Learning and memory functions of the Basal Ganglia

Impairment of visually guided associative learning in children with Tourette syndrome

The major symptoms of Tourette syndrome are motor and vocal tics, but Tourette syndrome is occasionally associated with cognitive alterations as well. Although Tourette syndrome does not affect the majority of cognitive functions, some of them improve. There is scarce evidence on the impairment of learning functions in patients with Tourette syndrome. The core symptoms of Tourette syndrome are related to dysfunction of the basal ganglia and the frontostriatal loops. Acquired equivalence learning is a kind of associative learning that is related to the basal ganglia and the hippocampi. The modified Rutgers Acquired Equivalence Test was used in the present study to observe the associative learning function of patients with Tourette syndrome. The cognitive learning task can be divided into two main phases: the acquisition and test phases. The latter is further divided into two parts: retrieval and generalization. The acquisition phase of the associative learning test, which mainly depends on the function of the basal ganglia, was affected in the entire patient group, which included patients with Tourette syndrome with attention deficit hyperactivity disorder, obsessive compulsive disorder, autism spectrum disorder, or no comorbidities. Patients with Tourette syndrome performed worse in building associations. However, the retrieval and generalization parts of the test phase, which primarily depend on the function of the hippocampus, were not worsened by Tourette syndrome.

Procedural and declarative memory brain systems in developmental language disorder (DLD)

The aim of the current study was to examine microstructural differences in white matter relevant to procedural and declarative memory between adolescents/young adults with and without Developmental Language Disorder (DLD) using diffusion tensor imaging (DTI). The findings showed atypical age-related changes in white matter structures in the corticostriatal system, in the corticocerebellar system, and in the medial temporal region in individuals with DLD. Results highlight the importance of considering the age factor in research on DLD. Future studies are needed to examine the developmental relationship between long-term memory and individual differences in language development and learning.

Neuronal Replacement as a Tool for Basal Ganglia Circuitry Repair: 40 Years in Perspective

The ability of new neurons to promote repair of brain circuitry depends on their capacity to re-establish afferent and efferent connections with the host. In this review article, we give an overview of past and current efforts to restore damaged connectivity in the adult mammalian brain using implants of fetal neuroblasts or stem cell-derived neuronal precursors, with a focus on strategies aimed to repair damaged basal ganglia circuitry induced by lesions that mimic the pathology seen in humans affected by Parkinson’s or Huntington’s disease. Early work performed in rodents showed that neuroblasts obtained from striatal primordia or fetal ventral mesencephalon can become anatomically and functionally integrated into lesioned striatal and nigral circuitry, establish afferent and efferent connections with the lesioned host, and reverse the lesion-induced behavioral impairments. Recent progress in the generation of striatal and nigral progenitors from pluripotent stem cells have provided compelling evidence that they can survive and mature in the lesioned brain and re-establish afferent and efferent axonal connectivity with a remarkable degree of specificity. The studies of cell-based circuitry repair are now entering a new phase. The introduction of genetic and virus-based techniques for brain connectomics has opened entirely new possibilities for studies of graft-host integration and connectivity, and the access to more refined experimental techniques, such as chemo- and optogenetics, has provided new powerful tools to study the capacity of grafted neurons to impact the function of the host brain. Progress in this field will help to guide the efforts to develop therapeutic strategies for cell-based repair in Huntington’s and Parkinson’s disease and other neurodegenerative conditions involving damage to basal ganglia circuitry.

The Modulation of Pain by Metabotropic Glutamate Receptors 7 and 8 in the Dorsal Striatum

The dorsal striatum, apart from controlling voluntary movement, displays a recently demonstrated pain inhibition. It is connected to the descending pain modulatory system and in particular to the rostral ventromedial medulla through the medullary dorsal reticular nucleus. Diseases of the basal ganglia, such as Parkinson's disease, in addition to being characterized by motor disorders, are associated with pain and hyperactivation of the excitatory transmission. A way to counteract glutamatergic hyperactivation is through the activation of group III metabotropic glutamate receptors (mGluRs), which are located on presynaptic terminals inhibiting neurotransmitter release. So far the mGluRs of group III have been the least investigated, owing to a lack of selective tools. More recently, selective ligands for each mGluR of group III, in particular positive and negative allosteric modulators, have been developed and the role of each subtype is starting to emerge. The neuroprotective potential of group III mGluRs in pathological conditions, such as those characterized by elevate glutamate, has been recently shown. In the dorsal striatum, mGluR7 and mGluR8 are located at glutamatergic corticostriatal terminals and their stimulation inhibits pain in pathological conditions such as neuropathic pain. The two receptors in the dorsal striatum have instead a different role in pain control in normal conditions. This review will discuss recent results focusing on the contribution of mGluR7 and mGluR8 in the dorsal striatal control of pain. The role of mGluR4, whose antiparkinsonian activity is widely reported, will also be addressed.

Examining implicit procedural learning in tetraplegia using an oculomotor serial reaction time task

Background and objective

Clinical observations indicate that implicit procedural learning, a central component of physical and psychosocial rehabilitation, is impeded following spinal cord injury. In accordance, previous research has revealed a specific deficit in implicit sequence learning among individuals with paraplegia using a standard, manual version of the serial reaction time task. To extend these findings and shed light on the underlying sources of potential spinal cord injury-related deficits in sequence learning, we used an ocular activated serial reaction time task to compare sequence learning performance between individuals with tetraplegia and healthy controls.

Participants and measures

Twelve participants with spinal cord injury in C5-T1 were compared to 12 matched control participants on measures derived from an ocular activated serial reaction time task. Depression and additional cognitive measures were assessed to explore the source and specificity of potential sequence learning deficits.

Results

Like controls, and in contrast with previous findings in paraplegia, the spinal cord injury group showed intact implicit sequence learning, evidenced by declining reaction times and improved anticipation over the first six blocks of the serial reaction time task, and an advantage for the initial learning sequence over a novel interference sequence.

Conclusions

The ocular activated serial reaction time task elicited a performance pattern similar to standard motor versions, such that participants with tetraplegia demonstrated unimpaired sequence learning. This suggests that previously reported implicit sequence learning deficits in spinal cord injury directly involved motor functioning rather than cognitive aspects of the task, and that the ocular activated sequence learning task could be a valid alternative for assessing implicit sequence learning in populations that cannot perform spinal-cord dependent motor tasks. Implications for post-spinal cord injury rehabilitation and adjustment are discussed.

Early putamen hypertrophy and ongoing hippocampus atrophy predict cognitive performance in the first ten years of relapsing-remitting multiple sclerosis

BACKGROUND

The first years of relapsing-remitting multiple sclerosis (RRMS) constitute the most vulnerable phase for the progression of cognitive impairment (CImp), due to a gradual decrease of compensatory mechanisms. In the first 10 years of RRMS, the temporal volumetric changes of deep gray matter structures must be clarified, since they could constitute reliable cognitive biomarkers for diagnostic, prognostic, and therapeutic purposes.

METHODS

Forty-five cognitively asymptomatic patients with RRMS lasting ≤ 10 years, and with a brain MRI performed in a year from the neuropsychological evaluation (Te-MRI), were included. They performed the Brief International Cognitive Assessment battery for MS. Thirty-one brain MRIs performed in the year of diagnosis (Td-MRI) and 13 brain MRIs of age- and sex-matched healthy controls (HCs) were also included in the study. The relationships between clinical features, cognitive performances, and Te- and Td-MRI volumes were statistically analyzed.

RESULTS

Cognitively preserved (CP) patients had significantly increased Td-L-putamen (P = 0.035) and Td-R-putamen volume (P = 0.027) with respect to cognitively impaired (CI) ones. CI patients had significantly reduced Te-L-hippocampus (P = 0.019) and Te-R-hippocampus volume (P = 0.042) compared, respectively, with Td-L-hippocampus and Td-R-hippocampus volume. Td-L-putamen volume (P = 0.011) and Te-L-hippocampus volume (P = 0.023) were independent predictors of the Symbol Digit Modalities Test score in all patients (r2 = 0.31, F = 6.175, P = 0.001).

