Telemetric recording of sleep and home cage activity in mice

STUDY OBJECTIVES: This study assessed differences in spontaneous sleep and locomotor activity in inbred and hybrid mouse strains and evaluated telemetry for recording sleep in mice. DESIGN: Uninterrupted recordings of sleep and home cage activity were obtained in four mouse strains. Pre-operative and post-operative home cage activity was obtained in two strains. SETTINGS: N/A PARTICIPANTS: The subjects were mice of three inbred (C57BL/6J (B6), n=25; BALB/cJ (C), n=24; DBA/2J (D2), n=30) strains and one hybrid (CB6F1/J (CB6: C x B6), n=19) strain. INTERVENTIONS: Electroencephalogram (EEG) and activity were recorded by telemetry, and behavioral states were visually scored based on EEG and activity records. Home cage activity was determined utilizing photobeam interruptions. MEASUREMENTS AND RESULTS: 1) Among the three inbred strains: C mice had the least sleep and the greatest amount of activity; D2 mice exhibited the least non-rapid-eye-movement (NREM) sleep, the longest average NREM-bout length, and the greatest diurnal ratio of sleep and were the most inactive; B6 mice had the most sleep and an intermediate activity level; no differences among inbred strains were observed in total REM. The CB6 mice exhibited intermediate levels of total sleep and activity and had greater amounts of REM compared to its parental strains. 2) Total operative mortality was 9.3%, with all deaths occurring within 3 to 9 days after the operation; significant reductions in activity were observed after the operation. CONCLUSION: Differences in spontaneous sleep and activity exist among inbred and hybrid mouse strains. Accurate determination of sleep states in mice can be achieved with telemetrically recorded EEG and activity.     

Changes in anxiety-related behaviors and hypothalamic-pituitary-adrenal activity in mice lacking the 5-HT-3A receptor

The serotonin-3 (5-HT-3A) receptor has been localized in limbic and brainstem structures that regulate anxiety-related behavior and hypothalamic-pituitary-adrenal (HPA) activity, but its role in regulating anxiety-related behaviors is equivocal, and evidence for its role in regulating HPA activity is limited. Therefore, we used 5-HT-3A receptor knockout (KO) mice to further study these issues. Behavior in the elevated plus maze, open field, light-dark box and after Pavlovian fear conditioning was examined in addition to HPA activity under basal and acute stress conditions. Compared to age-matched adult male wild-type (WT) controls, adult male KO mice exhibited increased distance traveled in the open arms of the elevated plus maze, consistent with decreased measures of anxiety. There were no differences between the two genotypes in exploratory behavior in the open field or light-dark test. KO mice displayed enhanced fear conditioning indexed by fear-induced freezing behavior. KO mice displayed lower adrenocorticotropin (ACTH) responses to restraint or lipopolysaccharide (LPS). In addition, lower vasopressin mRNA in the paraventricular nucleus of the hypothalamus (PVN) and higher corticotropin-releasing hormone (CRH) mRNA in the central amygdala were observed in KO compared to WT mice. Therefore, deletion of the 5-HT-3A receptor revealed an important role for this receptor in regulating HPA responses to acute stress and a potential interaction between the 5-HT-3A receptor and CRH in the amygdala. Together, these data suggest that the 5-HT-3A receptor does not have a unitary role in the regulation of anxiety- and fear-related behaviors but has a potentially substantial role in the regulation of HPA activity.     

Home cage activity and ingestive behaviors in mice following chronic ethanol vapor inhalation

Although drug withdrawal may induce an anxiety-like state, decreased locomotion in tests of anxiety-like behavior is an almost universal finding in rodent studies of ethanol withdrawal. Decreased locomotion in many behavioral apparatus, either as a result of a withdrawal-induced lethargy, malaise, or reduced motivation to explore confounds interpreting the effects of withdrawal as specifically increasing an anxiety-like state. To address this issue, we measured home cage activity levels as well as food and water intake for 3 days prior to and up to 5 days after chronic ethanol vapor exposure in genetically heterogeneous mice. In the first experiment, ethanol-withdrawing WSC-2 mice drank less water than controls, but did not differ from controls on any other behavioral measure during the withdrawal assessments. When the dose of ethanol was elevated in a subsequent experiment in WSC-2 mice, a similar temporary decrease in food and water intake, but not in locomotion, was observed during withdrawal. These results differed from those of mice placed into activity monitors during peak withdrawal, which exhibited profoundly reduced activity levels compared to controls. Finally, home cage activity levels during withdrawal were only transiently decreased in a mouse line that has been selectively bred to display high ethanol withdrawal handling-induced convulsion severity (WSP mice). The reduction in food and water consumption seen in most experiments suggests that withdrawal may induce a temporary malaise-like state, but this state is not reflected in altered home cage activity levels. Further, even in a relatively severe mouse model of alcohol withdrawal, any decreases in general home cage activity are short-lived.     

