Reorganized cerebral metabolic interactions in temporal lobe epilepsy.

Patients with left temporal lobe epilepsy demonstrate language impairments that are not well understood. To explore abnormal patterns of brain functional connections with respect to language processing, we applied a principal component analysis to resting regional cerebral metabolic data obtained with positron emission tomography in patients with right- and left-sided temporal lobe epilepsy and controls. Two principal components were expressed differentially among the groups. One principal component comprised a pattern of metabolic interactions involving left inferior frontal and left superior temporal regions-corresponding to Broca's and Wernicke's areas, respectively-and right mesial temporal cortex and right thalamus. Functional couplings between these brain regions were abnormally enhanced in the left-sided epilepsy patients. The right thalamic left superior temporal coupling was also abnormally enhanced in the right-sided epilepsy patients, but differentially from that in the left-sided patients. The other principal component was characterized by a pattern of metabolic interactions involving right and left mid prefrontal and right superior temporal cortex. Although both the right- and left-sided epilepsy patients showed decreased functional couplings between left mid prefrontal and the other brain regions, a weaker right-left mid prefrontal coupling in the left-sided epilepsy patients best distinguished them from the right-sided patients. The two mutually independent, abnormal metabolic patterns each predicted verbal intelligence deficits in the patients. The findings suggest a site-dependent reorganization of two independent, language-subserving pathways in temporal lobe epilepsy.

Cerebral blood flow responses to somatosensory stimulation are unaffected by scopolamine in unanesthetized rat.

Studies with positron-emission tomography have indicated that muscarinic acetylcholine receptors may be involved in the mechanism of enhancement of cerebral blood flow (CBF) by neuronal functional activation. We examined the effects of muscarinic receptor blockade by scopolamine on the local CBF responses to vibrissal stimulation in the whisker-to-barrel cortex sensory pathway in unanesthetized rats. Local CBF was measured by the quantitative autoradiographic [(14)C]iodoantipyrine method. Scopolamine (0.4 or 0.8 mg/kg) was injected i.v. 30 min before measurement of local CBF; control rats received equivalent volumes of physiological saline. Vibrissae on the left side of the face were stroked continuously throughout the 1-min period of measurement of CBF. Local CBF was determined bilaterally in four structures of the pathway, i.e., spinal and principal sensory trigeminal nuclei, ventral posteromedial thalamic nucleus, and barrel field of the sensory cortex, as well as in four representative structures unrelated to the pathway. The higher dose of scopolamine raised baseline CBF in the two trigeminal nuclei, but neither dose diminished the percentage of increases in local CBF because of vibrissal stimulation in any of the stations of the pathway. These results do not support involvement of muscarinic receptors in the mechanism of enhancement of local CBF by functional neuronal activation, at least not in the whisker-barrel cortex sensory pathway in the unanesthetized rat.

Postnatal hemodynamic changes in very-low-birthweight infants.

The purpose of this study was to characterize postnatal changes in regional Doppler blood flow velocity (BFV) and cardiac function of very-low-birthweight infants and to examine factors that might influence these hemodynamic changes. Mean and end-diastolic BFV of the middle cerebral and superior mesenteric arteries, cardiac output, stroke volume, and fractional shortening were measured in 20 infants birthweight 1,002 +/- 173 g, gestational age 28 +/- 2 wk) at 6, 30, and 54 h after birth and before and after feedings on days 7 and 14. Postnatal increases in cerebral BFV, mesenteric BFV, and cardiac output were observed that were not associated with changes in blood pressure, hematocrit, pH, arterial PCO(2), or oxygen saturation. The postnatal pattern of relative vascular resistance (RVR) differed between the cerebral and mesenteric vasculatures. RVR decreased in the middle cerebral but not the superior mesenteric artery. Physiological patency of the ductus arteriosus did not alter postnatal hemodynamic changes. In response to feeding, mesenteric BFV and stroke volume increased, and mesenteric RVR and heart rate decreased. Postprandial responses were not affected by postnatal age or the age at which feeding was initiated. However, the initiation of enteral nutrition before 3 days of life was associated with higher preprandial mesenteric BFV and lower mesenteric RVR than was later initiation of feeding. We conclude that in very-low-birthweight infants over the first week of life 1) systemic, cerebral, and mesenteric hemodynamics exhibit region-specific changes; 2) asymptomatic ductus arteriosus patency and early feedings do not significantly influence these postnatal hemodynamic changes; and 3) cardiac function adapts to increase local mesenteric BFV in response to feedings.

