Aperture Problem

Each neuron in the visual system is sensitive to visual input in a small part of the visual field, as if each neuron is looking at the visual field through a small window or aperture. The motion direction of a contour is ambiguous, because the motion component parallel to the line cannot be inferred based on the visual input. This means that a variety of contours of different orientations moving at different speeds can cause identical responses in a motion sensitive neuron in the visual system.

The Aperture Problem. The grating appears to be moving down and to the right, perpendicular to the orientation of the bars. But it could be moving in many other directions, such as only down, or only to the right. It is impossible to tell unless the ends of the bars become visible in the aperture.

Motion perception

Motion perception is the process of inferring the speed and direction of elements in a scene based on visual, vestibular and proprioceptive inputs.

Area V5 seems to be important to the processing of visual motion and damage to this area can disrupt motion perception.

First-order motion perception refers to the perception of the motion of an object that differs in luminance from its background, such as a black bug crawling across a white page.

Second-order motion is motion in which the moving contour is defined by contrast, texture, flicker or some other quality that does not result in an increase in luminance or motion energy in the Fourier spectrum of the stimulus.

visual cortex

The term visual cortex refers to the primary visual cortex and extrastriate visual cortical areas such as V2, V3, V4, and V5.

V1: The primary visual cortex, also the koniocortex (sensory type) located in and around the calcarine fissure in the occipital lobe. It receives information directly from the lateral geniculate nucleus.

V2: Also called prestriate cortex. It receives strong feedforward connections from V1 and sends strong connections to V3, V4, and V5. It also sends strong feedback connections to V1. V2 is split into four quadrants, a dorsal and ventral representation in the left and the right hemispheres. Together these four regions provide a complete map of the visual world. Cells are tuned to simple properties such as orientation, spatial frequency, and color.

V3: The term third visual complex refers to the region of cortex located immediately in front of V2, which includes the region named visual area V3 in humans. It is divided in furthur dorsal V3 and Ventral V3. Dorsal and ventral V3 have distinct connections with other parts of the brain, appear different in sections stained with a variety of methods, and contain neurons that respond to different combinations of visual stimulus. Dorsal V3 may be anatomically located in Brodmann area 19.

V4: It is one of the visual areas in the extrastriate visual cortex of the macaque monkey. It is located anterior to V2 and posterior to visual area PIT. It is unknown what the human homologue of V4 is, and this issue is currently the subject of much scrutiny.

V5: Visual area V5, also known as visual area MT (middle temporal), is a region of extrastriate visual cortex that is thought to play a major role in the perception of motion.

First sense to develop in the fetus

Touch is the first sense to develop in fetus.

The developing fetus responds to touch of the lips and cheeks by 8 weeks and to other parts of its body at 14 week.

The sense of taste may develop by 12 weeks and that of sound at 22-24 weeks.

Unique Mesencephalic Nucleus

The mesencephalic nucleus of the trigeminal nerve is Unique in many aspects. 

It is considered as the only place in the nervous system where the cell bodies of primary afferent fibers are found within the central nervous system rather than in ganglia outside the central nervous system.

The cell bodies located in the mesencephalic nucleus of the trigeminal are actually connected to afferents (sensory fibers) primarily from muscles for chewing.

It is considered as the center for the Corneal reflex though some say the Spinal nucleus as the center for the Corneal reflex.

Jaw Jerk

The jaw jerk reflex is a motor reflex used to test the status of a patient's trigeminal nerve

The mandible is tapped at a downward angle just below the lips at the chin while the mouth is held slightly open. Normally this reflex is absent or very slight. However in individuals with upper motor neuron lesions the jaw jerk reflex can be quite pronounced.

The reflex is MONOSYNAPTIC, with sensory neurons of the trigeminal MESENCEPHALIC NUCLEUS sending axons to the trigeminal motor nucleus, which in turn innervates the masseter.

This reflex is used to judge the integrity of the upper motor neurons projecting to the trigeminal motor nucleus. Both the sensory and motor aspects of this reflex are subserved by CN V.

It is not part of a standard neurological examination, being used rather if there are other signs of damage to the trigeminal nerve.

ONDINE'S CURSE

It also called congenital central hypoventilation syndrome (CCHS) or primary alveolar hypoventilation.

Patients afflicted with Ondine's curse classically suffer from respiratory arrest during sleep.

Till 2006, there were only about 200 known cases worldwide.

The disease used to be classified as a "neurocristopathy"or disease of the neural crest because part of the autonomic nervous system (such as sympathetic ganglia) derives from the neural crest.

Patients generally require tracheotomies and lifetime mechanical ventilation.

Now it is been shown that Biphasic Cuirass Ventilation can effectively be used without the need of a tracheotomy.

An alternative to a mechanical ventilator is Phrenic Nerve Pacing/diaphragm pacing.

TARLOV CYST

These represent one of the common type of arachnoid cyst.

They arise from the posterior rootlet (S2 and S3 most common) and form a dilated nerve root sleeve as a normal variant.

They can cause sacral erosion and may communicate with the thecal sac.

HSV Encephalitis in Children

• In children and neonates, herpes simplex virus type 2 (HSV-2) accounts for 80-90% of neonatal and almost all congenital infections.
• In neonates, HSV-2 typically involves the periventricular white matter and the meninges, with sparing of the medial temporal and inferior frontal lobes.

