Publications by authors named "Berke J"

Article Synopsis
  • The study investigates how the brain represents and selects alternative possibilities during navigation in a complex environment, specifically focusing on the rat hippocampus.
  • Researchers found that rats represented multiple potential paths, both ahead and behind them, and that these representations changed based on the value of the rewards associated with different paths.
  • The findings suggest that the brain adjusts how it generates alternatives to support decision-making, helping animals adapt to their changing environment and cognitive requirements.
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Article Synopsis
  • Striatal acetylcholine and dopamine play critical roles in regulating movement, motivation, and how we learn about rewards.
  • Researchers studied cholinergic interneuron (CIN) firing during decision-making in freely moving rats and found that CIN activity and dopamine release varied significantly across different striatal regions.
  • In the dorsal-lateral striatum, CIN firing patterns were not linked to reward prediction errors (RPE), while in the ventral striatum, both CINs and dopamine increased in response to rewards, highlighting complex interactions within the striatum.
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Living cells have spontaneous ultraweak photon emission derived from metabolic reactions associated with physiological conditions. The ORCA-Quest CMOS camera (Hamamatsu Photonics, Japan) is a highly sensitive and essential tool for photon detection; its use with a microscope incubator (Olympus) enables the detection of photons emitted by embryos with the exclusion of harmful visible light. With the application of the second law of thermodynamics, the low-entropy energy absorbed and used by embryos can be distinguished from the higher-entropy energy released and detectable in their environment.

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Acetylcholine is widely believed to modulate the release of dopamine in the striatum of mammals. Experiments in brain slices clearly show that synchronous activation of striatal cholinergic interneurons is sufficient to drive dopamine release via axo-axonal stimulation of nicotinic acetylcholine receptors. However, evidence for this mechanism in vivo has been less forthcoming.

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Animals make predictions to guide their behavior and update those predictions through experience. Transient increases in dopamine (DA) are thought to be critical signals for updating predictions. However, it is unclear how this mechanism handles a wide range of behavioral timescales-from seconds or less (for example, if singing a song) to potentially hours or more (for example, if hunting for food).

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Unlabelled: Capsid assembly is critical in the hepatitis B virus (HBV) life cycle, mediated by the viral core protein. Capsid assembly is the target for new anti-viral therapeutics known as capsid assembly modulators (CAMs) of which the CAM-aberrant (CAM-A) class induces aberrant shaped core protein structures and leads to hepatocyte cell death. This study aimed to identify the mechanism of action of CAM-A modulators leading to HBV-infected hepatocyte elimination where CAM-A-mediated hepatitis B surface antigen (HBsAg) reduction was evaluated in a stable HBV replicating cell line and in AAV-HBV-transduced C57BL/6, C57BL/6 SCID, and HBV-infected chimeric mice with humanized livers.

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Acetylcholine is widely believed to modulate the release of dopamine in the striatum of mammals. Experiments in brain slices clearly show that synchronous activation of striatal cholinergic interneurons is sufficient to drive dopamine release via axo-axonal stimulation of nicotinic acetylcholine receptors. However, evidence for this mechanism has been less forthcoming.

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Basal ganglia (BG) circuits help guide and invigorate actions using predictions of future rewards (values). Within the BG, the globus pallidus pars externa (GPe) may play an essential role in aggregating and distributing value information. We recorded from the GPe in unrestrained rats performing both Pavlovian and instrumental tasks to obtain rewards and distinguished neuronal subtypes by their firing properties across the wake/sleep cycle and optogenetic tagging.

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Animals frequently make decisions based on expectations of future reward ("values"). Values are updated by ongoing experience: places and choices that result in reward are assigned greater value. Yet, the specific algorithms used by the brain for such credit assignment remain unclear.

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Motivation to work for potential rewards is critically dependent on dopamine (DA) in the nucleus accumbens (NAc). DA release from NAc axons can be controlled by at least two distinct mechanisms: (1) action potentials propagating from DA cell bodies in the ventral tegmental area (VTA), and (2) activation of β2* nicotinic receptors by local cholinergic interneurons (CINs). How CIN activity contributes to NAc DA dynamics in behaving animals is not well understood.

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Dopamine in the nucleus accumbens helps motivate behavior based on expectations of future reward ("values"). These values need to be updated by experience: after receiving reward, the choices that led to reward should be assigned greater value. There are multiple theoretical proposals for how this credit assignment could be achieved, but the specific algorithms that generate updated dopamine signals remain uncertain.

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Hepatitis B virus (HBV) capsid assembly modulators (CAMs) represent a recent class of anti-HBV antivirals. CAMs disturb proper nucleocapsid assembly, by inducing formation of either aberrant assemblies (CAM-A) or of apparently normal but genome-less empty capsids (CAM-E). Classical structural approaches have revealed the CAM binding sites on the capsid protein (Cp), but conformational information on the CAM-induced off-path aberrant assemblies is lacking.

