Updated March 2, 2021
Research Spotlight
Adult trkB Signaling in Parvalbumin Interneurons is Essential to Prefrontal Network Dynamics
The importance of the neurotrophin BDNF and its receptor trkB in the development of neurons and brain circuits is well established. Guyon et al. focused on the function of the BDNF/trkB pathway in the adult brain and showed that it is necessary for the operations of a specific neuron type central to proper levels and patterns of brain activity. Alteration of the BDNF/trkB pathway in the prefrontal cortex of adult mice resulted in changes in rhythmic brainwave patterns and increased aggression. The findings demonstrate that BDNF/trkB signaling is not only important for the development of the brain but is also essential to cognition and proper functioning of the prefrontal cortex in the adult.
Memory Load Alters Perception-Related Neural Oscillations during Multisensory Integration
The integration of information across multiple senses is a complex process that is sensitive to external influences. Michail et al. investigated how the integration of simple auditory and visual stimuli is affected when cognitive resources are limited. The authors found that when available resources are depleted the integration of simple audio-visual stimuli is enhanced and, importantly, that under such conditions it requires the engagement of specific higher-level, top-down neuronal mechanisms, namely, theta and beta oscillations. This work extends our understanding of the role of context-related parameters during multisensory integration.
The cocktail party problem in auditory neuroscience can be recast as selectively listening to a localized auditory source. This process is presumably subserved by a network of areas. Napoli, Camalier et al. from NIMH examined several candidate areas including primary auditory cortex, prefrontal cortex, and the amygdala. Each of these areas was thought to contribute to components of this process. They found that, unlike work on related problems in the visual system, primary auditory cortex represented all components of the spatial selective listening task before prefrontal cortex, or the amygdala. This suggests that spatially selective sensory processes are organized in fundamentally different ways across the auditory and visual systems.
Vasopressin, also called antidiuretic hormone, are secreted by vasopressin neurons that play a key role in maintaining fluid homeostasis. Neupane et al. identified that chronic osmotic stimulus recruited NR2D subunit-containing NMDA receptors in supraoptic vasopressin neurons over oxytocin neurons. This leads to selective upregulation of the neuronal excitability of vasopressin neurons and contributes to fluid homeostasis via hormone secretion. This finding unveils a novel form of state-dependent plasticity in excitation-inhibition balance through recruitment of NR2D receptors in the adult brain following high salt intake.
By using an advanced neuron-computer-interface system, Kogo et al. developed an experimental model in which two real-life neurons are connected with computer-modeled neurons and synapses. The authors constructed a circuit with this “hybrid” system in which the two neurons compete with each other via inhibitory synaptic connections. They found that the circuit shows bi-stable activity when both neurons are activated simultaneously, and that its dynamics show surprisingly similar properties as observed during bi-stable perception in humans.
Most-Discussed Research Published in February
Below are five Early Release articles that generated the most online discussion in February 2021, as measured by Altmetric. Altmetric data is available for all articles published in JNeurosci on the Info & Metrics tab. Learn more about how the Altmetric score is calculated.
Humans acquire detailed semantic knowledge about people (e.g., their occupation and personality) and places (e.g., their cultural or historical significance). While research has demonstrated that brain regions preferentially respond to pictures of people and places, less is known about whether these regions preferentially represent semantic knowledge about specific people and places. We used machine learning techniques to develop a model of semantic similarity based on information available from Wikipedia, validating the model against similarity ratings from human participants. Using our computational model, we found that semantic knowledge about people and places is represented in distinct anterior temporal and posterior medial brain networks, respectively. We further found that hippocampus—an important memory center—represented semantic knowledge for both types of stimuli.
Accumulating evidence supports the organizational effects of pubertal testosterone, but the body of literature examining these effects on social cognition in humans is in its infancy. With a sample of young men from a longitudinal birth cohort, we showed that the cumulative exposure to testosterone during adolescence moderated the relation between adult testosterone and both the mean BOLD signal change and functional connectivity. Specifically, we observed a positive relationship between adult testosterone and the brain response to faces in participants with low exposure to testosterone during puberty, but not in participants with medium and high pubertal testosterone. Results of further analysis suggest that sensitivity to cues carried by the eyes might underlie the relationship between testosterone and brain response to faces, especially in the context of a potential threat.
Network asynchrony underlying increased broadband gamma power
Brain oscillations are fundamental to the coordination of neuronal activity across neurons and structures. Gamma oscillations (30-80 Hz) have received particular attention through their association with perceptual and cognitive processes. Synchronous activity of inhibitory PV interneurons generates cortical gamma oscillation, but, paradoxically, PV neuron deficiency is associated with increases in gamma oscillations. We here reconcile this conundrum and show how deficient PV inhibition can lead to increased and asynchronous excitatory firing, contaminating the LFP and manifesting as increased gamma power. Thus, increased gamma power does not always reflect a genuine rhythm. Further, we show that ketamine-induced gamma increases are caused by separate network mechanisms.
Adaptive memory distortions are predicted by feature representations in parietal cortex
Similarity between memories is a primary cause of interference and forgetting. Here, we show that when remembering highly similar objects, subtle differences in the features of these objects are exaggerated in memory in order to reduce interference. These memory distortions are reflected in, and predicted by, overlap of activity patterns in lateral parietal cortex. These findings provide unique insight into how memory interference is resolved and specifically implicate lateral parietal cortex in representing feature-specific memory distortions.
Expert tool users show increased differentiation between visual representations of hands and tools
It is commonly thought that tool use leads to assimilation of the tool into the neural representation of the body, a process referred to as embodiment. Here, we demonstrate that expert tool users (London litter pickers) neurally represent their own tool less like a hand (not more), compared to novices. Our findings advance our current understanding for how experience shapes functional organisation in high-order visual cortex. Further, this evidence provides an alternative framework to the prominent tool embodiment theory, suggesting instead that experience with tools leads to more distinct, separable hand and tool representations.
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