Performance Characteristics of an Eight-Ring Whole Body PET Scanner

Kops, Elena Rota; Herzog, Hans; Schmid, A.; Holte, S.; Feinendegen, L. E.

doi:10.1097/00004728-199005000-00022

Cited by 178 publications

(41 citation statements)

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“…17 and 18). A General ElectricScanditronix (Uppsala) model PC4096 15-slice whole-body tomograph was used (19). An individually molded thermoplastic face mask (True Scan, Annapolis, MD) was used to minimize head motion.…”

Section: Methodsmentioning

confidence: 99%

Conscious recollection and the human hippocampal formation: evidence from positron emission tomography.

Schacter

Alpert

Savage

et al. 1996

Proc. Natl. Acad. Sci. U.S.A.

534

367

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We used positron emission tomography (PET) to examine the role of the hippocampal formation in implicit and explicit memory. Human volunteers studied a list of familiar words, and then they either provided the first word that came to mind in response to three-letter cues (implicit memory) or tried to recall studied words in response to the same cues (explicit memory). There was no evidence of hippocampal activation in association with implicit memory. However, priming effects on the implicit memory test were associated with decreased activity in extrastriate visual cortex. On the explicit memory test, subjects recalled many target words in one condition and recalled few words in a second condition, despite trying to remember them. Comparisons between the two conditions showed that blood-flow increases in the hippocampal formation are specifically associated with the conscious recollection of studied words, whereas bloodflow increases in frontal regions are associated with efforts to retrieve target words. Our results help to clarify some puzzles concerning the role of the hippocampal formation in human memory.Understanding the role of the hippocampal formation in learning and memory constitutes an enduring problem in cognitive neuroscience. Studies of brain-damaged amnesic patients implicate the hippocampal formation in explicit or conscious memory for past events. By contrast, the hippocampal formation is thought to be uninvolved in a nonconscious or implicit form of memory known as priming (1-4). Yet previous attempts to test these ideas directly by studying the normal human brain with positron emission tomography (PET) have yielded inconclusive results.In an early PET study by Squire et al. (5), subjects studied a list of familiar words (e.g., GARNISH) and were then tested with three-letter word stems (e.g., GAR-). When subjects were instructed to provide a word from the study list on a cued recall test (explicit memory), there were significant blood flow increases in the vicinity of the right hippocampal formation compared with a baseline condition in which subjects responded to stems of nonstudied words. In a separate scan conducted in the same experimental session, subjects were instructed to complete stems of previously studied words with the first word that comes to mind (implicit memory), and a priming effect was observed: subjects preferentially completed the stems with words from the study list. Compared with the baseline condition, priming was associated with decreased blood flow in extrastriate occipital cortex and increased blood flow in the right hippocampus/parahippocampal gyrus. Because amnesic patients with hippocampal damage show intact priming effects (6-8), the former finding is consistent with the idea that such effects are mediated by brain systems outside the

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Section: Methodsmentioning

confidence: 99%

Conscious recollection and the human hippocampal formation: evidence from positron emission tomography.

Schacter

Alpert

Savage

et al. 1996

Proc. Natl. Acad. Sci. U.S.A.

534

367

View full text Add to dashboard Cite

show abstract

“…The PET camera was a General Electric PC4096 15-slice whole-body scanner used in the stationary mode. Detailed descriptions of the reconstruction software have been published (24). The slices are contiguous with a 6.5-mm center-to-center distance (axial field equal to 97.5 mm) and intrinsic axial resolution of 6.0 mm full width at half-maximum (fwhm).…”

Section: Methodsmentioning

confidence: 99%

Functional neuroanatomy of antisaccade eye movements investigated with positron emission tomography.

O’Driscoll

Alpert

Matthysse

et al. 1995

Proc. Natl. Acad. Sci. U.S.A.

