Abstract: Insect behavior can be controlled by a single odor compound or by a blend of a few components in an exact ratio of concentrations. These odor compounds or odor mixtures are called pheromones if used for intraspecific communication. Each of the pheromone components is perceived by a particular type of receptor cell that is specifically tuned to its "key compound" and may respond to single odor molecules by firing single nerve impulses. The entire response range of a receptor cell may cover many decades of stimulus intensities. Each olfactory receptor cell is a bipolar neuron. Its dendrite innervates a specialized cuticular structure, usually a hollow cuticular hair that captures the stimulus molecules. The axon runs directly to the deutocerebrum-the first synaptic relay station of the central nervous system. Chemo-electrical transduction in these organs comprises the processes leading from the adsorption of odor molecules on the cuticular surface via stimulus transport to the generation of receptor potentials and nerve impulses and, eventually, to the inactivation of the stimulus molecules. The interconnections of these processes and their influences on the ultimate impulse response of the receptor cells are largely unknown. This review covers electrophysiological investigations of cellular response charac­ teristics as well as biophysical and biochemical work, much of which is based on radiolabeled pheromone compounds. These studies employed a few species of insects, mainly of moths with olfactory organs that are relatively large and accessible for experimental work. The olfactory hairs of

Abstract: The interaction of an odorant with the chemosensitive membrane of olfactory receptor neurons initiates a sequence of molecular and membrane events leading to sensory transduction, impulse initiation, and the transmission of sensory information to the brain. The main steps in this sequence are summarized in Figure 6. Several lines of evidence support the hypothesis that the initial molecular events and subsequent stages of transduction are mediated by odorant receptor sites and associated ion channels located in the membrane of the cilia and apical dendritic knob of the olfactory receptor neuron. Similarly, the membrane events associated with impulse initiation and propagation are mediated by voltage-gated channels located in the initial axonal segment and the axolemma. The ionic and electrical events associated with the proposed sequence have been characterized in general using a variety of experimental techniques. The identification, localization, and sequence of membrane events are consistent with the neurophysiological properties observed in specific regions of the bipolar receptor neuron. The influence of other cells in the primary olfactory pathway such as the sustentacular cells in the olfactory epithelium, the Schwann cells in the olfactory nerve, and the astrocytes in the olfactory nerve layer in the olfactory bulb on the physiological activity of the olfactory receptor neuron is an emerging area of research interests. The general principles derived from the experimental results described in this review provide only a framework that is both incomplete and of necessity somewhat speculative. As noted in the Introduction, the multidisciplinary study of the primary olfactory pathway is undergoing a renaissance of research interest. The application of modern biophysical, cell, and molecular biological techniques to the basic issues of odorant recognition and membrane excitability will clarify the speculations and lead to the establishment of new hypotheses. Three broad areas of research will benefit from such studies. First, the application of biophysical techniques will lead to a detailed characterization of the membrane properties and associated ion conductance mechanisms. Second, the isolation and biochemical characterization of intrinsic membrane and cytosolic proteins associated with odorant recognition, sensory transduction, and the subsequent electrical events will result from the utilization of cell and molecular biological techniques.(ABSTRACT TRUNCATED AT 400 WORDS)

Abstract: The sensory neurons of the olfactory epithelium, as a consequence of their odor detection function, contact both the external environment and the central nervous system. The possibility that substances applied to the epithelium might reach the central nervous system was investigated by the intranasal application of peroxidase-conjugated wheat germ agglutinin (WGA-HRP). WGA-HRP was transported through olfactory receptor axons to the glomerulus of the olfactory bulb. Reaction product was localized electron microscopically to tubulovesicular profiles and dense bodies in sensory axons. Evidence of transneuronal transport was indicated by reaction product localized in dense bodies in dendrites postsynaptic to receptor cell axons. Periglomerular, tufted and mitral cells in the olfactory bulb also were transneuronally labeled. Anterograde transneuronal labeling occurred in the olfactory tubercle, piriform cortex and surrounding the lateral olfactory tract. Retrograde transneuronal label was found in neurons of the basal forebrain with the largest number of perikarya in the lateral nucleus of the horizontal limb of the diagonal band, a major source of cholinergic afferents to the olfactory bulb. These data suggest that substances, specifically those which bind to receptors, are transported from the olfactory receptor neurons in the nasal epithelium to the brain. Thus, the olfactory system may provide a route of entry for exogenous substances to the basal forebrain.

