PSB UNIT2 STUDY GUIDE

Chapter 5: Vision

• Route Within the Retina: What are the main types of cells in the retina, and what is the path of light in the retina? Which cells send direct messages to bipolar cells? Which cells send direct messages to ganglion cells?

• The main types of cells in the retina include receptors (rods and cones), bipolar cells, horizontal cells, amacrine cells, and ganglion cells.

• The path of light in the retina begins with the receptors, which convert light into electrical signals.

• Receptors send direct messages to bipolar cells, while bipolar cells send direct messages to ganglion cells, ultimately transmitting visual information to the brain.

• Horizontal cells (HCs) are interneurons in the retina that modulate information flow between photoreceptors and bipolar cells, contributing to contrast enhancement, color opponency, and the formation of center-surround receptive fields.

• Characteristics of foveal vision and peripheral vision. What are the differences between foveal vision and peripheral vision?

• Foveal Vision: This type of vision is characterized by high acuity and color perception, primarily due to the dense concentration of cones in the fovea. It allows for detailed vision necessary for tasks such as reading and recognizing faces.

• Peripheral Vision: In contrast, peripheral vision is responsible for detecting motion and providing a broader field of view, but it has lower acuity and is more sensitive to light. This vision relies more on rods, which are more prevalent in the peripheral regions of the retina.

• Distribution of rods and cones in the retina? Which receptors control peripheral vision? Which receptors control foveal vision?

20:1 Rods to cones ratio. Rods control peripheral vision while cones control foveal vision.

• Characteristics of rods and cones and differences between rods and cones. Which receptors are responsible for color perception?

• Rods: Highly sensitive to light, enable vision in low-light conditions, and do not detect color.

• Cones: Require brighter light for activation, responsible for color vision, and are concentrated in the fovea.

• Color Vision Theories: Characteristics of the Trichromatic Theory( Young Helmholtz), the Opponent-Process Theory, and the Retinex Theory. How do each of these theories explain color vision? Which theory of color vision can explain negative color afterimages? What is color constancy and which theory of color vision can explain this phenomenon?

Trichromatic theory; humans have three different types of
cones, each sensitive to a different set of wavelengths

Opponent process theory: we perceive
color in terms of paired opposites: white-black, red-green, and yellow-blue.

Retinex theory: When information from various parts of the retina reaches the cortex, the cortex compares each of the inputs to determine the brightness and color perception for each area.

The opponent process theory explains negative color afterimages

Color constancy is the ability to perceive colors of objects despite a change in lighting, explained by the retinex theory

• What are the different types of color vision deficiencies and their characteristics.

• Protanopia: A type of red-green color blindness where individuals have difficulty distinguishing between red and green hues due to the absence of red photopigment.

• Deuteranopia: Another form of red-green color blindness, characterized by the absence of green photopigment, leading to similar challenges in color differentiation.

• Tritanopia: A rare blue-yellow color blindness that results from the absence of blue photopigment, making it difficult to distinguish between blue and yellow colors.

• Achromatopsia: A complete absence of color vision, where individuals see everything in shades of gray, often accompanied by light sensitivity and poor visual acuity.

• Visual Pathways: Which cells send visual information to the lateral geniculate nucleus? Which structure receives visual information from the lateral geniculate nucleus?

• Retinal ganglion cells: These cells send visual information to the lateral geniculate nucleus (LGN) of the thalamus, where initial processing of visual stimuli occurs.

• Primary visual cortex (V1): This structure receives visual information from the lateral geniculate nucleus, further processing the visual input for perception.

• Processing in the Retina: What is lateral inhibition? Why is lateral inhibition important in visual perception?

Lateral inhibition is a mechanism in the retina where the activation of one neuron inhibits the activity of neighboring neurons. This process enhances contrast and helps to sharpen visual perception by allowing the brain to detect edges and boundaries more effectively.

• What is the receptive field of a neuron? What are the differences between simple and complex receptive fields and between simple and complex cells?

Receptive Field: The portion of the visual field that excites or inhibits a specific
cell in the visual system of the brain

• Simple Receptive Fields:

  • response to light stimuli in specific orientations and positions

  • typically found in the primary visual cortex.

  • They exhibit a distinct on-center and off-surround organization.

• Complex Receptive Fields:

  • respond to stimuli regardless of their exact position within the receptive field

  • more complex patterns and motion detection.

  • less sensitive to the specific orientation of stimuli.

Simple cells:

fixed excitatory and inhibitory zones in their receptive fields;

found only in the primary visual cortex (V1).
have bar-shaped or edge-shaped receptive fields.
Complex cells:

Located in either V1 or V2

have receptive fields that respond to particular orientations of light

cannot be mapped into fixed excitatory and inhibitory zones.

receive their input from a combination of simple cells.

