Lecture 7
Sensation and Perception
Define sensation = process by which our sensory receptors detect physical energy (stimulus) from the environment and convert it into neural signals. Takes place at the level of the sensory receptor.
Define perception = process by which our brains organize and interpret our sensations, enabling us to recognize objects and events as meaningful.
Understand the difference between sensation and perception = Sensation is input about the physical world obtained by our sensory receptors, and perception is the process by which the brain selects, organizes, and interprets these sensations.
Sensing the world: understand, be able to define and provide examples for the following basic principles - we perceive the world not exactly as it is, but as it is useful and important for us to perceive.
Sensory receptors: We don’t detect all the energy in our environment. Why? Because we can only detect the energy that our sensory receptors can sense.
Absolute threshold - Minimum stimulation needed to detect a particular stimulus and we don’t detect all stimuli all of the time. To function effectively, we need stimuli above threshold
Signal detection theory - Our psychological states affect how sensitive we are to external stimuli. It predicts how and when we detect the presence of a faint stimulus amid background stimulation.
Difference threshold (just noticeable difference) - minimal change in a stimulus that can just barely be detected.
Sensory adaptation - diminishing sensitivity to an unchanging stimulus. The benefit is the freedom to focus on informative changes without uninformative background stimulation.
Visual processing: Brain mechanisms of visual sensation and perception - Light energy is detected by special receptors in the eye called photoreceptors.
Light energy: visible spectrum (from 400 to 700 nm)
Transduction - the transformation of stimulus energy (sights, sounds,smells) into neural impulses. It takes place in the retina.
Sensory receptors- located in the retina
Rods - doesn't show colors
Cones - show colors
Understand the difference between rods and cones
Where are they located within the retina - back of retina
What types of cells are the rods and the cones? Photoreceptor cells
Fovea - Central point in the retina around which the eye’s cones cluster
Optic nerve (what retinal cells?) - Carries neural impulses from the eye to the brain. Optic nerves connect the eye to the thalamus in the middle of the brain, and the thalamus connects to the visual cortex.
Where are the cell bodies of the optic nerve cells?
Where do the axons project to?
Blind spot - Point where the optic nerve leaves the eye because there are no receptor cells located there.
Where is it? At the back of the eye, where the optic nerve connects to the retina.
What is its significance?
Basic visual pathway in the brain (eye to thalamus to visual cortex)
Feature detection neurons
Where in the brain are they located? Usually located in the temporal lobe- fusiform area.
Why are they significant? Teams of cells that respond to more complex information (i.e.faces or movement)
Supercell clusters in temporal lobe- responsible for more complex perception
Fusiform area (responsible for detection of faces) in temporal lobe
Prosopagnosia - a neurological condition characterized by the inability to recognize the faces of familiar people
Bottom-up vs top-down processing - Top-down and bottom-up processing are two types of processing that work together to help us make sense of the world.
Bottom-up processing - This process starts with sensory receptors and is based on incoming data. It starts with no preconceived idea of what you're looking at and allows the stimulus to influence your perception.
Top-down processing - In this process, our previous experiences, expectations, beliefs and memories affect our perceptions.
Give examples:
Lecture 8
Note that I will use neuroplasticity and plasticity of the brain interchangeably
Hemispherectomy as an extreme example of neuroplasticity
Hemispherectomy - removal of right hemisphere
Understand the static view of the brain
Understand current view: The brain is plastic
What is neuroplasticity - The brain’s ability to change and reorganize itself over time.
Structural vs synaptic plasticity
Structural - Changes to the number of neurons, Changes to the number of axon terminals and dendrites, leads to new connections between neurons and new information processing.
Synaptic - With repeated communication between neurons makes the synapse stronger and with repeated lack of communication between neurons makes the synapse weaker.
What aspects of brain function are subjective to change?
What are the biomarkers of structural plasticity?
What are the biomarkers of synaptic plasticity ?
Examples of neuroplasticity
o Plasticity after learning - Rats raised in an enriched environment develop a thicker
cortex and increased dendritic branching.
o Plasticity after stress - Rats raised in a stressed environment develop a smaller dendritic branching.
o Plasticity after exercise - Exercise is known to increase trophic factors that facilitate the survival of neurons, The thickness of the cerebral cortex declines in old age but much less
in those that are physically active, and Exercise is known to increase trophic factors that facilitate the survival of neurons.
• Plasticity after brain damage - Axon sprouting, collateral sprouts are new branches formed by other non-damaged axons that make synapses with vacant areas.
