Perceptual Development

Food 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 signals

Olfactory 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 memory

Olfactory 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?

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 later

Taste 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 seem to prefer flavors that are adaptive for them 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 development

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 education

Tactile 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 myelinated

Types 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 humunculus

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 infants