In recent years there has been extensive research on malformations of cortical development (MCDs) that result in clinical features like developmental delay, intellectual disability, and drug-resistant epilepsy (DRE). Various studies highlighted the contribution of microtubule-associated genes (including tubulin and kinesin encoding genes) in MCD development. It has been reported that de novo mutations in KIF2A , a member of the kinesin-13 family, are linked to brain malformations and DRE. Although it is known that KIF2A functions by regulating microtubule depolymerization via an ATP-driven process, in vivo implications of KIF2A loss of function remain partly unclear. Here, we present a novel kif2a knockout zebrafish model, showing hypoactivity, habituation deficits, PTZ-induced seizure susceptibility and microcephaly as well as neuronal cell proliferation defects and increased apoptosis. Interestingly, kif2a-/- larvae survived until adulthood and were fertile. Notably, our kif2a zebrafish knockout model de...

Cortical processing of arithmetic and of language rely on both shared and task-specific neural mechanisms, which should also be dissociable from the particular sensory modality used to probe them. Here, spoken arithmetical and non-mathematical statements were employed to investigate neural processing of arithmetic, compared to general language processing, in an attention-modulated cocktail party paradigm. Magnetoencephalography (MEG) data were recorded from 22 human subjects listening to audio mixtures of spoken sentences and arithmetic equations while selectively attending to one of the two speech streams. Short sentences and simple equations were presented diotically at fixed and distinct word/symbol and sentence/equation rates. Critically, this allowed neural responses to acoustics, words, and symbols to be dissociated from responses to sentences and equations. Indeed, the simultaneous neural processing of the acoustics of words and symbols was observed in auditory cortex for both streams. Neural respon...

Excitatory synaptic inputs arriving at the dendrites of a neuron can engage active mechanisms that nonlinearly amplify the depolarizing currents. This supralinear synaptic integration is subject to modulation by inhibition. However, the specific rules by which different subtypes of interneurons affect the modulation have remained largely elusive. To examine how inhibition influences active synaptic integration, we optogenetically manipulated the activity of two subtypes of interneurons: dendrite-targeting somatostatin-expressing ( SST ) interneurons and perisomatic-targeting parvalbumin-expressing ( PV ) interneurons. In acute slices of mouse primary visual cortex, electrical stimulation evoked nonlinear synaptic integration that depended on N -methyl-D-aspartate ( NMDA ) receptors. Optogenetic activation of SST interneurons in conjunction with electrical stimulation resulted in predominantly divisive inhibitory gain control, reducing the magnitude of the supralinear response without affecting its threshol...

Gene expression analysis in individual neuronal types helps understand brain function. Genetic methods expressing fluorescent proteins are widely used to label specific neuronal populations. However, because cell type specificity of genetic labeling is often limited, it is advantageous to combine genetic labelling with additional methods to select specific cell/neuronal types. Laser capture microdissection is one of such techniques with which one can select a specific cell/neuronal population based on morphological observation. However, a major issue is disappearance of fluorescence signals during tissue processing required for high quality sample preparation. Here, we developed a simple, novel method in which fluorescence signals are preserved. We use genetic labeling with fluorescence proteins fused to transmembrane proteins, which shows highly stable fluorescence retention and allows for the selection of fluorescent neurons/cells based on morphology. Using this method in mice, we laser-captured neuronal...

The size and structure of the dendritic arbor play important roles in determining how synaptic inputs of neurons are converted to action potential output. The regulatory mechanisms governing the development of dendrites, however, are insufficiently understood. The evolutionary conserved Ste20/Hippo kinase pathway has been proposed to play an important role in regulating the formation and maintenance of dendritic architecture. A key element of this pathway, Ste20-like kinase (SLK), regulates cytoskeletal dynamics in non-neuronal cells and is strongly expressed throughout neuronal development. However, its function in neurons is unknown. We show that during development of mouse cortical neurons, SLK has a surprisingly specific role for proper elaboration of higher, ≥ 3rd, order dendrites both in male and in female mice. Moreover, we demonstrate that SLK is required to maintain excitation-inhibition balance. Specifically, SLK knockdown caused a selective loss of inhibitory synapses and functional inhibition a...

