During free viewing, we move our eyes and fixate on objects to recognize the visual scene of our surroundings. To investigate the neural representation of objects in this process, we studied individual and population neuronal activity in three different visual regions of the brains of macaque monkeys ( Macaca fuscata ): the primary and secondary visual cortices (V1, V2) and the inferotemporal cortex (IT). We designed a task where the animal freely selected objects in a stimulus image to fixate on while we examined the relationship between spiking activity, the order of fixations, and the fixated objects. We found that activity changed across repeated fixations on the same object in all three recorded areas, with observed reductions in firing rates. Furthermore, the responses of individual neurons became sparser and more selective with individual objects. The population activity for individual objects also became distinct. These results suggest that visual neurons respond dynamically to repeated input stimu...

The auditory system relies on both local and summary representations; acoustic local features exceeding system constraints are compacted into a set of summary statistics. Such compression is pivotal for sound-object recognition. Here, we assessed whether computations subtending local and statistical representations of sounds could be distinguished at the neural level. A computational auditory model was employed to extract auditory statistics from natural sound textures (i.e., fire, rain) and to generate synthetic exemplars where local and statistical properties were controlled. Twenty-four human participants were passively exposed to auditory streams while the electroencephalography (EEG) was recorded. Each stream could consist of short, medium, or long sounds to vary the amount of acoustic information. Short and long sounds were expected to engage local or summary statistics representations, respectively. Data revealed a clear dissociation. Compared with summary-based ones, auditory-evoked responses based...

The timing and specificity of oligodendrocyte myelination during development, as well as remyelination after injury or immune attack, remain poorly understood. Recent work has shown that oligodendrocyte progenitors receive synapses from neurons, providing a potential mechanism for neuronal-glial communication. In this study, we investigated the importance of these neuroglial connections in myelination during development and during neuronal plasticity in the mouse hippocampus. We used chemogenetic tools and viral monosynaptic circuit tracing to analyze these connections and to examine oligodendrocyte progenitor cells (OPCs) proliferation, myelination, synapse formation, and neuronal-glial connectivity in vivo after increasing or decreasing neuronal activity levels . We found that increasing neuronal activity led to greater OPC activation and proliferation. Modulation of neuronal activity also altered the organization of neuronal-glial connections: while it did not impact the total number of RabV-labeled neu...

The annual Society for Neuroscience (SfN) meeting yields significant, measurable impacts that conflict with the environmental commitment of the Society and the Intergovernmental Panel on Climate Change (IPCC) recommendations to address the climate emergency ([IPCC, 2018][1]). We used 12,761 presenters’ origins, two online carbon calculators, and benchmark values to estimate 2018 meeting-related travel, event venue operations, and hotel accommodation emissions. Presenters’ conference travel resulted in between 17,298 and 8690 tons of atmospheric carbon dioxide (t CO2), with or without radiative forcing index factors. Over 92% of authors traveled by air and were responsible for >99% of total travel-related emissions. Extrapolations based on 28,691 registrants yielded between 69,592.60 metric tons of carbon dioxide equivalents (t CO2e) and 38,010.85 t CO2 from travel. Comparatively, authors’ and registrants’ hotel accommodation emissions equaled 429 and 965 t CO2e, whereas operation of the San Diego Conventio...

The Intercalated Cells of the Amygdala (ITCs) are a fundamental processing structure in the amygdala that remain relatively understudied. They are phylogenetically conserved from insectivores through primates, inhibitory, and project to several of the main processing and output stations of the amygdala and basal forebrain. Through these connections, the ITCs are best known for their role in conditioned fear, where they are required for fear extinction learning and recall. Prior work on ITC connectivity is limited, and thus holistic characterization of their afferent and efferent connectivity in a genetically defined manner is incomplete. The ITCs express the FoxP2 transcription factor, affording genetic access to these neurons for viral input-output mapping. To fully characterize the anatomical connectivity of the ITCs, we used cre-dependent viral strategies in FoxP2-cre mice to reveal the projections of the main (mITC), caudal (cITC), and lateral (lITC) clusters along with their presynaptic sources of inn...