CONCLUSION

In the first years of RRMS, putamen hypertrophy and hippocampus atrophy could represent promising indices of cognitive performance and reserve, and become potentially useful tools for diagnostic, prognostic, and therapeutic purposes.

The Caudate Nucleus: Its Connections, Surgical Implications, and Related Complications

BACKGROUND

The caudate nucleus is a C-shaped structure that is located in the center of the brain and is divided into 3 parts: the head, body, and tail.

METHODS

We detail the anatomic connections, relationships with other basal ganglia structures, and clinical implications of injury to the caudate nucleus.

RESULTS

Anatomically, the most inferior transcapsular gray matter is the lentiform peduncle, which is the connection between the lentiform nucleus and caudate nucleus as well as the amygdala. The border between the tail and body of the caudate nucleus is the posterior insular point. The tail of the caudate nucleus is extraependymal in some parts and intraependymal in some parts of the roof of the temporal horn of the lateral ventricle. The tail of the caudate nucleus crosses the inferior limiting sulcus (temporal stem), and section of the tail during approaches to lesions involving the temporal stem may cause motor apraxia. The mean distance from the temporal limen point, which is the junction of the limen insula and inferior limiting sulcus, to the tail of the caudate nucleus in the temporal stem is 15.87 ± 3.10 mm.

CONCLUSIONS

Understanding of the functional anatomy and connections of the distinct parts of the caudate nucleus is essential for deciding the extent of resection of lesions involving the caudate nucleus and the types of deficits that may be found postoperatively.

Anti-instinctive Learning Behavior Revealed by Locomotion-Triggered Mild Heat Stress in Drosophila

Anti-instinctive learning, an ability to modify an animal's innate behaviors in ways that go against one's innate tendency, can confer great evolutionary advantages to animals and enable them to better adapt to the changing environment. Yet, our understanding of anti-instinctive learning and its underlying mechanisms is still limited. In this work, we describe a new anti-instinctive learning behavior of fruit flies. This learning paradigm requires the fruit fly to respond to a recurring, aversive, mild heat stress by modifying its innate locomotion behavior. We found that experiencing movement-triggered mild heat stress repeatedly significantly reduced walking activity in wild type fruit flies, indicating that fruit flies are capable of anti-instinctive learning. We also report that such learning ability is reduced in dopamine 1-like receptor 1 (Dop1R1) null mutant and dopamine 2-like receptor (Dop2R) null mutant flies, suggesting that these two dopamine receptors are involved in mediating anti-instinctive learning in flies.

Long-Term Physical Exercise and Mindfulness Practice in an Aging Population

Previous studies have shown that physical exercise and mindfulness meditation can both lead to improvement in physical and mental health. However, it is unclear whether these two forms of training share the same underlying mechanisms. We compared two groups of older adults with 10 years of mindfulness meditation (integrative body-mind training, IBMT) or physical exercise (PE) experience to demonstrate their effects on brain, physiology and behavior. Healthy older adults were randomly selected from a large community health project and the groups were compared on measures of quality of life, autonomic activity (heart rate, heart rate variability, skin conductance response, respiratory amplitude/rate), immune function (secretory Immunoglobulin A, sIgA), stress hormone (cortisol) and brain imaging (resting state functional connectivity, structural differences). In comparison with PE, we found significantly higher ratings for the IBMT group on dimensions of life quality. Parasympathetic activity indexed by skin conductance response and high-frequency heart rate variability also showed more favorable outcomes in the IBMT group. However, the PE group showed lower basal heart rate and greater chest respiratory amplitude. Basal sIgA level was significantly higher and cortisol concentration was lower in the IBMT group. Lastly, the IBMT group had stronger brain connectivity between the dorsal anterior cingulate cortex (dACC) and the striatum at resting state, as well as greater volume of gray matter in the striatum. Our results indicate that mindfulness meditation and physical exercise function in part by different mechanisms, with PE increasing physical fitness and IBMT inducing plasticity in the central nervous systems. These findings suggest combining physical and mental training may achieve better health and quality of life results for an aging population.

Brain Activity Associated With Attention Deficits Following Chemotherapy for Childhood Acute Lymphoblastic Leukemia

BACKGROUND

The impact of contemporary chemotherapy treatment for childhood acute lymphoblastic leukemia on central nervous system activity is not fully appreciated.

METHODS

Neurocognitive testing and functional magnetic resonance imaging (fMRI) were obtained in 165 survivors five or more years postdiagnosis (average age = 14.4 years, 7.7 years from diagnosis, 51.5% males). Chemotherapy exposure was measured as serum concentration of methotrexate following high-dose intravenous injection. Neurocognitive testing included measures of attention and executive function. fMRI was obtained during completion of two tasks, the continuous performance task (CPT) and the attention network task (ANT). Image analysis was performed using Statistical Parametric Mapping software, with contrasts targeting sustained attention, alerting, orienting, and conflict. All statistical tests were two-sided.

RESULTS

Compared with population norms, survivors demonstrated impairment on number-letter switching (P < .001, a measure of cognitive flexibility), which was associated with treatment intensity (P = .048). Task performance during fMRI was associated with neurocognitive dysfunction across multiple tasks. Regional brain activation was lower in survivors diagnosed at younger ages for the CPT (bilateral parietal and temporal lobes) and the ANT (left parietal and right hippocampus). With higher serum methotrexate exposure, CPT activation decreased in the right temporal and bilateral frontal and parietal lobes, but ANT alerting activation increased in the ventral frontal, insula, caudate, and anterior cingulate.

CONCLUSIONS

Brain activation during attention and executive function tasks was associated with serum methotrexate exposure and age at diagnosis. These findings provide evidence for compromised and compensatory changes in regional brain function that may help clarify the neural substrates of cognitive deficits in acute lymphoblastic leukemia survivors.

How Sequential Interactive Processing Within Frontostriatal Loops Supports a Continuum of Habitual to Controlled Processing

We address the distinction between habitual/automatic vs. goal-directed/controlled behavior, from the perspective of a computational model of the frontostriatal loops. The model exhibits a continuum of behavior between these poles, as a function of the interactive dynamics among different functionally-specialized brain areas, operating iteratively over multiple sequential steps, and having multiple nested loops of similar decision making circuits. This framework blurs the lines between these traditional distinctions in many ways. For example, although habitual actions have traditionally been considered purely automatic, the outer loop must first decide to allow such habitual actions to proceed. Furthermore, because the part of the brain that generates proposed action plans is common across habitual and controlled/goal-directed behavior, the key differences are instead in how many iterations of sequential decision-making are taken, and to what extent various forms of predictive (model-based) processes are engaged. At the core of every iterative step in our model, the basal ganglia provides a "model-free" dopamine-trained Go/NoGo evaluation of the entire distributed plan/goal/evaluation/prediction state. This evaluation serves as the fulcrum of serializing otherwise parallel neural processing. Goal-based inputs to the nominally model-free basal ganglia system are among several ways in which the popular model-based vs. model-free framework may not capture the most behaviorally and neurally relevant distinctions in this area.

The Raphe Dopamine System Controls the Expression of Incentive Memory

The brain dopamine (DA) system participates in forming and expressing memory. Despite a well-established role of DA neurons in the ventral tegmental area in memory formation, the exact DA circuits that control memory expression remain unclear. Here, we show that DA neurons in the dorsal raphe nucleus (DRN) and their medulla input control the expression of incentive memory. DRN DA neurons are activated by both rewarding and aversive stimuli in a learning-dependent manner and exhibit elevated activity during memory recall. Disrupting their physiological activity or DA synthesis blocks the expression of natural appetitive and aversive memories as well as drug memories associated with opioids. Moreover, a glutamatergic pathway from the lateral parabrachial nucleus to the DRN selectively regulates the expression of reward memories associated with opioids or foods. Our study reveals a specialized DA subsystem important for memory expression and suggests new targets for interventions against opioid addiction.

