Using Fos imaging in the rat to reveal the anatomical extent of the disruptive effects of fornix lesions

Vann, Seralynne Denise ORCID: https://orcid.org/0000-0002-6709-8773, Brown, M. W., Erichsen, Jonathan Thor ORCID: https://orcid.org/0000-0003-1545-9853 and Aggleton, John Patrick ORCID: https://orcid.org/0000-0002-5573-1308 2000. Using Fos imaging in the rat to reveal the anatomical extent of the disruptive effects of fornix lesions. Journal of Neuroscience 20 (21) , pp. 8144-8152.

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Abstract

Activity of the immediate early gene c-fos was compared across hemispheres in rats with unilateral fornix lesions. To engage Fos production, rats first performed a radial arm maze task that is severely disrupted by bilateral fornix lesions. Using immunohistochemical techniques, Fos-positive cells were visualized and counted in 39 sites in both hemispheres. Fornix lesions led to a significant reduction in Fos in all ipsilateral hippocampal subfields, as well as the entorhinal cortex and most of the subicular complex. Other sites that showed reduced activity included the ipsilateral retrosplenial, anterior cingulate, and postrhinal cortices. Subcortical regions showing significant Fos decreases included the anterior thalamic nuclei, supramammillary nucleus, diagonal band of Broca, and lateral septum. Thus, the effects of fornix lesions extended beyond the hippocampal formation and included sites not directly innervated by the tract. These changes were nevertheless selective, as shown by the lack of hemispheric difference in any of the preselected control sites, the perirhinal cortex, or nucleus accumbens. Furthermore, there were no hemispheric differences in an additional group of animals with unilateral fornix lesions that were killed directly from the home cage. The location of Fos changes closely corresponded to those brain regions that when lesioned disrupt spatial working memory. Moreover, there was a correspondence between those brain regions that show increased Fos production in normal animals performing the radial arm maze task and those affected by fornix lesions. These results show that fornix transection has widespread, but selective, effects on a network of structures normally activated by spatial memory processes, with these effects extending beyond the hippocampal formation.

Item Type:	Article
Date Type:	Publication
Status:	Published
Schools:	Optometry and Vision Sciences Psychology Medicine Neuroscience and Mental Health Research Institute (NMHRI)
Subjects:	R Medicine > RC Internal medicine > RC0321 Neuroscience. Biological psychiatry. Neuropsychiatry
Uncontrolled Keywords:	amnesia; fornix; hippocampus; immediate early genes; limbic cortices; rat; spatial memory; thalamus
Additional Information:	Pdf uploaded in accordance with publisher's policy at http://www.jneurosci.org/site/misc/ifa_policies.xhtml#copyright (accessed 27/02/2014).
Publisher:	Society for Neuroscience
ISSN:	0270-6474
Date of First Compliant Deposit:	30 March 2016
Last Modified:	07 Nov 2023 11:17
URI:	https://orca.cardiff.ac.uk/id/eprint/17919

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