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The hippocampus plays a critical role in goal-directed navigation. Across different environments, however, hippocampal maps are randomized, making it unclear how goal locations could be encoded consistently. To address this question, we developed a virtual reality task with shifting reward contingencies to distinguish place versus reward encoding. In mice performing the task, large-scale recordings in CA1 and subiculum revealed a small, specialized cell population that was only active near reward yet whose activity could not be explained by sensory cues or stereotyped reward anticipation behavior. Across different virtual environments, most cells remapped randomly, but reward encoding consistently arose from a single pool of cells, suggesting that they formed a dedicated channel for reward. These observations represent a significant departure from the current understanding of CA1 as a relatively homogeneous ensemble without fixed coding properties and provide a new candidate for the cellular basis of goal memory in the hippocampus.

Steve Heinemann, one of the fathers of modern molecular neuroscience and a pioneer in neurotransmitter receptor biology, passed away on August 6, 2014, in La Jolla, California. Steve was well known in the neuroscience community as a genuinely nice guy with an unorthodox approach to research. For almost four decades in an extraordinarily productive career he helped to drive a quantum leap forward in elucidating the molecular components and cellular basis of excitatory neurotransmission in the mammalian CNS.

SummaryWorking memory is an emergent property of neuronal networks, but its cellular basis remains elusive. Recent data show that principal neurons of the entorhinal cortex display persistent firing at graded firing rates that can be shifted up or down in response to brief excitatory or inhibitory stimuli. Here, we present a model of a potential mechanism for graded firing. Our multicompartmental model provides stable plateau firing generated by a nonspecific calcium-sensitive cationic (CAN) current. Sustained firing is insensitive to small variations in Ca2+ concentration in a neutral zone. However, both high and low Ca2+ levels alter firing rates. Specifically, increases in persistent firing rate are triggered only during high levels of calcium, while decreases in rate occur in the presence of low levels of calcium. The model is consistent with detailed experimental observations and provides a mechanism for maintenance of memory-related activity in individual neurons.

You might expect these two texts to be quite similar in tone, content, and organization. After all, repeated revisions of the standard fat Neuroscience texts for first-year med students have converged upon a common, comprehensive, and predictable pattern that admirably suits medical curricula focused on the National Boards. Surprise! These books, each written by a single author, are as different as still lifes by two skilled, confident artists. Each book is the product of years of experience teaching a particular course, and from the different goals of these courses come the books' particular strengths and unique voices.