Biology subjects

Jung, M. W.

Publications and source records attributed to Jung, M. W..

7 recordsLinked to original sources

bioRxiv2024

Selective engagement of prefrontal VIP neurons in reversal learning

To gain insights into neural mechanisms enabling behavioral adaptations to complex and multidimensional environmental dynamics, we examined roles of VIP neurons in mouse medial prefrontal cortex (mPFC) in probabilistic reversal learning. Behaviorally, manipulating VIP neuronal activity left probabilistic classical conditioning unaffected but severely impaired reversal learning. Physiologically, conditioned cue-associated VIP neuronal responses changed abruptly after encountering an unexpected reward. They also conveyed strong reward prediction error signals during behavioral reversal, but not before or after, unlike pyramidal neurons which consistently conveyed error signals throughout all phases. Furthermore, the signals persistence across trials correlated with reversal learning duration. These results suggest that mPFC VIP neurons play crucial roles in rapid reversal learning, but not in incremental cue-outcome association learning, by monitoring significant deviations from ongoing environmental contingency and imposing error-correction signals during behavioral adjustments. These findings shed light on the intricate cortical circuit dynamics underpinning behavioral flexibility in complex, multifaceted environments.

neuroscience↗

bioRxiv2023

Hierarchical gradient of timescales in the mammalian forebrain

Many anatomical and physiological features of cortical circuits, ranging from the biophysical properties of synapses to the connectivity patterns among different neuron types, exhibit consistent variation along the hierarchical axis from sensory to association areas. Notably, the scale of temporal correlation of neural activity at rest, known as the intrinsic timescale, increases systematically along this hierarchy in both primates and rodents, analogous to the growing scale and complexity of spatial receptive fields. However, how the timescales for task-related activity vary across brain regions and whether their hierarchical organization appears consistently across different mammalian species remain unexplored. Here, we show that both the intrinsic timescale and the timescales of task-related activity follow a similar hierarchical gradient in the cortices of monkeys, rats, and mice. We also found that these timescales covary similarly in both the cortex and basal ganglia, whereas the timescales of thalamic activity are shorter than cortical timescales and do not conform to the hierarchical order predicted by their cortical projections. These results suggest that the hierarchical gradient of cortical timescales might be a universal feature of intra-cortical circuits in the mammalian brain. Significance StatementA gradual increase in the intrinsic timescales of cortical activity along the anatomical hierarchy reflects the functional specialization of cortical circuits. However, it is unknown whether this gradient of timescales is a common feature across distinct mammalian species in both intrinsic and task-related timescales and whether it is also observed in subcortical areas. This study reveals that the hierarchical gradient of multiple cortical timescales is conserved across multiple mammalian species. By contrast, thalamic timescales were shorter than cortical timescales and did not follow the hierarchical order inferred from their cortical projections. These findings imply a crucial role of intra-cortical connections in structuring distinct temporal dynamics observed across the cortex.

neuroscience↗

bioRxiv2023

Sensory cortical ensembles exhibit differential coupling to ripples in distinct hippocampal subregions

Cortical neurons activated during recent experiences often reactivate with dorsal hippocampal CA1 sharp-wave ripples (SWRs) during subsequent rest. Less is known about cortical interactions with intermediate hippocampal CA1, whose connectivity, functions, and SWRs differ from those of dorsal CA1. We identified three clusters of visual cortical excitatory neurons that are excited together with either dorsal or intermediate CA1 SWRs, or suppressed before both SWRs. Neurons in each cluster were distributed across primary and higher visual cortices and co-active even in the absence of SWRs. These ensembles exhibited similar visual responses but different coupling to thalamus and pupil-indexed arousal. We observed a consistent activity sequence: (i) suppression of SWR-suppressed cortical neurons, (ii) thalamic silence, and (iii) activation of the cortical ensemble preceding and predicting intermediate CA1 SWRs. We propose that the coordinated dynamics of these ensembles relay visual experiences to distinct hippocampal subregions for incorporation into different cognitive maps.

