Effects of lesions of globus pallidus on species-typical display behavior of squirrel monkeys

The Psychopharmacology of Obsessive-Compulsive Disorder: A Preclinical Roadmap

This review evaluates current knowledge about obsessive-compulsive disorder (OCD), with the goal of providing a roadmap for future directions in research on the psychopharmacology of the disorder. It first addresses issues in the description and diagnosis of OCD, including the structure, measurement, and appropriate description of the disorder and issues of differential diagnosis. Current pharmacotherapies for OCD are then reviewed, including monotherapy with serotonin reuptake inhibitors and augmentation with antipsychotic medication and with psychologic treatment. Neuromodulatory therapies for OCD are also described, including psychosurgery, deep brain stimulation, and noninvasive brain stimulation. Psychotherapies for OCD are then reviewed, focusing on behavior therapy, including exposure and response prevention and cognitive therapy, and the efficacy of these interventions is discussed, touching on issues such as the timing of sessions, the adjunctive role of pharmacotherapy, and the underlying mechanisms. Next, current research on the neurobiology of OCD is examined, including work probing the role of various neurotransmitters and other endogenous processes and etiology as clues to the neurobiological fault that may underlie OCD. A new perspective on preclinical research is advanced, using the Research Domain Criteria to propose an adaptationist viewpoint that regards OCD as the dysfunction of a normal motivational system. A systems-design approach introduces the security motivation system (SMS) theory of OCD as a framework for research. Finally, a new perspective on psychopharmacological research for OCD is advanced, exploring three approaches: boosting infrastructure facilities of the brain, facilitating psychotherapeutic relearning, and targeting specific pathways of the SMS network to fix deficient SMS shut-down processes. SIGNIFICANCE STATEMENT: A significant proportion of patients with obsessive-compulsive disorder (OCD) do not achieve remission with current treatments, indicating the need for innovations in psychopharmacology for the disorder. OCD may be conceptualized as the dysfunction of a normal, special motivation system that evolved to manage the prospect of potential danger. This perspective, together with a wide-ranging review of the literature, suggests novel directions for psychopharmacological research, including boosting support systems of the brain, facilitating relearning that occurs in psychotherapy, and targeting specific pathways in the brain that provide deficient stopping processes in OCD.

Mouse vocal communication system: are ultrasounds learned or innate?

Mouse ultrasonic vocalizations (USVs) are often used as behavioral readouts of internal states, to measure effects of social and pharmacological manipulations, and for behavioral phenotyping of mouse models for neuropsychiatric and neurodegenerative disorders. However, little is known about the neurobiological mechanisms of rodent USV production. Here we discuss the available data to assess whether male mouse song behavior and the supporting brain circuits resemble those of known vocal non-learning or vocal learning species. Recent neurobiology studies have demonstrated that the mouse USV brain system includes motor cortex and striatal regions, and that the vocal motor cortex sends a direct sparse projection to the brainstem vocal motor nucleus ambiguous, a projection previously thought be unique to humans among mammals. Recent behavioral studies have reported opposing conclusions on mouse vocal plasticity, including vocal ontogeny changes in USVs over early development that might not be explained by innate maturation processes, evidence for and against a role for auditory feedback in developing and maintaining normal mouse USVs, and evidence for and against limited vocal imitation of song pitch. To reconcile these findings, we suggest that the trait of vocal learning may not be dichotomous but encompass a broad spectrum of behavioral and neural traits we call the continuum hypothesis, and that mice possess some of the traits associated with a capacity for limited vocal learning.

Brain mechanisms for offense, defense, and submission

A preliminary attempt is made to analyze the intraspecific aggressive behavior of mammals in terms of specific neural circuitry. The results of stimulation, lesion, and recording studies of aggressive behavior in cats and rats are reviewed and analyzed in terms of three hypothetical motivational systems: offense, defense, and submission. A critical distinction, derived from ethological theory, is made between motivating stimuli that simultaneously activate functional groupings of motor patterning mechanisms, and releasing and directing stimuli that are necessary for the activation of discrete motor patterning mechanisms. It is suggested that motivating stimuli activate pathways that converge upon sets of homogeneous neurons, called motivational mechanisms, whose activity determines the motivational state of the animal.

