Broca’s aphasia is also known as non-fluent aphasia, while Wernicke’s aphasia is referred to as fluent aphasia.

Broca’s and Wernicke’s are two types of expressive dysphasia, which is characterized by difficulty producing speech despite intact comprehension. Dysarthria is a type of expressive dysphasia caused by damage to the speech production apparatus, while Broca’s aphasia is caused by damage to the area of the brain responsible for speech production, specifically Broca’s area located in Brodmann areas 44 and 45. On the other hand, Wernicke’s aphasia is a type of receptive of fluent aphasia caused by damage to the comprehension of speech, while the actual production of speech remains normal. Wernicke’s area is located in the posterior part of the superior temporal gyrus in the dominant hemisphere, within Brodmann area 22.

Genes Associated with Dementia

Dementia is a complex disorder that can be caused by various genetic and environmental factors. Several genes have been implicated in different forms of dementia. For instance, familial Alzheimer’s disease, which represents less than 1-6% of all Alzheimer’s cases, is associated with mutations in PSEN1, PSEN2, APP, and ApoE genes. These mutations are inherited in an autosomal dominant pattern. On the other hand, late-onset Alzheimer’s disease is a genetic risk factor associated with the ApoE gene, particularly the APOE4 allele. However, inheriting this allele does not necessarily mean that a person will develop Alzheimer’s.

Other forms of dementia, such as familial frontotemporal dementia, Huntington’s disease, CADASIL, and dementia with Lewy bodies, are also associated with specific genes. For example, C9orf72 is the most common mutation associated with familial frontotemporal dementia, while Huntington’s disease is caused by mutations in the HTT gene. CADASIL is associated with mutations in the Notch3 gene, while dementia with Lewy bodies is associated with the APOE, GBA, and SNCA genes.

In summary, understanding the genetic basis of dementia is crucial for developing effective treatments and preventive measures. However, it is important to note that genetics is only one of the many factors that contribute to the development of dementia. Environmental factors, lifestyle choices, and other health conditions also play a significant role.

Piaget’s theory of cognitive development highlights that Preoperational children are egocentric, meaning they view the world solely from their own perspective and cannot comprehend that others may have different viewpoints. Piaget believed that cognitive development is a result of the interplay between innate abilities and environmental factors, and progresses through four distinct stages: the sensorimotor stage, Preoperational stage, concrete operational stage, and formal operational stage. While Piaget’s theory has greatly contributed to our understanding of cognitive development, it has also faced criticism over time. Other notable theories in this field include Vygotsky’s theory, Bruner’s theory, and the information-processing approach. Vygotsky’s theory, for instance, examines human development across three levels: cultural, interpersonal, and individual.

Mannerisms are deliberate movements that convey a specific meaning, while tics are involuntary muscle contractions that disrupt normal activities and are often preceded by a strong urge. Hemiballismus refers to uncontrolled flinging movements of one arm and leg, while chorea involves irregular, jerky, and unpredictable movements that can occur anywhere in the body. Athetosis describes writhing movements, particularly in the arms and hands, and is often associated with cerebral palsy resulting from perinatal anoxia of kernicterus. Infants with athetosis may exhibit delayed motor milestones and floppy movements before developing athetoid movements before the age of 5.

A delta and C fibers use glutamate as their primary neurotransmitter where it acts as a fast acting localized neurotransmitter.

In 1960, psychiatrist R D (Ronald David) Laing, a Scottish author, published ‘The Divided Self’, which made him a significant figure in the antipsychiatry movement. Despite acknowledging the importance of treating mental distress, he believed that ‘schizophrenia was a theory, not a fact.’ Other notable authors in the field of psychiatry include Anthony Clare, who wrote ‘Psychiatry in Dissent,’ Carl Jung, who wrote ‘The Red Book,’ Scott Peck, who wrote ‘The Road Less Travelled,’ and Thomas Szasz, who wrote ‘The Myth of Mental Illness.

