Different Behavior of Density Perturbations Between Dayside and Nightside in the Martian Thermosphere and the Ionosphere Associated With Atmospheric Gravity Waves.

To investigate the excitation mechanism of ionospheric perturbations on Mars by the Neutral Gas and Ion Mass Spectrometer (NGIMS) onboard Mars Atmosphere and Volatile EvolutioN (MAVEN), we categorize ionospheric perturbations into three cases: (a) the ion-neutral coupling cases where ion and neutral perturbations are well coupled, (b) the ion-specific cases where ion perturbations move independently from neutrals, and (c) the coronal mass ejection cases associated with solar wind extreme events. A representative number of cases from total profiles are compared with a numerical model to determine the fraction that can be explained by an atmospheric gravity waves (GW). The neutral perturbations on the dayside at 170-190 km altitudes are in excellent agreement with the GW.

Martian atmospheric hydrogen and deuterium: Seasonal changes and paradigm for escape to space.

Mars' water history is fundamental to understanding Earth-like planet evolution. Water escapes to space as atoms, and hydrogen atoms escape faster than deuterium giving an increase in the residual D/H ratio. The present ratio reflects the total water Mars has lost.

Parallel Synapses with Transmission Nonlinearities Enhance Neuronal Classification Capacity.

Cortical neurons often establish multiple synaptic contacts with the same postsynaptic neuron. To avoid functional redundancy of these parallel synapses, it is crucial that each synapse exhibits distinct computational properties. Here we model the current to the soma contributed by each synapse as a sigmoidal transmission function of its presynaptic input, with learnable parameters such as amplitude, slope, and threshold.

Deep Learning without Weight Symmetry.

Backpropagation (BP), a foundational algorithm for training artificial neural networks, predominates in contemporary deep learning. Although highly successful, it is often considered biologically implausible. A significant limitation arises from the need for precise symmetry between connections in the backward and forward pathways to backpropagate gradient signals accurately, which is not observed in biological brains.

Temporal multiplexing of perception and memory codes in IT cortex.

A central assumption of neuroscience is that long-term memories are represented by the same brain areas that encode sensory stimuli. Neurons in inferotemporal (IT) cortex represent the sensory percept of visual objects using a distributed axis code. Whether and how the same IT neural population represents the long-term memory of visual objects remains unclear.