Delta waves are typically observed during stages III and IV of deep sleep and their presence outside of these stages can indicate diffuse slowing and encephalopathy.

Electroencephalography

Electroencephalography (EEG) is a clinical test that records the brain’s spontaneous electrical activity over a short period of time using multiple electrodes placed on the scalp. It is mainly used to rule out organic conditions and can help differentiate dementia from other disorders such as metabolic encephalopathies, CJD, herpes encephalitis, and non-convulsive status epilepticus. EEG can also distinguish possible psychotic episodes and acute confusional states from non-convulsive status epilepticus.

Not all abnormal EEGs represent an underlying condition, and psychotropic medications can affect EEG findings. EEG abnormalities can also be triggered purposely by activation procedures such as hyperventilation, photic stimulation, certain drugs, and sleep deprivation.

Specific waveforms are seen in an EEG, including delta, theta, alpha, sigma, beta, and gamma waves. Delta waves are found frontally in adults and posteriorly in children during slow wave sleep, and excessive amounts when awake may indicate pathology. Theta waves are generally seen in young children, drowsy and sleeping adults, and during meditation. Alpha waves are seen posteriorly when relaxed and when the eyes are closed, and are also seen in meditation. Sigma waves are bursts of oscillatory activity that occur in stage 2 sleep. Beta waves are seen frontally when busy of concentrating, and gamma waves are seen in advanced/very experienced meditators.

Certain conditions are associated with specific EEG changes, such as nonspecific slowing in early CJD, low voltage EEG in Huntington’s, diffuse slowing in encephalopathy, and reduced alpha and beta with increased delta and theta in Alzheimer’s.

Common epileptiform patterns include spikes, spike/sharp waves, and spike-waves. Medications can have important effects on EEG findings, with clozapine decreasing alpha and increasing delta and theta, lithium increasing all waveforms, lamotrigine decreasing all waveforms, and valproate having inconclusive effects on delta and theta and increasing beta.

Overall, EEG is a useful tool in clinical contexts for ruling out organic conditions and differentiating between various disorders.

Electroencephalography

Electroencephalography (EEG) is a clinical test that records the brain’s spontaneous electrical activity over a short period of time using multiple electrodes placed on the scalp. It is mainly used to rule out organic conditions and can help differentiate dementia from other disorders such as metabolic encephalopathies, CJD, herpes encephalitis, and non-convulsive status epilepticus. EEG can also distinguish possible psychotic episodes and acute confusional states from non-convulsive status epilepticus.

Not all abnormal EEGs represent an underlying condition, and psychotropic medications can affect EEG findings. EEG abnormalities can also be triggered purposely by activation procedures such as hyperventilation, photic stimulation, certain drugs, and sleep deprivation.

Specific waveforms are seen in an EEG, including delta, theta, alpha, sigma, beta, and gamma waves. Delta waves are found frontally in adults and posteriorly in children during slow wave sleep, and excessive amounts when awake may indicate pathology. Theta waves are generally seen in young children, drowsy and sleeping adults, and during meditation. Alpha waves are seen posteriorly when relaxed and when the eyes are closed, and are also seen in meditation. Sigma waves are bursts of oscillatory activity that occur in stage 2 sleep. Beta waves are seen frontally when busy of concentrating, and gamma waves are seen in advanced/very experienced meditators.

Certain conditions are associated with specific EEG changes, such as nonspecific slowing in early CJD, low voltage EEG in Huntington’s, diffuse slowing in encephalopathy, and reduced alpha and beta with increased delta and theta in Alzheimer’s.

Common epileptiform patterns include spikes, spike/sharp waves, and spike-waves. Medications can have important effects on EEG findings, with clozapine decreasing alpha and increasing delta and theta, lithium increasing all waveforms, lamotrigine decreasing all waveforms, and valproate having inconclusive effects on delta and theta and increasing beta.

Overall, EEG is a useful tool in clinical contexts for ruling out organic conditions and differentiating between various disorders.

Neurodevelopment: Understanding Brain Development

The development of the central nervous system begins with the neuroectoderm, a specialized region of ectoderm. The embryonic brain is divided into three areas: the forebrain (prosencephalon), midbrain (mesencephalon), and hindbrain (rhombencephalon). The prosencephalon further divides into the telencephalon and diencephalon, while the hindbrain subdivides into the metencephalon and myelencephalon.