• What is the path of visual information in the visual cortex? Which structure sends visual information to the secondary visual cortex? Which structure receives information from the secondary visual cortex?

Input → Primary visual cortex → secondary visual cortex → visual association areas

The primary visual cortex processes initial visual input, and the lateral geniculate nucleus (LGN) of the thalamus sends visual information to the secondary visual cortex, while the secondary visual cortex receives this processed information for further interpretation.

• The Ventral and Dorsal Paths: What is the name of the visual path in the parietal cortex? What is the name of the visual path in the temporal cortex? What kind of impairments result from damage in the ventral stream? What kind of impairments and conditions result from damage in the ventral stream?

The visual path in the parietal cortex is the dorsal stream. The visual path of the temporal cortex is the ventral stream.

Dorsal stream damage:

know what things are but not where they are.

inability to reach out and grab an object

Ventral stream damage:

know where things are but not what

can grab objects but trouble identifying them.

• What is blindsight, visual agnosia, and prosopagnosia?

The point at which the optic nerve leaves the eye is known as the blind spot.

visual agnosia (meaning “visual lack of knowledge”). It usually results from
damage in the temporal cortex.

Prosopagnosia: The impaired ability to recognize faces without an overall loss
of vision or memory. People with prosopagnosia can identify if a person is
young or old, male or female, but they do not recognize who they are.

• What brain structures are involved in face recognition, color perception and motion perception?

Face recognition depends on several brain areas, including the occipital face
area, the amygdala, and parts of the temporal cortex, including the fusiform
gyrus, especially in the right hemisphere.

the V4 area for color perception,

Area MT (middle-temporal cortex, also known as area V5) and adjacent area
MST (medial superior temporal cortex) are important for motion detection.

Chapter 6, Module 6.1: Audition, pages 188 to 195

• What is amplitude and how is amplitude related to intensity and loudness? What is sound

frequency and how is sound frequency related to pitch? What is Timbre?

Amplitude: Intensity of a sound wave. In general, sounds of greater amplitude sound louder, but exceptions occur.

Frequency: Number of compressions per second, measured in hertz (Hz) of a sound.

Pitch: The perception of frequency

(the higher the frequency of a sound, the higher its pitch).

The third aspect of sound is timbre, meaning tone quality or tone complexity.

• The outer ear: What are the structures of the outer ear and the functions associated with each of these structures? How does the tympanic membrane respond to low and high frequency sounds?

• The outer ear includes the pinna (structure of flesh and cartilage attached to the side of the head) and the auditory canal.

• The pinna helps us locate the source of a sound by altering reflections of sound waves.

• The auditory canal guides sound waves from the external environment to the middle ear for processing. Sound reaches the tympanic membrane through the auditory canal

• The tympanic membrane vibrates in response to low and high frequency sounds, and those vibrations help differentiate high and low sounds

• The middle ear: What are the structures of the middle ear and the function these structures

serve?

• The middle ear is comprised of the tympanic membrane (eardrum), which vibrates at the same frequency as the sound waves that strike it.

  • Sound waves reach the tympanic membrane through the auditory canal.

  • The tympanic membrane is attached to three tiny bones (hammer, anvil, and stirrup).

• The inner ear: What are the structures of the cochlea? What are the auditory receptors called

and where are they located? How do sound waves result in the production of receptor

potentials (depolarization)?

• The cochlea contains three main structures: the scala vestibuli, scala media, and scala tympani.

• The auditory receptors are called hair cells, which are located within the organ of Corti, situated in the scala media.

• When sound waves enter the cochlea, they cause fluid movement, leading to the deflection of hair cells and resulting in the production of receptor potentials through depolarization.

• How frequency is represented according to each of the three theories of pitch perception: The

place theory, the frequency theory and the current theory?

Place Theory: Each area along the basilar membrane is tuned to a specific frequency and vibrates whenever that frequency is present.

Frequency Theory: We perceive certain pitches when the basilar membrane vibrates in synchrony with a sound, causing the axons of the auditory nerve to produce action potentials at the same frequency.

The current theory is a modification of both place and frequency theories:

For low frequency sounds (below 100 Hz), the basilar membrane does vibrate in synchrony with the sound wave in accordance with frequency theory. The pitch of the sound is identified by the frequency of impulses and the loudness is identified by the number of firing cells.

• What is amusia and absolute pitch?

Tone deafness or amusia: A disorder where individuals are seriously impaired at detecting small changes in frequency.

Absolute pitch or perfect pitch: The ability to hear a note and identify it accurately.

• The Auditory Cortex: Which lobe of the brain receives auditory information? To what kind of

stimuli does the primary auditory cortex (A1) respond? What is a tonotopic map?

• The Auditory Cortex: Located in the temporal lobe, it receives auditory information from the ears and processes sounds ranging from simple tones to complex auditory stimuli.

