The capacity to suppress learned responses is essential for animals to adapt in dynamic environments. Extinction is a process by which animals learn to suppress conditioned responding when an expected outcome is omitted. The infralimbic cortex (IL) to nucleus accumbens shell (NAcS) neural circuit is implicated in suppressing conditioned responding after extinction, especially in the context of operant cocaine-seeking behaviour. However, the role of the IL-to-NAcS neural circuit in the extinction of responding to appetitive Pavlovian cues is unknown and the psychological mechanisms involved in response suppression following extinction are unclear. We trained male, Long-Evans rats to associate a 10 s auditory conditioned stimulus (CS; 14 trials per session) with a sucrose unconditioned stimulus (US; 0.2 mL per CS) in a specific context and then, following extinction in a different context, precipitated a renewal of CS responding by presenting the CS alone in the original Pavlovian conditioning context. Unila...

Duloxetine, a serotonin and norepinephrine reuptake inhibitor (SNRI), is the best-established treatment for painful chemotherapy-induced peripheral neuropathy (CIPN). While it is only effective in little more than half of patients, our ability to predict patient response remains incompletely understood. Given that stress exacerbates CIPN, and that the therapeutic effect of duloxetine is thought to be mediated, at least in part, via its effects on adrenergic mechanisms, we evaluated the contribution of neuroendocrine stress axes, sympathoadrenal and hypothalamic-pituitary-adrenal (HPA), to the effect of duloxetine in preclinical models of oxaliplatin- and paclitaxel-induced CIPN. Systemic administration of duloxetine, which alone had no effect on nociceptive threshold, both prevented and reversed mechanical hyperalgesia associated with oxaliplatin- and paclitaxel-CIPN. It more robustly attenuated oxaliplatin CIPN in male rats, while it was more effective for paclitaxel CIPN in females. Gonadectomy attenuate...

Omnipause neurons (OPNs) in the nucleus raphe interpositus have tonic activity while the eyes are stationary (‘fixation’), but stop firing immediately before and during saccades. To locate the suppression’s source, we analyzed synaptic inputs from the rostral and caudal superior colliculi (SCs) to OPNs by using intracellular recording and staining, and investigated pathways transmitting the inputs in anesthetized cats of both sexes. Electrophysiologically- or morphologically-identified OPNs received monosynaptic excitation from the rostral SCs with contralateral dominance, and received disynaptic inhibition from the caudal SCs with ipsilateral dominance. Cutting the tectoreticular tract transversely between the contralateral OPN and inhibitory burst neuron (IBN) regions eliminated inhibition from the caudal SCs, but not excitation from the rostral SCs in OPNs. In contrast, a midline section between IBN regions eliminated disynaptic inhibition in OPNs from the caudal SCs, but did not affect the monosynaptic...

Long-term potentiation (LTP) and long-term depression (LTD) in the spinal dorsal horn reflect activity-dependent synaptic plasticity and central sensitization in chronic pain. Tetanic high-frequency stimulation is commonly used to induce LTP in the spinal cord. However, primary afferent nerves often display low-frequency, rhythmic bursting discharges in painful conditions. Here, we determined how theta-burst stimulation (TBS) of primary afferents impacts spinal cord synaptic plasticity and nociception. We found that TBS induced more LTP, whereas tetanic stimulation induced more LTD, in mouse spinal lamina II neurons. TBS induced LTP, but not LTD, in 50% of excitatory neurons expressing vesicular glutamate transporter-2 (VGluT2). By contrast, TBS induced LTD and LTP in 12%–16% of vesicular GABA transporter (VGAT)-expressing inhibitory neurons. Nerve injury significantly increased the prevalence of TBS-induced LTP in VGluT2-expressing, but not VGAT-expressing, lamina II neurons. Blocking NMDARs, inhibiting α...

Despite being canonically considered a motor control structure, the cerebellum is increasingly recognized for important roles in processes beyond this traditional framework, including seizure suppression. Excitatory fastigial neurons project to a large number of downstream targets, and it is unclear whether this broad targeting underlies seizure suppression, or whether a specific output may be sufficient. To address this question, we used the intrahippocampal kainic acid mouse model of temporal lobe epilepsy, male and female animals, and a dual-virus approach to selectively label and manipulate fastigial outputs. We examined fastigial neurons projecting to the superior colliculus, medullary reticular formation, and central lateral nucleus of the thalamus, and found that these comprise largely nonoverlapping populations of neurons that send collaterals to unique sets of additional, somewhat overlapping, thalamic and brainstem regions. We found that neither optogenetic stimulation of superior colliculus nor ...

In the article “Connecting TNF-α Signaling Pathways to iNOS Expression in a Mouse Model of Alzheimer's Disease: Relevance for the Behavioral and Synaptic Deficits Induced by Amyloid β Protein,” by Rodrigo Medeiros, Rui D. S. Prediger, Giselle F. Passos, Pablo Pandolfo, Filipe S. Duarte,

With the wide adoption of genomic sequencing in children having seizures, an increasing number of SCN2A genetic variants have been revealed as genetic causes of epilepsy. Voltage-gated sodium channel Nav1.2, encoded by gene SCN2A , is predominantly expressed in the pyramidal excitatory neurons and supports action potential (AP) firing. One recurrent SCN2A genetic variant is L1342P, which was identified in multiple patients with epileptic encephalopathy and intractable seizures. However, the mechanism underlying L1342P-mediated seizures and the pharmacogenetics of this variant in human neurons remain unknown. To understand the core phenotypes of the L1342P variant in human neurons, we took advantage of a reference human-induced pluripotent stem cell (hiPSC) line from a male donor, in which L1342P was introduced by CRISPR/Cas9-mediated genome editing. Using patch-clamping and microelectrode array (MEA) recordings, we revealed that cortical neurons derived from hiPSCs carrying heterozygous L1342P variant have...

Learned associations between stimuli allow us to model the world and make predictions, crucial for efficient behavior (e.g., hearing a siren, we expect to see an ambulance and quickly make way). While there are theoretical and computational frameworks for prediction, the circuit and receptor-level mechanisms are unclear. Using high-density EEG, Bayesian modeling, and machine learning, we show that inferred “causal” relationships between stimuli and frontal alpha activity account for reaction times (a proxy for predictions) on a trial-by-trial basis in an audiovisual delayed match-to-sample task which elicited predictions. Predictive β feedback activated sensory representations in advance of predicted stimuli. Low-dose ketamine, an NMDAR blocker, but not the control drug dexmedetomidine, perturbed behavioral indices of predictions, their representation in higher-order cortex, feedback to posterior cortex, and pre-activation of sensory templates in higher-order sensory cortex. This study suggests that predic...

How does the brain integrate signals with different timescales to drive purposeful actions? Brain-machine interfaces (BMIs) offer a powerful tool to causally test how distributed neural networks achieve specific neural patterns. During neuroprosthetic learning, actuator movements are causally linked to primary motor cortex (M1) neurons, i.e., “direct” neurons that project to the decoder and whose firing is required to successfully perform the task. However, it is unknown how such direct M1 neurons interact with both “indirect” local (in M1 but not part of the decoder) and across area neural populations (e.g., in premotor cortex/M2), all of which are embedded in complex biological recurrent networks. Here, we trained male rats to perform a M1-BMI task and simultaneously recorded the activity of indirect neurons in both M2 and M1. We found that both M2 and M1 indirect neuron populations could be used to predict the activity of the direct neurons (i.e., “BMI-potent activity”). Interestingly, compared with M1 ...