Communicating Memory Information Between the Hippocampus and Prefrontal Cortex

Jadhav paper full image

The brain has a remarkable capacity to record our daily experiences and recall this stored information to guide our behavior. For example, every time you decide to get a cup of coffee on campus, you immediately know where to go and then step toward your destination. The ability to successfully memorize paths and navigate in the environment is fundamental for animals searching for food (see Illustration), as well as for humans surviving in a complicated environment, especially when you don’t have your smartphone to rely on, but only your brain as the inner GPS! However, how does the brain learn and remember such plans that allow us to get from one place to another?

We know that a structure in brain called the hippocampus plays an important role in encoding and storing memories. The hippocampus is thought to replay remembered experiences during fast, ripple-like brain waves, termed sharp-wave ripples (SWRs), that occur during “down-time” for the brain, i.e., offline periods during sleep and during pauses in active behavior. It has been previously shown by Jadhav and colleagues that selectively disrupting these ripple oscillations using precisely-timed electrical impulses impairs the ability of animals to learn in spatial mazes, suggesting that this “mental replay” is important for navigation and memory (Jadhav et al., 2012, Science). Notably, mental replay is not isolated activity in the hippocampus, but works together with the prefrontal cortex (PFC), the executive center of brain involved in storing memories and making decisions (Jadhav et al., 2016, Neuron). However, exactly how such memory replay supports memory processing in waking and sleep states had remained elusive.

In a new article published in the Journal of Neuroscience (Tang et al., 2017), the Jadhav lab (the team included Neuroscience graduate students Wenbo Tang and Justin Shin) used high-density electrophysiology to record large numbers of neurons in both the hippocampus and prefrontal cortex in both sleep and awake states. They discovered that as rats learned a spatial memory task, the activity in the hippocampal-prefrontal network replayed recent experiences in a precise manner during SWRs that occurred when animals paused from actively exploring the maze. This structured mental replay related to ongoing spatial behavior is ideally suited for storing and retrieving memories to inform decisions. When animals were asleep after exploring the maze, the hippocampal-prefrontal replay, however, appeared “noisy” and mixed. This replay occurring during sleep periods can support the ability of the brain to consolidate memories, by selectively integrating related memories to build a coherent map for long-term storage (see Illustration). These findings show how memory information is communicated between the hippocampus and PFC during ripple oscillations, and indicate that mental replay during sleep and awake states serve distinct roles in memory. These studies collectively provide fundamental knowledge about the neural substrates of memories. They will thus provide important insights into memory deficits that are prevalent in many neurological disorders that involve the hippocampal-prefrontal network, such as Alzheimer’s disease and schizophrenia.

Hippocampal-Prefrontal Reactivation during Learning Is Stronger in Awake Compared with Sleep States. Wenbo Tang, Justin D. Shin, Loren M. Frank and Shantanu P. Jadhav. Journal of Neuroscience 6 December 2017, 37 (49) 11789-11805.

 

Searches for Tenure-Track Faculty in the Sciences, 2017

Brandeis has six open searches for tenure-track faculty in the Division of Science this fall, with the intent to strengthen cross-disciplinary studies across the sciences. We are looking forward to a busy season of intriguing seminars from candidates this winter.

  1. Assistant Professor of Biochemistry. Biochemistry is looking for a creative scientist to establish an independent research program addressing fundamental questions of biological, biochemical, or biophysical mechanism, and who will maintain a strong interest in teaching Biochemistry.
  2. Assistant Professor of Chemistry. Chemistry seeks a creative individual at the assistant professor level for a tenure-track faculty position in physical (especially theoretical/computational) chemistry, materials chemistry, or chemical biology.
  3. Assistant Professor of Computer Science. Computer Science invites applications for a full-time, tenure-track assistant professor, beginning Fall 2018, in the broad area of Machine Learning and Data Science, including but not limited to deep learning, statistical learning, large scale and cloud-based systems for data science, biologically inspired learning systems, and applications of analytics to real-world problems.
  4. Assistant Professor in Soft Matter or Biological Physics. Physics invites applications for the position of tenure-track Assistant Professor beginning in the fall of 2018 in the interdisciplinary areas of biophysics, soft condensed matter physics and biologically inspired material science.
  5. Assistant Professor or Associate Professor in Psychology. Psychology invites applications for a tenure track appointment at the rank of Assistant or Associate Professor, with a specialization in Aging, to start August 2018. They seek an individual with an active human research program in any aspect of aging, including cognitive, social, clinical and health psychology.
  6. Tenure Track Assistant Professor in Applied MathematicsMathematics invites applications for a tenure-track position in applied mathematics at the rank of assistant professor beginning fall 2018. An ideal candidate will be expected to help to build an applied mathematics program within the department, and to interact with other science faculty at Brandeis. Candidates from all areas of applied mathematics will be considered.