Huntington’s Disease: Genetics and Pathology

Huntington’s disease is a genetic disorder that follows an autosomal dominant pattern of inheritance. It is caused by a mutation in the Huntington gene, which is located on chromosome 4. The mutation involves an abnormal expansion of a trinucleotide repeat sequence (CAG), which leads to the production of a toxic protein that damages brain cells.

The severity of the disease and the age of onset are related to the number of CAG repeats. Normally, the CAG sequence is repeated less than 27 times, but in Huntington’s disease, it is repeated many more times. The disease shows anticipation, meaning that it tends to worsen with each successive generation.

The symptoms of Huntington’s disease typically begin in the third of fourth decade of life, but in rare cases, they can appear in childhood of adolescence. The most common symptoms include involuntary movements (chorea), cognitive decline, and psychiatric disturbances.

The pathological hallmark of Huntington’s disease is the gross bilateral atrophy of the head of the caudate and putamen, which are regions of the brain involved in movement control. The EEG of patients with Huntington’s disease shows a flattened trace, indicating a loss of brain activity.

Macroscopic pathological findings include frontal atrophy, marked atrophy of the caudate and putamen, and enlarged ventricles. Microscopic findings include neuronal loss and gliosis in the cortex, neuronal loss in the striatum, and the presence of inclusion bodies in the neurons of the cortex and striatum.

In conclusion, Huntington’s disease is a devastating genetic disorder that affects the brain and causes a range of motor, cognitive, and psychiatric symptoms. The disease is caused by a mutation in the Huntington gene, which leads to the production of a toxic protein that damages brain cells. The pathological changes in the brain include atrophy of the caudate and putamen, neuronal loss, and the presence of inclusion bodies.

When a patient’s mania becomes intractable and is accompanied by severe depression and catatonia, electroconvulsive therapy (ECT) may be necessary. Despite being treated with a combination of mood stabilizers, antipsychotic medication, and a short-acting benzodiazepine, this patient has not responded to treatment and has deteriorated to the point of requiring seclusion. This suggests that the mania is treatment-resistant and requires ECT.

Under section 58a of the Mental Health Act, there are safeguards in place to ensure that the patient’s capacity and consent are assessed before administering ECT. However, in cases where immediate action is necessary to prevent death of serious deterioration in mental health, ECT can be given without the patient’s consent under Section 62. In this case, the patient will receive ECT while awaiting a SOAD.

Citalopram can moderately prolong QTc (>10 msec), while aripiprazole and paliperidone have no effect. Haloperidol and pimozide have a high effect, and quetiapine and amisulpride have a moderate effect. Clozapine, risperidone, and olanzapine have a low effect (<10 msec prolongation). Lamotrigine, mirtazapine, and SSRIs (excluding citalopram) do not have an effect on QTc interval.

Anabolic Steroids: Uses, Misuse, and Complications

Anabolic steroids are synthetic derivatives of testosterone that have both anabolic and androgenic properties. They are commonly used by athletes to enhance performance and by individuals to improve physical appearance. However, their misuse is not uncommon, with nearly half of users of dedicated bodybuilding gyms admitting to taking anabolic agents. Misuse can lead to dependence, tolerance, and the development of psychiatric disorders such as aggression, psychosis, mania, and depression/anxiety.

There are three common regimes practised by steroid misusers: ‘cycling’, ‘stacking’ and ‘pyramiding’. Anabolic steroids can be taken orally, injected intramuscularly, and applied topically in the form of creams and gels. Other drugs are also used by athletes, such as clenbuterol, ephedrine, thyroxine, insulin, tamoxifen, human chorionic Gonadotropin, diuretics, and growth hormone.

