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

Enriched Environments Donald Hebb (1904-1984) 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

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)

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)

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

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

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)

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

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

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

6 mo later @ 16 mo

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

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

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

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

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

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

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

Behavioral Neuroscience Lab