Rapid eye movement sleep behavior disorder （RBD） is a parasomnia characterized by abnormal, dream-enacting behavior during REM sleep associated with nightmare, often results in injury to themselves or their bed partners.　Typically, most RBD patients can recall the details of vivid dreams upon awakening.　RBD usually emerges after the age of 50 years with a male predilection and an estimated prevalence is reported to be 0.5% in the general population.　The proposed pathophysiology of human RBD is that the involvement of brainstem nuclei responsible for controlling REM sleep, including pedunculopontine nucei, laterodorsal tegmental nucleus, sublaterodorsal nuclei and locus coeruleus, and neuronal networks involving the limbic system and neocortex may contribute to the occurrence of RBD.　Detecting REM sleep without atonia by polysomnography （PSG） is required for RBD diagnosis;however, prior to PSG examination, RBD screening tools, such as RBD screening questionnaire, are useful in clinical practice.　Low-dose clonazepam before bedtime is effective in most patients with RBD.　Several follow-up studies of RBD patients demonstrated the significant number of RBD patients developed synucleinopathies such as Parkinson’s disease （PD）, dementia with Lewy bodies （DLB） and multiple system atrophy （MSA）.　In addition, RBD patients exhibit olfactory impairment, color discrimination deficits, cognitive impairment, a reduced uptake of cardiac 123I-MIBG scintigraphy and hyperechogenicity of the substantia nigra on transcranial sonography, which are observed in Lewy body diseases such as PD and DLB.　Accumulating evidence suggests that idiopathic RBD could be a prodromal phase of Lewy body diseases and idiopathic RBD patients may be ideal condidates for future neuroprotective, disease modifying therapy.　We also discuss characteristic findings of cognitive impairment in PD and RBD.

Epileptic seizure in midnight is sometimes difficult to diagnose especially differentiate correctly from sleep related disorders such as night terror or noctambulation.　Epileptic seizure is usually occurred not only in midnight but also in daytime, which is one of the important differential diagnostic points between them.　Although some kinds of epilepsy shows only nocturnal seizure without any diurnal attack.　To clarify the incidence of epileptic seizure in a day, we analyzed frequency of seizure during video-EEG （VEEG） monitoring for the patients with medically intractable epilepsy.

Seventy nine times of VEEG in 58 patients （38 are mesial temporal epilepsy ［MTLE］, 13 Neocortical epilepsy ［NCE］, 7 others） were recorded during 8 years in our hospital.　The incidences of seizures between daytime and nighttime in a day were not statistically different in both MTLE and NCE.　On the other hand, the incidences of seizures in sleep state in MTLE and NCE are 28% and 44%, respectively.　Although it was not statistical different （P=0.074, Mann-Whitney U test）, seizure during sleep was more frequent in NCE than MTLE.　All patients were diagnosed correctly as epilepsy with VEEG even in sleep state.

Seizures in sleep are more frequent in NCE than MTLE.　VEEG is useful method to diagnose epilepsy differentiating from sleep related disorders.

Sleep disorders are highly prevalent among patients with dementia.　The frequency of insomnia in patients with Alzheimer’s disease （AD） is around 40-50%, and increases as the disease progresses.　Sleep disorders are more common in vascular dementia （VD） and dementia with Lewy bodies （DLB）.　In patients with DLB, REM sleep behavior disorder （RBD） is seen at a high rate at the prodromal stage or at early stages.　There are factors, including bio-socio-psychological factors, which contribute to sleep disorders in patients with dementia.　Biological factors in AD-related sleep disorders include the supraoptic nucleus dysfunction and decreased melatonin level due to a decline of pineal function.　The fact that the supraoptic nucleus degeneration in DLB is severe may be related to severe sleep disorders of DLB.　In addition the causes of sleep disorders include lack of exercise in the daytime, a long duration afternoon nap, and inappropriate or lack of sunlight exposure in the daytime.　In addition, therapeutic drugs for comorbidities, occlusive sleep apnea syndrome, restless leg syndrome, respiratory illnesses causing dyspnea, skin itching, and urinary diseases causing frequent urination can lead to sleep disorders.

BPSD, such as agitation, aggression, screaming, delusional thinking, and wandering, frequently worsens from late afternoon to the early evening, and this condition is called sundown syndrome.　It is difficult to differentiate sundown syndrome from delirium, since patients with dementia have some common clinical features.　Major difference between those two conditions is that delirium tends to be acute in onset, relatively brief in the course.　Delirium may develop at the prodromal stage of dementia.　The frequency of delirium is significantly higher at the prodromal stage of DLB than at that of AD.

For psychiatric and behavioral symptoms of dementia at nigh-time, non-pharmacological interventions are the first-line treatments.　Safety is the most important thing for pharmacotherapy.

