Chapter 4:

1. Chapter 4: Sex Differences in Behavior: Animal and Human Models Examining the Neural and Neuroendocrine aspects of the Brain.

2. 4.2 Synapses may form either on dendritic spines or on the shaft of a dendrite The book correctly suggests that most synapses of interest occur on dendritic spines or on the shafts of dendrites. However, there are many other places where neural synapses may occur between neurons as well. We shall show some of these a bit later in the chapter.

3. 4.5 Cichlid fish show changes in neuronal cell size in response to social conditions These graphs are displaying the GnRH cell sizes seen in the preoptic area based upon four distinct social groups: NT = Non-territorial NT -> T = transitioned from non-territorial to territorial T = Territorial T -> NT transitioned from territorial to non-territorial

4. 4.8 Singing in female songbirds falls along a broad continuum Singing TENDS to be a sexually dimorphic trait in birds. In many cases, the female may be mute or have a very limited song repertoire. However, the Bay Wren is an example where both sexes sing equally as often.

5. Santiago Ramon Y. Cajal (1852-1934) Founding Scientist in the Modern Approach to Neuroscience. Received Nobel Prize in 1906

6. Figure 11.1: The nervous system’s functions, p. 388. Sensory input Integration Motor output

7. Figure 11.2: Levels of organization in the nervous system, p. 389. Key: Brain Central nervous system (CNS) Brain and spinal cord Integrative and control centers = Sensory (afferent) division of PNS = Motor (efferent) division of PNS Key: = Structure = Function Visceral sensory fiber Central nervous system (CNS) Peripheral nervous system (PNS) Cranial nerves and spinal nerves Communication lines between the CNS and the rest of the body Parasympathetic motor fiber of ANS Sympathetic motor fiber of ANS Visceral organ Spinal cord Skin Somatic sensory fiber Sensory (afferent) division Somatic and visceral sensory nerve fibers Conducts impulses from receptors to the CNS Motor (efferent) division Motor nerve fibers Conducts impulses from the CNS to effectors (muscles and glands) Motor fiber of somatic nervous system Skeletal muscle Sympathetic division Mobilizes body systems during activity Autonomic nervous system (ANS) Visceral motor (involuntary) Conducts impulses from the CNS to cardiac muscles, smooth muscles, and glands Somatic nervous System Somatic motor (voluntary) Conducts impulses from the CNS to skeletal muscles Peripheral nervous system (PNS) Parasympathetic division Conserves energy Promotes housekeeping functions during rest (b) (a)

8. Figure 11.3: Neuroglia, p. 390. Capillary Neuron (b) Microglial cell (a) Astrocyte Nerve fibers Myelin sheath Fluid-filled cavity Process of oligodendrocyte Brain or spinal cord tissue (c) Ependymal cells Cell body of neuron (d) Oligodendrocyte Satellite cells Schwann cells (forming myelin sheath) Nerve fiber (e) Sensory neuron with Schwann cells and satellite cells

9. Figure 11.4: Structure of a motor neuron, p. 392. Cell body (biosynthetic center and receptive region) Dendrites (receptive regions) Neuron cell body Nucleus Dendritic spine (a) Axon (impulse generating and conducting region) Impulse direction Nucleolus Node of Ranvier Nissl bodies Axon terminals (secretory component) Axon hillock Schwann cell (one inter- node) Neurilemma (sheath of Schwann) Terminal branches (telodendria) (b)

10. Figure 11.5: Relationship of Schwann cells to axons in the PNS, p. 394. Schwann cell cytoplasm Schwann cell plasma membrane Axon Myelin sheath Schwann cell nucleus (a) Schwann cell cytoplasm Axon Neurilemma (b) (d) Neurilemma Myelin sheath (c)

11. Figure 11.6: Operation of gated channels, p. 398. Neurotransmitter chemical attached to receptor Receptor Na+ Na+ Chemical binds K+ K+ Closed Open (a) Chemically gated ion channel Na+ Na+ Membrane voltage changes Closed Open (b) Voltage-gated ion channel

12. Figure 11.7: Measuring membrane potential in neurons, p. 399. Voltmeter Plasma membrane Ground electrode outside cell Microelectrode inside cell Axon Neuron

13. Figure 11.8: The basis of the resting membrane potential, p. 399. Cell exterior Na+ Na+ 15 mM Cell interior Na+ Na+ ion K+ 150 mM Diffusion us Na+–K+ pump Diff -70 mV Cl– 10 mM Na+ Na+ A– 100 mM Na+ 150 mM K+ Na+ Plasma membrane A– 0.2 mM Na+ K+ K+ 5 mM Cl– 120 mM K+ Cell interior Cell exterior K+ K+

14. Figure 11.9: Depolarization and hyperpolarization of the membrane, p. 400. Depolarizing stimulus Hyperpolarizing stimulus +50 +50 Inside positive 0 0 Inside negative Depolarization Membrane potential (voltage, mV) Membrane potential (voltage, mV) –50 –50 Resting potential –70 –70 Resting potential Hyper- polarization –100 –100 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 Time (ms) Time (ms) (a) (b)

