Loren Frank
Profile Url: loren-frank
Professor at University of California, San Francisco
Current topics in behavioral neurosciences, November 2016
The hippocampus is well known as a central site for memory processing-critical for storing and later retrieving the experiences events of daily life so they can be used to shape future behavior. Much of what we know about the physiology underlying hippocampal function comes from spatial navigation studies in rodents, which have allowed great strides in understanding how the hippocampus represents experience at the cellular level. However, it remains a challenge to reconcile our knowledge of spatial encoding in the hippocampus with its demonstrated role in memory-dependent tasks in both humans and other animals. Moreover, our understanding of how networks of neurons coordinate their activity within and across hippocampal subregions to enable the encoding, consolidation, and retrieval of memories is incomplete. In this chapter, we explore how information may be represented at the cellular level and processed via coordinated patterns of activity throughout the subregions of the hippocampal network.
Cell, Feb 2020
Cognitive faculties such as imagination, planning, and decision-making entail the ability to represent hypothetical experience. Crucially, animal behavior in natural settings implies that the brain can represent hypothetical future experience not only quickly but also constantly over time, as external events continually unfold. To determine how this is possible, we recorded neural activity in the hippocampus of rats navigating a maze with multiple spatial paths. We found neural activity encoding two possible future scenarios (two upcoming maze paths) in constant alternation at 8 Hz: one scenario per ∼125-ms cycle. Further, we found that the underlying dynamics of cycling (both inter- and intra-cycle dynamics) generalized across qualitatively different representational correlates (location and direction). Notably, cycling occurred across moving behaviors, including during running. These findings identify a general dynamic process capable of quickly and continually representing hypothetical experience, including that of multiple possible futures.
Nature Neuroscience, Jan 2011
The hippocampus is required for the encoding, consolidation and retrieval of event memories. Although the neural mechanisms that underlie these processes are only partially understood, a series of recent papers point to awake memory replay as a potential contributor to both consolidation and retrieval. Replay is the sequential reactivation of hippocampal place cells that represent previously experienced behavioral trajectories and occurs frequently in the awake state, particularly during periods of relative immobility. Awake replay may reflect trajectories through either the current environment or previously visited environments that are spatially remote. The repetition of learned sequences on a compressed time scale is well suited to promote memory consolidation in distributed circuits beyond the hippocampus, suggesting that consolidation occurs in both the awake and sleeping animal. Moreover, sensory information can influence the content of awake replay, suggesting a role for awake replay in memory retrieval.
Talk by Prof. Loren Frank on Mental Health and the Brain at the Battery SF
Neuron, Jan 2019
<p class="body-1"></p><h3 style="margin-top: 30px; margin-bottom: 20px; line-height: 1.1;"><span style="font-size: 1rem;">Highlights</span></h3><div class="section-paragraph" style="margin-top: 10px; margin-bottom: 18px;"><p style="list-style: none; display: flex; margin-bottom: 15px; flex-flow: row wrap; align-items: baseline;"><span style="font-size: 1rem;">• <span style="font-size: 1rem;">Modular polymer electrode-based system capable of recording up to 1,024 channels</span></span></p><ul class="ce-list--remove-bullets" id="ulist0010" style=""><li class="ce-list--remove-bullets__list-item" id="u0015" style="list-style: none; display: flex; margin-bottom: 15px; flex-flow: row wrap; align-items: baseline;"><span class="label" style="display: block; float: none; margin-bottom: 13px; margin-right: 5px; margin-top: -1px;">•</span><div class="ce-list--remove-bullets__list-item__text" style="flex: 1 1 90%;">Recording from 375 single units across multiple regions in freely behaving rats</div><div class="ce-list--remove-bullets__list-item__text" style="flex: 1 1 90%;"><span style="font-size: 1rem;">• </span><span style="font-size: 1rem;">Single-unit recording longevity for 160 or more days post-implantation</span></div></li><li class="ce-list--remove-bullets__list-item" id="u0025" style="list-style: none; display: flex; margin-bottom: 15px; flex-flow: row wrap; align-items: baseline;"><span class="label" style="display: block; float: none; margin-bottom: 13px; margin-right: 5px; margin-top: -1px;">•</span><div class="ce-list--remove-bullets__list-item__text" style="flex: 1 1 90%;">System capable of tracking populations of single units continuously for over a week</div><h3 style="flex: 1 1 90%;"><span style="font-size: 1rem;">Summary</span></h3><div class="ce-list--remove-bullets__list-item__text" style="flex: 1 1 90%;"><span style="font-family: Roboto; font-size: 1rem;">The brain is a massive neuronal network, organized into anatomically distributed sub-circuits, with functionally relevant activity occurring at timescales ranging from milliseconds to years. Current methods to monitor neural activity, however, lack the necessary conjunction of anatomical spatial coverage, temporal resolution, and long-term stability to measure this distributed activity. Here we introduce a large-scale, multi-site, extracellular recording platform that integrates polymer electrodes with a modular stacking headstage design supporting up to 1,024 recording channels in freely behaving rats. This system can support months-long recordings from hundreds of well-isolated units across multiple brain regions. Moreover, these recordings are stable enough to track large numbers of single units for over a week. This platform enables large-scale electrophysiological interrogation of the fast dynamics and long-timescale evolution of anatomically distributed circuits, and thereby provides a new tool for understanding brain activity.</span></div></li></ul><p></p></div> <p class="body-1"></p> <p></p>
Annual International Conference of the IEEE Engineering in Medicine and Biology Society, 2014
The brain is a massively interconnected network of specialized circuits. Even primary sensory areas, once thought to support relatively simple, feed-forward processing, are now known to be parts of complex feedback circuits. All brain functions depend on millisecond timescale interactions across these brain networks. Current approaches cannot measure or manipulate such large-scale interactions. Here we demonstrate that polymer-based, penetrating, micro-electrode arrays can provide high quality neural recordings from awake, behaving animals over periods of months. Our results indicate that polymer electrodes are a viable substrate for the development of systems that can record from thousands of channels across months to years. This is our first step towards developing a 1000+ electrode system capable of providing high-quality, long-term neural recordings.