Local cerebral glucose utilization in the newborn macaque monkey

Impact of glucose metabolism on the developing brain

Glucose is the most important substrate for proper brain functioning and development, with an increased glucose consumption in relation to the need of creating new brain structures and connections. Therefore, alterations in glucose homeostasis will inevitably be associated with changes in the development of the Nervous System. Several studies demonstrated how the alteration of glucose homeostasis - both hyper and hypoglycemia- may interfere with the development of brain structures and cognitivity, including deficits in intelligence quotient, anomalies in learning and memory, as well as differences in the executive functions. Importantly, differences in brain structure and functionality were found after a single episode of diabetic ketoacidosis suggesting the importance of glycemic control and stressing the need of screening programs for type 1 diabetes to protect children from this dramatic condition. The exciting progresses of the neuroimaging techniques such as diffusion tensor imaging, has helped to improve the understanding of the effects, outcomes and mechanisms underlying brain changes following dysglycemia, and will lead to more insights on the physio-pathological mechanisms and related neurological consequences about hyper and hypoglycemia.

The Inferior Colliculus in Alcoholism and Beyond

Post-mortem neuropathological and in vivo neuroimaging methods have demonstrated the vulnerability of the inferior colliculus to the sequelae of thiamine deficiency as occurs in Wernicke-Korsakoff Syndrome (WKS). A rich literature in animal models ranging from mice to monkeys-including our neuroimaging studies in rats-has shown involvement of the inferior colliculi in the neural response to thiamine depletion, frequently accomplished with pyrithiamine, an inhibitor of thiamine metabolism. In uncomplicated alcoholism (i.e., absent diagnosable neurological concomitants), the literature citing involvement of the inferior colliculus is scarce, has nearly all been accomplished in preclinical models, and is predominately discussed in the context of ethanol withdrawal. Our recent work using novel, voxel-based analysis of structural Magnetic Resonance Imaging (MRI) has demonstrated significant, persistent shrinkage of the inferior colliculus using acute and chronic ethanol exposure paradigms in two strains of rats. We speculate that these consistent findings should be considered from the perspective of the inferior colliculi having a relatively high CNS metabolic rate. As such, they are especially vulnerable to hypoxic injury and may be provide a common anatomical link among a variety of disparate insults. An argument will be made that the inferior colliculi have functions, possibly related to auditory gating, necessary for awareness of the external environment. Multimodal imaging including diffusion methods to provide more accurate in vivo visualization and quantification of the inferior colliculi may clarify the roles of brain stem nuclei such as the inferior colliculi in alcoholism and other neuropathologies marked by altered metabolism.

Imaging Brain Metabolism in the Newborn

In this review, we discuss molecular brain imaging studies using positron emission tomography (PET) with 2-deoxy-2(¹⁸F)fluoro-d-glucose (FDG) in human newborns and infants, and illustrate how this technology can be applied to probe the neuropathophysiology of neonatal neurologic disorders. PET studies have been difficult to perform in sick babies because of patient transportation issues and suboptimal spatial resolution. With approval from the FDA and the institutional review board, we modified and installed the Focus 220 animal microPET scanner (Concorde Microsystems, Knoxville, TN) directly in our neonatal intensive care unit in Children's Hospital of Michigan and verified the high spatial resolution (<2 mm full-width-at-half-maximum) of this microPET. The neonatal pattern of glucose metabolism is very consistent, with the highest degree of activity in primary sensory and motor cortex, medial temporal region, thalamus, brain stem, and cerebellar vermis. Prior studies have shown that increases of glucose utilization are seen by 2 to 3 months in the parietal, temporal, cingulate, and primary visual cortex; basal ganglia; and cerebellar hemispheres. Between 6 and 8 months, lateral and inferior frontal cortex becomes more functionally active and, eventually, between 8 and 12 months, the dorsal and medial frontal regions also show a maturational increase. These findings are consistent with the physical, behavioral, and cognitive maturation of the infant. At birth, metabolic rates of glucose utilization in cortex are about 30% lower than in adults but rapidly rise such that, by 3 years, the cerebral cortical rates exceed adult rates by more than 2-fold. At around puberty, the rates for cerebral cortex begin to decline and gradually reach adult values by 16-18 years. These nonlinear changes of glucose utilization indirectly reflect programed periods of synaptic proliferation and pruning in the brain. Positron emission tomographic (PET) imaging of GABA_A receptors (using ¹¹C-flumazenil) in newborns also show a pattern very different from adults, with high binding in amygdala-hippocampus, sensory-motor cortex, thalamus, brain stem, and basal ganglia, in that order. We speculate that the early development of amygdala/hippocampus prepares the baby for bonding, attachment, and memory, and the deprivation of such experiences during a sensitive period results in malfunction of these networks and psychopathology, as has been shown in studies on severely socioemotionally deprived children. Recently developed hybrid PET/magnetic resonance (MR) scanners allow the simultaneous acquisition of PET and MR data sets with advanced applications. These devices are particularly advantageous for scanning babies and infants because of the high spatial resolution, automated coregistration of anatomical and functional images and, in the case of need for sedation, maximal data acquired in 1 session.

Trajectories of Brain Lactate and Re-visited Oxygen-Glucose Index Calculations Do Not Support Elevated Non-oxidative Metabolism of Glucose Across Childhood

Brain growth across childhood is a dynamic process associated with specific energy requirements. A disproportionately higher rate of glucose utilization (CMR_glucose) compared with oxygen consumption (CMR_O2) was documented in children's brain and suggestive of non-oxidative metabolism of glucose. Several candidate metabolic pathways may explain the CMR_glucose-CMR_O2 mismatch, and lactate production is considered a major contender. The ~33% excess CMR_glucose equals 0.18 μmol glucose/g/min and predicts lactate release of 0.36 μmol/g/min. To validate such scenario, we measured the brain lactate concentration ([Lac]) in 65 children to determine if indeed lactate accumulates and is high enough to (1) account for the glucose consumed in excess of oxygen and (2) support a high rate of lactate efflux from the young brain. Across childhood, brain [Lac] was lower than predicted, and below the range for adult brain. In addition, we re-calculated the CMR_glucose-CMR_O2 mismatch itself by using updated lumped constant values. The calculated cerebral metabolic rate of lactate indicated a net influx of 0.04 μmol/g/min, or in terms of CMR_glucose, of 0.02 μmol glucose/g/min. Accumulation of [Lac] and calculated efflux of lactate from brain are not consistent with the increase in non-oxidative metabolism of glucose. In addition, the value for the lumped constant for [¹⁸F]fluorodeoxyglucose has a high impact on calculated CMR_glucose and use of updated values alters or eliminates the CMR_glucose-CMR_O2 mismatch in developing brain. We conclude that the presently-accepted notion of non-oxidative metabolism of glucose during childhood must be revisited and deserves further investigations.