Abstract: In the hawkmoth, Manduca sexta, the third segment of each labial palp contains a pit, which houses a densely packed array of sensilla. We have named this structure the labial pit organ (LPO). The sensilla within the pit are typical of olfactory receptors, characterized by a grooved surface, wall pores, and pore tubules. Axons arising from receptor cells that innervate these sensilla project bilaterally to a single glomerulus in each antennal lobe. We have compared this central projection with that in three other species of Manduca (M. quinquemaculata, M. dilucida, and M. lanuginosa) and in the silkmoths Antheraea polyphemus and Bombyx mori. A bilateral projection to a single glomerulus in each antennal lobe is present in all cases. We suggest that the LPO serves as an accessory olfactory organ in adult Lepidoptera.

Abstract: Cilia at the tips of dendritic processes of olfactory receptor cells are the sites of initial recognition and transduction events in olfactory reception. We have detached cilia from the olfactory epithelium of the bullfrog, Rana catesbeiana, via a calcium shock and partially purified them in high yield (226 +/- 19 micrograms protein/frog, n = 14) by sucrose gradient centrifugation. The cilia appear to undergo osmotic lysis during the isolation procedure, forming isolated axonemal structures and ciliary plasma membrane vesicles with diameters of 100–500 nm and an internal volume of 2.3 +/- 0.5 microliter/mg protein. PAGE in SDS reveals approximately 30 protein bands, among which cytoskeletal components, such as tubulin and actin, are readily identifiable by immunoblotting. Approximately 15 glycoprotein bands reactive with concanavalin A are discernible with major glycopeptides at apparent molecular weights of 56–65, 95, and 116 kDa. In contrast to olfactory cilia, respiratory cilia, isolated from the palate of the frog, do not contain the prominent glycopeptides observed for olfactory cilia. The 56–65 kDa glycopeptide region reacts with antiserum against chick kidney, Na+/K+-ATPase, and contains the beta subunit of this enzyme. In addition, we have identified the alpha and beta subunits of a guanine nucleotide-binding protein (G-protein) in the olfactory cilia preparation. This preparation of isolated olfactory cilia from Rana catesbeiana represents a readily accessible model system for studies of initial events in chemosensory recognition and signal transduction in the olfactory system.

Abstract: The olfactory system in vertebrates comprises a highly specialized sensory organ for detection and identification of minute quantities of chemicals in the environment. Experimental studies have documented the role played by olfactory information in social relationships, prey or predator recognition, and the search for food. The demands imposed by the aquatic environment have made the olfactory apparatus of fish a sensory system with many specialized features. At present only a few properties of the fish olfactory organ have been investigated.

Abstract: Recent evidence suggesting involvement of the central olfactory system in Alzheimer's disease (AD) was assessed by contrasting olfactory and visual discrimination in 15 probable AD subjects and 6 healthy aged controls. Control subjects performed better than AD subjects on both tasks. Mild AD subjects performed better than moderate AD subjects on visual discrimination, although the two groups did not differ on olfactory discrimination. Positron emission tomographic (PET) studies with (F‐18)2‐fluoro‐2‐deoxy‐D‐glucose performed on 11 of the AD subjects showed no relation between olfactory performance and cerebral metabolic asymmetries, but relations to visual discrimination were found.

