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Selection of currently relevant memory traces by the orbitofrontal cortex
NemoImage
11, Number
5, 2000,
Part 2 of 2 Parts ID
E EI-1”
MEMORY
- LEARNING
Selectionof currently relevant memory traces by the orbitofrontal cortex Armin Schnider*, Valerie Treyert, Alfred Buck? *Clirzique de reeducation, University Hospital, CH-1211 Geneva 14 / SwitzerlandPET Center, University Hospital, CH-8091 Zurich / Switzerland tPET Center, University Hospital, CH-8091 Zurich / Switzerland We used H2[15]0 PET to explore the selection repeatedly presented with the same set of pictures, recurrences within the runs. Thus, performance in distinction between currently repeated and previously medial temporal structures, subsequent runs provoked area is essential for sorting out mental associations
of currently relevant memories by the healthy human brain. Subjects were arranged in different order each time, and were requested to indicate picture the 1st run depended on new learning, whereas subsequent runs required seen but currently non-repeated pictures. Whereas initial learning activated circumscribed posterior medial orbitofrontal activation. We suggest that this that pertain to ongoing reality.
Introduction Purposeful actions require the distinction between currently relevant memories and currently irrelevant mental associations. Spontaneous confabulators act according to currently irrelevant memores due to an inability to suppress currently irrelevant memory traces (1, 2, 3, 4). Their lesions always involve anterior limbic structures, in particular the orbitofrontal cortex (OFC) or its connections in the basal forebrain (1, 2, 3,4). Here, we used H2[ iSJO PET to explore the brain structures involved in the initial storage and subsequent selection of currently relevant information from memory. Methods. 8 healthy men saw 60 pictures and were requested to indicate picture recurrences within the test run (Fig.1). Unbeknownst to them, the series was composed of 40 pictures, among which 12 were selected during the run to reappear once (4 pictures) or twice (8 pictures) as a target (total, 20 picture recurrences). Following the first run, 4 additional runs were made in rapid succession with only 90 s break between runs. All runs were composed of the same set of 40 pictures but each time with changing order. Test instructions were similar to the first run: Subjects were asked to forget that they had already seen all pictures and to indicate picture recurrences solely within the present run. Thus, In the 1st run, all pictures were initially new, and an item that appeared familiar could be assumed to be a picture repetition within this run, i.e., a target. Thus, performance in the 1st run depended on new learning. In subsequent runs, all items were already familiar and responses based on familiarity alone were no more correct. Recognition of an item’s current relevance now demanded the ability to sense its previous occurrence in the present rather than a previous run, i.e., the distinction between events within the present as opposed to previous runs. Results. Brain activity was measured in the lst, 3rd and 5th run (Fig.lb) using H2[15]0 PET. (z>3) were observed in the three nuts. In comparison to a baseline task requiring detection of immediate picture repetitions, new learning (1 st run; Fig. I a) provoked strong, predominantly right-sided medial temporal activation encompassing the hippocampus, parahippocampal and fusiform gyri (Fig.2a, h2). In addition, there was a small area of activation in the right rectal gyrus (Fig.2a, gR). An entirely different activation pattern emerged in the 3rd and 5th run: In the 3rd run, there was a large area of activation in the inferior posterior portion of the left inferior frontal gyrus, lateral of the rectal gyrus (Fig.2b, 01). In the 5th run, there were 2 new areas of activation in the posterior medial OFC on both sides Fig.2c, 02 and 03).
Different
clusters
of significant
Discussion. This study supports our contention, based on our studies on spontaneous confabulators (1, 4), that the posterior OFC makes a distinct, hitherto overlooked contribution to human memory: the selection of those memories and mental associations that have current behavioral relevance and that represent ongoing reality. The medial temporal lobe. by contrast. is only involved when new information has to be stored. References. 1. 2. 3. 4.
A. A. A. A.
Schnider, Schnider. Schnider, Schnider.
