Zona Incerta Research Articles

Whole-Brain Monosynaptic Afferents to Rostromedial Tegmental Nucleus Gamma-Aminobutyric Acid-Releasing Neurons in Mice.

Increasing evidence has revealed that the rostromedial tegmental area (RMTg) mediates many behaviors, including sleep and addiction. However, presynaptic patterns governing the activity of γ-aminobutyric acid-releasing (GABAergic) neurons, the main neuronal type in the RMTg, have not been defined. Here, we used cell-type-specific retrograde trans-synaptic rabies viruses to map and quantify the monosynaptic afferents to RMTg GABAergic neurons in mouse whole brains. We identified 71 ascending projection brain regions. Sixty-eight percent of the input neurons arise from the ipsilateral and 32% from the contralateral areas of the brain. The first three strongest projection regions were the ipsilateral lateral hypothalamus, zone incerta, and contralateral pontine reticular nucleus. Immunohistochemistry imaging showed that the input neurons in the dorsal raphe, laterodorsal tegmentum, and dorsal part of zone incerta were colocalized with serotoninergic, cholinergic, and neuronal nitric oxide synthetase-expressing neurons, respectively. However, in the lateral hypothalamus, a few input neurons innervating RMTg GABAergic neurons colocalized orexinergic neurons but lacked colocalization of melanin-concentrating hormone neurons. Our findings provide anatomical evidence to understand how RMTg GABAergic neurons integrate diverse information to exert varied functions.

1389-P: Asprosin-Neutralizing Antibodies as a Treatment for Binge Eating

The central nervous system (CNS) circuits that regulate binge eating remain to be identified, and effective treatments for binge eating are limited. Here, we provide evidence to support the vital role of asprosin, a novel fasting-induced glucogenic and orexigenic hormone, in the development of binge eating. We found that heterozygous deletion of fibrillin 1, the gene encoding asprosin protein, led to a 50% decrease in asprosin production and reduced binge-like eating behavior in mice. Consistently, systemic treatment of asprosin promoted, while an asprosin-neutralizing antibody inhibited, binge-like eating behavior. These behavioral changes were associated with increased or decreased activity of gamma-aminobutyric acid (GABA) producing neurons in the zona incerta (ZI) brain region, respectively. Mechanistically, we further demonstrate that asprosin stimulates ZI GABA neurons by decreasing small-conductance, calcium-activated potassium (SK) currents. Conversely, the asprosin-neutralizing antibody inhibits ZI GABA neurons by increasing SK currents. Our results support a model that asprosin decreases SK currents to stimulate ZI GABA neurons, further promoting binge-like eating behavior and causing obesity in mice. Our findings also provided preclinical evidence that asprosin-neutralizing antibodies could be used to treat binge eating. Keywords: Asprosin, neutralizing antibody, binge eating, obesity, GABA neurons Disclosure P. Xu: None. Y. He: None. Funding National Institutes of Health (P30 DK072476)

0126 Zona incerta Lhx6 neurons are most active during NREM and REM sleep and after prolonged waking

Abstract Introduction Emerging data shows that GABA neurons in the zona incerta (ZI) play a prominent role in regulating sleep. Transfer of the orexin gene into ZI neurons blocks cataplexy in narcoleptic orexin-knockout mice (Liu et al., JNeurosci, 2011) and vGAT GABA neurons in the ZI anticipate onset of NREM (Blanco-Centurion et al., SLEEP, 2021). To identify the subtype of GABA neurons regulating sleep, we examined the activity of Lhx6 neurons. This study tests the hypothesis that Lhx6 neurons show peak calcium fluorescence during sleep, and that the fluorescence is further increased after prolonged waking. Methods In Lhx6-cre mice (mice=4; all females; 4-5 mo), rAAV-DIO-GCaMP6s was delivered stereotaxically to the ZI (isofluorane anesthesia) and a GRIN lens, along with EEG and EMG electrodes were implanted. 21d later a miniscope (INSCOPIX) was attached, and after 3d of adaptation, sleep and fluorescence in individual Lhx6 neurons were recorded for 4h (baseline). On another day, the mice were kept awake for 6h (gentle handling; 9a-3p) and fluorescence in Lhx6 neurons was recorded for 2h during recovery sleep. The imaged data from the two recording periods (baseline and recovery sleep) was combined into a single data file and the change in fluorescence was determined against the mean image frame (F0). Previously, we and others found that the GCamP calcium fluorescence is a direct measure of action potentials and serves as a marker of activity. Results 97 neurons were automatically extracted (PCA-ICA analysis; blinded without knowledge of sleep state). In 66 neurons (68%) the average fluorescence was significantly higher during REM, NREM or both, compared to waking (Mixed Model ANOVA; SPSS25; P<0.01). In this population the fluorescence was significantly higher during recovery sleep compared to baseline (P<0.001) indicating increased activity of the sleep-active neurons during recovery sleep. With ensuing sleep, the increase in fluorescence gradually returned to baseline levels, attesting to the fluorescence as a marker of homeostatic sleep pressure. In 14 neurons (14%), fluorescence was highest in waking as compared to the other states during baseline, and in these neurons, fluorescence did not increase after sleep loss. Interestingly, six neurons (6%) were most active in waking and NREM but silent in REM (REM-off). Conclusion This is the first study to measure fluorescence in individual neurons after sleep loss. We find that the fluorescence in two-thirds of ZI Lhx6 neurons is tightly linked to sleep, and that the average fluorescence is further increased after prolonged waking. Microendoscopy is superior to indirect measures such as c-FOS or photometry in gauging sleep pressure in individual neurons. Support (If Any) VA BX000798, 1K6BX004216.

