Correlated signatures of social behavior in cerebellum and anterior cingulate cortex

The cerebellum has been implicated in the regulation of social behavior. Its influence is thought to arise from communication, via the thalamus, to forebrain regions integral in the expression of social interactions, including the anterior cingulate cortex (ACC). However, the signals encoded or the nature of the communication between the cerebellum and these brain regions is poorly understood. Here, we describe an approach that overcomes technical challenges in exploring the coordination of distant brain regions at high temporal and spatial resolution during social behavior. We developed the E-Scope, an electrophysiology-integrated miniature microscope, to synchronously measure extracellular electrical activity in the cerebellum along with calcium imaging of the ACC. This single coaxial cable device combined these data streams to provide a powerful tool to monitor the activity of distant brain regions in freely behaving animals. During social behavior, we recorded the spike timing of multiple single units in cerebellar right Crus I (RCrus I) Purkinje cells (PCs) or dentate nucleus (DN) neurons while synchronously imaging calcium transients in contralateral ACC neurons. We found that during social interactions a significant subpopulation of cerebellar PCs were robustly inhibited, while most modulated neurons in the DN were activated, and their activity was correlated with positively modulated ACC neurons. These distinctions largely disappeared when only non-social epochs were analyzed suggesting that cerebellar-cortical interactions were behaviorally specific. Our work provides new insights into the complexity of cerebellar activation and co-modulation of the ACC during social behavior and a valuable open-source tool for simultaneous, multimodal recordings in freely behaving mice.

Correlated signatures of social behavior in cerebellum and anterior cingulate cortex

The cerebellum has been implicated in the regulation of social behavior. Its influence is thought to arise from communication, via the thalamus, to forebrain regions integral in the expression of social interactions, including the anterior cingulate cortex (ACC). However, the signals encoded or the nature of the communication between the cerebellum and these brain regions is poorly understood. Here, we describe an approach that overcomes technical challenges in exploring the coordination of distant brain regions at high temporal and spatial resolution during social behavior. We developed the E-Scope, an electrophysiology-integrated miniature microscope, to synchronously measure extracellular electrical activity in the cerebellum along with calcium imaging of the ACC. This single coaxial cable device combined these data streams to provide a powerful tool to monitor the activity of distant brain regions in freely behaving animals. During social behavior, we recorded the spike timing of multiple single units in cerebellar right Crus I (RCrus I) Purkinje cells (PCs) or dentate nucleus (DN) neurons while synchronously imaging calcium transients in contralateral ACC neurons. We found that during social interactions a significant subpopulation of cerebellar PCs were robustly inhibited, while most modulated neurons in the DN were activated, and their activity was correlated with positively modulated ACC neurons. These distinctions largely disappeared when only non-social epochs were analyzed suggesting that cerebellar-cortical interactions were behaviorally specific. Our work provides new insights into the complexity of cerebellar activation and co-modulation of the ACC during social behavior and a valuable open-source tool for simultaneous, multimodal recordings in freely behaving mice.

A novel, ataxic mouse model of ataxia telangiectasia caused by a clinically relevant nonsense mutation

Ataxia Telangiectasia (A-T) and Ataxia with Ocular Apraxia Type 1 (AOA1) are devastating neurological disorders caused by null mutations in the genome stability genes, A-T mutated (ATM) and Aprataxin (APTX), respectively. Our mechanistic understanding and therapeutic repertoire for treating these disorders are severely lacking, in large part due to the failure of prior animal models with similar null mutations to recapitulate the characteristic loss of motor coordination (i.e., ataxia) and associated cerebellar defects. By increasing genotoxic stress through the insertion of null mutations in both the Atm (nonsense) and Aptx (knockout) genes in the same animal, we have generated a novel mouse model that for the first time develops a progressively severe ataxic phenotype associated with atrophy of the cerebellar molecular layer. We find biophysical properties of cerebellar Purkinje neurons (PNs) are significantly perturbed (e.g., reduced membrane capacitance, lower action potential [AP] thresholds, etc.), while properties of synaptic inputs remain largely unchanged. These perturbations significantly alter PN neural activity, including a progressive reduction in spontaneous AP firing frequency that correlates with both cerebellar atrophy and ataxia over the animal’s first year of life. Double mutant mice also exhibit a high predisposition to developing cancer (thymomas) and immune abnormalities (impaired early thymocyte development and T-cell maturation), symptoms characteristic of A-T. Finally, by inserting a clinically relevant nonsense-type null mutation in Atm, we demonstrate that Small Molecule Read-Through (SMRT) compounds can restore ATM production, indicating their potential as a future A-T therapeutic.

