MCAT Sensation, Perception, and Consciousness Flashcards
Transduction
When an environmental signal is turned into an electrical signal that’s sent to the brain.
Sensory Adaptation
When the strength in the response to a stimulus decreases with prolonged exposure to the stimulus.
Difference threshold (just noticeable difference)
The minimum threshold to differentiate two between two stimuli 50% of the time.
Weber’s law
As the intensity of the stimulus increases so does the just noticeable difference.
Given by the following equation:
(Difference threshold)/ (original stimulus strength) = K
We can find the difference threshold of one stimulus by using the equation and calculating the constant, K.
Absolute threshold
The threshold needed to detect a stimulus 50% of the time.
Signal detection theory
Used to see how external stimuli effects our judgements and decision making.
- Hit = signal presented, correctly identified
- Miss = signal presented, not identified.
- False alarm = no signal present, signal identified.
- correct rejection = no signal, signal not identified.
Sensory receptors, what are the four types?
Sensory receptors take internal and external stimuli and transduce them to the CNS.
- Mechanoreceptors- respond to mechanical stimuli such as pressure, vibrations, movement.
- Thermoreceptors - receptors that respond to a change in temperature.
- Photoreceptors - responds to light.
- Chemoreceptors - responds to chemicals like taste and smell.
Role of the thalamus
Most sensory information is sent here first and then to the appropriate brain regions.
The exception is olfactory stimuli which is sent to the olfactory bulb and then directly to brain regions.
Perception
Making a meaning of neural signals.
Top- down processing
When someone uses previously encoded information in perception of stimuli.
Perceptual set
When someone focus on certain parts of a stimuli but not others.
Perceptual organization
When someone’s experiences and expectation effect their perception of a stimulus.
People can have different perceptions of a stimulus if they have difference experiences and expectations.
Perceptual constancy
When nothing changes to the stimulus when slight changes are done to it when were observing it.
- Shape constancy
- Size constancy
- Color constancy
- Brightness constancy
Depth perception
When a person sees in 3D from the brain’s interpretation of 2D information from the eyes.
Information of depth perception given by monocular cues and binocular cues.
Describe the following monocular cues:
- Interposition
- Relative size
- Height in plane (relative height)
- Motion parallax (relative motion)
- Linear perspective
Monocular cues are cues from one eye that gives us information about depth perception.
- Interposition - When an object is partially blocked by another object the partially blocked object appears further away.
- Relative size - An object that is further away from another object appears smaller.
- Height in plane - objects lower the plane appears closer to us the objects further in the plane.
- Motion parallax - object that’s closer to us seem to be moving faster than objects further away. Think moving in a car.
- Linear perspective - parallel lines going off in the distance appears to come together.
Describe the binocular cues
Binocular cues are cues on depth given by both eyes.
- Retinal disparity - information about depth caused by the slight difference in the images that falls on both eyes.
- Convergence - The brain interprets the angles created by the eyes when they come close together to view close objects and the increase in the angle as it views objects further away.
Phi phenomenon
When adjacent flashing lights are perceived as moving.
Gestalt principles. Describe each one:
1. Law of subjective contours
- Law of similarity
- Law of continuity
- Law of closure
- Law of proximity
Used to explain how the brain examines stimuli as a whole rather than its hearts.
- Law of subjective contours- we perceive the contours (edges) of an object even when it’s not filled in.
- Law of similarity- we group together objects that are similar.
- Law of continuity - we view stimuli as a continuous path, not broken paths.
- Law of closure- we view the whole object by filling in gaps (think “ closing in those gaps”).
- Law of proximity - we see objects that are close together as groups .
What kind of waves is light?
Electromagnetic waves.
Wavelength determines it’s color (hue).
- Amplitude describes its intensity.
Describe the following parts of the eye:
- The cornea
- The pupil
- The iris
- The sclera
- The lens
- The cornea covers the pupil
- The pupil is the opening of the eye that allows light the pass.
- The iris- determines the dilates or constricts the pupil. It’s colored and determines the color of our eyes.
- The sclera- the white part of the eye.
- The lens- changes shape to change how the image falls onto the retina.
Accommodation
The process of the lens changing shape to change how the image falls onto the retina.
Describe the photoreceptors of the eye
Rods responds to movement and white, black, and grey colors.
Cones has high visual acuity and responds to the other colors.
- Centermost region of cones is the fovea which is the highest visual acuity as it’s packed with cones. The middle of the fovea is the macula.
Describe how visual information is passed among retinal cells?
Photoreceptors sends information to bipolar cells which synapses onto the ganglion cells whose axons come together and form the optic nerve. It goes to the thalamus and then to the visual cortex of the occipital lobe.
- The optic disk is where the optic nerve leaves for the thalamus and blood vessels supply blood to the retina. Because of this there’s a blind spot there.
Describe the visual pathway in the brain
Optic nerve crosses over at the chiasm so that information is processed on the opposite side of the brain from where it was transduced.