Abstract: It is generally accepted that the olfactory system is unique among the senses since the olfactory receptor cells, which are primary neurons, are thought to have a limited life span. Implicit in the current literature is the notion that these receptor cells are born, live and die by some “inherent clock” which, in mammals, lead to neuronal death after about 30 days (Moulton 1974; Graziadei and Monti Graziadei 1979). The turnover of receptor cells and their “programmed” replacement from a basally located progenitor cell compartment is thought to continue throughout the life of an animal and at a constant rate. This concept has gradually developed since Nagahara (1940) first reported the appearance of mitotic activity in the olfactory epithelium proprium of adult mice. Mitosis of basally located progenitor cells and repair of experimentally destroyed sensory cells was subsequently confirmed in a variety of other species (Lams 1940; Schultz 1941, 1960; Smith 1951; Bimes and Planel 1952; Westerman and von Baumgarten 1964; Andres 1965; Thornhill 1970; Craziadei and Metcalf 1971; Craziadei and Dehan 1973; Moulton 1974; Graziadei 1973; Breipohl and Ohyama 1981; Simmons et al. 1981; Matulionis 1982). Recent investigations on cell proliferation, cell death and repair by Hinds et al. (1984), Balboni and Vannelli (1982), Matulionis (1982) and our own group (Breipohl 1982b; Breipohl et al. 1985 a,b; 1986) lead to some doubt about a constant turnover of olfactory receptor cells throughout life.

Abstract: An anatomically distinct group of glomeruli, termed the modified glomerular complex (MGC), is present in the posterior dorsomedial portion of the main olfactory bulb. This region has been strongly implicated as part of the pathway that processes odor cues for suckling in neonatal rat pups. We studied the distribution pattern of olfactory receptor neurons that project to the MGC region after ionophoretic injections of WGA-HRP into the olfactory bulbs of 12-day-old rat pups. HRP label was confined to an identifiable localized region in the MGC of the main olfactory bulb. Label extended over 2-7% of the glomerular sheet of the main olfactory bulb, including the MGC. Olfactory receptor neurons within the olfactory epithelium of the nasal cavity were labeled with HRP ipsilateral to the injected side. Maps constructed of the olfactory epithelium revealed that the labeled neurons occurred within topographically defined regions. Anteriorly, labeled olfactory neurons were confined to a narrow strip medial to the dorsal recess, and, more posteriorly, this strip widened medially along the septal wall and laterally onto a limited area on the nasal turbinates. Only a portion of the receptor population within a region was labeled. The boundaries between labeled and unlabeled regions were sharp. These findings support the concept that the olfactory epithelium is an anatomical mosaic in which receptors with different glomerular projections sites are intermingled. In conjunction with previous evidence on the functional specificity of the MGC, and staining of receptor neuron subgroups with monoclonal antibodies, these findings further suggest that olfactory receptor neurons form a functional mosaic within the olfactory epithelium.

Abstract: Central projections of the nervus terminalis (n.t.) in the goldfish were investigated using cobalt- and horseradish peroxidase-tracing techniques. Single n.t. fibers were identified after unilateral application of cobalt chloride-lysine to the rostral olfactory bulb. The central course and branching patterns of individual n.t. fibers were studied in serial sections. Eight types of n.t. fibers are differentiated according to pathways and projection patterns. Projection areas of the n.t. include the contralateral olfactory bulb, the ipsilateral periventricular preoptic nucleus, both retinae, the caudal zone of the periventricular hypothalamus bilaterally, and the rostral optic tectum bilaterally. N.t. fibers cross to contralateral targets in the anterior commissure, the optic chiasma, the horizontal commissure, the posterior commissure, and possibly the habenular commissure. We propose criteria that differentiate central n.t. fibers from those of the classical secondary olfactory projections. Branching patterns of eight n.t. fiber types are described. Mesencephalic projections of the n.t. and of secondary olfactory fibers are compared and discussed with regard to prior reports on the olfactory system of teleosts. Further fiber types for which the association with the n.t. could not be established with certainty were traced to the torus longitudinalis, the torus semicircularis, and to the superior reticular nucleus on the ipsilateral side.

