Studies of the Brain

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Authors

Hichwa RD.

Institution

Department of Psychiatry, University of Iowa Hospitals and Clinics, Iowa City 52242, USA.

Title

II. PET studies of memory: novel versus practiced free recall of word lists.

Source

Neuroimage. 2(4):296-305, 1995 Dec.

Abstract

Positron emission tomography (PET) with the tracer H215O was used to measure regional cerebral blood flow in 13 healthy volunteers while they engaged in free recall of 15-item word lists from the Rey Auditory Verbal Learning task. The study was designed so that recall of well-practiced versus novel material could be compared. One week before the PET study, subjects were trained to perfect recall of List A, while they were exposed to list B only 60 s prior to PET data acquisition. As in the companion study of free recall of complex narratives, we observed that practice tended to decrease the size of activations in regions involved in the memory component of the task; we also observed that the novel recall task produced greater activation in left frontal regions, probably due to active encoding. A commonality of other regions observed in this pair of studies, as well as other studies of memory in the literature, suggests that the human brain may contain a distributed multinodal general memory system. Nodes on this network include the frontal, parietal, and temporal cortices, the thalamus, the anterior and posterior cingulate, the precuneus, and the cerebellum. There appears to be a commonality of components across tasks (e.g., retrieval, encoding) that is independent of content, as well as differentiation of some components that may be content-specific or tasks-specific. In addition, these results support a significant role for the cerebellum in cognitive functions such as memory.

 

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Authors

Andreasen NC. O'Leary DS. Arndt S. Cizadlo T. Rezai K.

Watkins GL. Ponto LL. Hichwa RD.

Institution

Department of Psychiatry, University of Iowa Hospitals and Clinics, Iowa City

52242, USA.

Title

I. PET studies of memory: novel and practiced free recall of complex narratives.

Source

Neuroimage. 2(4):284-95, 1995 Dec.

Abstract

Positron Emission Tomography (PET) with the tracer H215O was used to measure regional cerebral blood flow in 13 healthy volunteers during two experimental memory tasks, one of which was well-practiced and the other of which was novel. The materials used for the memory tasks consisted of two complex narratives (Story A and Story B from the Wechsler Memory Scale). Natural language materials were chosen because they similate experimentally the natural learning situation and permit study of the neural mechanisms by which recall memory becomes more fluid, automatic, or "rote." One week before the PET study, subjects were trained to perfect recall of Story A, while they were exposed to Story B only 60 s prior to PET data acquisition. Despite the substantial differences in level of familiarity (and in free recall performance), patterns of activation were quite similar; activations presumed to reflect recall in both tasks included frontal, inferior temporal, thalamic, anterior cingulate, and cerebellar regions. Many regions were smaller during recall of the familiar story, however, presumably reflecting greater neural efficiency due to practice. In addition, the novel task activated an additional left frontal region that is presumed to reflect more active encoding. The similarity and multiplicity of the activations in the two tasks suggest that the brain uses a multinodal general network for memory tasks such as free recall, while the differences suggest that some nodes in the network may be used for specific components of memory such as encoding and retrieval.

Authors

Paradiso S. Crespo Facorro B. Andreasen NC. O'Leary DS.

Watkins LG. Boles Ponto L. Hichwa RD.

Institution

Department of Psychiatry Administration, University of Iowa College of Medicine,

Iowa City 52242, USA.

Title

Brain activity assessed with PET during recall of word lists and narratives.

Source

Neuroreport. 8(14):3091-6, 1997 Sep 29.

Abstract

This study investigated the functional neuroanatomy involved in retrieval of structured versus unstructured verbal information. We compared cerebral blood flow using PET with the [15O]water method while subjects engaged in recall of novel and practised narratives and lists of unrelated words. Left orbital frontal cortex was activated during recall of both novel and practised unrelated words. Right parietal cortex was relatively more active during recall of the novel word list. Right orbital frontal cortex and anterior cingulate were relatively more active during recall of the practised but not the novel word list. These results are consistent with the role of left orbital frontal cortex in retrieval of unstructured verbal information. Right orbital frontal activity suggests that cognitive strategies may be involved in retrieval of well-practised words.