Now they’re referred to as tracts which goes to the lateral geniculate nucleus of the thalamus and then to the V1 (primary visual cortex)
Feature detectors
Neurons within the V1 only fire when exposed to different features of a stimulus such as certain orientation of lines.
Parallel processing
Processing the different information from feature detectors simultaneously.
Parvocellular pathway v. Magno cellular pathway of the V1
Parvo pathway transmits information about fine details from the LGN to V1.
Magno pathway transmits information about motion from LGN to V1.
Ventral stream v. Dorsal stream of V1
Ventral stream - projects information from V1 to the temporal lobe about what the of the stimulus (characteristics)
Dorsal stream- projects information from V1 to parietal lobe about the motion of the stimulus.
What are the two theories about how we process color?
- Trichromatic theory- cones responds to one the following three colors: red, green, blue.
- Opponent - process theory - cones sense color in opposing pairs. Inhibition of one leads to activation of the other: red- green, blue- yellow
What are the three sections of the ear?
Outer ear - contains the pinna which serves to funnel sound to the tympanic membrane (eardrum).
Middle ear - contains the tympanic membrane which vibrates the malleus, Incas, and stapes which are also in the middle ear.
Inner ear - contains the cochlea. Contains semicircular canals and otolith organs which are part of the vestibular system.
Describe the cochlea
A three- chambered structure in the inner ear. The middle chamber contains the organ of Corti which contains mechanoreceptors and supporting cells that sits on the basilar membrane.
The fluid in the middle chamber is called endolymph and when hair cells move it causes depolarization allowing the auditory nerve to send signal to brain.
The receptors are also called hair cells because on top of the mechanoreceptors are cilia.
What happens after auditory transduction?
The vestibulocochlear nerve sends signal from cochlea to medial geniculate nucleus (MGN) of the thalamus. From the thalamus it’s sent to the auditory cortex of the temporal lobe and to the inferior colliculus.
What is the pitch of sound?
Frequency theory
Place theory
How high lor low a tone is, determined by frequency.
- Frequency theory - pitch perception occurs because of the frequency of interaction at the auditory nerve.
- Place theory- pitch is influenced on where receptors are located on the basilar membrane in the organ of corti.
Somatosensation
The process of relaying sensory information from the environment to the brain. Specific receptors respond to specific stimuli.
Somatosensory neurons transduce sensory stimuli to electrical signal that’s sent to the primary somatosensory cortex (which is in the parietal lobe).
Most sensitive parts of the body take up more space in the somatosensory cortex.
Hemispheric lateralization
Each brain region is specialized for a specific function.
Each side of the brain interprets somatosensory information from the opposite side of the body.
Gate- control theory
pain is controlled by a “ neurological gate” that can be closed by another type of stimuli thereby decreasing the sensation of pain.
i.e. being distracted during a tattoo session decreases the perception of pain.
Gustation
The process by which tastants bind to taste receptors within taste buds. Taste buds are organized into papillae on the tongue.
Taste receptors responds to a certain taste but there is multiple forms of taste receptors in each taste bud.
What are the 5 primary tastes?
Sweet, bitter, umami ( savory flavor of meat), sour, salty
Chemical senses
Food and odor molecules
Describe the path that gustatory information travels to the brain?
Tastant binds to taste receptor and depolarizes it. This causes a signal to be sent to the gustatory afferent neuron which synapses onto the thalamus.
The thalamus then sends the information to the primary gustatory cortex which is located in the insular cortex of the frontal lobe.
Sensory information
When sensory information influences each other.
Olfaction
Occurs when an oderant binds to cilia of olfactory neurons. There neurons form the olfactory nerve which sends information to the olfactory bulb.
The axons of the olfactory bulb forms the olfactory tract which sends information directly to various brain regions.
What is unique about olfaction?
It bypasses the thalamus
Kinesthetic sense. How is it sensed?
The awareness of our body in space and our movement. Happens through proprioceptors.
Proprioceptors are mechanoreceptors that are located in skin, tendons, joints, and muscles and responds to mechanical stimuli.
Describe the path of proprioceptor information transmition
Proprioceptors transmit information from the environment from afferent sensory neurons which sends it the the spinal cord.
The spinal cord sends information to thalamus via tracts.
From the thalamus it’s sent to the primary somatosensory cortex in the parietal lobe.
Vestibular sense. How is it sensed?
Maintain’s body sense of balance.
Sensed from the semicircular canals and otolith organs of the inner ear.
There information is sent to the brain via the vestibulocochlear nerve.
Semicircular canals v. otolith organs
Semicircular canals transmits information related to angular acceleration due to continous movement of the endolymph in the middle ear if we suddenly stop our angular momentum.
Otolith organs transmit information about linear acceleration.
Sensory interaction
When our kinesthetic sense, vestibular sense, and sensory information all combined gives us information about proprioception and vestibular information.
