PS262 Ch 1, appendices, 2 and 3

Three main methods of study for Perception

• physiological (hardware analysis)

• cognitive (software level of analysis)

• psychophysical (connects objective measurements to reports of subjective experience)

Neurons

• units of processing

• relationship between nerve impulses and specific perceptions

How do neurons communicate with each other?

pre-snyaptic neuron communicates with the post synaptic neuron by sending neurotransmitters

Spontaneous activity

• resting rate or base rate without stimulation, meaning the neuron fires even without action potential

refractory period

the time following an action potential when a neuron is unable to fire another action potential due to temporary inactivation of sodium channels.

Single-cell recording technique

A method used to measure the electrical activity of a single neuron, typically by inserting a microelectrode into the cell.

Magnetic Resonance Imaging (MRI)

focuses on detailed images of brain structure

Functional Magnetic Resonance Imaging (fMRI)

measures changes in blood flow, blood flow increasesin areas of the brain that are more active, providing insights into brain function.

Electro-Encephalograhpy (EEG)

• Measures electrical activity through scalp/skull

• using electrodes placed on the scalp, allowing for the assessment of brain wave patterns and activity.

Bottom-up processing

• perception begins with raw sensory input from environment

  • starts at sensory receptors such as eyes and ears, moves upwards to brain and culminates in perception and interpretation of stimuli.

    • you see a new object, an unfamiliar tool, and try to figure out its purpose by analyzing its shape and features

Top-down processing

• perception is influenced by prior knowledge, experiences and expectations

  • you see a blurry picture of dog and recognize it quickly because you except it to be a dog based off its features

Do we perceive reality directly?

No, our perception is influenced by cognitive processes, prior knowledge, and sensory input.

Psychophysics

determining the quantitive relationships between

• physical stimulus (external)

• perception (internal psychological)

Absolute threshold

smallest amount of stimulus energy necessary for the observer to detect a stimulus

Difference threshold

• or just noticeable difference

• smallest difference between two stimuli person can detect

  • minimum change needed to tell a difference between two

  • standard stim - 200 g

  • second standard stim - 200 g + 10 g

  • you can tell second is heavier, thus 10 g is the noticeable difference

Response criterion

amount of sensory information an observer requires to say yes

low criterion

says yes even if they don’t perceive much evidence for tone

• liberal responder

high criterion

less willing to say yes

• conservative responder

Catch trials

• no target

• used to assess response bias by including trials without the target stimulus.

Receiver Operating Characteristic curves

• shows sensitivity and decision bias are separate factors

  • a persons sensitivity (ability ti distinguish signals from noise) is represented by the shape of the curve

  • bias affects on the placement of the curve along the x-axis.

Good sensitivity

• curve would bend closer to top left, indicating higher ability to correctly identify targets with fewer false alarms.

poor sensitivity

• curve bends closer to bottom right, meaning more false alarms and a lower ability to correctly identify targets.

magnitude estimation

relationship between intensity of a stimulus and the perception of its intensity

Perceptual process

1. stimulus in environment, distal stimulus

2. stimulus hits receptors, proximal stimulus

3. receptor processes

4. neural processing

5. perception

6. recognition

7. action

Stimulus in environment (distal stimulus)

• object in external world, such as a tree

stimulus hits receptors (Proximal stimulus)

• light from distal stimulus reaches eye and creates a proximal stimulus on retina

Receptor proceses

• receptors in eye, rods and cones in retina, convert light energy into electrical signals

  • process called transduction

neural processing

• electrical signals generated by receptors are transmitted through networks of neurons in brain

• processes fine information and contributes to perception

perception

• brain interprets neural signals to generate perception of object, such as recognizing characteristics like colour or shape of tree

recognition

• perceived object is compared with stored knowledge in brain, allowing for recognition

action

• individual takes action on perception and recognition and walks over to tree

Method of limits

• presenting stimuli in ascending or descending order to determine at which point a person can or cannot detect a stimulus

Method of constant stimuli

• different stimulus intensities are presented one at a time, participant must rescind whether they perceive it or not on each trial

  • presented at random

Method of adjustment

• participants, rather than experimenter, adjust stimuli to a point where they can no longer detect it

Electromagnetic spectrum

The range of all types of electromagnetic radiation, including visible light, radio waves, and X-rays, categorized by wavelength.

cerebral cortex

The outer layer of the brain, responsible for complex cognitive functions, including perception, reasoning, and decision-making.

oblique effect

The phenomenon where sensitivity to contrast varies with orientation, often showing enhanced perception for vertically and horizontally oriented stimuli compared to obliquely oriented ones.

Phenomenological report

A qualitative research method that captures participants' lived experiences and perceptions regarding a specific phenomenon.

Inhibition

A process that decreases the likelihood of a neuron firing an action potential, often regulating neural activity and maintaining balance within neural circuits.

lateral inhibiton

the capacity of an excited neuron to reduce the activity of its neighbours

Low level neural circuitry

Refers to the basic neural networks and connections that process sensory information and regulate simple reflexive responses.

simultaneous contrast

A perceptual phenomenon where the color or brightness of one area is affected by the adjacent area, making it appear different than it actually is.

