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Abstract
In 1947, a second power of anesthesia was described: "With anesthetic agents we seem to have a tool for producing and holding at will, and at little risk, different levels of consciousness--a tool that promises to be of great help in studies of mental phenomena." In 1995, anesthetic manipulation was coupled with neuroimaging, paving the way for detailed assessments of the relationship between the structure and the functioning of the brain. Anesthesia combined with neuroimaging thus provides a unique tool for investigating the neural correlates of human cognition.
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Affiliation(s)
- M T Alkire
- Department of Anesthesiology, University of California, Irvine, California, USA
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Cahill L, Uncapher M, Kilpatrick L, Alkire MT, Turner J. Sex-related hemispheric lateralization of amygdala function in emotionally influenced memory: an FMRI investigation. Learn Mem 2004; 11:261-6. [PMID: 15169855 PMCID: PMC419728 DOI: 10.1101/lm.70504] [Citation(s) in RCA: 262] [Impact Index Per Article: 13.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
The amygdala appears necessary for enhanced long-term memory associated with emotionally arousing events. Recent brain imaging investigations support this view and indicate a sex-related hemispheric lateralization exists in the amygdala relationship to memory for emotional material. This study confirms and further explores this finding. Healthy men and women underwent functional Magnetic Resonance Imaging (fMRI) while viewing a series of standardized slides that were rated by the subjects as ranging from emotionally neutral to highly arousing. Two weeks later, memory for the slides was assessed in an incidental recognition test. The results demonstrate a significantly stronger relationship in men than in women between activity of the right hemisphere amygdala and memory for those slides judged as arousing, and a significantly stronger relationship in women than in men between activity of the left hemisphere amygdala and memory for arousing slides. An ANOVA confirmed a significant interaction between sex and hemisphere regarding amygdala function in memory. These results provide the strongest evidence to date of a sex-related hemispheric lateralization of amygdala function in memory for emotional material. Furthermore, they underscore the view that investigations of neural mechanisms underlying emotionally influenced memory must anticipate, and begin to account for, the apparently substantial influence of sex.
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Affiliation(s)
- Larry Cahill
- Center for the Neurobiology of Learning and Memory and Department of Neurobiology and Behavior, University of California, Irvine, California, 92697-3800, USA.
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Abstract
BACKGROUND Adults with Down syndrome (DS) are at increased risk for dementia and provide an opportunity to identify patterns of brain activity that may precede dementia. Studies of early Alzheimer's disease (AD) and risk of AD show decreased function in posterior cingulate and temporal cortex as initial indicators of the disease process, but whether the origin and sequence of predementia brain changes are the same in DS is unknown. METHODS The regional cerebral glucose metabolic rates (GMR) among middle-aged nondemented people with DS (n = 17), people with moderate AD (n = 10), and age-matched control subjects (n = 24) were compared using PET during a cognitive task. RESULTS Statistical parametric mapping conjunction analyses showed that 1) both DS and AD groups had lower GMR than their respective controls primarily in posterior cingulate and 2) compared with respective controls, the subjects with DS had higher GMR in the same areas of inferior temporal/entorhinal cortex where the AD subjects had lower GMR. The same results were replicated after 1 year of follow-up. CONCLUSIONS As the DS subjects were not clinically demented, inferior temporal/entorhinal cortex hypermetabolism may reflect a compensatory response early in disease progression. Compensatory responses may subsequently fail, leading to neurodegenerative processes that the authors anticipate will be detectable in vivo as future GMR decreases in inferior temporal/entorhinal cortex are accompanied by clinical signs of dementia.
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Affiliation(s)
- R J Haier
- Department of Pediatrics, University of California, Irvine 92697-5000, USA.
