Perceptual Development

1. Perceptual Development

2. Food for thought • How do perceptual systems develop? • How do different senses interact in development?

3. 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

4. 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

6. 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?

7. 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?

8. 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

9. 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?

11. 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

12. 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

13. 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

14. 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

17. Types of touch • Different types of touch are associated with different types of receptors • Pain • Temperature

18. 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

19. Most aspects of these functions are fairly mature at birth.

20. 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?

21. 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