A defense motivational mechanism is hypothesized to be located in the midbrain central gray. In addition to tactile, auditory, and visual inputs from the paleospinothalamic tract, lateral lemniscus, and (perhaps) from the pretectum, it may receive inputs from a major forebrain pathway whose functional significance is not yet understood.

A submission motivational mechanism is also thought to be located in the central gray. In addition to inputs for defense, it is thought to receive a necessary input from a “consociate (social familiarity cue) modulator” located in the ventromedial hypothalamus, which can switch behavior from defense to submission. The location of the hypothetical offense motivational mechanism is not known, although the pathways by which it is activated are traced in some detail.

Brain mechanisms of aggression in primitive mammals and in primates are apparently similar to those in rats and cats.

The mouse who couldn't stop washing: pathologic grooming in animals and humans

The basic science literature is replete with descriptions of naturally occurring or experimentally induced pathological grooming behaviors in animals, which are widely considered animal models of obsessive-compulsive disorder (OCD). These animal models rely largely on observed similarities between animal behaviors and human OCD behaviors, and on studies of animal pathological grooming disorders that respond to serotonin enhancing drugs. However, current limitations in assessment of complex cognition and affect in animals precludes the field's ability to match the driving primary processes behind observable phenomenology in animal "OCD" with human behavioral disorders. We propose that excessive grooming behaviors in animals may eventually prove to be equally, or possibly more relevant to, other conditions in humans that involve pathological grooming or grooming-like behaviors, such as trichotillomania, body dysmorphic disorder, olfactory reference syndrome, compulsive skin-picking, and onychophagia. Research is needed to better understand pathological grooming behaviors in both humans and animals, as animal models have the potential to elucidate pathogenic mechanisms and inform the treatment of these psychiatric conditions in humans.

Assessing the validity of current mouse genetic models of obsessive-compulsive disorder

Obsessive-compulsive disorder (OCD) is a disorder characterized by unwanted and intrusive thoughts, images, or impulses and/or repetitive behavior. OCD is a major cause of disability; however, the genetic factors and pathophysiological mechanisms underlying this complex, heterogeneous disorder remain largely unknown. During the past decade, a number of putative mouse genetic models of OCD have been developed for the purpose of studying the neural mechanisms underlying this disorder and developing novel treatments. This review presents and evaluates these experimental preparations to date. Models using knockout or transgenic approaches, as well as those examining variation in genetically diverse populations, are evaluated and discussed.

The scientific contributions of Paul D. MacLean (1913-2007)

Paul D. MacLean, a leading brain scientist of the 20th century, died on December 26, 2007. We review his life as a scientist and highlight some of his most important research contributions.

Preferential responses in amygdala and insula during presentation of facial contempt and disgust

Some authors consider contempt to be a basic emotion while others consider it a variant of disgust. The neural correlates of contempt have not so far been specifically contrasted with disgust. Using functional magnetic resonance imaging (fMRI), we investigated the neural networks involved in the processing of facial contempt and disgust in 24 healthy subjects. Facial recognition of contempt was lower than that of disgust and of neutral faces. The imaging data indicated significant activity in the amygdala and in globus pallidus and putamen during processing of contemptuous faces. Bilateral insula and caudate nuclei and left as well as right inferior frontal gyrus were engaged during processing of disgusted faces. Moreover, direct comparisons of contempt vs. disgust yielded significantly different activations in the amygdala. On the other hand, disgusted faces elicited greater activation than contemptuous faces in the right insula and caudate. Our findings suggest preferential involvement of different neural substrates in the processing of facial emotional expressions of contempt and disgust.

Recent advances in Tourette syndrome research

Tourette syndrome (TS) is a developmentally regulated neurobehavioral disorder characterized by involuntary, stereotyped, repetitive movements. Recent anatomical and neuroimaging studies have provided evidence for abnormal basal ganglia and dopaminergic function in TS. Basic research on striatal inhibitory mechanisms and dopaminergic function complements the recent neuroimaging and anatomical data. Parallel studies of basal ganglia participation in the normal performance and learning of stereotyped repetitive behaviors or habits has provided additional insight. These lines of research have provided new pieces to the TS puzzle, and their increasing convergence is showing how those pieces can be put together.

