Ventro-dorsal hippocampal pathway gates novelty-induced contextual memory formation

Novelty facilitates formation of memories. The detection of novelty and storage of contextual memories are both mediated by the hippocampus, yet the mechanisms that link these two functions remain to be defined. Dentate granule cells (GCs) of the dorsal hippocampus fire upon novelty exposure forming engrams of contextual memory. However, their key excitatory inputs from the entorhinal cortex are not responsive to novelty and are insufficient to make dorsal GCs fire reliably. Here we uncover a powerful glutamatergic pathway to dorsal GCs from ventral hippocampal mossy cells (MCs) that relays novelty, and is necessary and sufficient for driving dorsal GCs activation. Furthermore, manipulation of ventral MCs activity bidirectionally regulates novelty-induced contextual memory acquisition. Our results show that ventral MCs activity controls memory formation through an intra-hippocampal interaction mechanism gated by novelty

Lightweight and Efficient Neural Natural Language Processing with Quaternion Networks

Many state-of-the-art neural models for NLP are heavily parameterized and thus memory inefficient. This paper proposes a series of lightweight and memory efficient neural architectures for a potpourri of natural language processing (NLP) tasks. To this end, our models exploit computation using Quaternion algebra and hypercomplex spaces, enabling not only expressive inter-component interactions but also significantly ($75\%$) reduced parameter size due to lesser degrees of freedom in the Hamilton product. We propose Quaternion variants of models, giving rise to new architectures such as the Quaternion attention Model and Quaternion Transformer. Extensive experiments on a battery of NLP tasks demonstrates the utility of proposed Quaternion-inspired models, enabling up to $75\%$ reduction in parameter size without significant loss in performance.Comment: ACL 201

Valence, Arousal, and Gender Effect on Olfactory Cortical Network Connectivity: a study using Dynamic Causal Modeling for EEG

The cortical network including the piriform (PC), orbitofrontal (OFC), and entorhinal (EC) cortices allows the complex processing of behavioral, cognitive, and context-related odor information and represents an access gate to the subcortical limbic regions. Among the several factors that influence odor processing, their hedonic content and gender differences play a relevant role. Here, we investigated how these factors influence EEG effective connectivity among the mentioned brain regions during emotional olfactory stimuli. To this aim, we acquired EEG data from twenty-one healthy volunteers, during a passive odor task of odorants with different valence. We used Dynamic Causal Modeling (DCM) for EEG and Parametric Empirical Bayes (PEB) to investigate the modulatory effects of odors’ valence on the connectivity strengths of the PC-EC-OFC network. Moreover, we controlled for the influence of arousal and gender on such modulatory effects. Our results highlighted the relevant role of the forward and backward PC-EC connections in odor’s brain processing. On the one hand, the EC-to-PC connection was inhibited by both pleasant and unpleasant odors, but not by the neutral one. On the other hand, the PC-to-EC forward connection was found to be modulated (posterior probability (Pp)>0.95) by the arousal level associated with an unpleasant odor. Finally, the whole network dynamics showed several significant gender-related differences (Pp>0.95) suggesting a better ability in odor discrimination for the female gender