Review : Metabolic Imaging: A Window on Brain Development and Plasticity

Various biochemical and physiological processes that undergo maturational changes during human brain development can be now studied in vivo using PET. The distribution of local cerebral glucose utilization shows regional alterations in the first year of life in agreement with behavioral, neurophysiological, and anatomical changes known to occur during development of the infant. Measurement of the absolute rates of glucose utilization with PET reveals that during the major portion of the first decade, the human brain has a higher energy (glucose) demand compared with both the newborn and adult brains. With adolescence, glucose utilization rates decline to reach adult values by age 16-18 years. This nonlinear course of cerebral glucose 'metabolic' maturation is also seen in a number of animal models and coincides with the develop mental course of transient synaptic exuberance associated with enhanced brain plasticity and efficient learn ing. Evidence of brain reorganization detected with PET is discussed in children with unilateral brain injury and early sensory deprivation. NEUROSCIENTIST 5:29-40, 1999

Acute and chronic vascular responses to experimental focal arterial stroke in the neonate rat

The presence of active developmental angiogenesis and vascular outgrowth in the postnatal brain may differentially affect vascular responses to stroke in newborns and adults, but very little is known about the dynamics of vascular injury and re-growth after stroke during the neonatal period. In this study we used a clinically relevant animal model of ischemic arterial stroke in neonate rats, a transient middle cerebral artery occlusion (MCAO) in postnatal day 7 (P7), to characterize the effects of injury on vascular density and angiogenesis from acute through the chronic phase. A marked vessel degeneration and suppressed endothelial cell proliferation occur in the ischemic regions early after neonatal stroke. In contrast to what has been described in adult animals, endothelial cell proliferation and vascular density are not increased in the peri-ischemic regions during the first week after MCAO in neonates. By two weeks after injury, endothelial cell proliferation is increased in the cortical peri-ischemic region but these changes are not accompanied by an increased vascular density. Suppressed angiogenesis in injured postnatal brain that we report may limit recovery after neonatal stroke. Thus, enhancement of angiogenesis after neonatal stroke may be a promising strategy for the long-term recovery of the affected newborns.

Molecular and physiological responses to juvenile traumatic brain injury: focus on growth and metabolism

Traumatic brain injury (TBI), one of the most frequent causes of neurologic and neurobehavioral morbidity in the pediatric population, can result in lifelong challenges not only for patients, but also for their families. Survivors of a brain injury experienced during childhood - when the brain is undergoing a period of rapid development - frequently experience unique challenges as the consequences of their injuries are overlaid on normal developmental changes. Experimental studies have significantly advanced our understanding of the mechanisms and underlying molecular underpinnings of the injury response and recovery process following a TBI in the developing brain. In this paper, normal and TBI-related alterations in growth, development and metabolism are comprehensively reviewed in the postweanling/juvenile age range in the rat (postnatal days 21-60). As part of this review, TBI-related changes in gene expression are presented, with a focus on the injury-induced alterations related to cerebral growth and metabolism, and discussed in the context of existing literature related to physiological and behavioral responses to experimental TBI. Increasing evidence from the existing literature and from our own gene microarray data indicates that molecular responses related to growth, development and metabolism may play a particularly important role in the injury response and the recovery trajectory following developmental TBI. While gene expression analysis shows many of these changes occur at the level of transcription, a comprehensive review of other studies suggests that the control of metabolic substrates may preferentially be regulated through changes in transporters and enzymatic activity. The interrelation between cellular metabolism and activity-dependent neuroplasticity shows great promise as an area for future study for an optimal translation of experimental data to clinical TBI, with the ultimate goal of guiding therapeutic interventions.

PET in the Assessment of Pediatric Brain Development and Developmental Disorders

This article discusses and reviews the role and contribution of PET in understanding the structural and functional changes that occur during brain development, and how these changes relate to behavioral and cognitive development in the infant and child. Data regarding various aspects of brain development, such as glucose metabolism, protein synthesis, and maturation and development of neurotransmitter systems will help in understanding the pathogenesis and neurologic basis of various developmental and neurologic disorders. This may help in following disease evolution and progression, planning and development of various therapeutic interventions, timing these interventions and monitoring their responses, and rendering long-term prognostication.

Multigenic control of thyroid hormone functions in the nervous system

Thyroid hormone (TH) has a remarkable range of actions in the development and function of the nervous system. A multigenic picture is emerging of the mechanisms that specify these diverse functions in target tissues. Distinct responses are mediated by alpha and beta isoforms of TH receptor which act as ligand-regulated transcription factors. Receptor activity can be regulated at several levels including that of uptake of TH ligand and the activation or inactivation of ligand by deiodinase enzymes in target tissues. Processes under the control of TH range from learning and anxiety-like behaviour to sensory function. At the cellular level, TH controls events as diverse as axonal outgrowth, hippocampal synaptic activity and the patterning of opsin photopigments necessary for colour vision. Overall, TH coordinates this variety of events in both central and sensory systems to promote the function of the nervous system as a complete entity.

Energy metabolism in mammalian brain during development

Production of energy for the maintenance of ionic disequilibria necessary for generation and transmission of nerve impulses is one of the primary functions of the brain. This review attempts to link the plethora of information on the maturation of the central nervous system with the ontogeny of ATP metabolism, placing special emphasis on variations that occur during development in different brain regions and across the mammalian species. It correlates morphological events and markers with biochemical changes in activities of enzymes and pathways that participate in the production of ATP. The paper also evaluates alterations in energy levels as a function of age and, based on the tenet that ATP synthesis and utilization cannot be considered in isolation, investigates maturational profiles of the key processes that utilize energy. Finally, an attempt is made to assess the relevance of currently available animal models to improvement of our understanding of the etiopathology of various disease states in the human infant. This is deemed essential for the development and testing of novel strategies for prevention and treatment of several severe neurological deficits.

The frontal lobes and theory of mind: Developmental concepts from adult focal lesion research

The primary objective in this paper is to present a framework to understand the structure of consciousness. We argue that consciousness has been difficult to define because there are different kinds of consciousness, hierarchically organized, which need to be differentiated. Our framework is based on evidence from adult focal lesion research. The different types of consciousness are associated with distinct brain regions, with the higher levels of consciousness related to self-awareness and theory of mind (both facets of consciousness), with an emphasis on the role of the frontal lobes. The secondary objective is to use this structure to suggest hypotheses about the potential effect of frontal dysfunction at various developmental stages, and including both congenital and acquired brain injury.

