Lecture 4 - Sensation, perception and conciousness

sensation vs perception

sensation = receiving, collecting and amplifying information from the environment

• light, sound, smell

Perception = interpreting/organizing this information so that we understand it and react to it

muller-lyer illusion

• three arrows, they al look like different lengths but in reality they are all the same. this is bc of visual sensory information (illusion)

speech segmentation

• when you can easily hear where one word ends and the next on begins

• someone who is not fluent in the language will hear a ocntinmous stream

what do sensory organs contain

they contain specialized receptors attached to neurons

• these neurons sends signals into the brain

structure of sensory network

• sensory organ

• sensory receptors

• sensory nerve

• thalamus

• specific cortical area

Structure of vision sensory processing

• eye (processes light)

• photoreceptors (rods/cons)

• optic nerve

• thalamus

• occipital cortex

vision

• light will get absorbed

• we are not sensitive to every light form

• light has frequency associated w colour

  • short wavelength = blue (S cones)

  • long wavelength = red

• light wil hit retina

Rods and Cones

Rods

• found in periphery of retina

• works best in dim light or darkness

• not sensitive to colour

Cones

• concentrated in fovea (center of retnia)

• best in bright light

• colour vision

• different types of cones are sensitive to different colours

trichromatic colour theory (young-helmholtz theory)

• every colour is a combination of three independednt colour signals (activity of three cones)

  • example: yellow is percieved when red and green cones are being stimulated (we dont have a cone thats sensitive to yellow)

opponent process colour theory

• explains that that color perception is controlled by the activity of two opponent systems

  • yellowish-blue and reddish-green because they are antagonistic (there is no yellowish or reddishgreen colour)

  • after image

after images

• happens when you stare at an image for a while and then look away, you will see it in its opposite colour

  • when you stare too long, those photoreceptors get tired and its opposite cones come up and respon more strongly creating a revered after image

Hearing pathway

• eardrum

• ossicles

• cochlea

• hair cells

• vestibulocochlear nerve (vestibular also involved w balance)

• thalamus

• auditory/temporal cortex

why is the sense of touch important

• for social development

• communicates warmth, caring and support

• affected in autism

sensory receptors in skin

different receptors adapt at different rates to stimulation

• fine touch = fast

• pan = slow

prooprioception

• being able to understand where your body is even if you cant see it (your body knows where it is in space)

• achived through input form specialized neruons in skin, joints, bones, ears, tendons

• neurons communicate compression and contraction of muscles

pain

• private expierence associated w injury

• adapted response, allows us to identifyu danger and withdraw from it

The 5 Tastes

Sweet

sour

salty

umami (ex. glutamic acid)

bitter (ex. quinine)

• we usually avoid bitter foods bc mos bitter things are poisonous

Taste pathwya

• taste cells

• bipolar neruons

• cranial nerves (7,9,10)

• brainstem structures

• thalamus

• primary gustatory cortex (insula)

The hypothesis on tatse

taste map theory - not supported

supertaster bud theory - depated

olfaction (smell)

• important for survival

  • threat warning (fire)

  • social role (recognizing friends, attractive partners)

• different system

• smell-evoked memories

• poorly studied and understood compared to other senses

olfactory pathway

begins with olfactory receptors in the olfactory bulb responding to odorant molecues in air

• bipolar receptor

• glomerulus

• olfactory nerve

• primary olfactory cortex (pyriform)

• orbitofrontal cortex (OFC)

taste expierence

• taste is multisensory

  • involves taste, smell, touch, and even sigh/sound

speechreading and the McGurk effect

• what you see can change what you hear

  • ex. you hear ba, lips move in ga so you percive da

    • shoes that our vison can override sound

synesthesia

• mixing senses

  • ex. some people see colours when hearing sounds (math is red..)

  • this is involuntary

sensory mismatch

• what your body expects doesnt match what it expierences

  • ex. spinning chair, your body says your moving but your eyes says your still

detection threshold

• minimum intensity needed to detect a stimulus

  • your senses need the stimulus to reach a cetain strenght to notice it

absolute threshold

• the lowest intensiyt you cna detect a stimulus more than 50% of the time

• ex. the shoftest sound you can just barely hear

subliminal signals

• stimuli that do not reach conscious awareness

  • can be too weak, unclear, presented too quickly to be consciously noticed

awareness vs response

• responses may come before awareness (ex. being scared and flitching but you don’t know whats scaring you)

  • you dont need to be fully aware in order to have a response

• responses may be possible w/o awareness

  • people suffering from anomia (they know how to use something but dont know what it is)

stimulus detection

• Our sensory reports are not always accurate.