Abstract: For the first time in cetaceans, the development of the terminalis system and its continuity between the olfactory placode and the telencephalon has been demonstrated by light microscopy. In the early development of toothed whales (Odontoceti) this system is partially incorporated within the fila olfactoria which grow out from the olfactory placode. As the peripheral olfactory system is reduced in later stages, a strongly developed ganglionlike structure (terminalis ganglion) remains within the primitive meninx. Peripherally it is connected via the cribriform plate with ganglionic cell clusters near the septal mucosa. Centrally it is attached to the telencephalon (olfactory tubercle, septal region) by several nerve fibre bundles. In contrast to all other mammalian groups, toothed whales and dolphins are anosmatic while being totally adapted to aquatic life. Therefore the remaining ganglion and plexus must have non-olfactory properties. They may be responsible for the autonomic innervation of intracranial arteries and of the large mucous epithelia in the accessory nasal air sacs. The morphology, evolution and functional implications of the terminalis system in odontocetes and other mammals are discussed.

Abstract: In order to assess the role of input-target interactions in the development of olfactory ccrtex, the primary afferent fibers from the olfactory bulb to the superficial part of layer I of the cortex (layer Ia) were removed in developing and mature rats. After survival periods that vary from a few days to 2–6 months, changes were assessed in (1) the radial thickness of layer I, (2) the laminar distribution of intracortical associational fibers, which normally terminate in a deep part of layer I (layer Ib), and (3) the distribution of glia in layer I. The findings indicate that the lamination of fibers within layer I is not intrinsically prespecified, but gradually becomes “set” during the first month after birth. If the fibers from the olfactory bulb are removed, the dendrites of cortical cells are capable of accepting inputs from other fiber systems, depending on the maturational state of the dendrites and the ingrowing axons. Development of the abnormal inputs is associated with relatively normal dendritic growth, whereas lack of adequate input results in dendritic atrophy. Thus, after neonatal bulb ablation, the intracortical fibers occupy both superficial and deep parts of layer I, and a normal synaptic density is established throughout the layer. Layer I also develops to nearly its normal adult thickness, although the high density of glia that normally characterizes layer Ia is not apparent. With bulb ablation at progressively older ages (from postnatal day (P-) 3 to 21), the cortical associational fibers show progressively less extension into the denervated layer Ia. Layer I continues to grow, but rut to the same extent as after P-1 ablations. In these experiments the glia distribution resembles the pattern present at the time of denervation. After adult olfactory bulb albation, the long intracortical fibers extend very little into layer Ia, which undergoes pronounced shrinkage and becomes filled with a high concentration of glia. However, partial reinnervation of layer Ia is accomplished by the proliferation of a normally sparse native fiber system, which has been identified only with the Timm method. These results are interpreted as evidence that the normal development of lamination of afferent fibers to the olfactory cortex depends on axodendritic interaction during development.