Optogenetic fMRI and electrophysiological identification of region-specific connectivity between the cerebellar cortex and forebrain

Complex animal behavior is produced by dynamic interactions between discrete regions of the brain. As such, defining functional connections between brain regions is critical in gaining a full understanding of how the brain generates behavior. Evidence suggests that discrete regions of the cerebellar cortex functionally project to the forebrain, mediating long-range communication potentially important in motor and non-motor behaviors. However, the connectivity map remains largely incomplete owing to the challenge of driving both reliable and selective output from the cerebellar cortex, as well as the need for methods to detect region specific activation across the entire forebrain. Here we utilize a paired optogenetic and fMRI (ofMRI) approach to elucidate the downstream forebrain regions modulated by activating a region of the cerebellum that induces stereotypical, ipsilateral forelimb movements. We demonstrate with ofMRI, that activating this forelimb motor region of the cerebellar cortex results in functional activation of a variety of forebrain and midbrain areas of the brain, including the hippocampus and primary motor, retrosplenial and anterior cingulate cortices. We further validate these findings using optogenetic stimulation paired with multi-electrode array recordings and post-hoc staining for molecular markers of activated neurons (i.e. c-Fos). Together, these findings demonstrate that a single discrete region of the cerebellar cortex is capable of influencing motor output and the activity of a number of downstream forebrain as well as midbrain regions thought to be involved in different aspects of behavior.

Circuit mechanisms underlying motor memory formation in the cerebellum

The cerebellum stores associative motor memories essential for properly timed movement; however, the mechanisms by which these memories form and are acted upon remain unclear. To determine how cerebellar activity relates to movement and motor learning, we used optogenetics to manipulate spontaneously firing Purkinje neurons (PNs) in mouse simplex lobe. Using high-speed videography and motion tracking, we found that altering PN activity produced rapid forelimb movement. PN inhibition drove movements time-locked to stimulus onset, whereas PN excitation drove delayed movements time-locked to stimulus offset. Pairing either PN inhibition or excitation with sensory stimuli triggered the formation of robust, associative motor memories; however, PN excitation led to learned movements whose timing more closely matched training intervals. These findings implicate inhibition of PNs as a teaching signal, consistent with a model whereby learning leads first to reductions in PN firing that subsequently instruct circuit changes in the cerebellar nucleus.

Control of submillisecond synaptic timing in binaural coincidence detectors by K(v)1 channels

Neurons in the medial superior olive process sound-localization cues via binaural coincidence detection, in which excitatory synaptic inputs from each ear are segregated onto different branches of a bipolar dendritic structure and summed at the soma and axon with submillisecond time resolution. Although synaptic timing and dynamics critically shape this computation, synaptic interactions with intrinsic ion channels have received less attention. Using paired somatic and dendritic patch-clamp recordings in gerbil brainstem slices together with compartmental modeling, we found that activation of K(v)1 channels by dendritic excitatory postsynaptic potentials (EPSPs) accelerated membrane repolarization in a voltage-dependent manner and actively improved the time resolution of synaptic integration. We found that a somatically biased gradient of K(v)1 channels underlies the degree of compensation for passive cable filtering during propagation of EPSPs in dendrites. Thus, both the spatial distribution and properties of K(v)1 channels are important for preserving binaural synaptic timing.

Posthearing developmental refinement of temporal processing in principal neurons of the medial superior olive

In mammals, principal neurons of the medial superior olive (MSO) exhibit biophysical specializations that enable them to detect sound localization cues with microsecond precision. In the present study, we used whole-cell patch recordings to examine the development of the intrinsic electrical properties of these neurons in brainstem slices from postnatal day 14 (P14) to P38 gerbils. In the week after hearing onset (P14-P21), we observed dramatic reductions in somatic EPSP duration, input resistance, and membrane time constant. Surprisingly, somatically recorded action potentials also dramatically declined in amplitude over a similar period (38 +/- 3 to 17 +/- 2 mV; tau = 5.2 d). Simultaneous somatic and dendritic patch recordings revealed that these action potentials were initiated in the axon, which primarily emerged from the soma. In older gerbils, the rapid speed of membrane voltage changes and the attenuation of action potential amplitudes were mediated extensively by low voltage-activated potassium channels containing the Kv1.1 subunit. In addition, whole-cell voltage-clamp recordings revealed that these potassium channels increase nearly fourfold from P14 to P23 and are thus a major component of developmental changes in excitability. Finally, the electrophysiological features of principal neurons of the medial nucleus of the trapezoid body did not change after P14, indicating that posthearing regulation of intrinsic membrane properties is not a general feature of all time-coding auditory neurons. We suggest that the striking electrical segregation of the axon from the soma and dendrites of MSO principal neurons minimizes spike-induced distortion of synaptic potentials and thus preserves the accuracy of binaural comparisons.

