User:Neuroscienceforlife/sandbox

Article Evaluation

The beginning of the article describes the Stroop effect in an efficient and concise manner. The author has a completely neutral perspective on the subject and even throws in a fun fact that intrigues the audience. In the last sentence in the Neuroanatomy portion of the article, the author talks about the anterior dorsal anterior cingulate cortex; however, it should have been written as dorsal anterior cingulate cortex (dACC). The links to the citation pages work. Something that could be added to the article would be the idea that stroop test shows cognitive dissonance is a way to control our behavior. This is an element of the brain only seen in humans, which helps to differentiate our brain from other primate brains. Neuroscienceforlife (talk) 01:15, 18 September 2017 (UTC)

Potential Articles

1. Free Nerve Ending:[[1]] -Notes:

• last edited on 31 July 2017
• The article does mention that free nerve ending detect pain stimulus, but fails to further explain transmission
• Discusses the structure, a better illustration could be used
• Briefly discusses adaptation, modality, and fiber types

Overall more information is needed on the topic in regards to actual transmission

2. Neurogenesis: [[2]] Notes:

• Discusses the two types of cells neurons are generated from
• A brief overview of the development and a little about Adult Neurogenesis
• The article needs more structure and detail

3. aphonogelia: Not on wikipedia The condition when a person cannot laugh out loud.

Neuroscienceforlife (talk) 20:13, 7 October 2017 (UTC)

Main Article information

Not to be confused with Paresthesia.

Pallesthesia refers to the sensation of mechanical vibration on or near the body. Vibration sense may be lost as a result of a number of lesions to the nervous system, often in conjunction with other deficits. The word "pallesthesia" is derived from the Greek pallein, meaning "to shake".

Testing

Pallesthesia may be tested for using a vibrating mechanical tuning fork, placed on a bony prominence.

Category:Sensory systems

My Notes:

• The above article is a very small stub article with low importance
• The one reference does not cite to the correct source, so all the information will be deleted and my first paragraph will be added

My revision:

Pallesthesia is the perception of vibration that is felt from the skin or bone . This sensation is usually stimulated by mechanoreceptors, such as Pacinian corpuscles, Merkel disk receptors, and Tactile corpuscles . All three of these receptors stimulate an action potential in afferent nerves found within the various layer of the skin and body. The afferent neuron travels to the spinal column, then up to the brain, where the information is processed. If a lesion occurs within the brain, the perception of vibration may be lost. Other neurological diseases can also effect the perception of vibration. In order to determine if a patient has a loss of vibration sensation, testing can be conducted using a tuning fork at 128 Hz and placing the it on a bone. This is because bones are particularly good resonators.

The second neuron in the figure depicts an encapsulated nerve ending.

Receptors

All three receptors are classified as encapsulated nerve endings, because they are involved in tactile stimulation.The Pacinian corpuscles are located within the deeper layer of the skin, under the skin in the subcutaneous tissues, within the muscles, in the periosteum, and other deeper layers of the body. The Merkel disk receptors are located in the superficial epidermis and in hair follicles, while Tactile corpuscles are concentrated heavily in the fingertips. Both the Merkel disk receptor and tactile corpuscles respond to low frequencies best to produce an action potential.

Pathway

The sensory conduction pathway that allows for cognitive recognition of vibration occurs through afferent neurons, also known as sensory neurons. The outside stimulus is a vibration, which actives one of the three encapsulated nerve endings mentioned above based upon where the sensation is felt. The intensity of the vibration must cause the neuron(s) to reach or surpass threshold in order for an action potential to be propagated. From here the signal travels through the dorsal column-medial lemniscal pathway.

The dorsal column-medial lemniscal pathway is comprised of the dorsal column within the spinal cord and the medial lemniscal in the brain stem. All the ascending sensory fibers are called the dorsal column. This is due to the fact that the ascending fibers gather at the dorsal funiculus in the spinal cord. The dorsal funiculus is located between the dorsal horn and the medial line in the spinal cord. The pathway consists of three types of neurons; first, second, and third order neurons. The first order neuron is the afferent neurons. The first order neuron enters the spinal cord through the dorsal root ganglia and branches in the spinal cord. Some neuron terminates in the spinal cord, where they contribute to a reflex response. Other neurons continue ipsilateral, same side, to the medulla oblongata. If the neurons are coming from the lower limbs they enter the medulla are carried by the fasciculus gracilis. If the neurons are coming from the upper limbs they are carried by the fasciculus cuneatus. In the medulla, at the dorsal column nuclei, the first order neuron synapses with the second order neuron, which then decussates (crosses over to the other side of the Central Nervous System) into the medial lemniscus. The second order neuron then carries the information to the venteral posterolateral nucleus of the thalamus and then the somatosensory cortex in the parietal lobe. Immediately, the posterior parietal lobe synthesizes the information into a recognizable pattern. The coded information is then sent to the prefrontal cortex to devise a motor response to the stimulation. The motor information is sent through efferent neurons.

