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Topographical disorientation after ischemic mini infarct in the dorsal hippocampus: whispers in silence.

Faraji J, Soltanpour N, Moeeini R, Roudaki S, Soltanpour N, Abdollahi AA, Metz GA - Front Behav Neurosci (2014)

Bottom Line: Some populations of hippocampal cells are particularly sensitive to ischemic events, however, rendering hippocampal functions especially vulnerable to ischemia-induced deficits.Comparison of region-specific HPC lesions in the present study indicated that dorsal hippocampal function is critically required for topographic orientation in a complex environment.Topographic disorientation as reflected by enhanced return behaviors may represent one of the earliest predictors of cognitive decline after silent ischemic insult that may be potentially traced with sensitive clinical examination in humans.

View Article: PubMed Central - PubMed

Affiliation: Department of Neuroscience, Canadian Centre for Behavioural Neuroscience (CCBN), University of Lethbridge Lethbridge, AB, Canada ; Faculty of Nursing and Midwifery, Golestan University of Medical Sciences Gorgan, Iran.

ABSTRACT
Silent focal ischemic mini infarcts in the brain are thought to cause no clinically overt symptoms. Some populations of hippocampal cells are particularly sensitive to ischemic events, however, rendering hippocampal functions especially vulnerable to ischemia-induced deficits. The present study investigated whether an otherwise silent ischemic mini infarct in the hippocampus (HPC) can produce impairments in spatial performance in rats. Spatial performance was assessed in the ziggurat task (ZT) using a 10-trial spatial learning protocol for 4 days prior to undergoing hippocampal ischemic lesion or sham surgery. Hippocampal silent ischemia was induced by infusion of endothelin-1 (ET-1), a potent vasoconstrictor, into either the dorsal or the ventral hippocampus (dHPC and vHPC). When tested postoperatively in the ZT using a standard testing protocol for 8 days, rats with hippocampal lesions exhibited no spatial deficit. Although spatial learning and memory in the ZT were not affected by the ET-1-induced silent ischemia, rats with dHPC stroke showed more returns when navigating the ZT as opposed to the vHPC rats. Comparison of region-specific HPC lesions in the present study indicated that dorsal hippocampal function is critically required for topographic orientation in a complex environment. Topographic disorientation as reflected by enhanced return behaviors may represent one of the earliest predictors of cognitive decline after silent ischemic insult that may be potentially traced with sensitive clinical examination in humans.

No MeSH data available.


Related in: MedlinePlus

Pre-ischemic spatial testing in the ZT. (A) Average latency to locate the peripheral or central goal ziggurats during 4 days of spatial testing. All groups significantly spent less time on memory days to find the spatial goals compared to learning days. (B) Mean path speed averaged across 4 days of testing. (C) Mean path length (distance traveled) to locate the spatial goal during each day of testing (learning and memory) on peripheral- and central-goal trials. (D and E) The number of returns for three groups on learning and memory days during spatial navigation in the ZT to locate peripheral and central goal ziggurats. (d and e) Dark gray squares indicate the location of peripheral and central spatial goals, respectively.
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Figure 5: Pre-ischemic spatial testing in the ZT. (A) Average latency to locate the peripheral or central goal ziggurats during 4 days of spatial testing. All groups significantly spent less time on memory days to find the spatial goals compared to learning days. (B) Mean path speed averaged across 4 days of testing. (C) Mean path length (distance traveled) to locate the spatial goal during each day of testing (learning and memory) on peripheral- and central-goal trials. (D and E) The number of returns for three groups on learning and memory days during spatial navigation in the ZT to locate peripheral and central goal ziggurats. (d and e) Dark gray squares indicate the location of peripheral and central spatial goals, respectively.

Mentions: The results of the pre-ischemic spatial testing in the ZT for 4 days are illustrated in Figures 5A–E. Spatial testing prior to infusion of the ET-1 in the HPC indicated no differences between groups in their latency (time spent to find the goal ziggurat), path speed, path length and returns.