Abstract: 55 Morest, D. K., A study of neurogenesis in the forebrain of opossum pouch young. Z. Anat. Entwickl.-Gesch. 130 (1970) 265-305. 56 Moulton, D. G., Celebi, G., and Fink, R. P., Olfaction in mammals two aspects: Proliferation of cells in the olfactory epithelium and sensitivity to odours, in: Taste and Smell in Vertebrates, pp. 227246. Eds G. Wolstenholme and J. Knight, J.A. Churchill, London 1970. 57 Ooteghem, S. Van, Schumacher, S., and Shipley, M.T., The ontogenic development of acetylcholinesterase activity in the rat olfactory bulb. AChemS VI Abstr. (1984) 131. 58 Pedersen, P.E., and Blass, E.M., Prenatal and postnatal determinents of the 1st suckling episode in albino rats. Devl Psychol. 15 (1982) 349-355. 59 Pedersen, E., Williams, C.L., and Blass, E.M., Activation and odor conditioning of suckling behavior in 3-day-old rats. J. exp. Psychol.: Animal Behav. Proc. 8 (1982) 329-341. 60 Pinching, A. J., and Powell, T. P. S., The neuron types of the glomerular layer of the olfactory bulb. J. Cell Sci. 9 (1971) 305-345. 61 Pinching, A. J., and Powell, T. P. S., The neuropil of the glomeruli of the olfactory bulb. J. Cell. Sci. 9 (1971) 347-377. 62 Pinching, A.J., and Powell, T. P. S., The neuropil of the periglomerular region of the olfactory bulb. J. Cell Sci. 9 (t971) 379~t09. 63 Powell, T.P.S., Cowan, W.M., and Raisman, G., The central olfactory connections. J. Anat. 99 (1965) 791-813. 64 Price, J.L., An autoradiographic study of complementary laminar patterns of termination of afferent fibers to the olfactory cortex. J. comp. Neurol. 150 (1973) 8%108. 65 Price, J. L., and Powell, T. P. S., An electron-microscopic study of the termination of the afferent fibers to the olfactory bulb from the cerebral hemisphere. J. Cell Sci. 7 (1970) 157-187. 66 Price, J. L., and Powell, T. P. S., An experimental study of the origin and the course of the centrifugal fibers to the olfactory bulb in the rat. J. Anat. 107 (1970) 215-237. 67 Rolls, E.T., Sanghera, M.K., and Roper-Hall, A., The latency of activation of neurones in the lateral hypothalamus and substantia innominata during feeding in the monkey. Brain Res. 164 (1979) 121-135. 68 Rudy, J. W., and Cheatle, M. D., Odor-aversion learning in neonatal rats. Science 198 (1977) 845-846. 223

Abstract: On the basis of morphology and arrangement of cell types, the olfactory tubercle (OT) of the cat is divided into two main components: a cortical part and the cap/hilus regions in which cortical characteristics are not recognizable. The cortical part undergoes a gradual transformation from a more cortex-like structure in the lateral half of the OT — possibly related to the presence of olfactory fibers — to a more striatum-like organization in the medial half. Cell bridges extend between the polymorph layer of the cortical part and the striatum and especially the n. accumbens. The cap regons form 8 or 9 superficial grooves running in a rostro-caudal direction. They contain dwarf and small pyramidallike neurons and lie immediately ventral to the granule islands of Calleja. Dwarf and small pyramidal-like neurons give rise to an ascending axonal plexus which may contact large neurons in the hilus regions dorsal to the Calleja islands and in part also neurons of the ventral pallidum, the dendrites of which enter the lateral hilus zones. The proportion of dwarf cells to granule cells in the cap regions gradually reverses from lateral, where dwarf cells dominate, to medial, where the caps contain almost exclusively granule cells. No interconnections are observed between the two components of the OT.

Abstract: The presence of synaptic glomeruli in the olfactory afferent pathway of vertebrates and arthropods is a striking example of neuroanatomical convergence. To test the generality of this analogy, the olfactory receptors in a terrestrial snail, Achatina fulica, were labeled and traced by application of horseradish peroxidase to the epithelial surface at the tip of the posterior tentacles. All afferent fibers enter the digitary extensions of the tentacular ganglion. The majority of fibers travel through the digits to terminate either in the tentacle ganglion per se or in the cerebral ganglion. About 10% of the afferent axons terminate in glomeruli within the digits. The glomeruli are characterized by dense neuropils, numerous synaptic contacts, and enclosure by glia cells and glial processes. Periglomerular interneurons lie in close proximity to the glomeruli. There are about 20 glomeruli per tentacle. They have irregular shapes with a mean individual volume of 38 × 10-5 mm3.

