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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

A schematic representation of the Ziggurat task (ZT). The task consisted of an open-field box constructed from opaque white laminate and 16 ziggurats, and required rats to learn and remember that the top surface of one of 16 ziggurats in the open field is baited with a food reward. All ziggurats were identical and made of white styrofoam covered by transparent duct tape. The standard or non-cued version of the ZT used in the present study requires animals to use spatial (distal and/or proximal) cues to navigate to the goal ziggurat. On testing days, the rats are released from each starting point (orange ziggurats) and explore the environment in which only one goal ziggurat (peripheral or central; blue and green ziggurats, respectively) is baited (Faraji et al., 2008).
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Figure 1: A schematic representation of the Ziggurat task (ZT). The task consisted of an open-field box constructed from opaque white laminate and 16 ziggurats, and required rats to learn and remember that the top surface of one of 16 ziggurats in the open field is baited with a food reward. All ziggurats were identical and made of white styrofoam covered by transparent duct tape. The standard or non-cued version of the ZT used in the present study requires animals to use spatial (distal and/or proximal) cues to navigate to the goal ziggurat. On testing days, the rats are released from each starting point (orange ziggurats) and explore the environment in which only one goal ziggurat (peripheral or central; blue and green ziggurats, respectively) is baited (Faraji et al., 2008).

Mentions: All procedures for ZT testing were similar to previously reported (Faraji et al., 2008, 2010, 2011a). The ZT environment is illustrated in Figure 1. Prior to behavioral testing, rats were habituated to the ZT environment for 10 min each day for 4 days. In ZT environment animals must use spatial cues (distal and/or proximal) to navigate to the goal ziggurat.


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)

A schematic representation of the Ziggurat task (ZT). The task consisted of an open-field box constructed from opaque white laminate and 16 ziggurats, and required rats to learn and remember that the top surface of one of 16 ziggurats in the open field is baited with a food reward. All ziggurats were identical and made of white styrofoam covered by transparent duct tape. The standard or non-cued version of the ZT used in the present study requires animals to use spatial (distal and/or proximal) cues to navigate to the goal ziggurat. On testing days, the rats are released from each starting point (orange ziggurats) and explore the environment in which only one goal ziggurat (peripheral or central; blue and green ziggurats, respectively) is baited (Faraji et al., 2008).
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 1: A schematic representation of the Ziggurat task (ZT). The task consisted of an open-field box constructed from opaque white laminate and 16 ziggurats, and required rats to learn and remember that the top surface of one of 16 ziggurats in the open field is baited with a food reward. All ziggurats were identical and made of white styrofoam covered by transparent duct tape. The standard or non-cued version of the ZT used in the present study requires animals to use spatial (distal and/or proximal) cues to navigate to the goal ziggurat. On testing days, the rats are released from each starting point (orange ziggurats) and explore the environment in which only one goal ziggurat (peripheral or central; blue and green ziggurats, respectively) is baited (Faraji et al., 2008).
Mentions: All procedures for ZT testing were similar to previously reported (Faraji et al., 2008, 2010, 2011a). The ZT environment is illustrated in Figure 1. Prior to behavioral testing, rats were habituated to the ZT environment for 10 min each day for 4 days. In ZT environment animals must use spatial cues (distal and/or proximal) to navigate to the goal ziggurat.

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