Testing Navigation in Real Space: Contributions to Understanding the Physiology and Pathology of Human Navigation Control

Successful navigation relies on the flexible and appropriate use of metric representations of space or topological knowledge of the environment. Spatial dimensions (2D vs. 3D), spatial scales (vista-scale vs. large-scale environments) and the abundance of visual landmarks critically affect navigation performance and behavior in healthy human subjects. Virtual reality (VR)-based navigation paradigms in stationary position have given insight into the major navigational strategies, namely egocentric (body-centered) and allocentric (world-centered), and the cerebral control of navigation. However, VR approaches are biased towards optic flow and visual landmark processing. This major limitation can be overcome to some extent by increasingly immersive and realistic VR set-ups (including large-screen projections, eye tracking and use of head-mounted camera systems). However, the highly immersive VR settings are difficult to apply particularly to older subjects and patients with neurological disorders because of cybersickness and difficulties with learning and conducting the tasks. Therefore, a need for the development of novel spatial tasks in real space exists, which allows a synchronous analysis of navigational behavior, strategy, visual explorations and navigation-induced brain activation patterns. This review summarizes recent findings from real space navigation studies in healthy subjects and patients with different cognitive and sensory neurological disorders. Advantages and limitations of real space navigation testing and different VR-based navigation paradigms are discussed in view of potential future applications in clinical neurology.

Explicit memory and cognition in monkeys

Taxonomies of human memory, influenced heavily by Endel Tulving, make a fundamental distinction between explicit and implicit memory. Humans are aware of explicit memories, whereas implicit memories control behavior even though we are not aware of them. Efforts to understand the evolution of memory, and to use nonhuman animals to model human memory, will be facilitated by better understanding the extent to which this critical distinction exists in nonhuman animals. Work with metacognition paradigms in the past 20 years has produced a strong case for the existence of explicit memory in nonhuman primates and possibly other nonhuman animals. Clear dissociations of explicit and implicit memory by metacognition have yet to be demonstrated in nonhumans, although dissociations between memory systems by other behavioral techniques, and by brain manipulations, suggest that the explicit-implicit distinction applies to nonhumans. Neurobehavioral studies of metamemory are beginning to identify neural substrates for memory monitoring in the frontal cortex of monkeys. We have strong evidence that at least some memory systems are explicit in rhesus monkeys, but we need to learn more about the distribution of explicit processes across cognitive systems within monkeys, and across species.

Basal ganglia role in learning rewarded actions and executing previously learned choices: Healthy and diseased states

The basal ganglia (BG) is a collection of nuclei located deep beneath the cerebral cortex that is involved in learning and selection of rewarded actions. Here, we analyzed BG mechanisms that enable these functions. We implemented a rate model of a BG-thalamo-cortical loop and simulated its performance in a standard action selection task. We have shown that potentiation of corticostriatal synapses enables learning of a rewarded option. However, these synapses became redundant later as direct connections between prefrontal and premotor cortices (PFC-PMC) were potentiated by Hebbian learning. After we switched the reward to the previously unrewarded option (reversal), the BG was again responsible for switching to the new option. Due to the potentiated direct cortical connections, the system was biased to the previously rewarded choice, and establishing the new choice required a greater number of trials. Guided by physiological research, we then modified our model to reproduce pathological states of mild Parkinson's and Huntington's diseases. We found that in the Parkinsonian state PMC activity levels become extremely variable, which is caused by oscillations arising in the BG-thalamo-cortical loop. The model reproduced severe impairment of learning and predicted that this is caused by these oscillations as well as a reduced reward prediction signal. In the Huntington state, the potentiation of the PFC-PMC connections produced better learning, but altered BG output disrupted expression of the rewarded choices. This resulted in random switching between rewarded and unrewarded choices resembling an exploratory phase that never ended. Along with other computational studies, our results further reconcile the apparent contradiction between the critical involvement of the BG in execution of previously learned actions and yet no impairment of these actions after BG output is ablated by lesions or deep brain stimulation. We predict that the cortico-BG-thalamo-cortical loop conforms to previously learned choice in healthy conditions, but impedes those choices in disease states.

Effects of huperzine A on hippocampal inflammatory response and neurotrophic factors in aged rats after anesthesia

PURPOSE

To investigate the effects of huperzine A (HupA) on hippocampal inflammatory response and neurotrophic factors in aged rats after anesthesia.

METHODS

Thirty-six Sprague Dawley rats (20-22 months old) were randomly divided into control, isofluran, and isoflurane+HupA groups; 12 rats in each group. The isoflurane+HupA group was intraperitoneally injected with 0.2 mg/kg of HupA. After 30 min, isoflurane inhalation anesthesia was performed in the isoflurane and isoflurane+HupA groups. After 24 h from anesthesia, Morris water maze experiment and open-field test were performed. Hippocampal inflammatory and neurotrophic factors were determined.

RESULTS

Compared with isoflurane group, in isofluran+HupA group the escape latency of rats was significantly decreased (P < 0.05), the original platform quadrant residence time and traversing times were significantly increased (P < 0.05), the central area residence time was significantly increased (P < 0.05), the hippocampal tumor necrosis factor α, interleukin 6 and interleukin 1β levels were significantly decreased (P < 0.05), and the hippocampal nerve growth factor, brain derived neurotrophic factor and neurotrophin-3 levels were significantly increased (P < 0.05).

CONCLUSION

HupA may alleviate the cognitive impairment in rats after isoflurane anesthesia by decreasing inflammatory factors and increasing hippocampal neurotrophic factors in hippocampus tissue.

CB1 Activity Drives the Selection of Navigational Strategies: A Behavioral and c-Fos Immunoreactivity Study

To promote efficient explorative behaviors, subjects adaptively select spatial navigational strategies based on landmarks or a cognitive map. The hippocampus works alone or in conjunction with the dorsal striatum, both representing the neuronal underpinnings of the navigational strategies organized on the basis of different systems of spatial coordinate integration. The high expression of cannabinoid type 1 (CB₁) receptors in structures related to spatial learning—such as the hippocampus, dorsal striatum and amygdala—renders the endocannabinoid system a critical target to study the balance between landmark- and cognitive map-based navigational strategies. In the present study, mice treated with the CB₁-inverse agonist/antagonist AM251 or vehicle were trained on a Circular Hole Board, a task that could be solved through either navigational strategy. At the end of the behavioral testing, c-Fos immunoreactivity was evaluated in specific nuclei of the hippocampus, dorsal striatum and amygdala. AM251 treatment impaired spatial learning and modified the pattern of the performed navigational strategies as well as the c-Fos immunoreactivity in the hippocampus, dorsal striatum and amygdala. The present findings shed light on the involvement of CB₁ receptors as part of the selection system of the navigational strategies implemented to efficiently solve the spatial problem.

Interfacing behavioral and neural circuit models for habit formation

Habits are an important mechanism by which organisms can automate the control of behavior to alleviate cognitive demand. However, transitions to habitual control are risky because they lead to inflexible responding in the face of change. The question of how the brain controls transitions into habit is thus an intriguing one. How do we regulate when our repeated actions become automated? When is it advantageous or disadvantageous to release actions from cognitive control? Decades of research have identified a variety of methods for eliciting habitual responding in animal models. Progress has also been made to understand which brain areas and neural circuits control transitions into habit. Here, I discuss existing research on behavioral and neural circuit models for habit formation (with an emphasis on striatal circuits), and discuss strategies for combining information from different paradigms and levels of analysis to prompt further progress in the field.