Whole-brain mapping of efferent projections of the anterior cingulate cortex in adult male mice.

The anterior cingulate cortex (ACC) is a key cortical region that plays an important role in pain perception and emotional functions. Previous studies of the ACC projections have been collected primarily from monkeys, rabbits and rats. Due to technological advances, such as gene manipulation, recent progress has been made in our understanding of the molecular and cellular mechanisms of the ACC-related chronic pain and emotion is mainly obtained from adult mice. Few anatomic studies have examined the whole-brain projections of the ACC in adult mice. In the present study, we examined the continuous axonal outputs of the ACC in the whole brain of adult male mice. We used the virus anterograde tracing technique and an ultrahigh-speed imaging method of Volumetric Imaging with Synchronized on-the-fly-scan and Readout (VISoR). We created a three-dimensional (3D) reconstruction of mouse brains. We found that the ACC projected ipsilaterally primarily to the caudate putamen (CPu), ventral thalamic nucleus, zona incerta (ZI), periaqueductal gray (PAG), superior colliculus (SC), interpolar spinal trigeminal nucleus (Sp5I), and dorsal medullary reticular nucleus (MdD). The ACC also projected to contralateral brain regions, including the ACC, reuniens thalamic nucleus (Re), PAG, Sp5I, and MdD. Our results provide a whole-brain mapping of efferent projections from the ACC in adult male mice, and these findings are critical for future studies of the molecular and synaptic mechanisms of the ACC and its related network in mouse models of brain diseases.

Novel targets in deep brain stimulation for movement disorders.

The neurosurgical treatment of movement disorders, primarily via deep brain stimulation (DBS), is a rapidly expanding and evolving field. Although conventional targets including the subthalamic nucleus (STN) and internal segment of the globus pallidus (GPi) for Parkinson's disease and ventral intermediate nucleus of the thalams (VIM) for tremor provide substantial benefit in terms of both motor symptoms and quality of life, other targets for DBS have been explored in an effort to maximize clinical benefit and also avoid undesired adverse effects associated with stimulation. These novel targets primarily include the rostral zona incerta (rZI), caudal zona incerta (cZI)/posterior subthalamic area (PSA), prelemniscal radiation (Raprl), pedunculopontine nucleus (PPN), substantia nigra pars reticulata (SNr), centromedian/parafascicular (CM/PF) nucleus of the thalamus, nucleus basalis of Meynert (NBM), dentato-rubro-thalamic tract (DRTT), dentate nucleus of the cerebellum, external segment of the globus pallidus (GPe), and ventral oralis (VO) complex of the thalamus. However, reports of outcomes utilizing these targets are scattered and disparate. In order to provide a comprehensive resource for researchers and clinicians alike, we have summarized the existing literature surrounding these novel targets, including rationale for their use, neurosurgical techniques where relevant, outcomes and adverse effects of stimulation, and future directions for research.