• The primary auditory cortex (A1) responds primarily to frequency and amplitude changes, allowing for the discrimination of different pitches and sound intensities.

• A tonotopic map : arrangement of neurons in A1 that correspond to different frequencies, with low frequencies represented in one area and high frequencies in another, facilitating the brain's ability to process sound systematically.

• Characteristics of middle ear deafness and inner ear deafness.

Conductive or middle-ear deafness: Failure of the bones of the middle ear to transmit sound waves properly to the cochlea.

Nerve or inner-ear deafness: Damage to the cochlea, hair cells, or auditory nerve that causes a permanent impairment in hearing in one to all ranges of frequencies. Nerve deafness can be inherited or caused by prenatal problem and early childhood disorders.

• Characteristics and definition of each of the following cues for sound localization: Differences in time arrival at the two ears (Inter-aural Time-Differences: ITD), difference in intensity between the ears (Inter-aural level differences: ILD), and phase difference between the ears (Inter-aural phase differences: IPD)

• Inter-aural Time-Differences (ITD): This cue relies on the slight difference in the time it takes for a sound to reach each ear, allowing the brain to determine the direction of the sound source based on which ear hears it first.

• Inter-aural Level Differences (ILD): This cue is based on the difference in sound intensity that reaches each ear, with sounds coming from one side being louder in the nearer ear than in the farther ear.

• Inter-aural Phase Differences (IPD): This cue is determined by the phase of the sound wave reaching each ear; sounds that arrive out of phase can help localize the sound source, particularly for low-frequency sounds.

• What cue for sound localization is useful for localizing high frequency sounds? What cue for

sound localization is useful for localizing low frequency sounds?

• High frequency sounds are primarily localized using Inter-aural Level Differences (ILD), as their shorter wavelengths are more effectively blocked by the head, creating a noticeable intensity difference between the ears.

• Low frequency sounds are localized using Inter-aural Phase Differences (IPD), since their longer wavelengths allow them to diffract around the head, making phase information more relevant for localization.

Chapter 8: Wakefulness and Sleep

• What is circadian rhythm? What behaviors/activities/physiological processes are controlled by

the circadian rhythm? In the absence of any time cues what would happen to your circadian

rhythm?

Circadian rhythm refers to the natural, internal process that regulates the sleep-wake cycle and other behavioral patterns, occurring roughly every 24 hours.

It influences various activities such as sleep, feeding, hormone production, cell regeneration, and other bodily functions.

In the absence of any external time cues, such as light or social interactions, the circadian rhythm may drift, leading to a desynchronization of biological processes, often resulting in sleep disturbances and impaired cognitive function.

• Setting and Resetting the Biological Clock: What is a "zeitgeber"? What is the importance of

zeitgebers?

Zeitgeber: Stimulus that is necessary for resetting the circadian rhythm. Light is

the dominant zeitgeber for land animals.

A "zeitgeber" is an external cue, such as light, temperature, or social interactions, that helps regulate the circadian rhythm by signaling to the body when to be awake or asleep. The importance of zeitgebers lies in their ability to synchronize biological processes with the external environment, ensuring optimal functioning of various bodily systems and promoting overall health.

• Jet Lag and Shift Work: When traveling across time zones, how does the direction of travel affect one’s adjustment to the new time zone? What would help someone adjust to jet lag? How to increase the alertness and efficiency of workers on night shifts?

Jet lag: A disruption of our biological rhythms due to crossing time zones.

b. Phase-delay: What happens to our circadian rhythms when we travel west, as

we stay awake late and awaken the next day already partly adjusted to the new

schedule.

c. Phase-advance: What happens to our circadian rhythms when we travel east,

as we tend to sleep and awaken earlier than usual.

People adjust best to night work if they sleep in a very dark room during the day and work under very bright lights at night

• The Suprachiasmatic Nucleus (SCN): What is the role of the suprachiasmatic nucleus in circadian rhythms? Where is the suprachiasmatic nucleus located?

Nucleus located above the optic chiasm in the hypothalamus. The SCN controls the rhythms for sleep and temperature. The neurons of the SCN generate impulses that follow a circadian rhythm.

• How Light Resets the Suprachiasmatic Nucleus (SCN): What is the name of the pathway that

connects the retina with the SCN? Where does the input from the eyes to the suprachiasmatic

nucleus, responsible for shifting the phase of the circadian rhythm, originate from? The

circadian rhythm is reset by input from special retinal ganglion cells. What kind of stimuli do

these retinal ganglion cells respond to?

RETINA → RETINOHYPOTHALAMIC PATH → SUPRACHIASMATIC NUCLEUS

The SCN is reset by the retinohypothalamic path that extends directly from the retina to the SCN.

The input from the eyes originates from retinal ganglion cells that are sensitive to light, particularly blue wavelengths, which play a crucial role in regulating our sleep-wake cycles.

