Biology subjects

Higley, M.

Publications and source records attributed to Higley, M..

8 recordsLinked to original sources

bioRxiv2026

Cholinergic and adrenergic modulation sculpts parallel inhibition of SST-INs in visual cortex

GABAergic interneurons are fundamental to the normal function of neuronal circuits in the neocortex. A growing literature has highlighted the role of somatostatin-expressing interneurons (SST-INs) in regulating cortical activity, and inhibition of SST-INs by other interneurons has emerged as a circuit motif leading to disinhibition of pyramidal neurons. However, the diversity and regulation of GABAergic inputs to SST-INs are only partially understood. Here, we combined widefield and 2-photon optogenetic stimulation of parvalbumin (PV)- and vasoactive intestinal peptide (VIP)-expressing interneurons with recordings from fluorescently identified SST-INs in layer 2/3 of primary visual cortex (V1). Our results show that both PV- and VIP-INs form inhibitory inputs onto SST-INs but with varying functional properties. PV-INs evoke strong, fast inhibition onto perisomatic regions of their target cells, while VIP-INs evoke slower inhibition onto target cell dendrites that is partially mediated by alpha subunit-containing GABA receptors. Cholinergic modulation through muscarinic receptors strongly suppresses PV-IN output while adrenergic modulation through beta receptors enhances VIP-IN output. Computational modeling suggests that these parallel inhibitory pathways can differentially regulate circuit gain and network stability across different inputs and arousal conditions. Thus, the diversity of disinhibitory GABAergic circuits in the neocortex provides a mechanism for state-dependent flexibility in circuit function.

neuroscience↗

bioRxiv2026

Multiquantal transmission supports dynamic synaptic strength in vivo

In the central nervous system, synaptic transmission occurs through the probabilistic release of neurotransmitter vesicles following presynaptic action potentials (AP). Traditional models posit a single vesicle release event per AP, though experimental evidence indicates multivesicular release (MVR) may occur under some circumstances, greatly expanding the dynamic range and information content at single synapses. However, the quantal nature of synaptic transmission in the intact, waking brain is largely unknown. Here, we used two-photon imaging of iGluSnFR4f-expressing cortical axons and found that MVR dominates synaptic transmission at both layer 4 and layer 2/3 synapses, enhancing reliability and yielding non-binary signaling for single synaptic connections. Moreover, MVR in the presence of cholinergic modulation conveys behavioral state-dependent influence over synaptic potency. Overall, our findings demonstrate that MVR at central synapses in vivo contributes to the computational capacity of cortical circuits.

neuroscience↗

bioRxiv2025

Learning-dependent cholinergic plasticity reconfigures cortical circuit dynamics.

Neuromodulation by acetylcholine (ACh) plays a critical role in shaping neural dynamics in the neocortex as a function of development, behavioral state, and learning 1-6. Prior work suggests cholinergic signaling can act as a gate for the subsequent induction of circuit plasticity 3,7,8. However, modification of ACh release could also be a direct mechanism for the expression of cortical plasticity. Here, we combine widefield and 2-photon imaging in head-fixed mice to show that visual fear conditioning leads to a selective, cue-dependent release of ACh in primary visual cortex that enhances visually-evoked neuronal responses via excitation of layer 1 GABAergic interneurons and resulting disinhibition of local excitatory pyramidal neurons. Cholinergic signaling through muscarinic receptors in visual cortex is necessary for both learning and expression of conditioned fear behavior and enhanced visual representation. Our results demonstrate a novel capacity for conditioned release of ACh in sensory cortex to serve as a mechanism for sensory-guided behavioral learning. Rather than acting as a simple gate, cortical neuromodulation may thus play a central role in the expression of learned behavior.

neuroscience↗

bioRxiv2022

The Cousa objective: a long working distance air objective for multiphoton imaging in vivo

Multiphoton microscopy can resolve fluorescent structures and dynamics deep in scattering tissue, but applying this technique in vivo can be limited by short working distance water-immersion objectives. Here we present an ultra long working distance (20 mm) air objective called the Cousa objective. It is optimized for performance across multiphoton imaging wavelengths, offers a > 4 mm2 field-of-view with submicron lateral resolution, and is compatible with commonly used multiphoton imaging systems. We share the full optical prescription, and report performance including in vivo 2-photon and 3-photon imaging in a range of species and preparations.

neuroscience↗

bioRxiv2020

Dual color mesoscopic imaging reveals spatiotemporally heterogeneous coordination of cholinergic and neocortical activity.