Effects of corticosterone synthesis inhibitor metyrapone on anxiety-related behaviors in Lurcher mutant mice

Beyond their motor impairments, the cerebellar Lurcher mutant mice show an alteration of the anxiety-related behaviors we called “behavioral disinhibition”. This is characterized by a low avoidance towards the open arms of the elevated plus-maze device paradoxically combined with a dramatic blood corticosterone level rise induced by the exposure to the experimental conditions. The present study was aimed at determining if the disinhibition of the mutants could be caused by their stress-induced high corticosterone rate. For this purpose, we compared the behaviors of Lurcher and control mice in the elevated plus-maze test after injection of either 2-methyl-1.2-di-3-pyridil-1-propanone (metyrapone; 75 mg/kg), a corticosterone synthesis inhibitor, or vehicle alone (Tween 80, 5%). Our results showed that metyrapone, although efficiently reducing their blood corticosterone rate, provoked only modest modifications of the anxiety-related behaviors in mice of both genotypes. As a result, the behavioral distance between the Lurcher and control mice slightly decreased, without being totally abolished. Thus, it seems that the behavioral disinhibition of the mutants is caused only in part by their stress-provoked high corticosterone level. As a complementary hypothesis, we propose that the behavioral disturbances observed in the Lurcher mice also might arise from dysfunctions of the neural pathways connecting the cerebellum with some limbic structures known to be highly involved in the regulation of emotions.     

The effects of stress on play and home cage behaviors in adolescent male rats

One prominent feature of adolescence is the high frequency of social behaviors, such as play. Engaging in these behaviors appears necessary for proper socio‐emotional development as social isolation during adolescence typically leads to behavioral dysfunctions in adulthood. The present experiments examined the effects of stress on social and nonsocial behaviors in group housed adolescent male rats. We found that acute restraint stress led to a complete inhibition of play (e.g., nape contacts and pins) and reduced social investigations in pre‐ (28 days), mid‐ (35 days), and late‐adolescent (42 and 49 days) animals. A follow‐up study, however, found that restraint‐induced suppression of play and social investigations was transient such that experimental animals engage in these behaviors at levels similar to those of controls 1 hr after termination of the stressor. We also found that exposure to repeated restraint stress throughout adolescence led to a decrease in social investigations, while leaving play largely unaffected. Interestingly, in all of the experiments, nonsocial behaviors (e.g., eating, drinking, grooming) were unaffected by restraint, suggesting these effects of stress are specific to social behaviors. Together, these data indicate that both acute and repeated stress significantly affect social behaviors during adolescence. © 2009 Wiley Periodicals, Inc. Dev Psychobiol 52: 62–70, 2010     

The role of motor learning and cage size in the early enrichment effect in mice

Three experiments with C57BL/10J mice examined the possible roles of cage size and simple motor practice as factors responsible for producing improved performance of animals reared in enriched environments. Neither factor was found sufficient to improve subsequent performance in a food-seeking task. Mice reared in flat environments containing a variety of objects, but designed to prevent any climbing practice, out-performed nonenriched animals on a task requiring extensive climbing activity.     