Effect of Different Thyroid States on Mitochondrial Porin Synthesis and Hexokinase Activity in Developing Rabbit Brain

Voltage-dependent anion-selective channel proteins (VDACs) are pore-forming proteins found in the outer mitochondrial membrane of all eukaryotes and in brain postsynaptic membranes. VDACs regulate anion fluxes of a series of metabolites including ATP, thus regulating mitochondrial metabolic functions. Hexokinase binds to porin. The mitochondrially bound hexokinase can greatly increase the rate of aerobic glycolysis. The activities of hexokinase and protein levels of mitochondrial porin were determined in brains of hypothyroid rabbits and in hypothyroid rabbits administered with thyroxine. Proteins were separated by electrophoresis, and the proteins of interest were quantified. Western blotting analysis revealed a significant decrease (approximately 50%) in the relative amount of porin in the hypothyroid compared with euthyroid rabbits. The changes in the developmental pattern of hexokinase activity in the brain of hypothyroid rabbits and the effect of T(4) on this enzyme activity have been investigated. Hypothyroid rabbits showed lower activity than their corresponding age-matched normal neonates. Administration of thyroxine to the hypothyroid neonates at birth abolished the effects of methimazole [1-methyl-2-mercaptoimidazole (MMI)]. These findings apparently indicate that the synthesis of the pore-forming protein and the hexokinase enzymes are under thyroid control during the fetal and the early postnatal period.

Local brain functional activity following early deprivation: a study of postinstitutionalized Romanian orphans

Early global deprivation of institutionalized children may result in persistent specific cognitive and behavioral deficits. In order to examine brain dysfunction underlying these deficits, we have applied positron emission tomography using 2-deoxy-2-[(18)F]fluoro-D-glucose in 10 children (6 males, 4 females, mean age 8.8 years) adopted from Romanian orphanages. Using statistical parametric mapping (SPM), the pattern of brain glucose metabolism in the orphans was compared to the patterns obtained from two control groups: (i) a group of 17 normal adults (9 males, 8 females, mean age 27.6 years) and (ii) a group of 7 children (5 males and 2 females, mean age 10.7 years) with medically refractory focal epilepsy, but normal glucose metabolism pattern in the contralateral hemisphere. Consistent with previous studies of children adopted from Romanian orphanages, neuropsychological assessment of Romanian orphans in the present study showed mild neurocognitive impairment, impulsivity, and attention and social deficits. Comparing the normalized glucose metabolic rates to those of normal adults, the Romanian orphans showed significantly decreased metabolism bilaterally in the orbital frontal gyrus, the infralimbic prefrontal cortex, the medial temporal structures (amygdala and head of hippocampus), the lateral temporal cortex, and the brain stem. These findings were confirmed using a region-of-interest approach. SPM analysis showed significantly decreased glucose metabolism in the same brain regions comparing the orphans to the nonepileptic hemisphere of the childhood epilepsy controls. Dysfunction of these brain regions may result from the stress of early global deprivation and may be involved in the long-term cognitive and behavioral deficits displayed by some Romanian orphans.

Brain glucose utilization in mice with a targeted mutation in the thyroid hormone alpha or beta receptor gene

Brain glucose utilization is markedly depressed in adult rats made cretinous after birth. To ascertain which subtype of thyroid hormone (TH) receptors, TRalpha1 or TRbeta, is involved in the regulation of glucose utilization during brain development, we used the 2-[(14)C]deoxyglucose method in mice with a mutation in either their TRalpha or TRbeta gene. A C insertion produced a frameshift mutation in their carboxyl terminus. These mutants lacked TH binding and transactivation activities and exhibited potent dominant negative activity. Glucose utilization in the homozygous TRbetaPV mutant mice and their wild-type siblings was almost identical in 19 brain regions, whereas it was markedly reduced in all brain regions of the heterozygous TRalpha1PV mice. These suggest that the alpha1 receptor mediates the TH effects in brain. Inasmuch as local cerebral glucose utilization is closely related to local synaptic activity, we also examined which thyroid hormone receptor is involved in the expression of synaptotagmin-related gene 1 (Srg1), a TH-positively regulated gene involved in the formation and function of synapses [Thompson, C. C. (1996) J. Neurosci. 16, 7832-7840]. Northern analysis showed that Srg1 expression was markedly reduced in the cerebellum of TRalpha(PV/+) mice but not TRbeta(PV/PV) mice. These results show that the same receptor, TRalpha1, is involved in the regulation by TH of both glucose utilization and Srg1 expression.

Neonatal auditory activation detected by functional magnetic resonance imaging

The objective of this study was to detect auditory cortical activation in non-sedated neonates employing functional magnetic resonance imaging (fMRI). Using echo-planar functional brain imaging, subjects were presented with a frequency-modulated pure tone; the BOLD signal response was mapped in 5 mm-thick slices running parallel to the superior temporal gyrus. Twenty healthy neonates (13 term, 7 preterm) at term and 4 adult control subjects. Blood oxygen level-dependent (BOLD) signal in response to auditory stimulus was detected in all 4 adults and in 14 of the 20 neonates. FMRI studies of adult subjects demonstrated increased signal in the superior temporal regions during auditory stimulation. In contrast, signal decreases were detected during auditory stimulation in 9 of 14 newborns with BOLD response. fMRI can be used to detect brain activation with auditory stimulation in human infants.

Dynamic changes in cerebral glucose metabolism in conscious infant monkeys during the first year of life as measured by positron emission tomography

Recently, advances in spatial resolution have provided the opportunity to utilize positron emission tomography (PET) to examine local cerebral metabolic rates for glucose (lCMR(glc)) in large animals noninvasively, thereby allowing repeated lCMR(glc) measurements in the same animal. Previous studies have attempted to describe the ontogeny of cerebral glucose metabolism in anesthetized nonhuman primates using [18F]fluorodeoxyglucose (FDG) and PET. However, the use of sedation during the tracer uptake period may influence lCMR(glc). This study was conducted to describe lCMR(glc) in conscious infant vervet monkeys (Cercopithecus aethiops sabaeus) during the first year of life utilizing FDG-PET. Cross-sectional studies (n=23) displayed lowest and highest lCMR(glc) in all structures at the 2-3 and 8-9 month age groups, respectively. The metabolic pattern suggested an increase in lCMR(glc) values between 2 and 8 months of age with decreased metabolism observed at 10-12 months of age in all regions. Peak lCMR(glc) values at 8 months were an average of 84+/-24% higher than values seen at the youngest age examined quantitatively (2-3 months). The regions of greatest and smallest increases in lCMR(glc) at 8 months were the cerebellar hemispheres (90%) and the thalamus (39%), respectively. Longitudinal analysis in 4 animals supported this developmental pattern, demonstrating the ability to detect changes in cerebral glucose metabolism within animals and the potential for FDG-PET in nonhuman primate models of brain maturation. By determining the normative profile of lCMR(glc) during development in monkeys, future application of FDG-PET will provide the opportunity to longitudinally assess the effects of environmental or pharmacological intervention on the immature brain.