Convergence

more than one neuron providing input for a neuron

Neuronal connectivity and lateral inhibition

1. receptors 1-7 are sensory receptors that detect stimuli

2. neurons a,b and c, recieven inout from receptors through excitatory connections

   1. neuron b is the central neuron

3. neurons A and C send inhibitory signals to neuron B which decreases activity of the neuron B

Receptive field (RF)

• region of retina that, when stimulated, influences firing rate of a particular neuron.

  • could make neuron fire more, excitatory

  • could make neuron fire less, inhibitory

Center-surround receptive fields

A type of receptive field organization where the center response is opposite to the surround response, enhancing contrast in visual stimuli.

Specificity Coding

The theory that individual neurons respond to specific stimuli, encoding particular features of the visual environment.

• grandmother cell

Sparse coding

A neural coding strategy where only a small number of neurons are active to represent a stimulus, allowing for efficient information processing.

Population Coding

A coding method where a large group of neurons collectively represents a stimulus, allowing for a more robust and flexible encoding of information.

Cell body

contain mechanisms to keep cell alive

Dendrites

branch out from cell body to receive electrical signals

axon

filled with fluid that conducts electrical signals

Sensory receptors

neurons specialized to respond to environmental stimuli

Action potential

the electrical impulse that travels down the axon, triggering neurotransmitter release, positive charge on the inside and negative charge on the outside of the membrane, resulting in a rapid depolarization followed by repolarization.

Resting potential

the state of a neuron when it is not firing, characterized by a negative charge inside the cell compared to the outside.

depolarization

the process of reducing the membrane potential, making the inside of the neuron less negative compared to the outside.

hyperpolarization

the process of increasing the membrane potential, making the inside of the neuron more negative compared to the outside, often following an action potential.

Excitatory response

a change in membrane potential that makes a neuron more likely to fire an action potential, often due to the influx of sodium ions.

Inhibitory response

a change in membrane potential that makes a neuron less likely to fire an action potential, often due to the influx of chloride ions or the efflux of potassium ions.

Sensory Coding

process by which sensory stimuli translates environmental stimuli into neural signals that brain can interpret

• is there a salty neuron in your brain that only fires in response to salt so you perceive saltiness?

• or, multiple neurons fire in one or multiple brain areas, that result in our perception of salt ?

Phrenology

the study of the shape and size of the skull as a supposed indication of character and mental abilities.

Modularity

specific brain areas are specialized to respond to specific types of stimuli or functions

Broca’s area

Involved in speech production, frontal lobe

Wernicke’s area

Involved in speech comprehension, temporal lobe

Distributed Representation

brain represents information all across the different regions of brain, instead of just one specific area. This allows for a more complex and nuanced processing of information.

• when your brain responds to pain

  • sensory, emotional and reflexive motor all work together to help you perceive pain

Structural Connectivity

the physical connections between brain regions, including axons and synapses, that enable communication and information flow throughout the brain.

• the highways

Functional Connectivity

neural activity associated with a particular function that is flowing through the structural networj

• the shops the highways are connected to

Mind-Body Problem

The philosophical debate concerning the relationship between mental processes and physical states of the brain,

• how do physical processes, like nerve impulses, transform into perceptual experiences ?

Accommodation

Lens changes shape so that images of nearby objects are not blurry

When lens is flat

focusing on things far away

When lens is fatter

focusing on things near

What helps lens get flat and fat

ciliary muscles

Transduction

transformation of one energy to another

Fovea

the central region of the retina responsible for sharp central vision, containing a high density of Cones

Peripheral Retina

the sides of the retina that are responsible for motion detection and peripheral vision, containing both rods and cones

• helps in dark adaptation

Macular Degeneration

common in older people

• destroys cone rich fovea and a small area surrounding it

• blind region at focal point (so directly ahead)

Retina pigemntosa

• degeneration of retina

  • first attacks peripheral rod receptors and results in poor vision in peripheral fields

Cornea

Transparent covering of the front of the eye

• 80 percent of focusing power

Lens

remaining 20 percent of eyes focusing power

• changes shape to adjust eyes focusing power

Refractive errors

• common vision problems caused by the eye's inability to focus light correctly, leading to blurred vision. These include myopia, hyperopia, and astigmatism.

Presbyopia

• as people get older, their ability to accommodate decreases, due to hardening of lens and wearing of ciliary muscles

Myopia

inability to see distant objects clearly

• can be caused by refractive myopia when cornea or lens bends light too much or axial myopia when eyeball is too long

isomerization

light causes retinal to change its shape from bent to straight

opsin

large protein

retinal

light sensitive molecule

Which photo receptor is important for dark adaptation

• rods

Rod pigments regenerate

20-30 mins

Cone pigments regenerate

3-5 mins

What is neural convergence

refers to multiple rods or cones sending signals to a single ganglion cell

rods have what type of convergence?

high (120 rods sends signals to one cell)

cones have what type of convergence

low, 6 cones sends signals to one ganglion cell

sensitivity vs acuity

• Rods: high sensitivity to faint light, poor at seeing details (low acuity) 

• Cones: low sensitivity to faint light, but excellent for seeing details and colours (high acuity)