Neuronal populations connected by gap junctions can be revealed via dye coupling of small molecules like neurobiotin and Lucifer yellow. However, the extent of dye diffusion between neurons varies with connexin subtype, loading method, and neuromodulation. Due to the increasing availability of GCaMP transgenic animals, we explore the possibility of revealing gap junctional coupling using Ca2+ imaging in the motor system of Xenopus laevis tadpole of either sex. Reliable axo-axonal electrical coupling was previously found in excitatory descending interneurons (dINs) using paired recordings but not with neurobiotin dye coupling. Here, we made whole-cell patch–clamp recordings with Ca2+-supplemented intracellular solution to load Ca2+ into GCaMP6-expressing neurons, followed by Ca2+ imaging to detect potential Ca2+ diffusion across coupled neurons. Successful membrane breakthroughs led to transient fluorescence increases in the patched neuron. However, increasing the Ca2+ concentration promoted membrane reseal...

Sensorimotor adaptation depends on implicit recalibration and explicit strategy. These processes are commonly assumed to sum ( A  =  I  +  E ), and this additivity assumption justifies subtractive measurement and informs computational models of motor learning. Recent work has challenged additivity by examining regression slopes between implicit and explicit measures. When slopes deviate from β  = −1, the interpretation has been that the processes are “sub-additive” and fail to sum as expected. Here, we show this reasoning is mistaken. Regression slopes reflect covariance structure: how learning processes relate across individuals. Additivity is a claim about motor output combination: whether learning processes sum within individuals. These are different questions, and regression slopes do not address the latter. We derive the expected slope under subtractive logic and show it equals β  = −1 only when total adaptation is uncorrelated with the measured component. Monte Carlo simulations confirm this benchmar...

In the article “Is Social Media Use a Blessing or Cure for Motor Function and Skill Acquisition? An Opinion …

Synaptic physiology experiments are fundamental to neuroscience research. Consequently, accurate detection of synaptic currents is crucial for conducting high-quality experiments. Traditionally, detecting inhibitory and excitatory postsynaptic currents (sIPSCs/sEPSCs) relied on hand-counting individual events. Although sEPSCs and sIPSCs are clear to the trained eye, hand analysis is time and labor intensive. Recent advances in applied machine learning promise faster, superior event detectors that may improve data quality and reduce or even completely negate the need for hand curation. While many strategies for sIPSC and sEPSC detection exist, rarely have they been quantitatively compared for accuracy within an experiment. Our study aims to establish practical ground-truth event detection in a large experimental dataset through meticulous hand counting and to assess variance in detection results across different laboratories, analysis techniques, and cell types. Using thoroughly hand-counted data as our gro...

We describe a novel method for adapting a two-photon scanning microscope to enable simultaneous detection of two-photon-generated visible fluorescence and single-photon-generated near-infrared (nIR) fluorescence. In this configuration, nIR fluorescence is routed through a single-mode optical fiber before detection by a photomultiplier tube. This fiber coupling offers two advantages: first, the optical fiber functions as a pinhole aperture, allowing for improved optical sectioning of the nIR signal; second, it minimizes nIR background fluorescence. To validate the effectiveness of this design, we conducted two sets of experiments in male and female C57B/6J mice. First, we compare two fluorescence indicators of the neurotransmitter dopamine: the genetically encoded indicator GRABDA and single-walled carbon nanotube-based optical nanosensors (nIRCats). Although nIRCats exhibit lower affinity for dopamine than GRABDA, this property allows for identification of high concentration release sites in the striatum. ...