neuroscience↗

bioRxiv2021

Suppressed prefrontal neuronal firing variability and impaired social representation in IRSp53-mutant mice

Social deficit is a major feature of neuropsychiatric disorders, including autism spectrum disorders, schizophrenia, and attention-deficit/hyperactivity disorder, but its neural mechanisms remain unclear. Here, we examined neuronal discharge characteristics in the medial prefrontal cortex (mPFC) of IRSp53-mutant mice, which show social deficits, during social approach. IRSp53-mutant excitatory mPFC neurons displayed an increase in baseline neuronal firing and decreases in variability and dynamic range of firing rates and burst firing during social and non-social target approaches compared to wild-type controls. As a consequence, their firing activity was less differential between social and non-social targets. In addition, there was a decrease in the proportion of excitatory mPFC neurons encoding social information but not that of those encoding non-social information. These results suggest that insufficient neuronal activity dynamics may underlie impaired cortical encoding of social information and social behaviors in IRSp53-mutant mice.

neuroscience↗

bioRxiv2021

Enhanced negative emotional processing limits behavioral flexibility in a mouse model of autism spectrum disorder

Impaired behavioral flexibility might underlie some of the symptoms associated with autism spectrum disorder (ASD). We investigated whether and how behavioral flexibility is impaired in a mouse model of ASD by testing Shank2-knockout (Shank2-KO) mice in reversal learning. Shank2-KO mice were trained in probabilistic classical conditioning with two odor cues paired with water and air puff. Upon the reversal of cue-outcome contingency, Shank2-KO mice were significantly slower than wild-type mice in reversing their anticipatory licking responses. Shank2-KO mice also showed stronger anticipatory eye closure responses than wild-type mice to the air puff, raising a possibility that the impairment might be because of enhanced negative emotional processing. Indeed, Shank2-KO mice showed intact reversal learning when the strong air puff was replaced with a mild air puff. Shank2-KO mice also showed intact reversal learning between two odor cues predicting rewards with different probabilities. These results indicate that enhanced negative emotional processing suppresses reversal learning despite of intact capability to learn cue-outcome contingency changes in Shank2-KO mice in our behavioral settings. Our findings suggest that behavioral flexibility may be seriously limited by abnormal emotional processing in ASD.

neuroscience↗

bioRxiv2021

Parallel processing of working memory and temporal information by distinct types of cortical projection neurons

It is unclear how different types of cortical projection neurons work together to support diverse cortical functions. We examined the discharge characteristics and inactivation effects of intratelencephalic (IT) and pyramidal tract (PT) neurons--two major types of cortical excitatory neurons that project to cortical and subcortical structures, respectively--in the medial prefrontal cortex of mice performing a delayed response task. We found that IT neurons, but not PT neurons, convey significant working memory-related signals. We also found that the inactivation of IT neurons, but not PT neurons, impairs behavioral performance. In contrast, PT neurons convey far more temporal information than IT neurons during the delay period. Our results indicate a division of labor between IT and PT projection neurons in the prefrontal cortex for the maintenance of working memory and for tracking the passage of time, respectively.

neuroscience↗

bioRxiv2018

Transient effect of mossy fiber stimulation on spatial firing of CA3 neurons

Strong hippocampal mossy fiber synapses are thought to function as detonators, imposing teaching signals onto CA3 neurons during new memory formation. For an empirical test of this long-standing view, we examined effects of stimulating mossy fibers on spatial firing of CA3 neurons in freely-moving mice. We found that optogenetic stimulation of mossy fibers can alter CA3 spatial firing, but their effects are only transient. Spatially restricted mossy fiber stimulation, either congruent or incongruent with CA3 place fields, was more likely to suppress than enhance CA3 neuronal activity. Also, changes in spatial firing induced by optogenetic stimulation reverted immediately upon stimulation termination, leaving CA3 place fields unaltered. Our results do not support the traditional view that mossy fibers impose teaching signals onto CA3 network, and show robustness of established CA3 spatial representations.

neuroscience↗