Lesion of striatal patches disrupts habitual behaviors and increases behavioral variability

Habits are automated behaviors that are insensitive to changes in behavioral outcomes. Habitual responding is thought to be mediated by the striatum, with medial striatum guiding goal-directed action and lateral striatum promoting habits. However, interspersed throughout the striatum are neurochemically differing subcompartments known as patches, which are characterized by distinct molecular profiles relative to the surrounding matrix tissue. These structures have been thoroughly characterized neurochemically and anatomically, but little is known regarding their function. Patches have been shown to be selectively activated during inflexible motor stereotypies elicited by stimulants, suggesting that patches may subserve habitual behaviors. To explore this possibility, we utilized transgenic mice (Sepw1 NP67) preferentially expressing Cre recombinase in striatal patch neurons to target these neurons for ablation with a virus driving Cre-dependent expression of caspase 3. Mice were then trained to press a lever for sucrose rewards on a variable interval schedule to elicit habitual responding. Mice were not impaired on the acquisition of this task, but lesioning striatal patches disrupted behavioral stability across training, and lesioned mice utilized a more goal-directed behavioral strategy during training. Similarly, when mice were forced to omit responses to receive sucrose rewards, habitual responding was impaired in lesioned mice. To rule out effects of lesion on motor behaviors, mice were then tested for impairments in motor learning on a rotarod and locomotion in an open field. We found that patch lesions partially impaired initial performance on the rotarod without modifying locomotor behaviors in open field. This work indicates that patches promote behavioral stability and habitual responding, adding to a growing literature implicating striatal patches in stimulus-response behaviors.

Real-space navigation testing differentiates between amyloid-positive and -negative aMCI

OBJECTIVE

To distinguish between patients with amyloid-positive (A+) and -negative (A-) amnestic mild cognitive impairment (aMCI) by simultaneously investigating navigation performance, visual exploration behavior, and brain activations during a real-space navigation paradigm.

METHODS

Twenty-one patients with aMCI were grouped into A+ (n = 11) and A- cases by amyloid-PET imaging and amyloid CSF levels and compared to 15 healthy controls. Neuropsychological deficits were quantified by use of the Consortium to Establish a Registry for Alzheimer's Disease-plus cognitive battery. All participants performed a navigation task in which they had to find items in a realistic spatial environment and had to apply egocentric and allocentric route planning strategies. ¹⁸F-fluorodeoxyglucose was injected at the start to detect navigation-induced brain activations. Subjects wore a gaze-controlled, head-fixed camera that recorded their visual exploration behavior.

RESULTS

A+ patients performed worse during egocentric and allocentric navigation compared to A- patients and controls (p < 0.001). Both aMCI subgroups used fewer shortcuts, moved more slowly, and stayed longer at crossings. Word-list learning, figural learning, and Trail-Making tests did not differ in the A+ and A- subgroups. A+ patients showed a reduced activation of the right hippocampus, retrosplenial, and parietal cortex during navigation compared to A- patients (p < 0.005).

CONCLUSIONS

A+ patients with aMCI perform worse than A- patients with aMCI in egocentric and allocentric route planning because of a more widespread impairment of their cerebral navigation network. Navigation testing in real space is a promising approach to identify patients with aMCI with underlying Alzheimer pathology.

Aberrant Thalamic-Centered Functional Connectivity in Patients with Persistent Somatoform Pain Disorder

PURPOSE

Recent task-based fMRI studies have shown that Persistent Somatoform Pain Disorder (PSPD) patients demonstrated aberrant activity in a wide range of brain regions associated with sensation, cognition and emotion. However, these specific task-based studies could not clearly uncover the alterations in the spontaneous brain networks that were associated with the general pain-related symptoms in PSPD.

PATIENTS AND METHODS

In the present study, 13 PSPD patients and 23 matched healthy controls (HCs) were enrolled. Resting state and 3D structural imaging data were collected during magnetic resonance imaging (MRI) scans. Ninety regions of interest (ROIs) were selected from the automated anatomical labeling (AAL) template. The functional connectivity toolbox "CONN" was used to calculate the functional connectivity (FC) coefficients.

RESULTS

Our results showed that PSPD patients exhibited increased FCs between the left thalamus and the right amygdala, the right hippocampus, and multiple sub-regions of the occipital lobe when compared to HCs. Correlation analysis revealed a negative correlation between the left thalamus-right amygdala FC and the level of anxiety in PSPD patients.

CONCLUSION

These findings suggest that the altered FC between thalamus and amygdala may be the neural mechanisms underlying the pain-related anxiety in PSPD.

Spatial Navigation

The hippocampus is critical for spatial navigation. In this review, we focus on the role of the hippocampus in three basic strategies used for spatial navigation: path integration, stimulus-response association, and map-based navigation. First, the hippocampus is not required for path integration unless the path of path integration is too long and complex. The hippocampus provides mnemonic support when involved in the process of path integration. Second, the hippocampus's involvement in stimulus-response association is dependent on how the strategy is conducted. The hippocampus is not required for the habit form of stimulus-response association. Third, while the hippocampus is fully engaged in map-based navigation, the shared characteristics of place cells, grid cells, head direction cells, and other spatial encoding cells, which are detected in the hippocampus and associated areas, offer a possibility that there is a stand-alone allocentric space perception (or mental representation) of the environment outside and independent of the hippocampus, and the spatially specific firing patterns of these spatial encoding cells are the unfolding of the intermediate stages of the processing of this allocentric spatial information when conveyed into the hippocampus for information storage or retrieval. Furthermore, the presence of all the spatially specific firing patterns in the hippocampus and the related neural circuits during the path integration and map-based navigation support such a notion that in essence, path integration is the same allocentric space perception provided with only idiothetic inputs. Taken together, the hippocampus plays a general mnemonic role in spatial navigation.

Maintained Visual-, Auditory-, and Multisensory-Guided Associative Learning Functions in Children With Obsessive-Compulsive Disorder

Sensory-guided acquired equivalence learning, a specific kind of non-verbal associative learning, is associated with the frontal cortex-basal ganglia loops and hippocampi, which seem to be involved in the pathogenesis of obsessive-compulsive disorder (OCD). In this study, we asked whether visual-, auditory-, and multisensory-guided associative acquired equivalence learning is affected in children with OCD. The first part of the applied learning paradigm investigated association building between two different sensory stimuli (where feedback was given about the correctness of the choices), a task that critically depends upon the basal ganglia. During the test phases, which primarily depended upon the hippocampi, the earlier learned and hitherto not shown but predictable associations were asked about without feedback. This study involved 31 children diagnosed with OCD according to the Diagnostic and Statistical Manual of Mental Disorders, 5th Edition (DSM-V) criteria and 31 matched healthy control participants. The children suffering from OCD had the same performance as the control children in all phases of the applied visual-, auditory-, and multisensory-guided associative learning paradigms. Thus, both the acquisition and test phases were not negatively affected by OCD. The reaction times did not differ between the two groups, and the applied medication had no effect on the performances of the OCD patients. Our results support the findings that the structural changes of basal ganglia and hippocampi detected in adult OCD patients are not as pronounced in children, which could be the explanation of the maintained associative equivalence learning functions in children suffering from OCD.

Striatum-Mediated Deficits in Stimulus-Response Learning and Decision-Making in OCD

Obsessive compulsive disorder (OCD) is a prevalent psychiatric disorder characterized by obsessions and compulsions. Studies investigating symptomatology and cognitive deficits in OCD frequently implicate the striatum. The aim of this study was to explore striatum-mediated cognitive deficits in patients with OCD as they complete a stimulus-response learning task previously shown to differentially rely on the dorsal (DS) and ventral striatum (VS). We hypothesized that patients with OCD will show both impaired decision-making and learning, coupled with reduced task-relevant activity in DS and VS, respectively, compared to healthy controls. We found that patients with OCD (n = 14) exhibited decision-making deficits and learned associations slower compared to healthy age-matched controls (n = 16). Along with these behavioral deficits, OCD patients had reduced task-relevant activity in DS and VS, compared to controls. This study reveals that responses in DS and VS are altered in OCD, and sheds light on the cognitive deficits and symptoms experienced by patients with OCD.

