Sensation and Perception Intro

Intro to Perception

• The study of sensation and perception in psychology draws from biology, physics, chemistry, biochemistry, anatomy, and physiology
• Sensation and perception relates to how we respond to our environment
• It is one of the earliest topics in psychology

Sensation

• Sensation involves the activation of sensory receptors by physical stimuli
• Transduction, or converting energy into a neural impulse, is performed by receptor cells
• Humans have roughly 7-12 senses or perceptions

Perception

• Perception is the interpretation of sensory information and response by the central nervous system (CNS)
• Our senses can drive our decisions through bottom-up processing
• Top-down processing entails that our experiences also play a role in driving our perception

Phenomenology

• Perception is based on phenomenology, which is our understanding of a perception
• Cognitive penetration-phenomenology can change based on one's emotions and cognition.
• Cognitive impenetrability entails that phenomenology cannot change with one's emotions and cognitions.

History of Perception

• Early perception study involved the Greeks, focusing on column tapering and motion aftereffects
• Constructivists study unconscious inferences (Helmholtz)
• Research entails that sensation gives enough info (Hering)
• Psychophysics examines the relationships between physical stimulus and perception, including Weber's Law (Just Noticeable Difference) and Fechner's Law

20th Century and Beyond

• The Gestalt approach views the world in patterns and order, emphasizing nature over nurture
• Direct perception occurs without interpretation
• The Information-Processing Approach involves information flowing from one thing to another
• The Computational Approach aims to model the brain as a computer

Neuroscience Methods

• Neuroscience methods study perception at the neuron level
• Microelectrodes and selective cells are used in animal brain studies
• Brian damage cases, like agnosia and aphasia, are studied
• Neuroimaging techniques used include fMRI, MRI, EEG, MEG, and TMS

Magnitude Estimation and Other Methods

• Magnitude estimation involves two types:
  • Subjects estimating stimulus intensity based on a standard
  • Subjects estimating stimulus intensity based on their own standard
• Examples include rating pain on a scale of 1-10 and rating the spiciness of peppers
• The absolute threshold is not absolute and is susceptible to response compression
• Estimation response increases with, but at a lower rate, stimulus intensely
• Pain is different given it involves response expansion
• Estimation response increases with stimulus intensity at a greater rate

Psychophysics

• Psychophysics studies absolute and difference thresholds
• It entails just noticeable difference
• Weber's Law and JND have a linear relationship
• Fechner's Law has a logarithmic relationship
• Steven's Power Law has a power equation

Signal Detection

• Signal Detection Theory determines whether a signal is detected based on sensory sensitivity and judgment criteria
• There are four possible outcomes: correct detection (hit), miss, false alarm, or correct rejection
• To properly gauge the probabilty there's detection one needs to account for noise, signal, d-prime, and criterion value

Touch and the Skin Senses

• Mechanoreceptors are receptors which specialize in touch
• SAI (slow-acting, surface)- Merkel discs: Respond to sustained pressure, two-point threshold, offer high spatial resolution and fine manual control; sensitive to patterns and texture
• SAII (slow-acting, deep)- Ruffini endings: Low spatial resolution; good at stretching, grasping objects
• FAI (fast-acting, surface)-Meissner corpuscles: Small receptive fields, accuracy, Detect "slip" or feel of surface of objects, detect beginning and end of touch
• FAll (fast-acting, deep)- Pacinian corpuscles: Large receptive field, responds to high frequency vibrations; used in fine motor control
• Proprioception is the kinesthetic awareness of limb movement
• Muscle spindles-embedded in muscle tissue which sense contraction and relaxation
• Joint receptors provide info on how far a joint is bent or stretched, and how much more it can move
• Golgi tendon organs are receptors in tendons that measure force of muscle contraction
• Thermoreceptors sense temperature
• Cold fibers- respond to temps less than 30C
• Warm fibers- respond to temps above 36C
• Temperatures below 17C or above 43C are perceived as pain
• Paradoxical heat occurs when it's so cold that it burns
• Pain Perception Involves the following
• Nociceptors- free nerve endings
• A-delta fibers- myelinated, quick
• C-fibers- unmyelinated, chronic or throbbing
• Pruceceptors inhibit itching

Neuroanatomy of touch & Neurons

• Touch receptors travel to the spinal cord through the dorsal root
  • Includes afferent fibers, which carry muscle signals to the brain
  • The cell body that has the nucleus is found in the dorsal root ganglion
  • The ventral root carries signals from the brain to muscles
• Mechanoreceptors and proprioceptors go to the brain through the dorsal column-medial lemniscal pathway.
• Nociceptors and thermoreceptors travel through the spinothalamic pathway
• Both pathways lead first to the ventral posterior nucleus of the thalamus and then to the somatosensory cortex.
• Receptors from the left side of the body project to the right side of the brain, and the right side of the body to the left side of the brain.