Progression in acute stroke: value of the initial NIH stroke scale score on patient stratification in future trials.

BACKGROUND AND PURPOSE: The objective was to determine the occurrence of neurological changes during the first 48 hours after acute stroke as it relates to initial stroke severity. METHODS: The National Institutes of Health Stroke Scale (NIHSS) was performed serially for the first 48 hours on 127 consecutive ischemic stroke patients (129 strokes) admitted to the neuroscience intensive care unit. Incidence of stroke progression (a >/=3-point increase on the NIHSS) was recorded and analysis performed to determine its association with initial stroke severity and other demographic and physiological variables. Deficit resolution by 48 hours, defined as an NIHSS score of 0 or 1, measured the frequency of functional recovery predicted by the initial deficit. RESULTS: Overall progression was noted in 31% of events (40/129). Applying Bayes' solution to the observed frequency of worsening, the greatest likelihood of predicting future patient progression occurs with stratification at NIHSS scores of 7. Patients with an initial NIHSS of 7 with a 65.9% (27/41) worsening rate (P<0.000005). Forty-five percent (40/88) of those with an initial score of 7 returned to a normal examination within this period (chi2, P<0.000005). CONCLUSIONS: This study suggests that the early clinical course of the neurological deficit after acute stroke is dependent on the initial stroke severity and that a dichotomy in early outcome exists surrounding an initial NIHSS score of 7. These findings may have significant implications for the design and patient stratification in treatment protocols with respect to primary clinical outcome.

Antenatal steroids decrease blood-brain barrier permeability in the ovine fetus.

Antenatal corticosteroid therapy reduces the incidence of intraventricular hemorrhage in premature infants. Enhanced microvascular integrity might provide protection against intraventricular hemorrhage. In the adult, there is evidence to suggest that the blood-brain barrier may be under hormonal control. We hypothesized that antenatal corticosteroids decrease blood-brain barrier permeability in the preterm ovine fetus. Chronically instrumented 120-day-gestation fetuses were studied 12 h after the last of four 6-mg dexamethasone (n = 5) or placebo (n = 6) injections had been given over 48 h to the ewes. Blood-brain barrier function was quantified with the blood-to-brain transfer constant (Ki) for alpha-aminoisobutyric acid (AIB). Ki was significantly lower across brain regions in the fetuses of ewes that received antenatal dexamethasone compared with placebo (ANOVA; interaction, F = 2.54, P < 0.004). In fetuses of dexamethasone- and placebo-treated ewes, Ki (microliter . g brain wt-1. min-1, mean +/- SD) was, respectively, 2.43 +/- 0.27 vs. 3.41 +/- 0.74 in the cortex, 4.46 +/- 0.49 vs. 5.29 +/- 0.85 in the cerebellum, and 3.70 +/- 0.49 vs. 5.11 +/- 0.70 in the medulla. We conclude that antenatal treatment with corticosteroids reduces blood-brain permeability in the ovine fetus.

Role of familial factors in late-onset Alzheimer disease as a function of age.

Whereas early-onset Alzheimer disease (AD; usually onset at age < 50 years) has been defined with genetic mutation on chromosomes 1, 14, and 21, the degree of familial contribution to late-onset AD is unclear. Further, it is uncertain if subgroups of late-onset AD exist. To examine the influence of familial factors as a function of age in late-onset AD we investigated lifetime risks and age-specific hazard rates of AD-like illness among late-onset AD probands' and controls' first-degree relatives, using questionnaires and medical records. As part of a longitudinal study on aging and AD, we studied 78 AD probands with age of onset > or =50 years (28 "definite" and 50 "probable" AD according to NINCDS/ADRDA criteria) and 101 healthy old controls seen since 1981. Both probands and controls were screened rigorously with medical tests and brain imaging and seen regularly until autopsy. Multiple informants and medical records were used for first-degree relatives. Among first-degree relatives, 49 secondary cases of AD-like illness were found for the AD probands' relatives (391 relatives 40 years old or older) compared with 20 cases among controls' relatives (456 relatives 40 years old or older). Relatives of AD probands had a significantly increased lifetime risk of AD-like illness of 52.8+/-11.4% by age 94 years compared with a lifetime risk in relatives of controls of 22.1+/-5.8% by age 90 years. Age-specific hazard rates in relatives of AD probands increased until the 75-79-year age interval and then decreased; in contrast the age-specific hazard rates increased in relatives of controls after the 80-84-year age interval. To determine if a dividing line exist among late-onset AD, several cutoff ages were used in our study to compare cumulative risk curves of AD-like illness between relatives of late-onset probands and relatives of late-late-onset probands. Differences in the pattern of cumulative incidence of AD in relatives showed that 67-71 years is the range for a dividing line between late- and late-late-onset AD. Age-specific hazard rates of AD in relatives supported a difference between late- and late-late-onset. Whereas these rates increased until the 75-79-year age interval and then decreased in late-onset AD, the rates began increasing after the 65-69-year age interval and through the oldest age interval in both late-late-onset AD and control groups. Our results support the concept that familial factors exist in late-onset AD and that different familial factors may exist in late-onset AD subgroups.

