Fundamental bounds on learning performance in neural circuits, bioRxiv, 2019-01-01
How does the size of a neural circuit influence its learning performance? Intuitively, we expect the learning capacity of a neural circuit to grow with the number of neurons and synapses. Larger brains tend to be found in species with higher cognitive function and learning ability. Similarly, adding connections and units to artificial neural networks can allow them to solve more complex tasks. However, we show that in a biologically relevant setting where synapses introduce an unavoidable amount of noise, there is an optimal size of network for a given task. Beneath this optimal size, our analysis shows how adding apparently redundant neurons and connections can make tasks more learnable. Therefore large neural circuits can either devote connectivity to generating complex behaviors, or exploit this connectivity to achieve faster and more precise learning of simpler behaviors. Above the optimal network size, the addition of neurons and synaptic connections starts to impede learning performance. This suggests that overall brain size may be constrained by the need to learn efficiently with unreliable synapses, and may explain why some neurological learning deficits are associated with hyperconnectivity. Our analysis is independent of specific learning rules and uncovers fundamental relationships between learning rate, task performance, network size and intrinsic noise in neural circuits.
biorxiv neuroscience 0-100-users 2019Loud music and the specific sound stress open the blood-brain barrier new fundamental, biomedical, and social aspects, bioRxiv, 2019-01-01
AbstractThe blood-brain barrier (BBB) poses a significant challenge for drug brain delivery. The limitation of our knowledge about the nature of BBB explains the slow progress in the therapy of brain diseases and absence of methods for drug brain delivery in the clinical practice.Here we show that BBB opens for lowhigh weight molecules and nanocarriers after exposure of loud musicsound of 90 dB and 100 dB (regardless its frequency) as being easily produced by MP3MP4 players, kitchen appliances, loudspeakers at concerts. The role of sound, sound-induced stress and molecular mechanisms behind is discussed in the framework of BBB opening as an informative platform for a novel fundamental knowledge about the nature of BBB and for the development of a non-invasive brain drug delivery technology.Social aspects of musicsound-induced opening of BBB provide completely new information about noise and healthy life conditions that will stimulate new research in this field.
biorxiv neuroscience 100-200-users 2019Inception in visual cortex in vivo-silico loops reveal most exciting images, bioRxiv, 2018-12-29
Much of our knowledge about sensory processing in the brain is based on quasi-linear models and the stimuli that optimally drive them. However, sensory information processing is nonlinear, even in primary sensory areas, and optimizing sensory input is difficult due to the high-dimensional input space. We developed inception loops, a closed-loop experimental paradigm that combines in vivo recordings with in silico nonlinear response modeling to identify the Most Exciting Images (MEIs) for neurons in mouse V1. When presented back to the brain, MEIs indeed drove their target cells significantly better than the best stimuli identified by linear models. The MEIs exhibited complex spatial features that deviated from the textbook ideal of V1 as a bank of Gabor filters. Inception loops represent a widely applicable new approach to dissect the neural mechanisms of sensation.
biorxiv neuroscience 0-100-users 2018Neocortical layer 4 in adult mouse differs in major cell types and circuit organization between primary sensory areas, bioRxiv, 2018-12-28
AbstractLayer 4 (L4) of mammalian neocortex plays a crucial role in cortical information processing, yet a complete census of its cell types and connectivity remains elusive. Using whole-cell recordings with morphological recovery, we identified one major excitatory and seven inhibitory types of neurons in L4 of adult mouse visual cortex (V1). Nearly all excitatory neurons were pyramidal and all somatostatin-positive (SOM+) non-fast-spiking neurons were Martinotti cells. In contrast, in somatosensory cortex (S1), excitatory neurons were mostly stellate and SOM+ neurons were non-Martinotti. These morphologically distinct SOM+ interneurons corresponded to different transcriptomic cell types and were differentially integrated into the local circuit with only S1 neurons receiving local excitatory input. We propose that cell-type specific circuit motifs, such as the Martinottipyramidal and non-Martinottistellate pairs, are optionally used across the cortex as building blocks to assemble cortical circuits.
biorxiv neuroscience 100-200-users 2018On-site ribosome remodeling by locally synthesized ribosomal proteins in axons, bioRxiv, 2018-12-20
SUMMARYRibosomes are known to be assembled in the nucleolus, yet recent studies have revealed robust enrichment and translation of mRNAs encoding ribosomal proteins (RPs) in axons, far away from neuronal cell bodies. Using subcellular proteomics and live-imaging, we show that locally synthesized RPs incorporate into axonal ribosomes in a nucleolus-independent fashion. We revealed that axonal RP translation is regulated through a novel sequence motif, CUIC, that forms a RNA-loop structure in the region immediately upstream of the initiation codon. Inhibition of axonal CUIC-regulated RP translation leads to defects in local translation activity and axon branching, demonstrating the physiological relevance of the axonal ribosome remodeling. These results indicate that axonal translation supplies cytoplasmic RPs to maintainmodify local ribosomal function far from the nucleolus.
biorxiv neuroscience 100-200-users 2018Endogenous variation in ventromedial prefrontal cortex state dynamics during naturalistic viewing reflects affective experience, bioRxiv, 2018-12-17
AbstractHow we process ongoing experiences is shaped by our personal history, current needs, and future goals. Consequently, brain regions involved in generating these subjective appraisals, such as the vmPFC, often appear to be heterogeneous across individuals even in response to the same external information. To elucidate the role of the vmPFC in processing our ongoing experiences, we developed a computational framework and analysis pipeline to characterize the spatiotemporal dynamics of individual vmPFC responses as participants viewed a 45-minute television drama. Through a combination of functional magnetic resonance imaging, facial expression tracking, and self-reported emotional experiences across four studies, our data suggest that the vmPFC slowly transitions through a series of discretized states that broadly map onto affective experiences. Although these transitions typically occur at idiosyncratic times across people, participants exhibited a marked increase in state alignment during high affectively valenced events in the show. Our work suggests that the vmPFC ascribes affective meaning to our ongoing experiences.
biorxiv neuroscience 100-200-users 2018