Neuroanatomy of Pain

• Reflex action goes to the spinal cord and back again, bypassing the brain to avoid damage
• Signals end up in the somatosensory cortex in the parietal lobe where pain is perceived
• Pain signals interact with descending fibers and large diameter fibers at the substantia gelatinosa of the dorsal horn
• Gate control theory of pain perception entails the pain can be inhibited,
• Analgesia is the process of relieving pain while endorphins are produced by the body
• Pain can also be psychosomatic
• Phantom Limb symptoms can be mitigated through mirror therapy

Balance

• Haptic perception involves active touch to identify objects
• The development of haptic perception begins with infants using their mouth to touch
• Finger use is developed over time
• Haptic perception helps form the somatosensory map and homunculus
• Loss of touch is referred to as tactile agnosia
• The Vestibular System entails the sense of head movement in space through semicircular canals next to the inner ear, one in each direction of head movement
• hair cells in semicircular canals respond to movement
• suspended in liquid (endolymph), the hairs move with the liquid
• Otoliths (rocks) on top of hair cells respond to gravity and acceleration to amplify hair movement

More on balance

• Balance is a combination of senses, including:
  • Vestibular sense
  • Proprioception
  • touch/haptic
• Haptics determines the feel of the surface you are standing on, including if it's slippery, firm, or shifting
• Vision dominates everything and the brain perceives gravity acting downward

The Chemical Senses

• Olfaction (smell) and gustation (taste) are our chemical senses
• The Just Noticeable Difference (JND) is different for different scents
• Humans have 350 different olfactory neurons, each a different chemical class
• Scent identification can be difficult due to the tip of the nose phenomenon, where one can't name it but can pick off a list
• Odor imagery is not common
• Anosmia is a total lack of smell
• Phantosmia is a disorder where the sufferer perceives various smells without the presence of any specific odorant

The Anatomy of Smell

• Olfactory receptor neurons are smell cells located in the olfactory epithelium
• There are about 20 million neurons and 350 different types in humans; all are replaced every 28 days
• The olfactory nerve connects to the olfactory bulb
• Glomeruli act as a relay station for smell, forming a map of smell that projects to the amygdala (emotion)
• The Piriform cortex serves as a olfactory cortex
• The Anterior PC- representation on chemical structure , Posterior PC- representation on dor quality
• The Orbitofrontal cortex- smell- emotion association
• The Trigeminal nerve- transduces the feel of smell

Taste and Flavor

• The five basic tastes are sweet, salty, sour, bitter, and umami (savory, meat, protein, MSG)
• Sweet, salty, and umami tastes encode information on nutrition
• Sour and bitter tastes serve as a warning for toxins or inedible food

The Anatomy of Taste

• The anterior insular cortex is the primary cortex for taste and is part of the frontal cortex
• Taste receptor cells and presynaptic cells are found on taste buds
• Taste buds are found in papillae on the tongue and can receive any taste
• Fungiform papillae are around the edges and on top
• Foliate papillae are at the back edges
• Circumvallate papillae are in the back
• Filiform papillae are all over and have somatosensory receptors
• Flavor is a combination of taste, smell, somatosensory cells, the trigeminal nerve, thermoreceptors, and nociceptors
• Chili peppers activate trigeminal nerve nociceptors in fungiform papillae
• The enjoyment of food is related to the orbitofrontal cortex

Visual Attention

• Attention is the active focusing of cognitive resources on a particular phenomenon
• Alertness is a heightened state of vigilance, being mindful of the surrounding
• Awareness is conscious mindfulness of something, real or imagined
• Attention is how one directs focus to some stimuli
• Selective attention involves purposefully directing cognitive resources toward a task or stimuli
• Divided attention means directing attention towards more than one task at once
• Overt attention involves attention to something in direct line of sight
• Covert attention involves attention to something that is not in your direct line of sight
• Attention and gaze: what you see may be different than what is paid attention to
  • We can direct attention like a spotlight and what is in the spotlight is easier to process

Posner's Cueing Paradigm

• Posner's Cueing Paradigm is where participants fix their gaze at a point in the middle of a computer screen.
• The target would appear on either the left or right of the center & A cue is given to indicate direction; valid cues correctly indicate direction while invalid cues indicate the opposite direction and with no cue, no cue was given
• Valid cues took the least time, invalid cues took the most time and no cue fell in the middle
• Stimulus onset asynchrony is the amount of time between prompt and signal
• Inattentional Blindness entails that if our attention is focused on something else in the scene, we miss something that is visible
• Change blindness is when one fails to notice a change in the environment

