Hippocampal Functioning in Juveniles

     

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      What is the earliest memory you can remember from childhood?  According to Dr. Ted Dumas of PBNJ Lab at the Krasnow Institute of GMU, many of us will not remember much from before three years of age.  This may be due to the delayed development of the hippocampus, resulting in the late formation of personal episodic memories until later in the post-natal period.  With his research on the relationship between glutamate receptor deactivation and spatial memories, Dr. Dumas helped us further understand the various aspects of memory formation.


     The hippocampus is crucial in the process of memory formation, which is facilitated by synaptic responses.  Dr. Dumas' research on rat subjects in spatial mazes has shown that spatial guided navigation does not develop until the end of three post-natal weeks. The reasoning behind this is the place cells are not evident in the hippocampus until about 16 days of age.  In addition, there is a reduced capacity of glutamatergic synapses to activate postsynaptic neurons.  This fact formed a foundation for Dr. Dumas' research on how memory formation may be limited due to a lack of synaptic excitation.  Experiments were done on rats given the drug Ampakines, which prolongs synaptic responses.  The rats were then placed in a Y-Maze to test for spontaneous alternation.  Rats without hippocampal lesions visited the least recently visited arm about 60-70% of the time.  However, rats with hippocampal damage had more difficulty remembering which arm they last visited, so the rate dropped.  Along with drugs that increase postsynaptic activation, visual enrichment also showed to be a key factor in cognitive development.  Rats' eyelids were parted four days prior to when it would have normally opened to give the rats more visual experience.  The increase of visual exposure accelerated the development of the hippocampus.  With that, we know that hippocampal maturation is associated with the duration of excitatory synaptic responses and spatial deliberation.  

Y-Maze Depicting Spontaneous Alternation

     
     The ability to observe how prolonging excitatory synaptic responses affects hippocampal neurons will surely help neuroscientists study and understand more about the development and retrieval of memories.  The plasticity of the brain can be seen with the help of drugs such as Ampakines, allowing further discovery on the encoding of memories.  The study has shown high success rates for juvenile subjects.  It would be great if in the future there will be a way to prolong memory in the elderly or those with cognitive damage.  Glutamate is known to be a central part of learning, memory, and cognitive development.  Since Ampakines regulates the levels of glutamate, could this drug also be used to treat diseases such as Alzheimer's?