Developmental Changes of Glutamate and GABA Receptor Densities in Wistar Rats

Neurotransmitters and their receptors are key molecules of signal transduction and subject to various changes during pre- and postnatal development. Previous studies addressed ontogeny at the level of neurotransmitters and expression of neurotransmitter receptor subunits. However, developmental changes in receptor densities to this day are not well understood. Here, we analyzed developmental changes in excitatory glutamate and inhibitory γ-aminobutyric acid (GABA) receptors in adjacent sections of the rat brain by means of quantitative in vitro receptor autoradiography. Receptor densities of the ionotropic glutamatergic receptors α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA), kainate and N-methyl-D-aspartate (NMDA) as well as of the ionotropic GABA_A and metabotropic GABA_B receptors were investigated using specific high-affinity ligands. For each receptor binding site, significant density differences were demonstrated in the investigated regions of interest [olfactory bulb, striatum, hippocampus, and cerebellum] and developmental stages [postnatal day (P) 0, 10, 20, 30 and 90]. In particular, we showed that the glutamatergic and GABAergic receptor densities were already present between P0 and P10 in all regions of interest, which may indicate the early relevance of these receptors for brain development. A transient increase of glutamatergic receptor densities in the hippocampus was found, indicating their possible involvement in synaptic plasticity. We demonstrated a decline of NMDA receptor densities in the striatum and hippocampus from P30 to P90, which could be due to synapse elimination, a process that redefines neuronal networks in postnatal brains. Furthermore, the highest increase in GABA_A receptor densities from P10 to P20 coincides with the developmental shift from excitatory to inhibitory GABA transmission. Moreover, the increase from P10 to P20 in GABA_A receptor densities in the cerebellum corresponds to a point in time when functional GABAergic synapses are formed. Taken together, the present data reveal differential changes in glutamate and GABA receptor densities during postnatal rat brain development, which may contribute to their specific functions during ontogenesis, thus providing a deeper understanding of brain ontogenesis and receptor function.

Genomewide Gene-by-Sex Interaction Scans Identify ADGRV1 for Sex Differences in Opioid Dependent African Americans

Sex differences in opioid dependence (OD) are genetically influenced. We conducted genomewide gene-by-sex interaction scans for the DSM-IV diagnosis of OD in 8,387 African-American (AA) or European-American subjects (43.6% women; 4,715 OD subjects). Among AAs, 9 SNPs were genome-wide significant at ADGRV1 (adhesion G-protein-coupled receptor V1, lead-SNP rs2366929*(C/T), p = 1.5 × 10-9) for sex-different risk of OD, with the rs2366929*C-allele increasing OD risk only for men. The top co-expressions in brain were between ADGRV1 and GRIK2 in substantia nigra and medullary inferior olivary nucleus, and between ADGRV1 and EFHC2 in frontal cortex and putamen. Significant sex-differential ADGRV1 expression from GTEx was detected in breast (Bonferroni-corrected-p < 0.002) and in heart (p < 0.0125), with nominal significance identified in brain, thyroid, lung, and stomach (p < 0.05). ADGRV1 co-expression and disease-enrichment analysis identifying the top 10 diseases showed strikingly sexually dimorphic risks. The enrichment and transcriptome analyses provided convergent support that ADGRV1 exerts a sex-different effect on OD risk. This is the first study to identify genetic variants contributing to sex differences in OD. It shows that ADGRV1 contributes to OD risk only in AA men, a finding that warrants further study.

Properdin: A Novel Target for Neuroprotection in Neonatal Hypoxic-Ischemic Brain Injury

Background: Hypoxic-ischemic (HI) encephalopathy is a major cause of neonatal mortality and morbidity, with a global incidence of 3 per 1,000 live births. Intrauterine or perinatal complications, including maternal infection, constitute a major risk for the development of neonatal HI brain damage. During HI, inflammatory response and oxidative stress occur, causing subsequent cell death. The presence of an infection sensitizes the neonatal brain, making it more vulnerable to the HI damage. Currently, therapeutic hypothermia is the only clinically approved treatment available for HI encephalopathy, however it is only partially effective in HI alone and its application in infection-sensitized HI is debatable. Therefore, there is an unmet clinical need for the development of novel therapeutic interventions for the treatment of HI. Such an alternative is targeting the complement system. Properdin, which is involved in stabilization of the alternative pathway convertases, is the only known positive regulator of alternative complement activation. Absence of the classical pathway in the neonatal HI brain is neuroprotective. However, there is a paucity of data on the participation of the alternative pathway and in particular the role of properdin in HI brain damage.

Objectives: Our study aimed to validate the effect of global properdin deletion in two mouse models: HI alone and LPS-sensitized HI, thus addressing two different clinical scenarios.

Results: Our results indicate that global properdin deletion in a Rice-Vannucci model of neonatal HI and LPS-sensitized HI brain damage, in the short term, clearly reduced forebrain cell death and microglial activation, as well as tissue loss. In HI alone, deletion of properdin reduced TUNEL+ cell death and microglial post-HI response at 48 h post insult. Under the conditions of LPS-sensitized HI, properdin deletion diminished TUNEL+ cell death, tissue loss and microglial activation at 48 h post-HI.

Conclusion: Overall, our data suggests a critical role for properdin, and possibly also a contribution in neonatal HI alone and in infection-sensitized HI brain damage. Thus, properdin can be considered a novel target for treatment of neonatal HI brain damage.

Helios modulates the maturation of a CA1 neuronal subpopulation required for spatial memory formation

Currently, molecular, electrophysiological and structural studies delineate several neural subtypes in the hippocampus. However, the precise developmental mechanisms that lead to this diversity are still unknown. Here we show that alterations in a concrete hippocampal neuronal subpopulation during development specifically affect hippocampal-dependent spatial memory. We observed that the genetic deletion of the transcription factor Helios in mice, which is specifically expressed in developing hippocampal calbindin-positive CA1 pyramidal neurons (CB-CA1-PNs), induces adult alterations affecting spatial memory. In the same mice, CA3-CA1 synaptic plasticity and spine density and morphology in adult CB-CA1-PNs were severely compromised. RNAseq experiments in developing hippocampus identified an aberrant increase on the Visinin-like protein 1 (VSNL1) expression in the hippocampi devoid of Helios. This aberrant increase on VSNL1 levels was localized in the CB-CA1-PNs. Normalization of VSNL1 levels in CB-CA1-PNs devoid of Helios rescued their spine loss in vitro. Our study identifies a novel and specific developmental molecular pathway involved in the maturation and function of a CA1 pyramidal neuronal subtype.

Dopaminergic medication reduces striatal sensitivity to negative outcomes in Parkinson's disease

Reduced levels of dopamine in Parkinson's disease contribute to changes in learning, resulting from the loss of midbrain neurons that transmit a dopaminergic teaching signal to the striatum. Dopamine medication used by patients with Parkinson's disease has previously been linked to behavioural changes during learning as well as to adjustments in value-based decision-making after learning. To date, however, little is known about the specific relationship between dopaminergic medication-driven differences during learning and subsequent changes in approach/avoidance tendencies in individual patients. Twenty-four Parkinson's disease patients ON and OFF dopaminergic medication and 24 healthy controls subjects underwent functional MRI while performing a probabilistic reinforcement learning experiment. During learning, dopaminergic medication reduced an overemphasis on negative outcomes. Medication reduced negative (but not positive) outcome learning rates, while concurrent striatal blood oxygen level-dependent responses showed reduced prediction error sensitivity. Medication-induced shifts in negative learning rates were predictive of changes in approach/avoidance choice patterns after learning, and these changes were accompanied by systematic striatal blood oxygen level-dependent response alterations. These findings elucidate the role of dopamine-driven learning differences in Parkinson's disease, and show how these changes during learning impact subsequent value-based decision-making.