Molecular mapping of striatal subdivisions in juvenile Macaca Mulata

The striatum of the primate brain can be subdivided into three distinct anatomical subregions: caudate (CAU), putamen (PUT), and ventral striatum (VS). Although these subregions share several anatomical connections, cell morphological, and histochemical features, they differ considerably in their vulnerability to different neurological and psychiatric diseases, and these brain regions have significantly different functions in health and disease. In order to better understand the molecular underpinnings of the different disease and functional vulnerabilities, transcriptional profiles were generated from the CAU, PUT, and VS of five juvenile rhesus macaques (Macaca mulatta) using human cDNA neuromicroarrays containing triplicate spots of 1227 cDNAs. Differences in microarray gene expression were assessed using z score analysis and 1.5-fold change between paired subregions. Clustering of genes based on dissimilarity of expression patterns between regions revealed subregion specific expression profiles encoding G-protein-coupled receptor signaling transcripts, transcription factors, kinases and phosphatases, and cell signaling and signal transduction transcripts. Twelve transcripts were examined using quantitative real-time PCR (qPCR), and 81% demonstrated alterations similar to those seen with microarray analysis, some of which were statistically significant. Subregion specific transcription profiles support the anatomical differentiation and potential disease vulnerabilities of the respective subregions.

Obsessive-compulsive disorder as a disturbance of security motivation

The authors hypothesize that the symptoms of obsessive-compulsive disorder (OCD), despite their apparent nonrationality, have what might be termed an epistemic origin--that is, they stem from an inability to generate the normal "feeling of knowing" that would otherwise signal task completion and terminate the expression of a security motivational system. The authors compare their satiety-signal construct, which they term yedasentience, to various other senses of the feeling of knowing and indicate why OCD-like symptoms would stem from the abnormal absence of such a terminator emotion. In addition, they advance a tentative neuropsychological model to explain its underpinnings. The proposed model integrates many previous disparate observations and concepts about OCD and embeds it within the broader understanding of normal motivation.

Vocal communication and the triune brain

This paper tests the 'fit' between Paul MacLean's triune brain scheme of brain organization and existing knowledge about the pathways mediating vocal communication in mammals. One component of MacLean's limbic system ('paleomammalian brain'), the 'thalamocingulate circuit,' is found to have an important role in expression of vocalizations, particularly the 'isolation call' (such as are given by mammalian infants when distressed or separated from their caregivers). Recent evidence suggests that this circuit may also have a role in perception of infant cries in humans. Outside of this circuit, the triune brain model has little to offer in the way of insights into how the brain is organized to mediate vocal communication. There is little evidence that the striatal complex ('R-complex' or 'protoreptilian formation') is involved in any major way in vocal communication, although it appears to be involved in some visual displays in both reptiles and nonhuman primates. Interestingly, components of the reptilian brain may be involved in human speech production, and avian homologues involved in birdsong. The neocortex ('neomammalian formation') has well-known importance in speech production and perception, but little evidence exists for a role in vocal production in nonhuman mammals. However, cortical mechanisms do play a role in perception of vocalizations, at least in nonhuman primates. It is concluded that a set of neural structures termed the 'communication brain' mediate vocal communication in mammals, and that this model does not fit well into the triune brain scheme of brain organization.

Basal ganglia systems in ritualistic social displays: reptiles and humans; function and illness

Complex, situation-specific territorial maintenance routines are similar across living terrestrial vertebrates (=amniotes). Decades ago, Paul MacLean et al., at the Laboratory of Brain Evolution and Behavior of the National Institute of Mental Health, postulated that these are evolutionarily conserved behaviors whose expression is mediated by the similarly conserved amniote basal ganglia and related brain systems (BG systems). Therefore, they undertook studies in nonhuman primates and in small social lizards (the common green anole, Anolis carolinensis) to examine this idea. MacLean et al. also postulated that when BG systems misfunction in humans, behavioral abnormalities result, some of them under the rubric of psychiatric illnesses. Obsessive-compulsive disorder (OCD) was singled out as one likely candidate. In the last dozen years, functional brain imaging studies of OCD patients have validated the contention that this is, in fact, a condition involving dysfunctioning BG systems. Inspired by the MacLean group's original investigations, my colleagues and I have now applied related functional imaging techniques in naturalistic experiments using Anolis to better understand BG systems' roles in the mediation of complex behavioral routines in healthy amniotes. Here, I will review this functional imaging work in primates (man, and a little in monkey) and in lizards. I believe the literature not only supports MacLean et al.'s contentions about BG systems and behavior in general, but also validates Paul MacLean's life-long contention that human behavioral medicine can profit from a broad comparative approach.