Interictal hyperperfusion observed in infants with cortical dysgenesis

We investigated increases of interictal regional cerebral blood flow (rCBF) in patients with intractable epilepsy caused by cortical dysgenesis. Using single photon emission computed tomography, we measured interictal rCBF of epileptic foci in 24 patients with cortical dysgenesis who achieved Engel Class I or II outcomes at least 1 year after surgical intervention. The patients included 14 males and ten females, ranging in age from 2 months to 34 years (mean 6 years and 5 months). In the interictal period, dysplastic areas showed hyperperfusion in four patients (17%), hypoperfusion in 15 (62%), and isoperfusion patterns in five (21%). Interictal hyperperfusion was found in four infants aged 3-4 months; three with focal cortical dysplasia and one with hemimegalencephaly. Our results suggest that interictal hyperperfusion may indicate the presence of an active epileptic focus in infants with cortical dysgenesis, but not in older children or adults with the same disorder. Given the risk of misinterpreting the normal side as hypoperfused, the phenomenon of interictal hyperperfusion in the epileptogenic area should be taken into account when diagnosing pediatric epilepsy caused by cortical dysgenesis.

Cerebral blood oxygenation changes induced by auditory stimulation in newborn infants measured by near infrared spectroscopy

Recent neuronal activation studies on newborns using functional MRI or near infrared spectroscopy (NIRS) have suggested that the increase in O2 consumption accompanying neuronal activation exceeds the increase in O2 delivery in the visual cortex during photic stimulation. In the present study, we evaluated the cerebral blood oxygenation (CBO) changes induced by auditory stimulation in the frontal lobe of newborns using NIRS. We studied 28 newborns; the postnatal age at CBO measurements was 3.1+/-0.3 days (mean+/-S.E.M.). We measured concentration changes of deoxyhemoglobin (Deoxy-Hb), oxyhemoglobin (Oxy-Hb), and total hemoglobin (Total-Hb) induced by auditory (music) stimulation in the bilateral frontal lobes of the newborns. Twenty-six (92.9%) out of 28 subjects showed increases of Oxy-Hb and Total-Hb during the stimulation. In these subjects, 17 (60.7%) subjects showed an increase of Deoxy-Hb associated with increases of Oxy-Hb and Total-Hb, while nine (32.1%) subjects showed a decrease of Deoxy-Hb. Although the direction of the Deoxy-Hb differed, these two groups did not differ for Oxy-Hb and Total-Hb (P > 0.05). Two (7.1%) subjects showed other changes. The frontal lobe of newborns shows CBO responses similar to those observed in the visual cortex, specifically neuronal activation causes an increase of Deoxy-Hb associated with increases of Oxy-Hb and Total-Hb. These results support the hypothesis that increments in O2 consumption exceed increments in O2 delivery during neuronal activity in newborns.

Application of positron emission tomography to determine cerebral glucose utilization in conscious infant monkeys

Cerebral glucose metabolism has been used as a marker of cerebral maturation and neuroplasticity. In studies addressing these issues in young non-human primates, investigators have used positron emission tomography (PET) and [18F]2-fluoro-2-deoxy-D-glucose (FDG) to calculate local cerebral metabolic rates of glucose (1CMRG1c). Unfortunately, these values were influenced by anesthesia. In order to avoid this confounding factor, we have established a method that permits reliable measurements in young conscious vervet monkeys using FDG-PET. Immature animals remained in a conscious, resting state during the initial 42 min of FDG uptake as they were allowed to cling to their anesthetized mothers. After FDG uptake, animals were anesthetized and placed in the PET scanner with data acquisition beginning at 60 min post-FDG injection. FDG image sets consisted of 30 planes separated by 1.69 mm, parameters sufficient to image the entire monkey brain. Our method of region-of-interest (ROI) analysis was assessed within and between raters and demonstrated high reliability (P < 0.001). To illustrate that our method was sensitive to developmental changes in cerebral glucose metabolism, quantitative studies of young conscious monkeys revealed that infant monkeys 6-8 months of age exhibited significantly higher 1CMRG1c values (P < 0.05) in all regions examined, except sensorimotor cortex and thalamus, compared to monkeys younger than 4 months of age. This method provided high resolution images and 1CMRG1c values that were reliable within age group. These results support the application of FDG-PET to investigate questions related to cerebral glucose metabolism in young conscious non-human primates.

Impact of cognitive rehabilitation therapy on neuropsychological impairments as measured by brain perfusion SPECT: a longitudinal study

Three patients, with known brain injury and neuropsychological impairments, are followed through an individualized cognitive rehabilitation programme and post discharge from the treatment programme. Single Photon Emission Computed Tomography (SPECT) of the brain was employed to evaluate resting relative cerebral blood flow (rCBF) during the process of recovery from brain injury. All patients experienced significant improvements on measures of neuropsychological functioning and improvements in rCBF during this longitudinal study. The specific changes in rCBF appear to be related to the location of the patient's brain injury and strategies particular to cognitive rehabilitation therapy. Continued improvements in rCBF, functional abilities, and cognitive skills were documented in these three cases up to 45 months post brain injury.

Age at onset and neuropsychological function in frontal lobe epilepsy

PURPOSE

Previous studies into the cognitive consequences of frontal lobe epileptic dysfunction may have proved inconclusive, due to a factor not commonly accounted for: Damage or disturbance during different epochs of development may give rise to different levels of neuropsychological dysfunction. In this study, we investigated the influence of age at onset on cognitive performance in a group of subjects with frontal lobe epilepsy (FLE).

METHODS

Seventy-four subjects (42 with left, and 32 with right) FLE were classified into early (0-6 years), intermediate (7-11 years) or late onset (> or =12 years) and their performance recorded on a battery of measures assessing both executive and motor skills.

RESULTS

On the measures of executive functioning, no consistent pattern emerged, whereas on the measures of motor skill, the results suggested that a right-sided early onset (i.e., 0-6 years) did not impair performance compared to a later lesion within the same hemisphere. Furthermore, this sparing of performance was not observed within the left hemisphere.

CONCLUSIONS

Overall, the results suggest that individuals with differing ages of epilepsy onset will be differentially impaired on certain cognitive tasks. Several tentative ramifications of these results are suggested.

Cerebral metabolic rate for glucose during the first six months of life: an FDG positron emission tomography study

AIM

To measure the local cerebral metabolic rate for glucose (LCMRGlc) in neonatal brains during maturation using positron emission tomography (PET) and 2-[18F]fluoro-2-deoxy-D-glucose (FDG).

METHODS

Twenty infants were studied using PET during the neonatal period. The postconceptional age ranged from 32.7 to 60.3 weeks. All infants had normal neurodevelopment and were normoglycaemic. The development of the infants was carefully evaluated (follow up 12-36 months) clinically, and by using a method based on Gesell Amatruda's developmental diagnosis. LCMRGlc was quantitated using PET derived from FDG kinetics and calculated in the whole brain and for regional brain structures.