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Alkire MT, Vazdarjanova A, Dickinson-Anson H, White NS, Cahill L. Lesions of the basolateral amygdala complex block propofol-induced amnesia for inhibitory avoidance learning in rats. Anesthesiology 2001; 95:708-15. [PMID: 11575545 DOI: 10.1097/00000542-200109000-00025] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
BACKGROUND As the unitary theory of anesthesia gives way to the "multiple sites, multiple mechanisms" concept, the sites involved in mediating the components of anesthesia must be identified. In the current study, we test the hypothesis that the basolateral amygdala complex (BLAC) is a brain site involved with mediating propofol-induced amnesia. METHODS Male Sprague-Dawley rats were divided into two groups, sham-operated control animals and rats given bilateral excitotoxic N-methyl-D-aspartate lesions of the BLAC. For each group, animals were given intraperitoneal saline or propofol (25 mg/kg) 5 min before inhibitory avoidance learning. Rats were given a foot shock (0.4 mA) upon entering the dark side of a two-sided apparatus. Rats could escape additional shock by returning to and staying in the light side. Training ended after shock avoidance for greater than 60 s. Memory was tested at 24 h. Longer latencies to enter the dark side 24 h after training imply better memory. RESULTS Sham-saline-treated animals had a robust memory latency (median latency [interquartile range] = 300 [163-567] s). Sham-propofo-treated animals exhibited a significant anterograde amnesia (latency = 63 [14-111] s) (P < 0.05 vs. sham-saline-treated animal). Both the saline-injected and propofol-injected animals with BLAC lesions showed robust memory (latency = 300 [264-485] and 323 [143480] s, respectively). These latencies did not differ from performance in the sham-saline-treated group and were significantly higher than the latency of the sham-propofol-treated group (both P < 0.05). CONCLUSIONS Discrete BLAC lesions blocked the amnestic effect of propofol. BLAC activity appears to be a requirement for propofol-induced amnesia. This finding suggests that the BLAC is a key brain site mediating anesthetic-induced amnesia.
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Affiliation(s)
- M T Alkire
- Department of Anesthesiology, Center for the Neurobiology of Learning and Memory, University of California, Irvine 92868, USA.
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Alkire MT. The power of observation. Conscious Cogn 2001; 10:236-40; discussion 246-58. [PMID: 11414718 DOI: 10.1006/ccog.2001.0514] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Affiliation(s)
- M T Alkire
- Department of Anesthesiology, University of California, Irvine Medical Center, 101 City Drive South, Building 53, Route 81-A, Orange, California 92868, USA.
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Alkire MT, Haier RJ. Correlating in vivo anaesthetic effects with ex vivo receptor density data supports a GABAergic mechanism of action for propofol, but not for isoflurane. Br J Anaesth 2001; 86:618-26. [PMID: 11575335 DOI: 10.1093/bja/86.5.618] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
If the in vivo effects of anaesthesia are mediated through a specific receptor system, then a relationship could exist between the regional changes in brain metabolism caused by a particular agent and the underlying regional distribution of the specific receptors affected by that agent. Positron emission tomography data from volunteers studied while unconscious during propofol (n=8) or isoflurane (n=5) anaesthesia were used retrospectively to explore for evidence of relationships between regional anaesthetic effects on brain glucose metabolism and known (ex vivo) regional distribution patterns of human receptor binding sites. The regional metabolic reductions caused by propofol differed significantly from those of isoflurane. Propofol's reductions negatively correlated most significantly with the regional distribution of [3H]diazepam and [3H]flunitrazepam (benzodiazepine) binding site densities (r=-0.86, P<0.0005; r=-0.79, P<0.005, respectively) and less strongly with [3H]naloxone (opioid) binding density (r=-0.69, P<0.05). Isoflurane's reductions positively correlated only with muscarinic (acetylcholine) binding density (r=0.85, P<0.05). These findings are consistent with the hypothesis that some of propofol's in vivo anaesthetic effects may be mediated through a GABAergic mechanism and suggest some of isoflurane's in vivo effects might involve antagonism of central acetylcholine functioning.