Sociality, stress, and the corpus striatum of the green anolis lizard

The green anolis lizard, Anolis carolinensis, is a uniquely convenient species with great potential for providing insights about the causes and consequences of social behavior from an evolutionary perspective. In this species, social interactions are mediated by visual displays in which specific units of behavior are combined in various ways to communicate several more-or-less specific messages. Two related research programs that utilize this species converge in provocative ways to provide insight into this phenomenon. The first program is centered on the basal ganglia, now known to be crucial to the expression of aggressive territoriality in this species, and the second research program examines the way the physiological stress response is involved in aggression and its subsequent adaptive outcomes. Both the neural and the neuroendocrine systems affect the progress of social interactions as well as the subsequent social dominance relationships when combatants subsequently live together. Further, because body color depends almost exclusively on the stress response, skin color provides a unique in situ bioassay of otherwise inaccessible information about the animal's internal state. The fullest understanding of the physiological ethology of this model species will depend on an interdisciplinary approach that considers both proximate (physiological) and ultimate (evolutionary) causes of displays. Questions thus arising include how the nervous system controls and assembles the specific units of behavior-motor patterns and autonomic reflexes-into displays that are adaptive in specific contexts.

Animal models of neurological deficits: how relevant is the rat?

Animal models of neurological deficits are essential for the assessment of new therapeutic options. It has been suggested that rats are not as appropriate as primates for the symptomatic modelling of disease, but a large body of data argues against this view. Comparative analyses of movements in rats and primates show homology of many motor patterns across species. Advances have been made in identifying rat equivalents of akinesia, tremor, postural deficits and dyskinesia, which are relevant to Parkinson's disease. Rat models of hemiplegia, neglect and tactile extinction are useful in assessing the outcome of ischaemic or traumatic brain injury, and in monitoring the effects of therapeutic interventions. Studies in rodents that emphasize careful behavioural analysis should continue to be developed as effective and inexpensive models that complement studies in primates.

Hoxb8 is required for normal grooming behavior in mice

Repertoires of grooming behaviors critical to survival are exhibited by most animal species, including humans. Genes that influence this complex behavior are unknown. We report that mice with disruptions of Hoxb8 show, with 100% penetrance, excessive grooming leading to hair removal and lesions. Additionally, these mice excessively groom normal cagemates. We have been unable to detect any skin or PNS abnormalities in Hoxb8 mutants. These observations suggest that the excessive, pathological grooming exhibited by these mice results from CNS abnormalities. Consistent with this interpretation, we demonstrate Hoxb8 expression in regions of the adult mouse CNS previously implicated in the control of grooming. The aberrant behavior observed in Hoxb8 mutants is not unlike that of humans suffering from the OC-spectrum disorder, trichotillomania. Interestingly, Hoxb8 is expressed in regions of the CNS known as the "OCD-circuit."

Brain mediation of Anolis social dominance displays. I. Differential basal ganglia activation

Ritualistic displays of aggressive intent are important social signals, often obviating physically dangerous engagement. To date, however, brain regions mediating such behaviors are not established. Here we used male Anolis carolinensis together with an in vivo 14C-2-deoxyglucose method to determine patterns of brain activation during elicitation of this animal's dominance displays vs. other behaviors. By patching one eye regional brain activation in the hemisphere receiving display-evocative visual stimuli ('seeing' side) was compared to activity in the contralateral brain that did not see specific stimuli ('patched' side); this was quantitated as the ratio of seeing/patched activity for brain regions of interest. Lone males displaying dominantly to mirrors activated dorsolateral basal ganglia (BG) in the seeing, compared to the patched hemisphere; this was not seen in various non-displaying controls. Degree of dorsolateral BG activation also correlated with a measure of dominant display activity, but not with locomotion. In socially stable pairs, displaying dominants showed similar activation of dorsolateral BG, but deactivated ventromedial BG; non-dominant cagemates displaying submissively had the opposite pattern. When cohabiting peacefully without displaying, paired dominants' and subordinates' brain activity patterns were similar to each other. Thus, different BG subsystems seem involved in dominant vs. submissive display behaviors. Given similarities in both social displays and BG organization, homologous brain systems might have similar functions in members of other amniote classes, including primates.