RESULTS

LCMRGlc for various cortical brain regions and the basal ganglia was low at birth (from 4 to 16 mumol/100 g/minute). In infants 2 months of age and younger LCMRGlc was highest in the sensorimotor cortex, thalamus, and brain stem. By 5 months, LCMRGlc had increased in the frontal, parietal, temporal, occipital and cerebellar cortical regions. In general, the whole brain LCMRGlc correlated with postconceptional age (r = 0.90; P < 0.001). The change in the glucose metabolic pattern observed in the neonatal brain reflects the functional maturation of these brain regions.

CONCLUSION

These findings show that LCMRGlc in infants increases with maturation. Accordingly, when LCMRGlc is measured during infancy, the postconceptional age has to be taken into account when interpretating the results.

Hypoxic-ischemic encephalopathy in areas of primary myelination: a neuroimaging and PET study

The stage of regional structural and biochemical development of the central nervous system appears as a critical factor determining the distribution of hypoxic-ischemic lesions during the perinatal period. We describe the brain lesions in 12 patients who suffered hypoxia-ischemia during the perinatal period. The gestational age ranged from 35 to 42 weeks and the age at death from 2 to 16 weeks. There is one patient alive at age 18 years and a second patient at age 1 year. The cerebral cortical damage is mainly restricted to areas of primary myelination and adjacent subcortical white matter. In addition, there is thalamic, basal ganglia, brainstem, and spinal cord damage. It is postulated that selective damage occurs in those areas which at the moment of the hypoxic-ischemic insult had achieved higher rates of oxygen-glucose utilization. This hypothesis is supported by studies utilizing positron emission tomography which indicates that glucose utilization in the normal human neonatal brain follows a phylogenetic order. Regions that achieved higher levels of glucose consumption are those that suffered the brunt of the damage in our term neonates.

Changes in regional cytochrome oxidase activity in the fetal, newborn and adult ovine brainstem

Metabolic activity of specific brain regions (e.g. brainstem respiratory centers) may increase during the physiologic adaptations at birth. Since regional activity of cytochrome oxidase is correlated with the level of oxidative metabolism, cytochrome oxidase histochemistry was used to investigate whether there are sustained changes in metabolic activity within specific nuclei of the ovine brainstem during the perinatal period and whether further changes occur in the adult. Histochemistry was performed on 10-microns-thick frozen sections of the perinatal (130 d fetus, 140 d fetus, 8 h newborn and 10 d newborn) and adult ovine brainstem (n = 3 at each age). Computer-assisted image analysis was performed on 20 brainstem regions. A general decreasing trend, interrupted by a tendency for a transient increase at 8 h after birth was observed in most regions analyzed. Statistically significant decreases (P < 0.05) in cytochrome oxidase levels between the perinatal age groups and the adult were found in 7 brainstem nuclei studied: ambiguus, cuneate, inferior olivary, reticularis lateralis, spinal trigeminal, parabrachial and superior olivary nuclei. Within the perinatal period, the nucleus gracilis was the only region to show statistically significant decreases in 140 d fetus and 8 h newborns in all nuclei analyzed, but this change was not statistically significant (P > 0.1). These results indicate that the dramatic changes in physiology and environment at birth do not result in a significant change in the metabolic capacity of brainstem nuclei in the immediate perinatal period. However, more gradual developmental changes are observed in specific brainstem nuclei suggesting a decrease in neuronal activity occurs in these areas during development in the sheep.

Anaerobic glycolysis preceding white-matter destruction in experimental neonatal hydrocephalus

The metabolic changes in neonatal hydrocephalus that lead to permanent brain injury are not clearly defined, nor is the extent to which these changes can be prevented by a cerebrospinal fluid shunt. To clarify these processes, cerebral glucose utilization was examined using [14C]2-deoxyglucose autoradiography in 1-month-old kittens, kaolin-induced hydrocephalic littermates, and hydrocephalic kittens in which a ventriculoperitoneal shunt had been inserted 10 days after kaolin injection. The hydrocephalic kittens showed thinning of the cerebral mantle and an anterior-to-posterior gradient of enlargement of the ventricular system, with a ventricle:brain ratio of 24% for the frontal and 35% for the occipital horns compared with control (< 0.5%) and shunted (< 5%) animals. White matter in hydrocephalic animals was edematous. Myelination was delayed in the periventricular region and in the cores of the cerebral gyri. Glucose utilization in hydrocephalic and shunted animals was unchanged from control animals in all gray-matter regions examined. However, in hydrocephalic animals, the frontal white matter exhibited a significant increase in glucose utilization (25 mumol.100 gm-1.min-1) in the cores of gyri compared with normal surrounding white-matter values (14.8 mumol.100 gm-1.min-1). Very low values (mean 4 mumol.100 gm-1.min-1) were found in areas corresponding to severe white-matter edema, and these areas were surrounded by a halo of increased activity (24 mumol.100 gm-1.min-1). In contrast, cytochrome oxidase activity in white matter was homogeneous. Shunting resulted in restoration of the cerebral mantle thickness, a return to normal levels of glucose utilization in the white matter, and an improvement in myelination. It is suggested that the areas of increased glucose utilization seen in the white matter represent anaerobic glycolysis which, if untreated, progresses to infarction. The pattern of this increased glucose utilization matches that of expected myelination and, during this period of high energy demand, white matter may be susceptible to the hypoperfusion associated with hydrocephalus.

Developmental expression of GLUT1 and GLUT3 glucose transporters in rat brain

Two glucose transport proteins, GLUT1 and GLUT3, have been detected in brain. GLUT1 is concentrated in the endothelial cells of the blood-brain barrier and may be present in neurons and glia; GLUT3 is probably the major neuronal glucose transporter. Of the few studies of glucose transport in the immature brain, none has quantified GLUT3. This study used membrane isolation and immunoblotting techniques to examine the developmental expression of GLUT1 and GLUT3 in four forebrain regions, cerebral microvessels, and choroid plexus, from rats 1-30 days postnatally as compared with adults. The GLUT1 level in whole brain samples was low for 14 days, doubled by 21 days, and doubled again to attain adult levels by 30 days; there was no regional variation. The GLUT3 level in these samples was low during the first postnatal week, increased steadily to adult levels by 21-30 days, and demonstrated regional specificity. The concentration of GLUT1 in microvessels increased steadily after the first postnatal week; the GLUT1 level in choroid plexus was high at birth, decreased at 1 week, and then returned to near fetal levels. GLUT3 was not found in microvessels or choroid plexus. This study indicates that both GLUT1 and GLUT3 are developmentally regulated in rat brain: GLUT1 appears to relate to the nutrient supply and overall growth of the brain, whereas GLUT3 more closely relates to functional activity and neuronal maturation.