What are collateral sprouts and why are they relevant? Collateral sprouts are new branches formed by other non-damaged axons that make synapses with vacant area and relevant because they represent a natural mechanism for the brain and spinal cord to partially recover function after damage by forming new connections with denervated tissue.
Lecture 9
Circadian Rhythms
Endogenous biological rhythms - Endogenous biological rhythms that help
us deal with fluctuations in the environment.
Circadian rhythms - Endogenous (generated from within) rhythms control or initiate various biological processes. Regulate the sleep/ wake cycle. Also regulate other processes such as: the frequency of eating and drinking, body temperature, secretion of hormones, volume of urination and sensitivity to drugs.
Circannual rhythms - seasons, migration
What gives rise to biological rhythms? Neural system that times behavior
Where in the brain is the biological clock? What is its name? Suprachiasmatic nucleus (SCN) in the hypothalamus.
What is the relation between light and the SCN? Light resets the SCN via a small
branch of the optic nerve known as the retinohypothalamic path (from the retina in your eye to the hypothalamus) If light is available, this pathway signals the SCN that it still not time
to sleep.
Why is the retinohypothalamic pathway relevant? It is essential for the resetting of circadian phase by light and, indirectly, for the photic regulation of pineal melatonin synthesis.
What is thought to be the relation between smart phones and tablets and biological rhythms? Smartphones—like laptops, tablets, and televisions—emit something called blue light, which is a type of light that the brain interprets as daylight
What is the mechanism by which blue light might affect circadian rhythms? The blue light actually suppresses melatonin (a hormone that affects circadian rhythm and should increase when you are preparing for bedtime). Your brain feels stimulated. This is fine if you’re looking at your smartphone’s screen at noon, but if you’re looking at the screen at midnight, your brain is going to get confused and think that the sun is out—making it even tougher to fall asleep.
What is sleep pressure? Sleep pressure is the desire to sleep and is correlated with the amount of adenosine in your brain.
What is the biological marker of sleep pressure? You can think of adenosine as the chemical barometer that will continuously register the amount of elapsed time since you woke up this morning.
What does adenosine do? Turns down the volume of wake-promoting regions in the brain and turns on the volume of sleep-promoting regions in the brain.
How is napping thought to affect adenosine? Taking a long nap in the afternoon will reduce the levels of adenosine in the afternoon and might make it difficult to fall asleep at night.
o How does coffee act in the brain? Caffeine blocks the adenosine receptor tricks the brain by muting the adenosine signal.
Sleep
What is an electroencephalogram? a test that detects electrical activity in your brain using small, metal discs (electrodes) attached to your scalp. Your brain cells communicate via electrical impulses and are active all the time, even when you're asleep. This activity shows up as wavy lines on an EEG recording.
What are the main stages of sleep? Non-REM Sleep - Consists of 4 stages: Stage 1, Stage 2, Stage 3, Stage 4 and REM- sleep (rapid eye movement or paradoxical sleep)
Brain activity during the different stages of sleep
Understand the 90 minutes cycles of sleep - With each 90-minute cycle, stage 4 sleep decreases and the duration of REM sleep increases.
Understand how Non-REM and REM sleep increase or decrease through the night
Understand the main characteristics of non-REM sleep - Four stages, Synchronized/slow brain activity (Slow wave sleep SWS), Not-vivid dream, Muscle tone, Posture maintained, Decreased as night progresses, Entire body moves
Understand the main characteristics of REM sleep - One stage, Desynchronized and fast brain activity (Paradoxical sleep), Vivid dreams, Atonia, Posture completely lost, Increases as night progresses, Eye movement
What is atonia and how does it relate to sleep? No tone; complete muscle inactivity produced by the inhibition of motor neurons; no movement of the body except for eyes
Why do we sleep? No one knows
Understand how sleep might have been selected by evolution? Sleep emerged in evolution to preserve energy and protect us during the time of day when there is little value and considerable danger.
Understand the restoration theory of sleep - sleep restores the immune system and repairs body and brain tissue.
Understand how lack of sleep might be related to the development of Alzheimer’s disease - Scientist are investigating if lack of sleep might lead to the development of Alzeihmer’s disease (accumulation of brain proteins proteins).
Understand how sleep is relevant to memory - Experiences of the day are often replayed during sleep, strengthening those brain connections and making them more long-lasting.