Differential effects of local inactivation within motor cortex and red nucleus on performance of an elbow task in the cat

This study examined changes in the performance of a single-joint, elbow task produced by reversible inactivation of local regions within the proximal forelimb representation in area 4 of motor cortex (MCx) and the red nucleus (RN) of the cat. Inactivation was carried out by microinjecting lidocaine, -aminobutyric acid, or muscimol into sites where microstimulation evoked contraction of elbow muscles. Reaction time, amplitude, and speed (velocity or dF/dt) of position and force responses elicited during inactivation were compared to control values obtained immediately prior to inactivation. In addition, we assessed qualitatively the effects of inactivation on reaching, placing reactions, and proprioceptive responses to imposed limb displacement. In the single-joint task, injections in MCx did not increase reaction time (simple or choice) and produced modest and inconsistent reductions in response amplitude (mean-8%) and speed (mean -19%). In contrast, injections of the same amounts of inactivating agents in the forelimb representation of RN consistently increased reaction time (34.4%), and increased the reaction time coefficient of variability (32%). There were small reductions in response amplitude (-4%) and speed (-10%) which were less than those produced by MCx inactivation. During reaching, however, these same injections in MCx and RN produced a substantial loss of accuracy. For MCx, this was due, in part, to systematic hypometria: for RN, inaccuracy resulted from increased variability in paw paths. Placing reactions and corrective responses to imposed limb displacements were also depressed by the cortical and rubral injections. Our results suggest that the forelimb representation in RN plays a role in the initiation of the single-joint, elbow tracking response examined here. The RN may mediate cerebellar regulation of response timing, a function that is likely to be important for interjoint coordination. Although neurons in the forelimb representations of MCx may contribute to force generation in single-joint movements, their contribution to multijoint control appears to be more important and is examined in the subsequent report (Martin and Ghez 1993).     

Haploinsufficiency of Dyrk1A in mice leads to specific alterations in the development and regulation of motor activity

DYRK1A is a protein kinase proposed to be involved in neurogenesis. Gene-targeting disruption of Dyrk1A in mice leads to decreased body and brain size, with no severe disturbance of behavior. In this study, the authors focused on the motor profile of Dyrk1A(+/-) mice. These mice presented impairment of neuromotor development with decreased activity, suggesting a physiological role of Dyrk1A in the maturation of the neuromotor system. In the adult, a marked hypoactivity and alteration of specific motor parameters were detected. These results are in agreement with the significant expression of Dyrk1A in structures related to motor function and support a role of Dyrk1A in the control of motor function.     

Analysis of automated quantification of motor activity in REM sleep behaviour disorder

Rapid eye movement (REM) sleep behaviour disorder (RBD) is characterized by dream enactment and REM sleep without atonia. Atonia is evaluated on the basis of visual criteria, but there is a need for more objective, quantitative measurements. We aimed to define and optimize a method for establishing baseline and all other parameters in automatic quantifying submental motor activity during REM sleep. We analysed the electromyographic activity of the submental muscle in polysomnographs of 29 patients with idiopathic RBD (iRBD), 29 controls and 43 Parkinson's (PD) patients. Six adjustable parameters for motor activity were defined. Motor activity was detected and quantified automatically. The optimal parameters for separating RBD patients from controls were investigated by identifying the greatest area under the receiver operating curve from a total of 648 possible combinations. The optimal parameters were validated on PD patients. Automatic baseline estimation improved characterization of atonia during REM sleep, as it eliminates inter/intra‐observer variability and can be standardized across diagnostic centres. We found an optimized method for quantifying motor activity during REM sleep. The method was stable and can be used to differentiate RBD from controls and to quantify motor activity during REM sleep in patients with neurodegeneration. No control had more than 30% of REM sleep with increased motor activity; patients with known RBD had as low activity as 4.5%. We developed and applied a sensitive, quantitative, automatic algorithm to evaluate loss of atonia in RBD patients.     

Cortical excitability and motor task in man: an investigation of the wrist extensor motor area

Task-related changes in the corticospinal excitation of the right extensor carpi radialis (ECR) muscle were investigated in 16 healthy human subjects. The subjects were asked to perform a tonic isometric wrist extension or to clench their hand around a manipulandum, thereby coactivating the antagonistic wrist muscles. At matched levels of background EMG in the ECR muscle, transcranial magnetic stimulation (TMS) was applied through a figure-of-eight coil at 20-30 sites spaced 1 cm apart over the hand area of the left motor cortex. The cortical maps of the representation of the ECR muscle constructed in this way did not change between the two motor tasks. Nevertheless, for all investigated cortical sites TMS evoked a smaller motor evoked potential (MEP) in the ECR muscles during hand clenching than during wrist extension. A similar decrease in the short-latency peak in the poststimulus time histogram (PSTH) of single ECR motor units to TMS during hand clenching was found in seven subjects (number of motor units = 35). In contrast, short-latency peaks in the PSTH evoked by electrical stimulation of the motor cortex had a similar size during the two tasks (number of motor units = 9; two subjects). Already the initial 0.5-1.0 ms of the short-latency peak evoked by TMS was depressed during hand clenching, which suggests that decreased excitability of corticospinal cells with monosynaptic projections onto ECR motor units was involved. This decreased excitability was not explained by increased intracortical inhibition, which was found to be of a similar size during hand clenching and wrist extension. The task-related changes in the efficiency of the motor cortex output are discussed in relation to the function of the wrist antagonist muscles in handling and gripping tasks.     