A quantitative dendritic analysis of Wernicke's area in humans. II. Gender, hemispheric, and environmental factors

This quantitative Golgi study extends our investigation of relationships between cortical dendrite systems in humans and higher cognitive functions. Here we examine the relationship between the basilar dendrites of supragranular pyramidal cells in Wernicke's area and selected intrinsic (i.e., gender and hemisphere) and extrinsic (i.e., education and personal history) variables. Tissue was obtained from 20 neurologically normal right-handers: 10 males (Mage = 52.2) and 10 females (Mage = 47.8). Several independent variables were investigated: GENDER (male, female), HEMISPHERE (left, right), and EDUCATION (less than high school, high school, and university). These were evaluated according to Total Dendritic Length, Mean Dendritic Length, and Dendritic Segment Count. A distinction was made between proximal (1st, 2nd, and 3rd order) and ontogenetically later developing distal (4th order and above) branches. There was significant interindividual variation in dendritic measurements, which roughly reflected individuals' personal backgrounds. Females exhibited slightly greater dendritic values and variability than males across the age range examined. On the whole, the left hemisphere maintained a slight advantage over the right hemisphere for all dendritic measures when all subjects were pooled, but these differences were not in a consistent direction across individuals. Education had a consistent and substantial effect such that dendritic measures increased as educational levels increased. Dendritic differences between independent variable levels were most clearly illustrated in the total dendritic length of 3rd and 4th order branches. Distal dendritic branches appeared to exhibit greater epigenetic flexibility than proximal dendrites. The present findings concur with environmental enrichment research results in animals and suggest that dendritic systems in humans function as a sensitive indicator of an individual's (a)vocational activities.

Biological and psychological development of executive functions

The purpose of this overview is to provide a background for understanding the relation between the biological maturation of the frontal lobes and the development of the psychological concept of executive functions. In the first section, an interactive hierarchical feedback model is presented as a heuristic way of conceptualizing the relationship of the frontal lobes and executive functions to other brain regions and abilities. The following two sections present a synopsis of research on biological maturation and the psychological development of executive functions.

Ontogeny of cholecystokinin-immunoreactive structures in the primate cerebral neocortex

Distribution of cholecystokinin (CCK)-immunoreactive structures was studied in various neocortical areas of macaque monkeys during prenatal and postnatal development. The largest number of CCK-immunoreactive cells was observed at embryonic day 140, and subsequently they decreased in number until postnatal day 60. A few cells which were presumably degenerated neurons were observed during postnatal development. A higher density of CCK-immunoreactive cells was observed in the supragranular layers (layers II and III) than in the infragranular layers (layers V and VI). The number of CCK-immunoreactive cells was larger and changed more conspicuously in the association areas than in the other areas during development. In contrast, in the occipital area, the number of such cells was small and changed only a little. These findings suggest that CCK may be involved in the development and special function of each neocortical areas of the primate.

Synchronized overproduction of neurotransmitter receptors in diverse regions of the primate cerebral cortex

A remarkable diversity of neurotransmitter receptors develops concurrently in disparate areas of the primate cerebral cortex. The density of dopaminergic, adrenergic, serotonergic, cholinergic, and GABAergic receptors (where GABA is gamma-aminobutyric acid) in rhesus monkey reaches a maximum level between 2 and 4 months of age and then declines gradually to adult levels in all layers of sensory, motor, and association regions. The synchronized development of neurotransmitter receptors in diverse layers and regions of the neocortex occurs pari passu with synaptogenesis, demonstrating unusual coordination of biochemical and structural maturation and supporting the hypothesis that the entire cerebral cortex matures as an integrated network, rather than as a system-by-system cascade.

Regional myocardial glucose utilization by developing fetal and maternal hearts

Regional glucose utilization of the developing fetal feline heart was assessed during three stages of gestation and compared with the maternal heart and non-pregnant controls. The specific aims were to determine: 1) if glucose utilization by the whole heart changes from early to late gestation; 2) if there are differences in glucose utilization by specific regions of the heart; 3) if these regional differences in glucose utilization are consistent throughout gestation. Regional myocardial glucose utilization was measured using the [14C] 2-deoxyglucose high spatial resolution autoradiographic technique. Eleven fetal and 16 adult hearts were studied. Two of the fetuses were at 49 days of gestation, three were at 35 days, and six were at 25 days of gestation. This was the first study to assess regional myocardial glucose utilization in the developing fetus. Glucose utilization by the fetal heart was greater than that seen in the normal control adult or maternal heart, and was highest during early gestation. The posterior wall of the left ventricle had glucose utilization twice that measured for the anterior wall. Other regions were not significantly different. This information indicates that availability of glucose to the fetus is important for normal cardiac metabolism and development.

Metabolic maturation of the brain: a study of local cerebral glucose utilization in the developing cat

Previously, using positron emission tomography (PET), we showed that local cerebral metabolic rates for glucose (lCMRglc) in children undergo dynamic maturational 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 kittens at various stages of postnatal development and in adult cats using quantitative [14C]2-deoxyglucose autoradiography. In the kitten, very low lCMRglc levels (0.14 to 0.53 mumol min-1 g-1) were seen during the first 15 days of life, with phylogenetically older brain regions being generally more metabolically mature than newer structures. After 15 days of age, many brain regions (particularly 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 was observed, but this was followed by a second, larger peak occurring at about 180 days, when sexual maturation occurs in the cat. Only after 180 days did lCMRglc decrease to reach final adult values (0.21 to 2.04 mumol min-1 g-1). In general, there was good correlation between the metabolic maturation of various neuroanatomical 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 developmental plasticity, the "critical period" corresponded to that portion of the lCMRglc maturational curve surrounding the 60-day metabolic peak. These normal maturational lCMRglc data will serve as baseline values with which to compare anatomical and metabolic plasticity changes induced by age-related lesions in the cat.

Consequences of chronic phenobarbital treatment on local cerebral glucose utilization in the developing rat

The influence of a chronic phenobarbital (PhB) treatment on postnatal evolution of local cerebral metabolic rates for glucose (LCMRglc) was studied in 58 cerebral structures of freely moving rats. The animals received a daily subcutaneous injection of PhB at a dose of 50 mg/kg between days 2 and 35 or an equivalent volume of saline for controls and were studied at 5 postnatal stages, i.e. 10, 14, 17, 21 and 35 days, and at the adult stage. Body and brain weights were both reduced by 6-21% over the whole period studied. PhB exposure induced significant decreases in LCMRglc during the period of pharmacological treatment, i.e. until 35 days, except at the stage of 17 days as well as long-term reductions in LCMRglc of adult rats in 36 out of the 58 brain regions studied. These decreases affected all systems studied, sensory systems as well as limbic, hypothalamic, motor and white matter areas. In addition to a growth retardation, PhB also seemed to be able to induce a delay in the acquisition of auditory function which matures early during postnatal life. The long-term deficits in cerebral energy metabolism due to PhB in the adult rat also confirm the behavioral deficits which have been shown previously after early PhB exposure.

