Simulation of the neural activity underlying a short-term modification of inking behavior in aplysia

Carew and Kandel (1977) found that weak stimuli to the head or siphon fail to elicit the release of ink. When paired with each other, however, the second of the two leads to the release of ink. The present paper quantifies and simulates the neural events which underlie this short-term modification of the behavior. Noxious stimuli to the intact animal were mimicked by delivering trains of electrical stimuli to the connectives (conditioning input) and siphon nerve (test input) which drive the ink gland motor neurons located within the abdominal ganglion. Estimates of the synaptic conductance and equilibrium potential during the conditioning and test inputs were then made and used to drive a previously developed Hodgkin-Huxley model of the ink motor neurons. The experimental and simulated results are in good agreement. Activation of one stimulus pathway augments or facilitates the ability of the other pathway to fire the ink motor neurons. The behavioral modification is causally related to a sustained synaptic current activated by the conditioning stimulus.     

Neuronal mechanisms underlying control of a brain-computer interface

Brain-computer interfaces (BCIs) enable humans or animals to communicate or control external devices without muscle activity using electric brain signals. The BCI used here is based on self-regulation of slow cortical potentials (SCPs), a skill that most people and paralyzed patients can acquire with training periods of several hours up to months. The neurophysiological mechanisms and anatomical sources of SCPs and other event-related brain potentials have been described but the neural mechanisms underlying the self-regulation skill for the use of a BCI are unknown. To uncover the relevant areas of brain activation during regulation of SCPs, the BCI was combined with functional magnetic resonance imaging. The electroencephalogram was recorded inside the magnetic resonance imaging scanner in 12 healthy participants who learned to regulate their SCP with feedback and reinforcement. The results demonstrate activation of specific brain areas during execution of the brain regulation skill allowing a person to activate an external device; a successful positive SCP shift compared with a negative shift was closely related to an increase of the blood oxygen level-dependent response in the basal ganglia. Successful negativity was related to an increased blood oxygen level-dependent response in the thalamus compared with successful positivity. These results may indicate learned regulation of a cortico-striatal-thalamic loop modulating local excitation thresholds of cortical assemblies. The data support the assumption that human subjects learn the regulation of cortical excitation thresholds of large neuronal assemblies as a prerequisite for direct brain communication using an SCP-driven BCI. This skill depends critically on an intact and flexible interaction between the cortico-basal ganglia-thalamic circuits.     

Canadian Association of Neuroscience Review: Respiratory control and behavior in humans: lessons from imaging and experiments of nature

The purpose of this review is to demonstrate that respiration is a complex behavior comprising both brainstem autonomic control and supramedullary influences, including volition. Whereas some fundamental mechanisms had to be established using animal models, this review focuses on clinical cases and physiological studies in humans to illustrate normal and abnormal respiratory behavior. To summarize, central respiratory drive is generated in the rostroventrolateral medulla, and transmitted to both the upper airway and to the main and accessory respiratory muscles. Afferent feedback is provided from lung and muscle mechnoreceptors, peripheral carotid and aortic chemoreceptors, and multiple central chemoreceptors. Supramedullary regions, including cortex and subcortex, modulate or initiate breathing with volition, emotion and at the onset of exercise. Autonomic breathing control can be perturbed by brainstem pathology including space occupying lesions, compression, congenital central hypoventilation syndrome and sudden infant death syndrome. Sleep-wake states are important in regulating breathing. Thus, respiratory control abnormalities are most often evident during sleep, or during transition from sleep to wakefulness. Previously undiagnosed structural brainstem pathology may be revealed by abnormal breathing during sleep. Ondine's curse and 'the locked-in syndrome' serve to distinguish brainstem from supramedullary regulatory mechanisms in humans: The former comprises loss of autonomic respiratory control and requires volitional breathing for survival, and the latter entails loss of corticospinal or corticobulbar tracts required for volitional breathing, but preserves autonomic respiratory control.     

The dual control model of male sexual response: a theoretical approach to centrally mediated erectile dysfunction

A theoretical model of dual control of male sexual response is considered, based on the balancing of central excitation and inhibition, with individuals varying in their propensity for both sexual excitation and inhibition of sexual response. A questionnaire method for measuring propensities for sexual excitation and inhibition has been developed (SIS/SES questionnaire), resulting in one excitation factor (SES) and two inhibition factors (SIS1 and SIS2). Evidence for the existence of both inhibitory and excitatory tone is discussed. The first inhibition factor (SIS1) may be related to level of inhibitory tone and is associated with fear of performance failure. The second inhibition factor (SIS2) may be related to external threats (e.g. from within the sexual relationship). The implications for the treatment of centrally mediated erectile dysfunction are discussed, with predictions that high SIS2 individuals will respond to psychological treatment, whereas high SIS1 individuals will respond better to pharmacological methods of treatment.     

