Neural Intrinsic timescales in the macaque dorsal premotor cortex predict the strength of spatial response coding

Our brain continuously receives information over multiple timescales that are differently processed across areas. In this study, we investigated the intrinsic timescale of neurons in the dorsal premotor cortex (PMd) of two rhesus macaques while performing a non-match-to-goal task. The task rule was to reject the previously chosen target and select the alternative one. We defined the intrinsic timescale as the decay constant of the autocorrelation structure computed during a baseline period of the task. We found that neurons with longer intrinsic timescale tended to maintain a stronger spatial response coding during a delay period. This result suggests that longer intrinsic timescales predict the functional role of PMd neurons in a cognitive task. Our estimate of the intrinsic timescale integrates an existing hierarchical model (Murray et al., 2014), by assigning to PMd a lower position than prefrontal cortex in the hierarchical ordering of the brain areas based on neurons' timescales

Development of a software trigger algorithm for electron identification using the NA62 RICH Cherenkov detector

The thesis focuses on the development of a new algorithm able to identify an electron Cherenkov ring using the NA62 Ring Imaging CHerenkov detector (RICH). The algorithm is developed to act as an online Level 1 trigger algorithm and its execution time is studied to make it as fast as possible. In parallel, an efficiency analysis of the official offline NA62 RICH multi-ring reconstruction algorithm is performed in case it will be used as an online trigger algorithm. Studies on the efficiency and the rejection factor of the trigger cut to select the lepton number violating process K + → π−e+e+ are described. Concerning the Level 1 trigger cut strategy, it is based on the use of the RICH detector only. Finally, a brief description of the NA62 PC-farm, where all the software trigger algorithms are implemented, is described

Intrinsic timescales across the basal ganglia

International audienceAbstract Recent studies have shown that temporal stability of the neuronal activity over time can be estimated by the structure of the spike-count autocorrelation of neuronal populations. This estimation, called the intrinsic timescale, has been computed for several cortical areas and can be used to propose a cortical hierarchy reflecting a scale of temporal receptive windows between areas. In this study, we performed an autocorrelation analysis on neuronal populations of three basal ganglia (BG) nuclei, including the striatum and the subthalamic nucleus (STN), the input structures of the BG, and the external globus pallidus (GPe). The analysis was performed during the baseline period of a motivational visuomotor task in which monkeys had to apply different amounts of force to receive different amounts of reward. We found that the striatum and the STN have longer intrinsic timescales than the GPe. Moreover, our results allow for the placement of these subcortical structures within the already-defined scale of cortical temporal receptive windows. Estimates of intrinsic timescales are important in adding further constraints in the development of computational models of the complex dynamics among these nuclei and throughout cortico-BG-thalamo-cortical loops

Autocorrelation structure in the macaque dorsolateral, but not orbital or polar, prefrontal cortex predicts response-coding strength in a visually cued strategy task

In previous work, we studied the activity of neurons in the dorsolateral (PFdl), orbital (PFo), and polar (PFp) prefrontal cortex while monkeys performed a strategy task with 2 spatial goals. A cue instructed 1 of 2 strategies in each trial: stay with the previous goal or shift to the alternative goal. Each trial started with a fixation period, followed by a cue. Subsequently, a delay period was followed by a “go” signal that instructed the monkeys to choose one goal. After each choice, feedback was provided. In this study, we focused on the temporal receptive fields of the neurons, as measured by the decay in autocorrelation (time constant) during the fixation period, and examined the relationship with response and strategy coding. The temporal receptive field in PFdl correlated with the response-related but not with the strategy-related modulation in the delay and the feedback periods: neurons with longer time constants in PFdl tended to show stronger and more prolonged response coding. No such correlation was found in PFp or PFo. These findings demonstrate that the temporal specialization of neurons for temporally extended computations is predictive of response coding, and neurons in PFdl, but not PFp or PFo, develop such predictive properties

Search for heavy neutral lepton production in K+K^+ decays

A search for heavy neutral lepton production in $K^+$ decays using a data sample collected with a minimum bias trigger by the NA62 experiment at CERN in 2015 is reported. Upper limits at the $10^{-7}$ to $10^{-6}$ level are established on the elements of the extended neutrino mixing matrix $|U_{\ell 4}|^2$ ($\ell=e,\mu$) for heavy neutral lepton mass in the range $170-448~{\rm MeV}/c^2$. This improves on the results from previous production searches in $K^+$ decays, setting more stringent limits and extending the mass range.A search for heavy neutral lepton production in K+ decays using a data sample collected with a minimum bias trigger by the NA62 experiment at CERN in 2015 is reported. Upper limits at the 10−7 to 10−6 level are established on the elements of the extended neutrino mixing matrix |Ue4|2 and |Uμ4|2 for heavy neutral lepton mass in the ranges 170–448 MeV/ c2 and 250–373 MeV/ c2 , respectively. This improves on the previous limits from HNL production searches over the whole mass range considered for |Ue4|2 , and above 300 MeV/ c2 for |Uμ4|2

First search for K+→π+ννˉK^+\rightarrow\pi^+\nu\bar{\nu} using the decay-in-flight technique

International audienceThe NA62 experiment at the CERN SPS reports the first search for K+→π+νν¯ using the decay-in-flight technique, based on a sample of 1.21×1011 K+ decays collected in 2016. The single event sensitivity is 3.15×10−10 , corresponding to 0.267 Standard Model events. One signal candidate is observed while the expected background is 0.152 events. This leads to an upper limit of 14×10−10 on the K+→π+νν¯ branching ratio at 95% CL

A search for the K+→μ−νe+e+K^+\to\mu^-\nu e^+e^+ decay

A search for the $K^+\to\mu^-\nu e^+e^+$ decay, forbidden within the Standard Model by either lepton number or lepton flavour conservation depending on the flavour of the emitted neutrino, has been performed using the dataset collected by the NA62 experiment at CERN in 2016--2018. An upper limit of $8.1\times 10^{-11}$ is obtained for the decay branching fraction at 90% CL, improving by a factor of 250 over the previous search

Measurement of the very rare K+→π+ννˉK^+\rightarrow\pi^+\nu\bar{\nu} decay

The NA62 experiment reports the branching ratio measurement BR$(K^+ \rightarrow \pi^+ \nu\bar{\nu}) = (10.6^{+4.0}_{-3.4} |_{\rm stat} \pm 0.9_{\rm syst}) \times 10 ^{-11}$ at 68% CL, based on the observation of 20 signal candidates with an expected background of 7.0 events from the total data sample collected at the CERN SPS during 2016-2018. This provides evidence for the very rare $K^+ \rightarrow \pi^+ \nu\bar{\nu}$ decay, observed with a significance of 3.4$\sigma$. The experiment achieves a single event sensitivity of $(0.839\pm 0.054)\times 10^{-11}$, corresponding to 10.0 events assuming the Standard Model branching ratio of $(8.4\pm1.0)\times10^{-11}$. This measurement is also used to set limits on BR($K^+ \to \pi^+ X$), where $X$ is a scalar or pseudo-scalar particle. Details are given of the analysis of the 2018 data sample, which corresponds to about 80% of the total data sample