Zona Incerta Modulates Pain-Associated Behaviors in Mice

Pain is an unpleasant experience with both sensory and affective components. However, the neural circuits underlying modulation of pain-related behaviors remains unclear. In this study, we identified an inhibitory neural circuit that originates in central amygdala protein kinase C-delta (CeA-PKCδ) neurons and terminates in the ventral sector of the zona incerta (ZI), a subthalamic structure previously linked to pain processing. Behavioral experiments show that chemogenetic inhibition of GABAergic ZI neurons induces bilateral hypersensitivity in uninjured mice as well as contralateral hypersensitivity after nerve injury. In contrast, chemogenetic activation of VGAT cells in the ZI reverses nerve injury-induced hypersensitivity. Furthermore, we found that chemogenetic activation of ZI-VGAT neurons reduced pain-related aversion during formalin conditioned place aversion (FCPA) without affecting spontaneous nociceptive responses induced by formalin. Taken together, our results suggest an indispensable role of ZI in regulating somatosensory and affective components of pain. Grant support from NCCIH.

Somatotopic Organization of Hyperdirect Pathway Projections From the Primary Motor Cortex in the Human Brain.

BackgroundThe subthalamic nucleus (STN) is an effective neurosurgical target to improve motor symptoms in Parkinson's Disease (PD) patients. MR-guided Focused Ultrasound (MRgFUS) subthalamotomy is being explored as a therapeutic alternative to Deep Brain Stimulation (DBS) of the STN. The hyperdirect pathway provides a direct connection between the cortex and the STN and is likely to play a key role in the therapeutic effects of MRgFUS intervention in PD patients.ObjectiveThis study aims to investigate the topography and somatotopy of hyperdirect pathway projections from the primary motor cortex (M1).MethodsWe used advanced multi-fiber tractography and high-resolution diffusion MRI data acquired on five subjects of the Human Connectome Project (HCP) to reconstruct hyperdirect pathway projections from M1. Two neuroanatomy experts reviewed the anatomical accuracy of the tracts. We extracted the fascicles arising from the trunk, arm, hand, face and tongue area from the reconstructed pathways. We assessed the variability among subjects based on the fractional anisotropy (FA) and mean diffusivity (MD) of the fibers. We evaluated the spatial arrangement of the different fascicles using the Dice Similarity Coefficient (DSC) of spatial overlap and the centroids of the bundles.ResultsWe successfully reconstructed hyperdirect pathway projections from M1 in all five subjects. The tracts were in agreement with the expected anatomy. We identified hyperdirect pathway fascicles projecting from the trunk, arm, hand, face and tongue area in all subjects. Tract-derived measurements showed low variability among subjects, and similar distributions of FA and MD values among the fascicles projecting from different M1 areas. We found an anterolateral somatotopic arrangement of the fascicles in the corona radiata, and an average overlap of 0.63 in the internal capsule and 0.65 in the zona incerta.ConclusionMulti-fiber tractography combined with high-resolution diffusion MRI data enables the identification of the somatotopic organization of the hyperdirect pathway. Our preliminary results suggest that the subdivisions of the hyperdirect pathway projecting from the trunk, arm, hand, face, and tongue motor area are intermixed at the level of the zona incerta and posterior limb of the internal capsule, with a predominantly overlapping topographical organization in both regions. Subject-specific knowledge of the hyperdirect pathway somatotopy could help optimize target definition in MRgFUS intervention.

Case series investigating the differences between stimulation of rostral zona incerta region in isolation or in conjunction with the subthalamic nucleus on acute clinical effects for Parkinson’s disease

BackgroundSubthalamic nucleus (STN) deep brain stimulation (DBS) is a highly effective therapy for movement disorders including Parkinson’s disease (PD). One focus of research has been to explore whether stimulation of the rostral zona incerta (rZI) region contributes to the efficacy observed in STN DBS therapy. ObjectiveIn this study, we conducted a case series to evaluate the clinical efficacy and adverse effects of stimulation to the rZI region in isolation and in conjunction with STN stimulation. MethodsVolunteers with PD (N = 5), treated with STN DBS, and determined to have a dorsal contact within the region of rZI were recruited to participate. Following evaluation of tolerability, each volunteer underwent routine motor assessments during three stimulation parameter conditions: STN, rZI, and co-stimulation STN + rZI. Both participant and clinical examiner were blinded to the condition. Efficacy was measured with the Movement Disorders Society Unified Parkinson’s Disease Rating Scale (MDS-UPDRS) and the Unified Dyskinesia Rating Scale (UDysRS). Volumes of tissue activation for all conditions were assessed for STN and rZI coverage. ResultsNo significant differences between measures of MDS-UPDRS and UDysRS were observed for the three stimulation settings. Although not statistically significant, results showed that 2 participants preferred STN + rZI co– stimulation, 2 participants preferred STN stimulation, and 1 participant preferred rZI stimulation and 4/5 participant preferences were consistent with clinician preference. ConclusionsFindings from this case series support further investigation into co-stimulation of the rZI region and STN for PD motor symptoms.

