Building machines that adapt and compute like brains

Building machines that learn and think like humans is essential not only for cognitive science, but also for computational neuroscience, whose ultimate goal is to understand how cognition is implemented in biological brains. A new cognitive computational neuroscience should build cognitive-level and neural- level models, understand their relationships, and test both types of models with both brain and behavioral data.Comment: Commentary on: Lake BM, Ullman TD, Tenenbaum JB, Gershman SJ. (2017) Building machines that learn and think like people. Behavioral and Brain Sciences, 4

Premature recruitment of oocyte pool and increased mTOR activity in Fmr1 knockout mice and reversal of phenotype with rapamycin.

While mutations in the fragile X mental retardation-1 (FMR1) gene are associated with varying reproductive outcomes in females, the effects of a complete lack of FMR1 expression are not known. Here, we studied the ovarian and reproductive phenotypes in an Fmr1 knockout (KO) mouse model and the role of mammalian target of rapamycin (mTOR) signaling. Breeding, histologic and mTOR signaling data were obtained at multiple time points in KO and wild type (WT) mice fed a control or rapamycin (mTOR inhibitor) diet. KO mice showed an earlier decline in ovarian reserve than WT mice with an increased proportion of activated follicles. mTOR and phosphorylated S6 kinase (p-S6K) levels, a measure of downstream mTOR signaling, were elevated in the KO ovaries. Rapamycin blocked these effects in KO mice, and increased the primordial follicle pool and age of last litter in WT mice. Our data demonstrates an early decline in reproductive capacity in Fmr1 KO mice and proposes that premature recruitment of the primordial pool via altered mTOR signaling may be the mechanism. Reversal of phenotypes and protein levels in rapamycin-treated KO mice, as well as increased reproductive lifespan of rapamycin-fed WT mice, suggest the mTOR pathway as a potential therapeutic target

A multilevel account of hippocampal function in spatial and concept learning: Bridging models of behavior and neural assemblies

A complete neuroscience requires multilevel theories that address phenomena ranging from higher-level cognitive behaviors to activities within a cell. We propose an extension to the level of mechanism approach where a computational model of cognition sits in between behavior and brain: It explains the higher-level behavior and can be decomposed into lower-level component mechanisms to provide a richer understanding of the system than any level alone. Toward this end, we decomposed a cognitive model into neuron-like units using a neural flocking approach that parallels recurrent hippocampal activity. Neural flocking coordinates units that collectively form higher-level mental constructs. The decomposed model suggested how brain-scale neural populations coordinate to form assemblies encoding concept and spatial representations and why so many neurons are needed for robust performance at the cognitive level. This multilevel explanation provides a way to understand how cognition and symbol-like representations are supported by coordinated neural populations (assemblies) formed through learning

The Stream-Stream Collision after the Tidal Disruption of a Star Around a Massive Black Hole

A star can be tidally disrupted around a massive black hole. It has been known that the debris forms a precessing stream, which may collide with itself. The stream collision is a key process determining the subsequent evolution of the stellar debris: if the orbital energy is efficiently dissipated, the debris will eventually form a circular disk (or torus). In this paper, we have numerically studied such stream collision resulting from the encounter between a 10^6 Msun black hole and a 1 Msun normal star with a pericenter radius of 100 Rsun. A simple treatment for radiative cooling has been adopted for both optically thick and thin regions. We have found that approximately 10 to 15% of the initial kinetic energy of the streams is converted into thermal energy during the collision. The angular momentum of the incoming stream is increased by a factor of 2 to 3, and such increase, together with the decrease in kinetic energy, significantly helps the circularization process. Initial luminosity burst due to the collision may reach as high as 10^41 erg/sec in 10^4 sec, after which the luminosity increases again (but slowly this time) to a steady value of a few 10^40 erg/sec in a few times of 10^5 sec. The radiation from the system is expected to be close to Planckian with effective temperature of \~10^5K.Comment: 19 pages including 12 figures; Accepted for publication in Ap

Cytotoxic Complexes of Sodium Oleate with β-Lactoglobulin

pre-printA complex of α-lactalbumin and oleic acid has previously been shown to induce apoptosis in cancer cells in a number of in vitro and in vivo trials. This complex is called HAMLET or BAMLET, depending on the origin of α-la (human/bovine alpha-lactalbumin made lethal to tumour cells). In the current study, it was shown that bovine β-lactoglobulin (β-lg), upon binding sodium oleate (NaOle), the salt of oleic acid, also acquires cytotoxicity towards tumour cells (human monocytic cells U937), analogously to HAMLET/BAMLET complexes. The properties of the complex were characterized using FIR spectroscopy, HPLC and SDS-PAGE. It was shown that the level of covalent oligomerization (dimers and trimers) of β-lg increased with increasing the molar ratio of sodium oleate NaOle:β-lg in the preparation procedure. At the same time, increasing the molar ratio of NaOle:β-lg increased the cytotoxicity of the complex. The increase in cytotoxicity appeared to be dependent on the amount of bound NaOle in the complex, but not on the content of multimeric forms of β-lg. The NaOle/β-lg complex also showed similarity with BAMLET in penetrating the cell membrane and co-localizing with the cell nucleus. Furthermore, DNA fragmentation studies suggested that tumour cells (U937) treated with the complex died by apoptosis, as in the case of BAMLET, and healthy cells appeared to be less affected by treatment, as shown with model rat adrenal pheochromocytoma cells PC12. In conclusion, β-lg and NaOle can form complexes with apoptosis-inducing qualities comparable to those of BAMLET.The work was funded by the Irish Dairy Research Trust and The Department of Agriculture (Food Institutional Research Measure – FIRM project 08RDTMFRC650) under the National Development Plan 2007-2013. K. Lišková was funded under the TeagascWalsh Fellowship Scheme

Auditory stimulus timing influences perceived duration of co-occurring visual stimuli

There is increasing interest in multisensory influences upon sensory-specific judgments, such as when auditory stimuli affect visual perception. Here we studied whether the duration of an auditory event can objectively affect the perceived duration of a co-occurring visual event. On each trial, participants were presented with a pair of successive flashes and had to judge whether the first or second was longer. Two beeps were presented with the flashes. The order of short and long stimuli could be the same across audition and vision (audio–visual congruent) or reversed, so that the longer flash was accompanied by the shorter beep and vice versa (audio–visual incongruent); or the two beeps could have the same duration as each other. Beeps and flashes could onset synchronously or asynchronously. In a further control experiment, the beep durations were much longer (tripled) than the flashes. Results showed that visual duration discrimination sensitivity (d′) was significantly higher for congruent (and significantly lower for incongruent) audio–visual synchronous combinations, relative to the visual-only presentation. This effect was abolished when auditory and visual stimuli were presented asynchronously, or when sound durations tripled those of flashes. We conclude that the temporal properties of co-occurring auditory stimuli influence the perceived duration of visual stimuli and that this can reflect genuine changes in visual sensitivity rather than mere response bias