1Perceptual DevelopmentFood for thought How do perceptual systems develop? How do different senses interact in development?General concepts Sensory receptors/Sense organs General pattern of transmissionSense organs Thalamus Cortical areas Organizational principleTopographical mapping Receptors translate stimuli into electrical signalsOlfactory System development Smell is one of the earliest emerging perceptual systems The olfactory bulb acts as the major brain sensation organ for small Ventral temporal lobe acts as primary cortical area Olfactory areas have many connections with brain areas involved in memoryOlfactory system New olfactory cells (in nostrils & olfactory bulbs) are generated throughout lifetime Precursor cells are required for this generation Relatively little plasticity – human olfactory system is largely developed by birth Babies can smell in utero Survival mechanism?2 Babies can identify smells (especially their mothers) very soon after birth. Babies discriminate mother’s milk smell from other women very early Early developed sense of smell might relate to social and cognitive development How? In both “old” senses (taste and smell), input goes first to very primitive structures, then to cortical areas. The more primitive aspects of this system may underlie differentiation early in development, with cortical control kicking in laterTaste System Also an early maturing system Taste buds are receptor cells Input to medulla, and from there to thalamus and limbic system Why might it be important for the taste system to interact with the limbic system? Babies discriminate and respond differently to different tastes from early on Babies seem to prefer flavors that are adaptive for them  e.g., sweet is the “most popular” flavor for newborns, corresponds to milk. Infants seem to be programmed to crave what’s good for them Example – Infant with imbalance in adrenal hormones that regulate salt had craving for salty foods Role in dietary preference? Perhaps, but there is very little data from humans Preferences can also be learned Conditioned responses and associative learning Developments in taste perception Some tastes are delayed Salt preference increases with age Wanes after about age 2 May relate to organ development3 Breast milk vs. formula Breast – fed babies have been shown in some cases to out-perform bottle fed babies Why? Nutrition in breast milk Difference in social relationship Unlikely – babies fed breast milk through tubes (so no difference in interaction) still outperformed babies fed formula Maternal educationTactile System Involves synapses from sense organs to spinal chord, ultimately ending up in somatosensory cortex Some sense of touch develops in utero Touch involves very long axons –sensation continues to improve until they are myelinatedTypes of touch Different types of touch are associated with different types of receptors Pain Temperature Pressure Different type of receptors respond to different types of touch Differences in how quickly they adapt or habituate Complex stimuli activate a number of receptors and a number of types of receptors Spacing of receptors influences how sensitive a particular part of the body is This sensitivity information is translated on the humunculus4 Most aspects of these functions are fairly mature at birth. Whisker barrels in rodents Whiskers are represented in “barrels” Patch-like organization Removal of whiskers increases area represented by each whisker Significance for development/humans?Newborn touch therapy Eliot suggests that touch and massage can help with later development What might be a problem with this interpretation? These data are much more well established for premature infants than for full term