Deoxyglucose lumped constant estimated in a transplanted rat astrocytic glioma by the hexose utilization index

The lumped constant (LC) for calculating the regional glucose (glc) metabolic rate by the deoxyglucose (DG) method was estimated in a transplanted rat glioma and normal rat brain. First, the hexose utilization index (HUI) was measured at 1.5, 3.0, and 4.5 min in right hemisphere glioma implants and uninvolved contralateral hemisphere following bolus intravenous injections of [3H]DG and [14C]glucose. At these times, the glioma HUI values were 0.639, 0.732, and 0.712, respectively, and the coordinate left hemisphere values were 0.432, 0.449, and 0.418. Second, the volumes of distribution of DG and glucose were determined to be 0.436 and 0.235 in glioma implants and 0.402 and 0.237 in left hemisphere, respectively. Third, following simultaneous intracarotid injections of [3H]DG and [14C]glucose, the ratio K1/K1 was 1.1 in glioma grafts and 1.3 in left hemisphere. With these values for HUI, volume of distribution, and K1 ratio, the LC in this rat glioma was estimated to be 2.1 times higher than the left hemisphere LC (p less than 0.02). These results suggest that measurement of brain tumor CMRglc using a normal brain LC may significantly overestimate the true tumor CMRglc.

Local cerebral glucose utilization during status epilepticus in newborn primates

The effect of bicuculline-induced status epilepticus (SE) on local cerebral metabolic rates for glucose (LCMRglc) was studied in 2-wk-old ketamine-anesthetized marmoset monkeys, using the 2-[14C]-deoxy-D-glucose autoradiographical technique. To estimate LCMRglc in cerebral cortex and thalamus during SE, the lumped constant (LC) for 2-deoxy-D-glucose (2-DG) and the rate constants for 2-DG and glucose were calculated for these regions. The control LC was 0.43 in frontoparietal cortex, 0.51 in temporal cortex, and 0.50 in thalamus; it increased to 1.07 in frontoparietal cortex, 1.13 in temporal cortex, and 1.25 in thalamus after 30 min of seizures. With control LC values, LCMRglc in frontoparietal cortex, temporal cortex, and dorsomedial thalamus appeared to increase four to sixfold. With seizure LC values, LCMRglc increased 1.5- to 2-fold and only in cortex. During 45-min seizures, LCMRglc in cortex and thalamus probably increases 4- to 6-fold initially and later falls to the 1.5- to 2-fold level as tissue glucose concentrations decrease. Together with our previous results demonstrating depletion of high-energy phosphates and glucose in these regions, the data suggest that energy demands exceed glucose supply. The long-term effects of these metabolic changes on the developing brain remain to be determined.

Fetal glucose utilization using maternal plasma glucose and scintillation values

The hypothesis tested was that measurement of fetal plasma values for glucose and scintillation counts results in statistically the same calculated integrals and consequent values for cerebral glucose utilization as would be obtained if the maternal plasma values were used alone with the quantitative 2-[14C]deoxyglucose technique of Sokoloff et al. In 4 pregnant rabbits anesthetized with ketamine, a single bolus of 2-[14C]deoxyglucose was injected i.v. Fourteen periodic blood samples were taken from the adult rabbit and a single fetal placental unit simultaneously. The plasma integrals of the Sokoloff equation were calculated and compared statistically. The results demonstrate that there is no statistical difference between the maternal and fetal plasma integrals and therefore the fetal plasma values do not need to be measured for accurate measurements of fetal cerebral glucose utilization to be made using the 2-[14C]deoxyglucose technique of Sokoloff.

Regional variations in human newborn cerebral blood flow

Regional differences in the local cerebral metabolic rate of glucose have been reported in newborn infants. This study was performed to determine if comparable differences exist in neonatal regional cerebral blood flow (rCBF). In 21 infants, rCBF was measured with a modified xenon 133 (133Xe) clearance technique by means of eight extracranial detectors positioned over four homologous regions (frontal, parietal, temporal, and occipital). The rCBF was lowest in the frontal region, higher in the parietal region, and highest in the temporal and occipital regions. Regional differences in rCBF may be caused by regional differences in brain development and function.

Projections between the interpeduncular nucleus and basal forebrain in the rat as demonstrated by the anterograde and retrograde transport of WGA-HRP

The distribution of anterogradely-labeled fibers and retrogradely-labeled cell bodies in the interpeduncular nucleus (IPN) was mapped after injections of wheat-germ agglutinin conjugated to horseradish peroxidase (WGA-HRP) into various structures of the basal forebrain in adult rats. WGA-HRP injections into the medial septum/vertical limb of the diagonal band nucleus resulted in: 1) dense anterograde labeling in the rostral, intermediate, and central subnuclei; and 2) retrograde labeling in the apical and central subnuclei. Injections into the lateral septum produced: 1) no anterograde labeling in the IPN; and 2) retrograde labeling which was dense in the apical subnucleus, moderate in the central and lateral subnuclei, and light in the intermediate subnucleus. Injections into the horizontal limb of the diagonal band nucleus resulted in: 1) anterograde labeling which was most pronounced in the central, rostral, and intermediate subnuclei; and 2) retrograde labeling which was strongest in the apical, central, and lateral subnuclei. After injections into the substantia innominata-magnocellular preoptic nucleus, there was: 1) dense anterograde labeling in the rostral and central subnuclei and moderate anterograde labeling in the intermediate subnucleus; and 2) essentially no retrograde cell labeling in the IPN. These findings demonstrate that the IPN receives inputs from, and projects to specific portions of the basal forebrain. The rostral and central subnuclei are the primary targets of inputs from the basal forebrain to the IPN, and the apical subnucleus is the primary source of IPN projections to the basal forebrain.

Positron emission tomography study of human brain functional development

From over 100 children studied with 2-deoxy-2[18F]fluoro-D-glucose and positron emission tomography we selected 29 children (aged 5 days to 15.1 years) who had suffered transient neurological events not significantly affecting normal neurodevelopment. These 29 children were reasonably representative of normal children and provided an otherwise unobtainable population in which to study developmental changes in local cerebral metabolic rates for glucose (lCMRGlc). In infants less than 5 weeks old lCMRGlc was highest in sensorimotor cortex, thalamus, brainstem, and cerebellar vermis. By 3 months, lCMRGlc had increased in parietal, temporal, and occipital cortices; basal ganglia; and cerebellar cortex. Frontal and dorsolateral occipital cortical regions displayed a maturational rise in lCMRGlc by approximately 6 to 8 months. Absolute values of lCMRGlc for various grey matter regions were low at birth (13 to 25 mumol/min/100 gm), and rapidly rose to reach adult values (19 to 33 mumol/min/100 gm) by 2 years. lCMRGlc continued to rise until, by 3 to 4 years, it reached values of 49 to 65 mumol/min/100 gm in most regions. These high rates were maintained until approximately 9 years, when they began to decline, and reached adult rates again by the latter part of the second decade. The highest increases of lCMRGlc over adult values occurred in cerebral cortical structures; lesser increases were seen in subcortical structures and in the cerebellum. This time course of lCMRGlc changes matches that describing the process of initial overproduction and subsequent elimination of excessive neurons, synapses, and dendritic spines known to occur in the developing brain. The determination of changing metabolic patterns accompanying normal brain development is a necessary prelude to the study of abnormal brain development with positron emission tomography.

