Perception Flashcards
What does the Electroencephalography (EEG) detect?
electrical activity
An active brain produces electrical
activity
* Event-related potentials (ERP)
* EEG measures activity in a large
group of neurons at a certain
times
* Provides great estimate of when the
brain is active
Good at timing (temporal resolution)
What does the Functional Magnetic Resonance Imaging (fMRI) detect?
energy
- An indirect measure as it measures blood flow and not neural activity
Active brain areas need oxygen (metabolic
energy)
* A magnet detects changes in oxygenated
blood
Provides good spatial resolution but not good temporal. Also relies on the assumption more oxygen is more activity.
What do the Brain stimulation techniques detect?
change
Transcranial Magnetic Stimulation (TMS)
* Focal magnetic field induces
electricity and affects neurons in
the targeted area as well as
connected brain circuits
(?) TMS may improve memory (?)
Good to test causality (testing direct effects
of temporary lesion or stimulation on
cognition)
* fMRI and EEG are correlational
(associate brain activity to task)
* But stimulation techniques have broad
effects on the brain, so it is hard to localize
effects
* The way it works is not entirely clear
What are Exteroceptive sensations?
- Any form of sensation that results from stimuli located outside the
body detected by sensory organs
(Five Senses)
What are the Interoceptive sensations?
- Sensations from inside our body
- Proprioception: Sense of where our limbs are in space
- Nociception: Sense of pain due to body damage
- Equilibrioception: Sense of balance
- Dancers have increased interoceptive accuracy
(Christensen et al., 2017) - Finding was dancers could estimate heart rate more accurately
than non-dancers
What is Proprioception?
Sense of where our limbs are in space
What is Nociception?
Sense of pain due to body damage
What is Equilibrioception?
Sense of balance
What is Synesthesia?
A neurological condition in which
one sense automatically triggers
the experience of another sense
* Hear colours
* Smell sounds
* See time
* Genetic component
* More common in women
* Specific pairings tend to be stable
over the lifetime of the individual
What is Grapheme-colour synesthesia:?
Colour with letter/numbers
“7 is pale blue with a pleasant, soft, nice personality”
What is Chromesthesia?
Sound can evoke an experience of colour
Why is synaesthesia important?
1) Shows the importance of Individual differences
2) Shows the communication and crossing of circuits that happen in the brain
Ex. fMRI studies show activating of V4 color processing region during
words for grapheme–colour synaesthetes
What is Early visual processing?
- Sensation
- Eyes and the optic nerve
- Light waves enter the eye
* Projected onto the retina
* The retina forms an inverted image
*Later processes turn this image around - Retina photoreceptors convert light to
electrical activity
* Rods: low light levels for night vision
* Cones: high light levels for detailed color vision - The electrical signal is sent to bipolar
cells
* Sent on to the ganglion cells - The signal exits through the optic
nerve
* To the brain for later visual processing
What is Late visual processing?
- Perception
- The visual cortex or
occipital lobe
What is Information compression in the visual system?
Millions of photoreceptors in each retina converge onto 100x fewer ganglion cells -> optic nerve -> brain
* Input from the eyes to the brain is compressed
- Hot take: You don’t ‘see’ everything that is out there in the
world
What is the distribution of photoreceptors in the brain?
- Cones are concentrated in the
fovea - Small area on the the central part of
the visual field - Thus, center of your visual field is
most detailed - Rods are mostly in the periphery
- Thus, periphery of your visual field is
less detailed and less accurate
What is Perceptual Filling-In
When we focus with our cones on something, we tend to fill in the background of things we aren’t focusing on (with rods)
Why do we have a Blindspot?
Photoreceptors are at the back
of the retina (farther from the
‘world’); Ganglion cells are at the
front
- Ganglion cells make up the
optic nerve that exits to the brain - Must past the photoreceptor
layer - At this ‘exit location’, there are
no photoreceptors - No vision!
Why dont we usually see our blindspot?
- Perceptual filling-in
- Later visual processes in the brain provide the missing
information by ‘interpolating’ visual information (e.g.,
colors) from surrounding areas - The left and right visual fields can compensate for each other’s blindspot
What does the thalamus do with vision?
(lateral geniculate nucleus,
LGN) is the way-station
(All senses but smell stop here first)
Does vision have Contralateral representation?
Yes !
(Left visual field is perceived via the
right hemisphere
* Right visual field is perceived via the
left hemisphere)
How does the Primary Visual Cortex process information?
Specialized regions that process
specific visual attributes or features
* Edges
* Angles
* Color
* Light
What do Visual Association Areas do?
interpret visual signal, assigns meaning
Explain the What (ventral) pathway?
Occipital to temporal lobes
* Shape, size, visual details
Explain the Where (dorsal) pathway
- Occipital to parietal lobes
- Location, space, movement information
What happens when Ventral damage with intact dorsal stream?
- Impaired performance on visual object recognition or matching tasks
What happens when Dorsal damage with intact ventral stream?
- Accurate performance on object recognition or matching tasks
- Impaired performance on visual guided action (picking up an
object appropriately)
What is Bottom-up processing?
the influence of information from the
external environment on perception
* Information from the sensory organs (eyes) to the visual cortex
What is Top-down processing?
the influence of knowledge
(expectations, context and goals) on perception
* Information from higher processing brain regions (prefrontal
cortex or higher visual processing areas) is sent back to the
sensory organs
What is the Constructivist Theory of Perception?
- We use what we already know
and expectations to predict how
to perceive sensory information - Relies on the influence of topdown processes to vision
- Illustrates how perception is an
“illusion”
Explain the Ponzo illusion
depth perception
What is the The letters in context effect?
The ability to read words in sentences even when the letters in the middle
of some of the words are mixed up
You can stlil raed this senetnece even thuogh lettres in the wrods are
jubmled.
- You ‘expect’ to see real words in a sentence
- This is why it is hard to edit your own work
What is the color in context effect
- The context a color appears changes how you see that color.
- Color perception depends on :
- The wavelengths of light that fall on our retina
- Our expectation (from experience) of how objects look under
contexts of illumination
Darker backgrounds (make object look brighter)
Light backgrounds (make object look darker)
