Learning and memory

  • Article
    | Open Access

    Hippocampus is necessary for integrating the context with sensory cues to retrieve memory for unique episodes. Here, the authors show that inhibiting topographically organized projections from hippocampus to the anterior olfactory nucleus independently impairs spatial and temporal odour memory recall.

    • Afif J. Aqrabawi
    •  & Jun Chul Kim
  • Article
    | Open Access

    Serotonin (5-HT) plays many important roles in reward, punishment, patience and beyond, and optogenetic stimulation of 5-HT neurons has not crisply parsed them. The authors report a novel analysis of a reward-based decision-making experiment, and show that 5-HT stimulation increases the learning rate, but only on a select subset of choices.

    • Kiyohito Iigaya
    • , Madalena S. Fonseca
    •  & Peter Dayan
  • Article
    | Open Access

    Theta oscillations are implicated in memory formation. Here, the authors show that low-theta oscillations in the hippocampus are differentially modulated between each hemisphere, with oscillations in the left increasing when successfully learning object–location pairs and in the right during spatial navigation.

    • Jonathan Miller
    • , Andrew J. Watrous
    •  & Joshua Jacobs
  • Article
    | Open Access

    Complex networks can be used to model brain networks. Here the authors identify the essential nodes in a model of a brain network and then validate these predictions by means of in vivo pharmacogenetic interventions. They find that the nucleus accumbens is a central region for brain integration.

    • Gino Del Ferraro
    • , Andrea Moreno
    •  & Hernán A. Makse
  • Article
    | Open Access

    Memory representations in cortex and hippocampus are reactivated during sharp-wave ripple (SWR) events. Here, the authors show that, in a familiar environment, this activity preferentially links spatially selective hippocampal cells and task general PFC representations, pointing to a potential neural mechanism for generalization of individual experiences.

    • Jai Y. Yu
    • , Daniel F. Liu
    •  & Loren M. Frank
  • Article
    | Open Access

    Prefrontal cortex is involved in flexibly learning the correct behavioural strategies but the neural correlates of this process are not well understood. Here the authors show that reinforcement for a correct decision at behavioural transitions evokes ensemble firing patterns related to prior events.

    • Silvia Maggi
    • , Adrien Peyrache
    •  & Mark D. Humphries
  • Article
    | Open Access

    Early childhood deprivation such as institutionalization can greatly affect early development. Here, the authors study children who were raised in institutions but later randomly placed in foster care vs. not, to understand how early-life deprivation affects associative learning in adolescence.

    • Margaret A. Sheridan
    • , Katie A. McLaughlin
    •  & Charles A. Nelson
  • Article
    | Open Access

    Feeding-relevant vagal signaling occurs between the gastrointestinal tract and the brain, but it is unclear if this pathway influences cognitive processes. This study shows that endogenous gastrointestinal derived vagal sensory signaling promotes hippocampal-dependent memory function via a multi-order brainstem–septal pathway.

    • Andrea N. Suarez
    • , Ted M. Hsu
    •  & Scott E. Kanoski
  • Article
    | Open Access

    Trial and error learning requires the brain to generate expectations and match them to outcomes, yet whether this occurs for semantic learning is unclear. Here, authors show that the brain encodes the degree to which new factual information violates expectations, which in turn determines whether information is encoded in long-term memory.

    • Alex Pine
    • , Noa Sadeh
    •  & Avi Mendelsohn
  • Article
    | Open Access

    Emotional memory can change when retrieved, yet the conditions under which this can occur are not fully described. Here, authors show that taking a pill of propranolol taken during a specific time window can change the expression of fear memory in a person, and that sleep is necessary to forget learned fear.

    • Merel Kindt
    •  & Marieke Soeter
  • Article
    | Open Access

    Detailed memories are transformed into gist-like memories over time. Here, the authors report that this change is linked to a time-dependent reorganization within the hippocampus, such that anterior activity supporting memory specificity declines over time while posterior activity patterns carrying gist representations remain more stable.

    • Lisa C. Dandolo
    •  & Lars Schwabe
  • Article
    | Open Access

    When perceiving new stimuli, organisms need to distinguish between threats versus harmless stimuli. Here, the authors find a set of cells in the lateral amygdala that is required to discriminate or generalize new auditory stimuli based on similarity to previously fear-associate sounds.

    • Anna Grosso
    • , Giulia Santoni
    •  & Benedetto Sacchetti
  • Article
    | Open Access

    Zona incerta (ZI) is an inhibitory subthalamic nucleus with diverse connectivity yet its functional importance has not been extensively studied. Here the authors report that ZI receives mPFC input and can modulate both innate and learned defensive behaviors via its inhibitory projection to the PAG.