The auditory system relies on both local and summary representations; acoustic local features exceeding system constraints are compacted into a set of summary statistics. Such compression is pivotal for sound-object recognition. Here, we assessed whether computations subtending local and statistical representations of sounds could be distinguished at the neural level. A computational auditory model was employed to extract auditory statistics from natural sound textures (i.e., fire, rain) and to generate synthetic exemplars where local and statistical properties were controlled. Twenty-four human participants were passively exposed to auditory streams while the EEG was recorded. Each stream could consist of short, medium, or long sounds to vary the amount of acoustic information. Short and long sounds were expected to engage local or summary statistics representations, respectively. Data revealed a clear dissociation. Compared to summary-based ones, auditory-evoked responses based on local information were ...

Cajal-Retzius (CR) cells are transient neurons with long-lasting effects on the architecture and circuitry of the neocortex and hippocampus. Contrary to the prevailing assumption that CR cells completely disappear in rodents shortly after birth, a substantial portion of these cells persist in the hippocampus throughout adulthood. The role of these surviving CR cells in the adult hippocampus is largely unknown, partly because of the paucity of suitable tools to dissect their functions in the adult versus the embryonic brain. Here, we show that genetic crosses of the ΔNp73-Cre mouse line, widely used to target CR cells, to reporter mice induce reporter expression not only in CR cells but also progressively in postnatal dentate gyrus granule neurons. Such a lack of specificity may confound studies of CR cell function in the adult hippocampus. To overcome this, we devise a method that not only leverages the temporary CR cell-targeting specificity of the ΔNp73-Cre mice before the first postnatal week, but also ...

The levels of purines, essential molecules to sustain eukaryotic cell homeostasis, are regulated by the coordination of the de novo and salvage synthesis pathways. In the embryonic central nervous system (CNS), the de novo pathway is considered crucial to meet the requirements for the active proliferation of neural stem/progenitor cells (NSPCs). However, how these two pathways are balanced or separately utilized during CNS development remains poorly understood. In this study, we showed a dynamic shift in pathway utilization, with greater reliance on the de novo pathway during embryonic stages and on the salvage pathway in postnatal–adult mouse brain. The pharmacological effects of various purine synthesis inhibitors in vitro and the expression profile of purine synthesis enzymes indicated that NSPCs in the embryonic cerebrum mainly utilize the de novo pathway. Simultaneously, NSPCs in the cerebellum require both the de novo and the salvage pathways. In vivo administration of de novo inhibitors resulted in ...

Spoken language contains information at a broad range of timescales, from phonetic distinctions on the order of milliseconds to semantic contexts which shift over seconds to minutes. It is not well understood how the brain's speech production systems combine features at these timescales into a coherent vocal output. We investigated the spatial and temporal representations in cerebral cortex of three phonological units with different durations: consonants, vowels, and syllables. Electrocorticography recordings were obtained from five participants while speaking single syllables. We developed a novel clustering and Kalman filter-based trend analysis procedure to sort electrodes into temporal response profiles. A linear discriminant classifier was used to determine how strongly each electrode's response encoded phonological features. We found distinct time-courses of encoding phonological units depending on their duration: consonants were represented more during speech preparation, vowels were represented eve...

The annual Neuroscience meeting yields significant, measurable impacts that conflict with the environmental commitment of the society and IPCC’s recommendations to address the climate emergency (IPCC, 2018). We used 12,761 presenters’ origins, two online carbon calculators, and benchmark values to estimate 2018 meeting-related travel, event venue operations, and hotel accommodation emissions. Presenters’ conference travel resulted in between 17,298 and 8,690 t CO2, with or without radiative forcing index factors. Over 92% of authors traveled by air and were responsible for over 99% of total travel-related emissions. Extrapolations based upon 28,691 registrants yielded between 69,592.60 t CO2e and 38,010.85 t CO2 from travel. Comparatively, authors’ and registrants’ hotel accommodation emissions equaled 429 and 965 t CO2e, whereas operation of the San Diego Convention Center equaled about 107 t CO2e. We relate SfN meeting-related emissions to potential September Arctic sea ice loss, labor productivity loss ...