15. Figure 11.10: The mechanism of a graded potential, p. 401. Depolarized region Stimulus Plasma membrane (a) Depolarization (b) Spread of depolarization

16. Figure 11.11: Changes in membrane potential produced by a depolarizing graded potential, p. 402. Active area (site of initial depolarization) Membrane potential (mV) – 70 Resting potential Distance (a few mm)

17. Outside cell Outside cell Na+ Na+ Inside cell K+ Inside cell K+ Repolarizing phase: Na+ channels inactivating, K+ channels open Depolarizing phase: Na+ channels open 2 Action potential +30 3 0 Relative membrane permeability 2 PNa Membrane potential (mV) PK Threshold –55 1 1 4 –70 0 1 2 3 4 Time (ms) Outside cell Sodium channel Potassium channel Outside cell Na+ Na+ Activation gates K+ Inside cell K+ Inside cell Inactivation gate Hyperpolarization: K+ channels remain open; Na+ channels resetting 4 1 Resting state: All gated Na+ and K+ channels closed (Na+ activation gates closed; inactivation gates open)

18. Figure 11.13: Propagation of an action potential (AP), p. 405. Voltage at 2 ms +30 Membrane potential (mV)) Voltage at 0 ms Voltage at 4 ms –70 (a) Time = 0 ms (b) Time = 2 ms (c) Time = 4 ms Resting potential Peak of action potential Hyperpolarization

19. Figure 11.14: Relationship between stimulus strength and action potential frequency, p. 406. Action potentials +30 Membrane potential (mV) – 70 Stimulus amplitude Threshold Voltage 0 Time (ms)

20. Figure 11.15: Refractory periods in an AP, p. 406. Absolute refractory period Relative refractory period Depolarization (Na+ enters) +30 0 Repolarization (K+ leaves) Membrane potential (mV) After-hyperpolarization –70 Stimulus 0 1 2 3 4 5 Time (ms)

21. Figure 11.16: Saltatory conduction in a myelinated axon, p. 407. Node of Ranvier Cell body Myelin sheath Distal axon

22. Figure 11.17: Synapses, p. 409. Cell body Dendrites Axodendritic synapses Axosomatic synapses Axoaxonic synapses Axon (a) Axon Axosomatic synapses Soma of postsynaptic neuron (b)

23. Figure 11.18: Events at a chemical synapse in response to depolarization, p. 410. Neurotransmitter Na+ Ca2+ Axon terminal of presynaptic neuron Action Potential Receptor 1 Postsynaptic membrane Mitochondrion Postsynaptic membrane Axon of presynaptic neuron Ion channel open Synaptic vesicles containing neurotransmitter molecules 5 Degraded neurotransmitter Na+ 2 Synaptic cleft 3 4 Ion channel closed Ion channel (closed) Ion channel (open)

24. Figure 11.19: Postsynaptic potentials, p. 412. +30 +30 0 0 Threshold Membrane potential (mV) Threshold Membrane potential (mV) –55 –55 –70 –70 10 20 Time (ms) 10 20 Time (ms) (b) Inhibitory postsynaptic potential (IPSP) (a) Excitatory postsynaptic potential (EPSP)

25. Figure 11.24: Types of circuits in neuronal pools, p. 422. Input Input Input Input 1 Input 2 Input 3 Output Output Output Output (a) Divergence in same pathway (b) Divergence to multiple pathways (c) Convergence, multiple sources (d) Convergence, single source Input Input Output Output (e) Reverberating circuit (f) Parallel after-discharge circuit

26. Why Study Bird Song? Bird song has been a classic behavioral response studied in animals to help us understand sexually dimorphic differences in brain organization. By studying bird song and the neural and neuroendocrine basis of bird song, we can better understand the principles of how the brain organizes itself during development. This information about bird song can then be used to understand and/or predict aspects of organization of the brain of other animals including in humans.

27. Major Regions of the Bird Brain Associated with Song: HVC = higher vocal center RA = robust nuclusu of the archistriatum nXIIts = hypoglossal nerve DM = dorsomedial region of the nucleus intercollicularis ICo = intercollicularis Syrinx = the vocal organ in birds that produces sound (equivalent to our larynx)

28. 1 tracheal ring 2 tympanum 3 pre MT syringeal rings 4 pessulus 5 membrana tympaniformis lateralis 6 membrana tympaniformis medialis 7 post MT syringeal rings 8 primary bronchi 9 bronchial cartilages • Syrinx • the name for the vocal organ of birds • located at the base of a bird's trachea • sound is produced by vibrations of the membranatympaniformisandpessulus • muscles modulate the sound by changing tension of the membranes and the bronchial openings • distinctly unlike the larynx of mammals, the syrinx is located where the trachea forks into the lungs • some songbirds can produce more than one sound pitch at a time

29. A typical bird syrinx.

30. 4.9 The neural basis of bird song Note that in the bird species with sexually dimorphic song abilities, these brain regions are typically much larger in males than in females of the species.