The Auditory Sense

• Sound is a periodic variation in air pressure caused by sound waves emanating from a source
• Pure tones follow a sine wave
• Frequency is the number of cycles per second and is correlated to the pitch (measured in Hertz)
• Amplitude is the distance between the peak and trough of a sound wave, correlated to loudness & Measured in decibels
• Waveforms are complex sounds that are a mix of multiple frequencies
• Fundamental frequency is the lowest of all other frequencies in a complex sound and determines the pitch of the sound
• Harmonics are higher frequencies present in a complex sound
• Timbre consists of the sound differences between sounds at the same pitch but with different harmonics (the "voice" of the sound)
• Phase is the position in one cycle of a wave
• "Out of phase" corresponds to a time delay and sounds out of phase by 1½ a cycle can cancel out sound
• Amplitude and frequency interact, therefore some frequencies need more and some need less
• human voice (100-300Hz) needs slightly less

Anatomy of hearing

• The pinna funnels sound into the ear canal and is unique to each individual
• The tympanic membrane vibrates with sound, causing Ossicles to move
• Just inside the tympanic membrane is the Eustachian Tube, which opens to the larynx to relieve pressure on the ears
• Bones amplify the sound wave into the Cochlea through the Oval Window:
  • Pressure makes the fluid inside the cochlea move in a wave, which makes the Basilar Membrane bend and flex with the wave
  • Creating tension on the hair cells of the basilar membrane which causes them to fire
• Most sounds are complex (meaning that they have a fundamental frequency with multiple harmonics above that frequency), which will cause multiple firing points on the basilar membrane

Hearing Loss

• High-frequency hearing loss occurs as humans age
• 50-yo can't hear above 12,000 Hz, 25-yo can't hear about 16,000 Hz
• Basilar membrane gets stiff as we age, making it harder to encode high frequencies
• Decibel levels do the damage
• at 30 dB - quiet bedroom is barely audible, 70 dB is a busy city street (hazardous), 100 dB is tools/chainsaw (dangerous) while ~140 dB is plane taking off
• Permanent hearing loss depends on strength and length of exposure as well as outside range
• Conductive Hearing Loss means that the sound isn't getting to the cochlea properly, which is due to blockage, damage or otosclerosis
• Sensorineural Hearing Loss entails that the sound is not being processed by the neuronal system properly, usually to genetics or damage to cochlea/hair cells/cortex
• One symptom includes Tinnitus (ringing in ears)
• Cochlear implants have been designed which are digital device to restore some hearing to deaf individuals. (usually human voice
• These artificial mechanisms Stimulate auditory nerve artificially, bypassing the hair cells

Theories of Hearing

• Place code theory frequency is encoded is at specific places along the basilar:
  • Hair cells at specific places fire, encoding frequency
  • Basilar membrane gets thinner at the apex compared to the base and responds to different wavelengths along the length of it
• Temporal Code Theory frequency is matched with firing rates of basilar membrane:
  • Basilar membrane at the apex (low frequencies) vibrates at the same rate as the sound wave
• Each code works for a different frequency, where the temporal code theory is for low frequencies and the place code theory is for high frequencies
• Basilar membrane is thick at the base which is good for high frequencies
• Basilar membrane is thin at the apex which is good for encoding low frequencies

Auditory Pathway

• From the cochlea, the neural signal goes through the Auditory Nerve
• The signal travels through the Inferior Colliculus (top of Brain Stem) and Medial Geniculate Nucleus (Thalamus)
• Ends up in the Primary Auditory Cortex (A1) Located under the Lateral Sulcus on the top of the Temporal Lobe and is Part of the Auditory Core

More on Hearing

• Tonotopic organization means that cells that respond to specific frequencies are located next to each other in a map-like pattern.
• A1 is surrounded by the Belt and Parabelt, which respond to more complex sounds, not just pure tones & auditory core region includes "What" (Temporal Lobe) and "Where" (Parietal Lobe) pathways
• Hearing develops at 25 weeks of gestation, newborns an recognize their mother's voice, infants have thresholds for hearing as young adults and babies can differentiate between different sources of sound
• Hair cells continue to develop for the first years of a child's life
• Biosonar is a tool harnessed by bats and dolphins, the process is called echolocation
• This pertains to Using sounds to “see” by emitting high-pitched sounds and returning them
• High frequencies are good because they don't pass through smaller objects
• Uses Doppler effect where sound waves compress when moving towards, expand when leaving direction
• Calls go out while an animal is moving, and timing until the return eco gives information about distance
• The pitch increases if approaching the object

Auditory Scene Analysis

• Temporal segregation means sounds that occur simultaneously are linked
• Spatial segregation means sounds that come from the same direction are linked
• Spectral segregation means sounds with overlapping frequencies and harmonics are linked togehter
• Harmonic coherence means when multiple sounds resemble the harmonics and fundamental frequency, like when in an orchestra