C. C. K. R.
von Dlniken, K. Gutbrod, Brain 119, 1365-1375 (1996); von Dlniken. K. Gutbrod, Brain 119, 1627-1632 (1996): Gutbrod, C. W. Hess, G. S&troth, J. Neurol. Neurosurg. Ptak, Nat. Neurosci. 2, 677-681 (1999).
s390
Psychiatry
61, 186-193
(1996):
activation
11, Number
5, 2000,
Part 2 of 2 Parts ID
E EI-1”
MEMORY
- LEARNING
Selectionof currently relevant memory traces by the orbitofrontal cortex Armin Schnider*, Valerie Treyert, Alfred Buck? *Clirzique de reeducation, University Hospital, CH-1211 Geneva 14 / SwitzerlandPET Center, University Hospital, CH-8091 Zurich / Switzerland tPET Center, University Hospital, CH-8091 Zurich / Switzerland We used H2[15]0 PET to explore the selection repeatedly presented with the same set of pictures, recurrences within the runs. Thus, performance in distinction between currently repeated and previously medial temporal structures, subsequent runs provoked area is essential for sorting out mental associations
of currently relevant memories by the healthy human brain. Subjects were arranged in different order each time, and were requested to indicate picture the 1st run depended on new learning, whereas subsequent runs required seen but currently non-repeated pictures. Whereas initial learning activated circumscribed posterior medial orbitofrontal activation. We suggest that this that pertain to ongoing reality.
Introduction Purposeful actions require the distinction between currently relevant memories and currently irrelevant mental associations. Spontaneous confabulators act according to currently irrelevant memores due to an inability to suppress currently irrelevant memory traces (1, 2, 3, 4). Their lesions always involve anterior limbic structures, in particular the orbitofrontal cortex (OFC) or its connections in the basal forebrain (1, 2, 3,4). Here, we used H2[ iSJO PET to explore the brain structures involved in the initial storage and subsequent selection of currently relevant information from memory. Methods. 8 healthy men saw 60 pictures and were requested to indicate picture recurrences within the test run (Fig.1). Unbeknownst to them, the series was composed of 40 pictures, among which 12 were selected during the run to reappear once (4 pictures) or twice (8 pictures) as a target (total, 20 picture recurrences). Following the first run, 4 additional runs were made in rapid succession with only 90 s break between runs. All runs were composed of the same set of 40 pictures but each time with changing order. Test instructions were similar to the first run: Subjects were asked to forget that they had already seen all pictures and to indicate picture recurrences solely within the present run. Thus, In the 1st run, all pictures were initially new, and an item that appeared familiar could be assumed to be a picture repetition within this run, i.e., a target. Thus, performance in the 1st run depended on new learning. In subsequent runs, all items were already familiar and responses based on familiarity alone were no more correct. Recognition of an item’s current relevance now demanded the ability to sense its previous occurrence in the present rather than a previous run, i.e., the distinction between events within the present as opposed to previous runs. Results. Brain activity was measured in the lst, 3rd and 5th run (Fig.lb) using H2[15]0 PET. (z>3) were observed in the three nuts. In comparison to a baseline task requiring detection of immediate picture repetitions, new learning (1 st run; Fig. I a) provoked strong, predominantly right-sided medial temporal activation encompassing the hippocampus, parahippocampal and fusiform gyri (Fig.2a, h2). In addition, there was a small area of activation in the right rectal gyrus (Fig.2a, gR). An entirely different activation pattern emerged in the 3rd and 5th run: In the 3rd run, there was a large area of activation in the inferior posterior portion of the left inferior frontal gyrus, lateral of the rectal gyrus (Fig.2b, 01). In the 5th run, there were 2 new areas of activation in the posterior medial OFC on both sides Fig.2c, 02 and 03).
Different
clusters
of significant
Discussion. This study supports our contention, based on our studies on spontaneous confabulators (1, 4), that the posterior OFC makes a distinct, hitherto overlooked contribution to human memory: the selection of those memories and mental associations that have current behavioral relevance and that represent ongoing reality. The medial temporal lobe. by contrast. is only involved when new information has to be stored. References. 1. 2. 3. 4.
A. A. A. A.
Schnider, Schnider. Schnider, Schnider.
C. C. K. R.
von Dlniken, K. Gutbrod, Brain 119, 1365-1375 (1996); von Dlniken. K. Gutbrod, Brain 119, 1627-1632 (1996): Gutbrod, C. W. Hess, G. S&troth, J. Neurol. Neurosurg. Ptak, Nat. Neurosci. 2, 677-681 (1999).
s390
Psychiatry
61, 186-193
(1996):
activation