Cortical activity of skilled performance in a complex sports related motor task

A skilled player in goal-directed sports performance has the ability to process internal and external information in an effective manner and decide which pieces of information are important and which are irrelevant. Focused attention and somatosensory information processing play a crucial role in this process. Electroencephalographic (EEG) recordings are able to demonstrate cortical changes in conjunction with this concept and were examined during a golf putting performance in an expert-novice paradigm. The success in putting (score) and performance-related cortical activity were recorded with an EEG during a 5 × 4 min putting series. Subjects were asked to putt balls for four min at their own pace. The EEG data was divided into different frequencies: Theta (4.75–6.75 Hz), Alpha-1 (7–9.5 Hz), Alpha-2 (9.75–12.5 Hz) and Beta-1 (12.75–18.5 Hz) and performance related power values were calculated. Statistical analysis shows significant better performance in the expert golfers (P < 0.001). This was associated with higher fronto-midline Theta power (P < 0.05) and higher parietal Alpha-2 power values (P < 0.05) compared to the novices in golf putting. Frontal Theta and parietal Alpha-2 spectral power in the ongoing EEG demonstrate differences due to skill level. Furthermore the findings suggest that with increasing skill level, golfers have developed task solving strategies including focussed attention and an economy in parietal sensory information processing which lead to more successful performance. In a theoretical framework both cortical parameters may play a role in the concept of the working memory.     

Impairment of N-methyl-D-aspartate receptor-controlled motor activity in LYN-deficient mice

The N-methyl-D-aspartate (NMDA) receptor, an ionotropic glutamate receptor, is implicated in motor activity that is regulated in the striatum and nucleus accumbens of the brain. A Src family kinase Lyn is highly expressed in striatum, cortex, thalamus, and cerebellum in the brain. Here we show that spontaneous motor activity is suppressed in lyn-/- mice. S.c. injection of methylphenidate, which causes accumulation of dopamine in synapses, reveals that dopaminergic pathway is normal in lyn-/- mice. After blocking the NMDA receptor, motor activity of lyn-/- mice increased to the same level as that of wild type mice. Therefore, the NMDA receptor-mediated signaling is enhanced in lyn-/- mice, indicating that Lyn regulates the NMDA receptor pathway negatively. Intriguingly, the activity of protein kinase C (PKC), an enzyme regulated downstream of NMDA receptors, is increased in lyn-/- mice. The present data suggest that the NMDA receptor signal that is enhanced in the absence of Lyn suppresses the motor activity, probably through inhibition of dopaminergic pathway at striatum.We conclude that Lyn contributes to coordination of motor activity through regulation of the NMDA pathway. It appears that this negative regulation involves suppression of downstream signaling of NMDA receptor such as those mediated by PKC.     

There's no place like home: cage odours and place preference in subordinate CD-1 male mice

Prior studies using mice have shown that scent marks are an important source of information and can cause behavioural changes in other individuals. Studies have also shown that scent marks in the environment can affect the outcome of social interactions between mice. We used conditioned place preference tests to investigate whether CD-1 male mice (Mus musculus) are reinforced by olfactory cues from the home cage. Soiled bedding from the home cage was presented in the initially less preferred chamber of the apparatus to determine whether this association would reduce the unconditioned preference for one chamber over the other. We tested the effects of social rank and housing condition by comparing the performance of dyads that were polarised into dominant and subordinate relationships, both when paired and when separated, with mice that were isolated throughout. The development of conditioned place preference (CPP) supported by home cage odours was influenced by social rank but not by housing condition. Only subordinate mice showed CPP to home cage odours, and this effect was seen irrespective of whether they were housed with a dominant cage mate or alone. Neither dominant (paired or separated) nor isolated mice showed any change in their preference for the chamber associated with home cage odours. This suggests that the smell of home is a more powerful reinforcer for subordinate mice in that it can produce contextual conditioning to the environment in which it is experienced.     