Neural and Behavioral Effects of an Adaptive Online Verbal Working Memory Training in Healthy Middle-Aged Adults

Neural correlates of working memory (WM) training remain a matter of debate, especially in older adults. We used functional magnetic resonance imaging (fMRI) together with an n-back task to measure brain plasticity in healthy middle-aged adults following an 8-week adaptive online verbal WM training. Participants performed 32 sessions of this training on their personal computers. In addition, we assessed direct effects of the training by applying a verbal WM task before and after the training. Participants (mean age 55.85 ± 4.24 years) were pseudo-randomly assigned to the experimental group (n = 30) or an active control group (n = 27). Training resulted in an activity decrease in regions known to be involved in verbal WM (i.e., fronto-parieto-cerebellar circuitry and subcortical regions), indicating that the brain became potentially more efficient after the training. These activation decreases were associated with a significant performance improvement in the n-back task inside the scanner reflecting considerable practice effects. In addition, there were training-associated direct effects in the additional, external verbal WM task (i.e., HAWIE-R digit span forward task), and indicating that the training generally improved performance in this cognitive domain. These results led us to conclude that even at advanced age cognitive training can improve WM capacity and increase neural efficiency in specific regions or networks.

Estradiol and selective estrogen receptor agonists differentially affect brain monoamines and amino acids levels in transitional and surgical menopausal rat models

Estrogens have many beneficial effects in the brain. Previously, we evaluated the effects of two models of menopause (surgical vs. transitional) on multiple monoaminergic endpoints in different regions of the adult rat brain in comparison with levels in gonadally intact rats. Here we evaluated the effects of estrogen receptor (ER) agonist treatments in these same two models of menopause. Neurochemical endpoints were evaluated in the hippocampus (HPC), frontal cortex (FCX), and striatum (STR) of adult ovariectomized (OVX) rats and in rats that underwent selective and gradual ovarian follicle depletion by daily injection of 4-vinylcyclohexene-diepoxide (VCD), after 1- and 6-weeks treatment with 17β-estradiol (E2), or with selective ERα (PPT), ERβ (DPN), or GPR30 (G-1) agonists. Endpoints included serotonin (5-HT) and 5-Hydroxyindoleacetic acid, dopamine (DA), 3,4-Dihydroxyphenylacetic acid and homovanillic acid, norepinephrine (NE) and epinephrine, as well as the amino acids tryptophan (TRP) and tyrosine (TYR). Significant differences between the models were detected. OVX rats were much more sensitive to ER agonist treatments than VCD-treated rats. Significant differences between brain regions also were detected. Within OVX rats, more agonist effects were detected in the HPC than in any other region. One interesting finding was the substantial decrease in TRP and TYR detected in the HPC and FCX in response to agonist treatments, particularly in OVX rats. This is on top of the substantial decreases in TRP and TYR previously reported one week after OVX or VCD-treatments in comparison with gonadally intact controls. Other interesting findings included increases in the levels of 5-HT, DA, and NE in the HPC of OVX rats treated with DPN, increases in DA detected in the FCX of OVX rats treated with any of the ER agonists, and increases in 5-HT and DA detected in the STR of OVX rats treated with E2. Many effects that were observed after 1-week of treatment were no longer observed after 6-weeks of treatment, demonstrating that effects were temporary despite continued agonist treatment. Collectively, the results demonstrate significant differences in the effects of ER agonists on monoaminergic endpoints in OVX vs. VCD-treated rats that also were brain region-specific and time dependent. The fact that agonist treatments had lesser effects in VCD treated rats than in OVX rats may help to explain reports of lesser effects of estrogen replacement on cognitive performance in women that have undergone transitional vs. surgical menopause.

Subcortical structural variations associated with low socioeconomic status in adolescents

Low socioeconomic status (SES) is associated with a higher probability of multiple exposures (e.g., neighborhood violence, poor nutrition, housing instability, air pollution, and insensitive caregiving) known to affect structural development of subcortical brain regions that subserve threat and reward processing, however, few studies have examined the relationship between SES and such subcortical structures in adolescents. We examined SES variations in volume and surface morphometry of subcortical regions. The sample comprised 256 youth in eighth grade (mean age = 13.9 years), in whom high dimensional deformation mapping of structural 3T magnetic resonance imaging scans was performed. Vertex‐wise linear regression analyses examined associations between income to poverty ratio and surfaces of the hippocampus, amygdala, thalamus, caudate, putamen, nucleus accumbens and pallidum, with the covariates age, pubertal status, and intracranial volume. Given sex differences in pubertal development and subcortical maturation at this age, the analyses were stratified by sex. Among males, who at this age average an earlier pubertal stage than females, the relationship between SES and local shape variation in subcortical regions was almost entirely positive. For females, the relationship between SES and local shape variation was negative. Racial identity was associated with SES in our sample, however supplementary analyses indicated that most of the associations between SES and subcortical structure were independent of it. Although these cross‐sectional results are not definitive, they are consistent with a scenario where low SES delays structural maturation of subcortical regions involved with threat and reward processing. Future longitudinal studies are needed to test this hypothesis.

Shaping consumption propensity through the emotional response evoked by nutritional labels: Evidence from an fMRI study

The study aims to investigate a) the ability of nutritional labels in pictorial and textual form to guide consumption choices applying the dual-coding theory; b) the effectiveness of a new type of pictorial label (i.e. the body label) that appeals to the self-congruence theory and to positive emotional response. The research hypotheses were tested trough a 2x4x2 fMRI experimental design with 2 levels of product version (regular vs light), 4 levels of label type (text vs traffic light vs star rating vs body) and 2 levels of group of people (normal weight vs overweight). The body light label generates more brain activation in areas involved in the reward circuit compared to the body regular one, and compared to all the other types of labels for both versions, only in the overweight subject group. Furthermore, the star rating label has the worst performance in orienting healthy food choices as it requires more cognitive effort. The results are of interest to policy maker's strategies and to out-of-store and in-store communication strategies with the aim to contract the excessive body-weight phenomenon.

Cellular and Synaptic Dysfunctions in Parkinson's Disease: Stepping out of the Striatum

The basal ganglia (BG) are a collection of interconnected subcortical nuclei that participate in a great variety of functions, ranging from motor programming and execution to procedural learning, cognition, and emotions. This network is also the region primarily affected by the degeneration of midbrain dopaminergic neurons localized in the substantia nigra pars compacta (SNc). This degeneration causes cellular and synaptic dysfunctions in the BG network, which are responsible for the appearance of the motor symptoms of Parkinson’s disease. Dopamine (DA) modulation and the consequences of its loss on the striatal microcircuit have been extensively studied, and because of the discrete nature of DA innervation of other BG nuclei, its action outside the striatum has been considered negligible. However, there is a growing body of evidence supporting functional extrastriatal DA modulation of both cellular excitability and synaptic transmission. In this review, the functional relevance of DA modulation outside the striatum in both normal and pathological conditions will be discussed.