The telencephalon, of cerebrum, consists of the cerebral cortex, underlying white matter, and the basal ganglia. The diencephalon includes the prethalamus, thalamus, hypothalamus, subthalamus, epithalamus, and pretectum. The mesencephalon comprises the tectum, tegmentum, ventricular mesocoelia, cerebral peduncles, and several nuclei and fasciculi.

The rhombencephalon includes the medulla, pons, and cerebellum, which can be subdivided into a variable number of transversal swellings called rhombomeres. In humans, eight rhombomeres can be distinguished, from caudal to rostral: Rh7-Rh1 and the isthmus. Rhombomeres Rh7-Rh4 form the myelencephalon, while Rh3-Rh1 form the metencephalon.

Understanding neurodevelopment is crucial in comprehending brain development and its complexities. By studying the different areas of the embryonic brain, we can gain insight into the formation of the central nervous system and its functions.

Pathology Findings in Psychiatry

There are several pathology findings that are associated with various psychiatric conditions. Papp-Lantos bodies, for example, are visible in the CNS and are associated with multisystem atrophy. Pick bodies, on the other hand, are large, dark-staining aggregates of proteins in neurological tissue and are associated with frontotemporal dementia.

Lewy bodies are another common pathology finding in psychiatry and are associated with Parkinson’s disease and Lewy Body dementia. These are round, concentrically laminated, pale eosinophilic cytoplasmic inclusions that are aggregates of alpha-synuclein.

Other pathology findings include asteroid bodies, which are associated with sarcoidosis and berylliosis, and are acidophilic, stellate inclusions in giant cells. Barr bodies are associated with stains of X chromosomes and are inactivated X chromosomes that appear as a dark staining mass in contact with the nuclear membrane.

Mallory bodies are another common pathology finding and are associated with alcoholic hepatitis, alcoholic cirrhosis, Wilson’s disease, and primary-biliary cirrhosis. These are eosinophilic intracytoplasmic inclusions in hepatocytes that are made up of intermediate filaments, predominantly prekeratin.

Other pathology findings include Schaumann bodies, which are associated with sarcoidosis and berylliosis, and are concentrically laminated inclusions in giant cells. Zebra bodies are associated with Niemann-Pick disease, Tay-Sachs disease, of any of the mucopolysaccharidoses and are palisaded lamellated membranous cytoplasmic bodies seen in macrophages.

LE bodies, also known as hematoxylin bodies, are associated with SLE (lupus) and are nuclei of damaged cells with bound anti-nuclear antibodies that become homogeneous and loose chromatin pattern. Verocay bodies are associated with Schwannoma (Neurilemoma) and are palisades of nuclei at the end of a fibrillar bundle.

Hirano bodies are associated with normal aging but are more numerous in Alzheimer’s disease. These are eosinophilic, football-shaped inclusions seen in neurons of the brain. Neurofibrillary tangles are another common pathology finding in Alzheimer’s disease and are made up of microtubule-associated proteins and neurofilaments.

Kayser-Fleischer rings are associated with Wilson’s disease and are rings of discoloration on the cornea. Finally, Kuru plaques are associated with Kuru and Gerstmann-Sträussler syndrome and are sometimes present in patients with Creutzfeldt-Jakob disease (CJD). These are composed partly of a host-encoded prion protein.

Glutamate is the primary neurotransmitter responsible for excitatory signaling in the brain.

Glutamate: The Most Abundant Neurotransmitter in the Brain

Glutamate is a neurotransmitter that is found in abundance in the brain. It is always excitatory and can act through both ionotropic and metabotropic receptors. This neurotransmitter is believed to play a crucial role in learning and memory processes. Its ability to stimulate neurons and enhance synaptic plasticity is thought to be responsible for its role in memory formation. Glutamate is also involved in various other brain functions, including motor control, sensory perception, and emotional regulation. Its importance in the brain makes it a target for various neurological disorders, including Alzheimer’s disease, Parkinson’s disease, and epilepsy.

DBS is primarily used to treat Parkinson’s disease by targeting the Globus pallidus interna and subthalamic nucleus. However, for treatment-resistant depression (TRD), the subcallosal cingulate was the first area investigated for DBS, while vagal nerve stimulation has also been used. Psychosurgical treatment for refractory OCD and TRD involves targeting the anterior limb of the internal capsule. Although the caudate nucleus is part of the basal ganglia and associated with Parkinson’s disease, it is not a primary target for DBS.

