MCAT Behavioral Sciences - Sensation and Perception

Sensation

Taking the physical, electromagnetic, auditory and other information from our internal an external environment and converting this information into electrical signals in the nervous system

Perception

Processing information within the central nervous system in order to make sense of the information significant

Sensory Receptors

Neurons that respond to stimuli by triggering electrical signals that carry information to the CNS

Photoreceptor

Respond to electromagnetic waves in visible spectrum (light)

Mechanoreceptors

respond to pressure or movement

Nociceptors

Respond to painful or noxious stimuli (somatosensation

Thermoreceptors

Respond to changes in temperature (thermosensation)

Osmoreceptors

Respond to osmolarity of the blood (water homeostasis)

Olfactory Receptors

Respond to volatile compounds (smell)

Taste Receptor

Respond to dissolved compounds (taste)

Distal Stimuli

Physical objects outside the body

Proximal Stimuli

Photons, sound waves, heat, pressure or other stimuli that directly interact with sensory receptors

Psychophysics

Relationship between physical nature of stimuli and the sensation and perceptions these stimuli evoke

Ganglia

Collection of neuron cell bodies found outside the CNS

Threshold

The minimum amount of a stimulus that renders a difference in perception

Absolute Threshold

Minimum of stimulus energy that is needed to activate a sensory system

Threshold of Conscious Perception

The level of intensity that a stimulus must pass in order to be consciously percieved

Subliminal perception

Information that is recieved by the CNS but does not cross the threshold

Difference Threshold

Minimum change in magnitude required for an observe to percieve that two different stimuli are different

Discrimination testing

Participants presented with stimulus, then varied and report if recieves change

Webers Law

Difference thresholds are proportional and must be computed as percentages

Signal Detection Theory

Studies how internal and external factors influence thresholds of sensation and perception

Noise Trial

In signal detection experiemmnts the trial in which signal is presented

Catch trial

In signal detection experiment the trial where signal is not presented

Hit

Trial in which signal is presented and subject correctly percieves the signal

Miss

A trial fails to percieve the signal

False Alarm

Trial in which subject indicates percieving signal even though there was no signal present

Correct negative

Trial when subject correctly identifies no signal was presented

Sclera

Thick Structural Layer

Choroidal Vessels

Complex intermingling of blood vessels between the sclear and retina

Retina

Innermost layer of the eye, contain photoreceptor and transduce light into electrical information the brain can process

Cornea

Gathers and focuses incoming light

Anterior Chamber

Lies in front of iris

Posterior chamber

Between the iris and lens

Iris

Colored part of the eye, composed of dilator pupillae and constrictor

Dilalator pupillae

Opens pupil under sympathetic stimulation

Constrictor Pupillae

Constrict pupil under parasympathetic stimulation

Choroid

Vascular layer of connective tissue that surroudns and provides nourishment to the retina

Aqueous Humor

Bathes front of eye before draining into the canal of schlemm

Cilary body

produces aqueous humor

Lens

Lies behind iris and helps control the refraction of incoming light

Accomadation

Change shape of lens to focus on image as distance varies

Vitreous Humor

Transparent gel that supports the retina

Duplicity theory of vision

The retina contains two kinds of photoreceptors, those specified for light and dark detection and those specified for color detection

Cones

Used for color vision and to sense fine details

Rods

Permit vision in reduced light and only allow sensation of light and dark

Signal pigment in rods

Rhodospin

Macula

Central section of retina and has high concentration of cones

Fovea

Centermost region of macula and contains cones

Optic Disk

devoid of photoreceptors, gives rise to blind spot

Bipolar Cells

Highlight ingredients between adjacent rods or cones

Visual Pathways

Refer to both anatomical connections between the eyes and brain and to the flow of visual information along these connections

Visual Parrallel Processes

Brains ability to analyze information regarding color, form, motion and depth simultaneously “in parallel”