Differential regulation of antigen presentation in high- and low-IgE responder mice.

Strains of mice differ greatly in their capacity to produce interleukin (IL) 4 and high levels of serum IgE. The contribution of macrophages (M phi) in enhancing the production of IL4 by T cells in high-IgE responder mice was studied. M phi from BALB/c mice (high-IgE responder strain) developed an augmented capacity to present antigen to IL 4-producing T helper type 2 (Th2) clones, when the M phi were pretreated by exposure to the lymphokines IL 4 and IL 5. In contrast, identical treatment of M phi from H-2-identical DBA/2 mice (low-IgE responder strain) resulted in inhibition of the capacity to stimulate Th2 clones. The impairment of antigen presentation by DBA/2 M phi was closely paralleled by a decrease of cell surface class II major histocompatibility complex (MHC) expression and an abrogation of IL 1 production by these cells, while identical treatment of BALB/c M phi enhanced class II MHC expression and did not inhibit secretion of IL 1. Our studies demonstrate that IL 4 and IL 5 can exert different effects on M phi from high- and low-IgE responder strains of mice, resulting in down-regulation of the expansion of IL 4-producing cells in low-but not high-IgE responder mice.     

Differential regulation of cytokine production in lipopolysaccharide tolerance in mice.

We investigated the pattern of down-regulation of cytokine production in endotoxin (lipopolysaccharide [LPS]) tolerance. A 4-day treatment with LPS (35 micrograms per mouse) was followed by a challenge on day 6 with one more injection of LPS. Circulating tumor necrosis factor (TNF) and interleukin-6 (IL-6) could not be induced (> 99% inhibition) by LPS in LPS-tolerant mice; colony-stimulating factor (CSF) was also down-regulated by more than 95%, whereas interferon (IFN) and IL-1 syntheses were only partially inhibited. To study the mechanism of cytokine down-regulation in tolerance, we attempted to reverse the tolerant state by pretreatment with phorbol 12-myristate 13-acetate (PMA) (4 micrograms per mouse) 10 min before the LPS challenge. PMA completely restored IL-6 production and partially that of CSF. PMA had no effect on IFN production and inhibited the induction of IL-1. TNF production was also not restored by PMA. To investigate the role of endogenously produced cytokines in the development of LPS tolerance, we administered IL-6, TNF, or IL-1 alpha, using the same treatment schedule as that for LPS. Whereas IL-6 had no effect, IL-1 alpha or TNF induced partial tolerance to LPS in terms of inhibition of LPS-stimulated TNF and IL-6 production. However, a full LPS-tolerant state could not be induced by administration of recombinant cytokines, suggesting the existence of additional mechanisms, such as a loss of LPS receptors or changes in release of soluble binding proteins.     

Characterization of torque-related activity in primary motor cortex during a multijoint postural task

The present study examined neural activity in the shoulder/elbow region of primary motor cortex (M1) during a whole-limb postural task. By selectively imposing torques at the shoulder, elbow, or both joints we addressed how neurons represent changes in torque at a single joint, multiple joints, and their interrelation. We observed that similar proportions of neurons reflected changes in torque at the shoulder, elbow, and both joints and these neurons were highly intermingled across the cortical surface. Most torque-related neurons were reciprocally excited and inhibited (relative to their unloaded baseline activity) by opposing flexor and extensor torques at a single joint. Although coexcitation/coinhibition was occasionally observed at a single joint, it was rarely observed at both joints. A second analysis assessed the relationship between single-joint and multijoint activity. In contrast to our previous observations, we found that neither linear nor vector summation of single-joint activities could capture the breadth of neural responses to multijoint torques. Finally, we studied the neurons' directional tuning across all the torque conditions, i.e., in joint-torque space. Our population of M1 neurons exhibited a strong bimodal distribution of preferred-torque directions (PTDs) that was biased toward shoulder-extensor/elbow-flexor (whole-limb flexor) and shoulder-flexor/elbow-extensor (whole-limb extensor) torques. Notably, we recently observed a similar bimodal distribution of PTDs in a sample of proximal arm muscles. This observation illustrates the intimate relationship between M1 and the motor periphery.     