The trigeminal nerve, which is the largest cranial nerve, serves both sensory and motor functions. It is composed of three primary branches, namely the ophthalmic, maxillary, and mandibular branches. This nerve is responsible for providing sensory information to the face and head, while also controlling the muscles involved in chewing. On the other hand, the facial nerve is responsible for controlling the muscles that enable facial expressions and transmitting information from the front two-thirds of the tongue.

Overview of Cranial Nerves and Their Functions

The cranial nerves are a complex system of nerves that originate from the brain and control various functions of the head and neck. There are twelve cranial nerves, each with a specific function and origin. The following table provides a simplified overview of the cranial nerves, including their origin, skull exit, modality, and functions.

The first cranial nerve, the olfactory nerve, originates from the telencephalon and exits through the cribriform plate. It is a sensory nerve that controls the sense of smell. The second cranial nerve, the optic nerve, originates from the diencephalon and exits through the optic foramen. It is a sensory nerve that controls vision.

The third cranial nerve, the oculomotor nerve, originates from the midbrain and exits through the superior orbital fissure. It is a motor nerve that controls eye movement, pupillary constriction, and lens accommodation. The fourth cranial nerve, the trochlear nerve, also originates from the midbrain and exits through the superior orbital fissure. It is a motor nerve that controls eye movement.

The fifth cranial nerve, the trigeminal nerve, originates from the pons and exits through different foramina depending on the division. It is a mixed nerve that controls chewing and sensation of the anterior 2/3 of the scalp. It also tenses the tympanic membrane to dampen loud noises.

The sixth cranial nerve, the abducens nerve, originates from the pons and exits through the superior orbital fissure. It is a motor nerve that controls eye movement. The seventh cranial nerve, the facial nerve, also originates from the pons and exits through the internal auditory canal. It is a mixed nerve that controls facial expression, taste of the anterior 2/3 of the tongue, and tension on the stapes to dampen loud noises.

The eighth cranial nerve, the vestibulocochlear nerve, originates from the pons and exits through the internal auditory canal. It is a sensory nerve that controls hearing. The ninth cranial nerve, the glossopharyngeal nerve, originates from the medulla and exits through the jugular foramen. It is a mixed nerve that controls taste of the posterior 1/3 of the tongue, elevation of the larynx and pharynx, and swallowing.

The tenth cranial nerve, the vagus nerve, also originates from the medulla and exits through the jugular foramen. It is a mixed nerve that controls swallowing, voice production, and parasympathetic supply to nearly all thoracic and abdominal viscera. The eleventh cranial nerve, the accessory nerve, originates from the medulla and exits through the jugular foramen. It is a motor nerve that controls shoulder shrugging and head turning.

The twelfth cranial nerve, the hypoglossal nerve, originates from the medulla and exits through the hypoglossal canal. It is a motor nerve that controls tongue movement. Overall, the cranial nerves play a crucial role in controlling various functions of the head and neck, and any damage of dysfunction can have significant consequences.

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.

The Amygdala: A Key Player in Emotional Processing

The amygdala is a small, almond-shaped structure located in the anterior temporal lobe of the brain. As a core component of the limbic system, it plays a crucial role in emotional processing and regulation.

To better understand its function, we can use the metaphor of a car being driven on the road. The frontal lobe of the brain acts as the driver, making decisions and navigating the environment. The amygdala, on the other hand, serves as the dashboard, providing the driver with important information about the car’s status, such as temperature and fuel levels. In this way, the amygdala gives emotional meaning to sensory input, allowing us to respond appropriately to potential threats of opportunities.

One of the amygdala’s primary functions is to activate the fight or flight response in response to perceived danger. It does this by sending signals to the hypothalamus, which in turn triggers the release of stress hormones like adrenaline and cortisol. This prepares the body to either confront the threat of flee from it.

In addition to its role in the fight or flight response, the amygdala also plays a role in regulating appetite and eating behavior. Studies have shown that damage to the amygdala can lead to overeating and obesity, suggesting that it may be involved in the hypothalamic control of feeding behavior.

Overall, the amygdala is a key player in emotional processing and regulation, helping us to respond appropriately to the world around us.