D(2), but not D(1) dopamine receptor agonists potentiate cannabinoid-induced sedation in nonhuman primates

In primates, CB(1) cannabinoid receptor agonists produce sedation and psychomotor slowing, in contrast to behavioral stimulation produced by high doses of dopamine receptor agonists. To investigate whether dopamine agonists attenuate the sedative effects of a cannabinoid agonist in monkeys, we compared the effects of D(1) or D(2) dopamine receptor agonists on spontaneous behavior in three to six cynomolgus monkeys (Macaca fasicularis) alone and after administration of a low dose of the CB(1) agonist levonantradol. Alone, the CB(1) cannabinoid receptor agonist levonantradol (0.01-0. 3 mg/kg) induced sedation, ptosis, and decreased locomotor and general activity. Alone, D(2)-type dopamine agonists quinelorane (0. 001-1.0 mg/kg; n = 4) or pergolide (0.01-1.0 mg/kg) or a D(1) dopamine agonist 6-chloro-7,8-dihydroxy-1-phenyl-2,3,4, 5-tetrahydro-3-allyl-[1H]-3-benzazepine (0.3-3.0 mg/kg) produced either no effect or promoted hyperactivity. Thirty minutes after administration of a threshold dose of levonantradol (0.03 mg/kg), D(2)-type agonists, but not the D(1) agonist, precipitated marked sedation, ptosis, and decreased general activity and locomotor activity. These data inducate the following: 1) D(2,) but not D(1) dopamine agonists, potentiate sedation in monkeys treated with a CB(1) cannabinoid agonist, at doses of agonists that alone do not produce sedation; 2) the threshold dose for cannabinoid-induced sedation is reduced by D(2) agonists, but not by a D(1) dopamine agonist, differentiating D(1) and D(2) dopamine receptor linkage to cannabinoid receptors; and 3) modulation of D(2) dopamine receptor activity by a nonsedating dose of a cannabinoid agonist has implications for the pathophysiology and treatment of dopamine-related neuropsychiatric disorders and drug addiction. Cannabinoid agonists and D(2) dopamine agonists should be combined with caution.

Reducing the risks of ventilator-associated infections

Mechanically ventilated patients are at high risk for developing nosocomial pneumonia. This article reviews the pathogenesis of ventilator-associated infections and ways nurses can intervene to reduce the risks to patients and to themselves.

Co-oximetry

The adequacy of tissue oxygenation depends on the interaction of many factors. Assuming the presence of sufficient tissue perfusion, oxygenation failure must be caused by depressed respiratory efficiency (shunt or other ventilation/perfusion mismatch), inadequate FIO2/PaO2 relationships (alveolar-capillary diffusion deficits, for example), or oxygen transport difficulties (hemoglobin loading/unloading dysfunction). When presented with patients whose respiratory distress is not alleviated by application of increasing levels of FIO2 and seemingly adequate SaO2 values, one must look toward less obvious reasons for the disparity between subjective and objective findings. Early response by clinicians to situations such as those just mentioned should include a survey and analysis of hemoglobin status. It is important to note that meaningful co-oximetry results depend on the quality of the patient history and other laboratory tests to rule out factors that might affect the co-oximetry results. Good preparation of the sample is essential to ensure that adequate hemolysis has occurred and that the sample was not contaminated prior to analysis. A well designed and executed program of preventive maintenance and QA is important. It should include preparation and sampling as well as technique and instrument integrity. All of these are essential for safe, effective, and accurate determination and dissemination of this important clinical information.

Wernicke and Alzheimer on the language disturbances of dementia and aphasia

Signs of language dysfunction in dementia of the Alzheimer's type (DAT) and in the aphasic syndromes of transcortical sensory aphasia and Wernicke's aphasia are superficially similar. The unresolved question concerning the extent to which the language disturbances of DAT are "aphasic" is linked to a more fundamental question concerning the relation of language to thought, given that aphasia is often defined as language disturbance without disturbance of intellect, and dementia as dissolution of intellectual function, of which language forms an integral part. In this paper we explore the historical roots of today's debate by analyzing the original case studies of Wernicke (1874) and Alzheimer (1907, 1911). Although each of these neurologists described similar patterns of language disturbance, they drew different conclusions. Wernicke argued for a distinction between language and thought and between the language disturbances of aphasia and those of dementia. Alzheimer continued the then dominant paradigm of aphasia in describing the language disturbances of his demented patients as aphasic. Paradoxically his conclusion makes him appear, in contrast to Wernicke, to argue for the identity of the language disturbances of aphasia and dementia. Yet he himself acknowledged that the presence of focal language symptoms arising from diffuse degenerative pathology was indeed problematic. We conclude that today's discussion could profitably be refocused on the question which emerges from the original works of Wernicke and Alzheimer, which Alzheimer himself asked, and which remains unanswered: How can diffuse cerebral pathology give rise to a pattern of language deficit virtually identical to that of a focal lesion?

Needs: importance and satisfaction in respiratory therapy personnel

Using Maslow's hierarchy of needs as a base, this article attempts to determine the motivational level of respiratory therapy personnel. Also analyzed was the importance of these needs to the individuals studied. The instrument used to obtain the necessary data was a questionnaire designed to indicate a mathematical score relevant to a person's position in the hierarchy. This instrument was designed by Lyman Porter and is called the Porter needs-satisfaction index (PNSI). The respondents, who were representatives of all classes of respiratory therapy personnel, showed high levels of satisfaction in areas concerned with helping others, autonomy, and prestige. They ranked ability to help others, self-fulfillment, and feelings of accomplishment as highly important. Further analysis of the questionnaires is presently under way. It is hoped that data relative to position in the hierarchy based on demographic data will soon be available.