242

148

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Increasing interest in the role of the frontal lobe in relation to psychiatric and neurologic disorders has popularized tests of frontal function. One of these is the antisaccade task, in which both frontal lobe patients and schizophrenics are impaired despite normal performance on (pro)saccadic tasks. We used positron emission tomography to examine the cerebral blood flow changes associated with the performance of antisaccades in normal individuals. We found that the areas of the brain that were more active during antisaccades than saccades were highly consistent with the oculomotor circuit, including frontal eye fields (FEFs), supplementary motor area, thalamus, and putamen.

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“…The 15 PET image slices had a slice distance of 6.5 mm. 15 A transmission scan using a rotating 68 Ge pin source was obtained before the emission scans to correct for attenuation. The PET images were reconstructed with a Hanning filter to an effective image resolution (full width at half maximum) of 8 mm.…”

Section: Pet Imaging Of Rcbfmentioning

confidence: 99%

The Role of Diaschisis in Stroke Recovery

Seitz

Azari

Knorr

et al. 1999

Stroke

Self Cite

185

105

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Background and Purpose-Recovery from hemiparesis after stroke has been shown to involve reorganization in motor and premotor cortical areas. However, whether poststroke recovery also depends on changes in remote brain structures, ie, diaschisis, is as yet unresolved. To address this question, we studied regional cerebral blood flow in 7 patients (meanϮSD age, 54Ϯ8 years) after their first hemiparetic stroke. Methods-We analyzed imaging data voxel by voxel using a principal component analysis by which coherent changes in functional networks could be disclosed. Performance was assessed by a motor score and by the finger movement rate during the regional cerebral blood flow measurements. Results-The patients had recovered (PϽ0.001) from severe hemiparesis after on average 6 months and were able to perform sequential finger movements with the recovered hand. Regional cerebral blood flow at rest differentiated patients and controls (PϽ0.05) by a network that was affected by the stroke lesion. During blindfolded performance of sequential finger movements, patients were differentiated from controls (PϽ0.05) by a recovery-related network and a movement-control network. These networks were spatially incongruent, involving motor, sensory, and visual cortex of both cerebral hemispheres, the basal ganglia, thalamus, and cerebellum. The lesion-affected and recovery-related networks overlapped in the contralesional thalamus and extrastriate occipital cortex. Conclusions-Motor recovery after hemiparetic brain infarction is subserved by brain structures in locations remote from the stroke lesion. The topographic overlap of the lesion-affected and recovery-related networks suggests that diaschisis may play a critical role in stroke recovery. (Stroke. 1999;30:1844-1850.)Key Words: brain mapping Ⅲ hemiparesis Ⅲ infarction Ⅲ neuronal plasticity Ⅲ tomography, emission computed I n 1914, von Monakow 1 established the concept of diaschisis as a principle for recovery from brain lesions. Accordingly, functional changes in brain structures remote from the site of a focal brain damage, ie, diaschisis, were conceptualized as processes underlying functional recovery. The role of diaschisis, however, has remained elusive. Modern neuroimaging studies have provided first clues to the existence of diaschisis by revealing that focal brain lesions are accompanied by widespread metabolic changes involving the affected cerebral hemisphere but extending into brain areas supplied by contralateral and cerebellar arteries. 2 More recently, such remote metabolic changes have been shown to be lesionspecific in terms of cerebral topography and the related clinical deficits. 3,4 Corresponding findings in experimental models of ischemia further support the concept that these remote abnormalities are brought about acutely by neurotransmitter changes and chronically by degeneration of fiber tracts. 5 However, evidence that diaschisis is also related to recovery of function is virtually lacking.In this study we tested the hypothesis that lesion-induced, remot...

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Performance Characteristics of an Eight-Ring Whole Body PET Scanner

Cited by 178 publications

References 0 publications

Conscious recollection and the human hippocampal formation: evidence from positron emission tomography.

Conscious recollection and the human hippocampal formation: evidence from positron emission tomography.

Functional neuroanatomy of antisaccade eye movements investigated with positron emission tomography.

The Role of Diaschisis in Stroke Recovery

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