Decreased amplitude and reliability of odor-evoked responses in two mouse models of autism.

Sensory processing deficits are increasingly recognized as core symptoms of autism spectrum disorders (ASDs). However the molecular and circuit mechanisms that lead to sensory deficits are unknown. We show that two molecularly disparate mouse models of autism display similar deficits in sensory-evoked responses in the mouse olfactory system. We find that both Cntnap2- and Shank3-deficient mice of both sexes exhibit reduced response amplitude and trial-to-trial reliability during repeated odor presentation. Mechanistically, we show that both mouse models have weaker and fewer synapses between olfactory sensory nerve (OSN) terminals and olfactory bulb tufted cells and weaker synapses between OSN terminals and inhibitory periglomerular cells. Consequently, deficits in sensory processing provide an excellent candidate phenotype for analysis in ASDs.NEW & NOTEWORTHY The genetics of autism spectrum disorder (ASD) are complex. How the many risk genes generate the similar sets of symptoms that define the disorder is unknown. In particular, little is understood about the functional consequences of these genetic alterations. Sensory processing deficits are important aspects of the ASD diagnosis and may be due to unreliable neural circuits. We show that two mouse models of autism, Cntnap2- and Shank3-deficient mice, display reduced odor-evoked response amplitudes and reliability. These data suggest that altered sensory-evoked responses may constitute a circuit phenotype in ASDs.

The two-step task, avoidance, and OCD.

In this invited review, we argue for the need to determine whether appetitive and aversive behaviors, be they goal-directed or habitual, share overlapping neural circuitry. To motivate our argument, we first summarize what is currently known about the neural circuits governing aversive and appetitive behaviors by focusing first on the three hypothesized phases of avoidance learning, and then on goal-directed and habitual reward seeking. We then provide several reasons to believe that the neural circuits of appetitive and aversive instrumental behaviors are not completely overlapping. We next discuss an experimental strategy to determine the extent of overlap based on a new computational framework that improves the identification of goal-directed and habitual actions regardless of valence. Finally, we discuss recent work in obsessive-compulsive disorder that uses this computational framework to determine whether patients perform appetitive and aversive versions of the same task using the same behavioral strategies and neural circuits.

Distinct Patterns of Abnormal Lateral Orbitofrontal Cortex Activity During Compulsive Grooming and Reversal Learning Normalize After Fluoxetine.

BACKGROUND: Patients with obsessive-compulsive disorder (OCD) display disrupted performance and abnormal lateral orbitofrontal cortex (LOFC) activity during reversal learning tasks. However, it is unknown whether compulsions and reversal learning deficits share a common neural substrate. To answer this question, we measured neural activity with in vivo calcium imaging in LOFC during compulsive grooming and reversal learning before and after fluoxetine treatment. METHODS: Sapap3 knockout (KO) mice were used as a model for OCD-relevant behaviors. Sapap3 KOs and control littermates were injected with a virus encoding GCaMP6f and implanted with gradient-index lenses to visualize LOFC activity using miniature microscopes. Grooming, reversal learning, and neural activity were measured pre- and post-fluoxetine treatment (18 mg/kg, 4 weeks). RESULTS: Baseline compulsive grooming and reversal learning impairments in KOs improved after fluoxetine treatment. In addition, KOs displayed distinct patterns of abnormal LOFC activity during grooming and reversal learning, both of which normalized after fluoxetine. Finally, reversal learning-associated neurons were distributed randomly among grooming-associated neurons (i.e., overlap is what would be expected by chance). CONCLUSIONS: In OCD, LOFC is disrupted during both compulsive behaviors and reversal learning, but whether these behaviors share common neural underpinnings is unknown. We found that LOFC plays distinct roles in compulsive grooming and impaired reversal learning and their improvement with fluoxetine. These findings suggest that LOFC plays separate roles in pathophysiology and treatment of different perseverative behaviors in OCD.

Synaptic Variability and Cortical Gamma Oscillation Power in Schizophrenia.

OBJECTIVE: Cognitive impairments in schizophrenia are associated with lower gamma oscillation power in the prefrontal cortex (PFC). Gamma power depends in part on excitatory drive to fast-spiking parvalbumin interneurons (PVIs). Excitatory drive to cortical neurons varies in strength, which could affect how these neurons regulate network oscillations. The authors investigated whether variability in excitatory synaptic strength across PVIs could contribute to lower prefrontal gamma power in schizophrenia. METHODS: In postmortem PFC from 20 matched pairs of comparison and schizophrenia subjects, levels of vesicular glutamate transporter 1 (VGlut1) and postsynaptic density 95 (PSD95) proteins were quantified to assess variability in excitatory synaptic strength across PVIs. A computational model network was then used to simulate how variability in excitatory synaptic strength across fast-spiking (a defining feature of PVIs) interneurons (FSIs) regulates gamma power. RESULTS: The variability of VGlut1 and PSD95 levels at excitatory inputs across PVIs was larger in schizophrenia relative to comparison subjects. This alteration was not influenced by schizophrenia-associated comorbid factors, was not present in monkeys chronically exposed to antipsychotic medications, and was not present in calretinin interneurons. In the model network, variability in excitatory synaptic strength across FSIs regulated gamma power by affecting network synchrony. Finally, greater synaptic variability interacted synergistically with other synaptic alterations in schizophrenia (i.e., fewer excitatory inputs to FSIs and lower inhibitory strength from FSIs) to robustly reduce gamma power. CONCLUSIONS: The study findings suggest that greater variability in excitatory synaptic strength across PVIs, in combination with other modest synaptic alterations in these neurons, can markedly lower PFC gamma power in schizophrenia.

Decreased severity of Shiga toxin-producing Escherichia coli haemolytic uraemic syndrome (STEC-HUS) in a child with type 1 von Willebrand disease.

Shiga toxin-producing Escherichia coli-associated haemolytic uraemic syndrome (STEC-HUS) is characterised by haemolytic anaemia, thrombocytopenia and acute kidney injury. Von Willebrand Factor (vWF) is an important mediator of normal thrombi formation and indirect evidence suggests that vWF may play an important role in Shiga toxin-induced thrombi formation. Clinical evidence supporting the role of vWF in STEC-HUS is lacking. A 10-year-old girl with type 1 von Willebrand Disease (vWD) had a mild case of STEC-HUS, with nadir haemoglobin 7.3 g/dL and platelet count 105×109 cells/L and peak serum creatinine 0.56 mg/L and lactate dehydrogenase 741 U/L. This is the first report of STEC-HUS in a patient with vWD. We speculate that the quantitative deficiency of vWF associated with type 1 vWD may have attenuated the course of disease by reducing platelet aggregation, complement activation and thrombi formation. This case adds to a growing literature supporting a link between vWF and STEC-HUS.

Distinct lateral inhibitory circuits drive parallel processing of sensory information in the mammalian olfactory bulb.

Splitting sensory information into parallel pathways is a common strategy in sensory systems. Yet, how circuits in these parallel pathways are composed to maintain or even enhance the encoding of specific stimulus features is poorly understood. Here, we have investigated the parallel pathways formed by mitral and tufted cells of the olfactory system in mice and characterized the emergence of feature selectivity in these cell types via distinct lateral inhibitory circuits. We find differences in activity-dependent lateral inhibition between mitral and tufted cells that likely reflect newly described differences in the activation of deep and superficial granule cells. Simulations show that these circuit-level differences allow mitral and tufted cells to best discriminate odors in separate concentration ranges, indicating that segregating information about different ranges of stimulus intensity may be an important function of these parallel sensory pathways.