    • Xiao-lin Chou
    • , Xiyue Wang
    •  & Huizhong Whit Tao
  • Article
    | Open Access

    Human speech and bird song requires the generation of precisely timed motor patterns. The authors show that zebra finches can learn to independently modify the duration of individual song segments and find that synfire chain networks are ideally suited to implement such flexible motor timing.

    • Cengiz Pehlevan
    • , Farhan Ali
    •  & Bence P. Ölveczky
  • Article
    | Open Access

    Odor-guided spatial behaviours are difficult to study due to the challenge of controlling chemical concentrations in space and time. Here the authors present a precise odor delivery system to generate a olfactory virtual landscape that engages hippocampal place cells in mice.

    • Brad A. Radvansky
    •  & Daniel A. Dombeck
  • Article
    | Open Access

    Memory lapses can occur due to ineffective encoding, but it is unclear if targeted brain stimulation can improve memory performance. Here, authors use a closed-loop system to decode and stimulate periods of ineffective encoding, showing that stimulation of lateral temporal cortex can enhance memory.

    • Youssef Ezzyat
    • , Paul A. Wanda
    •  & Michael J. Kahana
  • Article
    | Open Access

    Computational studies have hinted that hippocampal subfields represent information differently. Here, the authors show that when retrieving items that share an episodic context, subfield CA1 represent similarities between items whereas CA2/3/dentate gyrus represents item-unique features.

    • Halle R. Dimsdale-Zucker
    • , Maureen Ritchey
    •  & Charan Ranganath
  • Article
    | Open Access

    Previous work has documented a slow form of memory generalization although a rapid one is demanded. Here the authors elucidate the role of the interhemispheric CA1-CA1 projection in a form of rapid generalization of contextual fear memory via gradual potentiation of these synapses over 24 h.

    • Heng Zhou
    • , Gui-Jing Xiong
    •  & Lin Xu
  • Article
    | Open Access

    Theta- and gamma-frequency oscillatory synchrony correlates with spatial working memory performance. Here the authors report increases in theta-gamma cross-frequency coupling as a compensatory mechism associated with better working memory performance in models of cognitive dysfunction in mice.

    • Makoto Tamura
    • , Timothy J. Spellman
    •  & Joshua A. Gordon
  • Article
    | Open Access

    Adolescence is associated with negative behaviors that are related to enhanced reward-related striatal activity, but it is unclear whether this activity could also be beneficial. Here, authors report longitudinal data showing that enhanced striatal activity is related with increased learning ability.

    • S. Peters
    •  & E. A. Crone
  • Article
    | Open Access

    Complex motor behaviors such as birdsong are learned through practice and are thought to depend on specific excitatory connectivity in premotor circuits. Here the authors show that song learning in Bengalese Finches is associated with enrichment of inhibitory network connectivity that can affect specific song features.

    • Mark N. Miller
    • , Chung Yan J. Cheung
    •  & Michael S. Brainard
  • Article
    | Open Access

    While non-caloric artificial sweeteners (NAS) are used as food additives, it’s unclear whether animals perceive NAS as positive or negative percept. Here, Musso and colleagues show in Drosophila that NAS is a negative percept, encoded in a new type of memory.

    • Pierre-Yves Musso
    • , Aurélie Lampin-Saint-Amaux
    •  & Thomas Preat
  • Article
    | Open Access

    Previous studies have shown short-term plasticity in single neurons or local field potentials during brain-machine interface (BMI) training. Here the authors report long-term changes in functional connectivity of motor cortex neuronal ensemble activity as chronically amputated monkeys learn to operate a BMI.

    • Karthikeyan Balasubramanian
    • , Mukta Vaidya
    •  & Nicholas G. Hatsopoulos
  • Article
    | Open Access

    Synchronous neural activity is related with memory encoding and retrieval, but it is not clear whether this happens across the whole brain. Here, authors use intracranial recordings to show that gamma networks are largely asynchronous, desynchronizing while theta synchronizes during memory encoding and retrieval.

    • E. A. Solomon
    • , J. E. Kragel
    •  & M. J. Kahana
  • Article
    | Open Access

    Making a good decision often requires the weighing of relative short-term rewards against long-term benefits, yet how the brain does this is not understood. Here, authors show that long-term beliefs are biased by reward experience and that dissociable brain regions facilitate both types of learning.