Sound Localization

• Azimuth - the direction of sound in the same horizontal plane as the listener (360 degrees)
• Elevation - the direction of sound in the vertical plane in relation to the listener, up-down direction
• Distance - The perceived physical distance the sound source is from the listener
• Interaural time difference arises because we have two ears on opposite sides of our heads, the sound reaches each ear at different times, and that difference informs where sound is coming from
• Interaural loudness difference dissipates with distance
• Acoustic shadow means loudness is dampened by the head as sound travels around/through
• This Creates different loudness in each ear, which they detect and use to judge direction distance
• The cone of confusion is a region in space where sounds are equally likely because of internal time and loudness differences
• Elevation Perception uses spectral shape cue to locate sound
• Memory & Loudness + Direct vs indirect provide more cues for proper assessment and can be damaged through new piercings
• Reverberation time can provide more info and entails the difference in time from the onset of direct sound and the onset of indirect sound

Speech Perception

• Anatomy – Trachea, Larynx, Pharynx, Uvula, Teeth, Tongue, Lips
• Vowels use unrestricted airflow and form the frequencies within harmonics of vowel sounds with higher amplitudes
• Consonants restricted airflow meaning they are shaped with parts of mouth, and they go though Manner of articulation and are voiced/unvoiced
• Phonemes are the basic units of speech sound
• International Phonetic Alphabet (American English) has 15 vowel sounds, 24 consonants but is complex at times Coarticulation the pairing of phonemes in a word changes the phonemes sound Example: “ba” and “be” both have “b” but is pronounced differently because of the vowel after Categorical Perception when small variations in phonemes are perceived as the same Voicing-onset time is the time difference between the first sound and the vibration of the vocal cords

Speech

• Top-Down Processing in speech is based on what we have learned
• Pertains to Pronunciation, Words, Grammar, Syntax
• by noise & Different in foreign languages
• Word segmentation is the recognition of boundaries between words
• Phonemic Restoration Effect is "filling in" gaps in speech that are left there

Speech Areas of the Brain

• Broca's Area responsible for speech production
• Wernicke's Area responsible for speech/language comprehension
• Voice Area (Superior temporal sulcus) responds to human voices
• Aphasia disability due to damage to the brain area responsible for speech/language comprehension
  • Broca's aphasia and Wernicke's aphasia
  • Sign-language and Wernicke's aphasia

Theories of Speech Perception

• General-mechanism theories claim that it speech perception uses no different mechanisms than regular auditory perception
  • There is importance of Top-down processes
  • Learning a language is important to development of phoneme production and comprehension, also good to classify features of speech
  • But there is more information in speech than just a signal & We can be fooled by non-speech sounds
• Special-mechanism theories entails that there are special mechanisms for speech perception and Motor theory entails it's unique from auditory perception. The end goal is to deduce the mouth and airway movements of the speaker
• The McGurk Effect, inconsistencies in phoneme formation
• Direct Perception approach (by Fowler & Thompson) is often used to correlate the sounds we hear to the motion of the speaker's vocal tract, and this can be confusing instead of concentrating on just sound

Speech Development

• Infants and children have an ability to learn languages meaning they can learn any languages/phonemes or patterns etc
• infants and children have All the phenomes spoken in the environment, can use, they use that over others during production

Music

• Timbre is the "voice" of sound caused by different, higher harmonics, and it's cause may differ instrument to instrument
• Instruments may play the same fundamental tone, but they sound very different because of the higher harmonics (timbre)
• Instruments have different range

Parts of Music

• Octave is the interval between a note of a particular frequency and half or double of that
• Chroma is a subjective quality of a pitch, it makes octaves sound similar (and people sound off-key)
• Semitones - (diatonic) 12 steps within the octave (equal-temperament scale) that each has a distinct tone
• Harmony is dissonant given that there are non-complementary chroma (higher harmonics) and consonnance involves complementary chrom
• Dynamics, rhythm, tempo, meter, beat, and timbre all fit into this category
• Melody entails a collection of notes in a particular rhythm and sequence of pitches that is percived as oine unit. This must be tied to a particular scale of key & octaves are universal

Gestalt principles of melody

• Proximity: pitch of notes that are closer together in frequency
  • time & space
• Similarity
• Closure often helps people hear a resolution to the musical phrase, for example if we start on c then we should end on c (or g)
• Good continuation helps for notes that are separated that are more related because they occur in the same scale of frequency

Neuroscience of Music

• Music perception is primarily in the right temporal lobe.
  • right secondary auditory cortex
  • speech is in the left
• Musical training activates the left hemisphere along with the right
• Congenial amusia means an inability to perceive music normally
• Color-music synesthesia means you're seeing color when you hear music