The purpose of this article is to present the features of communication disorders in Alzheimer’s disease （AD） from the standpoint of a speech-language-hearing therapist. The basic communication disorders in AD are cognitive and language deficits, but AD patients often have hearing and visual defects related to ageing. First, we performed cluster analysis of communication disorders in probable AD patients to detect useful functions for their daily communication, and five clusters were identified. Only 4% of the patients were classified into the low communication score cluster, which indicated that most AD patients have some useful communication functions. Next, we investigated the results of two non-pharmacologic therapies. Hearing aids were provided for probable AD patients with presbycusis. The rate of using a hearing aid was 9.8%, and the criteria for selecting a hearing aid were auditory word discrimination and auditory attention. Group therapy using a “memory book,” which is a form of life review therapy, was also provided for AD patients. We performed several neuropsychological tests in two patients before and after these interventions. Some language functions improved remarkably, especially the naming score, episodic memory score, motivation for performance, and relations to others score. We will develop these methods for dementia, including the other kinds of dementia and mild cognitive impairment, to provide both disease-specific and disease-closing approaches that enhance the communication of dementia patients.

Sleep disorder is very common in population affected with dementia.　Although fragmentation and shallowing of nocturnal sleep are relatively common among dementia disorders, some specific abnormalities are present in respective dementia disorders, i.e. patients with Alzheimer type dementia are likely to show decreased amplitude of circadian rhythm leading to irregular sleep awake schedule and patients with Lewy body dementia frequently have dysfunction of the control of muscle tonus during REM sleep which may cause dream enactment abnormal behavior in this sleep stage.　For prevention of the appearance as well as the development of dementia, appropriate management of insomnia would be necessary.　However, usage of hypnotics （benzodiazepines and its agonists） in demented population may become a risk factor for falls, nocturnal delirious behavior and enhancement of cognitive dysfunction in the affected population.　In addition, we want to emphasize the necessity of proper management of obstructive sleep apnea syndrome, a common disorder in the elderly, would be desirable in individuals with dementia, since the disorder may become a risk factor for causing cerebrovascular events during sleep and for the aggravation of cognitive decline in this population.

Senile dementia of the neurofibrillary tangle （NFT） type （SD-NFT） is a disease entity characterized by a large amount of NFTs mainly in the hippocampal region and scarcity of senile plaques （Aβ deposition） throughout the brain, distinguished from Alzheimer’s disease （AD） in clinical, pathological, and genetic aspects.　Prevalence of the SD-NFT in older people with dementia is about 5%.　Clinically, SD-NFT is a slowly progressive dementia with sporadic onset.　At the initial image, memory disturbance is a main symptom with relative preservation of other cognitive functions ［mild cognitive impairment （MCI） stage］;after very slow progression of the memory disturbance, disorientation and other cognitive functions appeared （dementia stage）.　Laboratory findings include medial temporal lobe atrophy on CT and MRI, and negative finding on amyloid imaging.　Tau imaging, with which clinical studies are ongoing, would be useful for the diagnosis of detection of NFTs.　Cerebrospinal fluid （CSF） markers for SD-NFT would include elevated levels of phosphorylated tau and normal levels of Aβ1-42, which needs to be confirmed by pathologically confirmed cases.　Currently, no therapies have been proved to be effective for SD-NFT;tau-targeted therapies are currently under development.

Parkinson’s disease （PD）, a progressive neurodegenerative disease, has been traditionally defined by its characteristic motor symptoms.　Cognitive impairment is one of the most common and important non-motor symptoms of PD that, greatly affects functioning and quality of life.　Cognitive decline in PD is characterized by its heterogeneity, with impairments manifesting in one or multiple cognitive domains.　Most PD patients eventually develop impairment of attentional, executive, and visuospatial function.　Dopaminergic deficits in the frontostriatal circuits cause mainly executive, cognitive deficits.　By contrast, cholinergic depletion has a cognitive profile of memory and visuoconstructional deficits.

Restless legs syndrome （RLS） is a sleep-related movement disorder with disturbed sleep and reduced quality of life.　Specific neurocognitive domains including executive attention, working memory, and divergent higher cognitive functions are particularly vulnerable to sleep loss.　The sleep deprivation associated with RLS also results in neurocognitive performance decrements similar to those seen in sleep restriction studies;, however, the reported impact of RLS on cognition has been conflicting.

In this review, cognitive functions in PD and RLS is discussed.

Nagase analbuminemic rats （NARs） have been proposed as a new animal model of ADHD;however, it is necessary to determine whether this animal model has high validity.　Therefore, in this study, to determine whether NARs can be suitable as an animal model of ADHD with high validity, we examined behavioral abnormalities in association with the inattention, impulsivity, and hyperactivity （observed in ADHD） of NARs using the 5-choice serial reaction time task （5-CSRTT） and a familiar environmental open field.　As a result, an accuracy to be the index of the attention in NAR was lower, compared to Sprague-Dawley （SD） rat of wild-type （p<0.001）.　In addition, the impulsivity index and number of premature responses was higher in NAR （p<0.01）.　Furthermore, in the familiar environmental open-field, the distance traveled （an index of hyperactivity） was greater in NARs （p<0.01）.　NAR was full of it as an ADHD animal model than the above behaviorally, and it was suggested that it was the animal model that had high validity.