Neurologically Speaking

1. Neurologically Speaking Part 4

4. New research on causes Origins of human impairment and illness Merzenich, 2003 � animal research A1 processing is �specialized� as the infant is exposed to specific sound stimuli � auditory cortex maps Perinatally generated maps can be distorted and persist into adulthood Variations occur depending on Input modulation rate Input intensity Complexity of stimuli Continuous noise

6. The critical period is the cortical �setup� epoch � Merzenich, 2006 Early exposure drives and shapes the initial form of the cortex�s processing machinery. That machinery is �specialized� to process environmental inputs. In babies, the primary sound processing specialization is for the child�s native language. Cortical specialization crucially enables the development of selective attentional control.

7. The critical period is the cortical �setup� epoch � Merzenich, 2006 Cortical specialization generates important functional changes that enable subsequent skill learning. At the end of the critical period, cortical maturation is paralleled by (causes) the maturation of modulatory control systems that results in the subsequent dominance of attentionally-controlled plasticity. From the end of the critical period forward to the end of life, cortical plasticity is powerfully gated by these modulatory control systems.

8. Variations occur by� input modulation rate input intensity Complexity of stimuli pulsed noise, variable rate continuous noise

9. Four ways to degrade sensory cortex (aural language and somatosensory cortex) development structured noise Zhang et al (2004) PNAS continuous, unmodulated noise Chang et al (2003) Nature Neurosci; Chang et al (2005) PNAS perinatal anoxia Strata et al (2005) PNAS non-coplanar PCBs (PBDEs?) Kenet et al (2006) submitted, Nature Medicine

10. A1 does not mature in infants raised in continuous noise In continuous noise reared rats, the critical period remains open indefinitely

15. Figure 3. Excitatory-inhibitory balance is disrupted in PCB-exposed animals. (a) Receptive field of excitatory (filled circles) and inhibitory (open circles) currents in control animals. Symbols indicate peak tone-evoked synaptic currents. Top: Currents from one A1 neuron. Bottom: Co-tuning and balance of mean (� s.e.m.) currents, normalized to peak excitatory and inhibitory responses, and centered on the best excitatory frequency of each cell (n = 16). (b) As in (a), but for PCB-exposed animals (n = 10). (c) Linear correlation coefficient r of peak excitation and inhibition. In control animals, tuning of excitation and inhibition is highly correlated, but this correlation is reduced in PCB-exposed animals. (d) Absolute difference in octaves between best frequency of excitatory and inhibitory currents. In control animals, the best frequency for inhibition tends to occur at or near the best frequency for excitation. In PCB-exposed animals, the difference between excitatory and inhibitory best frequencies is larger. Figure 3. Excitatory-inhibitory balance is disrupted in PCB-exposed animals. (a) Receptive field of excitatory (filled circles) and inhibitory (open circles) currents in control animals. Symbols indicate peak tone-evoked synaptic currents. Top: Currents from one A1 neuron. Bottom: Co-tuning and balance of mean (� s.e.m.) currents, normalized to peak excitatory and inhibitory responses, and centered on the best excitatory frequency of each cell (n = 16). (b) As in (a), but for PCB-exposed animals (n = 10). (c) Linear correlation coefficient r of peak excitation and inhibition. In control animals, tuning of excitation and inhibition is highly correlated, but this correlation is reduced in PCB-exposed animals. (d) Absolute difference in octaves between best frequency of excitatory and inhibitory currents. In control animals, the best frequency for inhibition tends to occur at or near the best frequency for excitation. In PCB-exposed animals, the difference between excitatory and inhibitory best frequencies is larger.

19. Beyond early infancy, plasticity is modulated as a function of: 

21. Some practical implications of these cortical plasticity studies:

22. A little more conversation, a littleless action � candidate roles for the motor cortex in speech perception Sophie K. Scott, Carolyn McGettigan and Frank Eisner Nature Reviews Neuroscience, April 2009

25. Language Learning Timetable

27. Differential Diagnosis (Chermak, et al, 1998) Rank order ADHD inattentive distracted hyperactive fidgety/restless hasty/impulsive interrupts/intrudes Rank order CAPD difficulty hearing in background noise difficulty following oral directions poor listening skills academic difficulties poor auditory assoc.. Distracted inattentive

28. Normal brain development versus ADHD My Videos\RealPlayer Downloads\ADHD brain development 1.mov Note that in ADHD development, especially of the prefrontal lobes (and perhaps right hemisphere significantly lag behind) � especially during adolescence

30. Furthermore�. �If, in early life, the brain�s primary training �signal� (aural speech) is consistently degraded (e.g. muffled or noisy)� It will result in an auditory/aural speech system that is specialized for the representation of bad (muffled, noisy) speech� Merzenich, 2003; Tallal, 2002

32. What are the most reliable assessments? Audiologists provide the most reliable testing although not all audiologists specialize in APD evaluation Speech-Language pathologists can often tell the warning signs and can screen for problems

33. Reliable audiological (non-language based) tests Pitch pattern analysis � Pinherio and Musiek Gap detection Masking Level Differences � a child with a MLD of <7 has problems listening in noise Bio-Mark ---- Biologic

34. What can be done about it? the immature auditory system can be modified Plasticity in older brains is powerfully modulated as a function of behavioral context Plastic changes can be induced on a grand scale

35. Different dimensions of adult cortical plasticity are enabled by the behaviorally-context-dependent release of: acetylcholine (focused attention/reward) (Kilgard, Bao) dopamine (reward, novelty) (Bao) norepinephrine (novelty) (Bollinger) serotonin (Bollinger) et alia

36. The human brain controls its own plasticity We have examples of: Acetylcholine-enabled plasticity Dopamine-enabled plasticity

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40. Plasticity in in older children depends on: Selective representations of behaviorally relevant inputs, actions, etc. ie. Must be meaningful and important Must have cortical processing and forebrain system specialization that match schedules of relevant inputs Ie. Brain must organize to match input Neuron that fire together wire together

41. Adult plasticity studies have been conducted in many other systems and models.

42. How does a brain SYSTEM coordinate its plasticity? Coordination comes from the top! Affirms importance of memory-based tasks in training. Working memory drives prediction (syntax), which is also expressed as system feedback. Effective coordination is crucial for sustaining attentional control

43. CAPD Management � traditional approaches Signal enhancement auditory training environmental modifications metacognitive [executive] strategies linguistic strategies metalinguistic strategies collaboration learning strategies

44. New materials Linguisystems The Central Auditory Processing Kit � 3 books $115.95 Auditory memory Auditory discrimination, closure and synthesis Figure-ground, cohesion, binaural integration

45. Pro-Ed It�s Time to Listen Patricia Hamaguchi Metacognitive activities for improving auditory processing in the classroom

46. Academic Communication Associates Listening Lessons for the early elementary classroom 5-8 years of age $34.95

47. What about AIT, TLP, Etc. ASHA has issued cautionary provisions regarding many of the programs because of minimal controlled research Developed largely to desensitize children who are hypersensitive to sound They might be effective in helping to organize the auditory system of very impaired children

48. Implications for central auditory system plasticity � cochlear implants Ponton, 2006 Impact of auditory deprivation (deafness) on spoken language development is minimized when CI occurs as early as possible Even as late as 7 years of age, maturation is possible Auditory short term memory (as marked by N1) continues as a deficit when children older than five years of age