Neuroimaging techniques can be divided into structural and functional types, although this distinction is becoming less clear as new techniques emerge. Structural techniques include computed tomography (CT) and magnetic resonance imaging (MRI), which use x-rays and magnetic fields, respectively, to produce images of the brain’s structure. Functional techniques, on the other hand, measure brain activity by detecting changes in blood flow of oxygen consumption. These include functional MRI (fMRI), emission tomography (PET and SPECT), perfusion MRI (pMRI), and magnetic resonance spectroscopy (MRS). Some techniques, such as diffusion tensor imaging (DTI), combine both structural and functional information to provide a more complete picture of the brain’s anatomy and function. DTI, for example, uses MRI to estimate the paths that water takes as it diffuses through white matter, allowing researchers to visualize white matter tracts.

Dura Mater

The dura mater is one of the three membranes, known as meninges, that cover the brain and spinal cord. It is the outermost and most fibrous layer, with the pia mater and arachnoid mater making up the remaining layers. The pia mater is the innermost layer.

The dura mater is folded at certain points, including the falx cerebri, which separates the two cerebral hemispheres of the brain, the tentorium cerebelli, which separates the cerebellum from the cerebrum, the falx cerebelli, which separates the cerebellar hemispheres, and the sellar diaphragm, which covers the pituitary gland and forms a roof over the hypophyseal fossa.

Dhat is a syndrome that is specific to Indian culture and affects men. Those who suffer from it experience anxiety about the presence of semen in their urine, which they believe leads to a loss of energy.

Creutzfeldt-Jakob Disease: Differences between vCJD and CJD

Creutzfeldt-Jakob Disease (CJD) is a prion disease that includes scrapie, BSE, and Kuru. However, there are important differences between sporadic (also known as classic) CJD and variant CJD. The table below summarizes these differences.

vCJD:
– Longer duration from onset of symptoms to death (a year of more)
– Presents with psychiatric and behavioral symptoms before neurological symptoms
– MRI shows pulvinar sign
– EEG shows generalized slowing
– Originates from infected meat products
– Affects younger people (age 25-30)

CJD:
– Shorter duration from onset of symptoms to death (a few months)
– Presents with neurological symptoms
– MRI shows bilateral anterior basal ganglia high signal
– EEG shows biphasic and triphasic waves 1-2 per second
– Originates from genetic mutation (bad luck)
– Affects older people (age 55-65)

Overall, understanding the differences between vCJD and CJD is important for diagnosis and treatment.

While alpha (α) and beta (β) activity are typical in adults who are awake and at rest, delta activity (δ) may suggest the presence of a brain tumor. Mu (μ) activity is linked to movement, and theta activity (θ) is uncommon in the waking adult population, occurring briefly in only 15% of individuals.

The Basal Ganglia: Functions and Disorders

The basal ganglia are a group of subcortical structures that play a crucial role in controlling movement and some cognitive processes. The components of the basal ganglia include the striatum (caudate, putamen, nucleus accumbens), subthalamic nucleus, globus pallidus, and substantia nigra (divided into pars compacta and pars reticulata). The putamen and globus pallidus are collectively referred to as the lenticular nucleus.

The basal ganglia are connected in a complex loop, with the cortex projecting to the striatum, the striatum to the internal segment of the globus pallidus, the internal segment of the globus pallidus to the thalamus, and the thalamus back to the cortex. This loop is responsible for regulating movement and cognitive processes.

However, problems with the basal ganglia can lead to several conditions. Huntington’s chorea is caused by degeneration of the caudate nucleus, while Wilson’s disease is characterized by copper deposition in the basal ganglia. Parkinson’s disease is associated with degeneration of the substantia nigra, and hemiballism results from damage to the subthalamic nucleus.

In summary, the basal ganglia are a crucial part of the brain that regulate movement and some cognitive processes. Disorders of the basal ganglia can lead to significant neurological conditions that affect movement and other functions.

Cranial Nerve Reflexes

When it comes to questions on cranial nerve reflexes, it is important to match the reflex to the nerves involved. Here are some examples:

– Pupillary light reflex: involves the optic nerve (sensory) and oculomotor nerve (motor).
– Accommodation reflex: involves the optic nerve (sensory) and oculomotor nerve (motor).
– Jaw jerk: involves the trigeminal nerve (sensory and motor).
– Corneal reflex: involves the trigeminal nerve (sensory) and facial nerve (motor).
– Vestibulo-ocular reflex: involves the vestibulocochlear nerve (sensory) and oculomotor, trochlear, and abducent nerves (motor).

Another example of a cranial nerve reflex is the gag reflex, which involves the glossopharyngeal nerve (sensory) and the vagus nerve (motor). This reflex is important for protecting the airway from foreign objects of substances that may trigger a gag reflex. It is also used as a diagnostic tool to assess the function of these nerves.