FOXP2 contributes to the cognitive impairment in chronic patients with schizophrenia

The forkhead-box P2 (FOXP2), involving in language and memory function, has been identified as susceptibility to schizophrenia. However, no study examined the role of FOXP2 on cognitive impairment in schizophrenia. Total 1106 inpatients with schizophrenia and 404 controls were recruited and genotyped. Among them, 867 patients and 402 controls were assessed through the Repeatable Battery for the Assessment of Neuropsychological Status (RBANS). SHEsis software was used to investigate the association of FOXP2 rs10447760 with schizophrenia, followed by logistic regression. The model of covariance (ANCOVA) and multivariate analysis were conducted to investigate the effect of FOXP2 rs10447760 on cognitive impairment in schizophrenia. No differences in the genotypic and allelic frequencies of the FOXP2 rs10447760 were found between patients and controls (both p> 0.05). Except for the visuospatial/constructional score (p > 0.05), other five RBANS scores were lower in patients compared to controls (all p < 0.0001). Interestingly, we found immediate memory score was lower in patients carrying genotype CT compared to genotype CC (F=5.19, p=0.02), adjusting for confounding data. Our study suggested that FOXP2 rs10447760 has no effect on the susceptibility to schizophrenia, while it may be associated with its cognitive impairment, especially immediate memory in chronic schizophrenia.

Inter-Individual Differences in Striatal Connectivity Is Related to Executive Function Through Fronto-Parietal Connectivity

The striatum has long been associated with cognitive functions, but the mechanisms behind this are still unclear. Here we tested a new hypothesis that the striatum contributes to executive function (EF) by strengthening cortico-cortical connections. Striatal connectivity was evaluated by measuring the resting-state functional connectivity between ventral and dorsal striatum in 570 individuals, aged 3–20 years. Using structural equation modeling, we found that inter-individual differences in striatal connectivity had an indirect effect (via fronto-parietal functional connectivity) and a direct effect on a compound EF measure of working memory, inhibition, and set-shifting/flexibility. The effect of fronto-parietal connectivity on cognition did not depend on age: the influence was as strong in older as younger children. In contrast, striatal connectivity was closely related to changes in cognitive ability during childhood development, suggesting a specific role of the striatum in cognitive plasticity. These results support a new principle for striatal functioning, according to which striatum promotes cognitive development by strengthening of cortico-cortical connectivity.

A human memory circuit derived from brain lesions causing amnesia

Human memory is thought to depend on a circuit of connected brain regions, but this hypothesis has not been directly tested. We derive a human memory circuit using 53 case reports of strokes causing amnesia and a map of the human connectome (n = 1000). This circuit is reproducible across discovery (n = 27) and replication (n = 26) cohorts and specific to lesions causing amnesia. Its hub is at the junction of the presubiculum and retrosplenial cortex. Connectivity with this single location defines a human brain circuit that incorporates > 95% of lesions causing amnesia. Lesion intersection with this circuit predicts memory scores in two independent datasets (N1 = 97, N2 = 176). This network aligns with neuroimaging correlates of episodic memory, abnormalities in Alzheimer's disease, and brain stimulation sites reported to enhance memory in humans.

Partial decortication ameliorates dopamine depletion‑induced striatal neuron lesions in rats

The balance between glutamate (cortex and thalamus) and dopamine (substantia nigra) inputs on striatal neurons is of vital importance. Dopamine deficiency, which breaks this balance and leads to the domination of cortical glutamatergic inputs, plays an important role in Parkinson's disease (PD). However, the exact impact on striatal neurons has not been fully clarified. Thus, the present study aimed to characterize the influence of corticostriatal glutamatergic inputs on striatal neurons after decortication due to dopamine depletion in rats. 6-Hydroxydopamine was injected into the right medial forebrain bundle to induce dopamine depletion, and/or ibotenic acid into the primary motor cortex to induce decortication. Subsequently, the grip strength test and Morris water maze task indicated that decortication significantly shortened the hang time and the latency that had been increased in the rats subjected to dopamine depletion. Golgi staining and electron microscopy analysis showed that the total dendritic length and dendritic spine density of the striatal neurons were decreased in the dopamine-depleted rats, whereas decortication alleviated this damage. Immunohistochemistry analysis demonstrated that decortication decreased the number of caspase-3-positive neurons in the dopamine-depleted rats. Moreover, reverse transcription-quantitative PCR and western blot analyses showed that decortication offset the upregulation of caspase-3 at both the protein and mRNA levels in the dopamine-depleted rats. In conclusion, the present study demonstrated that a relative excess of cortical glutamate inputs had a substantial impact on the pathological processes of striatal neuron lesions in PD.

Synaptic signals mediated by protons and acid-sensing ion channels

Extracellular pH changes may constitute significant signals for neuronal communication. During synaptic transmission, changes in pH in the synaptic cleft take place. Its role in the regulation of presynaptic Ca²⁺ currents through multivesicular release in ribbon-type synapses is a proven phenomenon. In recent years, protons have been recognized as neurotransmitters that participate in neuronal communication in synapses of several regions of the CNS such as amygdala, nucleus accumbens, and brainstem. Protons are released by nerve stimulation and activate postsynaptic acid-sensing ion channels (ASICs). Several types of ASIC channels are expressed in the peripheral and central nervous system. The influx of Ca²⁺ through some subtypes of ASICs, as a result of synaptic transmission, agrees with the participation of ASICs in synaptic plasticity. Pharmacological and genetical inhibition of ASIC1a results in alterations in learning, memory, and phenomena like fear and cocaine-seeking behavior. The recognition of endogenous molecules, such as arachidonic acid, cytokines, histamine, spermine, lactate, and neuropeptides, capable of inhibiting or potentiating ASICs suggests the existence of mechanisms of synaptic modulation that have not yet been fully identified and that could be tuned by new emerging pharmacological compounds with potential therapeutic benefits.

Re-learning and remembering in the lesioned brain

It is well known that re-learning language skills after a brain lesion can be very difficult. However, while learning and memory challenges have been extensively researched in amnesic individuals, very little research attention has been directed at understanding the characteristics of learning and memory that are relevant to recovery and rehabilitation of acquired language impairments. Even in the absence of damage to the medial temporal lobe regions classically associated with learning and memory, these individuals often suffer damage to frontal and other subcortical areas associated with learning and memory that may contribute to the learning challenges they face. Therefore, an understanding of the learning and memory profiles of post-stroke language impairments is important for the development and optimization of rehabilitation approaches. In two studies, we examine the degree to which certain basic characteristics of learning and memory, identified in neurotypical individuals, are intact in individuals with post-stroke language impairment. We specifically consider fundamental principles regarding the optimal spacing of learning trials that have been shown to reliably operate in neurotypical adults, across a wide range of language domains. We report on two studies that examine whether or not these principles also apply in language re-learning and retention for individuals with acquired deficits in written language production. Study 1 compared distributed vs. clustered training schedules, while Study 2 examined-for the first time in the context of re-learning-the relationship between the spacing of training trials and the retention period. This investigation revealed that, despite significant cognitive deficits and brain lesions, remarkably similar principles govern re-learning and retention in the lesioned brain as have been found to apply in neurologically healthy individuals. These results allow us to begin to integrate our understanding of recovery with the broader literature on learning and memory and have implications for the optimal organization of rehabilitation. Specifically, the findings raise questions regarding the traditional compression of rehabilitation within relatively short time windows.

The effect of cognitive training on the brain's local connectivity organization in healthy older adults

Cognitive training has been shown effective in improving the cognitive function of older adults. While training related plasticity of the brain has been observed at different levels, it is still open to exploration whether local functional connectivity (FC) may be affected by training. Here, we examined the neuroimaging data from a previous randomized-controlled double-blinded behavioural study, in which healthy older adults participated in a 3-month cognitive training program. Resting-state fMRI was acquired at baseline and one year after training. The local FC in the brain was estimated using the regional homogeneity (ReHo), and the high ReHo clusters (HRCs) were extracted to quantify the level of local FC integration. Results showed that: (i) HRCs exhibited a power-law size distribution; (ii) local FC were less integrated in older participants than in younger participants; (iii) local FC in older participants of the training group became more integrated after training than the control group; (iv) the baseline local FC integration was positively correlated with educational level. These results indicated a training-related alteration in local FC.