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Affiliation(s)
- M T Alkire
- Department of Anesthesiology, University of California-Irvine Medical Center, Orange 92868, USA
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Cahill L, Haier RJ, White NS, Fallon J, Kilpatrick L, Lawrence C, Potkin SG, Alkire MT. Sex-related difference in amygdala activity during emotionally influenced memory storage. Neurobiol Learn Mem 2001; 75:1-9. [PMID: 11124043 DOI: 10.1006/nlme.2000.3999] [Citation(s) in RCA: 330] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
We tested the possibility suggested by previous imaging studies that amygdala participation in the storage of emotionally influenced memory is differentially lateralized in men and women. Male and female subjects received two PET scans for regional cerebral glucose-one while viewing a series of emotionally provocative (negative) films, and a second while viewing a series of matched, but emotionally more neutral, films. Consistent with suggestions from several previously published studies, enhanced activity of the right, but not the left, amygdala in men was related to enhanced memory for the emotional films. Conversely, enhanced activity of the left, but not the right, amygdala in women was related to enhanced memory for the emotional films. These results demonstrate a clear gender-related lateralization of amygdala involvement in emotionally influenced memory, and indicate that theories of the neurobiology of emotionally influenced memory must begin to account for the influence of gender.
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Affiliation(s)
- L Cahill
- Department of Neurobiology and Behavior, Center for the Neurobiology of Learning and Memory, CA 92697-3800, USA.
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Alkire MT, Haier RJ, Fallon JH. Toward a unified theory of narcosis: brain imaging evidence for a thalamocortical switch as the neurophysiologic basis of anesthetic-induced unconsciousness. Conscious Cogn 2000; 9:370-86. [PMID: 10993665 DOI: 10.1006/ccog.1999.0423] [Citation(s) in RCA: 251] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
A unifying theory of general anesthetic-induced unconsciousness must explain the common mechanism through which various anesthetic agents produce unconsciousness. Functional-brain-imaging data obtained from 11 volunteers during general anesthesia showed specific suppression of regional thalamic and midbrain reticular formation activity across two different commonly used volatile agents. These findings are discussed in relation to findings from sleep neurophysiology and the implications of this work for consciousness research. It is hypothesized that the essential common neurophysiologic mechanism underlying anesthetic-induced unconsciousness is, as with sleep-induced unconsciousness, a hyperpolarization block of thalamocortical neurons. A model of anesthetic-induced unconsciousness is introduced to explain how the plethora of effects anesthetics have on cellular functioning ultimately all converge on a single neuroanatomic/neurophysiologic system, thus providing for a unitary physiologic theory of narcosis related to consciousness.
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Affiliation(s)
- M T Alkire
- Department of Anesthesiology, University of California at Irvine, Irvine, California 92697, USA.
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Alkire MT, Pomfrett CJ, Haier RJ, Gianzero MV, Chan CM, Jacobsen BP, Fallon JH. Functional brain imaging during anesthesia in humans: effects of halothane on global and regional cerebral glucose metabolism. Anesthesiology 1999; 90:701-9. [PMID: 10078670 DOI: 10.1097/00000542-199903000-00011] [Citation(s) in RCA: 143] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
BACKGROUND Propofol and isoflurane anesthesia were studied previously with functional brain imaging in humans to begin identifying key brain areas involved with mediating anesthetic-induced unconsciousness. The authors describe an additional positron emission tomography study of halothane's in vivo cerebral metabolic effects. METHODS Five male volunteers each underwent two positron emission tomography scans. One scan assessed awake-baseline metabolism, and the other scan assessed metabolism during halothane anesthesia titrated to the point of unresponsiveness (mean +/- SD, expired = 0.7+/-0.2%). Scans were obtained using a GE2048 scanner and the F-18 fluorodeoxyglucose technique. Regions of interest were analyzed for changes in both absolute and relative glucose metabolism. In addition, relative changes in metabolism were evaluated using statistical parametric mapping. RESULTS Awake whole-brain metabolism averaged 6.3+/-1.2 mg x 100 g(-1) x min(-1) (mean +/- SD). Halothane reduced metabolism 40+/-9% to 3.7+/-0.6 mg x 100 g(-1) x min(-1) (P< or =0.005). Regional metabolism did not increase in any brain areas for any volunteer. The statistical parametric mapping analysis revealed significantly less relative metabolism in the basal forebrain, thalamus, limbic system, cerebellum, and occiput during halothane anesthesia. CONCLUSIONS Halothane caused a global whole-brain metabolic reduction with significant shifts in regional metabolism. Comparisons with previous studies reveal similar absolute and relative metabolic effects for halothane and isoflurane. Propofol, however, was associated with larger absolute metabolic reductions, suppression of relative cortical metabolism more than either inhalational agent, and significantly less suppression of relative basal ganglia and midbrain metabolism.