Neuronal control of bird song production

Bird song represents a powerful model system for many of the important problems in behavioral neurobiology, offering both easily measured sensory and motor patterns and a discrete neural effector system. Methods were developed to record the discharge of neurons in singing birds to examine the functions of nuclei in the song control pathway previously implicated anatomically. In several cases, lesions and other techniques were employed to test predictions derived from electrode recordings. Four major findings emerge from these studies. Single-unit recordings from telencephalic nucleus hyperstriatum ventrale, pars caudale (HVc) show several classes of neurons with apparently specialized roles in song production and/or sensorimotor interaction. The nucleus interfacialis (Nlf; Nottebohm, 1980), which provides an input to HVc and is anatomically the "highest" nucleus in the descending motor pathway, is uniquely placed among vocal control nuclei to be a generator of timing cues for song. Consistent with the unidirectional connections between nuclei of the descending pathway, Nlf, HVc, and nucleus robustus archistriatalis (RA) are activated sequentially prior to sound onset. Three other nuclei with connections to or from the descending tract do not show song-related activity in the adult. Bilateral HVc recordings and peripheral disruptions of the vocal apparatus suggest that both hemispheres and syringeal halves normally make similar contributions to most if not all song syllables. The latter finding casts doubt on the analogy between neural lateralization in bird song and in human speech.     

Respiratory control as a treatment for panic attacks

Eighteen patients who experienced frequent panic attacks were given a treatment derived from the literature on hyperventilation and anxiety. The treatment consisted of (i) brief, voluntary hyperventilation. This was intended to induce a mild panic attack; (ii) explanation of the effects of overbreathing and reattribution of the cause of a patient's attacks to hyperventilation; (iii) training in a respiratory control technique. Substantial reductions in panic attack frequency and in self-reported fear during a behaviour test were obtained after 2 weeks' treatment and these reductions occurred in the absence of exposure to feared situations. Further reductions in panic attack frequency were evident at 6-month and 2-year follow-up though interpretation of these results is complicated by the addition of exposure and other psychological treatments.     

Losing control: Assaultive behavior as a predictor of impulse control disorders in young adults

Objective

Assaultive behaviors are common among young people and have been associated with a range of other unhealthy, impulsive behaviors such as substance use and problem gambling. This study sought to determine the predictive ability of single assaultive incidents for impulse control disorders, an association that has yet to be examined, especially in young adults.

Methods

The authors conducted a university-wide email survey in the spring of 2011 on 6000 university students. The survey examined assaultive behavior and associated mental health variables (using a clinically validated screening instrument, the Minnesota Impulsive Disorders Interview), stress and mood states, and psychosocial functioning.

Results

The rate of response was 35.1% (n = 2108). 109 (5.9%) participants reported that they had assaulted another person or destroyed property at some time in their lives. Compared with respondents without lifetime assaultive behavior, those with a history of assaultive or destructive behavior reported more depressive symptoms, more stress, and higher rates of a range of impulse control disorders (intermittent explosive disorder, compulsive sexual behavior, compulsive buying, and skin picking disorder).

Conclusions

Assaultive behavior appears fairly common among college students and is associated with symptoms of depression and impulse control disorders. Significant distress and diminished behavioral control suggest that assaultive behaviors may often be associated with significant morbidity. Additional research is needed to develop specific prevention and treatment strategies for young adults attending college who report problems with assaultive behaviors.     

Pontomedullary Efferent Projections of the Ventral Respiratory Neuronal Subsets of the Rat

