Papers for the month of March 2015

Galvan E.J., Pérez-Rosello T., Gómez-Lira G., Lara E., Gutiérrez R.

"Synapse-specific compartmentalization of signaling cascades for LTP induction in CA3 interneurons"
Neuroscience, 290:332-345

Mouse over here for a brief summary or click to open article in a new tab.The aspiny dendrites of hippocampal area CA3 interneurons are able to compartmentalize the initial steps in the signaling transduction cascades implicated in the induction of two mechanistically distinct forms of Hebbian LTP at Recurrent Collateral and Mossy Fiber synapses.Functionally, synapse-specific compartmentalization of these two forms of LTP in the aspiny dendrite enables CA3 interneurons to participate in the dual mnemonic processes of pattern separation and pattern completion.

Urban-Ciecko, Joanna and Fanselow, Erika E.

"Neocortical Somatostatin Neurons Reversibly Silence Excitatory Transmission via GABAb Receptors"
Current Biology, 25(6):722-31

Mouse over here for a brief summary or click to open article in a new tab.Excitatory transmission is suppressed in active neocortical networks, where spontaneous activity of both excitatory and inhibitory neurons is present. This suppression -- which can in some cases completely silence verified synapses -- is mediated via GABAb receptors, through the release of GABA from somatostatin interneurons. Optogenentic silencing of somatostatin neuron firing enhances EPSP efficacy, revealing synapses and increasing the amplitude of excitatory transmission.

Gabay, Y., Vakil, E., Schiff, R.

"Probabilistic Category Learning in Developmental Dyslexia: Evidence From Feedback and Paired-Associate Weather Prediction Tasks"

Mouse over here for a brief summary or click to open article in a new tab.We demonstrate that the ability to learn probabilistic classification tasks with feedback is not selectively impaired in dyslexia. Rather, it seems that the probabilistic nature of the classification tasks hampers learning among dyslexics. The results are consistent with general procedural learning impairments in dyslexia.

Bowman, S.L., Soohoo, A.L., Shiwarski, D.J., Schulz, S., Pradhan, A.A.,

"Cell-Autonomous Regulation of Mu-Opioid Receptor Recycling by Substance P."
Cell Reports, 10:1925–1936

Mouse over here for a brief summary or click to open article in a new tab.How neuronal connections change the behavior of neurons is the next step of brain mapping. We show that neuropeptides mediating pain can sensitize sensory neurons to opioids in a selective manner by regulating the surface expression of opioid receptors. This reduces acute tolerance to endorphins, but not morphine, in mice, providing an example of how the pain and analgesic pathways interact to fine-tune the responses of sensory neurons.

Chmura, J., Presson, N., Benso, S., Puccio, A. M., Fissel, K., Hachey, R., Braun, E., Okonkwo, D. O.

"A High-Definition Fiber Tracking Report for Patients With Traumatic Brain Injury and Their Doctors"
Military Medicine, 180:122-134

Mouse over here for a brief summary or click to open article in a new tab.We have developed a tablet-based application, the High-Definition Fiber Tracking Report App, to enable clinicians and patients in research studies to see and understand damage from Traumatic Brain Injury (TBI) by viewing 2-dimensional and 3-dimensional images of their brain, with a focus on white matter tracts with quantitative metrics.

Snyder, Adam C.; Morais, Michael J.; Willis, Cory.

"Global network influences on local functional connectivity"
Nature Neuroscience, 0:0

Mouse over here for a brief summary or click to open article in a new tab.To better understand how neurons interact across disparate spatial scales, we measured spike count correlation, an index of functional connectivity with computational relevance, and EEG oscillations, which have been linked to various cognitive functions. We found a non-monotonic relationship between EEG oscillation amplitude and spike count correlation, contrary to the intuitive expectation of a direct relationship. We also found that spike count correlation explained nonlinearities in the relationship between EEG oscillations and response time in a spatial selective attention task.

Pasquereau B.

"Dopamine neurons encode errors in predicting movement trigger occurrence."
The Journal of Neurophysicology, 113(4):1110-23

Mouse over here for a brief summary or click to open article in a new tab.The capacity to anticipate the timing of events in a dynamic environment allows us to optimize the processes necessary for perceiving, attending to, and responding to them. Such anticipation requires neuronal mechanisms that track the passage of time and use this representation, combined with prior experience, to estimate the likelihood that an event will occur. (i.e., the event's "hazard rate"). Although hazard-like ramps in activity have been observed in several cortical areas in preparation for movement, it remains unclear how such time-dependent probabilities are estimated to optimize response performance. We studied the spiking activity of dopamine neurons in the substantia nigra pars compacta of monkeys during an arm-reaching task for which the foreperiod preceding the "go" signal varied randomly along a uniform distribution. After extended training, the monkeys' reaction times correlated inversely with foreperiod duration, reflecting a progressive anticipation of the go signal according to its hazard rate. Many dopamine neurons modulated their firing rates as predicted by a succession of hazard-related prediction errors. First, as time passed during the foreperiod, slowly decreasing anticipatory activity tracked the elapsed time as if encoding negative prediction errors. Then, when the go signal appeared, a phasic response encoded the temporal unpredictability of the event, consistent with a positive prediction error. Neither the anticipatory nor the phasic signals were affected by the anticipated magnitudes of future reward or effort, or by parameters of the subsequent movement. These results are consistent with the notion that dopamine neurons encode hazard-related prediction errors independently of other information.

Zimnik AJ, Nora GJ, Desmurget M

"Movement-Related Discharge in the Macaque Globus Pallidus during High-Frequency Stimulation of the Subthalamic Nucleus."
The Journal of Neuroscience, 35(9):3978-89

Mouse over here for a brief summary or click to open article in a new tab.http://Deep brain stimulation (DBS) of the subthalamic nucleus (STN-DBS) has largely replaced ablative therapies for Parkinson's disease. Because of the similar efficacies of the two treatments, it has been proposed that DBS acts by creating an "informational lesion," whereby pathologic neuronal firing patterns are replaced by low-entropy, stimulus-entrained firing patterns. The informational lesion hypothesis, in its current form, states that DBS blocks the transmission of all information from the basal ganglia, including both pathologic firing patterns and normal, task-related modulations in activity. We tested this prediction in two healthy rhesus macaques by recording single-unit spiking activity from the globus pallidus (232 neurons) while the animals completed choice reaction time reaching movements with and without STN-DBS. Despite strong effects of DBS on the activity of most pallidal cells, reach-related modulations in firing rate were equally prevalent in the DBS-on and DBS-off states. This remained true even when the analysis was restricted to cells affected significantly by DBS. In addition, the overall form and timing of perimovement modulations in firing rate were preserved between DBS-on and DBS-off states in the majority of neurons (66%). Active movement and DBS had largely additive effects on the firing rate of most neurons, indicating an orthogonal relationship in which both inputs contribute independently to the overall firing rate of pallidal neurons. These findings suggest that STN-DBS does not act as an indiscriminate informational lesion but rather as a filter that permits task-related modulations in activity while, presumably, eliminating the pathological firing associated with parkinsonism.


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