Edinger-Westphal peptidergic neurons enable maternal preparatory nesting.

SummaryOptimizing reproductive fitness in mammalians requires behavioral adaptations during pregnancy. Maternal preparatory nesting is an essential behavior for the survival of the upcoming litter. Brain-wide immediate early gene mapping in mice evoked by nesting sequences revealed that phases of nest construction strongly activate peptidergic neurons of the Edinger-Westphal nucleus in pregnant mice. Genetic ablation, bidirectional neuromodulation, and in vitro and in vivo activity recordings demonstrated that these neurons are essential to modulate arousal before sleep to promote nesting specifically. We show that these neurons enable the behavioral effects of progesterone on preparatory nesting by modulating a broad network of downstream targets. Our study deciphers the role of midbrain CART+ neurons in behavioral adaptations during pregnancy vital for reproductive fitness.

Commentary: Combined Unilateral Radiofrequency Lesioning of the Motor Thalamus, Field of Forel, and Zona Incerta: A Series of Cases With Dystonia.

Commentary: Combined Unilateral Radiofrequency Lesioning of the Motor Thalamus, Field of Forel, and Zona Incerta: A Series of Cases With Dystonia.

Parvalbumin Neurons in Zona Incerta Regulate Itch in Mice.

Pain and itch are intricately entangled at both circuitry and behavioral levels. Emerging evidence indicates that parvalbumin (PV)-expressing neurons in zona incerta (ZI) are critical for promoting nocifensive behaviors. However, the role of these neurons in itch modulation remains elusive. Herein, by combining FOS immunostaining, fiber photometry, and chemogenetic manipulation, we reveal that ZI PV neurons act as an endogenous negative diencephalic modulator for itch processing. Morphological data showed that both histamine and chloroquine stimuli induced FOS expression in ZI PV neurons. The activation of these neurons was further supported by the increased calcium signal upon scratching behavior evoked by acute itch. Behavioral data further indicated that chemogenetic activation of these neurons reduced scratching behaviors related to histaminergic and non-histaminergic acute itch. Similar neural activity and modulatory role of ZI PV neurons were seen in mice with chronic itch induced by atopic dermatitis. Together, our study provides direct evidence for the role of ZI PV neurons in regulating itch, and identifies a potential target for the remedy of chronic itch.

Current-dependent ocular tilt reaction in deep brain stimulation of the subthalamic nucleus: Evidence for an incerto-interstitial pathway?

The aim was to characterize a combined vestibular, ocular motor and postural syndrome induced by deep brain stimulation (DBS) of the subthalamic nucleus in a patient with Parkinson's disease. In a systematic DBS programming session, eye, head and trunk position in roll and pitch plane were documented as a function of stimulation amplitude and field direction. Repeat ocular coherence tomography was used to estimate ocular torsion. The interstitial nucleus of Cajal (INC), zona incerta (ZI) and ascending vestibular fibre tracts were segmented on magnetic resonance imaging using both individual and normative structural connectomic data. Thresholded symptom-associated volumes of tissue activated (VTA) were calculated based on documented stimulation parameters. Ipsilateral ocular tilt reaction and body lateropulsion as well as contralateral torsional nystagmus were elicited by the right electrode in a current-dependent manner and subsided after DBS deactivation. With increasing currents, binocular tonic upgaze and body retropulsion were observed. Symptoms were consistent with an irritative effect on the INC. Symptom-associated VTA was found to overlap with the dorsal ZI and the ipsilateral vestibulothalamic tract, while lying rather distant to the INC proper. A ZI-to-INC 'incerto-interstitial' tract with contact to the medial-uppermost portion of the VTA could be traced. Unilateral stimulation of INC-related circuitry induces an ipsilateral vestibular, ocular motor and postural roll-plane syndrome, which converts into a pitch-plane syndrome when functional activation expands bilaterally. In this case, tractography points to an incerto-interstitial pathway, a tract previously only characterized in non-human primates. Directional current steering proved useful in managing this rare side effect.

