Fuu Jiun Hwang

All Publications

• A positively tuned voltage indicator for extended electrical recordings in the brain. Nature methods Evans, S. W., Shi, D., Chavarha, M., Plitt, M. H., Taxidis, J., Madruga, B., Fan, J. L., Hwang, F., van Keulen, S. C., Suomivuori, C., Pang, M. M., Su, S., Lee, S., Hao, Y. A., Zhang, G., Jiang, D., Pradhan, L., Roth, R. H., Liu, Y., Dorian, C. C., Reese, A. L., Negrean, A., Losonczy, A., Makinson, C. D., Wang, S., Clandinin, T. R., Dror, R. O., Ding, J. B., Ji, N., Golshani, P., Giocomo, L. M., Bi, G., Lin, M. Z. 2023; 20 (7): 1104-1113

  Abstract

  Genetically encoded voltage indicators (GEVIs) enable optical recording of electrical signals in the brain, providing subthreshold sensitivity and temporal resolution not possible with calcium indicators. However, one- and two-photon voltage imaging over prolonged periods with the same GEVI has not yet been demonstrated. Here, we report engineering of ASAP family GEVIs to enhance photostability by inversion of the fluorescence-voltage relationship. Two of the resulting GEVIs, ASAP4b and ASAP4e, respond to 100-mV depolarizations with ≥180% fluorescence increases, compared with the 50% fluorescence decrease of the parental ASAP3. With standard microscopy equipment, ASAP4e enables single-trial detection of spikes in mice over the course of minutes. Unlike GEVIs previously used for one-photon voltage recordings, ASAP4b and ASAP4e also perform well under two-photon illumination. By imaging voltage and calcium simultaneously, we show that ASAP4b and ASAP4e can identify place cells and detect voltage spikes with better temporal resolution than commonly used calcium indicators. Thus, ASAP4b and ASAP4e extend the capabilities of voltage imaging to standard one- and two-photon microscopes while improving the duration of voltage recordings.

  View details for DOI 10.1038/s41592-023-01913-z

  View details for PubMedID 37429962

• Dichotomous regulation of striatal plasticity by dynorphin. Molecular psychiatry Yang, R., Tuan, R. R., Hwang, F., Bloodgood, D. W., Kong, D., Ding, J. B. 2022

  Abstract

  Modulation of corticostriatal plasticity alters the information flow throughout basal ganglia circuits and represents a fundamental mechanism for motor learning, action selection, and reward. Synaptic plasticity in the striatal direct- and indirect-pathway spiny projection neurons (dSPNs and iSPNs) is regulated by two distinct networks of GPCR signaling cascades. While it is well-known that dopamine D2 and adenosine A2a receptors bi-directionally regulate iSPN plasticity, it remains unclear how D1 signaling modulation of synaptic plasticity is counteracted by dSPN-specific Gi signaling. Here, we show that striatal dynorphin selectively suppresses long-term potentiation (LTP) through Kappa Opioid Receptor (KOR) signaling in dSPNs. Both KOR antagonism and conditional deletion of dynorphin in dSPNs enhance LTP counterbalancing with different levels of D1 receptor activation. Behaviorally, mice lacking dynorphin in D1 neurons show comparable motor behavior and reward-based learning, but enhanced flexibility during reversal learning. These findings support a model in which D1R and KOR signaling bi-directionally modulate synaptic plasticity and behavior in the direct pathway.

  View details for DOI 10.1038/s41380-022-01885-0

  View details for PubMedID 36460726

• Motor learning selectively strengthens cortical and striatal synapses of motor engram neurons. Neuron Hwang, F., Roth, R. H., Wu, Y., Sun, Y., Kwon, D. K., Liu, Y., Ding, J. B. 2022

  Abstract

  Learning and consolidation of new motor skills require plasticity in the motor cortex and striatum, two key motor regions of the brain. However, how neurons undergo synaptic changes and become recruited during motor learning to form a memory engram remains unknown. Here, we train mice on a motor learning task and use a genetic approach to identify and manipulate behavior-relevant neurons selectively in the primary motor cortex (M1). We find that the degree of M1 engram neuron reactivation correlates with motor performance. We further demonstrate that learning-induced dendritic spine reorganization specifically occurs in these M1 engram neurons. In addition, we find that motor learning leads to an increase in the strength of M1 engram neuron outputs onto striatal spiny projection neurons (SPNs) and that these synapses form clusters along SPN dendrites. These results identify a highly specific synaptic plasticity during the formation of long-lasting motor memory traces in the corticostriatal circuit.

  View details for DOI 10.1016/j.neuron.2022.06.006

  View details for PubMedID 35809573