Electroencephalography

Electroencephalography (EEG) is a clinical test that records the brain’s spontaneous electrical activity over a short period of time using multiple electrodes placed on the scalp. It is mainly used to rule out organic conditions and can help differentiate dementia from other disorders such as metabolic encephalopathies, CJD, herpes encephalitis, and non-convulsive status epilepticus. EEG can also distinguish possible psychotic episodes and acute confusional states from non-convulsive status epilepticus.

Not all abnormal EEGs represent an underlying condition, and psychotropic medications can affect EEG findings. EEG abnormalities can also be triggered purposely by activation procedures such as hyperventilation, photic stimulation, certain drugs, and sleep deprivation.

Specific waveforms are seen in an EEG, including delta, theta, alpha, sigma, beta, and gamma waves. Delta waves are found frontally in adults and posteriorly in children during slow wave sleep, and excessive amounts when awake may indicate pathology. Theta waves are generally seen in young children, drowsy and sleeping adults, and during meditation. Alpha waves are seen posteriorly when relaxed and when the eyes are closed, and are also seen in meditation. Sigma waves are bursts of oscillatory activity that occur in stage 2 sleep. Beta waves are seen frontally when busy of concentrating, and gamma waves are seen in advanced/very experienced meditators.

Certain conditions are associated with specific EEG changes, such as nonspecific slowing in early CJD, low voltage EEG in Huntington’s, diffuse slowing in encephalopathy, and reduced alpha and beta with increased delta and theta in Alzheimer’s.

Common epileptiform patterns include spikes, spike/sharp waves, and spike-waves. Medications can have important effects on EEG findings, with clozapine decreasing alpha and increasing delta and theta, lithium increasing all waveforms, lamotrigine decreasing all waveforms, and valproate having inconclusive effects on delta and theta and increasing beta.

Overall, EEG is a useful tool in clinical contexts for ruling out organic conditions and differentiating between various disorders.

Neuroimaging studies have shown that Alzheimer’s dementia is linked to a gradual increase in ventricular size, while schizophrenia is associated with non-progressive enlargement of the lateral and third ventricles. Although some studies have reported increased ventricular size in individuals with affective disorders, the findings are not consistent. Additionally, individuals with antisocial personality disorder may have reduced prefrontal gray matter volume.

Deep brain stimulation (DBS) for treatment resistant depression targets specific brain regions based on their known involvement in pleasure, reward, and mood regulation. The nucleus accumbens is targeted due to its role in pleasure and reward processing. The inferior thalamic peduncle is targeted based on PET studies showing hyperactivity in depression. The lateral habenula is chosen due to observed hypermetabolism in depressed patients. The subgenual cingulate gyrus is targeted due to its hyperactivity in depression. The ventral capsule/ventral striatum is chosen based on its association with improved mood and reduced depressive symptoms following ablation treatments for OCD and depression.

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.

The sphenoid bone contains a saddle-shaped depression known as the sella turcica. The anterior cranial fossa is formed by the frontal, ethmoid, and a portion of the sphenoid bones. The middle cranial fossa is formed by the sphenoid and temporal bones, while the posterior cranial fossa is formed by the occipital and temporal bones.

Neurotrophins: Crucial for Neuronal Growth and Development

Neurotrophins are essential for the growth and development of neurons. However, disturbances in neurotrophic factors may contribute to some neurodevelopmental aspects of schizophrenia and major depression.

Studies have shown that patients with schizophrenia have increased concentrations of Brain-derived neurotrophic factor (BDNF) in cortical areas, but decreased levels in the hippocampus compared to controls. Additionally, patients with schizophrenia have lower concentrations of neurotrophin-3 in frontal and parietal areas than controls.

These findings suggest that neurotrophins play a critical role in the pathophysiology of schizophrenia and major depression. Further research is needed to fully understand the mechanisms underlying these disturbances in neurotrophic factors.

Melanin

Melanin is a pigment found in various parts of the body, including the skin, hair, and eyes. It is produced by specialized cells called melanocytes, which are located in the skin’s basal layer. The function of melanin in the body is not fully understood, but it is thought to play a role in protecting the skin from the harmful effects of ultraviolet (UV) radiation from the sun. Additionally, melanin may be a by-product of neurotransmitter synthesis, although this function is not well established. Overall, the role of melanin in the body is an area of ongoing research.

