Integration, Navigation, And Organization: An Exploration Of Two Spatial Processing Loops Using Environmental Enrichment In Adolescent Rats

ASU Author/Contributor (non-ASU co-authors, if there are any, appear on document)
Charlotte Heloise Godfrey (Creator)
Appalachian State University (ASU )
Web Site:
Mark Zrull

Abstract: Spatial cognition and memory help to build understanding of an organism’s environment. Understanding how one comes to perceive and navigate an environment can give insight into the order and disorder of environmental processing. In this thesis, c-FOS was used as a measure of neural activation in eight regions within two neural circuits involved with spatial processing. One neural circuit is thought to be involved with the processing of overall spatial scene, while the other is thought to be involved in processing object-location information. The two neural circuits of interest are begun with efferents from superficial medial entorhinal cortex (MEC) and superficial lateral entorhinal cortex (LEC), with MEC leading the loop processing overall spatial scene and LEC leading the loop processing object-location information. The MEC-led loop also involves proximal cornu ammonis 1 (CA1), distal subiculum, and deep MEC. The LEC-led loop involves distal CA1, proximal subiculum, and deep LEC. Environmental enrichment (EE) was used to study these loops, as EE is thought to cause activation in these regions. EE is the provision of stimulation using an environment containing toys, ramps, and platforms. Neural activation in the neural regions was manipulated through periodic EE /or a final EE session organized as a 2x2 factorial design, with four groups: No+No, EE+No, EE+EE, and No+EE (No/EE before + references periodic EE, No/EE after + references final EE). Four hypotheses were posed, with predictions of higher activation of just the No+EE group in superficial MEC, proximal CA1, distal subiculum, distal CA1, and proximal subiculum when compared to all other groups, and predictions of higher activation of the No+EE and EE+EE groups in superficial LEC, deep MEC, and deep LEC when compared to control groups (No+No and EE+No).Significantly higher neural activation was observed in the No+EE group in comparison to all other groups in superficial MEC, proximal CA1, and distal CA1 (p = .042, p = .003, and p < .001, respectively). In superficial LEC, distal subiculum, proximal subiculum, deep MEC, and deep LEC, No+EE and EE+EE groups showed significantly higher activation than control groups (No+No and EE+EE) (p= .017, p = .007, p < .001, p = .002, and p = .006, respectively), with no significant difference between No+EE and EE+EE groups. The findings suggest neural processing in superficial MEC and LEC and proximal and distal CA1 that is in accordance with current research in the field. These results also suggest a more involved role of the subiculum in spatial processing and add to the growing body of evidence investigating the role of deep entorhinal cortex (EC) in providing contextual feedback to superficial layers.

Additional Information

Honors Project
Godfrey, C. (2021). Integration, Navigation, And Organization: An Exploration Of Two Spatial Processing Loops Using Environmental Enrichment In Adolescent Rats. Unpublished Honors Thesis. Appalachian State University, Boone, NC.
Language: English
Date: 2021
spatial representation, environmental enrichment, processing loops, c-FOS, entorhinal cortex, hippocampus, subiculum

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