Topographical disorientation after ischemic mini infarct in the dorsal hippocampus: whispers in silence.

Faraji J, Soltanpour N, Moeeini R, Roudaki S, Soltanpour N, Abdollahi AA, Metz GA - Front Behav Neurosci (2014)

Pre-ischemic spatial testing in the ZT. (A) Average latency to locate the peripheral or central goal ziggurats during 4 days of spatial testing. All groups significantly spent less time on memory days to find the spatial goals compared to learning days. (B) Mean path speed averaged across 4 days of testing. (C) Mean path length (distance traveled) to locate the spatial goal during each day of testing (learning and memory) on peripheral- and central-goal trials. (D and E) The number of returns for three groups on learning and memory days during spatial navigation in the ZT to locate peripheral and central goal ziggurats. (d and e) Dark gray squares indicate the location of peripheral and central spatial goals, respectively.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4120695&req=5

Figure 5: Pre-ischemic spatial testing in the ZT. (A) Average latency to locate the peripheral or central goal ziggurats during 4 days of spatial testing. All groups significantly spent less time on memory days to find the spatial goals compared to learning days. (B) Mean path speed averaged across 4 days of testing. (C) Mean path length (distance traveled) to locate the spatial goal during each day of testing (learning and memory) on peripheral- and central-goal trials. (D and E) The number of returns for three groups on learning and memory days during spatial navigation in the ZT to locate peripheral and central goal ziggurats. (d and e) Dark gray squares indicate the location of peripheral and central spatial goals, respectively.
Mentions: The results of the pre-ischemic spatial testing in the ZT for 4 days are illustrated in Figures 5A–E. Spatial testing prior to infusion of the ET-1 in the HPC indicated no differences between groups in their latency (time spent to find the goal ziggurat), path speed, path length and returns.

Bottom Line: Some populations of hippocampal cells are particularly sensitive to ischemic events, however, rendering hippocampal functions especially vulnerable to ischemia-induced deficits.Comparison of region-specific HPC lesions in the present study indicated that dorsal hippocampal function is critically required for topographic orientation in a complex environment.Topographic disorientation as reflected by enhanced return behaviors may represent one of the earliest predictors of cognitive decline after silent ischemic insult that may be potentially traced with sensitive clinical examination in humans.

View Article: PubMed Central - PubMed

Affiliation: Department of Neuroscience, Canadian Centre for Behavioural Neuroscience (CCBN), University of Lethbridge Lethbridge, AB, Canada ; Faculty of Nursing and Midwifery, Golestan University of Medical Sciences Gorgan, Iran.

ABSTRACT
Silent focal ischemic mini infarcts in the brain are thought to cause no clinically overt symptoms. Some populations of hippocampal cells are particularly sensitive to ischemic events, however, rendering hippocampal functions especially vulnerable to ischemia-induced deficits. The present study investigated whether an otherwise silent ischemic mini infarct in the hippocampus (HPC) can produce impairments in spatial performance in rats. Spatial performance was assessed in the ziggurat task (ZT) using a 10-trial spatial learning protocol for 4 days prior to undergoing hippocampal ischemic lesion or sham surgery. Hippocampal silent ischemia was induced by infusion of endothelin-1 (ET-1), a potent vasoconstrictor, into either the dorsal or the ventral hippocampus (dHPC and vHPC). When tested postoperatively in the ZT using a standard testing protocol for 8 days, rats with hippocampal lesions exhibited no spatial deficit. Although spatial learning and memory in the ZT were not affected by the ET-1-induced silent ischemia, rats with dHPC stroke showed more returns when navigating the ZT as opposed to the vHPC rats. Comparison of region-specific HPC lesions in the present study indicated that dorsal hippocampal function is critically required for topographic orientation in a complex environment. Topographic disorientation as reflected by enhanced return behaviors may represent one of the earliest predictors of cognitive decline after silent ischemic insult that may be potentially traced with sensitive clinical examination in humans.

No MeSH data available.


Related in: MedlinePlus