Testing

In a doctor's office or in a research experiment, a person's perception of vibration can be test. One type of routine clinical testing is the Quantitative Vibratory Testing (QVT) and another is Rydel-Sheiffer tuning fork test. The typical frequency used in 128 Hz is used for a tuning fork .The common areas for testing in the bones are the metatarsals, the tibia, the malleoli, the anterior superior illiac crest, vertebrae in the spinal cord, sternum, clavicle, and the styloid processes of the radius and ulna . These are are particularly good for testing, because they are close to the surface of the skin, with only a small amount of muscle over them. To test the perception through the skin, small pads are placed on the fingertips. The test is conducted by placing a tuning fork upon a bony prominence and striking the fork. The amount of force used to strike the fork is directly proportional to the intensity of the perceived vibration and the duration . The lower limbs have a higher threshold than the upper limbs, so a higher frequency or force is needed.For accurate testing, both the left and right side of the body, aka homologous sites, need to be tested. The patient should lose the perception of pallesthesia, when changing sides. This is due to sensory adaptation, the receptors require a large threshold to produce an action potential because of previous stimulation. It should be of concern when a patient reports asymmetrical perception, this indicates an underlining neurological issue . Another factor of concern, is when a patient does not perceive vibration when the tuning fork is changed from the abnormal area to the normal area. Pallesthesia testing is often used to figure out different neurological disorders and is conducted on lesion patients to understand neurological pathways and functions. This test is often conducted in older patients because with advancing age there is a decline in vibratory sensation. Older patients may have complete loss of vibratory sensation in their toes . In order to determine if the cause is age or a neurological disorder, a partner of the same age must undergo the test as well and the results are compared.

Disorders

The benefits of pallesthesia is that it can be used to identify disorders within the neural pathways. There are only a finite amount of areas in the neural pathway that the sensation and perception can be disturbed. This enables doctors, to make accurate diagnoses about their patients health. It can help to identify neural disorders and the effects of other diseases on the nervous system, such as diabetes.

Neural disorders

The peripheral nervous system with an enlarged depiction of a afferent neuron.

Peripheral Nervous System

Peripheral Nervous System is composed of the afferent and efferent neurons. Damage to the peripheral nervous system is classified as Peripheral neuropathy. A vibration exam can detect any number of disorders within the peripheral nervous system. A gradual loss of sensation from the toes to the knees is consistent with a peripheral nerve problem, while an impairment in perceiving vibration from all extremities is a sign of a posterior column disorder. Impairments classified to the peripheral nervous system and posterior column are good indicators of demyelination of afferent neurons, which may be caused by any number of degenerative disorder of the peripheral nervous system.

Myelopathy

Myelopathy is a disorder within the spinal cord. Compression on the spinal cord by bony projections or a displaced disk in the cervical spine are the most common caused of myelopathy. Inflammation, illness, neurodegenerative, nutritional, and vascular disorder can also attribute to myelopathy. Quantitative Vibratory Testing can be used to diagnosis a patient with myelopathy. When performing the test the patient will report a uniform loss of vibration after a certain point. For example, if the fork is started at the toes and continues to the knees with a completely perception of vibration, but once the fork is placed at the illiac crest the patient no longer senses vibration, this would be a case of myelopathy. In addition, if the fork is placed on rostral spinous processes, the patient will be able to detect the intensity of the vibration level.

The Central Nervous System

Central Nervous System

Central Nervous System is composed of the spinal cord and the brain. Many neurological studies are conducted on patients with lesions. Scientists can actual gain more insight about the functions of different brain areas, by looking at damage to those areas. Thus, studies have been conducted on lesion patients for pallesthesia. A common disease to the central nervous system is Multiple sclerosis. In this disease, the immune system attacks the myelin sheath surrounding neurons. Deterioration of the myelin sheath drastically reduces the conduction speed of neurons, thus affecting sensation and motor control of the body. These patients exhibit the largest reduction in pallesthesia. They cannot perceive vibration at 128 Hz; however, studies have shown that 256 Hz can be perceived in young multiple sclerosis patients.

Diabetic Neurapathy

Diabetes mellitus is a disorder in which the body cannot break down glucose either because insulin is not produced or the body does not produce enough insulin, or both in some cases. This causes glucose to accumulate in the blood. High concentrations of glucose in the blood can cause injury to never fibers, resulting in Diabetic neuropathy. In most cases, the nerve damage occurs in afferent neurons in the foot and lower limbs. Nerve damage can be assessed with pallesthesia. If there is an inability to sense the vibration being applied from the tuning fork, then never damage has occurred. A doctor then assesses the damage and places the patient on a treatment, which in severe cases may be the amputation of a the foot or limb.

Research

In the early 1950s and through the 1970s, pallesthesia was used as a research method for many disorders in connection with the sensory system. The scientist hoped to find a new therapy that may be able to reconstruct neuronal outputs. They understood that damage to the central nervous system could not be repaired, however, they hoped to rewire the peripheral nervous system to give patients some of their sensation back. One study looked into the affects of pallesthesia on stroke patients. They theorized that sinusoidal stimulation may be an effective therapy, however, the results were inconclusive and the research forgotten. For current research, it is rare to use pallesthesia because other more improved methods of testing the sensory system have been developed.