Medical complications are common and can affect various systems, such as the musculoskeletal, cardiovascular, hepatic, reproductive (males and females), dermatological, and other systems. Complications include muscular hypertrophy, increased blood pressure, decreased high-density lipoprotein cholesterol and increased low-density lipoprotein cholesterol, cholestatic jaundice, benign and malignant liver tumours, testicular atrophy, sterility, gynaecomastia, breast tissue shrinkage, menstrual abnormalities, masculinisation, male-pattern baldness, acne, sleep apnoea, exacerbation of tic disorders, polycythaemia, altered immunity, and glucose intolerance.

Anabolic steroids are a class C controlled drug and can only be obtained legally through a medical prescription. It is important to educate individuals about the risks and complications associated with their misuse and to promote safe and legal use.

Assessing Executive Function with the Hayling and Brixton Tests

The Hayling and Brixton tests are two assessments designed to evaluate executive function. The Hayling Sentence Completion Test consists of two sets of 15 sentences, with the last word missing. In the first section, participants complete the sentences, providing a measure of response initiation speed. The second part, the Hayling, requires participants to complete a sentence with a nonsense ending word, suppressing a sensible one. This provides measures of response suppression ability and thinking time. Performance on such tests has been linked to frontal lobe dysfunction and dysexecutive symptoms in everyday life.

The Brixton Test is a rule detection and rule following task. Impairments on such tasks are commonly demonstrated in individuals with dysexecutive problems. Overall, these tests provide valuable insights into executive function and can help identify areas of weakness that may require intervention.

The PANSS scale is a commonly utilized tool in schizophrenia research to assess both positive and negative symptoms. The BDI measures depression using the Beck inventory, while the Calgary scale is specifically designed to rate depression in individuals with schizophrenia. CIWA is a scale used to evaluate the severity of alcohol withdrawal, and LUNSER is a rating scale for neuroleptic side effects developed by Liverpool University.

Extrapyramidal side-effects (EPSE’s) are a group of side effects that affect voluntary motor control, commonly seen in patients taking antipsychotic drugs. EPSE’s include dystonias, parkinsonism, akathisia, and tardive dyskinesia. They can be frightening and uncomfortable, leading to problems with non-compliance and can even be life-threatening in the case of laryngeal dystonia. EPSE’s are thought to be due to antagonism of dopaminergic D2 receptors in the basal ganglia. Symptoms generally occur within the first few days of treatment, with dystonias appearing quickly, within a few hours of administration of the first dose. Newer antipsychotics tend to produce less EPSE’s, with clozapine carrying the lowest risk and haloperidol carrying the highest risk. Akathisia is the most resistant EPSE to treat. EPSE’s can also occur when antipsychotics are discontinued (withdrawal dystonia).

It is important to be aware of the half-lives of certain benzodiazepines, including diazepam with a half-life of 20-100 hours (36-200 hours for active metabolite), lorazepam with a half-life of 10-20 hours, chlordiazepoxide with a half-life of 5-30 hours (36-200 hours for active metabolite), nitrazepam with a half-life of 15-38 hours, temazepam with a half-life of 8-22 hours, zopiclone with a half-life of 4-6 hours, and zolpidem with a half-life of 2-6 hours.

The half-life of a drug is the time taken for its concentration to fall to one half of its value. Drugs with long half-lives may require a loading dose to achieve therapeutic plasma concentrations rapidly. It takes about 4.5 half-lives to reach steady state plasma levels. Most drugs follow first order kinetics, where a constant fraction of the drug in the body is eliminated per unit time. However, some drugs may follow zero order kinetics, where the plasma concentration of the drug decreases at a constant rate, despite the concentration of the drug. For drugs with nonlinear kinetics of dose-dependent kinetics, the relationship between the AUC of CSS and dose is not linear, and the kinetic parameters may vary depending on the administered dose.

Transitional objects were conceptualized by Winnicott as items that infants between 4-18 months of age select to aid in their separation and individuation process. These objects, such as a soft toy of blanket, serve as a source of comfort and help reduce anxiety. Object relations theory was also supported by Balint and Fairbairn. Meanwhile, Kleinian theory placed significant emphasis on the interpretation of play.