Deep Brain Stimulation of Caudal Zona Incerta for Parkinson's Disease: One-Year Follow-Up and Electric Field Simulations

ObjectiveTo evaluate the effects of bilateral caudal zona incerta (cZi) deep brain stimulation (DBS) for Parkinson's disease (PD) one year after surgery and to create anatomical improvement maps based on patient-specific simulation of the electric field. Materials and MethodsWe report the one-year results of bilateral cZi-DBS in 15 patients with PD. Patients were evaluated on/off medication and stimulation using the Unified Parkinson's Disease Rating Scale (UPDRS). Main outcomes were changes in motor symptoms (UPDRS-III) and quality of life according to Parkinson's Disease Questionnaire-39 (PDQ-39). Secondary outcomes included efficacy profile according to sub-items of UPDRS-III and simulation of the electric field distribution around the DBS lead using the finite element method. Simulations from all patients were transformed to one common magnetic resonance imaging template space for the creation of improvement maps and anatomical evaluation. ResultsMedian UPDRS-III score off medication improved from 40 at baseline to 21 on stimulation at one-year follow-up (48%, p < 0.0005). PDQ-39 summary index did not change, but the subdomain activities of daily living (ADL) and stigma improved (25%, p < 0.03 and 75%, p < 0.01), whereas communication worsened (p < 0.03). For UPDRS-III sub-items, stimulation alone reduced median tremor score by 9 points, akinesia by 3, and rigidity by 2 points at one-year follow-up in comparison to baseline (90%, 25%, and 29%, respectively, p < 0.01). Visual analysis of the anatomical improvement maps based on simulated electrical fields showed no evident relation with the degree of symptom improvement and neither did statistical analysis show any significant correlation. ConclusionsBilateral cZi-DBS alleviates motor symptoms, especially tremor, and improves ADL and stigma in PD patients one year after surgery. Improvement maps may be a useful tool for visualizing the spread of the electric field. However, there was no clear-cut relation between anatomical location of the electric field and the degree of symptom relief.

Combined Unilateral Radiofrequency Lesioning of the Motor Thalamus, Field of Forel, and Zona Incerta: A Series of Cases With Dystonia.

Dystonia is a group of disorders characterized by involuntary slow repetitive twisting movements and/or abnormal posture. Surgical options such as neuromodulation through deep brain stimulation and neuroablative procedures are available for patients who do not respond to conservative treatment. To present our series of patients with dystonia who were treated with stereotactic combined unilateral radiofrequency lesioning of the motor thalamus, field of Forel, and zona incerta. Medical records of 50 patients with dystonia who were treated with unilateral combined lesions were reviewed. Outcomes of the surgical procedure were evaluated using the Burke-Fahn-Marsden Dystonia Rating Scale (with movement and disability subscales) and Unified Parkinson's Disease Rating Scale-tremor items. Based on the symptoms, patients were categorized as having generalized dystonia (34%), hemidystonia (30%), and dystonic tremor (DT) (36%). Primary/idiopathic dystonia, primary genetic/hereditary dystonia, and secondary dystonia accounted for 16%, 4%, and 80% of patients, respectively. The mean follow-up duration was 156.2 ± 88.9 mo. The overall improvement in the Burke-Fahn-Marsden Dystonia Rating Scale scores (movement and disability, respectively) was 57.8% and 36.4% in generalized dystonia, 60.0% and 45.8% in hemidystonia, and 65.6% and 56.8% in DT. Patients with DT showed an 83.3% improvement in mean Unified Parkinson's Disease Rating Scale tremor score. Patients with cerebral palsy showed mean improvements of 66.7% in movement scores and 50.8% in disability scores. No mortality or major morbidity was observed postoperatively. Stereotactic radiofrequency unilateral combined thalamotomy, campotomy, and zona incerta lesions may be an effective surgical alternative for patients with dystonia, especially those with secondary dystonia resistant to deep brain stimulation.

