Biology subjects

Howard, C. D.

Publications and source records attributed to Howard, C. D..

5 recordsLinked to original sources

bioRxiv2021

Characterization of striatal dopamine projections across striatal subregions in behavioral flexibility

Behavioral flexibility is key to survival in a dynamic environment. While flexible, goal-directed behaviors are initially dependent on dorsomedial striatum, they become dependent on lateral striatum with extended training as behaviors become inflexible. Similarly, dopamine release shifts from ventromedial to lateral striatum across learning, and impairment of lateral dopamine release disrupts habitual, inflexible responding. This raises the possibility that lateral dopamine release is a causative mechanism in establishing inflexible behaviors late in training, though this has not been directly tested. Here, we utilized optogenetics to activate dopamine terminals in dorsal medial (DMS), dorsal lateral (DLS), and ventral (NAc) striatum in DATcre mice to determine how specific dopamine subpopulations impact behavioral flexibility. Mice performed a reversal task in which they self-stimulated DMS, DLS, or NAc dopamine terminals by pressing one of two levers before action-outcome lever contingencies were reversed. Consistent with presumed ventromedial/lateral striatal function, we found that mice self-stimulating ventromedial dopamine terminals rapidly reversed lever preference following contingency reversal, while mice self-stimulating dopamine terminals in DLS showed impaired reversal learning. These impairments were characterized by more regressive errors and reliance on lose-stay strategies following reversal, suggesting reward insensitivity and overreliance on previously learned actions. This study supports a model of striatal function in which dorsomedial dopamine facilitates goal-directed responding, and dorsolateral dopamine release is a key mechanism in supporting the transition toward inflexible behaviors.

neuroscience↗

bioRxiv2021

Colonization at birth with human CST IV cervicovaginal microbiota alters development and increases neonatal mortality in mice

Profound racial health disparities contribute to maternal-infant morbidity and mortality. An emergent risk factor is the maternal microbiota, whereby compositional alterations impact maternal health and offspring development during pregnancy and beyond. The presence of a nonoptimal CST IV cervicovaginal microbiota, more common in Black and Hispanic women, is associated with increased risk of preterm birth and adverse birth outcomes. Through examination of the biological mechanisms by which vertical transmission of microbiota from mother to offspring influences postnatal development, we found that exposing cesarean delivered mice with CST IV cervicovaginal microbiota from pregnant women produced lasting effects on offspring metabolic, immune, and neural outcomes. We then examined how compounding effects of a typical high-risk, proinflammatory in utero environment, characterized by a maternal obesogenic state and the presence of G. vaginalis, would affect the offspring response to CST IV microbial gut colonization. The resultant developmental immaturity, coupled with an exaggerated immune response induced by exposure to risk-associated maternal microbiota, resulted in a profound increase in neonatal mortality, supporting the critical importance of elucidating the multifactorial biological mechanisms involved in high-risk pregnancies. HighlightsO_LIGut colonization by nonoptimal human cervicovaginal microbiota had sex-specific effects on postnatal development. C_LIO_LIA high-risk in utero environment increased offspring mortality risk. C_LIO_LIHeightened innate immune response associated with mortality risk. C_LIO_LIDevelopmental immaturity, premature birth, and exposure to CST IV contribute to increased offspring mortality risk. C_LI

systems biology↗

bioRxiv2021

Nigrostriatal Dopamine Signals Sequence-Specific Action-Outcome Prediction Errors

Dopamine has been suggested to encode cue-reward prediction errors during Pavlovian conditioning. While this theory has been widely applied to reinforcement learning concerning instrumental actions, whether dopamine represents action-outcome prediction errors and how it controls sequential behavior remain largely unknown. Here, by training mice to perform optogenetic intracranial self-stimulation, we examined how self-initiated goal-directed behavior influences nigrostriatal dopamine transmission during single as well as sequential instrumental actions. We found that dopamine release evoked by direct optogenetic stimulation was dramatically reduced when delivered as the consequence of the animals own action, relative to non-contingent passive stimulation. This action-induced dopamine suppression was specific to the reinforced action, temporally restricted to counteract the expected outcome, and exhibited sequence-selectivity consistent with hierarchical control of sequential behavior. Together these findings demonstrate that nigrostriatal dopamine signals sequence-specific prediction errors in action-outcome associations, with fundamental implications for reinforcement learning and instrumental behavior in health and disease.

neuroscience↗

bioRxiv2020

Optogenetic interrogation of the role of striatal patches in habit formation and inhibition of striatal dopamine

Habits are inflexible behaviors that can be maladaptive in diseases including drug addiction. The striatum is integral to habit formation, and interspersed throughout the striatum are patches, or striosomes, which are characterized by unique gene expression relative to the surrounding matrix. Recent work has indicated that patches are necessary for habit formation, but how patches contribute to habits remains partially understood. Here, using optogenetics, we modulated striatal patches in Sepw1-NP67 mice during habit formation. We find that patch activation during operant training impairs habit formation, and conversely, that acute patch stimulation after reward devaluation can drive habitual reward seeking. Patch stimulation invigorates general locomotion but is not inherently rewarding. Finally, we use fast-scan cyclic voltammetry to demonstrate that patch stimulation suppresses dopamine release in dorsal striatum in vivo. Overall, this work provides novel insight into the role of the patch compartment in habit formation, and potential interactions with dopamine signaling.

neuroscience↗

bioRxiv2019

Lesion of striatal patches disrupts habitual behaviors and increases behavioral variability

Habits are automated behaviors that are insensitive to changes in behavioral outcomes. Habitual responding is thought to be mediated by striatum, with medial striatum guiding goal-directed action and lateral striatum promoting habits. However, interspersed throughout the striatum are neurochemically differing subcompartments known as patches, which are characterized by distinct molecular profiles relative to the surrounding matrix tissue. These structures have been thoroughly characterized neurochemically and anatomically, but little is known regarding their function. Patches have been shown to be selectively activated during inflexible motor stereotypies elicited by stimulants, suggesting that patches may subserve habitual behaviors. To explore this possibility, we utilized transgenic mice (Sepw1 NP67) expressing Cre recombinase in striatal patches to target these neurons for selective ablation with a virus driving Cre-dependent expression of caspase 3. Mice were then trained to press a lever for sucrose rewards on a variable interval schedule to elicit habitual responding. Mice were not impaired on the acquisition of this task, but lesioning striatal patches disrupted behavioral stability across training and lesioned mice utilized a more goal-directed behavioral strategy during training. Similarly, when mice were forced to omit responses to receive sucrose rewards, habitual responding was impaired in lesioned mice. To rule out effects of lesion on motor behaviors, mice were then tested for impairments in motor learning on a rotarod and locomotion in an open field. We found that patch lesions specifically impaired initial performance on the rotarod without modifying locomotor behaviors in open field. This work indicates that patches promote behavioral stability and habitual responding, adding to a growing literature implicating striatal patches in stimulus-response behaviors.

neuroscience↗