The pontomedullary trajectories of projections efferent from the ventral respiratory cell group were anterogradely labelled after discrete injections of Fluoro Ruby into three morphophysiologically identified subdivisions (Bötzinger complex, rostral inspiratory, and caudal expiratory cell groups). The anterogradely labelled varicosities were located in a variety of areas involved in cardiorespiratory function: other subdivisions of the ventral respiratory cell group, the parabrachial (medial, central, and external lateral), Kölliker-Fuse, and lateral paragigantocellular nuclei, A5, and perifacial areas. Although the target areas were similar for the three studied subdivisions, some differences of the location and densities of labelled varicosities were found. Anterogradely labelled fibre bundles were found bilaterally after all of the tracer injections. Three caudally efferent bundles passed through the ventral respiratory cell group, dorsal medullary, and paramedian reticular nuclei. A labelled fibre bundle also took an ascending route through the ventral respiratory cell group: it surrounded the facial nucleus, and then followed two different pathways, one coursing towards forebrain areas and the other to the parabrachial and Kölliker-Fuse complex. Bundles of efferent axons decussated mainly at medullary levels and to a lesser extent in the pons. In the contralateral medulla and pons these labelled fibre bundles followed pathways similar to those observed ipsilaterally. The three ventral respiratory neuronal subsets sent axonal projections through similar tracts, but within them they were topographically organized. The present data are discussed with respect to the circuitry involved in the mechanisms of cardiorespiratory and other visceral functions.     

Neuronal responses in monkey lateral hypothalamus during operant feeding behavior

Single neuron activity was recorded from monkey lateral hypothalamus to investigate neuronal events correlated with operant bar press feeding behavior. The behavioral paradigm was divided into three phase: visual (discrimination), bar press (procurement), and ingestion (consummatory). Of 669 neurons tested, 158 (24%) responded in one or more phases. During the visual phase, 106 neurons (16%) responded. Of 80 neurons that responded in the visual phase and were tested systematically, 33 (41%, 33/80) responded selectively to the sight of food or nonfood objects associated with a juice reward, but not to the sight of nonfood or objects associated with aversive saline. Neuronal activity related to discrimination was modulated by satiation and learning (i.e., acquisition and extinction). During the bar press phase, 51 neurons (7.6%) responded. These responded tonically during the early or late stage of the bar press period, but did not depend on individual bar pressing motions. During ingestion, 90 neurons (13%) responded. The ingestion response was modulated by palatability of food and satiation. Data suggest that the LHA is deeply involved in operant feeding behavior; discrimination of food, drive to get food, and perception of reward, all of which are affected by learning and internal states such as hunger and satiety.     

Neuronal responses in monkey anterior putamen during operant bar-press behavior

Single neuron activity was recorded in the monkey anterior putamen to compare visuomotor-related responses during operant bar-press behavior with visual discrimination of objects. Of 615 neurons recorded 9.8% ( ) responded to the presentation of food during forced delay of access to the bar. Of these 60 neurons, 38 were also tested with nonfood, and 19 of these responded to the nonfood objects regardless of the following movement. The amplitude of the visual-related responses of some differential neurons was graded for different objects to reflect the relative degree of preference for the food presented. However, these responses disappeared in reaction time tasks in which the bar could be accessed for pressing immediately upon presentation of an object. The visual response latency of differential neurons ranged from 50 to 700 ms (mean ± SD, 386 ±211 ms), which was longer than that of the nondifferential responses (207 ± 204 ms). These results suggest that anterior putamen neurons might participate in estimation of visual information that could be related to forecasting movement.     

Neuronal ceroid lipofuscinoses: a review

Neuronal ceroid lipofuscinoses (NCLs) are among the most common neurodegenerative diseases in childhood but rarely present in adulthood. The main symptoms are psychomotor deterioration, visual failure, epilepsy and motor disturbances. The NCLs are morphologically characterized by the accumulation of lipopigments within numerous cell types and loss of neurons. Pathogenesis is unknown. The current clinical classification recognizes six classic types of NCL and several atypical forms. Electrophysiological and neuroradiological findings may be of diagnostic significance, but disease recognition rests on the demonstration of a typical ultrastructural pattern. Genetic studies have demonstrated that several different genetic loci are involved in the pathogenesis of NCL, but the molecular mechanisms underlying neuronal death and lipopigment accumulation are not understood.

---

Sommario Le ceroido lipofuscinosi neuronali (NCL) sono tra le encefalopatie progressive più freguenti nell'infanzia ed interessano, seppure più raramente, l'adulto. Clinicamente sono caratterizzate da demenza, deficit visivo, epilessia e disturbi motori. Gli aspetti patologici specifici sono rappresentati da degenerazione neuronale ed accumulo lisosomiale di lipopigmento in differenti tipi cellulari. Il difetto biochimico della malattia non e noto. La classificazione delle NCL, basata su criteri clinici, distingue sei forme classiche ed altre forme atipiche. L'elettrofisiologia e la neuroradiologia sono di importante ausilio diagnostico, ma la diagnosi si fonda sull'identificazione dell'accumulo di lipopigmento the presenta pattern ultrastrutturali specifici. Differenti difetti genetici sono stati dimostrati in diverse forme cliniche, ma il meccanismo patogenetico molecolare rimane ancora da chiarire.