SELENOT Deficiency in the Mouse Brain Impacts Catecholaminergic Neuron Density: An Immunohistochemical, in situ Hybridization and 3D Light-Sheet Imaging Study

Background: Selenoprotein T (SELENOT), a PACAP-regulated thioredoxin-like protein, plays a role in catecholamine secretion and protects dopaminergic neurons. However, the role of SELENOT in the establishment of the catecholaminergic (CA) neuronal system is not known yet. Methods: We analyzed by immunohistochemistry and RNAscope in situ hybridization the distribution of SELENOT and the expression of its mRNA, respectively. In addition, 3D imaging involving immunostaining in toto, clearing through the iDISCO+ method, acquisitions by light-sheet microscopy, and processing of 3D images was performed to map the CA neuronal system. A semi-automatic quantification of 3D images was carried out. Results: SELENOT protein and mRNA are widely distributed in the mouse brain, with important local variations. Three-dimensional mapping, through tyrosine hydroxylase (TH) labeling, and semi-automated quantification of CA neurons in brain-specific SELENOT knockout mice showed a significant decrease in the number of TH-positive neurons in the area postrema (AP-A2), the A11 cell group (A11), and the zona incerta (ZI-A13) of SELENOT-deficient females, and in the hypothalamus (Hyp-A12-A14-A15) of SELENOT-deficient females and males. Conclusion: These results showed that SELENOT is diffusely expressed in the mouse brain and that its deficiency impacts CA neuron distribution in different brain areas including Hyp-A12-A14-A15, in both male and female mice.

Case report of holmes tremor and brief literature review

Introduction: Holmes Tremor is a slow frequency tremor, with an irregular presentation of rest and intention tremor, with postural component not obligatory. The Holmes tremor physiopathology, although not completely elucidated, can be explained by lesions in both basal ganglia-thalamo-cortical loop and cerebellum-thalamo cortical loop, and can be treated with a conservative approach– pharmacological treatment – or with surgery. It is reported a case that a surgery was elected as treatment, that resulted in a stimulation of the Ventralis Intermedius (Vim) and Zona Incerta (ZI). Case Presentation: Female patient, 41 years old, with Holmes Tremor involving both upper limbs, more predominant on the right side, and affecting more the proximal than the distal region of the limb. The tremor was both of rest and action, exacerbated by movement, anxiety, and stress. Due to functional impairment and failure of conservative neurological treatment with pharmacotherapy, a neurosurgical procedure was requested for implantation of two electrodes, targeting the Vim and ZI, on the left side for tremor control. Conclusion: Holmes Tremor is a complex syndrome and has its pathophysiology not so well elucidated. The case report describes an implantation of an electrode that had positive outcomes for the patient.

Electrophysiological confrontation of Lead-DBS-based electrode localizations in patients with Parkinson’s disease undergoing deep brain stimulation

Microelectrode recordings (MERs) are often used during deep brain stimulation (DBS) surgeries to confirm the position of electrodes in patients with advanced Parkinson’s disease.The present study focused on 32 patients who had undergone DBS surgery for advanced Parkinson’s disease. The first objective was to confront the anatomical locations of intraoperative individual MERs as determined electrophysiologically with those determined postoperatively by image reconstructions. The second aim was to search for differences in cell characteristics among the three subthalamic nucleus (STN) subdivisions and between the STN and other identified subcortical structures.Using the DISTAL atlas implemented in the Lead-DBS image reconstruction toolbox, each MER location was determined postoperatively and attributed to specific anatomical structures (sensorimotor, associative or limbic STN; substantia nigra [SN], thalamus, nucleus reticularis polaris, zona incerta [ZI]). The STN dorsal borders determined intraoperatively from electrophysiology were then compared with the STN dorsal borders determined by the reconstructed images. Parameters of spike clusters (firing rates, amplitudes – with minimum amplitude of 60 μV -, spike durations, amplitude spectral density of β-oscillations) were compared between structures (ANOVAs on ranks).Two hundred and thirty one MERs were analyzed (144 in 34 STNs, 7 in 4 thalami, 5 in 4 ZIs, 34 in 10 SNs, 41 others). The average difference in depth of the electrophysiological dorsal STN entry in comparison with the STN entry obtained with Lead-DBS was found to be of 0.1 mm (standard deviation: 0.8 mm). All 12 analyzed MERs recorded above the electrophysiologically-determined STN entry were confirmed to be in the thalamus or zona incerta. All MERs electrophysiologically attributed to the SN were confirmed to belong to this nucleus. However, 6/34 MERs that were electrophysiologically attributed to the ventral STN were postoperatively reattributed to the SN. Furthermore, 44 MERs of 3 trajectories, which were intraoperatively attributed to the STN, were postoperatively reattributed to the pallidum or thalamus.MER parameters seemed to differ across the STN, with higher spike amplitudes (H = 10.64, p < 0.01) and less prevalent β-oscillations (H = 9.81, p < 0.01) in the limbic STN than in the sensorimotor and associative subdivisions. Some cells, especially in the SN, showed longer spikes with lower firing rates, in agreement with described characteristics of dopamine cells. However, these probabilistic electrophysiological signatures might become clinically less relevant with the development of image reconstruction tools, which deserve to be applied intraoperatively.