Aneuploidy: Abnormal Chromosome Numbers

Aneuploidy refers to the presence of an abnormal number of chromosomes, which can result from errors during meiosis. Typically, human cells have 23 pairs of chromosomes, but aneuploidy can lead to extra of missing chromosomes. Trisomies, which involve the presence of an additional chromosome, are the most common aneuploidies in humans. However, most trisomies are not compatible with life, and only trisomy 21 (Down’s syndrome), trisomy 18 (Edwards syndrome), and trisomy 13 (Patau syndrome) survive to birth. Aneuploidy can result in imbalances in gene expression, which can lead to a range of symptoms and developmental issues.

Compared to autosomal trisomies, humans are more able to tolerate extra sex chromosomes. Klinefelter’s syndrome, which involves the presence of an extra X chromosome, is the most common sex chromosome aneuploidy. Individuals with Klinefelter’s and XYY often remain undiagnosed, but they may experience reduced sexual development and fertility. Monosomies, which involve the loss of a chromosome, are rare in humans. The only viable human monosomy involves the X chromosome and results in Turner’s syndrome. Turner’s females display a wide range of symptoms, including infertility and impaired sexual development.

The frequency and severity of aneuploidies vary widely. Down’s syndrome is the most common viable autosomal trisomy, affecting 1 in 800 births. Klinefelter’s syndrome affects 1-2 in 1000 male births, while XYY syndrome affects 1 in 1000 male births and Triple X syndrome affects 1 in 1000 births. Turner syndrome is less common, affecting 1 in 5000 female births. Edwards syndrome and Patau syndrome are rare, affecting 1 in 6000 and 1 in 10,000 births, respectively. Understanding the genetic basis and consequences of aneuploidy is important for diagnosis, treatment, and genetic counseling.

Box and whisker plots are a useful tool for displaying information about the range, median, and quartiles of a data set. The whiskers only contain values within 1.5 times the interquartile range (IQR), and any values outside of this range are considered outliers and displayed as dots. The IQR is the difference between the 3rd and 1st quartiles, which divide the data set into quarters. Quartiles can also be used to determine the percentage of observations that fall below a certain value. However, quartiles and ranges have limitations because they do not take into account every score in a data set. To get a more representative idea of spread, measures such as variance and standard deviation are needed. Box plots can also provide information about the shape of a data set, such as whether it is skewed or symmetric. Notched boxes on the plot represent the confidence intervals of the median values.

Delusional perception is a symptom of schizophrenia where a person interprets normal sensory experiences with a delusional meaning. Other first rank symptoms of schizophrenia include delusions, auditory hallucinations, thought disorders, and passivity experiences. Delusional awareness is when ideas seem more real, while delusional intuition is a sudden onset of delusional beliefs. Delusional mood is a feeling of unease and confusion where the environment seems threatening but the reason is unclear to the person experiencing it.

Hirano bodies are a nonspecific indication of neurodegeneration and are primarily observed in.

Alzheimer’s disease is characterized by both macroscopic and microscopic changes in the brain. Macroscopic changes include cortical atrophy, ventricular dilation, and depigmentation of the locus coeruleus. Microscopic changes include the presence of senile plaques, neurofibrillary tangles, gliosis, degeneration of the nucleus of Meynert, and Hirano bodies. Senile plaques are extracellular deposits of beta amyloid in the gray matter of the brain, while neurofibrillary tangles are intracellular inclusion bodies that consist primarily of hyperphosphorylated tau. Gliosis is marked by increases in activated microglia and reactive astrocytes near the sites of amyloid plaques. The nucleus of Meynert degenerates in Alzheimer’s, resulting in a decrease in acetylcholine in the brain. Hirano bodies are actin-rich, eosinophilic intracytoplasmic inclusions which have a highly characteristic crystalloid fine structure and are regarded as a nonspecific manifestation of neuronal degeneration. These changes in the brain contribute to the cognitive decline and memory loss seen in Alzheimer’s disease.

