Sense and Perception Flashcards
Sensation
simple stimulation of a sense organ
perception
the organization, identification, and interpretation of a sensation in order to form a mental representation
transduction
when sense receptors convert signals from the environment into neural signals that are sent to the CNS
psychophysics
methods that systematically relate the physical characteristics of a stimulus to an observer’s perception
acuity
how well you can distinguish between two similar stimuli
sensory adaption
sensitivity to a stimuli decreases over time
Purity (light)
the degree to which a light source is emitting just one wavelength, or a mixture of wavelengths
What do bipolar cells do in the eye?
Bipolar cells collect electrical signals from the rods and cones and transmit them to the outermost layer of the retina
-From there neurons (retinal ganglion cells (RGCs)) organise them and send them to the brain
What is the optic nerve made of
The optic nerve is made of RCGs, and contains no photoreceptors (blind spot)
Which area of the brain do visual signals get sent?
Visual signals are first sent to the lateral geniculate nucleus (LGN) in the thalamus of each hemisphere.
From there, the visual signals go a location called area V1 (the part of the occipital lobe that contains the primary visual cortex)
What are the 2 visual pathways
Ventral (lower) stream
- the “what” pathway
The dorsal (upper) stream
- the “where” pathway
Binding problem
how the brain links feature together so that we can see unified objects in our visual world rather than free floating or miscombined features
How do we see the world as a seamless whole?
Sound Waves
changes in air pressure unfolding over time
Frequency (sound)
perceived as pitch
Amplitude (sound)
perceived as loudness (the perception of a sound’s intensity)
Complexity (sound)
Affects timbre
Timbre
the quality of sound that allows you to distinguish two sources with the same pitch and loudness (ex. The difference between a clarinet and oboe playing the same song in the same key)
Outer ear
Collects and funnels sound
-Pinna
-Auditory canal
-eardrum
Middle ear
Transmits and amplifies sound
Ossicles
-Hammer “malleus”
-Anvil “incus”
-Stirrup “stapes”
Pushes against the oval window
Inner ear
Transduces sound into neural impulses
-Cochlea (“snail”)
-Basilar membrane
Cochlea
Fluid filled tube that contains cells that transduce sound vibrations into neural impulses
Basilar membrane
A structure in the inner eat that moves up and down in time with vibrations relayed from the ossicles, transmitted from the oval window
Sound causes the basilar membrane to move up and down in a travelling wave
Inner hair cells (ears)
Specialized auditory receptor neurons embedded in the basilar membrane
Bends back and forth in cochlear fluid, generating rhythmic action potentials in auditory nerve axons
Where do auditory signals go?
Auditory signals are sent to the thalamus and ultimately to an area of the cerebral cortex called area A1 (the primary auditory cortex in the temporal lobe)
Where are spacial auditory features handled in the brain?
Spatial auditory features are handled by areas towards the back of the temporal lobe in regions that may overlap with the visual dorsal stream
Where are sound identification features located in the brain?
Sound identification features are handled by areas in the lower (ventral) part of the temporal lobe (may overlap with the ventral visual pathway)
How do you detect Loudness
Signalled by total amount of activity in hair cells
How do you detect pitch
Seems to depend on two factors
First, different frequencies stimulate different parts of the basilar membrane
This provides a place code
The brain uses information about the relative activity of hair cells across the whole basilar membrane to help determine the pitch you hear
Second, the hair cell hairs move in time with the incoming sound wave, so auditory nerve axons fire synchronously with the sound-wave peaks, which happen regularly at the sound’s repetition rate
-This provides a temporal code
The brain uses the timing of the action potentials in the auditory nerve to help determine the pitch you hear
How do you detect Timbre
partially depends on the relative amounts of different frequency components in a sound, (depends on the relative activity of hair cells across the whole basilar membrane)
How do you detect location of sound
Has both one ear (monaural) cues and two ear (binaural) cues
-The pinna folds alter sound, emphasising some frequency components over others based on where they came from
-The speed of sound is relatively slow, the brain can interpret small time delays to judge distance
-Higher frequencies are more intense close to the ear than further away, as your head can block the sound
Perceptual grouping
figuring out which frequency belongs together in a single source
Perceptual Segregation
figuring out which frequency components belong to different sources
Conductive hearing loss
the eardrum or ossicles are damaged to the point where theory cannot conduct sound waves effectively to the cochlea
-The cochlea is normal
Medication or surgery are often a solution
-Hearing aids can improve hearing
Sensorineural hearing loss
damage to the cochlea, the hair cells, or the auditory nerve
-Happens to almost all of us when we age
-Sensitivity decreases (sounds must be more intense to be heard)
-Acuity decreases - sounds smear together on the basilar membrane
-Makes voices harder to understand
Haptic Perception
the active exploration of the environment by touching and grasping objects with our hands
Tactile Receptive Field
A small patch of skin that relates information about pain, pressure, texture, patter, or vibration to a receptor
Thermoreceptors
nerve fibres that sense cold and warmth, respond when your skin temperature changes
A-delta fibres
axons that transmit initial sharp pain
-fast acting
C-fibres
axons that transmit the longer lasting, duller persistent pain
-slower
What are the two pain pathways
One sends signals to the somatosensory cortex, identifying where the pain is occurring and what type of pain it is
The other sends signals to the motivational and emotional centres of the brain, such as the hypothalamus and amygdala, as well as to the frontal lobe
-Makes pain unpleasant and motivates us to escape from it
Can your pain sections of the brain get activated by other’s pain?
Your pain sensing part of the brain (especially the frontal lobe) also responds when you see other people in pain
Social Pain
embarrassment or social exclusion
Referred Pain
when sensory information from internal and external areas converges on the same nerve cells in the spinal cord
Ex. heart attack
-People feel pain from their left arm rather than from inside the chest
Is the severity of an injury a reliable measure of pain intensity?
Pain intensity cannot be determined solely by the severity of the injury that inflicted it
Gate control theory
signals arriving from pain receptors in the body can be stopped by interneuron in the spinal cord via feedback from the skin of from the brain
Can your brain control your level of pain?
Under high stress conditions the brain can send signals to the periaqueductal grey (PAG) in the spinal cord to suppress pain signals
The brain can also increase the pain you feel
-This is the theory for why being sick is painful, its the bodies way of forcing you to rest
Proprioception
your sense of body position
Where do you get info about position of torso and limbs
Info about position of torso and limbs depends on stimulation of receptors in the muscles, tendons, and joints of the body
