Sensation, Perception, and Light

Sensation and Perception

• Sensation can be distinguished from perception.
• Absolute threshold and difference threshold are important concepts.
• Attention, motivation, and sensory adaptation affect perception.
• The retinal image helps us see near and far objects with size cues.

Mental Process

• Mental process bridges the gap between retinal image properties and visual experience.
• It extends beyond everyday experience, and relies on unconscious inferences.
• The unconscious mind interprets the retinal image using eye movement cues.
• Indirect perception involves the mind first presenting an idea of an object and then directing attention to it.

Light and Color Vision

• Light is electromagnetic radiation creating electrical signals for the mind to create sensation.
• ROYGBIV is the spectrum: Red, Orange, Yellow, Green, Blue, Indigo, Violet
• The trichromatic theory of color vision states that all colors are produced by combining red, green, and blue.
• The opponent-process theory codes color in opponent pairs (black-white, yellow-blue, red-green).
• Afterimages are are related to the continuation of visual sensation after stimulus removal.
• The trichromatic theory applies to visual processing on the retina.
• Cells respond to visual stimuli in a way consistent with the opponent-process theory once the signal moves from the retina.

Parts of the Eye

• The pupil controls the amount of light entering the eye.
• The lens focuses light rays on the retina through accommodation.
• Presbyopia is age-related loss of focus.
• The retina contains receptors (rods and cones).
• Cones: used in bright light, and facilitate fine detail and color vision.
• Rods: are best in dark environments, and facilitate blurry/peripheral vision.
• Transduction is the conversion of sensory stimulus energy to action potential.
• Visual neuroscience studies how visual features are represented in the brain and firing patterns along the visual pathway.

Thresholds

• Absolute threshold: the minimum stimulus energy needed for detection 50% of the time.
• Just noticeable difference: intensity needed to detect change.
• Stimuli below conscious awareness can still be processed.

Eye Anatomy

• Fovea: indentation in the back of the eye that focuses images perfectly (cones).
• Rods: do no process color function and work well in low light for cones
• Cones work well in bright light.
• The optic nerve carries cells that exit through the back of the eye.
• The optic chiasm is where nerves from each eye merge just below the brain.

Retinal Ganglion Cells (RGC)

• Retinal Ganglion Cells (RGC): help identify measured firing rates under different conditions.
• Respond to enhance contrast when shone light on the retina.
• Display activity when there is a big contrast between light and dark.
• Relate to edge detection and object recognition.
• Ganglion cells are the first neurons in the retina to respond with action potentials. The response of ganglion cells depends on the cells that feed them.
• The receptive field is divided into two regions (center and surround).
• ON-center/OFF-surround cells increase response with flashing small bright light spots as action potential.

Visual Pathways

• Primary visual cortex occurs as neurons respond to the retinal image, and electrical signals occur.
• Dorsal stream ("where" pathway): extends into movement areas of the brain (posterior parietal lobe)
  • Damage can cause optic ataxia preventing the use of vision to guide movement.
• Ventral stream ("what" pathway): extends into memory areas of the brain (inferior temporal lobe)
  • Damage can cause visual agnosia, which is an inability to recognize objects.

Processing Types

• Bottom-up processing: sensory information from a stimulus drives a process.
• Top-down processing: knowledge and expectancy drive a process.

Sensory and Attention

• Sensory adaptation: getting used to constant stimuli in the environment.
• Factors that affect perception:
  • Attention: what's in site will be most preserved.
  • Motivation: perceptions, shift our ability to discriminate between sensory input and background noise.
• Inattentional blindness: failure to notice something fully visible due to attention being directed elsewhere.
• Signal detection theory: being able to identify a stimulus in a distracting background.

Amplitude and Wavelength

• Amplitude: amplitude of a wave is the distance from center line to to the top/bottom point (trough).
• Wavelength: refers to the length of the wave from one peak to the next
  • Related to the frequency of the given waveform, number of waves passing a given point over time (Hertz- Hz).

Light Waves

• The visible spectrum is the portion of the larger electromagnetic spectrum that can be seen
• The human visible spectrum is associated with range of 380 - 740 nm.

Sound Waves

• Physical properties of sound waves, associated which our perception of sound.
• Audible range for humans: 20 - 20,000 Hz.
• The frequency of a sound wave is associated with which our pitch.
• Place theory: Perception of pitch corresponds to where vibration occurs along the cochlea,
• Frequency Theory: pitch corresponds to the rate at which hair cells vibrate.
• Amplitude is the perception of sound. amplitude.
• Low is quiet and high amplitude is loud.
• Timbre refers to the sound's purity, and it is affected by the complex interplay of frequency, amplitude and timing of sound waves.

Parts of the Ear

• Outer Ear: pinna funnels sound waves to the middle ear.
• Middle Ear: vibration of the eardrum amplified by three tiny bones (malleus, incus, stapes).
• Inner Ear: vibrations converted to a neural signal in the cochlea.
• Fluid-filled coil in the inner ear contains receptors for hearing.
• Stimulation of hair cells transduced into patterns of neurons firing.

Auditory Issues

• Presbycusis: Age-related hearing loss that starts with higher frequencies.
• Sensorineural hearing loss: hearing problems, failure to transmit neural signals from the cochlea to the brain.
• A disease that results in this this is Meniere disease.
• Meniere disease symptoms: constant ringing or buzzing in the inner ear and vertigo.
  • Cannot be cured with hearing aids.
• Congenital deafness: not being able to hear from birth.
• Conductive hearing loss: problem in delivering sound energy to the cochlea.
• Hearing aids help with this problem.
• McGurk effect: hearing how different background sounds come together and create hearing.