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Affiliation(s)
- M T Alkire
- Department of Anesthesiology, University of California-Irvine Medical Center, Orange 92668, USA.
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Alkire MT, Haier RJ, Fallon JH, Cahill L. Hippocampal, but not amygdala, activity at encoding correlates with long-term, free recall of nonemotional information. Proc Natl Acad Sci U S A 1998; 95:14506-10. [PMID: 9826730 PMCID: PMC24403 DOI: 10.1073/pnas.95.24.14506] [Citation(s) in RCA: 79] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Participation of two medial temporal lobe structures, the hippocampal region and the amygdala, in long-term declarative memory encoding was examined by using positron emission tomography of regional cerebral glucose. Positron emission tomography scanning was performed in eight healthy subjects listening passively to a repeated sequence of unrelated words. Memory for the words was assessed 24 hr later with an incidental free recall test. The percentage of words freely recalled then was correlated with glucose activity during encoding. The results revealed a striking correlation (r = 0.91, P < 0.001) between activity of the left hippocampal region (centered on the dorsal parahippocampal gyrus) and word recall. No correlation was found between activity of either the left or right amygdala and recall. The findings provide evidence for hippocampal involvement in long-term declarative memory encoding and for the view that the amygdala is not involved with declarative memory formation for nonemotional material.
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Affiliation(s)
- M T Alkire
- Department of Anesthesiology, University of California, Irvine, CA 92697-3800, USA.
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Abstract
BACKGROUND To help elucidate the relationship between anesthetic-induced changes in the electroencephalogram (EEG) and the concurrent cerebral metabolic changes caused by anesthesia, positron emission tomography data of cerebral metabolism obtained in volunteers during anesthesia were correlated retrospectively with various concurrently measured EEG descriptors. METHODS Volunteers underwent functional brain imaging using the 18fluorodeoxyglucose technique; one scan always assessed awake-baseline cerebral metabolism (n = 7), and the other scans assessed metabolism during propofol sedation (n = 4), propofol anesthesia (n = 4), or isoflurane anesthesia (n = 5). The EEG was recorded continuously during metabolism assessment using a frontal-mastoid montage. Power spectrum variables, median frequency, 95% spectral edge, and bispectral index (BIS) values subsequently were correlated with the percentage of absolute cerebral metabolic reduction (PACMR) of glucose utilization caused by anesthesia. RESULTS The percentage of absolute cerebral metabolic reduction, evident during anesthesia, trended median frequency (r = -0.46, P = 0.11), and the spectral edge (r = -0.52, P = 0.07), and correlated with anesthetic type (r = -0.70, P < 0.05), relative beta power (r = -0.60, P < 0.05), total power (r = 0.71,P < 0.01), and bispectral index (r = -0.81,P < 0.001). After controlling for anesthetic type, only bispectral index (r = 0.40, P = 0.08) and alpha power (r = 0.37, P = 0.10) approached significance for explaining residual percentage of absolute cerebral metabolic reduction prediction error. CONCLUSIONS Some EEG descriptors correlated linearly with the magnitude of the cerebral metabolic reduction caused by propofol and isoflurane anesthesia. These data suggest that a physiologic link exists between the EEG and cerebral metabolism during anesthesia that is mathematically quantifiable.
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Affiliation(s)
- M T Alkire
- University of California-Irvine Medical Center, Department of Anesthesiology, Orange 92668, USA.