These ganglion cells respond to slow changes in duration of light

• The Biochemistry of the Circadian Rhythm: How do PER and TIM proteins influence the circadian rhythm?

Early in the morning, the concentration of both PER and TIM are low and they increase during the day. In the evening, protein concentrations are high and result in sleepiness. During the night, the genes stop producing the proteins

• Melatonin: How does melatonin affect the circadian rhythm? When do the secretions of

melatonin begin?

SCN regulates waking and sleeping by controlling the pineal gland which

releases the hormone melatonin, which increases sleepiness. Melatonin release

usually starts 2 or 3 hours before bedtime.

b. Melatonin stimulates receptors in the SCN to reset the biological clock.

• What kind of information a polysomnography shows? What kind of information an electroencephalograph shows?

Polysomnograph: A combination of EEG and eye-movement records

Electroencephalograph: Measures electrical activity in the brain, providing insights into different sleep stages and brain wave patterns.

• The Stages of Sleep: Characteristics of stages of sleep 1, 2, 3, and 4.

• Stage 1: Light sleep where the person can be easily awakened, characterized by slow eye movements and reduced muscle activity. LOW VOLTAGE WAVES

• Stage 2: Deeper sleep with sleep spindles and K-complexes in the EEG, where the heart rate slows and body temperature decreases. SLEEP SPINDLES AND K-COMPLEXES (HIGH ALT WAVES)

• Stage 3: Deep sleep, also known as slow-wave sleep, featuring delta waves in the EEG and is crucial for restorative processes. SLOW, LARGE AMPLITUDE WAVES

• Stage 4: The deepest stage of sleep, essential for physical recovery and growth, with the highest proportion of delta waves. (SLOW, LARGE AMPLITUDE WAVES)

• Characteristics of paradoxical or REM sleep.

• REM Sleep: Characterized by rapid eye movements, increased brain activity, and vivid dreaming, it plays a vital role in emotional regulation and memory consolidation.

• What is paradoxical about paradoxical sleep?

Named “paradoxical” because it is deep sleep in some ways and light in others.

• Cycle of sleep: What happens to REM as the night progresses? What happens to stages 3 and 4 sleep as the night progresses?

Early in the night, stages 3 and 4 predominate, but toward morning, stage 4 grows shorter and REM grows longer.

• What are the main differences between REM and NREM dreams.

• REM dreams tend to be more vivid and narrative-driven, while NREM dreams are often more fragmented and less memorable.

• Brain Structures of Arousal and Attention: What is the role of the locus Coeruleus, the reticular formation, and the basal forebrain in arousal? What neurotransmitter is released by the locus coeruleus? What neurotransmitter is released by the basal forebrain?

Reticular formation: A structure that extends from the medulla into the forebrain. Lesions through the reticular formation decrease arousal.

Locus coeruleus:

inactive at most times

emits impulses, releasing norepinephrine, in response to meaningful events.

important for storing information.

usually silent during sleep

Basal forebrain: releases acetylcholine which promotes arousal and cortical activity. Neurotransmitter GABA

• What is the role of GABA in Sleep.

GABA is an inhibitory neurotransmitter that helps regulate sleep by promoting relaxation and reducing neuronal excitability, thus facilitating the transition to sleep and maintaining sleep stability.

• Brain Functions in REM Sleep: Does brain activity increase during REM? If so, in what parts of the brain?

During REM sleep, activity increases in the pons, the limbic system, and the

parietal and temporal cortex of the brain.

Activity decreases in the primary visual cortex, the motor cortex, and the dorsolateral prefrontal cortex.

• Sleep Disorders: Characteristics of sleep apnea, narcolepsy, REM behavior disorder, and Sleep Walking.

• Sleep Apnea: Characterized by repeated interruptions in breathing during sleep, leading to fragmented sleep and excessive daytime sleepiness.

• Narcolepsy: A neurological disorder marked by uncontrollable episodes of sleep during the day, often accompanied by cataplexy, sleep paralysis, and hallucinations.

• REM Behavior Disorder: A condition where individuals act out their dreams during REM sleep, potentially leading to injury.

• Sleep Walking: A disorder that involves getting up and walking around while in a state of sleep, typically occurring during non-REM sleep.

• What are the main symptoms of narcolepsy and their characteristics?

• Excessive daytime sleepiness: Persistent and overwhelming urge to sleep during the day, often leading to unplanned naps.

• Cataplexy: Sudden loss of muscle tone triggered by strong emotions, resulting in temporary weakness or paralysis.

• Sleep paralysis: Inability to move or speak while falling asleep or waking up, often accompanied by a feeling of pressure on the chest.

• Hypnagogic hallucinations: Vivid and often frightening hallucinations that occur while falling asleep, which can be mistaken for reality.