Biology subjects

Jackman, S. L.

Publications and source records attributed to Jackman, S. L..

4 recordsLinked to original sources

bioRxiv2026

Mice with impaired synaptic facilitation exhibit deficits in cognitive flexibility

Behavioral flexibility is crucial to animal survival in dynamic environments, and a failure to update actions in response to recent outcomes is a hallmark of many neuropsychiatric disorders. However, the cellular and circuit mechanisms in the brain that support behavioral flexibility remain poorly understood. Forms of short-term plasticity such as synaptic facilitation have been theorized to transiently maintain information in neural circuits, and flexibly modulate how circuits process information depending on recent activity. Despite theoretical support, there is no direct experimental evidence linking synaptic facilitation to flexible decision-making. Recently, the presynaptic calcium sensor Synaptotagmin-7 (Syt7) has been shown to be required for synaptic facilitation at many synapses in the mammalian brain. Here, we assess operant learning in male and female Syt7 KO mice to determine how facilitation contributes to learning both stable and dynamic reward contingencies. We find that Syt7 KO mice acquired stable contingencies similarly to wild-type controls. However, KO mice were impaired in learning dynamic contingencies, showed more perseverative responding, and were delayed in applying a new task rule to all trial types following reversal. Behavioral modeling revealed a reduced influence of recent trial history on decisions in KO mice compared to wild-type controls. The behavioral deficits could not be explained by differences in motivation or memory. These results suggest that synaptic facilitation supports adaptive decision-making and that disruptions of short-term plasticity impair animals ability to use recent outcomes to update behavior.

neuroscience↗

bioRxiv2021

Synaptotagmin-7 enhances phasic dopamine release

Dopamine released from substantia nigra pars compacta (SNc) neurons modulates movement, motivation, and reward. In addition to their tonic firing pattern, dopamine neurons also fire high-frequency bursts that cause superlinear increases in dopamine release. To study this poorly understood form of short-term plasticity, we used the fluorescent dopamine sensor dLight1.3b to examine the role of the calcium-binding protein synaptotagmin-7 (SYT7). We report that SYT7 mediates a hidden component of facilitation, which was unmasked by lowering initial release probability, or by low-frequency stimulation of nerve terminals. In Syt7 KO neurons, there was profound synaptic depression that significantly reduced release during stimulations that mimic in vivo firing patterns of SNc neurons. D2-mediated inhibitory postsynaptic currents in the SNc revealed a similar role for SYT7 in somatodendritic release. Our results indicate that SYT7 drives short-term facilitation of release from dopamine neurons, which likely underlies frequency-dependence of dopamine signaling in vivo.

neuroscience↗

bioRxiv2021

Fast resupply of synaptic vesicles requires Synaptotagmin-3

Sustained neuronal activity demands quick resupply of synaptic vesicles in order to maintain reliable synaptic transmission. Such vesicle replenishment is accelerated by sub-micromolar presynaptic Ca2+ signals by an as yet unidentified high-affinity Ca2+ sensor1-4. Here we identify a novel presynaptic role for the high-affinity Ca2+ sensor Synaptotagmin-3 (SYT3)5 in driving vesicle replenishment and short-term synaptic plasticity. Synapses in Syt3 knockout mice exhibit enhanced short-term depression, and recovery is slower and insensitive to presynaptic residual Ca2+. During sustained neuronal firing, SYT3 speeds vesicle replenishment and increases the size of the readily releasable pool of vesicles. SYT3 also mediates a second form of short-term enhancement called facilitation, under conditions of low vesicle release probability. Models of vesicle trafficking suggest that SYT3 could combat synaptic depression by accelerating vesicle docking at active zones. Our results reveal a critical role for presynaptic SYT3 in maintaining reliable high-frequency synaptic transmission in neural circuits.

neuroscience↗

bioRxiv2020

Cerebellar Purkinje cell activity modulates aggressive behavior

Although the cerebellum is traditionally associated with balance and motor function, it also plays wider roles in affective and cognitive behaviors. Evidence suggests that the cerebellar vermis may regulate aggressive behavior, though the cerebellar circuits and patterns of activity that influence aggression remain unclear. We used optogenetic methods to bidirectionally modulate the activity of spatially-delineated cerebellar Purkinje cells to evaluate the impact on aggression in mice. Increasing Purkinje cell activity in the vermis significantly reduced the frequency of attacks in a resident-intruder assay. Reduced aggression was not a consequence of impaired motor function, because optogenetic stimulation did not alter motor performance. In complementary experiments, optogenetic inhibition of Purkinje cells in the vermis increased the frequency of attacks. These results establish Purkinje cell activity in the cerebellar vermis regulates aggression, and further support the importance of the cerebellum in driving affective behaviors that could contribute to neurological disorders.

neuroscience↗