Action Selection and Flexible Switching Controlled by the Intralaminar Thalamic Neurons

Learning processes contributing to appropriate selection and flexible switching of behaviors are mediated through the dorsal striatum, a key structure of the basal ganglia circuit. The major inputs to striatal subdivisions are provided from the intralaminar thalamic nuclei, including the central lateral nucleus (CL) and parafascicular nucleus (PF). Thalamostriatal neurons in the PF modulate the acquisition and performance of stimulus-response learning. Here, we address the roles of the CL thalamostriatal neurons in learning processes by using a selective neural pathway targeting technique. We show that the CL neurons are essential for the performance of stimulus-response learning and for behavioral flexibility, including reversal and attentional set-shifting of learned responses. In addition, chemogenetic suppression of neural activity supports the requirements of these neurons for behavioral flexibility. Our results suggest that the main contribution of the CL thalamostriatal neurons is functional control of the basal ganglia circuit linked to the prefrontal cortex.

Increased flanker task and forward digit span performance in caudate-nucleus-dependent response strategies

One of two memory systems can be used to navigate in a new environment. Hippocampus-dependent spatial strategy consists of creating a cognitive map of an environment and caudate nucleus-dependent response strategy consists of memorizing a rigid sequence of turns. Spontaneous use of the response strategy is associated with greater activity and grey matter within the caudate nucleus while the spatial strategy is associated with greater activity and grey matter in the hippocampus. The caudate nucleus is involved in executive functions such as working memory, cognitive control and certain aspects of attention such as attentional disengaging. This study therefore aimed to investigate whether response learners would display better performance on tests of executive and attention functioning compared to spatial learners. Fifty participants completed the 4/8 virtual maze to assess navigational strategy, the forward and backward visual digit span and the Attention Network Test - Revised to assess both attention disengagement and cognitive control. Results revealed that response learners showed significantly higher working memory capacity, more efficient attention disengagement and better cognitive control. Results suggest that response learners, who putatively display more grey matter and activity in the caudate nucleus, are associated with better working memory span, cognitive control and attentional disengagement.

Combined fractional anisotropy and subcortical volumetric abnormalities in healthy immigrants to high altitude: A longitudinal study

The study of individuals at high-altitude (HA) exposure provides an important opportunity for unraveling physiological and psychological mechanism of brain underlying hypoxia condition. However, this has rarely been assessed longitudinally. We aim to explore the cognitive and cerebral microstructural alterations after chronic HA exposure. We recruited 49 college freshmen who immigrated to Tibet and followed up for 2 years. Control group consisted of 49 gender and age-matched subjects from sea level. Neuropsychological tests were also conducted to determine whether the subjects' cognitive function had changed in response to chronic HA exposure. Surface-based cortical and subcortical volumes were calculated from structural magnetic resonance imaging data, and tract-based spatial statistics (TBSS) analysis of white matter (WM) fractional anisotropy (FA) based on diffusion weighted images were performed. Compared to healthy controls, the high-altitude exposed individuals showed significantly lower accuracy and longer reaction times in memory tests. Significantly decreased gray matter volume in the caudate region and significant FA changes in multiple WM tracts were observed for HA immigrants. Furthermore, differences in subcortical volume and WM integration were found to be significantly correlated with the cognitive changes after 2 years' HA exposure. Cognitive functions such as working memory and psychomotor function were found to be impaired during chronic HA. Differences of brain subcortical volumes and WM integration between HA and sea-level participants indicated potential impairments in the brain structural modifications and microstructural integrity of WM tracts after HA exposure.

Involvement of Interferon Regulatory Factor 7 in Nicotine's Suppression of Antiviral Immune Responses

Nicotine, the active ingredient in tobacco smoke, suppresses antiviral responses. Interferon regulatory factors (IRFs) regulate transcription of type I interferons (IFNs) and IFN-stimulated genes (ISGs) in this response. IRF7 is a key member of the IRF family. Expression of Irf7 is elevated in the brains of virus-infected animals, including human immunodeficiency virus-1 transgenic (HIV-1Tg) rats. We hypothesized that IRF7 affects nicotine's modulation of antiviral responses. Using CRISPR/Cas9 system, IRF7-mutant cell lines were created from human embryonic kidney 293FT cells in which 16 nicotinic acetylcholine receptors (nAChRs) were detected. Decreased expression of IRF7 was confirmed at both the mRNA and protein levels, as was IRF7-regulated cell growth in two IRF7-mutant cell lines, designated IRF7-Δ7 and IRF7-Δ11. In IRF7-Δ7 cells, expression of two nAChR genes, CHRNA3 and CHRNA9, changed modestly. After stimulation with polyinosinic-polycytidylic acid (poly I:C) (0.25 μg/ml) for 4 h to mimic viral infection, 293FT wild-type (WT) and IRF7-Δ7 cells were treated with 0, 1, or 100 μM nicotine for 24 h, which increased IFN-β expression in both types of cells but elevation was higher in WT cells (p < 0.001). Expression was significantly suppressed in WT cells (p < 0.001) but not in IRF7-Δ7 cells by 24-h nicotine exposure. Poly I:C stimulation increased mRNA expression of retinoic-acid-inducible protein I (RIG-I), melanoma-differentiation-associated gene 5 (MDA5), IFN-stimulated gene factor 3 (ISG3) complex, and IFN-stimulated genes (IRF7, ISG15, IFIT1, OAS1); nicotine attenuated mRNA expression only in WT cells. Overall, IRF7 is critical to nicotine's effect on the antiviral immune response. Graphical Abstract Involvement of IRF7 in nicotine's suppression of poly I:C-induced antiviral immune responses. PAMPs, such as a synthetic viral analogue of dsRNA poly I:C attack cells, will be recognized by PRRs, and the host innate immunity against viral infection will be activated. PRRs signaling trigger phosphorylation of IRF7 and IRF3 to induce their translocation to the nucleus and result in the production of type I IFNs. Then IFNs bind to IFNAR to activate the transcription factor ISGF3, a complex consisting of STAT1, STAT2, and IRF9. Further, it induces the expression of ISGs, including IFIT1, OAS1, IRF7, ISG15, etc. Nicotine suppresses the immune responses stimulated by poly I:C. In the IRF7-mutant cells, nicotine's suppressive effects on poly I:C-stimulated immune responses were restrained.

Atypical Dorsolateral Prefrontal Activity in Female Adolescents With Conduct Disorder During Effortful Emotion Regulation

Background

Conduct disorder (CD), which is characterized by severe aggressive and antisocial behavior, is linked to emotion processing and regulation deficits. However, the neural correlates of emotion regulation are yet to be investigated in adolescents with CD. Furthermore, it remains unclear whether CD is associated with deficits in emotional reactivity, emotion regulation, or both.

Methods

We used functional magnetic resonance imaging to study effortful emotion regulation by cognitive reappraisal in 59 female adolescents 15 to 18 years of age (30 with a CD diagnosis and 29 typically developing (TD) control adolescents).

Results

Behaviorally, in-scanner self-report ratings confirmed successful emotion regulation within each group individually but significant group differences in emotional reactivity and reappraisal success when comparing the groups (CD < TD). Functional magnetic resonance imaging results revealed significantly lower activation in left dorsolateral prefrontal cortex and angular gyrus in CD compared with TD adolescents during emotion regulation, but no group differences for emotional reactivity. Furthermore, connectivity between left dorsolateral prefrontal cortex and the bilateral putamen, right prefrontal cortex, and amygdala was reduced in CD compared with TD adolescents during reappraisal. Callous-unemotional traits were unrelated to neural activation, but these traits correlated negatively with behavioral reports of emotional reactivity.

Conclusions

Our results demonstrate reduced prefrontal brain activity and functional connectivity during effortful emotion regulation in female adolescents with CD. This sheds light on the neural basis of the behavioral deficits that have been reported previously. Future studies should investigate whether cognitive interventions are effective in enhancing emotion-regulation abilities and/or normalizing prefrontal and temporoparietal activity in female adolescents with CD.