BIOPSYC Unit 2

Differentiate between chromosomes, DNA, and genes

Chromosomes are inside genes, which are inside DNA

Homozygous

Same genes on both copies of chromosomes

Heterozygous

Unmatched pair of genes

Dominant

Shows a strong effect in either the homozygous or heterozygous conditions

Recessive

Only shows effects in the homozygous condition

Epigenetic influence on gene expression

Changes in gene expression based on experience

Fetal Alcohol Syndrome

Hyperactivity, attention deficits, impulsivity, motor problems, heart defects, and facial abnormalities

Dendritic pruning

Alterations in spine densities in deep layers of the temporal lobe

Implications for temporal-limbic circuits (facial recognition, recognition of emotions, social-emotional functioning)

Sensory loss

Can cause one location to have increased sensitivity

• Blind people show increased sensitivity in fingers

Extensive music training

Can result in greater than normal cortical representation for fingers or larfer sometosensory cortex volumes

Experiences

Can alter brain anatomy and function including dendritic pruning, sensory loss, and extension of the brain

How can axon sprouting account for brain plasticity?

If a neuron loses input from an axon, it secretes neurotrophins that cause proximal axons to form new branches

These collateral sprouts can then take over vacant synapses

Wavelength

Associated with our perceptions of colors

Short wavelength

Violet, indigo, blue

Middle wavelength

Green

Long wavelength

Yellow, orange, red

Amplitude

Associated with intesity/brightness

Higher amplitude

More intense/bright

Lower amplitude

Dimmer and less intense visual images

Cornea

Outermost part of the eye

Focuses light waves into the eye onto certain areas of the retina

Iris

The colored part of the eye

Movement impacts the size of pupils to help control the amount of light waves coming into the eye

Pupil

Contains many muscles that can dilate (when light waves have a low amplitude) or constrict (when light waves have a high amplitude) this part of the eye

Aqueous Humor

Fluid in the space between the cornea and the lens

Watery substance

Supplies nutrients to the lens and other structures in the eye that do not have a direct blood supply

The body is constantly producing and recycling this part through drainage systems

Glaucoma

In some individuals, excess aqueous humor does not properly drain so fluid is pushed to the back of the eye, putting pressure on the retina

Virtuous Humor

Jelly-like consistency that fills the space between the front and back of the eye

Helps maintain the shape of the eye

Important for absorbing shock

Helps keep the retina pushed up against the back of the eyeball, which is important for vision

Cannot be replaced

Floaters in vision

Caused by pieces of virtuous humor

Lens

Specifically focuses light waves back to the retina to produce sharp, clear vision

Muscle fibers around this part work to change its shape to help focus on things close or far away (changes the way it bends light)

It can get stiffer with age, making it hard to stretch or push to focus on what you need to see. Muscles also begin to weaken, making it hard to read things up close

Cataracts

Clouding of the lens, a natural part of aging

Retina

A layer of tissue that lines the back of the eye

Light-sensory tissue that has photoreceptor cells (rods and cones) that are responsible for transduction and help trigger action potentials

Fovea

Small area on the retina that contains only cones

A dio

Associated with the clearest or sharpest vision

Muscle degradation of the fovea

Occurs when proteins accumulate in the fovea, preventing cones from firing and leading to loss of focused/central vision

Peripheral vision is still intact

The leading cause of vision loss for 50+ year olds

Optic Nerve

Bundles of axons from ganglion cells

There are no photoreceptors where the optic nerve leads to the eye, which creates a blind spot

Blind spot

Created by there being no photoreceptors where the optic nerve connects to the retina

Why are we usually not aware of our blind spot

The brain fills in the gap using surrounding images, information from the other eye, and our eyes are constantly moving

Rods

More in the periphery

Not helpful for color detail

Very useful in low-light conditions, can pick up on much weaker intensities of light

Cones

More in the center

Prominent in fovea

Essential for seeing color
Good for detail

Only work well in adequate light conditions

Three different types

How do we perceive color?

