From Sensory Plasticity to Behaviour Flashcards
LYTHGOE (1979)
- larger eyes (compared to body ratio) = higher spatial resolution
- ie. lowest -> highest = human -> peregrine falcon -> honeybee -> drosophilia
- visual exceptions = myotis (bat) -> jumping spider (aka. much better vision than bat)
DEVELOPMENT OF VISUAL SYSTEM IN MAMMALS POST BIRTH
DIFS IN VISUAL ABILITIES OF ADULTS/INFANTS
- 1st year = acuity develops v fast BUT continues also during later development (up to 20+ y) as eye (+lense) continues growing in size
- 1st month = eye-hand coordination already starts developing
- week 8 = babies focus view more easily
- 3 months = reaching for objects
- 8 months = crawling; develops eye-foot-hand coordination
- 10 months = increased visual generalisation for small features in non-relevant objects/improved human face discrimination (relevant objects)
GIBSON & WALK (1960)
- “visual cliff” experiment
- same sized pattern viewed from dif distances generates disparities that visual system (at V1 lvl) interprets as same texture/object at dif distance
- young babies won’t crawl over glass as depth perception = already developed by 5 months; other infant mammals also don’t walk over; BUT dark-reared kittens fail
ISSA ET AL. (1999)
- critical-period plasticity in visual cortex
- visual deprivation causes structural changes in brain
- experiments in kittens/monkeys revealed development/utilisation of V1 structures (orientation/ocular dominance columns) depend heavily on sensory experience
- brain functions compete for space; reorganisation takes place
- 1st evidence at neural lvl for critical sensory periods in early age post which development CANNOT be recovered (or only partially)
COUREAUD ET AL. (2002)
- transnatal olfactory continuity in rabbit; beh evidence/STM consequence of disruption
- pre-natal brain development/learning/transnatal sensory memories
- mammalian newborns fully depended on milk; rabbit mothers lactate pups until day 28 post birth then pups find food independently; detecting/competing w/siblings for access to milk
OLFACTORY SYSTEM OF HONNEYBEE
antenna (60k receptors) -> lateral proto-cerebrum -> mushroom body
KROFCZIK ET AL. (2008)
- synaptic density/neuropile volumes change in insect brains during adult beh development BUT also depend on sensory experience
- honeybee queens experiencing higher temp during pupal development show larger neuropile volumes w/age post adult emergence (increase in microglomeruli number); workers reared in field colonies/greenhouse show difs in calycal bouton volumes/densities at dif ages/in dif rearing environments
IMMUNOHISTOCHEMISTRY
- synapsins = phosphoproteins located in boutons of presynaptic neurons in mushroom body calyx
- synapsin genes = expressed in many animal brain neurons
- labelling synapsins w/antibody/Kenyon cells w/fluorescent dye (phalloidine) = gives 2-coloured images identifying MGs
MINI SUMMARY
VISION & HEARING
- parallel pathways
- sensory maps
- similarities between senses
SENSORY LEARNING & MEMORY FORMATION
- synaptic plasticity in identified neurons/circuits
SPATIAL LEARNING
- egocentric/allocentric frameworks to locate sensory cues & guide actions in space
KNUDSEN (2002)
- auditory cue values/locations in space
- sound waveform in right ear = delayed/attenuated relative to left ear
- correspondence of interaural timing dif (ITD) & interaural lvl dif (ILD) values w/locations in space for 6kHz sound; spatial pattern changes for other frequencies
LOCATION OF SOUND SOURCES
- mapped into 2 dimensions onto MLD
- spatial reconstruction of auditory spaces in front of owl
- L/R = azimuth of agrees; +/- = elevation degrees; from ITD/ILD coding pathways converging in MLD
- in addition in inner part of auditory region neurons = organised in tonotopical layers (mapping interneurons according to frequency tuning); outer part = interneurons tuned to 6/8kHz (highest sensitivity range)
DE BELLO, FELDMAN & KNUDSEN (2001)
- vision supplements hearing in owls for prey detection
- auditory map in external nucleus of midbrain = aligned w/retinoptic visual input & controls head movements (via hindbrain)
- during development experimental manipulations targeted auditory input (ear plug)/visual input (prism)
- sound-guided gaze movements displaced when removed (BUT not visual gaze)
- effect strong in owls <3 weeks (critical period); during critical period owls can learn better/correct larger misalignments than later
- ITD tuning of neurons = indicated by numbers in ICC/OT
CATANIA & KAAS (1996)
- sensory maps exist in both vertebrate/invertebrate brains
- 3 somatosensory maps in cortex of star-nosed mole w/subdivided areas of dif tips of star-shaped nose (touch organ)
- nose w/22 fleshy rays/large numbers of Eimer’s organs; ray nr11 on each nose side = short/more sensitive/has largest projection area in somatosensory map
MERZENICH ET AL. (1984)
- somatosensory cortical map change following digit amputation in adult monkeys; sensory mapping can change w/perceptual experience/learning
- cortical representations can change w/use; owl monkey trained for several months at task using fingers 2-4
- reorganisation of somatosensory cortex maps following:
1. digit amputations in racoon/monkey
2. peripheral nerve stimulation in cats
3. passive touching of fingertips in humans (fMRI/primary & second somatosensory cortex)
ELBERT ET AL. (1995)
- magnetic source imaging revealed that cortical representation of digits of left hand of string players = larger > controls
- effect = smallest for left thumb; no such difs observed for representations of right hand; cortical reorganisation in represntation of fingering digits = correlated w/age at which person had begun to play
- results suggest representations of dif parts of body in primary somatosensory cortex of humans depends on use/changes to conform current needs/experiences of individual