Mammal-like striatal functions in Anolis. I. Distribution of serotonin receptor subtypes, and absence of striosome and matrix organization

Serotonin (5-HT) 5-HT(2A) and 5-HT(2C) receptors are thought to play important roles in the mammalian striatum. As basal ganglia functions in general are thought highly conserved among amniotes, we decided to use in situ autoradiographic methods to determine the occurrence and distribution of pharmacologically mammal-like 5-HT(2A) and 5-HT(2C) receptors in the lizard, Anolis carolinensis, with particular attention to the striatum. We also determined the distributions of 5-HT(1A), 5-HT(1B/D), 5 HT(3), and 5-HT(uptake) receptors for comparison. All 5-HT receptors examined showed pharmacological binding specificity, and forebrain binding density distributions that resembled those reported for mammals. Anolis 5 HT(2A/C) and 5-HT(1A) site distributions were similar in both in vivo and ex vivo binding experiments. 5-HT(2A & C) receptors occur in both high and low affinity states, the former having preferential affinity for (125)I-(+/-)-2,5-dimethoxy-4-iodo-amphetamine hydrochloride ((125)I-DOI). In mammals (125)I-DOI binding shows a patchy density distribution in the striatum, being more dense in striosomes than in surrounding matrix. There was no evidence of any such patchy density of (125)I-DOI binding in the anole striatum, however. As a further indication that anoles do not possess a striosome and matrix striatal organization, neither (3)H-naloxone binding nor histochemical staining for acetylcholinesterase activity (AChE) were patchy. AChE did show a band-like striatal distribution, however, similar to that seen in birds.

Advances in the neurobiology of obsessive-compulsive disorder. Implications for conceptualizing putative obsessive-compulsive and spectrum disorders

Several approaches to the spectrum of obsessive-compulsive spectrum disorders have been put forward, each based on a rather different framework. To some extent, overlaps exist among these approaches, indicating that the neurobiology of OCD and related disorders is increasingly consolidated; however, important differences exist between these approaches, and many questions are unanswered, demonstrating that more work is necessary to fully delineate OCD and its subtypes and their relationships to other putative obsessive compulsive spectrum disorders. Despite the need for substantial additional research on the neurobiology of the obsessive-compulsive spectrum, this construct already has heuristic value in the clinical and research setting. It reminds clinicians to ask OCD patients about comorbid spectrum disorders, and it suggests the possible value of anti-OCD agents and behavioral techniques in patients for whom treatments were previously unavailable. It reminds investigators to consider possibly overlapping and differentiating mechanisms in several disorders. Ultimately, the delineation of such mechanisms will allow for a more rigorous approach to the putative obsessive-compulsive spectrum disorders.

Neurosurgical treatment of neuropsychiatric illness

Neurosurgical treatment of neuropsychiatric illness has evolved considerably since its inception in 1935. The most common psychiatric indications for the procedure, including obsessive-compulsive disorder and major depression, are conceptualized as disorders involving the basal ganglia and limbic system. In this article, the various operations and their contemporary applications are discussed. Neurosurgical treatment represents a viable option in appropriate candidates suffering from severe and otherwise treatment-refractory neuropsychiatric diseases.

A neuro-evolutionary approach to the anxiety disorders

BACKGROUND

Advances in our understanding of the anxiety disorders and in the application of evolutionary principles to medicine provide the possible basis for a neuro-evolutionary approach to these conditions. In this paper, initial steps taken towards such an approach are described.

METHODS

Neuro-evolutionary accounts of each of the anxiety disorders have been offered. Notably, several of these accounts have suggested that particular anxiety disorders are mediated by specific brain-based false alarms. This paper reviews the strengths and weaknesses of such accounts.

RESULTS

The false suffocation alarm of panic attack is the most fully elaborated of the neuro-evolutionary accounts of an anxiety disorder. However, viable neuro-evolutionary approaches have also been offered for other anxiety disorders, such as obsessive-compulsive disorder and social phobia.