Trichromatic theory

Opponent-process theory

Opponent neurons

Trichromatic Theory

Our experience of color vision depends on the cone intensity at a particular area

Tied specifically to which type of photoreceptors are being activated

• Short wavelength: Blue cones

• Medium wavelength: Green cones

• Long wavelength: Red cones

Opponent-Process theory

The visual cortex and retinal ganglion cells process color in three oppoent

• Yellow-blue

• Red-green

• Black-white

Staring at one color creates an afterimage of its opposite pair color

Opponent Neurons

Specialized visual cells that process color with an excitatory response to wavelengths and with an inhibitory response to its opponent

• E.g., Red-Green

Neural Convergence

Occurs when several neurons synapse onto a single neuron

Higher convergence of rods than cones

Neural Convergence: Rods

Two different combinations of cells result in the same response in the ganglion cell

Detail is not being coded

Neural Convergence: Cones

One-to-one correspondence between cones and ganglion cells

Allow for detail to be coded

Left visual field

Hits to the left eye nasal retina

Hits the right eye temporal retina

Right visual field

Hits the right eye nasal retina

Hits the left eye temporal retina

Describe the basic path that information takes from the right/left visual field of each to the visual cortex

1. Light hits the retina

2. Left visual field hits the left nasal retina + right temporal retina, while right visual field hits the right nasal retina + left temporal retina

3. Photoreceptors in the retina convert light into signals, which then leave through the optic nerve

4. Signals reach the optic chiasm

• Axons from the nasal retinas cross to the opposite side

• Axons from the temporal retinas stay on the same side

5. Signals reach the primary visual cortex

• Right visual cortex receives left visual field info

• Left visual cortex receives right visual field info

Receptive Fields in the Visual Cortex (V1)

Stimulated retina with patterns of light

Recorded single cells/fibers at various points along the visual pathway

Determine receptive fields in neurons at each level

Simple Cortical Cells

Specialized neurons in the primary visual cortex (V1) that detect specific edges, lines, or bar-shaped stimuli

Have distinct ON/OFF subregions

Highly sensitive to the orientation, position, and polarity of a stimulus

Fires if the visual stimulus, edge, or line in the pixel of your visual field is oriented at a certain angle

Complex Cortical Cells

A type of neuron in the primary visual cortex (V1) that responds to specific edge orientations (e.g., vertical lines) moving in a particular direction within a large visual field

Lack distinct ON/OFF zones

Show spatial invariance, responding regardless of the exact position of the stimulus

Selective rearing

If an animal is reared in an environment that contains only certain types of stimuli, then neurons that respond to those stimuli will be more prevalent

A kitten reared with only vertical lines would ignore a horizontal rod placed in front of them

More coritcal cells fired to the orientation experienced during rearing

Carpentered world

Experience with parallel lines and right angles increases susceptibility to the Muller-Lyer illusion

What/Ventral Pathway

Striate cortex (V1) to the temporal lobe (ventral stream)

Monkeys with damage to the temporal lobe fail the object discrimination task

Where/Dorsal Pathway

Striate cortex (V1) to the parietal lobe (dorsal stream)

Monkeys with damage to the parietal lobe fail the landmark discrimination task

Prospagnosia

Damage to the fusiform gyrus (specialized to respond to faces) that causes difficulty in recognizing the faces of familiar people

Facial recognition

Takes place in the fusiform gyrus

Faces elicit the fastest eye movement

It’s difficult to identify faces upside down

Specialized neurons and locations in the brain are associated with processing faces

Faces are special argument

Human newborns pay more attention to faces than to other visual stimuli

Humans are predisposed to see faces, and cortical cells that respond to faces also respond to face-like objects

Faces are not special argument

Our proficiency in perceiving faces, and the largest response in the fusiform gyrus, is due to extensive experience/exposure

Frequency

The number of times that a wave repeats itself in a second

Measured in Hertz (Hz)

Higher=higher pitch

Amplitude

The difference in pressure between the high and low peaks of the wave

Larger=louder

Pitch

Often associated with a musical scale

A property of speech

Higher=higher frequency

Inner Ear

Pinna

Auditory Canal

Eardrum

Pinna

Collects, amplifies, and directs sound into the auditory canal

Auditory Canal

Protects the middle ear

Provides resonance

Resonance

Occurs when sound waves are reflected back from the closed end of the canal

Certain frequencies are reinforced depending on the size of the canal

Eardrum

Vibrates in response to sound waves

Middle Ear

Malleus, incus, and stapes

Malleus, incus, stapes

Transmit vibrations from the eardrum to the inner ear by pushing on the membrane covering the oval window