The postnatal development of stimulated deoxyglucose uptake into the mouse cochlea and the inferior colliculus

The effect of acoustic stimulation on the postnatal development of deoxyglucose uptake into the mouse cochlea and the inferior colliculus was evaluated. Animals between postnatal day 4 and 20 were separated into four different groups depending on their age. Tritiated deoxyglucose was injected intraperitoneally into each animal and tracer uptake was quantitated by microdissection of the tissues and scintillation counting. Acoustic stimulation at a noise level of 100 dB (A) resulted in supra-normal levels of deoxyglucose uptake for all auditory tissues during postnatal days 13, 14, and 15. The lateral wall tissues, which are non-sensory and non-neuronal, also increased deoxyglucose uptake following acoustic stimulation in a manner that paralleled the uptake by the sensory structures. Serum radioactivity and glucose levels remained unchanged during postnatal development, with these parameters remaining stable with acoustic stimulation.

Metabolic anatomy of generalized bicuculline seizures in the newborn marmoset monkey

Sustained convulsive seizures were induced with bicuculline in ketamine-anesthetized marmoset monkeys aged 7 to 18 days. Relative 2-deoxyglucose metabolism was compared in convulsing (N = 9) and control (N = 6) animals. Convulsions were accompanied by striking focal increases in cerebral 2-deoxyglucose uptake which were remarkably consistent from animal to animal. Increased 2-deoxyglucose uptake in broad cortical regions (2- to 3-fold) suggests that cortical mechanisms can be important, even in neonatal seizures. The hippocampus and other limbic system structures were markedly activated, as were nuclei of the basal ganglia and thalamus. In contrast, sensory systems were less affected. No increase in 2-deoxyglucose uptake was found in the lateral geniculate nuclei, and a 22% decrease was found in the inferior colliculus (central core). Increased uptake was found in several white matter regions, and activation of the corpus callosum (2.6-fold) was comparable to that found for many gray matter regions. Our results show that generalized bicuculline seizures can produce striking focal increases in cerebral 2-deoxyglucose metabolism in brain regions known to be vulnerable to epileptic brain damage.

Measurement of regional cerebral blood flow, blood volume and oxygen metabolism in patients with sickle cell disease using positron emission tomography

Regional cerebral blood flow, blood volume, fractional oxygen extraction and oxygen consumption were measured by positron emission tomography in six patients with sickle cell disease to see how oxygen delivery to the brain is maintained in the presence of both anemia and a low oxygen affinity hemoglobin. Both regional cerebral blood flow and blood volume were found to be markedly increased compared to values obtained from 14 normal subjects in the same age range. The mean fractional oxygen extraction was not significantly different in the two groups. Mean oxygen consumption in the two groups was also not significantly different but low values in individual patients with sickle cell disease and the presence of atrophy on the CT-scans of three of them were suggestive of some neuronal loss in patients without any history of nervous system involvement. In view of the known high values of cerebral blood flow and metabolism in childhood, it is suggested that when compounded by anemia and abnormal red cells, a hypercirculatory state may make patients in this age-group particularly prone to ischemic infarction.

Local cerebral glucose utilization in the adult cretinous rat

Local rates of cerebral glucose utilization were determined in 5-month-old neonatally radiothyroidectomized and control (littermate) rats. Virtually all 48 brain regions examined in the thyroidectomized rats exhibited lower rates of glucose utilization than those of the controls with differences ranging from -24 to -58%. The decreases were particularly large in the cerebral cortex and throughout the auditory system. Altered patterns in the intrastructural distribution of rates of glucose utilization were seen in a number of regions and were particularly prominent in the hippocampus and inferior colliculus. Lesser changes were seen in hypothalamic regions involved in the synthesis of thyrotropin releasing hormone (TRH). The results indicate that the many structural, functional and biochemical abnormalities of cretinism are associated with widespread reductions in energy metabolism throughout the brain.

Concurrent overproduction of synapses in diverse regions of the primate cerebral cortex

Synapses develop concurrently and at identical rates in different layers of the visual, somatosensory, motor, and prefrontal areas of the primate cerebral cortex. This isochronic course of synaptogenesis in anatomically and functionally diverse regions indicates that the entire cerebral cortex develops as a whole and that the establishment of cell-to-cell communication in this structure may be orchestrated by a single genetic or humoral signal. This is in contrast to the traditional view of hierarchical development of the cortical regions and provides new insight into the maturation of cortical functions.

Maturational changes in cerebral function in infants determined by 18FDG positron emission tomography

2-Deoxy-2[18F]fluoro-D-glucose positron emission tomography performed in human infants during development revealed progressive changes in local cerebral glucose utilization. In infants 5 weeks of age and younger, glucose utilization was highest in the sensorimotor cortex, thalamus, midbrain-brainstem, and cerebellar vermis. By 3 months, glucose metabolic activity had increased in the parietal, temporal, and occipital cortices and the basal ganglia, with subsequent increases in frontal and various association regions occurring by 8 months. These functional changes measured with positron emission tomography are in agreement with behavioral, neurophysiological, and anatomical alterations known to occur during infant development.

Autoradiographic deoxyglucose study of visually activated extrastriate cortex in the primate: three-dimensional reconstruction

Activation of the visual system with a moving black and white geometric pattern resulted in dense patches or columns of 2-deoxyglucose label in primate extrastriate visual cortex. The three-dimensional reconstruction of these metabolic columns showed that they were arranged in irregularly shaped slabs which extended in an essentially rostrocaudal plane. The slabs tended to merge with one another and to subdivide throughout their course in the extrastriate visual cortex.

Quantitation of the sweating deficiency in diabetes mellitus

This report introduces quantitative tests for the evaluation of sweating and the results obtained in 81 diabetic and 30 control subjects. The tests rely on the ability of pilocarpine, introduced into the skin by iontophoresis, to stimulate sweating from fully or partially innervated sweat glands but not from denervated glands. Many diabetic patients had a reduced number of excitable sweat glands and a low volume of sweat per square centimeter of skin. The results of the sweat tests correlated best with the clinically determined perception of pain from pinprick. The similar degree of involvement of sudomotor axons and pain-conveying axons may be related to the known similarity in size and reinnervation patterns. There was poor correlation of the sweating deficiency with alpha motor conduction velocity and with denervation of foot muscles as determined by the evoked muscle action potential. The number of excitable sweat glands was usually normal if the muscle action potential was above 0.5 mv, and often normal even when a muscle action potential was unobtainable. Every diabetic patient with abnormal sweating and several with normal sweating had reduced heart rate fluctuation during a standard Valsalva maneuver or during slow respiration.