Approaches and Theories

• Traditional approaches create illusion about visions, and minimizes movements in the body.
• Ecological approaches better approach stimulation.
• Perception unfolds overtime, and doesn't stay as a static series of images frozen in time.
• Small moments can correct errors of perception.
• Alhazen: experiment- change that the way we see light. Prove: light travels in a straight line, experiment was done through the product called camera obscura.
• Kepler: vision experiments, revealed that visions occur through a picture of the visible thing.
• Affordances: opportunities for action.

Measuring Conciseness

• Consciousness: Awareness of internal and external events.
• It's estimated that 15-20% of unresponsive patients have covert consciousness.
• Light information sent from he retina to the suprachiasmatic nucleus in hypothalamus (biological clock).
• Suprachiasmatic nucleus sends signals to the pineal gland: increases production of the hormone melatonin as light decreases.
  • Melatonin makes you feel sleepy.
  • Blue light from smartphones suppresses melatonin.
• Sleep/wake cycle is a circadian rhythm: biological activity that rise and fall in an 24-hour cycle.
• Biological clock corrects itself with reference to environmental cues, but can function without them.
• Younger adults and more evening people, older adults are more morning people in circadian rhythms.

Sleep

• Sleep deprivation occurs when you don't get enough sleep.
• Get or feel cold when you don't get enough sleep.
• Evolutionary perspective: conserving our energy, staying away from predators.
• Cognitive perspective: help us think and function better.
• Brains don't turn off when we go to sleep in stages:
• EEG: Electro-encephalograph: which records brain activity.
• EMG: Electro-myograph: which records muscle activity.
• EOG: Electro-oculography: Records eye movements.
• Mirror neurons: Groups of neurons tend to fire at the same rate and at the same time.
• Summed activity of neurons is measured by EEG as a brain wave.
• Pass through 5 stages where brain waves are distinguishable from awake brain waves.
• Stage of Sleep Cycle: brain waves are awake and alert, higher frequency and small amplitude.
• In the sleep cycle, brain waves get slower frequency and larger amplitude in first four stages.
• Stage 1: Myoclonic jerks, and hypnagogic imagery.
• Stage 2: Sleep spindles, heart rate slows, body temperature decreases.
• Stage 3-4: Slow wave sleep or delta wave sleep.
• Deepest stage of sleep, feel refreshed in the morning.
• Dreaming occurs instead of 1: Brainwaves resemble the waking brain, almost no muscle-tension.
• Lucid dreaming: Experience of becoming aware that you are dreaming. Sleep cycle repeat about 4-5 times per night.

Dreaming Theory

• Activation synthesis model argues that what our brain interprets in the day when it is awake, the brain attempts to make sense or construct a story out of random brain activity during REM sleep.
• People often dream about problems that are occurring in their waking life in the Cartwright's theory.
• Memory consolidation replayed in REM sleep.
• Sleeping is important as it strengthens our memory to stay in our brain in memory consolidation theory of dreaming.
• Psychoactive drugs selectively after neurotransmitter activity in the brain.

Intoxicants Effect

• Alcohol: sedative and depressant effects
• Alcohol tends to defeat the central nervous system activity.
• Slow thinking, impaired concentration, walking and muscular coordination.
• If the alcohol level is more than 4: you will become unconscious.
• The effects of the psychoactive drugs through their interactions with our endogenous neurotransmitter systems
• Stimulants: increase heart rate, blood pressure, body temperature.
• MDMA (Ecstasy): high toxicity to the brain.
• Sedative Hypnotics Depressants Decreased heart rate, blood pressure, motor disturbance, memory, decreased respiratory function, and death. Opiates
• Heroin decreases pain, decreased gut motility, decreased respiratory function Hallucinogens
• Marijuana increases heart rate and blood pressure that disappears over time.

Learning Behaviour

• Learning: defined as a change in behaviour or thought through our experience.
• Habituation: Reduced response when a stimulus is presented repeatedly.
• Classical conditioning: Automatic response
• Stimulus generalization: Responding to a new stimulus in a the way that you do to previously conditioned stimuli (CS).
• Phobia: developed from classical conditioning
• Changes in whether you like or dislike the stimulus based on positive or negative stimulus. Aversion therapy- converting a behaviour into a good one by pairing it with unpleasant stimulus
• Operant conditioning: Learning in which responses come to be controlled by their consequences

Reinforcements

The Reinforcer: An event or a behaviour that is either continued or decreased based on the consequences

• Shaping by successive approximations
• If the dog follows the rule through a kind of behaviour, it will be continued and if not a different behaviour will be acted.
• Positive reinforcement- continued behaviour.
• Negative reinforcement- decreased behaviour to get the desired rule followed.

Schedules

• Schedule of reinforcement either continuos orpartial. - Partial reinforcement behaviours are learned doing things differently:

  • Fixed-ratio schedule: reinforcement after a set number of non-reinforced responses.,
  • Variable- ratio schedule: after a variable number of non-reinforced responses.
  • Fixed-interval schedule:reinforced after a set amount of time .

• Observational learning

• We learn by watching others and then imitating or modeling. Do what you observe.

• Mirror neurons

  • Neurons Firing when performing an action and observing that same action being performed.

• Conditioning: Learning connections between events and behaviour.

• Pavlov's experiment with dogs, associating different sounds of foods, if they recognize or not.

• Conditioned responses are not permanent as the learned response may not stay the same and fade away over time.