     

Neuronal control and monitoring of initiation of movements

The prerequisite for behavioral self-control is the ability to initiate actions and to cancel planned actions. A rational choice about which action to initiate or to withhold must be informed by the consequences of prior actions. The neuronal correlates of these processes have been studied with the countermanding paradigm. This task requires subjects to withhold planned movements in response to an imperative stop signal, which they can do with varying success. By recording the activity of single neurons in different parts of the frontal cortex of macaque monkeys performing this task, signals that are sufficient for controlling the initiation and inhibition of movements and other signals that evaluate the consequences of these movements have been identified.     

Neuronal control of neurotransmitters biosynthesis during development.

Studies on neuronal control mechanisms of neurotransmitters biosynthesis during the development of peripheral and central autonomic synapses are reviewed. Particular emphasis is placed on investigations of developing peripheral sympathetic ganglia and brain in chick embryo and chick. Studies on the development of autonomic neurons and synapses under different pharmacological conditions are reported. Principally the effect of a) the administration of drugs and precursors such as L-dopa, 3H-dopa, 6-OH dopa; b) the prenatal administration of reserpine; c) the blockade of cholinergic receptors; d) the nerve growth factor (NGF) is analyzed. Results of developmental studies on chick ciliary ganglia are summarized. The review particulary underlines the importance of combining the use of sensitive microchemical methods to pharmacological tools in exploring the development of regulatory mechanisms at the cellular level.     

Neuronal control of the pyloric sphincter of the guinea-pig

The pyloric sphincter (PS) controls gastric emptying and prevents the reflux of duodenal content into the stomach. Neuronal pathways and reflexes controlling the guinea-pig PS were physiologically investigated in isolated preparations. Simultaneous intracellular or extracellular and tension recordings from PS circular muscle with electrical and stretch stimulation were used. Electrical stimulation evoked an initial small contraction followed by a relaxation with a corresponding inhibitory junction potential (IJP) then a second large contraction with a corresponding excitatory junction potential (EJP). Hyoscine (1 micromol L-1) blocked the first contraction, and reduced the second contraction and EJP by 52.5% and 61%, respectively. These responses were further reduced by the NK2 antagonist, MEN10627 (1 micromol L-1), and the NK1 antagonist, SR140333 (1 micromol L-1). N-nitro-L-arginine (100 micro;mol L-1) and apamin (0.5 micromol L-1) blocked the relaxation and the IJP. Duodenal electrical stimulation evoked an EJP, whereas antral stimulation evoked an IJP followed by a small EJP. All were blocked by hexamethonium (100 micromol L-1). Duodenal stretch evoked tetrodotoxin-sensitive reflex contractions and membrane depolarization with action potentials in the PS. Thus, PS enteric motor neurones receive inputs from the duodenum and the stomach. There are stretch-sensitive ascending excitatory reflex pathways from the duodenum to the PS.     

Neuronal activity in female rat preoptic area associated with sexually motivated behavior

Single unit activities were recorded from 31 neurons in the preoptic area (POA) of female rats engaging in sexual interactions. Concurrent videotape recordings were used to establish a relationship between neuronal activity and particular behavioral events. In 14 of the 31 neurons, the firing rate changed in association with bouts of sexual activity. The remaining 17 fired with more variability regardless of episodes of sexual interactions. Peri-event histograms identified four types of neurons: type 1 (n=4) increased their firing rate when the female rats initiated proceptive behavior; type 2 (n=4) showed a brief activation when the male mounted; type 3 (n=4) fired in response to intromission, and type 4 (n=2) were inhibited prior to and throughout the display of lordosis reflex. Type 1 neurons fired at significantly higher rates during the solicitatory period, from the initiation of solicitatory locomotion to the male mounts. Their activity was suppressed when the males mounted successfully with intromission. Types 1–3 neurons were recorded from the transitional region between the medial and lateral POAs. Type 4 neurons were located more medially in the medial POA. Systemic injection of pimozide, a dopamine receptor blocker, diminished firing in type 1 neurons and abolished proceptivity. The firing pattern in type 1 neurons appeared to embody the motivational state of the animal with an implication for a consummatory value of penile intromission. Visceral or somatosensory inputs may be responsible for short bursts in types 2 and 3 neurons. Type 4 neurons behaved exactly as if they inhibit the execution of the lordosis reflex. The results showed separate sets of POA neurons each specifically associated with proceptive and receptive components of female rat sexual behavior.