    • Adrian G. Fischer
    • , Sacha Bourgeois-Gironde
    •  & Markus Ullsperger
  • Article
    | Open Access

    Changes to subsets of dendritic spines are thought to be important for memory formation. Here, the authors develop a hybrid RNA/protein tool that allows for optogenetic stimulation of single synapses that have been tagged in an activity-dependent manner

    • Francesco Gobbo
    • , Laura Marchetti
    •  & Antonino Cattaneo
  • Article
    | Open Access

    The APOE4 allele is the leading risk factor for late-onset Alzheimer’s disease, but how it might contribute to the disease is not clear. Here the authors show that a mouse expressing the human APOE4 allele displays hyperactivity in the entorhinal cortex due to a decreased inhibitory tone, which may in part explain accelerated Alzheimer’s pathology in APOE4 carriers.

    • Tal Nuriel
    • , Sergio L. Angulo
    •  & Karen E. Duff
  • Article
    | Open Access

    Supramammillary nucleus (SuM) neurons have been studied in the context of REM sleep but their possible role in mediating wakefulness is not known. Here the authors elucidate the distinct functional contributions of three subpopulations in the SuM on electrographical and behavioral arousal in mice using genetically targeted approaches.

    • Nigel P. Pedersen
    • , Loris Ferrari
    •  & Patrick M. Fuller
  • Article
    | Open Access

    Though people are easily able to recall items in a category without mentioning a wrong exemplar, the mechanism underlying this ability is unknown. Here, authors use intracranial recordings to show that this ability is likely due to a selective increase in baseline neuronal activity in category-specific regions.

    • Yitzhak Norman
    • , Erin M. Yeagle
    •  & Rafael Malach
  • Article
    | Open Access

    It is not fully understood how intrusive or unwanted memories are regulated. Here the authors show that hippocampal GABA concentrations, and coupling between the dorsolateral prefrontal cortex and hippocampus, predict how well subjects can suppress unwanted memories when presented with a reminder.

    • Taylor W. Schmitz
    • , Marta M. Correia
    •  & Michael C. Anderson
  • Article
    | Open Access

    People often assume that other people share their preferences, but how exactly this bias manifests itself in learning and decision-making is unclear. Here, authors show that a person's own preferences influence learning in both social and non-social situations, and that this bias improves performance.

    • Tor Tarantola
    • , Dharshan Kumaran
    •  & Benedetto De Martino
  • Article
    | Open Access

    Different stages of sleep, marked by particular electroencephalographic (EEG) signatures, have been linked to memory consolidation, but underlying mechanisms are poorly understood. Here, the authors show that dendritic calcium synchronisation correlates with spindle-rich sleep phases.

    • Julie Seibt
    • , Clément J. Richard
    •  & Matthew E. Larkum
  • Article
    | Open Access

    Spike timing dependent plasticity (STDP) has been studied extensively in slices but whether such pairings can induce plasticity in vivo is not known. Here the authors report an experimental paradigm that achieves bidirectional corticostriatal STDP in vivo through modulation by behaviourally relevant reinforcement signals, mediated by dopamine and adenosine signaling.

    • Simon D. Fisher
    • , Paul B. Robertson
    •  & John N.J. Reynolds
  • Article
    | Open Access

    Neurons in the retrosplenial cortex (RSC) encode spatial and navigational signals. Here the authors use calcium imaging to show that, similar to the hippocampus, RSC neurons also encode place cell-like activity in a sparse orthogonal representation, partially anchored to the allocentric cues on the linear track.

    • Dun Mao
    • , Steffen Kandler
    •  & Vincent Bonin
  • Article
    | Open Access

    Intra-hippocampal circuits are essential for associating a background context with behaviorally salient stimuli and involve cholinergic modulation at SST+ interneurons. Here the authors show that the salience of the background context memory is modulated through muscarinic activation of NPY+ hilar perforant path associated interneurons and NPY signaling in the dentate gyrus.

    • Syed Ahsan Raza
    • , Anne Albrecht
    •  & Oliver Stork
  • Article
    | Open Access

    Motor learning induces structural and functional reorganization in upper layers of motor cortex. Here the authors show that neuronal ensembles in the output layer 5b exhibit temporal dynamics during skilled learning that progressively becomes well-aligned to movement in a dopamine dependent manner.

    • Qian Li
    • , Ho Ko
    •  & Wing-Ho Yung
  • Article
    | Open Access

    Neurons in the lateral prefrontal cortex are known to encode visual features as well as maintain them in working memory. Here the authors report that LPFC neurons encode both perceived and memorized visual features in diverse combinations and the population activity reliably decodes as well as differentiates between these two representations.

    • Diego Mendoza-Halliday
    •  & Julio C. Martinez-Trujillo