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 Authors

Andreasen NC. O'Leary DS. Cizadlo T. Arndt S. Rezai K.

Watkins GL. Ponto LL.

Hichwa RD.

Institution

Department of Psychiatry, University of Iowa Hospitals and Clinics, Iowa City 52242, USA.

Title

Remembering the past: two facets of episodic memory explored with positron emission tomography.

Source

American Journal of Psychiatry. 152(11):1576-85, 1995 Nov.

Abstract

OBJECTIVE: This study used positron emission tomography to examine two kinds of personal memory that are used in psychiatric evaluation: focused episodic memory (recall of past experience, employed in "taking a history") and random episodic memory (uncensored thinking about experience, examined during analytic therapy using free association). For comparison, a third memory task was used to tap impersonal memory that represents general information about the world ("semantic memory"). METHOD: Thirteen subjects were studied using the [15O]H2O method to obtain quantitative measurements of cerebral blood flow. The three conditions were subtracted and their relative relationships examined. RESULTS: The random episodic condition produced activations in widely distributed association cortex (right and left frontal, parietal, angular/supramarginal, and posterior inferior temporal regions). Focused episodic memory engaged a network that included the medial inferior frontal regions, precuneus/retrosplenial cingulate, anterior cingulate, thalamus, and cerebellum. The use of medial frontal regions and the precuneus/retrosplenial cingulate was common to both focused and random episodic memory. The major difference between semantic and episodic memory was activation of Broca's area and the left frontal operculum by semantic memory. CONCLUSIONS: These results indicate that free-ranging mental activity (random episodic memory) produces large activations in association cortex and may reflect both active retrieval of past experiences and planning of future experiences. Focused episodic memory shares some components of this circuit (inferior frontal and precuneus), which may reflect the time-linked components of both aspects of episodic memory, and which permit human beings to experience personal identity, consciousness, and self-awareness.

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Authors

Argenyi EE. Ponto LL. Hichwa RD.

Watkins GL. Kirchner PT. Ryals TJ.

Institution

Department of Radiology 3JPP, University of Iowa Hospitals and Clinics, Iowa City 52242, USA.

Title

Follow-up of treatment of a cerebral arteriovenous malformation with acetazolamide and positron emission tomography.

Source

Clinical Nuclear Medicine. 20(7):639-41, 1995 Jul.

Authors

Andreasen NC. O'Leary DS. Arndt S. Cizadlo T. Hurtig R. Rezai K.

Watkins GL. Ponto LL. Hichwa RD.

Institution

Mental Health Clinical Research Center, University of Iowa Hospitals and Clinics, College of Medicine, Iowa City 52242, USA.

Title

Short-term and long-term verbal memory: a positron emission tomography study.

Source

Proceedings of the National Academy of Sciences of the United States of America. 92(11):5111-5, 1995 May 23.

Abstract

Short-term and long-term retention of experimentally presented words were compared in a sample of 33 healthy normal volunteers by the [15O]H2O method with positron emission tomography (PET). The design included three conditions. For the long-term condition, subjects thoroughly studied 18 words 1 week before the PET study. For the short-term condition, subjects were shown another set of 18 words 60 sec before imaging, with instructions to remember them. For the baseline condition, subtracted from the two memory conditions, subjects read a third set of words that they had not previously seen in the experiment. Similar regions were activated in both short-term and long-term conditions: large right frontal areas, biparietal areas, and the left cerebellum. In addition, the short-term condition also activated a relatively large region in the left prefrontal region. These complex distributed circuits appear to represent the neural substrates for aspects of memory such as encoding, retrieval, and storage. They indicate that circuitry involved in episodic memory has much larger cortical and cerebellar components than has been emphasized in earlier lesion studies.

Authors

Junck L. Gilman S. Rothley JR. Betley AT. Koeppe RA.

Hichwa RD.

Institution

Department of Neurology, University of Michigan Medical School, Ann Arbor.

Title

A relationship between metabolism in frontal lobes and cerebellum in normal subjects studied with PET.

Source

Journal of Cerebral Blood Flow & Metabolism. 8(6):774-82, 1988 Dec.