Chronic exposure to MPTP as a primate model of progressive parkinsonism: a pilot study with a free radical scavenger.

The development of a validated primate model of progressive parkinsonism is a critical step in the evaluation of drugs that might halt or slow progression of Parkinson's disease. In this pilot study, we gradually exposed 14 cynomolgus monkeys to 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), at a weekly dose of 0.5 mg/kg s.c. for 10 weeks, to determine their probability of not reaching a predetermined endpoint on a disability scale by Kaplan-Meier analysis. Four other MPTP-exposed animals were coadministered the potent free radical scavenger 7-hydroxy-1-[4-(3-methoxyphenyl)-1-piperazinyl]acetylamino-2,2,4,6- tetramethylindan (OPC-14117) as a single oral daily dose of 0.6 g/kg, starting 2 weeks before MPTP initiation. The risk of reaching endpoint by week 10 was 79% and mean time before reaching endpoint was 6 weeks. Global motor activity, recorded in a subset of animals using a portable activity monitor, declined following the first MPTP dose and never recovered. Several cerebrospinal fluid indices of central monoamine metabolism collected by suboccipital puncture at 0, 5, and 10 weeks, including HVA, DOPAC, and tetrahydrobiopterin but not MHPG, were found to be "trait" markers for MPTP exposure, whereas CSF DOPAC and tetrahydrobiopterin constituted potential "state" markers for reaching endpoint. The antioxidant OPC-14117 did not protect against MPTP-induced parkinsonism. Further attempts to validate this incremental model of neurotoxin-induced parkinsonism as a predictor of patient responses to putative neuroprotective agents appear warranted.

Increased endothelial expression of intercellular adhesion molecule-1 in symptomatic versus asymptomatic human carotid atherosclerotic plaque.

BACKGROUND AND PURPOSE: The mechanisms that cause carotid atherosclerotic plaque to become symptomatic remain unclear. Evidence suggests that mediators of inflammation are not only instrumental in the formation of plaque but may also be involved in the rapid progression of atheromatous lesions leading to plaque fissuring, endothelial injury, and intraluminal thrombosis. Our goal is to determine whether intercellular adhesion molecule-1 (ICAM-1), a known component of the inflammatory pathway, is preferentially expressed on symptomatic versus asymptomatic carotid plaques. METHODS: Carotid plaques from symptomatic (n = 25) and asymptomatic (n = 17) patients undergoing carotid endarterectomy with lesions involving >60% stenosis were snap-frozen at the time of surgery. Immunofluorescence studies were performed to measure the percentage of luminal endothelial surface that expressed ICAM-1. The relationships of stroke risk factors, white blood cell count, percent stenosis, and soluble ICAM-1 (sICAM-1) plasma levels to endothelial ICAM-1 expression were investigated. RESULTS: An increased expression of ICAM-1 was found in the high-grade regions of symptomatic (29.5%+/-2.4%, mean+/-SEM) versus asymptomatic (15.7%+/-2.7%, mean+/-SEM) plaques (P=0.002) and in the high-grade versus the low-grade region of symptomatic plaques (29.5+/-2.4, mean+/-SEM, versus 8.9+/-1.6; P<0.001). Plasma sICAM-1 levels were not predictive of symptomatic disease, and no significant correlation between risk factor exposure and endothelial ICAM-1 expression was found. CONCLUSIONS: An elevation in ICAM-1 expression in symptomatic versus asymptomatic plaque suggests that mediators of inflammation are involved in the conversion of carotid plaque to a symptomatic state. The data also suggest a differential expression of ICAM-1, with a greater expression found in the high-grade region than in the low-grade region of the plaque specimen.

Effects of prophylactic low-dose indomethacin on hemodynamics in very low birth weight infants.