Auditory associative learning and its neural correlates in the auditory midbrain

Interpreting the meaning of environmental stimuli to generate optimal behavioral responses is essential for survival. Simply sensing a sound, without accessing prior knowledge in the brain, will not benefit behavior. How sensation and memory interact to form behavior is one of the fundamental questions in the field of neuroscience. In this thesis, I have addressed this question from two perspectives: I investigated the behavioral outcome of this interaction using discrimination, and the circuit underlying this interaction using electrophysiological recordings in the behaving mouse. Behaviorally, we found that the physical difference between to-be-discriminated sounds, had a constraining effect on discrimination. This effect occurred even though physical differences were significantly larger than reported discrimination limens, thus reflecting a high overlap between the memory traces of the relevant stimuli. The results suggest a strong role of pre-wired tonotopic organization and the involvement of peripheral stations with wider tuning (Ehret and Merzenich, 1985; Taberner and Liberman, 2005). To further understand the influence of sensation on behavior, we tested the interaction between sound features with generalization. Using sounds that differed in two dimensions, we found that bi-dimensional generalization can be either biased towards a single dimension or an integration of both. Whether it was one or the other depended on the two dimensions used. As the first convergence station in the auditory system (Casseday et al., 2002), the role of the inferior colliculus in encoding behavioral relevant information is not well understood. Recording from freely behaving mouse, we found task engagement modulated neural activity in the IC in a stimulus-specific manner. Our lab found previously that relevant sound exposure induced enhancement in neural activity and shifts in tonal representation in the IC (Cruces-Solís et al., 2018). As a continuation, we found that movement-sound association is essential for this plasticity. Furthermore, recording in freely behaving mice also found that this association modulated the ongoing LFP in the IC, suggesting a new role of IC in filtering movement-related acoustic stimuli. To conclude, our results support the view that the IC is not simply an auditory structure that relays auditory information into the cortex, but plays important role in interpreting the meaning of the sound. The new role of IC in encoding movement-related information suggests that the filtering function of the auditory system starts already in subcortical stages of the auditory pathway

The representations of arithmetic fact knowledge in memory and their development

The present dissertation focused on one aspect of mathematical knowledge: fact knowledge. More specifically, we focused on the relation between the memory representations of simple multiplication and division facts (both operands < 10), as this remains a debated issue. This dissertation contains an introductory chapter (Chapter 1), four empirical chapters (Chapters 2-5) and a general discussion (Chapter 6). In Chapter 2, we used the number-matching task (measuring automatic activation of fact knowledge) and we expected to find stronger interference effects for division problems (compared to inverse division problems) if an independent division network exists. This was not confirmed as both problem types led to automatic activation. In two subsequent studies, we focused on developmental changes in multiplication and division performance. In Chapter 3, we showed that the formation of a memory network of multiplication facts is a fast-developing process. This study laid out the foundations for Chapter 4, in which we investigated both multiplication and division performance from the moment a child acquires the multiplication and division tables until the end of fourth grade. All effects that have been robustly observed in adults were also observed in children, quickly after they acquired the tables. Moreover, all effects observed in multiplication performance were also present in division performance and strong developmental parallels between both operations were observed. These results are a necessary condition to exclude the existence of independent networks. In Chapter 5 we investigated adult multiplication and division performance by making use of a learning paradigm. Clear evidence for cross-operation transfer of learning was found, which is not in line with the idea of independent representations at high skill levels. Taken together, using different paradigms and different populations, the results of the present studies speak against the idea of independent memory networks for multiplication and division facts and show that it is more correct to consider multiplication and division as mutually dependent and interacting skills

Power System Load Modeling Using A Weighted Optimal Linear Associative Memory (Olam)

Power system load models are very powerful tools, which have a wide range of applications in the electric power industry. These uses include scheduling system maintenance, monitoring load management policies, helping with the generator commitment problem by providing short-term forecasts, and aiding system planning [4]. Further, Power System Load Modeling is a technique used to model a power system and other essentials for the assessment of stability. In today’s datacenters, power consumption is a major issue. Storage usually typically comprises a large percentage of a datacenter’s power. Therefore, without mentioning that managing, understanding, and reducing storage, power consumption is an essential aspect of any efforts that address the total power consumption of datacenters. Moreover, according to [16], power system load models have a wide range of applications in the electric power industry including load management policy monitoring, such as aiding with system planning by providing long-term forecasts, short-term forecasts, and others including assisting with the generator commitment problem

The cognitive cell: bacterial behavior reconsidered

Research on how bacteria adapt to changing environments underlies the contemporary biological understanding of signal transduction, and signal transduction provides the foundation of the information-processing approach that is the hallmark of the ‘cognitive revolution,’ which began in the mid-20th century. Yet cognitive scientists largely remain oblivious to research into microbial behavior that might provide insights into problems in their own domains, while microbiologists seem equally unaware of the potential importance of their work to understanding cognitive capacities in multicellular organisms, including vertebrates. Evidence in bacteria for capacities encompassed by the concept of cognition is reviewed. Parallels exist not only at the heuristic level of functional analogue, but also at the level of molecular mechanism, evolution and ecology, which is where fruitful cross-fertilization among disciplines might be found