Abstract

Lesions of one cerebral hemisphere are associated with decreased glucose metabolism, oxygen metabolism, and blood flow in the contralateral cerebellar hemisphere. We used positron emission tomography to look for a functional relationship in cerebral metabolism between the cerebral cortex and the contralateral cerebellum in normal human subjects. Twenty-four normal subjects were scanned with [18F]fluoro-2-deoxy-D-glucose while in a resting state. Asymmetry in local CMRglu (LCMRglu) in the frontal cortex was strongly correlated with asymmetry in LCMRglu in the opposite direction in the cerebellar hemispheres (r = -0.60, p less than 0.001). Widespread subregions of the frontal cortex were found to contribute to this relationship. Considering these results together with previous studies demonstrating that frontal lesions are associated with decreased metabolism in the contralateral cerebellum, we conclude that the frontal cortex exerts a strong modulating influence on metabolism in the contralateral cerebellum in normal subjects, and that this influence may be asymmetrical.

Authors

Damasio H. Grabowski TJ. Tranel D. Hichwa RD. Damasio

AR.

Institution

Department of Neurology, Division of Behavioral Neurology and CognitiveNeuroscience, University of Iowa College of Medicine, Iowa City, 52242, USA.

Title

A neural basis for lexical retrieval [see comments] [published erratum appears in Nature 1996 Jun 27;381(6595):810].

Comments

Comment in: Nature 1996 Apr 11;380(6574):485-6

Source

Nature. 380(6574):499-505, 1996 Apr 11.

Abstract

Two parallel studies using positron emission tomography, one conducted in neurological patients with brain lesions, the other in normal individuals, indicate that the normal process of retrieving words that denote concrete entities depends in part on multiple regions of the left cerebral hemisphere, located outside the classic language areas. Moreover, anatomically separable regions tends to process words for distinct kinds of items.

Authors

O'Leary DS. Andreason NC. Hurtig RR. Hichwa RD.

Watkins GL. Ponto LL. Rogers M. Kirchner PT.

Institution

Department of Psychiatry, University of Iowa Hospitals and Clinics, Iowa City 52242-1057, USA.

Title

A positron emission tomography study of binaurally and dichotically presented stimuli: effects of level of language and directed attention.

Source

Brain & Language. 53(1):20-39, 1996 Apr.

Abstract

Regional cerebral blood flow (rCBF) was measured using positron emission tomography with oxygen- 15 labeled water as 10 normal subjects listened to three types of auditory stimuli (environmental sounds, meaningless speech, and words) presented binaurally or dichotically. Binaurally presented environmental sounds and words caused similar bilateral rCBF increases in left and right superior temporal gyri. Dichotically presented stimuli (subjects attended to left or right ears) caused asymmetric activation in the temporal lobes, resulting from increased rCBF in temporal lobe regions contralateral to the attended ear and decreased rCBF in the opposite hemisphere. The results indicate that auditorily presented language and non-language stimuli activate similar temporal regions, that dichotic stimulation dramatically changes rCBF in temporal lobes, and that the change is due both to attentional mechanisms and to hemispheric specialization.

Authors

Cameron OG. Modell JG. Hichwa RD. Agranoff BW. Koeppe

RA.

Institution

Department of Psychiatry, University of Michigan Medical Center, Ann Arbor 48109-0722.

Title

Changes in sensory-cognitive input: effects on cerebral blood flow.

Source

Journal of Cerebral Blood Flow & Metabolism. 10(1):38-42, 1990 Jan.

Abstract

Eight healthy right-handed young men were subjected to local CBF measurement by [15O]water and positron emission tomography during partial sensory deprivation and during sensory-cognitive activation; physiological, hormonal, and subjective stress measurements were also performed. Results indicated that (a) "whole-brain" CBF increased during activation; (b) the greatest increase in CBF was in the primary visual cortex; (c) differences between hemispheres were not observed, but CBF was greater anteriorly than posteriorly in the deprivation condition only; (d) within-subject variability of CBF was not influenced by the sensory-cognitive condition; and (e) the procedure was not stressful.