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13
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Abstract
BACKGROUND Although the anesthetic effects of the intravenous anesthetic agent propofol have been studied in the living human brain using brain imaging technology, the nature of the anesthetic state evident in the human brain during inhalational anesthesia remains unknown. To examine this issue, the authors studied the effects of isoflurane anesthesia on human cerebral glucose metabolism using positron emission tomography (PET). METHODS Five volunteers each underwent two PET scans; one scan assessed awake-baseline metabolism and the other scan assessed metabolism during isoflurane anesthesia titrated to the point of unresponsiveness (means +/- SD; expired = 0.5 +/- 0.1%). Scans were obtained with a GE2048 scanner (4.5-mm resolution-FWHM) using the 18fluorodeoxyglucose technique. RESULTS Awake whole-brain glucose metabolism averaged 6.9 +/- 1.5 mg.100 g-1.min-1 (means +/- SD). Isoflurane reduced whole-brain metabolism 46 +/- 11% to 3.6 +/- 0.3 mg.100 g-1.min-1 (P < or = 0.005). Regional metabolism decreased fairly uniformly throughout the brain, and no evidence of any regional metabolic increases were found in any brain region for any participant. A region-of-interest analysis showed that the pattern of regional metabolism evident during isoflurane anesthesia was not significantly different from that seen when participants were awake. CONCLUSION These data clarify that the anesthetic state evident in the living human brain during unresponsiveness induced with isoflurane is associated with a global, fairly uniform, whole-brain glucose metabolic reduction of 46 +/- 11%.
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Affiliation(s)
- M T Alkire
- Department of Anesthesiology, University of California-Irvine Medical Center, Orange 92668, USA.
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Abstract
Previous studies of the cortical input to the mammalian dorsal lateral geniculate nucleus (LGN) have identified a number of possible functions for the corticogeniculate pathway, including alteration of LGN spatial frequency selectivity and facilitation of both binocular interactions and orientation selectivity. These changes may be due to either a tonic or a phasic cortical facilitation or both. The temporal differences between each of these inputs suggests that their impact on LGN cell temporal tuning should be unique. To test this hypothesis, we reversibly blocked the visual cortex (VI) and measured the effects on several indices of the temporal properties of LGN cells, including peak frequency, bandwidth, and response phase. Macaque monkeys were anesthetized and paralyzed during single cell recording from the LGN while area VI was cryogenically deactivated. Single-cell responses were visually evoked with drifting, luminance-modulated, sine-wave gratings and discrete-Fourier analyzed. Cortical cooling produced statistically significant increases or decreases in response amplitude in 64% of cells recorded. In most cases, alterations in response amplitude occurred for stimuli that varied in spatial as well as temporal frequency. For those cells influenced by changes in stimulus temporal frequency, the majority showed changes over a broad range of frequencies. A minority of cells showed changes in either peak temporal tuning or temporal frequency bandwidth. Response phase angles for all temporal frequencies tested were unaffected by cortical cooling. Overall, these results suggest that the cortical input may alter the temporal response properties of LGN cells, perhaps by tonic, but not exclusively excitatory, corticofugal influences.
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Affiliation(s)
- R T Marrocco
- Institute of Neuroscience, University of Oregon, Eugene 97403-1254, USA
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Cahill L, Haier RJ, Fallon J, Alkire MT, Tang C, Keator D, Wu J, McGaugh JL. Amygdala activity at encoding correlated with long-term, free recall of emotional information. Proc Natl Acad Sci U S A 1996; 93:8016-21. [PMID: 8755595 PMCID: PMC38867 DOI: 10.1073/pnas.93.15.8016] [Citation(s) in RCA: 655] [Impact Index Per Article: 23.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
Positron emission tomography of cerebral glucose metabolism in adult human subjects was used to investigate amygdaloid complex (AC) activity associated with the storage of long-term memory for emotionally arousing events. Subjects viewed two videos (one in each of two separate positron emission tomography sessions, separated by 3-7 days) consisting either of 12 emotionally arousing film clips ("E" film session) or of 12 relatively emotionally neutral film clips ("N" film session), and rated their emotional reaction to each film clip immediately after viewing it. Three weeks after the second session, memory for the videos was assessed in a free recall test. As expected, the subjects' average emotional reaction to the E films was higher than that for the N films. In addition, the subjects recalled significantly more E films than N films. Glucose metabolic rate of the right AC while viewing the E films was highly correlated with the number of E films recalled. AC activity was not significantly correlated with the number of N films recalled. The findings support the view derived from both animal and human investigations that the AC is selectively involved with the formation of enhanced long-term memory associated with emotionally arousing events.