Neural correlates of multidimensional motor outputs in an excitatory parafascicular-zona incerta circuit

The parafascicular nucleus (Pf) in medial thalamus is interconnected with prefrontal cortex and basal ganglia. Though much research has determined its importance in cognitive regulation of behaviour, its projections to regions in subthalamus remain less known. Such connections include those to zona incerta (ZI), located immediately dorsal to subthalamic nuclei (STN) regulating motor output, and whose role in a motor context is only beginning to be investigated. We thus examined circuits from parafascicular (Pf) thalamus to ZI, and its activity during locomotion and spontaneous behaviours in mice. We found that a distinct group of CaMKIIα-positive excitatory parafascicular neurons, separated from VGLUT2-positive excitatory neurons, project widely into ZI, more than adjacent STN. Our results from fibre photometry and decoding with general linear model (GLM) indicate that PF-ZI pathways do not specifically correlate with amount of locomotion or movement velocity, but instead show more specified activity during relative directional changes of movements observed in turning, sniffing behaviours. These results hint at the PF-ZI pathway having a distinct role in directing action specificity and have implications for subcortical bases in dimensional control of behaviours.

A primate temporal cortex-zona incerta pathway for novelty seeking.

Primates interact with the world by exploring visual objects; they seek opportunities to view novel objects even when these have no extrinsic reward value. How the brain controls this novelty seeking is unknown. Here we show that novelty seeking in monkeys is regulated by the zona incerta (ZI). As monkeys made eye movements to familiar objects to trigger an opportunity to view novel objects, many ZI neurons were preferentially activated by predictions of novel objects before the gaze shift. Low-intensity ZI stimulation facilitated gaze shifts, whereas ZI inactivation reduced novelty seeking. ZI-dependent novelty seeking was not regulated by neurons in the lateral habenula or by many dopamine neurons in the substantia nigra, traditionally associated with reward seeking. But the anterior ventral medial temporal cortex, an area important for object vision and memory, was a prominent source of novelty predictions. These data uncover a functional pathway in the primate brain that regulates novelty seeking.

Cellular and serotonergic correlates of habituated neuroendocrine responses in male and female rats.

Male and females appear equally capable of showing habituated hypothalamic-pituitary-adrenal (HPA) axis output responses to repeated exposures of the same challenge. Whether this reflects, within males and females, common mechanisms of decreased neuronal activity within stress responding, afferents to the paraventricular hypothalamic nucleus (PVH), the final common pathway to the HPA axis, has not been examined. Here we compared in adult male and female rats the extent to which declines in HPA axis responses to repeated restraint are met by habituated cellular (Fos) responses, in addition to changes in serotonin (5-hydroxytryptamine; 5-HT) expression and signaling, which normally stimulates the HPA axis. Thus, alterations in this component of HPA axis drive could provide an underlying basis for sex differences in adaptive responses. Males and females showed reliable declines in ACTH and corticosterone responses after 10 daily episodes of repeated restraint, recapitulated, in largest part, by similar regional patterns of Fos habituation, including within the PVH, several stress sensitive cell groups of the limbic forebrain, as well as within the raphe nucleus. Serotonin staining in the dorsal raphe and terminal profiles in the forebrain continued to reflect a higher pre-synaptic capacity for the 5-HT system in females. The sexual dimorphism encountered within the lateral septum and medial preoptic area of control animals was less distinguished in the repeat condition, however, whereas 5-HT varicosities in the PVH increased after repeated restraint only in females. Relative to their singly restrained counterparts, males displayed an increase in 5-HT 1 A receptor expression in the raphe nucleus after repeated restraint, whereas females showed a decrease in 5-HT 1 A mRNA levels in the hippocampus and in the zona incerta, representing the most proximal of cell groups expressing the 5-HT 1 A receptor in the vicinity of the PVH. In conclusion, similar regional profiles of cellular habituation in males and females suggest common CNS substrates of neuroendocrine adaptation. However, this process may be met by underlying sex differences in serotonergic control, given the respective roles for pre- and postsynaptic 5-HT 1 A receptors in mediating serotonin availability and signal transfer.