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Suppressing actions is essential for flexible behavior. Multiple neural circuits involved in behavioral inhibition converge upon a key basal ganglia output nucleus, the substantia nigra pars reticulata (SNr). To examine how changes in basal ganglia output contribute to self-restraint, we recorded SNr neurons during a proactive behavioral inhibition task.

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Food and water are rewarding in part because they satisfy our internal needs. Dopaminergic neurons in the ventral tegmental area (VTA) are activated by gustatory rewards, but how animals learn to associate these oral cues with the delayed physiological effects of ingestion is unknown. Here we show that individual dopaminergic neurons in the VTA respond to detection of nutrients or water at specific stages of ingestion.

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Background: Prone positioning improves mortality in patients intubated with acute respiratory distress syndrome and has been proposed as a treatment for nonintubated patients with COVID-19 outside the ICU. However, there are substantial patient and operational barriers to prone positioning on acute floors. The objective of this project was to increase the frequency of prone positioning among acute care patients with COVID-19.

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The strength of cortical connectivity to the striatum influences the balance between behavioral variability and stability. Learning to consistently produce a skilled action requires plasticity in corticostriatal connectivity associated with repeated training of the action. However, it remains unknown whether such corticostriatal plasticity occurs during training itself or 'offline' during time away from training, such as sleep.

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Background: A central goal of systems neuroscience is to understand the relationships amongst constituent units in neural populations, and their modulation by external factors, using high-dimensional and stochastic neural recordings. Parametric statistical models (e.g.

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Hepatitis B Virus (HBV) core protein has multiple functions in the viral life cycle and is an attractive target for new anti-viral therapies. Capsid assembly modulators (CAMs) target the core protein and induce the formation of either morphologically normal (CAM-N) or aberrant structures (CAM-A), both devoid of genomic material. To date a diverse family of CAM-N chemotypes has been identified, but in contrast, described CAM-As are based on the heteroaryldihydropyrimidine (HAP) scaffold.

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Objective: Multimodal measurements at the neuronal level allow for detailed insight into local circuit function. However, most behavioral studies focus on one or two modalities and are generally limited by the available technology.

Approach: Here, we show a combined approach of electrophysiology recordings, chemical sensing, and histological localization of the electrode tips within tissue.

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Neural implants with large numbers of electrodes have become an important tool for examining brain functions. However, these devices typically displace a large intracranial volume compared with the neurons they record. This large size limits the density of implants, provokes tissue reactions that degrade chronic performance, and impedes the ability to accurately visualize recording sites within intact circuits.

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Article Synopsis
  • Researchers developed a new red-shifted dopamine sensor called RdLight1, which allows for high-resolution imaging of dopamine dynamics in animals while avoiding interference with existing green fluorescent protein (GFP)-based sensors. !* -
  • RdLight1 demonstrates excellent photostability and can be utilized for receptor-specific pharmacological studies, tracking dopamine release, and monitoring neuronal activity in live animals. !* -
  • The study found that dopamine release in the nucleus accumbens triggered by reward-predictive cues results in a quick suppression of glutamate release, highlighting RdLight1's potential for exploring complex interactions within neural circuits. !*
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Four weeks of once-daily oral JNJ-56136379 (JNJ-6379; 25, 75, 150 or 250 mg), a class-N capsid assembly modulator (CAM-N), was well tolerated with potent antiviral activity in treatment-naïve, chronic hepatitis B e antigen-positive and hepatitis B e antigen-negative patients (NCT02662712). Hepatitis B virus (HBV) genome sequence analysis, using HBV DNA next-generation sequence technology, was performed, and impact of substitutions on efficacy was assessed. Analyses focused on HBV core protein amino acid positions associated with JNJ-6379 and/or other CAMs in vitro resistance, and those within the CAM-binding pocket.

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Flexible behavior requires restraint of actions that are no longer appropriate. This behavioral inhibition critically relies on frontal cortex - basal ganglia circuits. Within the basal ganglia, the globus pallidus pars externa (GPe) has been hypothesized to mediate selective proactive inhibition: being prepared to stop a specific action, if needed.

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Objectives: To characterize antiviral activity of the capsid assembly modulator (CAM-N) JNJ-56136379 against HBV genotypes and variants carrying amino acid substitutions in the core protein.

Methods: Anti-HBV activity of JNJ-56136379 was investigated against a diverse panel of 53 HBV clinical isolates (genotypes A-H). The impact of core amino acid substitutions using site-directed mutants (SDMs) was assessed in a transient replication assay.

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Spindles and slow oscillations (SOs) both appear to play an important role in memory consolidation. Spindle and SO "nesting," or the temporal overlap between the two events, is believed to modulate consolidation. However, the neurophysiological processes modified by nesting remain poorly understood.

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