So, here’s some hot off the press research that I did…
We exposed rats to a high fat / high sugar “junk food” diet or a standard diet in the control animals and then tested their memories on a task known as trace conditioning which allowed us to determine how different memory systems were functioning – the hippocampus and the amygdala. In this task the rats were exposed to 2 environments, which differed in smell, appearance and size. In one of these environments the rats were exposed to a flashing light signal, and 30 seconds after it’s offset, they received a static shock. So the rats had to learn about 2 things, the flashing light (Conditioned Stimulus) and the environment (context). We found a dissociation in what each group of rats remembered, the standard (healthy) diet rats learned about the environment, which relies on the hippocampus, but the junk food diet consuming rats learned about the flashing light, which does not require the hippocampus, indicating dysfunction of this memory structure.
We then analysed the molecular components of hippocampal tissue of the rats and found a reduction in the neuroplasticity associated protein Reelin in the junk food fed rats. Reelin is important in the developing brain and the adult brain in the arrangement of synapses that allow neurons to connect to each other to form new memories, a process called Long Term Potentiation. It has been implicated in Alzheimer’s disease, schizophrenia and autism, so the fact that junk food reduces it’s expression is important, as these diets may cause long term changes in both adult and developing brains.
Dietary-induced obesity disrupts trace fear conditioning and decreases hippocampal reelin expression Brain, Behaviour and Immunity (2014)