Neurotransmitter spillover is a form of communication not readily predicted by anatomical structure. In the cerebellum, glutamate spillover from climbing fibers recruits molecular layer interneurons in the absence of conventional synaptic connections. Spillover-mediated signaling is typically limited by transporters that bind and reuptake glutamate. Here, we show that patterned expression of the excitatory amino acid transporter 4 (EAAT4) in Purkinje cells regulates glutamate spillover to molecular layer interneurons. Using male and female Aldolase C-Venus knock-in mice to visualize Zebrin microzones, we find larger climbing fiber-evoked spillover EPSCs in regions with low levels of EAAT4 compared to regions with high EAAT4. This difference is not explained by presynaptic glutamate release properties or postsynaptic receptor density but rather by differences in the glutamate concentration reaching receptors on interneurons. Inhibiting glutamate transport normalizes the differences between microzones, sugge...

Pain is the major debilitating symptom of osteoarthritis (OA), which is difficult to treat. In OA patients joint tissue damage only poorly associates with pain, indicating other mechanisms contribute to OA pain. Immune cells regulate the sensory system, but little is known about their involvement in OA pain. Here we report that macrophages accumulate in the dorsal root ganglia (DRG) distant from the site of injury in two rodent models of OA. DRG macrophages acquired a M1-like phenotype and depletion of DRG macrophages resolved OA pain in male and female mice. Sensory neurons innervating the damaged knee joint shape DRG macrophages into a M1-like phenotype. Persisting OA pain, accumulation of DRG macrophages, and their programming into M1-like phenotype was independent of Nav1.8 nociceptors. Inhibition of M1-like macrophages in the DRG, by intrathecal injection of a IL4-IL10 fusion protein or M2-like macrophages resolved persistent OA pain. In conclusion, these findings reveal a crucial role for macrophages...

Spatial orientation memory plays a crucial role in animal navigation. Recent studies of tethered Drosophila melanogaster (fruit fly) in a virtual reality setting showed that the head direction is encoded in the form of an activity bump, i.e. localized neural activity, in the torus-shaped ellipsoid body (EB). However, how this system is involved in orientation working memory is not well understood. We investigated this question using free moving flies ( Drosophila melanogaster ) in a spatial orientation memory task by manipulating two EB subsystems, C and P circuits, which are hypothesized for stabilizing and updating the activity bump, respectively. To this end, we suppressed or activated two types of inhibitory ring neurons (EIP and P) which innervate EB, and we discovered that manipulating the two inhibitory neuron types produced distinct behavioral deficits, suggesting specific roles of the inhibitory neurons in coordinating the stabilization and updating functions of the EB circuits. We further elucida...

Complex perceptual decisions, in which information must be integrated across multiple sources of evidence, are ubiquitous but are not well understood. Such decisions rely on sensory processing of each individual source of evidence, and are therefore vulnerable to bias if sensory processing resources are disproportionately allocated amongst visual inputs. To investigate this, we developed an implicit neurofeedback protocol embedded within a complex decision-making task to bias sensory processing in favour of one source of evidence over another. Human participants of both sexes ( N =30) were asked to report the average motion direction across two fields of oriented moving bars. Bars of different orientations flickered at different frequencies, thus inducing steady-state visual evoked potentials (SSVEPs). Unbeknownst to participants, neurofeedback was implemented to implicitly reward attention to a specific “trained” orientation (rather than any particular motion direction). As attentional selectivity for thi...

Entorhinal cortex (EC) neurons make monosynaptic connections onto distal apical dendrites of CA1 and CA2 pyramidal neurons (PNs) through the perforant path (PP) projection. Previous studies show that differences in dendritic properties and synaptic input density enable the PP inputs to produce a much stronger excitation of CA2 compared to CA1 PNs. Here, using mice of both sexes, we report that the difference in PP efficacy varies substantially as a function of presynaptic firing rate. Although a single PP stimulus evokes a 5-6 fold greater EPSP in CA2 compared to CA1, a brief high-frequency train of PP stimuli evokes a strongly facilitating postsynaptic response in CA1, with relatively little change in CA2. Furthermore, we demonstrate that blockade of NMDARs significantly reduces strong temporal summation in CA1, but has little impact on that in CA2. As a result of the differences in the frequency- and NMDAR-dependent temporal summation, naturalistic patterns of presynaptic activity evoke CA1 and CA2 respo...