Peaks of wakefulness
What are chronotypes? Some of us are more alert and active in the morning, some of us in the middle of the day and some of us in the evening, These differences affect when we feel tired and when we are able to sleep, These individual differences in circadian typology are referred
to as chronotypes
What are the different types of chronotypes? Morning type-larks, night owls, and in between types
Understand how circadian rhythms are altered in adolescence. The circadian rhythm of teenagers shifts, Children and older adults have internal clocks set to make them sleepy in the evening, around 8 or 9 p.m., This shifts to 10 or 11 p.m. in Puberty, Teenagers are biologically programmed to go to sleep later.
Sleep loss
Understand all the consequences of sleep loss (we talked about many) - academic performance: diminishes productivity (leads to more hours needed to fulfill school requirements), ability to concentrate (leads to reduced ability to study), increases the tendency to make mistakes (leads to more errors in exams), affects memory consolidation.
Reaction time: Slow responses for those operating equipment, piloting or diving, Increased errors in visual attention tasks (reading X-rays, performing surgery),Driver fatigue has contributed to an estimated 20% of American traffic accidents
Obesity: Increases ghrelin, a hunger arousing hormone, Decreases leptin, a satiety hormone, Increases cortisol, a stress hormone that stimulates the body to make fat
Depression
Mood - leads to irritability and for students, lack to sleep leads to more conflicts in friendships
and romantic relationships.
Understand how much sleep we need according to the National Sleep Foundation
Lecture 10
What is consciousness? Consciousness is how we know we exist
Is consciousness the same as the mind? NO
If not, how are they different? Consciousness is one quality of the mind, Consciousness is the quality of the mind that allows us to know that we exist, Consciousness is the quality of the mind that allows us to have a sense of self that observes ourselves and the world around us.
Interaction between attention and consciousness - We are not conscious of everything that surrounds us. Through selective attention, your conscious awareness focuses, like a flashlight beam, on only a very limited aspect of all that you experience, Our conscious awareness processes only a small part of all that we experience and this is called selective attention.
Gorilla in the basketball experiment
What does this experiment reveal? Failing to see visible objects when our attention is directed elsewhere.
• Define selective inattention, also called inattentional blindness - Inattentional blindness is a by-product of what we are really good at: focusing attention on some part of our environment.
• Define change blindness - failure to notice change in the environment.
Lecture 11
Learning - The process of acquiring, through experience, new and relatively enduring information or a relatively permanent change in behavior. Learning allows us to adopt to our environment and survive.
Associative learning - when an organism makes connections between stimuli or events that occur together in the environment.
Classical conditioning - (two stimuli are paired together)
Classic Pavlov experiment - dog and bell experiment
Unconditioned stimulus (UCS) - they are inherently meaningful to the animal and the response that they produce does not need to be learned. any stimulus that will naturally ELICITS a response- without learning.
Conditioned stimulus (CS) - A situation in which one signal, or stimulus, is given just before another signal. a stimulus that has no importance to the organism until it is paired with something that does have importance.
Neutral stimulus (NS) - don't have any significant value for the animal. any stimulus that does not naturally elicits a response.
Drug addiction - If one always takes a drug of abuse in a particular context, the context (NS) can become a CS and trigger the desire for the drug
Eating patterns - If one always eats in a particular context, the context (NS) can become a CS and trigger the desire for food, even if you are not that hungry.
Understand the role of classical conditioning in human emotions - Watson believed that human emotions and behaviors are merely a bundle of conditioned responses (conditioned emotional reactions or CERs)
Classical conditioning processes:
Acquisition - association between a neutral stimulus and an UCS
In what order and when do the UCS and NS need to be presented for
acquisition to occur? The neutral stimulus needs to come before the unconditioned stimulus –biologically adaptive. Classical conditioning prepares the animal for good or bad events
Extinction- When the CS (bell) is not followed by the UCS (food), the CR (salivation) begins to decrease and eventually causes extinction.
Spontaneous recovery- After a rest period, an extinguished CR (salivation) spontaneously recovers, but if the CS (bell) persists alone, the CR becomes extinct again
What is recovered during spontaneous recovery? CR
What is necessary for spontaneous recovery to occur? A previously extinguished conditioned response must reappear after a period of time without exposure to the conditioned stimulus.
Generalization - Tendency to respond to stimuli similar to the CS is called generalization
Discrimination - Discrimination is the learned ability to distinguish between a conditioned stimulus and other stimuli that do not signal an unconditioned stimulus.
Pavlov’s legacy - Classical conditioning is one way all species learn to adapt to their environment. Learning can be studied objectively. It provides a scientific model for psychological science.