcements. Exam 2 is a week from Today

Announcements Exam 2 is a week from Today

VI. Sleep and Dreams

Mini-Mailbag I was wondering why some people have such vivid dreams that they can have difficulty remembering if it actually happened or was just a dream, even during the following day. Why are some dreams so vivid that they can cause anxiety and guilt, yet other people don't even remember their dreams, or can easily distinguish dreams from reality.

Dream remembering https://www.youtube.com/watch?v=b94oprdrwe4

Why do we dream? 1. Wish Fulfillment: Freud suggested dreams provide a psychic safety valve to discharge unacceptable feelings. Royal road to the unconscious! 2. Information Processing: Dreams may help sift, sort, and fix a day s experiences in our memories.

Why do we dream? 3. Physiological Function: Dreams provide the sleeping brain with stimulation to develop and preserve neural pathways. Newborns thus need more sleep.

Why do we dream? All dream researchers believe we need REM sleep. When deprived of REM, subsequent REM Rebound.

Sleep and Dreams B. Dreams 1.People differ in their ability to remember dreams. Why? A. Defense mechanism (Freud) B. State-dependent phenomenon 2.Dream length 3.Confusion of dreams & reality 4.Lucid dreaming

End of Consciousness

Sensation and Perception

I. Overview A. Sensation: awareness of simple characteristics B. Perception: making complex interpretations

Top Down Versus Bottom Up Processing Bottom Up: the sensory features create the perception No Expectations or Experience necessary Top Down: Higher level mental processes based on our experience and expectations influence the perception

Bottom up Processing Analysis of the stimulus begins with the sense receptors and works up through levels of processing in the brain to give us the percept Letter A is really a black blotch broken down into features by the brain that we perceive as an A.

Top Down Processing Information processing guided by higher level mental processes as we construct perceptions, drawing on our experience and expectations.

Other Examples of Top Down Processes Proof reading trouble

Cna You Raed This? Aoccdrnig to rseerach at Cmabrigde Uinervtisy, it deosn't mttaer in waht oredr the ltteers in a wrod are, the olny iprmoatnt tihng is taht the frist and lsat ltteer be at the rghit pclae. The rset can be a total mses and you can sitll raed it wouthit porbelm. Tihs is bcuseae the huamn mnid deos not raed ervey lteter by istlef, but the wrod as a wlohe. Amzanig huh?

Other Examples of Top Down Processes Proof reading trouble Deciphering Lyrics Excuse me while I Kiss this guy? Excuse me while I Kiss the sky! Those alleged hidden messages in songs Another One Bites the dust tsud eht setib eno rehtona And many more!

Hidden Messages? Some claim that musicians insert these messages to influence us (e.g., promote satanic views!) Think skeptically Without top-down processing (i.e., knowing what it s supposed to say), we can t decipher it No evidence it has any effect when played forward OR backward

Key Concepts Thus Far Bottom-up Vs Top-down Processing Brain senses only Neural Energy; physical energy can only impact brain if transduction takes place Vision: Characteristics of Light The Fascinating Eye

Brain as Scientist Prisoner The brain only senses neural energy

Frequency/wavelength determines hue (color) Intensity determines perceived brightness

B. The Eye Vision 1. Eye receptors respond to light energy 2. Structure a. Cornea: Transparent tissue where light enters the eye.

The Eye

Vision B. The Eye 1. Eye receptors respond to light energy 2. Structure a. Cornea: Transparent tissue where light enters the eye. b. Iris 1. circular band of muscles; colored; 2. controls amount of light entering pupil c. Lens: 1. adjusts so as to train the light rays --image--on the retina 2. fixation reflex 3. Near-sightedness or far-sightedness

The Eye

The Lens Lens: Transparent structure behind the pupil that changes shape to focus images on the retina. Accommodation: The process by which the eye s lens changes shape to help focus near or far objects on the retina.

3. Receptor cells that make up retina a. Rods: don't perceive color 1. sensitive to low illumination 2. located in periphery of retina b. Cones: operate in greater illumination 1. sensitive to color differences, patterns 2. Fovea has only cones c. Blind spot: no rods or cones = no vision

Vision 3. Receptor cells that make up retina a. Rods: don't perceive color 1. sensitive to low illumination 2. located in periphery of retina b. Cones: operate in greater illumination 1. sensitive to color differences, patterns 2. Fovea has only cones c. Blind spot: no rods or cones = no vision

Find your Blind Spot (Figure 3.7)

Optic Nerve, Blind Spot & Fovea Optic nerve: Carries neural impulses from the eye to the brain. Blind Spot: Point where the optic nerve leaves the eye because there are no receptor cells located there. This creates a blind spot. Fovea: Central point in the retina around which the eye s cones cluster. http://www.bergen.org

Color Vision: Three Types of Cones We have three types of cones, unless colorblind Light of different wavelengths will stimulate these cone types by different Relative responsiveness of cones 1.00 0.50 0.00 Blue cones Green cones Red cones 400 450 500 550 600 650 amounts Wavelength in nanometers (billionths of a meter)

Color Blindness Due to lack of or problem with red cones A. I saw the number! B. I did not see a number E. I like E

Vision 4. Layers of retina a. Inside out and Upside Down! b. light passes through: vitreous humor (fluid) ganglion cells and bipolar cells (transparent layers of neurons) to photoreceptors at the back of retina (rods and cones)

Vision b. Light energy (photons) causes chemical reactions with photopigments within the rods and cones 1. intensity is coded by rate of firing c. Rods and cones send graded potentials 1. to next layer: bipolar cells; also send graded potentials to 2. ganglion cells 3. action potentials then carried to the CNS by ganglion cells.

Distribution of Rods and Cones Thousands of rods per square millimeter 180 140 100 60 20 0 Fovea Blind spot Fovea Blind spot 60 40 20 0 20 40 60 Distance on retina from fovea (degrees) Thousands of cones per square millimeter 180 140 100 60 20 0 Rods Cones Fovea Blind spot 60 40 20 0 20 40 60 Distance on retina from fovea (degrees)

Vision d. Axons from the ganglion cells leave the eye through the optic nerve 1. pass through the thalamus 2. in route to the primary visual cortex in occipital lobe (Striate cx)

Vision 5. Why all the different layers? a. To confuse and perplex students b. Data reduction c. Feature Detection

If we get this far today, I ll be totally surprised!