There is considerable interest in cannabinoid-based therapies to treat pain, but activation of the endogenous cannabinoid (endocannabinoid) system can elicit pro- and anti-nociceptive effects. This study tests the hypothesis that the concentration of the endocannabinoid arachidonoylethanolamine (AEA) contributes to whether pro- or anti-nociceptive effects are observed. Experiments were carried out using isolated ganglia from the medicinal leech Hirudo verbana where it is possible to selectively record from nociceptive and non-nociceptive synapses in the central nervous system (CNS). Previous studies using Hirudo have shown that endocannabinoids depress nociceptive (N) sensory cell synapses and potentiate of non-nociceptive pressure (P) sensory cell synapses. In this study, exogenously applied AEA produced depression of N synapses and potentiation of P synapses across the same range of concentrations. However, the results differed when using URB597, a drug that raises AEA by inhibiting fatty acid amine hydr...

Multi-electrode recording of neuronal activity in cultures offer opportunities for understanding how the structure of a network gives rise to function. Neuronal cultures derived from human induced pluripotent stem cells (iPSCs) from male and female individuals are often plated at highly variable cell densities across studies, but its impact on neuronal activity remains poorly understood. We found that properties such as the mean firing rate of the individual cells, the pairwise correlations between cells, and the entropy of the population all changed significantly with changes in culture density. We used a maximum entropy model to capture the structure of the population activity using only the firing rates and correlations, and we found that the model performed best at the highest densities, suggesting that changes in activity reflected differences in structure of interactions between neurons across scales of complexity. Our work thus shows that culture density is an important experimental parameter that i...

The suprachiasmatic nucleus (SCN) produces diffusible signals sufficient to sustain circadian locomotor rhythms, although the nature of such signals, their targets, and the pathway whereby such signals may travel is unknown. It is possible that the venous portal veins that connect the capillary beds of the SCN to those of the organum vasculosum of the lamina terminalis (OVLT) provide a vascular pathway whereby signals originating in SCN neurons can reach local targets in the OVLT. Given the presence of the blood–brain interface (BBI) within the SCN, it is unclear how diffusible signals originating in SCN neurons might access the capillary vasculature of this nucleus. Estimates of astrocyte coverage of capillary vasculature range widely, from 70 to 100%, and furthermore such coverage can change dynamically. In the present study, we investigated whether three vasoactive peptidergic processes found in the mouse SCN, namely, vasopressin, vasoactive intestinal peptide, and gastrin-releasing peptide, might breac...

Dopamine D1 receptor (D1R) signaling in the brain has been strongly implicated in multiple cognitive processes, with D1 agonists known to enhance performance. The development of functionally selective D1 agonists that differentially activate D1R-mediated cAMP versus β-arrestin signaling may offer precision therapy if we understand how signaling bias impacts integrated cognitive processes in complex tasks. We therefore examined the effects of two selective D1 agonists, 2-methyldihydrexidine (2MDHX) and PF-06256142 (PF), on a rodent touchscreen-based Trial-Unique Nonmatching-To-Location task. Primarily assessing both spatial working memory and pattern separation in adult male rats, this behavioral paradigm requires greater cognitive demands to maintain performance throughout the testing session, significantly increasing task complexity. Our results revealed an inverted U-shaped dose response curve for both compounds, aligning with our previously published work, but did not demonstrate marked improvement in t...

With repeated exposure to addictive drugs, there is a shift from drug abuse to drug addiction that is mediated by the transition from goal-directed to habitual control. It is well known that the development of habitual control over behavior relies upon cell-type-specific synaptic changes in both D1 and D2 medium spiny neurons (MSNs) in dorsal striatum. Specifically, habitual behavior is mediated by increased synaptic strength in D1 and D2 MSNs in dorsolateral striatum (DLS), suggesting similar cell-type-specific synaptic changes may underlie the development of habitual cocaine-seeking behavior. However, cell-type-specific synaptic changes have not been evaluated in DLS in this context. Therefore, we trained male rats to self-administer cocaine in a self-administration paradigm that allows for differentiation of goal-directed versus habitual cocaine-seeking behavior. Moreover, we used a viral vector under a D2-specific promoter to fluorescently label D2 MSNs with eYFP in DLS. Evoked excitatory postsynaptic ...