Indomethacin decreases cerebral and mesenteric blood flow velocities in premature infants with symptomatic patent ductus arteriosus. Low-dose indomethacin is recommended for the prevention of intraventricular hemorrhage in very low birth weight infants. The hemodynamic effects of prophylactic indomethacin have not been previously examined. We hypothesized that prophylactic indomethacin does not change cerebral and mesenteric blood flow velocities and cardiac function in very low birth weight infants. Twenty-one infants (775 to 1245 gm, 24 to 31 weeks' gestation) were studied before and after indomethacin (0.1 mg/kg) administration at 6, 30, and 54 hours of life. Mean and end-diastolic cerebral and mesenteric blood flow velocities decreased (ANOVA, p < 0.05) after prophylactic indomethacin. The 38% increase in cerebral relative vascular resistance was significantly greater than the 18% increase in mesenteric relative vascular resistance (ANOVA, p < 0.05). In five infants who were fed 1 hour after the third indomethacin dose, the postprandial mesenteric blood flow velocity was significantly greater than the mesenteric blood flow velocity before both indomethacin and feeding (ANOVA, p < 0.05). Cardiac output, stroke volume, fractional shortening, and blood pressure did not change after prophylactic indomethacin administration. We conclude that prophylactic indomethacin (1) reduces cerebral and mesenteric blood flow velocity without affecting cardiac function, (2) increases cerebral more than mesenteric relative vascular resistance, and (3) does not prevent postprandial increases in mesenteric blood flow velocity. We speculate that the increase in cerebral relative vascular resistance is a beneficial effect that contributes to protection against intraventricular hemorrhage.

Changes in cerebral acyl-CoA concentrations following ischemia-reperfusion in awake gerbils.

Transient global cerebral ischemia affects phospholipid metabolism and features a considerable increase in unesterified fatty acids. Reincorporation of free fatty acids into membrane phospholipids during reperfusion following transient ischemia depends on conversion of fatty acids to acyl-CoAs via acyl-CoA synthetases and incorporation of the acyl group into lysophospholipids. To study the effect of ischemia-reperfusion on brain fatty acid and acyl-CoA pools, the common carotid arteries were tied for 5 min in awake gerbils, after which the ligatures were released for 5 min and the animals were killed by microwave irradiation. Twenty percent of these animals (two of 10) were excluded from the ischemia-reperfusion group when it was demonstrated statistically that brain unesterified arachidonic acid concentration was not elevated beyond the range of the control group. Brain unesterified fatty acid concentration was increased 4.4-fold in the ischemic-reperfused animals, with stearic acid and arachidonic acid increasing the most among the saturated and polyunsaturated fatty acids, respectively. The total acyl-CoA concentration remained unaffected, indicating that reacylation of membrane lysophospholipids is maintained during recovery. However, there was a substantial increase in the stearoyl- and arachidonoyl-CoA and a marked decrease in palmitoyl- and docosahexaenoyl-CoA. These results suggest that unesterified fatty acid reacylation into phospholipids is reprioritized according to the redistribution in concentration of acyl-CoA molecular species, with incorporation of stearic acid and especially arachidonic acid being favored.

Ontogeny of blood-brain barrier function in ovine fetuses, lambs, and adults.

The ontogeny of regional blood-brain barrier function was quantified with the rate constant for influx (Ki) across the blood-brain barrier with the small molecular weight synthetic, inert hydrophilic amino acid alpha-aminoisobutyric acid (AIB) in chronically instrumented early (87 days of gestation, 60% of gestation) and late (137 days of gestation, 90% of gestation) gestation fetal, newborn (3 days of age), older (24 days of age), and adult (3 years of age) sheep. The Ki was significantly (P < 0.05) lower in the brain regions of the adult sheep and in most brain regions of newborn and older lambs compared with fetuses at 60 and 90% of gestation. The Ki exhibited regional brain heterogeneity (P < 0.05) in the five groups. The patterns of regional heterogeneity were accentuated (P < 0.05) in the younger groups. We conclude that ontogenic decreases in blood-brain barrier permeability are observed in ovine fetuses from 60% of gestation to maturity in the adult.

Enhanced regional cerebral metabolic interactions in thalamic circuitry predicts motor recovery in hemiparetic stroke.