Patients who develop TD who are prescribed an anticholinergic drug should not have this discontinued if possible.

Extrapyramidal side-effects (EPSE’s) are a group of side effects that affect voluntary motor control, commonly seen in patients taking antipsychotic drugs. EPSE’s include dystonias, parkinsonism, akathisia, and tardive dyskinesia. They can be frightening and uncomfortable, leading to problems with non-compliance and can even be life-threatening in the case of laryngeal dystonia. EPSE’s are thought to be due to antagonism of dopaminergic D2 receptors in the basal ganglia. Symptoms generally occur within the first few days of treatment, with dystonias appearing quickly, within a few hours of administration of the first dose. Newer antipsychotics tend to produce less EPSE’s, with clozapine carrying the lowest risk and haloperidol carrying the highest risk. Akathisia is the most resistant EPSE to treat. EPSE’s can also occur when antipsychotics are discontinued (withdrawal dystonia).

Antidepressants and Their Cardiac Effects

SSRIs are generally recommended for patients with cardiac disease as they may protect against myocardial infarction (MI). Untreated depression worsens prognosis in cardiovascular disease. Post MI, SSRIs and mirtazapine have either a neutral of beneficial effect on mortality. Sertraline is recommended post MI, but other SSRIs and mirtazapine are also likely to be safe. However, citalopram is associated with Torsades de pointes (mainly in overdose). Bupropion, citalopram, escitalopram, moclobemide, lofepramine, and venlafaxine should be used with caution of avoided in those at risk of serious arrhythmia (those with heart failure, left ventricular hypertrophy, previous arrhythmia, of MI).

Tricyclic antidepressants (TCAs) have established arrhythmogenic activity which arises as a result of potent blockade of cardiac sodium channels and variable activity at potassium channels. ECG changes produced include PR, QRS, and QT prolongation and the Brugada syndrome. Lofepramine is less cardiotoxic than other TCAs and seems to lack the overdose arrhythmogenicity of other TCAs. QT changes are not usually seen at normal clinical doses of antidepressants (but can occur, particularly with citalopram/escitalopram). The arrhythmogenic potential of TCAs and other antidepressants is dose-related.

Overall, SSRIs are recommended for patients with cardiac disease, while caution should be exercised when prescribing TCAs and other antidepressants, especially in those at risk of serious arrhythmia. It is important to monitor patients closely for any cardiac effects when prescribing antidepressants.

Henry Dale was the first to identify acetylcholine in 1915 through its effects on cardiac tissue, and he was awarded the Nobel Prize in Medicine in 1936 alongside Otto Loewi for their work. Arvid Carlsson discovered dopamine as a neurotransmitter in 1957, while von Euler discovered noradrenaline (also known as norepinephrine) as both a hormone and neurotransmitter in 1946. Oxytocin is typically classified as a hormone, while substance P is a neuropeptide that functions as both a neurotransmitter and neuromodulator and was first discovered in 1931.

Although iproniazid demonstrated an antidepressant effect in clinical trials involving tuberculosis patients, it has been largely discontinued due to its link to liver damage. However, isoniazid, which shares chemical similarities with iproniazid, is still utilized as a treatment for tuberculosis.

Mechanisms of Action of Different Drugs

Understanding the mechanisms of action of different drugs is crucial for medical professionals. It is a common topic in exams and can earn easy marks if studied well. This article provides a list of drugs and their mechanisms of action in different categories such as antidepressants, anti dementia drugs, mood stabilizers, anxiolytic/hypnotic drugs, antipsychotics, drugs of abuse, and other drugs. For example, mirtazapine is a noradrenaline and serotonin specific antidepressant that works as a 5HT2 antagonist, 5HT3 antagonist, H1 antagonist, alpha 1 and alpha 2 antagonist, and moderate muscarinic antagonist. Similarly, donepezil is a reversible acetylcholinesterase inhibitor used as an anti dementia drug, while valproate is a GABA agonist and NMDA antagonist used as a mood stabilizer. The article also explains the mechanisms of action of drugs such as ketamine, phencyclidine, buprenorphine, naloxone, atomoxetine, varenicline, disulfiram, acamprosate, and sildenafil.

