Main Menu (Mobile)- Block

Main Menu - Block

custom | custom

Search Results

general_search_page-panel_pane_1 | views_panes

24 Janelia Publications

Showing 21-24 of 24 results
Your Criteria:
    05/30/16 | Hippocampal global remapping for different sensory modalities in flying bats.
    Geva-Sagiv M, Romani S, Las L, Ulanovsky N
    Nature Neuroscience. 2016 May 30;19(7):952-8. doi: 10.1038/nn.4310

    Hippocampal place cells encode the animal's spatial position. However, it is unknown how different long-range sensory systems affect spatial representations. Here we alternated usage of vision and echolocation in Egyptian fruit bats while recording from single neurons in hippocampal areas CA1 and subiculum. Bats flew back and forth along a linear flight track, employing echolocation in darkness or vision in light. Hippocampal representations remapped between vision and echolocation via two kinds of remapping: subiculum neurons turned on or off, while CA1 neurons shifted their place fields. Interneurons also exhibited strong remapping. Finally, hippocampal place fields were sharper under vision than echolocation, matching the superior sensory resolution of vision over echolocation. Simulating several theoretical models of place-cells suggested that combining sensory information and path integration best explains the experimental sharpening data. In summary, here we show sensory-based global remapping in a mammal, suggesting that the hippocampus does not contain an abstract spatial map but rather a 'cognitive atlas', with multiple maps for different sensory modalities.

    View Publication Page
    03/15/16 | Practice makes perfect in memory recall.
    Romani S, Katkov M, Tsodyks M
    Learning & Memory (Cold Spring Harbor, N.Y.). 2016 Apr;23(4):169-73. doi: 10.1101/lm.041178.115

    A large variability in performance is observed when participants recall briefly presented lists of words. The sources of such variability are not known. Our analysis of a large data set of free recall revealed a small fraction of participants that reached an extremely high performance, including many trials with the recall of complete lists. Moreover, some of them developed a number of consistent input-position-dependent recall strategies, in particular recalling words consecutively ("chaining") or in groups of consecutively presented words ("chunking"). The time course of acquisition and particular choice of positional grouping were variable among participants. Our results show that acquiring positional strategies plays a crucial role in improvement of recall performance.

    View Publication Page
    12/17/15 | Neural Network Model of Memory Retrieval.
    Recanatesi S, Katkov M, Romani S, Tsodyks M
    Frontiers in Computational Neuroscience. 2015 Dec 17;9:149. doi: 10.3389/fncom.2015.00149

    Human memory can store large amount of information. Nevertheless, recalling is often a challenging task. In a classical free recall paradigm, where participants are asked to repeat a briefly presented list of words, people make mistakes for lists as short as 5 words. We present a model for memory retrieval based on a Hopfield neural network where transition between items are determined by similarities in their long-term memory representations. Meanfield analysis of the model reveals stable states of the network corresponding (1) to single memory representations and (2) intersection between memory representations. We show that oscillating feedback inhibition in the presence of noise induces transitions between these states triggering the retrieval of different memories. The network dynamics qualitatively predicts the distribution of time intervals required to recall new memory items observed in experiments. It shows that items having larger number of neurons in their representation are statistically easier to recall and reveals possible bottlenecks in our ability of retrieving memories. Overall, we propose a neural network model of information retrieval broadly compatible with experimental observations and is consistent with our recent graphical model (Romani et al., 2013).

    View Publication Page
    02/01/15 | Theta sequences are essential for internally generated hippocampal firing fields.
    Wang Y, Romani S, Lustig B, Leonardo A, Pastalkova E
    Nature Neuroscience. 2015 Feb;18(2):282-8. doi: 10.1038/nn.3904

    Sensory cue inputs and memory-related internal brain activities govern the firing of hippocampal neurons, but which specific firing patterns are induced by either of the two processes remains unclear. We found that sensory cues guided the firing of neurons in rats on a timescale of seconds and supported the formation of spatial firing fields. Independently of the sensory inputs, the memory-related network activity coordinated the firing of neurons not only on a second-long timescale, but also on a millisecond-long timescale, and was dependent on medial septum inputs. We propose a network mechanism that might coordinate this internally generated firing. Overall, we suggest that two independent mechanisms support the formation of spatial firing fields in hippocampus, but only the internally organized system supports short-timescale sequential firing and episodic memory.

    View Publication Page