• We may report stimuli when none are present (false positives, e.g., hearing a noise that isn’t there).

• We may miss stimuli that are present (misses, e.g., failing to smell something that’s there).

• Inaccuracies may be due to sensory problems or situational biases.

  • Example: influenced by risk and reward (more likely to detect/report when there’s a high reward or consequence).

stimulus detection terminology

• hit (present and yes you detect it)

  • the beep happens and you hear it

• miss (present and no you dont detect it)

  • the beep happens but you dont hear it

• false alarm (nothing present but yes you detect something)

  • no beep happens but you think you heard it

• correct rejection (nothing present and no you dont detect it)

  • no beep happens and nothing happened

Just Noticeable Difference (JND) (difference threshold)

• smallest detectable difference b/w two stimuli that a person can reliably notice

• EX. you can tell the difference between 1 kg and 5 kg. (but you cant for 1kg and 3kg)

Weber-Fechner Law

• this law explains our ability to detect changes in the property of a stimulus

• As intensity increases, the change needed to notice a difference also increases.

• slope, K, is constant

  • In A: 50 kg → 55 kg = ΔI = 5 kg

    Relative change = 5 ÷ 50 = 0.1 (10%)

    In B: 1 kg → 6 kg = ΔI = 5 kg

    Relative change = 5 ÷ 1 = 5 (500%)

    • B is easier

consciousness

• our subjective awareness of ourselves and environment

  • autonomic (unconscious) behaviour

  • controlled (conscious) behaviour

  • implicit (unconscious) memory

  • explicit (conscious) memory

• fundemental to our sense of identy, free will and morality

• most processing is thought to be unconscious

sleep and why do we need it

• state of consciousness

• maintenance of brain (clears waste) and restores injured/damaged tissues

• ontogenetic development of the brain

• maintencance of language and memory

• emotional regualtion

• energeticially favorable

• dreaming

sleep in elderly

• it takes longer to sleep the older you get (greater sleep latency)

• more arousals

• less REM sleep

• Less NREM3 (deep sleep)

• fragmented sleep (interuptions)

• less overall sleep

young adult sleep

• more deep sleep

• more rem sleep

• fewer arousals (awakenigns)

• consolidated sleep

sleepers in population (average)

• 7-8 hours

• difference in individuals

• exercise, stress and genetics all matter for sleep

chronotype

• referes to weather somone is a morning ot night person

early bird vs night owl

• morning

  • better academic performance

  • better mental health

  • higher aggreableness and conscientousness

• Evening

  • higher cognitive ability

  • higher neuroticism and sensation seeking

dreams

• aversive, rarely happy or sexual

• increases in complexity w age (neurocognitive theory)

REM dreams

• more emotional

• logicial

• sudden plot shifts

NREM

• more thought like, repetitive nd centered around daily tasks

why do we dream

dream protection theory

• instincts are transformed into symbols that represent wish fulfillment

evolutionary theory

• dreams about threats to reproductive success, plan solutions

activation-synthesis theory

• dreams are an attempt by the brian to interpret random acitivty

overfitted brain hypothesis

hypnosis

• trance like state

• 20% highly responsive, 10 % unresponsive

• best candites: peopel who are open to new expierences, attention foucsm show conformity obiedience and suggestibility

• selection bias

theories of hypnosis

dissociative theories (unreliable)

• suggests hypnosis cna split consciousness

• person acts 4 years old when they are 20

socio-cognitive theories (better supported)

• a social role or performance based on expectations

cour rejects hypnoses based evidence

used in therapies

effective for anxiety and pain

Near Death Experiences (NDEs)

• Experience associated with death or impending death

• May be studied using the Greyson NDE scale

• Aspects of NDEs can be brought about with drugs (ketamine, DMT, opioids), brain stimulation or hypoxia

Common features of NDEs

Peaceful

Out-of-body experience

Altered time perception (feels like you've been there for years)

“My life flashed before my eyes” → isnt exactly lol

Meditation

An activity in which an individual either trains the mind and/or induces an altered state of consciousness

Widely practiced and has shaped culture, religion and medicine

may help treat anxiety depression and chronic pain disorders

deja vu

• soemthoing that you think has already happend before

• May be due to temporal lobe anomalies (false familiarity) or prior similar experiences incompletely recalled