Neurotransmitters are substances used by neurons to communicate with each other and with target tissues. They are synthesized and released from nerve endings into the synaptic cleft, where they bind to receptor proteins in the cellular membrane of the target tissue. Neurotransmitters can be classified into different types, including small molecules (such as acetylcholine, dopamine, norepinephrine, serotonin, and GABA) and large molecules (such as neuropeptides). They can also be classified as excitatory or inhibitory. Receptors can be ionotropic or metabotropic, and the effects of neurotransmitters can be fast of slow. Some important neurotransmitters include acetylcholine, dopamine, GABA, norepinephrine, and serotonin. Each neurotransmitter has a specific synthesis, breakdown, and receptor type. Understanding neurotransmitters is important for understanding the function of the nervous system and for developing treatments for neurological and psychiatric disorders.

Wernicke’s area is located in the categorical hemisphere or left hemisphere in about 95% of right handed individuals and 60% of left handed individuals. It is involved in the comprehension or understanding of written and spoken language. In contrast Broca’s area is involved in production of language.

Intermediate Mechanism: Rationalisation

Rationalisation is a defense mechanism commonly used by individuals to create false but credible justifications for their behavior of actions. It involves the use of logical reasoning to explain away of justify unacceptable behavior of feelings. The individual may not be aware that they are using this mechanism, and it can be difficult to identify in oneself.

Rationalisation is considered an intermediate mechanism, as it is common in healthy individuals from ages three to ninety, as well as in neurotic disorders and in mastering acute adult stress. It can be dramatically changed by conventional psychotherapeutic interpretation.

Examples of rationalisation include a student who fails an exam and blames the teacher for not teaching the material well enough, of a person who cheats on their partner and justifies it by saying their partner was neglectful of unaffectionate. It allows the individual to avoid taking responsibility for their actions and to maintain a positive self-image.

Overall, rationalisation can be a useful defense mechanism in certain situations, but it can also be harmful if it leads to a lack of accountability and an inability to learn from mistakes.

It is important to note that myoclonus is a common occurrence when individuals are falling asleep and is not considered abnormal in this context. Tics share similarities with myoclonus, but one key difference is that tics can be partially suppressed.

Movement Disorders: Key Features

Movement disorders refer to a range of conditions that affect voluntary muscle movements. These disorders can be caused by various factors, including neurological conditions, medication side effects, and metabolic imbalances. The following table outlines some of the key features of common movement disorders:

Akinesia: Absence of loss of control of voluntary muscle movements, often seen in severe Parkinson’s disease.

Bradykinesia: Slowness of voluntary movement, a core symptom of Parkinson’s disease.

Akathisia: Subjective feeling of inner restlessness, often caused by antipsychotic medication use.

Athetosis: Continuous stream of slow, flowing, writhing involuntary movements, often seen in cerebral palsy, stroke, and Huntington’s disease.

Chorea: Brief, quasi-purposeful, irregular contractions that appear to flow from one muscle to the next, often seen in Huntington’s disease and Wilson’s disease.

Dystonia: Involuntary sustained of intermittent muscle contractions that cause twisting and repetitive movements, abnormal postures, of both.

Dyskinesia: General term referring to problems with voluntary movements and the presence of involuntary movements, often drug-induced.

Myoclonus: A sequence of repeated, often non-rhythmic, brief shock-like jerks due to sudden involuntary contraction of relaxation of one of more muscles.

Parkinsonism: Syndrome characterized by tremor, rigidity, and bradykinesia.

