Updated September 19, 2023
Research Spotlight
Different theories of anterior cingulate cortex function suggest that this region is important for tracking reward contexts or for linking goals to appropriate actions. These possibilities were evaluated in monkeys performing a task where contexts were determined by the potential to either gain or lose a valuable asset. Chein and colleagues showed that the activity of cingulate neuron populations was predominantly structured by reward context, and that trial outcomes were encoded in a relative sense, as either the better or worse possible outcome within a context. These representations were separated from information about the motor response that achieved the outcome, which was encoded in an orthogonal space, indicating that, rather than linking goals and actions, the anterior cingulate cortex is more involved in context-setting and relative interpretation of outcomes.
The Hierarchy of Coupled Sleep Oscillations Reverses with Aging in Humans
As we age, the coupling of two electrophysiological sleep oscillations – slow waves and spindles – tends to deteriorate, impacting memory and brain metabolism. By examining a large cohort of 340 individuals aged 15 to 83, Züst and colleagues unveiled a surprising evolution in the dynamics of slow wave-spindle coupling during sleep. Contrary to the expected decoupling, spindles gradually shift from being driven by slow waves to driving them with age, while coupling strength remains unaffected. This shift is linked to astrocyte activation, suggesting potential compensatory processes. These findings enhance our understanding of the intricate relationship between aging, sleep, and cognitive vitality and may help combat cognitive decline.
Distinctive Roles of Medial Prefrontal Cortex Subregions in Strategic Conformity to Social Hierarchy
Have you ever experienced conforming to your boss’s opinion despite disagreeing? Kim and colleagues demonstrated that participants, categorized by performance levels and rating images alongside higher or lower status peers, exhibited a stronger tendency to align their opinions with superiors’, particularly when under observation. Neuroimaging data revealed that the rostromedial prefrontal cortex (rmPFC) has been identified as a crucial area associated with modifying one’s preferences based on the other person’s rank. The ventromedial prefrontal cortex (vmPFC) was active when one’s opinion aligns with that of a superior, while the dorsomedial prefrontal cortex (dmPFC) was active when disagreeing privately. Considering the idea that ascending the brain’s hierarchy along the mPFC axis leads to an increased reliance on external signals over internal ones, assisting in predicting and preventing bodily homeostatic imbalances, these findings imply that conforming to authority figures helps save bodily energy.
Most-Discussed Research Published in August
Below are five Early Release articles that generated the most online discussion in August 2023, 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.
Switching between external and internal attention in hippocampal networks
How does the brain balance the need to pay attention to internal thoughts and external sensations? We focused on the human hippocampus, a region that may serve at the interface between internal and external attention, and asked how its functional connectivity varies based on attentional states. The hippocampus was more strongly coupled with the cholinergic basal forebrain when attentional states were guided by the external world rather than retrieved memories. This pattern flipped for functional connectivity between the hippocampus and dorsal attention network, which was higher for attention tasks that were guided by memory rather than external cues. Together, these findings show that distinct networks in the brain may modulate the hippocampus to switch between external and internal attention.
We present results from AMseL (‘Audio and Neuroplasticity of Musical Learning’), a 12-year longitudinal study on the development of the human auditory system from childhood to adulthood that combined structural magnetic resonance imaging, magnetoencephalography, and auditory discrimination and pattern recognition tests. 66 musicians and 46 non-musicians were tested at five time points. Substantial, stable differences in the morphology of auditory cortex were found between the two groups even at the earliest ages, suggesting that musical aptitude is manifested in macroscopic neuroanatomical characteristics. We also observed neuroplastic and perceptual changes with age and musical practice. This interplay between ‘nature’ (stable biological dispositions and natural maturation) and ‘nurture’ (learning-induced plasticity) is integrated into a novel neurodevelopmental model of the human auditory system.
How does the brain differentiate between imagined and perceived experiences? Combining fMRI, eye-tracking, multivariate decoding and encoding approaches, the current study revealed enhanced stimulus-specific representations in visual imagery originating from parietal cortex, supporting the subjective experience of imagery. This neural principle was further validated by evidence from visual illusion, wherein illusion resembled perception and imagery at different levels of cortical hierarchy. Our findings provide direct evidence for the critical role of parietal cortex as a domain-general region for content-specific imagery, and offer new insights into the neural mechanisms underlying the differentiation between subjectively internal and external experiences.
Exposure to radiation can affect cognitive performance and cognitive flexibility — the ability to adapt to changed circumstances and demands. The full range of consequences of irradiation on cognitive flexibility is unknown, partly because of a lack of suitable models. Here, we developed a new behavioral task requiring mice to combine various types of cues and strategies to find a correct solution. We show that animals exposed to γ-radiation, despite being able to successfully solve standard problems, show delayed learning, deficient memory, and diminished use of efficient navigation patterns in circumstances requiring adjustments of previously used search strategies. This new task could be applied in other settings for assessing the cognitive changes induced by aging, trauma, or disease.
Cholinergic reinforcement signaling is impaired by amyloidosis prior to its synaptic loss
The cholinergic system is especially vulnerable to the neurotoxic effects of amyloidosis, a hallmark of Alzheimer’s disease. Though amyloid-induced cholinergic synaptic loss is thought in part to account for learning and memory impairments in AD, little is known regarding how amyloid impacts signaling of the cholinergic system prior to its anatomical degeneration. Optical measurement of ACh release in a mouse model of AD that develops amyloidosis reveals that ACh signals reinforcement and outcome-prediction that is disrupted by amyloidosis prior to cholinergic degeneration. These observations have important scientific and clinical implications: they implicate ACh signaling as an early functional biomarker, provide a deeper understanding of acetylcholine’s action, and inform upon when and how intervention may best ameliorate cognitive decline in AD.
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