Actin is the primary component of Hirano bodies, which are indicative of neurodegeneration but lack specificity.

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.

Cerebral Tumours

The most common brain tumours in adults, listed in order of frequency, are metastatic tumours, glioblastoma multiforme, anaplastic astrocytoma, and meningioma. On the other hand, the most common brain tumours in children, listed in order of frequency, are astrocytoma, medulloblastoma, and ependymoma.

White matter is the cabling that links different parts of the CNS together. There are three types of white matter cables: projection tracts, commissural tracts, and association tracts. Projection tracts connect higher centers of the brain with lower centers, commissural tracts connect the two hemispheres together, and association tracts connect regions of the same hemisphere. Some common tracts include the corticospinal tract, which connects the motor cortex to the brainstem and spinal cord, and the corpus callosum, which is the largest white matter fiber bundle connecting corresponding areas of cortex between the hemispheres. Other tracts include the cingulum, superior and inferior occipitofrontal fasciculi, and the superior and inferior longitudinal fasciculi.

Normal Pressure Hydrocephalus

Normal pressure hydrocephalus is a type of chronic communicating hydrocephalus, which occurs due to the impaired reabsorption of cerebrospinal fluid (CSF) by the arachnoid villi. Although the CSF pressure is typically high, it remains within the normal range, and therefore, it does not cause symptoms of high intracranial pressure (ICP) such as headache and nausea. Instead, patients with normal pressure hydrocephalus usually present with a classic triad of symptoms, including incontinence, gait ataxia, and dementia, which is often referred to as wet, wobbly, and wacky. Unfortunately, this condition is often misdiagnosed as Parkinson’s of Alzheimer’s disease.

The classic triad of normal pressure hydrocephalus, also known as Hakim’s triad, includes gait instability, urinary incontinence, and dementia. On the other hand, non-communicating hydrocephalus results from the obstruction of CSF flow in the third of fourth ventricle, which causes symptoms of raised intracranial pressure, such as headache, vomiting, hypertension, bradycardia, altered consciousness, and papilledema.

The BOLD technique is used by fMRI to non-invasively map cortical activation, while PET and SPECT require the administration of a radioactive isotope and are invasive. Although all three magnetic imaging techniques are non-invasive, fMRI stands out for its use of the BOLD technique.

HPA Axis Dysfunction in Mood Disorders

The HPA axis, which includes regulatory neural inputs and a feedback loop involving the hypothalamus, pituitary, and adrenal glands, plays a central role in the stress response. Excessive secretion of cortisol, a glucocorticoid hormone, can lead to disruptions in cellular functioning and widespread physiologic dysfunction. Dysregulation of the HPA axis is implicated in mood disorders such as depression and bipolar affective disorder.

In depressed patients, cortisol levels often do not decrease as expected in response to the administration of dexamethasone, a synthetic corticosteroid. This abnormality in the dexamethasone suppression test is thought to be linked to genetic of acquired defects of glucocorticoid receptors. Tricyclic antidepressants have been shown to increase expression of glucocorticoid receptors, whereas this is not the case for SSRIs.

Early adverse experiences can produce long standing changes in HPA axis regulation, indicating a possible neurobiological mechanism whereby childhood trauma could be translated into increased vulnerability to mood disorder. In major depression, there is hypersecretion of cortisol, corticotropin-releasing factor (CRF), and ACTH, and associated adrenocortical enlargement. HPA abnormalities have also been found in other psychiatric disorders including Alzheimer’s and PTSD.

In bipolar disorder, dysregulation of ACTH and cortisol response after CRH stimulation have been reported. Abnormal DST results are found more often during depressive episodes in the course of bipolar disorder than in unipolar disorder. Reduced pituitary volume secondary to LHPA stimulation, resulting in pituitary hypoactivity, has been observed in bipolar patients.

Overall, HPA axis dysfunction is implicated in mood disorders, and understanding the underlying mechanisms may lead to new opportunities for treatments.

Prosopagnosia is a condition where individuals are unable to recognize familiar faces, which can be caused by damage to the fusiform area of be congenital. Achromatopsia, on the other hand, is color blindness that can result from thalamus damage. Parietal lobe lesions can cause agraphesthesia, which is the inability to recognize numbers of letters traced on the palm, and astereognosis, which is the inability to recognize an item by touch. Lastly, phonagnosia is the inability to recognize familiar voices and is the auditory equivalent of prosopagnosia, although it is not as well-researched.

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.