Serial Processing

Occurs when cognitive process are execution a sequential step by step manner

Form

Refers not only to the shape of an object, but also our ability to discriminate an object of mirror from background and detecting its boundaries

Spatial Resolution

These cells permit us to detect very fine detail when thoroughly examining an object

Magnocellular Cells

Well suited for detecting motion because these cells have very high temporal resolution

Depth Perceptions

Our ability to discriminate the 3D shape of our environment and judge the distance of objects within it, is largely based discrepancies between teh inputs our brain receievs from our two eyes

Binocular Neurons

Responsible for comparing the inputs to each hemisphere and detecting these differences

Feature Detectors

Detects a very particular individual feature of an object in the visual field

Vestibular Sense

Our ability to both detect rotational and linear acceleration and use this info to inform our sense of balance and spatial orrientaiton

Pinna/auricle

Cartilangeous outside part of ear, function is to channel sound waves into external auditory canal

External auditory Canal

Directs sound waves to tympanic membrane

Tympanic membrane

divides outer ear from middle ear

Ossicles

Transmit and amplify vibration from typanic membrane to inner ear

Names of ossicles

Malleus (hammer), Incus (anvil), stapes (stirrup)

Bony labyrinth

hollow region of the temporal bone containing cochlea, vestibule and semicircular canals

Perilymph

Simultaneously transmits vibrations from outside world and cushions inner ear structures

Cochlea

Spiral shaped organ that contains receptor for hearing

Organ of Corti

houses actual hearing apparatus, rests on thin flexible membrane

Vestibule

Portion of bony labrynth contains urticle and saccule

Place theory

Location of a hair cell on the basilar membrane determines the perception of pitch when hair cell is vibrated

Chemoreceptors

Receptors that detect snesory information by binding to chemical stimuli

Olfactory chemoreceptors

Receptors in the olfactory epithelium in the upper part of the nasal cavity that respond to volatile or aerosolized compounds by binding to chemical stimuli.

Pheromones

Chemicals secreted by one animal and which once bonded with chemoreceptors compel or urge an other animal to behave in a specific way

Five basic tastes

Sweet, sour, salty, bitter, umami (savory)

Taste buds

group of cells that are receptors for taste

Four modalities for somatosensation

Pressure, vibration, pain and temperature

Pacinian corpuscles

respond to deep pressure and vibration

Meissner corpuscles

Respond to light touch

Merkel Cells

Respond deep pressure and texture

Ruffini Endings

Responding to stretch

Free Nerve Endings

Respond to pain and temperature

Two Point Threshold

Minimum distance necessary between two points of stimulation on the skin such that the points will be felt as two distinct stimuli

Physiological zero

Normal constant (temp) of skin

Gate Theory of Pain

Special gating mechanism can turn pain signals on or off affecting whether or not we recieve pain

Kinesthetic Sense

Refers to ability to tell where one’s body is in space

Proprioceptors

Receptors for proprioception play critical role in hand eye coordination, balance and mobility

Bottom Up Processing

Object recognition by parallel processing and feature detection

Top Down Processing

Driven by memories and expectations that allow the brain recognize the whole object and then recognize the components based on these expectations

Perceptual Organization

Refer to ability to create a complete picture or idea by combining top-down and bottom up processing will all of the other sensory clues gathered from an object

Monocular Cue

Require one eye

Relative Size

Refers to idea that objects appear larger the closer they are

Interposition

When two objects overlap, the one iin front is closer

Linear Perspective

Convergence of parallel line at a distnace, greater the convergece, greater the distance

Motion Parallel

Perception that object closer to us seem to move faster when we change our field of vision

Binocular Cue

Involve retinal disparity

Retinal Disparity

Refer to slight difference in images, projected on the two retinas

Convergence

Brain detects angle between two eyes required to bring an object into focus.

Constancy

Refer to our ability to percieve that certain characteristics of object remain the same despite changes in the environment