Cats were subjected to complete lower brainstem transection, and were then tested for learning ability according to a classical conditioning paradigm. An auditory stimulus was systematically paired with a brief shock to the eyelid. Within a few weeks after the operation, the decerebrate cats could learn the conditioned response with a tone frequency discrimination and then a discrimination reversal. Our results support the notion that the brainstem reticular formation can support a conditioned response which isbehaviorally similar to that obtained in the intact animal.

The neurological development of the kitten was studied from birth to 120 days of age. Three motor features present at birth disappeared within the 1st 45 days of life. The labyrinthine head and body righting reactions were present at birth; the latter matured only by 25 days of age when the air righting reaction (mature by 35 days) started to appear. Limb placing reactions developed progressively with proprioceptive components being present at birth whereas tactile components evolved slowly from early contact lifting to forepaws contact placing (60 days) and narrow plank walking (75 days). Standing and walking were well developed by 45 days. Eye opening occurred at 9.5 days and several eyeblink reactions (including blink to light) were present at birth. Adequate binocular coordination was seen by 47 days. Vision progressed parallel to the clearing of the ocular media which were fairly transparent by 32 days. Visually guided paw placing and the visuopalpebral blink reflex matured later (by 37 and 59 days, respectively). The external auditory canal and pinna were fully developed by 12 and 31 days, respectively; spontaneous and tactile pinna movements were present at birth; orienting to animal and nonanimal sounds was well developed by 6.5 and 18 days, respectively; spatial sound localization was developed by 16 days and differential responding to animal sounds matured by 24.5 days. Somatic responses and olfaction were present at birth but matured further thereafter. Playful interactions between kittens started by 10--15 days and well developed play behavior was seen by 36--40 days. In brief, all neurological functions mature progressively during the 1st 3 postnatal months.

Summary: Previously, using positron emission tomogra phy (PET), we showed that local cerebral metabolic rates for glucose (lCMRglc) in children undergo dynamic mat urational trends before reaching adult values. In order to develop an animal model that can be used to explore the biological significance of the different segments of the lCMRglc maturational curve, we measured lCMRglc in kit tens at various stages of postnatal development and in adult cats using quantitative [14C]2-deoxyglucose autora diography. In the kitten, very low lCMRg1c levels (0.14 to 0. 53 f.Lmol min -I g -I ) were seen during the first 15 days of life, with phylogenetically older brain regions being generally more metabolically mature than newer struc tures. After 15 days of age, many brain regions (particu larly telencephalic structures) underwent sharp increases of lCMRglc to reach, or exceed, adult rates by 60 days. This developmental period (15 to 60 days) corresponds to the time of rapid synaptic proliferation known to occur in the cat. At 90 and 120 days, a slight decline in lCMRglc Using positron emission tomography (PET), we have previously described the distribution and ab solute rates of local cerebral glucose utilization in the normal human brain from birth to adulthood (Chugani and Phelps, 1986;Chugani et al., 1987 Abbreviations used: BHB, f3-hydroxybutyrate ; 2DG, 2-deoxyglucose; PET, positron emission tomography . 35was observed, but this was followed by a second, larger peak occurring at about 180 days, when sexual matura tion occurs in the cat. Only after 180 days did ICMRglc decrease to reach final adult values (0.21 to 2.04 f.Lmol min -I g -I ) . In general, there was good correlation be tween the metabolic maturation of various neuroanatom ical regions and the emergence of behaviors mediated by the specific region. At least in the kitten visual cortex, which has been extensively studied with respect to de velopmental plasticity, the "critical period" corre sponded to that portion of the lCMRg1c maturational curve surrounding the 60-day metabolic peak. These nor mal maturational ICMRglc data will serve as baseline val ues with which to compare anatomical and metabolic plasticity changes induced by age-related lesions in the cat. Key Words: Cerebral glucose utilization-Brain de velopment-Positron emission tomography-Auto radiography-Plasticity-Cat.metabolic rates for glucose (lCMR g lc) in most brain areas undergo dynamic maturational changes over a rather protracted period. The typically low neonatal values of ICMR g lc rapidly increase from birth and begin to exceed adult values in the second and third postnatal year. By about 4 years, a plateau is reached that extends until about 9 years; following this, there is a gradual decline in ICMR g lc to reach adult values by the end of the second decade. The relative increase in ICMR g lc over adult values is most pronounced in neocortical regions, which at their peak have over a twofold higher ICMR g lc than corresponding adult values. Phylogenetically older structures (e.g.,...

SUMMAR Y This paper reviews the lifetime contributions of the author to the field of sleepwakefulness (S-W), reinterprets results of the early studies, and suggests new conclusions and perspectives. Long-term cats with mesencephalic transection show behavioral/polygraphic rapid eye movement sleep (REMS), including the typical oculopupillary behavior, even when the section is performed in kittens prior to S-W maturation. REMS can be induced as a reflex. Typical non-rapid eye movement S (NREMS) is absent and full W/arousal is present only after a precollicular section. The isolated forebrain (IF) rostral to the transection exhibits all features of W/arousal and NREMS [with electroencephalographic (EEG) spindles and delta waves], arousal to olfactory stimuli, and including the appropriate oculo-pupillary behaviors. These features also mature normally after neonatal transection. REMS is absent from the IF. After deprivation there is NREMS pressure and rebound in the IF, but the decerebrate cat only shows pressure for REMS. Most IF reactions to pharmacologic agents are within expectations, except for the tolerance/withdrawal effects of long-term morphine use which are absent. In contrast, these effects are supported by the brainstem (i.e. seen in the decerebrate cat). In cats with ablation of the telencephalon, or diencephalic cats, delta waves are absent in the thalamus. EEG thalamic spindle waves are seen triggering S for only 4-5 days after ablation. Therefore, true NREMS is absent in chronic diencephalic cats although pre-and postsomniac behaviors persist. These animals are hyperactive and show a pronounced, permanent insomnia; however, a low dose of barbiturate triggers a dramatic REMS/atypical NREMS rebound. Cats without the thalamus (athalamic cats), initially show a dissociation between behavioral hyperactivity/insomnia and the neocortical EEG, which for 15-20 days exhibits only delta and slower oscillations. Fast, low-voltage W rhythms appear later on, first during REMS, but spindle waves and S postures are absent from the start, such that these cats also display only atypical NREMS. Athalamic cats also show barbiturate-sensitive insomnia. Cats with ablation of the frontal cortices or the caudate nuclei remain permanently hyperactive. They also show a mild, but significant hyposomnia, which is permanent in afrontal cats, but lasts for about a month in acaudates. The polygraphic/ behavioral features of their S-W states remain normal. We conclude and propose that: (a) the control of the S-W system is highly complex and distributed, but is organized hierarchically in a well-defined rostro-caudal manner; the rostral-most or highest level (telencephalon), is the most functionally complex/adaptative and regulates the lower levels; the diencephalic/basal forebrain, or middle level, has a pivotal role in inducing switching between S and W and in coordinating the lowest (brainstem) and highest levels; (b) W can occur independently in both the forebrain and brainstem, but true NREMS-and REMS-generating mechanisms exis...