Hsin-I Liao 2005/11/17

1. Neville, H. J., & Bavelier, D. (2002). Specificity and plasticity in neurocognitive development in humans. In M. H. Johnson, Y. Munakata, & R. O. Gilmore (Eds.), Brain development and cognition: A reader (pp. 251-271). Blackwell Publishers. Hsin-I Liao 2005/11/17

2. Overview • anatomy and physiology of the developing human brain • developmental specificity of visual functions in humans • developmental specificity in other neurocognitive domains • development specificity of language functions in humans

3. Anatomy and physiology of the developing human brain auditory cortex visual cortex prefrontal cortex (Huttenlocheer & Dabholkar, 1997)

4. Overview • anatomy and physiology of the developing human brain • developmental specificity of visual functions in humans • developmental specificity in other neurocognitive domains • development specificity of language functions in humans

5. Two visual subsystems • dorsal: magnocellular system • magno (M) stimuli: low spatial frequency gratings of light and dark gray bars with a low luminance contrast • ventral: parvocelluar system • parvo (P) stimuli: isoluminant blue and green high spatial frequency gratings

6. Effects of auditory deprivation (congenital deaf) • Processing of the M stimuli is enhanced. • Higher activation in MT-MST. • Visual attention to the periphery is enhanced.

7. Processing of the M stimuli is enhanced

8. Higher activation in MT-MST

9. Visual attention to the periphery is enhanced

10. Effects of auditory deprivation (congenital deaf) • Processing of the M stimuli is enhanced. • Higher activation in MT-MST. • Visual attention to the periphery is enhanced. • Components of the visual pathway that are specialized for high acuity vision (e.g., P pathway) exhibit fewer developmental redundancies (“errors”) (Chalupa & Dreher, 1991).

11. Sensitive period effects and mechanisms • Individuals who became deaf after the age of 4 do not display such enhancement. • mechanisms: redundancy of connections between auditory and visual areas • gradually decrease: birth to 3 years of age

12. gradually decrease

13. Overview • anatomy and physiology of the developing human brain • developmental specificity of visual functions in humans • developmental specificity in other neurocognitive domains • development specificity of language functions in humans

14. Developmental specificity in other neurocognitive domains • an advantage in sound localization for the blind that is largest at peripheral locations (Röder et al., 1997; Rice, 1965, Rauschecker & Kneipert, 1993) • functional participation of visual areas during somatosensory tasks

15. Functional participation of visual areas during somatosensory tasks sighted volunteers:no effect on tactile task early blind individuals:induce errors on tactile task (Cohen et al., 1997)

16. Functional participation of visual areas during somatosensory tasks • But, not all aspects of somatosensory processing recruit visual areas in blind subjects. • Simple tactile stimuli that did not require discrimination produced little activation in visual areas of blind subjects (Sadato et al., 1996). • Different neurocognitive systems and subsystems exhibit different sensitivities to altered experience.

17. Overview • anatomy and physiology of the developing human brain • developmental specificity of visual functions in humans • developmental specificity in other neurocognitive domains • development specificity of language functions in humans

18. development specificity of language functions in humans • lexical/semantic processing • “open-class” words, e.g., nouns, verbs • posterior temporal-parietal systems • grammatical processing • “closed-class” words, e.g., prepositions, conjunctions • frontal-temporal systems within LH • more vulnerable to delays in language experience

19. Evidences from Chinese-English bilinguals: grammar processing LH bilateral bilateral

20. Studies of congenital deaf adults:who learned English late and as 2nd language (1st language: American Sign Language, ASL) • response to open-class word • indistinguishable from normal and deaf adults • response to closed-class word (a, the, & his)

21. Studies of ASL • Whether the strongly biased role of the LH in language occurs independently of the structure and modality of the language first acquired? • ERP: ASL = English • fMRI: ASL = English • Yes!

22. ERP: ASL = English • But, for closed-class words • English: LH • ASL: bilateral activity • Acquisition of a language that relies on spatial contrasts and the perception of motion may result in the inclusion of RH into the language system. = ASL closed-class words

23. fMRI: ASL = English

24. Effects of primary language acquisition on cerebral organization = open class words ≠ open class words different systems p.s. link to language ability

25. Summary and conclusions:Systems employing fundamentally different learning mechanisms display different patterns of developmental plasticity • experience-dependent change throughout life • topography of sensory maps • lexical acquisition (i.e., object-word associations) • establishment of form, face and object representations (i.e., ventral pathway functions) • general, associative learning mechanisms

26. Summary and conclusions:Systems employing fundamentally different learning mechanisms display different patterns of developmental plasticity • modified by experience during limited periods in development • computing dynamically shifting relations between locations, objects, and events (i.e., including the dorsal visual pathway and the systems of the brain that mediate grammar)