We applied a multiple regression/discriminant analysis to resting metabolic data from patients with first hemiparetic suprathalamic infarctions to determine if metabolic interdependencies, which may separate recovered (N=12) from nonrecovered (N=9) patients, suggest important motor-recovery pathways. Recovered, vs. nonrecovered, patients showed an enhanced ipsilesional thalamic-contralesional cerebellar metabolic interdependency. This pattern correctly classified 91% of recovered and 88% of nonrecovered patients. Metabolic interactions involving bilateral supplementary motor area, ipsilesional thalamus, and contralesional cerebellum distinguished all recovered patients from age/sex-matched controls (N=12). These results suggest that altered functional interactions in thalamic circuitry may reflect plastic reorganization associated with motor recovery from hemiparesis.

Sex differences in patterns of hemispheric cerebral metabolism: a multiple regression/discriminant analysis of positron emission tomographic data.

Sex differences in brain hemispheric structure and function have been reported, and sex-related differences in hemispheric interregional correlations were reported in a prior analysis of resting PET glucose metabolic (rCMRglc) data. To explore further the effect of sex on patterns of hemispheric brain functional interactions, we applied a multiple regression/discriminant analysis to resting rCMRglc PET data from young normal men and women to test two hypotheses: (1) women have stronger between-hemisphere functional interactions; (2) men have stronger within-hemisphere functional interactions. Two separate discriminant functions based on these hypotheses distinguished men and women: the first reflected rCMRglc interdependencies between hemispheres and correctly classified all women and 94% of the men; the second reflected rCMRglc interdependencies within the left hemisphere and correctly classified 82% of the women and 88% of the men. Because the discriminant functions successfully distinguished men and women, these results provide support for both hypotheses.

Detection of an Alzheimer disease pattern of cerebral metabolism in Down syndrome.

Correlational analysis of cerebral metabolic (rCMRglc) data obtained with positron emission tomography (PET) assesses group differences and has demonstrated reduced frontal-parietal rCMRglc interdependencies in Alzheimer's disease (AD). A multivariate analysis of rCMRglc data assesses individual differences. We recently identified discriminant functions, reflecting frontal-parietal rCMRglc interdependencies, that separated AD from control subjects. To test if the functions would identify an AD rCMRglc pattern in older Down syndrome (DS) adults with (DS DAT+) or without (DS DAT-) dementia, we applied the functions to longitudinal rCMRglc data in: young DS (n = 15), DS DAT- (n = 10), DS DAT+ (n = 4), and young controls (n = 15). All DS DAT+ and some of the later DS DAT- scans were classified as AD. The results provide additional validation of the functions and suggest their utility for the early detection of AD.

Blood-brain barrier permeability measurements by double-indicator method using intravenous injection.

The double-indicator technique with intracarotid bolus injection is useful for the estimation of transfer rates across the human blood-brain barrier. A method using intravenous tracer injection is developed whereby the input is measured at a peripheral artery and the output is measured at the jugular vein. To correct for differences in the brain input of test and reference substances, a five-parameter Dirac impulse response for passage through the cerebrovascular bed is computed from the input and output of the reference substance. This response is then combined with a capillary model of the brain. This is then convoluted with the arterial input curve of the test substance to yield a theoretical test output curve, which is compared with the actual test output curve. On the basis of these two curves and an appropriate mathematical model for the brain, estimates of blood-brain barrier permeability are obtained. In the present study, the techniques are compared in 13 patients in whom alternating intracarotid and intravenous bolus injections were given. For D-glucose, the two techniques yielded similar results. This was also the case for L-phenylalanine, provided that the erythrocyte compartment was taken into account. Data obtained after intravenous injection of leucine and water yielded similar results compared with previous intracarotid data.

Abnormal pattern of cerebral glucose metabolic rates involving language areas in young adults with Down syndrome.

Correlational and discriminant analyses were applied to "resting" state (eyes covered, ears plugged) regional cerebral glucose metabolic data, obtained with positron emission tomography (PET) and [18F] fluorodeoxyglucose in 14 retarded adults with Down syndrome (10 men, 4 women; age 26-38 years) and 17 age- and sex-matched controls. Down and control subjects showed no differences in the pattern of correlations. However, a discriminant function, reflecting regional interactions involving primary language areas, successfully classified the Down (100%) and control (88%) subjects. The results are consistent with a disruption of brain regional interactions involving language areas in adults with Down syndrome.

Mutant herpes simplex virus induced regression of tumors growing in immunocompetent rats.

