1. Learning and Memory in Female Rats:
Effects of a high fat diet and enriched environment
Andrew Suter
Behavioral Neuroscience Laboratory
California State University, Bakersfield

2. Enriched Environments
Donald Hebb ( )
Pioneered the field of environmental enrichment
Behavioral benefits
Improved performance in detour and maze tasks
Solved test problems more easily than their laboratory counterparts
Modern-era research on environmental enrichment can be traced back to 1949, when the biopsychologist Donald O. Hebb anecdotally observed that the laboratory rats he took home for his daughters to play with had behavioral improvements over their littermates who remained in standard cages in the laboratory.
Impoverished Environment
Enriched Environment

3. Enriched Environments and Brain Development
Mammals that are exposed to Enriched Environments show:
Greater survival of neurons (Nilsson et al., 1999)
Increased dendritic branching ( Beauquis et al. , 2010)
Increased synapotgenesis (Birch et al., 2013)
Increased neurogenesis (Römer et al., 2011)

4. Enriched Environments & Neurogenesis
Here we have a study by Mora et al. showing the effect of a high fat diet on neurogenesis in the hippocampus. As you can see, both young and old rats in enriched environments showed increased levels of neurogenesis in the hippocampus over their counterparts in the control group.
Fig. 1. Effects of different housing conditions (8 weeks) on the number of BrdU+ cells in the dentate gyrus (newborn granule cells) of young (2 months) and aged (25 months) rats male rats. Environmental enrichment significantly increased neurogenesis in the hippocampus of young and old rats compared with control housing conditions (Mora et al., 2007, Brain Research Reviews)

5. Where is Neurogenesis Occurring?
Hippocampus
Short Term Memory into Long Term Memory
Hippocampus
Hippocampus
Human Brain
Rat Brain

6. Enriched Environments & Learning and Memory in Male rats
Rats placed in Enriched Environments have better memory
Morris Water Maze
Qiu et al., 2012

7. Neurogenesis, High Fat Diet, And Sex
4 weeks of high fat diet resulted in significant reduction of neurogenesis in male rats, and not in female rats.
But not in females
….however
Lindqvist et al. (2006)

8. Rational & Research Question
Given that we know enriched environments lead to:
Increased neurogenesis in the areas of the brain that play a role in learning and memory
And
Given that we know a high fat diet leads to:
Decreased neurogenesis in the hippocampus
And that this effect is different in males and females…
We wanted to compare the behavioral effects (spatial learning) of a high fat diet in male and female rats kept in enriched environments

9. Standard Environment Enriched Environment (Female)
6 mo later
@ 16 mo
Standard Environment
Enriched Environment
(Female)
Enriched Environment
(Male)

10. AIN-93G, Research Diets, NJ, USA
6 mo later
@ 16 mo
Standard Rodent Chow (11% fat)
#5001 Purina, USA
Western Diet (39% fat)
AIN-93G, Research Diets, NJ, USA

11. 6 mo later
@ 16 mo

12. 8-Arm Radial Maze: Test of Spatial Learning
Arms: 61cm L, x 23cm W, x 23cm H
Measure of:
Short-Term: each trial
Long-Term: over the 8 days

13. Design & Analysis DV: Errors in 8-Arm Maze DV :Time to Complete Task
2X2X(8) Mixed Design
Standard Rat Cage
Standard Rat Chow n=14
High Fat Diet n=14
Enriched Environment
Standard Chow n =14
High Fat Diet
N=14
Between: Environment & Diet
Within: 8 Days of Testing
DV: Errors in 8-Arm Maze
DV :Time to Complete Task
Mixed Design 2X2X(8) ANOVA

14. Female Errors in 8-Arm Radial Maze
4 month
10 month
16 month

15. Summary of Finding
Memory: Errors
High fat diets contributed negatively to memory in female rats.
Regardless of diet, female rats housed in enriched environments showed significant improvement in spatial memory.
These data show that females are similarly effected by a high fat diet despite a lack of change in neurogenesis
Time:
Rats on a high fat diet completed the task slower than their standard chow counterparts in both environmental conditions (data not shown)
In both males and females, Enriched Environments have a positive impact

16. Translation to Humans Diet may impact children’s learning
Long-term impacts of childhood diet may be ameliorated by an enriched environment

17. Future Research Analyze Phase 4 of testing (April, 2016)
Longitudinal comparison to Male data
Presenting at Society for Neuroscience
New Projects!

18. Gayle & Ben Batey Fund for the Neurosciences
Acknowledgements
Faculty Mentor:
Dr. Isabel Sumaya
BNL Supervisor
Samirah Hussain
BNL Assistants:
Christine Dawson
Lyncie Fink
Sukhi Momi
Nayeli Ramirez
Monica Rosas
Susie Villarreal
The Rats!
CSU SRS Program
Gayle & Ben Batey Fund for the Neurosciences

19. Behavioral Neuroscience Lab