CONCLUSIONS

Further work is necessary to consolidate a neuro-evolutionary approach to the anxiety disorders. Although the theoretical basis for such an approach has become increasingly appealing over the last several years, this foundation requires supplementation by further empirical research.

[Involvement of the basal ganglia in obsessive compulsive disorder: a review]

This article reviews the main clinical indicators linking the basal nuclei to obsessive compulsive disorder (OCD). Various pathologies associated with lesions of the basal nuclei are examined, followed by a review of neuropharmacological, brain imaging and psychosurgical studies. Once the role of the neostriatum in ritualistic behaviours has been clarified, the symptoms of OCD are interpreted based on the hypothesis of a lesion of the striato-orbito-frontal loop.

Social and emotional functions in facial expression and communication: the readout hypothesis

Fridlund (Fridlund, A.J. (1991). Biological Psychology, 32, 3-100) has argued that facial displays are specific to intent and context, rather than being readouts of underlying motivational-emotional states. This paper responds that these views are not incompatible, and that subjective emotional experience functions in part to enhance the learned control of emotional expression and communication. It summarizes the readout position, answers Fridlund's criticisms identifying it with the different notion of "spillover," and contends that the expressive readout functions in spontaneous communication. Fridlund's assertions that the readout is a reflex-like process, and that the readout view has ignored the receiver's coevolutionary role in communication, are addressed. Evidence supporting the readout view is presented, including studies suggesting that there are hierarchically organized neurochemical systems underlying subjective, expressive, and peripheral physiological responses. Such primary motivational-emotional systems (primes) are basic to the readout theory.

Axial motor disturbances after hypoxic lesions of the globus pallidus

Four subjects aged between 29 and 60 years were examined because of axial motor impairment after hypoxic brain injury. Magnetic resonance imaging revealed circumscribed lesions of the globus pallidus in every case. The association of freezing of the gait, speech disorders, axial bradykinesia, and postural disturbances, with no rigidity or tremor and little or no distal akinesia, suggests a role of the globus pallidus in controlling axial motion.

Cholinergic innervation of the human striatum, globus pallidus, subthalamic nucleus, substantia nigra, and red nucleus

The anatomical organization of cholinergic markers such as acetylcholinesterase, choline acetyltransferase, and nerve growth factor receptors was investigated in the basal ganglia of the human brain. The distribution of choline acetyltransferase-immunoreactive axons and varicosities and their relationship to regional perikarya showed that the caudate, putamen, nucleus accumbens, olfactory tubercle, globus pallidus, substantia nigra, red nucleus, and subthalamic nucleus of the human brain receive widespread cholinergic innervation. Components of the striatum (i.e., the putamen, caudate, olfactory tubercle, and nucleus accumbens) displayed the highest density of cholinergic varicosities. The next highest density of cholinergic innervation was detected in the red nucleus and subthalamic nucleus. The level of cholinergic innervation was of intermediate density in the globus pallidus and the ventral tegmental area and low in the pars compacta of the substantia nigra. Immunoreactivity for nerve growth factor receptors (NGFr) was confined to the cholinergic neurons of the basal forebrain and their processes. Axonal immunoreactivity for NGFr was therefore used as a marker for cholinergic projections originating from the basal forebrain (Woolf et al., '89: Neuroscience 30:143-152). Although the vast majority of striatal cholinergic innervation was NGFr-negative and, therefore, intrinsic, the striatum also contained NGFr-positive axons, indicating the existence of an additional cholinergic input from the basal forebrain. This basal forebrain cholinergic innervation was more pronounced in the putamen than in the caudate. The distribution of NGFr-positive axons suggested that the basal forebrain may also project to the globus pallidus but probably not to the subthalamic nucleus, substantia nigra, or red nucleus. The great majority of cholinergic innervation to these latter three structures and to parts of the globus pallidus appeared to come from cholinergic neurons outside the basal forebrain, most of which are probably located in the upper brainstem. These observations indicate that cholinergic neurotransmission originating from multiple sources is likely to play an important role in the diverse motor and behavioral affiliations that have been attributed to the human basal ganglia.