Variation in an animals behavioral state is linked to fluctuations in brain activity and cognitive ability. In the neocortex, state-dependent control of circuit dynamics may reflect neuromodulatory influences including acetylcholine (ACh). While early literature suggested ACh exerts broad, homogeneous control over cortical function, recent evidence indicates potential anatomical and functional segregation of cholinergic signaling. Additionally, it is unclear whether states as defined by different behavioral markers reflect heterogeneous cholinergic and cortical network activity. We performed simultaneous, dual-color mesoscopic imaging of both ACh and calcium across the neocortex of awake mice to investigate their relationships with behavioral variables. We find that increasing arousal, categorized by different motor behaviors, is associated with spatiotemporally dynamic patterns of cholinergic release and enhanced large-scale network correlations. Overall, our findings demonstrate that ACh provides a highly dynamic and spatially heterogeneous signal that links fluctuations in behavior to functional reorganization of cortical networks.

neuroscience↗

bioRxiv2020

Tonic GABAergic activity facilitates dendritic calcium signaling and short-term plasticity

Brain activity is highly regulated by GABAergic activity, which acts via GABAARs to suppress somatic spike generation as well as dendritic synaptic integration and calcium signaling. Tonic GABAergic conductances mediated by distinct receptor subtypes can also inhibit neuronal excitability and spike output, though the consequences for dendritic calcium signaling are unclear. Here, we use 2-photon calcium imaging in cortical pyramidal neurons and computational modeling to show that low affinity GABAARs containing an 5 subunit mediate a tonic hyperpolarization of the dendritic membrane potential, resulting in deinactivation of voltage-gated calcium channels and a paradoxical boosting of action potential-evoked calcium influx. We also find that GABAergic enhancement of calcium signaling modulates short-term synaptic plasticity, augmenting depolarization-induced suppression of inhibition. These results demonstrate a novel role for GABA in the control of dendritic activity and suggest a mechanism for differential modulation of electrical and biochemical signaling.

neuroscience↗

bioRxiv2018

Simultaneous mesoscopic and two-photon imaging of neuronal activity in cortical circuits

Spontaneous and sensory-evoked activity propagates across spatial scales in the mammalian cortex but technical challenges have generally precluded establishing conceptual links between the function of local circuits of neurons and brain-wide network dynamics. To solve this problem, we developed a method for simultaneous cellular-resolution two-photon calcium imaging of a local microcircuit and mesoscopic widefield calcium imaging of the entire cortical mantle in awake, behaving mice. Our method employs an orthogonal axis design whereby the mesoscopic objective is oriented downward directly above the brain and the two-photon objective is oriented horizontally, with imaging performed through a glass right angle microprism implanted in the skull. In support of this method, we introduce a suite of analysis tools for relating the activity of individual cells to distal cortical areas, as well as a viral method for robust and widespread gene delivery in the juvenile mouse brain. We use these methods to characterize the diversity of associations of individual, genetically-defined neurons with cortex-wide network motifs.

neuroscience↗

bioRxiv2018

Ketamine disrupts neuromodulatory control of glutamatergic synaptic transmission.

A growing body of literature has demonstrated the potential for ketamine in the treatment of major depression. Sub-anesthetic doses produce rapid and sustained changes in depressive behavior, both in patients and rodent models, associated with reorganization of glutamatergic synapses in the prefrontal cortex (PFC). While ketamine is known to regulate NMDA-type glutamate receptors (NMDARs), the full complement of downstream cellular consequences for ketamine administration are not well understood. Here, we combine electrophysiology with 2-photon imaging and glutamate uncaging in acute slices of mouse PFC to further examine how ketamine alters glutamatergic synaptic transmission. We find that four hours after ketamine treatment, glutamatergic synapses themselves are not significantly affected. However, expression levels of the neuromodulatory Regulator of G-protein Signaling (RGS4) are dramatically reduced. This loss of RGS4 activity disrupts the normal compartmentalization of synaptic neuromodulation. Thus, under control conditions, 2 adrenergic receptors and GABAB receptors selectively inhibit AMPA-type glutamate receptors (AMPARs) and NMDARs, respectively. After ketamine-induced loss of RGS4 activity, this selectivity is lost, with both modulatory systems broadly inhibiting glutamatergic transmission. These results demonstrate a novel mechanism by which ketamine can influence synaptic signaling and provide new avenues for the exploration of therapeutics directed at treating neuropsychiatric disorders, such as depression.

neuroscience↗