Lec4DevtVision

Lec4DevtVision - Lecture 4 NS Development Vision Outline...

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Lecture 4 NS Development Vision Outline for today • Brain development and plasticity • Vision • Today - Ch. 5, 6 (skip 6.3) • Next time: 8 (skip 8.1), 12, 13 • skip Ch. 7 Fig. 5-2, p. 123 2-3 weeks of age (during gestation) Fig. 5-1a, p. 122 Babies < 9 months show interest in objects…
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Fig. 5-1b, p. 122 …but not if it is out of view How do neurons know specifically where to go? • Axons must travel great distances across the brain to form the correct connections. • Sperry’s (1954) research with newts indicated that axons follow a chemical trail to reach their appropriate target. • Growing axons reach their target area by following a gradient of chemicals in which they are attracted by some chemicals and repelled by others. Fig. 5-7, p. 127 The protein TOP DV is concentrated in the Ventral tectum. Axons rich in TOP DV attach to tectal neurons that are also rich in that chemical. Similarly, a second protein directs axons from the posterior retina to the anterior portion of the tectum. Retinal axons match up with neurons in the tectum by following two gradients. Fig. 5-6, p. 127 Sperry = Cut optic invert eye = optic nerve axons grow back to original targets. Evid. for chemical guide
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Fig. 5-8, p. 129 Apoptosis of motor neurons in ventral spinal cord of human fetus Axons that fail to make synapses die VIDEO 1: Secret Life of the Brain - baby cataracts Visual system neurons: use it or lose it Fig. 5-14, p. 139 VIDEO 2: Secret Life of the Brain - stroke recovery of penumbra?
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Plasticity After Brain Damage • Phantom limb refers to the continuation of sensation of an amputated body part • Can lead to the feeling of sensations in the amputated limb when other body parts are stimulated • Cortex reorganizes after amputation: Original somatosensory cortical axons degenerate leaving vacant synaptic sites into which others axons sprout. • Example: amputated hand ctx neurons degenerate, face neurons move (sprout) in Fig. 5-16, p. 141 Fig. 5-18, p. 143 VIDEO 3: Phantom limbs
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language of the brain • Each of our senses has specialized receptors that are sensitive to a particular kind of energy. • Receptors transduce (convert) energy into electrochemical patterns. • Receptors for vision transduce light. Which neurons are active is key • Law of specific nerve energies states that activity by a particular nerve always conveys the same type of information to the brain.
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Lec4DevtVision - Lecture 4 NS Development Vision Outline...

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