Evaluation of exploration and risk assessment in pre-weaning mice using the novel cage test

Exploration and risk behaviour (risk assessment/risk taking) are critical to enable mice to cope with novel situations and gain control over their environment. Evaluation of those behaviours would therefore be a useful part of early phenotypic characterization of genetically modified mice, allowing early detection of behavioural phenotypes that require special attention and/or are of scientific interest. This study aimed to evaluate exploration and risk behaviour in pre-weaning mice using the novel cage test, which consists in exploration of a novel, clean, Makrolon type III cage. The results of this test were compared with those obtained in more complex and established tests to which the same mice were subjected as adolescents and young adults. Mice of two inbred strains (129S6/Bkl, n=10; C57BL/6Bkl, n=10) and one hybrid (B6CBAF1/Bkl, n=10) were used for validation of the test. The animals were tested in the novel cage (at weaning), the open field test (at 5 weeks), and from 9 weeks of age in three other tests: the elevated plus-maze, the concentric square field and the rat exposure test. The novel cage test effectively detected strain differences in pre-weaning mice as regards exploration and risk behaviour and the results were largely consistent with those obtained in the established tests later in life. In all tests 129S6 displayed a low locomotion and high risk assessment, while C57BL/6 and B6CBAF1 showed high locomotion and exploration. In addition high levels of risk taking were observed in C57BL/6. The novel cage test is rapid, requires no special equipment and is as discriminatory as more complex tests in detecting strain/genotype differences. This suggests that the novel cage test is a valuable tool for evaluation of exploration, risk assessment and risk taking in juvenile mice.     

Supplementary motor area in the monkey: activity of neurons during performance of a learned motor task.

1. Recordings were made of the natural discharges of neurons in the supplementary motor area (SMA) of conscious monkeys trained to perform stereotyped motor task, pulling a horizontal lever, with either hand. 2. Of the total population of cells, 80% showed modulation of their activity during particular movements of either limb. Many cells had a similar pattern of modulation regardless of whether the contralateral or ipsilateral hand was used. Of the remaining 20%, some cells were related to leg or body movements or to visual experience. 3. Cells whose activity was related to movements of distal joints were found in approximately equal numbers to those whose discharges occurred with proximal movements. 4. Only 5% of cells tested sent their axons into the pyramidal tract, and only 14% of units investigated showed responses to passive manipulation of the limbs. The effective afferent input usually was of a rather complex kind. 5. The findings suggest that the discharges of a large number of neurons in SMA are changing during particular movements of either arm, and that only a small number of cells receive peripheral afferent sensory input. These results contrast with those obtained in the primary motor area and suggest a different role for SMA in the control of movement.     

Consummatory behaviors and weight regulation in pregnant, lactating, and pregnant-lactating mice.

Pregnant Rockland-Swiss (R-S) albino mice consumed significantly more food and water and gained significantly more weight between gestation days 8-17 compared to virgin R-S females maintained in isolation for a comparable period. Postpartum (days 1-10) patterns of ingestion and weight change among thelectomized (nipple-deprived) mouse dams provided with young did not differ significantly from those of virgin animals without young. Sham- and nonoperated dams received suckling stimulation from young and consumed about 100% more food than thelectomized or virgin females (Experiment 1). Pregnancy concurrent with lactation does not increase further the hyperphagic response of female mice. Nipple presence is the principle regulator of postpartum hyperphagia in lactating and simultaneously pregnant-lactating mouse dams (Experiment 2).     

Bimodal effect of amphetamine on motor behaviors in C57BL/6 mice

Amphetamine-induced motor behaviors, i.e., locomotor and stereotypic activities, were simultaneously characterized in C57BL/6 mice, a strain commonly used for genetic studies. Our findings show relatively high levels of focused activities in drug-naive C57BL/6 mice, confirming the lively nature of this mouse strain. Acute amphetamine induced a dose-dependent, bimodal response: locomotion predominated at lower doses of amphetamine and was gradually displaced by stereotypic behavior as dose and time increased. The sum total of both behavioral activities increased with amphetamine dose, supporting the notion that amphetamine-induced locomotion and stereotypy form a continuum. These data provide a basis for using C57BL/6 mice as a strain to study the molecular and cellular mechanisms underlying psychostimulant effects, drug addiction and psychotic disorders.