Tic: Sudden, repetitive, non-rhythmic, stereotyped motor movement of vocalization involving discrete muscle groups, often seen in Tourette’s syndrome.

Tremor: Involuntary, rhythmic, alternating movement of one of more body parts, often seen in essential tremor, Parkinson’s disease, and alcohol withdrawal.

Hemiballismus: Repetitive, but constantly varying, large amplitude involuntary movements of the proximal parts of the limbs, often seen in stroke and traumatic brain injury.

Stereotypies: Repetitive, simple movements that can be voluntarily suppressed, often seen in autism and intellectual disability.

It is important to consider the underlying conditions and factors that may contribute to movement disorders in order to properly diagnose and treat these conditions.

Behaviour change theories can be categorized into two main groups: social cognition models and stage models. Stage models involve progression through specific stages, while social cognition models focus on beliefs and attitudes as drivers of behaviour change. Examples of social cognition models include the health belief model, protection motivation theory, and self-efficacy theory.

Hypocretin deficiency has been linked to narcolepsy, as it is a neuropeptide hormone produced in the hypothalamus that plays a crucial role in regulating sleep, arousal, appetite, and energy expenditure (also known as orexin) (Mignot, 2000).

Sleep Disorders

The International Classification of Sleep Disorders (ISCD) categorizes sleep disorders into several main categories and subclasses. Dyssomnias are intrinsic sleep disorders that include narcolepsy, psychopsychologic insomnia, idiopathic hypersomnia, restless leg syndrome, periodic limb movement disorder, and obstructive sleep apnea. Extrinsic sleep disorders include inadequate sleep hygiene and alcohol-dependent sleep disorder. Circadian rhythm disorders consist of jet lag syndrome, shift work sleep disorder, irregular sleep-wake pattern, delayed sleep phase syndrome, and advanced sleep phase disorder. Parasomnias include arousal disorders such as sleepwalking and sleep terrors, sleep-wake transition disorders such as rhythmic movement disorder, sleep talking, and nocturnal leg cramps, and parasomnias associated with REM sleep such as nightmares and sleep paralysis. Sleep disorders associated with medical/psychiatric disorders and proposed sleep disorders are also included in the classification.

Narcolepsy is a disorder of unknown cause that is characterized by excessive sleepiness, cataplexy, and other REM sleep phenomena such as sleep paralysis and hypnagogic hallucinations. Periodic limb movement disorder is characterized by periodic episodes of repetitive and highly stereotyped limb movements that occur during sleep. Restless legs syndrome is a disorder characterized by disagreeable leg sensations that usually occur prior to sleep onset and that cause an almost irresistible urge to move the legs. Jet lag syndrome consists of varying degrees of difficulties in initiating or maintaining sleep, excessive sleepiness, decrements in subjective daytime alertness and performance, and somatic symptoms following rapid travel across multiple time zones. Shift work sleep disorder consists of symptoms of insomnia of excessive sleepiness that occur as transient phenomena in relation to work schedules. Non 24 hour sleep wake syndrome consists of a chronic steady pattern comprising one to two hour daily delays in sleep onset and wake times in an individual living in society. Sleepwalking consists of a series of complex behaviors that are initiated during slow-wave sleep and result in walking during sleep. Sleep terrors are characterized by a sudden arousal from slow wave sleep with a piercing scream of cry, accompanied by autonomic and behavioral manifestations of intense fear. Rhythmic movement disorder comprises a group of stereotyped, repetitive movements involving large muscles, usually of the head and neck. Sleep starts are sudden, brief contractions of the legs, sometimes also involving the arms and head, that occur at sleep onset. Nocturnal leg cramps are painful sensations of muscular tightness of tension, usually in the calf but occasionally in the foot, that occur during the sleep episode. Nightmares are frightening dreams that usually awaken the sleeper from REM sleep. Sleep paralysis is a common condition characterized by transient paralysis of skeletal muscles which occurs when awakening from sleep of less often while falling asleep.