Accumbens-caudate-septal circuit as a system for hippocampal regulation: involvement of a GABAergic neurotransmission

Hippocampal-based epileptiform activity may reach the basal ganglia via the nucleus accumbens. Previous data suggested that caudate nucleus is able to influence hippocampal epilepsy, probably sending a projection to the septum. In order to test the hypothesis of a retrograde activation of accumbens-caudate pathway in hippocampal regulation, we electrically stimulated both caudate nucleus and nucleus accumbens and studied modifications of hippocampal EEG in the feline focal epilepsy model. We also performed bilateral electrolytic lesion of nucleus accumbens and repeated caudate stimulation. Results showed that nucleus accumbens stimulation was ineffective in modifying hippocampal epilepsy; on the contrary, caudate stimulation caused a statistically significant decrease of hippocampal spike frequency and amplitude. On the other hand, in accumbens-lesioned animals caudate activation consistently reduced hippocampal epilepsy to a significant degree. As the caudate nucleus influences hippocampal activity and the septum may constitute a relay station of this functional relation, a possibility was tested concerning a GABAergic mediation. To this end, after a stable caudate-induced effect was reached, an intraseptal microinjection of picrotoxin (GABA receptor antagonist) was made and caudate stimulation repeated at the same parameters. Such a study showed that after intraseptal picrotoxin, caudate stimulation failed to elicit any type of modification of hippocampal activity. Experimental findings support the notion that the striatal modulation on hippocampus is mediated by an anterograde rather than a retrograde pathway, and underline the possibility of a GABAergic caudate-septal influence.

Animal models of compulsive behavior

A convergence of clinical and pathological evidence points to the basal ganglia as the site of disturbance in compulsive disorders. However, the limbic system may be implicated as well. This article draws upon various lines of animal research in an attempt to explain how disturbances in one or another of these systems may produce compulsive behavior. Possible models include stimulation of the reinforcement mechanism, manipulation of the striatal "comparator" function, production and blockade of displacement behavior, and interference with the hippocampus' modulation of the stereotypy-inducing effect of reward. The common denominator of these models is a relative excess of dopaminergic activity in the basal ganglia. However, this does not necessarily implicate a primary dopaminergic disturbance in all human compulsive behavior.

CRH and alpha-helical-CRH modulate behavioral measures of arousal in monkeys

Several neuropeptides involved in the control of pituitary-adrenal activation have also been shown to have behavioral effects which may be mediated by actions on brain mechanisms independent of pituitary release. The behavioral effects of intraventricular administration of CRH and the synthetic peptide antagonist alpha-helical-CRH were assessed in socially separated squirrel monkeys. Treated monkeys were presented with a sequence of behavioral challenges including undisturbed social separation, presentation of a mirror image, and presentation of a "predator" stimulus. The test sequence was repeated at several time intervals after administration of the peptides. CRH produced dose-related increases in several species-typical measures of arousal including motor activity, vigilance-checking, and marking. Pretreatment with alpha-helical-CRH prevented the increased motor activity but not the marking behavior associated with CRH. When administered alone, alpha-helical-CRH increased vigilance-checking. In addition, alpha-helical-CRH increased aggressive behaviors exhibited at the mirror stimulus. The data provide further support for a central role for CRH in the mediation of both activational and inhibitory behavioral responses to stressful stimuli. These data also suggest both antagonistic and partial agonist effects for alpha-helical-CRH.

Striatal influence on ingestive behaviour in the cat

In freely moving cats with chronically implanted electrodes an analysis was made of the effects on feeding behaviour of low-frequency long-duration stimulation of the caudate nucleus, the substantia nigra and the globus pallidus. In all 3 structures a significant reduction of food intake was observed and in the pallidus this reached the point of a complete block of feeding. The effects were always limited to the period of stimulation. At the end of stimulation the animals recovered and took in food quantities equal to those of controls. The results are interpreted on the basis of reciprocal connections between the basal ganglia and the hypothalamus; the role of the striatum on the selection of certain movements and its possible involvement in behaviour is also discussed.

