neuroscience105.39 min read
Memory-guided edge tracking enables vector-based olfactory navigation in fruit flies
3 days ago•Source: Nature
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Cortical coding favors high-dimensional diversity over fixed categories
Across ~14,000 neurons in 43 mouse cortical regions, the study shows cortex-wide representations are organized categorically, but within individual areas responses are highly diverse and non-categorical. This diversity creates high-dimensional neural geometry that enables linear readouts to separate many conditions, with maximal separability emerging when information is accounted for in each area. The results imply a computational regime that prioritizes diversity over fixed categories, and reveal a gradient of increasing representational dimensionality along the cortical hierarchy closely tied to anatomy and connectivity.
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Timing of Childhood Trauma Shapes Distinct Brain Signatures in Adulthood
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Inhibitory Overload in the Prefrontal Cortex Linked to Aging Memory Loss
A Neurobiology of Disease study finds that aging-related memory decline may be driven by an excess of inhibitory synapses in the prefrontal cortex. In aged mice, researchers identified two groups—cognitively susceptible and resilient—with the susceptible group showing higher levels of inhibitory markers (Gephyrin, VGAT) and denser inhibitory synapses in the prefrontal cortex. Using optogenetics, activating inhibitory neurons in young mice reproduced memory and exploration deficits, while similar stimulation in aged impaired mice had no additional effect, suggesting a chronic, structure‑level inhibitory load contributes to cognitive decline. The study warns that treatments increasing inhibition could worsen age-related cognitive deficits and notes limitations, including all-male subjects and the artificial nature of the manipulation.
Brain estrogen in both sexes shapes memory's resilience to stress
Researchers in mice show that estrogen produced in the hippocampus alters memory after acute stress in a sex- and cycle-dependent way: high hippocampal estrogen in males and proestrus females worsened memory, while estrus females with lower estrogen were more resilient. The findings suggest estrogen receptors regulate chromatin and memory-related genes, with potential implications for PTSD risk and aging in humans—especially during perimenopause—though further study is needed.
Neurons Map the Cellular Grammar of Human Language
Recordings from 579 neurons across the human frontotemporal cortex during natural speech show individual cells encode fine-grained linguistic features: some respond to parts of speech, others to sentence constituents or dependency depth, and some track combinatorial feature sets. The neuron population also encodes sentence context, with language encoding being left-lateralized and varying by region. Large language models’ contextual embeddings better predict neural activity than syntax/semantics alone, revealing distributed cellular building blocks and a micro-to-macro map of how language is represented in the brain.
Interwoven whole-body motor maps across the human precentral gyrus revealed by single-neuron recordings
An eight-participant BrainGate study mapped the crown of the human precentral gyrus at single-neuron resolution, finding whole-body representations at every sampled site with intermingled limb and speech tuning that partially follows the classic motor homunculus. The researchers identify four functional zones and demonstrate a compositional, limb-independent neural code that links limbs and allows robust decoding of 46 movements across regions, informing targeted strategies for multi-function motor BCIs and challenging strict somatotopy hypotheses.
Convergent Cortical Development Delays Across Autism Mouse Models
A large multi-omics study profiling 251 samples from 11 ASD-linked mouse models across embryonic and postnatal stages, both sexes, and two brain regions finds convergence on disruptions to the radial glial lineage that manifest as a transient developmental delay rather than lasting lineage mis-specification. Neurons show the largest early postnatal transcriptional changes, including downregulation of synaptic and ion-channel genes consistent with delayed maturation. Within each developmental window, models converge on shared molecular programs, but the convergence diminishes by postnatal day 14, with cross-genotype heterogeneity overlaying stage-specific effects. Electrophysiology corroborates altered neuronal excitability and synaptic properties across models, and sex-specific gene expression differences emerge, often with larger effects in females. Using multiplexed snRNA-seq/snATAC-seq (snMultiome), EdU lineage tracing, RNAscope, and biophysical modeling, the study maps developmental trajectories and cross-model convergence, offering a unified view of how diverse ASD mutations perturb cortical development.
Brain cells map the building blocks of speech
A Nature study used temporarily implanted brain electrodes in epilepsy patients to observe real-time single-neuron activity in the frontotemporal cortex as people spoke. It found specialized neurons that encode parts of speech and semantics or syntax, with many neurons firing just before specific components (e.g., nouns) are spoken. The left hemisphere showed greater involvement, and the researchers noted that both brain activity and large-language models track the sentence context up to about five preceding words to shape the next word—supporting a modular view of language built from neuronal building blocks.
Histamine Brain Rhythms Gate Real-Time Memory Access
A Nagoya City University study shows slow, spontaneous fluctuations in histamine neurons bias moment-to-moment memory accessibility in mice: higher histamine activity before a cue improves memory-guided responses, while lower activity reduces them. Using real-time cues and optogenetics, researchers confirm a priming-state mechanism that prepares memory circuits, with the basolateral amygdala acting downstream, suggesting memory lapses can arise from brain state rather than memory decay.
Early genome duplications expanded vertebrate brain cell diversity
Cross-species single-cell analyses of human, mouse, lizard, lamprey and amphioxus brains show that vertebrate brain cell-type families often lack one-to-one amphioxus homologs; ohnologues from the first whole-genome duplication were especially important for vertebrate cell-type diversification, driven by dosage selection and subfunctionalization, with ohnologues continuing to enable cellular diversity across brain regions and glia.
Decision-Making Emerges from Sensorimotor Loops, Not a Central Brain Center
A new study argues there is no discrete neural 'decision center' in the brain; instead, intentional-looking behavior arises from the simultaneous interaction of sensory, sensorimotor, and motor processes, challenging the linear 'sandwich' model and the Cartesian Theater. The paper uses analogies to nonphysical decisions and a simple wall-following robot to illustrate how decisions can appear purposeful without a central controller, and calls for embodied, ecological approaches to studying decision-making.
Dopamine Sets the Pace of Stress-Driven Courtship Suppression in Flies
In fruit flies, researchers show that dopamine does not trigger the initial shutdown of mating drive under stress but acts as a molecular timer that sustains suppression after stress; longer confinement leads to longer-lasting courtship inhibition via dopamine signaling in the mushroom body, offering insights into stress-related sexual dysfunction that may extend to humans.