Chapter 5 Development and Plasticity

of the Brain

Development of the Brain

• Plasticity

• Nature versus Nurture

• Rapid development

Fig. 5-1, p. 122

Fig. 5-2, p. 123

Development of the Brain.

• The human central nervous system begins to form when the embryo is approximately 2 weeks old.

Fig. 5-3, p. 123

Development of the Brain

• The fluid-filled cavity becomes the central canal of the spinal cord and the four ventricles of the brain.

Development of the Brain

• At birth, the human brain weighs approximately 350 grams.

• By the first year. the brain weighs approximately 1000 grams.

• The adult brain weighs 1200-1400 grams.

Development of the Brain

• The development of neurons in the brain involves the following four processes:

1. Proliferation

2. Differentiation

3. Myelination

4. Synaptogenesis

Fig. 5-6, p. 127

Development of the Brain

• Neurogenesis??

• Sperry’s (1954) research

Fig. 5-7, p. 127

Development of the Brain

• Neural Darwinism

• Neurotropin

• Apoptosis

• Nerve growth factor (NGF)

Development of the Brain

• Fetal alcohol syndrome

• Cocaine abuse

• Enriched versus impoverished environments

Fig. 5-10, p. 131

Fig. 5-11, p. 132

Fig. 5-12, p. 133

Plasticity After Brain Damage

• Survivors of brain damage show subtle to significant behavioral recovery.

• Some of the mechanisms of recovery include those similar to the mechanisms of brain development such as the new branching of axons and dendrites.

Plasticity After Brain Damage

• Possible causes of brain damage include:– Tumors– infections– exposure to toxic substances– degenerative diseases– closed head injuries.

Fig. 5-13, p. 138

Plasticity After Brain Damage

• A closed head injury

• A stroke or cerebrovascular accident– Ischemia– Hemorrhage– Edema-

How can we help?

• tissue plasminogen activator (tPA)

• Cooling the brain

• Cannabanoids

Fig. 5-14, p. 139

Plasticity After Brain Damage

• Diaschisis• Axonal regrowth• Collateral sprouts • Gangliosides• Progesterone

Fig. 5-16, p. 141

Fig. 5-17, p. 142

Plasticity After Brain Damage

• Ways the brain compensates for decreased input and to restores normal functioning include:

• Denervation supersensitivity

• Disuse supersensitivity

Plasticity After Brain Damage

• Phantom limb

• Deafferenated limbs