Amplify soundwaves so that they can transfer from air to liquid more effectively

Inner Ear

Semicircular canals

Coachlea

Semicircular canals

Sense head rotation and assist with balance

Coachlea

Begins the process of auditory transduction

Describe how sound waves travel through the structures of the ear

1. The cochlea has 3 tunnels, each of which goes from the base to the apex

2. The cochlear partition contains the scala media and structures necessary for transduction

3. The vibrations of the oval window set the liquid inside the cochlea into motion

4. This movement displaces the hair cells, and when they bend, it triggers an action potential

Place theory of pitch perception

Low frequencies cause more vibrations at the apex of the cochlea

High frequencies cause more vibrations near the base end of the cochlea

Merkel receptor

Fire continuously, as long as the stimulus is presented, or “on”

Respond to light touch, detail, and fine texture

Meissner corpuscle

Fires when the stimulus is first applied, and then again when it is removed Responds to motion across skin
Important for handgrip control

Ruffini cylinder

Fires continuously in response to stimulus

Respond to stretching of skin and roughness

Pacinian corpuscle

Fires when the stimulus is applied or removed

Respond to rapid vibrations, fine texture when fingers are moving, and sudden touch

Direct pathway

Receptors send signals directly to the brain

• Thin, unmyelinated axons = Dull, milder pain

• Thick, myelinated axons = Sharp, intense pain

Gate theory

Touch receptors and the brain can modulate perception of pain

Placebo Effect

Patients believe they are receiving an effective therapy, expect a reduction in pain, and then experience the expected effect

Attention

It’s not so much about when you are injured, but when you realize that you’re injured

Five basic taste qualities

Sweet, sour, salt, bitter, umani

Basic anatomy of the taste system

The bumps on the tongue are papillae, and the taste buds line these

• Circumvallate papilla

• Foliate papilla

• Fungiform papillae

Circumvallate Papilla

Big taste buds at the back of tongue

Foliate Papillae

At the middle sides of your tongue

Fungiform papillae

Mostly at the tip and along the sides

Neurogenesis

Constant renewal of receptors

Specificity coding

Individual neurons respond to specific qualities

Population coding

Quality is signaled by the pattern of activity across several neurons

How do previous experiences and genetic influence individual differences in taste?

75% of people can taste PTC

The ability to taste PTC is tied to a single gene that codes for a certain taste receptor on the tongue

Supertasters

Make up 25% of people

Report that foods such as dark chocolate, coffee, and broccoli are extreamely bitter

More likely to experience pain when eating very spicy foods

More likely to dislike sugary foods

Olfactory receptor neurons

Located in the olfactory mucosa

Cilia dendrites protrude through the mucosa

Sensitive to chemical odors

Olfactory bulb

All olfactory receptor neurons. (ORNs) of a particular type send their signals to one or two glomeruli

Each glomerulus collects information about the firing of one type of ORN

Primary olfactory cortex

Odors that smell different cause different patterns of firing of olfactory receptors

Excitation in the olfactory bulb is equally organized

Odorants that cause activity in the specific locations in the olfactory bulb now cause widespread activity in the PC

Substantial overlap between the activity caused by different odorants

How well can people identify odors? What factors influence this ability?

Humans can discriminate millions of different odors, but often find it difficult to identify specific odors

Experience, practice, genetic variability, and cognitive influences can influence identification abilities

Flavor

The perceptual experience resulting from the combination of taste, olfaction, and cognitive factors

Describe the retronasal route in our perception of flavor

When we chew food, vapors reach the olfactory mucosa via the retronasal route

• Pinching your nose prevents vapors from reaching the olfactory mucosa by eliminating the circulation of air through this channel

Endogenous rhythms

Generation from within

Different lengths

Cicannaul, circalunar, circadian

Zeitgeber

Factors that set the biological clock
Includes light, exercise, food, arousal, temperature

Disruptions to the biological clock

Daylight saving time

Jet lag

Night shift

Short-wavelength (e.g., blue) light

Suprachiasmatic nucleus (SCN)

Damage can disrupt the biological clock

These neurons removed from the body will continue to produce a circadian rhythm of action potentials