Neuroscientists are discovering striking similarities between the way the brain develops and the way it stores knowledge. In a special issue of the journal Learning & Memory, research groups from Caltech, Yale University, and other institutions explore this parallel, presenting new studies on how a family of proteins called growth factors help nerve cells not only to grow but to learn and accumulate a lifetime of memories.

Nerve cells signal one another at specialized connections called synapses, forming circuits that carry out specific functions like coordinating muscle activity or recognizing friends. Scientists widely believe that the brain can store newly learned facts and behaviors by increasing signal strength at the appropriate synapses. As they study this process, however, scientists are discovering the brain has more than one use for the same trick: circuits forming their connections at the beginning of life may use the same synaptic strengthening mechanisms as adult circuits use to learn. Standing out among the common elements are the neurotrophins, a family of proteins critical for cell survival and growth in the developing nervous system. The studies presented in the special issue of Learning & Memory continue a string of exciting indications that neurotrophins are also important for strengthening synapses in the adult brain.

In this issue, Benedikt Berninger, Alejandro Schinder, and Mu-ming Poo (University of California, San Diego) show that neurotrophins have more effect on weak synapses than strong ones. Measuring signal strength between pairs of nerve cells, they find that applying neurotrophins increases synapse strength dramatically if the initial signal is small. If the initial signal is already large, neurotrophins do not increase it much further. This work suggests neurotrophins strengthen nerve connections by "maturing" undeveloped synapses, leaving strong or "mature" synapses relatively unaffected. So learning may really be growing after all.

LEARNING & MEMORY Vol. 6(3)

TABLE OF CONTENTS

Regulation of Synaptic Function by Neurotrophic Factors in Vertebrates and Invertebrates: Implications for Development and Learning (Review Article) Sharen E. McKay, Angela L. Purcell, and Thomas J. Carew

Activity-Dependent Activation of TrkB Neurotrophin Receptors in the Adult CNS Raquel Aloyz, James P. Fawcett, David R. Kaplan, Richard A. Murphy, and Freda D. Miller

Synaptic Reliability Correlates with Reduced Susceptibility to Synaptic Potentiation by Brain-Derived Neurotrophic Factor Benedikt Berninger, Alejandro F. Schinder, and Mu-ming Poo

Signaling Mechanisms Mediating BDNF Modulation of Synaptic Plasticity in the Hippocampus Wolfram A. Gottschalk, Hao Jiang, Nicole Tartaglia, Linyin Feng, Alexander Figurov, and Bai Lu

Blockade of NR2B-Containing NMDA Receptors Prevents BDNF Enhancement of Glutamatergic Transmission in Hippocampal Neurons Robert A. Crozier, Ira B. Black, and Mark R. Plummer

Neuronal NT-3 Is Not Required For Synaptic Transmission or Long-term Potentiation in Area CA1 of the Adult Rat Hippocampus Long Ma, Gerald Reis, Luis F. Parada, Erin M. Schuman

Transgenic Brain-Derived Neurotrophic Factor Modulates A Developing Cerebellar Inhibitory Synapse Shaowen Bao, Lu Chen, Xiaoxi Qiao, and Richard F. Thompson

BDNF Regulates the Intrinsic Excitability of Cortical Neurons Niraj S. Desai, Lana C. Rutherford, and Gina G. Turrigiano

Growth Factor Modulation of Substrate-Specific Morphological Patterns in Aplysia Bag Cell Neurons Lore M. Gruenbaum and Thomas J. Carew

Trophic Factor-Induced Plasticity of Synaptic Connection Between Identified Lymnaea Neurons Melanie A. Woodin, Toshiro Hamakawa, M. Takasaki, K. Lukowiak, and Naweed I. Syed

TGF-b1 in Aplysia: Role in Long-Term Changes in the Excitability of Sensory Neurons and Distribution of TbR-II-like Immunoreactivity Jeannie Chin, Annie Angers, Leonard J. Cleary, Arnold Eskin, and John H. Byrne

Inflammation Causes a Long-Term Hyperexcitability in the Nociceptive Sensory Neurons of Aplysia Maryjane Farr, Jenny Mathews, De-Fen Zhu, and Richard T. Ambron

For complete manuscripts or additional information, please contact:

Peggy Calicchia
Editorial Secretary
Learning & Memory
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phone (516) 367-6834
fax: (516) 367-8334
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