Brandeis University is an equal opportunity employer, committed to building a culturally diverse intellectual community, and strongly encourages applications from women and minorities.  Diversity in its student body, staff and faculty is important to Brandeis’ primary mission of providing a quality education.  The search committees are therefore particularly interested in candidates who, through their creative endeavors, teaching and/or service experiences, will increase Brandeis’ reputation for academic excellence and better prepare its students for a pluralistic society.

Sekuler elected to Society of Experimental Psychologists

Robert Sekuler photoLouis and Frances Salvage Professor of Psychology and Professor of Neuroscience Robert Sekuler has been elected a fellow of the Society of Experimental Psychologists.  The society, founded by Edward Titchener in 1904, elects 6 new members annually from among the leading experimentalists in North America. Sekuler and his lab continue to research issues involved with visual perception, visual and auditory memory, and the cognitive process, often using video games in the research process.

Taste and smell are intertwined in the rat brain

A recent paper in Current Biology titled “A Multisensory Network for Olfactory Processing” from the Katz Lab in Psychology tackles the question of where in rat brain the senses of taste and smell are processed, and just how distinct the two senses are. In addition to Katz, authors on the paper include former postdoctoral fellows Joost Maier and Jennifer Li, as well as Neuroscience graduate student Meredith Blankenship.

The paper discusses their finding that the tongue and the nose work together to help you decide what potential foods are actually good to eat. This intimate cooperation leads to an intertwining and interdependence of function; everyone who has had a cold knows that things don’t taste right when the sense of smell is blocked (by snot). They now show that the opposite is true as well–specifically, that the part of the cortex known to be responsible for taste is also required for the sense of smell.

Recordings from taste and olfactory cortex

First, they show that there is a strong neural connection between taste cortex (GC) and olfactory cortex (PC): this connection ensures that information about tastes in the mouth reaches the latter from the former, but also ensures that a constant chatter of action potentials (the language of the brain) flows between the two, even in the total absence of a substance on the tongue. Thus, switching those taste cortex neurons off both removes any evidence of taste information in olfactory cortex AND changes the way olfactory cortex deals with odor information arriving directly from the nose. The result of this impact is striking: a rat utterly fails to recognize a familiar odor when taste cortex is silent; the taste system is a part of the smell system.

The implications of this finding for neuroscience are far-reaching. It suggests a major breakdown of the basic dogma that the different sensory systems, each of which originate in distinct sense organs (the nose for smell, the tongue for taste) process their input independently. In fact, the brain likely doesn’t “see” tastes and smells as separate at all, but as unified parts of holistic objects…FOOD.

Maier JX, Blankenship ML, Li JX, Katz DB. A Multisensory Network for Olfactory Processing. Curr Biol. 2015.

Jadhav receives NARSAD Young Investigator Grant

Assistant Professor of Psychology Shantanu Jadhav has recently been named to receive a 2015 NARSAD Young Invesigator Grant from the Brain & Behavior Research Foundation. The $70,000 award will help allow the Jadhav lab to

investigate the physiological interactions between the brain’s hippocampal and prefrontal cortex regions that support learning and memory-guided behavior. The two structures are important for different aspects of memory formation, storage, and retrieval, and impaired hippocampal-prefrontal interactions have been implicated in neurological disorders related to cognition, including memory disorders and schizophrenia.

SciFest V is in the books

The Brandeis University Division of Science held its annual undergraduate research poster session SciFest V on July 30, 2015. Despite the 90 degree heat (and the steam leak) outside, the student presenters in the Shapiro Science atrium admirably kept their cool and showed off the results of their summer’s (or last year’s) worth of independent research. We had a great audience of grad students, postdocs, faculty, proud parents, members of the Brandeis senior administration, visiting neuroscientists at Brandeis helping evaluate our Computational Neuroscience training program, and physicists at Brandeis attending the IGERT Summer Institute.

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If you’re a student who didn’t get to present, or you’re a community member who just wanted a chance to talk about science with our energized undergrads, we’re planning another session for Fall Fest 2015. Stay tuned for details.

For a few more impressions of the event, see the story at Brandeis NOW. More pictures and abstract books are available at the SciFest site.

SciFest V by numbers

 

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