Abstract: Adult olfactory cortical neurons in layer IIa undergo fulminant transneuronal degeneration after removal of afferent olfactory bulb fibers (Price, '76, Neurosci Abst. 2:161; Heimer and Kalil, '78, J. Comp. Neurol 178:559-609). This provides an unusual example of dependence of a mature population of neurons on axonal input. In order to investigate whether similar transneuronal degeneration occurs in immature animals, a series of rats were subjected to unilateral olfactory bulb removal at various ages during the first 3 postnatal weeks. The brains were examined for degeneration after short survivals by use of the de Olmos cupric silver method, which selectively stains degenerating neurons. In addition, animals with long survivals were examined with the HRP retrograde tracing method, in order to determine if cells that survive the acute effects of deafferentation develop normal patterns of connections. Young neurons are more resistant to the effects of olfactory bulb removal than more mature neurons. There was little degeneration of cortical neurons after bulb ablation during the first 2 postnatal, weeks. Although layer IIa does not become distinct from layer IIb in, these experimental animals, cells that have connections normally characteristic of the cells of layer IIa, and are situated at the superficial edge of layer II, were identified with the HRP method. The severity of transneuronal degeneration increases and becomes adultlike between the second and third postnatal weeks. This increase in transneuronal degeneration is temporally associated with a progressive reduction in axonal sprouting following deafferentation during the first 3 postnatal weeks, as described in the companion paper (Friedman and Price, '86). Thus, axon sprouting may “protect” the immature IIa neurons from the effects of removal of the fibers from the olfactory bulb. A period of normal cell death has also been identified in olfactory cortex by the use of the de Olmos cupric silver method. This cellular degeneration is much less severe and has a different time course and laminar distribution than the transneuronal degeneration produced by olfactory bulb ablation in adults. Although normal cell death appears to be potentiated by removal of the olfactory bulb on postnatal day 1, it is clearly a different process from the transneuronal reaction.

Abstract: Central connections of the olfactory bulb of Polypterus palmas were studied with the use of horseradish peroxidase and cobalt-tracing techniques. The olfactory bulb projects to subpallial and palliai areas in the ipsilateral telencephalon; a projection to the contralateral subpallium is noted via the habenular commissure. A further target of secondary olfactory fibers is a caudal olfactory projection area in the ipsilateral hypothalamus. No labeling was seen in the anterior commissure and in the contralateral olfactory bulb. The medial and the lateral pallium receive secondary olfactory fibers in distinct areas. Neurons projecting to the bulb are found in the ipsilateral subpallium, mainly in one dorsal longitudinal nucleus. The main connection with the tel- and diencephalon is mediated via the medial olfactory tract. This tract also contains fibers to the contralateral telencephalon, and to the hypothalamus. The smaller lateral olfactory tract mediates fibers to the lateral pallium. The organization of pathways of secondary olfactory fibers in the telencephalon is described. The present findings are compared to those obtained in species possessing an inverted forebrain.