Reptilian behavioural patterns in childhood autism

Childhood autism may be caused by damage to three phylogenetically distinct regions of the brain, or their major pathways and connections. Injury to the neocortex results in loss of language and cognitive function, while injury to the limbic cortex results in autistic withdrawal and abolition of play behaviour. Injury to the more primitive striatal complex, mammalian counterpart of the brain of reptiles, results in a bizarre and truncated form of stereotyped and ritualistic behaviour. The causes of brain injury in childhood autism could be those common in the perinatal period including cerebral anoxia, haemorrhage, phenylketonuria, neurolipidoses , meningitis, toxoplasmosis, and congenital rubella. All these conditions have previously been shown to be associated with childhood autism.

Effects of tegmental lesions on the isolation call of squirrel monkeys

The present study is concerned with identifying brain mechanisms underlying a basic mammalian vocalization known as the isolation call. The call serves to reestablish contact of separated individuals. Adult squirrel monkeys were used as experimental subjects because the isolation call in these animals has been shown to be stable, well-defined, and readily elicited under experimental conditions. Bilateral, symmetrical electrocoagulations in certain parts of the tegmentum and core gray matter of the thalamus and midbrain variously altered the character and production of isolation calls, but had no apparent effect on other vocalizations. In respective cases the changes were characterized by: (1) reduction in number of calls; (2) calls with abnormal structure; and (3) calls of infantile character. As opposed to earlier investigations on mammals, the present study has shown that damage to certain brain structures may not only affect the production of a vocalization but also its physical characteristics.

Species-typical behavior of hamsters deprived from birth of the neocortex

Hamsters deprived from birth of the neocortex developed normally and displayed the usual hamster-typical behavioral patterns. With the additional concurrent destruction of midline limbic convolutions (cingulate and underlying dorsal hippocampal), there were deficits in maternal behavior and a lack of development of play behavior. These findings demonstrate in a rodent (i) that the striatal complex and limbic system, along with the remaining neuraxis, are sufficient for giving expression to a wide range of unlearned forms of species-typical behavior and (ii) that midline limbic structures are required for the expression of play behavior and the integrated performance of maternal behavior.

Nucleus accumbens to globus pallidus GABA projection: electrophysiological and iontophoretic investigations

Extracellular recordings were obtained from neurons in the nucleus accumbens and globus pallidus of urethane anesthetized rats. Eight neurons in the nucleus accumbens were activated antidromically following stimulation of the globus pallidus. Calculated conduction velocities were 0.4-1.5 m/sec, indicative of small unmyelinated fibers. A total of 74 of 153 neurons in the globus pallidus responded to stimulation of the nucleus accumbens. Of these neurons 4 (2.7%) were excited only, 46 (30.1%) were inhibited only and 24 (15.7%) had sequential effects to excitation and inhibition. Iontophoretic application of picrotoxin was found to attenuate or abolish the poststimulus inhibition in one-half of the neurons examined. The 74 neurons which responded to stimulation of the nucleus accumbens had slower firing frequencies and generally more random firing patterns than neurons which did not respond to stimulation. Fifty-three per cent of all globus pallidus neurons examined had increased spontaneous firing frequencies following the iontophoretic administration of picrotoxin alone. This is indicative of the removal of a tonic GABA input onto these neurons. Most neurons examined had decreased spontaneous firing frequencies following the iontophoretic application of GABA which could be blocked by the iontophoretic application of picrotoxin. The results from antidromic activation, slow conduction velocity, sensitivity to GABA and picrotoxin, and picrotoxin attenuation of the poststimulus inhibitory effect provide evidence of a direct GABAergic projection from the nucleus accumbens to the globus pallidus in the rat.

Role of the paleostriatum in species-typical display behavior of the lizard (Anolis carolinensis)

In a comparative study of forebrain mechanisms of species-typical behavior, unilateral lesions were placed in the subpallial telencephalon of male green anolis lizards (Anolis carolinsis), in which there is an almost complete decussation of the optic nerve. Responses to a conspecific male antagonist in a territorial confrontation were then tested when the subject's vision was limited to an eye leading to either the normal or lesioned hemisphere. In lizards with lesions involving the paleostriatum and lateral forebrain bundle, there was an elimination of or marked deficit in the performance of the challenge display while signature displays and measures of general activity were not significantly affected. Lesions predominantly in anterior or posterior dorsal ventricular ridge resulted in no significant deficit in any behavioral measure.