Herpes simplex virus (HSV) mutants kill dividing tumor cells but spare non-proliferating, healthy brain tissue and may be useful in developing new treatment strategies for malignant brain tumors. Two HSV mutants, a thymidine kinase deficient virus (TK-) and a ribonucleotide reductase mutant (RR-), killed 7/7 human tumor cell lines in tissue culture. The TK-HSV killed Rat RG2 glioma and W256 carcinoma lines but not the rat C6 glioma in culture. TK-HSV replication (12 pfu/cell) was similar to wild-type HSV (10 pfu/cell) in rapidly dividing W256 cells in tissue culture, but was minimal (< 1 pfu/cell) in serum-starved cells, suggesting that the proliferative activity of tumor cells at the site and time of TK-HSV injection may influence efficacy in vivo. Subcutaneous W256 tumors in male Sprague-Dawley rats were injected with TK-HSV or free inoculum. A significant effect of TK-HSV therapy on W256 tumor growth was demonstrated compared to controls (p = 0.002). Complete regression was observed in 4/9 experimental tumors, with no recurrence over 6 months. Tumor growth in the remaining 5/9 animals was attenuated during the first 3 to 5 days after treatment, but not beyond 5 days compared to 9 matched control animals; no tumor regression was observed in any of the control animals. These results suggest that HSV mutants are potentially useful as novel therapeutic agents in the treatment of tumors in immunocompetent subjects.

Individual differences in cerebral metabolic patterns during pharmacotherapy in obsessive-compulsive disorder: a multiple regression/discriminant analysis of positron emission tomographic data.

A multiple regression/discriminant analysis of positron emission tomographic cerebral metabolic (rCMRglc) data in 10 obsessive-compulsive disorder (OCD) patients before and during pharmacotherapy was carried out to see if rCMRglc interdependencies distinguished OCD patients from controls. Before therapy, a discriminant function reflecting parietal, sensorimotor, and midbrain rCMRglc interdependencies correctly classified eight (80%) of the 10 patients as OCD; after therapy, six (70%) were classified as controls, most of whom were responders. Before therapy, rCMRglc interdependencies involving basal ganglia, thalamus, limbic, and sensory and association cortical regions distinguished 67% of patients who clinically responded to drug (RESP, n = 6) and 75% of patients who did not (NRESP, n = 4) from controls. After therapy, all RESP were classified as controls; classification of NRESP remained unchanged. The results suggest the conjunctive utility of this method to assess individual differences in rCMRglc during pharmacotherapy, and to explore the neurobiology of OCD.

Effects of physostigmine on local cerebral glucose utilization in the central components of the rat visual system.

The effects of intravenous administration of physostigmine at doses of 0.03, 0.095, or 0.3 mg/kg on local cerebral glucose utilization (LCGU) were determined in 3 structures of the visual system of the rat brain by means of the quantitative 2-[14C]deoxyglucose method. LCGU was increased in the superior colliculus (superficial gray layer), but unchanged in the visual cortex and the lateral geniculate body. To determine whether the observed effect of physostigmine on the superior colliculus depended on input from the retina, the highest dose of physostigmine was administered to rats which had previously been enucleated bilaterally. Enucleation decreased LCGU in the superior colliculus of the animals not treated with physostigmine and blocked the effect of physostigmine on LCGU. The effect of physostigmine in the superior colliculus appears, therefore, to depend on input from the retina.

Early detection of Alzheimer's disease: a statistical approach using positron emission tomographic data.

Correlational analysis of regional cerebral glucose metabolism (rCMRglc) obtained by high-resolution positron emission tomography (PET) has demonstrated reduced neocortical rCMRglc interactions in mildly/moderately demented patients with probable Alzheimer's disease (AD). Thus, identification of individual differences in patterns of rCMRglc interactions may be important for the early detection of AD, particularly among individuals at greater risk for developing AD (e.g., those with a family history of AD). Recently, a statistical procedure, using multiple regression and discriminant analysis, was developed to assess individual differences in patterns of rCMRglc interdependencies. We applied this new statistical procedure to resting rCMRglc PET data from mildly/moderately demented patients with probable AD and age/sex-matched controls. The aims of the study were to identify a discriminant function that would (a) distinguish patients from controls and (b) identify an AD pattern in an individual at risk for AD with isolated memory impairment whose initial PET scan showed minor abnormalities, but whose second scan showed parietal hypometabolism, coincident with further cognitive decline. Two discriminant functions, reflecting interactions involving regions most involved in reduced correlations in probable AD, correctly classified 87% of the patients and controls, and successfully identified the first scan of the at-risk individual as AD (probability > 0.70). The results suggest that this statistical approach may be useful for the early detection of AD.