Abstract: Content.- 1 Early Development of Behavior and the Nervous System: An Embryological Perspective.- Some Embryological Findings.- Early Neural Development.- Neurobehavioral Development: The Role of Neural Activity.- Behavioral Embryology: Practice and Perceptual Experience.- References.- 2 Motor Patterns in Development.- Preliminary Issues.- Approach Taken.- Review of Issues.- Basic Dimensions of Movement.- Spontaneous and Elicited Movements.- Higher-Order Motor Patterns.- Socially Integrated Motor Patterns.- Some Personal Explorations.- Rodent Motor Patterns.- Conditioned Movement Sequences and Stereotypies.- Canid Motor Patterns.- Emergent Issues.- Developmental Processes: A Motor Perspective.- Capabilities and Strategies.- Perspectives on Mechanism.- Summary Themes and Conclusions.- References.- 3 Environmental and Neural Determinants of Behavior in Development.- Suckling as an Organized Behavior.- External Controls.- Internal Controls of Suckling.- Suckling and Reinforcement.- Huddling.- Independent Ingestion.- Water Intake.- Nutrient Intake.- Brain Stimulation and Behavioral Organization.- Discussion.- Concluding Remarks.- References.- 4 The Ontogeny of Vocal Learning in Songbirds.- Background.- Behavioral Data.- Theoretical Framework.- Neuroanatomical Data.- Sexual Dimorphisms and Brain-Behavior Correlations.- Neural Correlates of Song Learning.- The Auditory Template.- Auditory-Motor Integration: The Matching Process.- The Central Motor Program.- Possible Mechanisms of Song Learning.- Development of the Central Motor Program.- Sensitive Periods for Song Learning.- Song Learning and Brain Volume Changes.- Relations of Avian and Human Vocal Learning.- Similarities Between Vocal Learning in Birds and Humans.- Relationships Between Vocal Perception and Production.- References.- 5 Early Development of Olfactory Function.- Main Olfactory Epithelium.- Vomeronasal Organ.- Main Olfactory Bulb.- Accessory Olfactory Bulb.- Central Olfactory Projections.- Modified Glomerular Complex.- The Ontogeny of Olfactory Function: Overview.- Prenatal Activity in the Accessory Olfactory Bulb.- Early Postnatal Activity in the MGC.- Postnatal Activity in the Main Olfactory Bulb.- Discussion.- References.- 6 Development of the Sense of Taste.- Development of the Rat Gustatory System.- Changes in Electrophysiological Responses from Peripheral Taste Nerves.- Anatomical Correlates of Response Changes in Peripheral Taste Nerves.- Changes in Electrophysiological Responses from Central Nervous System Taste Neurons and Behavioral Implications.- Attempts to Modify the Rat Gustatory System through Early Experience.- Development of the Sheep Gustatory System and Applications to Development of Taste Responses in Humans.- Changes in Electrophysiological Responses from Peripheral Taste Nerves.- Anatomical Correlates of Response Changes in Peripheral Taste Nerves.- Changes in Electrophysiological Responses from Central Nervous System Taste Neurons and Implications for Human Behavioral Responses.- Proposed Membrane Changes Underlying Development of Taste Responses.- Summary.- References.- 7 The Tunable Seer: Activity-Dependent of Vision.- Experience-Dependent Developmental Programs.- The Retino-Geniculo-Cortical Pathway in Adult Cats.- Functional Specialization in the Retina.- Parallel Pathways in the Visual System.- Orientation Selectivity of Area 17 Cells.- Distribution of Preferred Orientations in Retina, Lgn, and Area 17.- Development of the Retino-Geniculo-Cortical Pathway in Normal Cats.- Optics and Alignment of the Eyes.- Retinal Development.- Lgn Development.- Development of Area 17.- Activity-Dependent Development of the Visual System.- Neuronal Activity and Subcortical Development.- Neuronal Activity and Cortical Development.- Factors Controlling Differences in Experience Sensitivity of Cortical Cells.- Extraretinal Factors in Visual System Development.- Behavioral Significance of Experience-Dependent Changes.- Development of Visually Guided Behavior in the Kitten.- Correlating Behavioral and Visual System Development.- Effects of Stripe-Rearing on Visual Development.- Experience-Dependent Changes in "Attention".- Summary: The Tunable Seer.- Developmental Changes.- Experience-Dependent Changes in Area 17.- Behavioral Significance of Experience-Dependent Development.- Integration of Genetic and Environmental Information.- Implications of Experience-Dependent Development.- References.- 8 Development of Thermoregulation.- Thermal Aspects of Embryonic Development.- Sexual Differentiation.- Development of Thermoregulation.- Strategies for Thermoregulation.- Maternal Defense of Neonatal Temperature.- Adaptive Features of Hypothermia.- Mechanisms of Thermoregulation in Young Mammals.- Physiological Mechanisms.- Behavioral Mechanisms.- Plasticity in the Development of Thermoregulatory Capacity.- Effects of Being Reared in Different Ambient Conditions.- Thermal Mediation of Early Experience.- Thermal Activation.- Summary.- References.