Visual Processing Flashcards
DOES BEHAVIOUR REQUIRE A BRAIN?
- not per se; ie:
1. echinoderms (sea starfish; brittle stars; sea cucumbers; etc.)
2. cnidarians (sea anemones; corals; jelly fish)
3. chorates (lancelot)
BRAIN FUNCTIONS
- organ
- has neurons/glia/blood vessels
- blood-brain barrier
- systems regulating beh performance
- generates beh
- controls physiological/mental/physical body processes
- generates beh
- controls motor sequences
- influences homeostasis/stress responses
- regulates sleep/internal states
- stores memories
TRIUNE BRAIN MODEL
- beh/forebrain evolution
- compartmentalised brain functions said to function independently
- NOT supported by neuroscience/evolution/psych evidence
- aka. 3 brains, not 1
NEOCORTEX - human “rational” brain
LIMBIC SYSTEM - mammalian “emotional brain”
- amygdala/hippocampus/cingulate gyrus
REPTILIAN BRAIN - instinctual “survival” brain
- basal ganglia/brainstem
BRAIN = NETWORK
- brain = highly structured/interconnected network of neurons/supporting tissues
- collection functioning as single unit
- communication balances speed/cost
- specialised cell/hub clusters
- dynamic/serial/parallel activity
- remembers/generates new connections
- makes predictions about internal/external environment
SENSORY PROCESSING
- sensory info processing varies w/body type/brain design/action spectrum
- eyes = diversity/similarities
- spatial resolution/sensitivity of eyes
DUSENBERY (1992)
SCALLOP
- eyes: 60/200; receptors: 10k
ANT LION
- eyes: 12; receptors: 50
FLY
- eyes: 2+; receptors: 80k
SPIDER
- eyes: 8; receptors: 10-10k
HUMAN
- eyes: 2; receptors: 130m
DAPHNIA
- eyes: 1; receptors: 176
NEMATODES
- eyes: 2; receptors: 1
WITH SPATIAL RESOLUTION
ARTHROPODA (insects; crabs; etc.)
- insecta
- crustacea
- chelicerata
MOLLUSCA (snails; mussles; squid; etc.)
- cephalopoda
CHORDATA (vertebrates; etc.)
- vertebrata
WITHOUT SPATIAL RESOLUTION
ECDYSOZOA
- onychophora
- nematoda
MOLLUSCA (snails; mussles; squid; etc.)
- gastropoda
- bivalvia
LOPHOTROCHOZOA
- platyzoa
ANNELIDA
- polychaeta
DEUTEROSTOMIA
- echinodermata
ANCESTRAL METAZOAN
- cnidaria (corals; anemones; etc.)
HIGH-RESOLUTION VISION
- high-resolution vision evolved to process more spatial info for increasing task complexity (aka. task difficulty = reception)
- screening pigment = non-directional photoreception
- membrane stacking = directional photoreception
- focusing optics = low resolution vision
HOW DO WE SEE SMALL DETAILS IN AN IMAGE?
- reduce distance to object/feature aka. move closer/bring image closer; less scene seen BUT more details appear
- accomodation of lens (humans/mammals)
- move lens/retina inside eye (fish/jumping spiders)
2 EYE DESIGNS W/SPATIAL RESOLUTION
COMPOUND
- invertebrates
- individual lenses
- convex retina
- grouped receptors (rhabdom)
SINGLE-LENS EYE
- invertebrates/vertebrates
- single lens
- concave retina
- individual receptors
HEMPEL DE IBARRA ET AL. (2015)
- flowers seen via honeybees’ eyes
- to resolve more details in flower patterns, bees must come close to flower
RECEPTORS
1. S: sensitivity peak in UV spectrum
2. M: blue peak
3. L: green peak
KIRSCHFELD (1976)
- neural principles in vision
- compound eyes found only in small-sized animals in invertebrate line
- single lens eye = resolution scales linearly w/size
- compound eye = eye radius proportional to square of required resolution
LYTHGOE (1979)
- ecology of vision
- larger eyes = higher spatial resolution; ie:
1. human
2. peregrine falcon
8. myotis (bat)
13. honeybee
17. metaphidippus (jumping spider)
18. drosophilia - aka. lower body height = higher anatomical/physiological resoltion; negative correlation
LAMB (2013)
- phototransduction/vertebrate photoreceptors/retina evolution
- protostomes = molluscs/annelida/arthropods
- 420 MYA = jawed vertebrates (gnathostomes) evolved aka. ancestors to modern vertebrates
- hag fish (slime eels) & lamprey = jawless vertebrates; living species in evolutionary distinct lines; shared common ancestor w/gnathostomes
LAMPREY (GEOTRIA AUSTRALIS)
- 38 species (some fish parasites)
- aka. nine-eyed eel; lateral eyes
- lamprey eyes = similar to other vertebrates; supports hypothesis derived from fossils aka. that vertebrate lens eye evolved early in vertebrates evolution
- ammocoete’s rudimentary eyes = embedded beneath skin; cannot be seen
PESSIMISTIC ESTIMATE OF TIME FOR EYE TO EVOLVE
- theoretical considerations of eye design allow finding routes along which optical structures of eye may have evolved
- if selection constantly favours ^ in detectable spatial info amount, light-sensitive path will gradually turn into focused eye lens via continuous small design improvements
- upper limit for number of generations required for complete transformation = calculated w/minimum of assumptions; even w/consistently pessimistic approach, required time = amazingly short aka. only a few hundred years to evolve eye w/high spatial resolution
MAIN DETERMINANTS OF VISUAL PERFORMANCE IN IMAGE-FORMING EYES
SPATIAL RESOLUTION
LIGHT SENSITIVITY
TEMPORAL RESOLUTION
DETERMINANT: SPATIAL RESOLUTION
- viewing distances
- size/density of relevant features/objects in visual scene
- density/number of photoreceptors
- eye size/retina curvature
DETERMINANT: LIGHT SENSITIVITY
- intensity range in which receptors operate (dim/bright light)
- eye size
- size of lens(es)
- decreases w/higher spatial resolution
DETERMINANT: TEMPORAL RESOLUTION
- speed of movements
- fast/slow photoreceptors
CONTRASTS = IMPORTANT
- important for generating info
- coding info = costly
- most useful info = in patterns of contrasts
- function of vision = extraction of info NOT to form copy of external world
RODIECK (1965); ENROTH-CUGELL & ROBSON (1966): MEXICAN HAT MODEL
- responses of cells w/centre-surround receptive fields (aka. classical RFs) in vertebrate retina can be described by Difference of Gaussians model (aka. summation of excitatory/inhibitory inputs)
- Mexican Hat Model = responses of centre/surround/sum for ON-centre/OFF-surround receptive field when spot is moved across receptive field
ZANKER (2009)
- sensation, perception & action
- filtering to separate dif features
- gravel pit = sieved filter out gravel of dif sizes
- eye retina = filtering by spatial frequency/colour (ie. centre-surround receptive fields)
DECOMPOSITION OF IMAGES IN DIF SPATIAL FREQUENCY CHANNELS
- high-frequency square wave (10 cycles)
- low-frequency square wave (5 cycles)
- high frequencies filtered out = blurry image; low frequencies filtered out = negative image
SUMMARY
- animal eyes = diverse BUT share similar basic functions for info processing
- eye size/mobility define how much/which info is extracted
- photoreceptors = first filter in visual pathway
- futther filtering in post-receptor stages takes place in each serial layer of visual system already in brain periphery
- in both vertebrates & insect eyes, edge extraction starts at first synapse of vertical/serial connections