31. 4.10 Singing in zebra finches is organized by estrogens but activated by androgens Note that the far right column represents the typical developmental pattern for intact, adult male zebra finches. This further supports much of Young’s hypothesis concerning the organizational effects of early hormone secretion.

32. 4.11 The sonic organs are used by Type I male midshipman fish to attract females to their nests The sonic organs are sound producing muscles attached to the swim bladder in these fish. Type 1 males have well developed sonic organs (6x) compared to Type 2 males or females. The Type 1 male is an aggressive male. The Type 2 male has a “sneakier” reproductive behavior pattern. With this “sneaker” behavior, the Type 2 male has 900% larger gonad:body mass ratio compared to Type 1 males. Thought Questions: What does this suggest about the costs of sonic organ development? When would each male be more successful than the other?

33. 4.12 Urination postures of domestic dogs

34. 4.15 The frequency of rough-and-tumble and pursuit play (Part 1) Note that this is showing ROUGH-AND-TUMBLE play behavior. Study of Rhesus Monkeys The pseudohermaphrodites are females who received in utero exposure to exogenous androgens. This study suggests play behavior is MASCULINIZED by in utero exposure to these androgens.

35. 4.15 The frequency of rough-and-tumble and pursuit play (Part 2) Note that this is showing PURSUIT play.

36. 4.16 Contributions of activational and organizational effects of hormones to behavior It is very important to note that in the above, the human example is concerned with LEARNING, not development.

38. Known Brain Differences in Humans: SDN-POA = sexually dimorphic nucleus of the preoptic area of the hypothalamus. The volume of SDN in medial preoptic area is modified by hormones, among which testosterone is proved to be of much importance. The larger volume of male SDN is correlated to the higher concentration of fetal testosterone level in males than in females. From Roger Gorski’s Lab at Yale University: Coronal rat brain sections showing the SDN-POA A: male; B: female; C: female treated perinatally with testosterone; D: female treated perinatally with the synthetic estrogen diethylstilbestrol.

39. INAH-3 = the third interstitial nucleus of the anterior hypothalamus The INAH has been implicated in sexual behavior because of known sexual dimorphism in this area in humans and because it corresponds to an area of the hypothalamus that when lesioned, impairs heterosexual behavior in non-human primates without affecting sex drive. It has been reported to be smaller on average in homosexual men than in heterosexual men, and in fact has approximately the same size as INAH 3 in heterosexual women. The above information is based on Simon Levay’s work that was published in the journal Science in 1991. LeVay S (1991). A difference in hypothalamic structure between homosexual and heterosexual men. Science, 253, 1034-1037.

40. 4.17 Average sex differences in behavior often reflect significant overlap between the sexes

41. 4.18 Congenital absence of the olfactory bulbs in Kallmann syndrome Kallmann Syndrome - hypogonadism (decreased functioning of the glands that produce sex hormones) caused by a deficiency of gonadotropin-releasing hormone (GnRH) which is created by the hypothalamus. Alternative names include: hypothalamic hypogonadism or hypogonadotropic hypogonadism Males with this condition have smaller than average testes, are infertile, and express anosmia (the inability to detect odors) This is due to incomplete development of the olfactory bulb embryologically.

42. The lack of olfactory bulb development results in the lack of GnRH cell development (the cells in the olfactory bulb normally migrate during development to the hypothalamus

43. 4.19 A possible sex difference in the corpus callosum Corpus callosum - a structure of the mammalian brain in the longitudinal fissure that connects the left and right cerebral hemispheres. It facilitates communication between the two hemispheres. This may explain certain sexually dimporphic right/left communication disorders are more prevelant in males than females….. such as ADHD, schizophrenia. This may also suggest why females may have greater verbal cognition and why some task performance skills are sexually dimorphic…

44. 4.20 Performance on certain tasks favor one sex over the other Sexually Dimorphic Performance Behavioral Differences in Humans Test A = Matching Speed Test (Which house is the same as house #1?) Test B = Fine Motor Skills Tests Test C = Mathematical calculations Test D = Target Directed Motor Skills Test E = Mathematical Reasoning Test F = Spatial Orientation Skills Females > Males Males > Females

45. Box 4.5 Hormones, Sex Differences, and Art (Part 1)

46. Box 4.5 Hormones, Sex Differences, and Art (Part 2)

47. Female Male Female with CAH Female Male Female with CAH All drawings by children aged 5-7. Male

48. Congenital Adrenal Hyperplasia (CAH) - an autosomal recessive disease group resulting in mutations of genes for hormone production in the brain that guide the biochemical steps of production of cortisol from cholesterol by the adrenal glands (Corticotropin Releasing Hormone (CRH) or Corticotropin Inhibiting Hormone (CRIH)) CRIH is also sometimes called Atriopeptin. Most of these conditions involve excessive or deficient production of sex steroids and can alter development of primary or secondary sex characteristics in some affected infants, children, or adults.