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Affiliation(s)
- L Cahill
- Center for the Neurobiology of Learning and Memory, University of California, Irvine 92697-3800, USA
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Alkire MT, Haier RJ, Barker SJ, Shah NK, Wu JC, Kao YJ. Cerebral metabolism during propofol anesthesia in humans studied with positron emission tomography. Anesthesiology 1995; 82:393-403; discussion 27A. [PMID: 7856898 DOI: 10.1097/00000542-199502000-00010] [Citation(s) in RCA: 241] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
BACKGROUND Although the effects of propofol on cerebral metabolism have been studied in animals, these effects have yet to be directly examined in humans. Consequently, we used positron emission tomography (PET) to demonstrate in vivo the regional cerebral metabolic changes that occur in humans during propofol anesthesia. METHODS Six volunteers each underwent two PET scans; one scan assessed awake-baseline metabolism, and the other assessed metabolism during anesthesia with a propofol infusion titrated to the point of unresponsiveness (mean rate +/- SD = 7.8 +/- 1.5 mg.kg-1.h-1). Scans were obtained using the 18fluorodeoxyglucose technique. RESULTS Awake whole-brain glucose metabolic rates (GMR) averaged 29 +/- 8 mumoles.100 g-1.min-1 (mean +/- SD). Anesthetized whole-brain GMR averaged 13 +/- 4 mumoles.100 g-1.min-1 (paired t test, P < or = 0.007). GMR decreased in all measured areas during anesthesia. However, the decrease in GMR was not uniform. Cortical metabolism was depressed 58%, whereas subcortical metabolism was depressed 48% (P < or = 0.001). Marked differences within cortical regions also occurred. In the medial and subcortical regions, the largest percent decreases occurred in the left anterior cingulate and the inferior colliculus. CONCLUSION Propofol produced a global metabolic depression on the human central nervous system. The metabolic pattern evident during anesthesia was reproducible and differed from that seen in the awake condition. These findings are consistent with those from previous animal studies and suggest PET may be useful for investigating the mechanisms of anesthesia in humans.
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Affiliation(s)
- M T Alkire
- Department of Anesthesiology, University of California-Irvine Medical Center, Orange 92668-2901
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Ahn SS, Blaha CD, Alkire MT, Wood E, Gray-Allan P, Marrocco RT, Moore WS. Biphasic striatal dopamine release during transient ischemia and reperfusion in gerbils. Stroke 1991; 22:674-9. [PMID: 2028500 DOI: 10.1161/01.str.22.5.674] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
To clarify the nature of ischemic striatal dopamine release during the earliest periods of neuronal injury, we used chronoamperometry to measure dopamine levels every 60 seconds during various durations of ischemia in 32 gerbils. Catecholamine-selective electrodes were implanted into the brains of anesthetized gerbils subjected to 2, 5, or 10 minutes of transient forebrain ischemia or permanent forebrain ischemia. Four control animals showed a stable chronoamperometric baseline. In the six gerbils subjected to permanent ischemia, dopamine release was rapid during early ischemia and slowed with time. The four animals subjected to 2 minutes of ischemia showed minimal dopamine release. The six gerbils subjected to 5 minutes of ischemia demonstrated a noticeable dopamine release during ischemia, and three of the six developed a massive secondary dopamine release during reperfusion. All six animals subjected to 10 minutes of ischemia demonstrated a similar biphasic dopamine release twice the size of that observed in the 5-minute group. Pretreatment with pargyline in six additional gerbils subjected to 10 minutes of ischemia failed to modify significantly this biphasic pattern of dopamine release. We conclude that dopamine release occurs very early during ischemia and that its magnitude correlates with the duration of an ischemia insult. Reperfusion is associated with an even larger striatal dopamine release. This previously unreported biphasic dopamine release phenomenon may have important clinical implications in the management of cerebral ischemia.
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Affiliation(s)
- S S Ahn
- Department of Surgery, University of California, Los Angeles Center for the Health Sciences 90024-6904
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