HSV Encephalitis in Adults

• In adults, herpes simplex virus type 1 (HSV-1) accounts for 95% of all fatal cases of sporadic encephalitis and usually results from reactivation of the latent virus.
• An isolated case report of an immunocompromised adult patient developing HSV-2 infection has been described.
• Adult HSV-1 encephalitis often results from reactivation of latent HSV in the trigeminal ganglion. The virus spreads along the orbitofrontal and temporal meningeal branches of this cranial nerve and then to the anterior and middle cranial fossa. Atypical spread can occur when cranial nerves IX and X are involved. 
• The virus has a predilection for the limbic system, involving one or both temporal lobes, and often involving the hippocampus, parahippocampus, and amygdala. Frontal and parietal spread also can occur.

10 Myths in Neurosurgery

Myth 1: Head elevation is beneficial in the treatment of elevated intracranial pressure.

Myth 2: Hyperventilation (induced hypocapnia) is useful to treat elevated intracranial pressure.

Myth 3: Glucocorticoids are beneficial in the treatment of brain injury.

Myth 4: Antihistamines (H2 blockers, eg, cimetidine) should be used to avoid stress gastritis.

Myth 5: Shaving the operative site reduces infection.

Myth 6: Following anterior cervical discectomy (ACD), a fusion procedure is required.

Myth 7: Congenital disorders such as neural tube defects and hydrocephalus are not preventable.

Myth 8: Primary brain tumors do not metastasize.

Myth 9: Knowledge of neuroanatomy will allow the surgeon to avoid iatrogenic neurological deterioration.

Myth 10: The "Brain" is the surgical domain of the neurosurgeon.

UNINDENTIFIED BRIGHT OBJECTS IN BRAIN

30% to 60% of patients with Type I Neurofibramatosis (NF1)  demonstrate hyperintense lesion on T2-weighted MRI in the basal ganglia, thalamus, cerebellum, and brain stem. These lesion are called un-identified bright objects ( UBO'S).
An association was demonstrated between these lesions and learning disabilities in children with NF1.
Pathology of these lesion showed increased water content but not dysplasia or hamartoma.

PARANEOPLASTIC CEREBELLAR DEGENERATION

It is the most common remote effect of neoplasm affecting the brain.
It is associated with lung, ovarian, and breast Ca and Hodgkin’s disease.
Histopathologically, there is a severe loss of Purkinje cells.
Two main antibodies are found in patient’s sera and CSF; namely Yo and Hu antibodies.
The symptoms usually progress rapidly to severe and symmetric truncal and limb ataxia with dysarthria and nystagmus.
Cerebellar sypmtoms may improve in some patients when causative neoplasms are removed.

Autism and yawning

Children with autism spectrum disorder are not as susceptible to contagious yawning as other children.

(Source: Senju, A., et al., Absence of contagious yawning in children with autism spectrum disorder, Biology Lett., August 14, 2007 (DOI 10.1098/rsbl.2007.0337).

Egaz Moniz, Antonio

Nobel Prize winner Antonio Egaz Moniz, who introduced the prefrontal lobotomy, was the Portuguese ambassador to Spain in 1917. (Source: Meyers, M.A., Happy Accidents. Serendipity in Modern Medical Breakthroughs, New York: Arcade Publishing, 2007.)

He also introduced the technique of cerebral angiography.

Speed of Transmission

Information travels in the nerves at speeds up to 268 miles per hour (429 kilometers/hour).

Sleep, Death and Dreams

1. In Greek mythology Sleep (Hypnos), Death (Thanatos), and Dreams (Oniros) were children of the goddess Night (Nyx)
2. Neglect or Forgetfulness (Lethe) and Pain (Algos) were grandchildren of the Night (Nyx). (Source: Ture et al., The art of alleviating pain in Greek mythology, (Neurosurgery, 56:178-185, 2005.)

Neuro Philately in India

Several countries have issued postage stamps with pictures of famous neuroscientists.

India till date don't have a postage stamp in relation to neuroscience but for a five rupee stamp about Drug addiction.

Missing 1st Spinal nerve

The first cervical dorsal spinal nerve and dorsal root ganglia are missing in 50% of all people. (Source: Schwartz, E.D. and Flanders, A.E., Spinal trauma: imaging, diagnosis, and management, Philadelphia: Lippincott Williams & Wilkins, 2007.)

Record for Stay without sleeping

In 1965, Randy Gardner set the world record for staying awake: 264 continuous hours (about 11 days).

In Biopsychology (by J.P.J. Pinel, Boston: Allyn and Bacon, 2000, p. 322), the record for time awake is attributed to Mrs. Maureen Weston. She apparently spent 449 hours (18 days, 17 hours) awake in a rocking chair.

The Guinness Book of World Records [1990] has the record belonging to Robert McDonald who spent 453 hours, 40 min in a rocking chair.

Lyme disease

Lyme disease, or borreliosis, is an emerging infectious disease caused by at least three species of bacteria belonging to the genus Borrelia.

Even pets (and wild animals) can get Lyme disease. Dogs, cats, horses, mice, cattle, deer, squirrels, opossum and raccoons can be infected. Many wild animals infected by the bacteria that cause Lyme disease do not show any symptoms. Dogs, however, may develop a fever and have pain in the joints. This can cause them to limp when they walk.

US President George W. Bush was treated for Lyme disease in August, 2006.

Cerebral Cortex

The human cerebral cortex has an area of about 2.5 square feet, has 25 billion neurons, is interconnected by over 100,000 kilometers of axons and receives 300 trillion synapses.

The Edwin Smith surgical papyrus, written about 1,700 B.C., contains the first recorded use of the word "brain."

In 1891, Wilhelm von Waldeyer coined the term "neuron."

Collodion

Collodion is a solution of nitrocellulose in ether or acetone, sometimes with the addition of alcohols. Its generic name is pyroxylin solution. It is highly flammable. As the solvent evaporates, it dries to a celluloid-like film.

It was discovered about 1846 by the French chemist and writer Louis Ménard.

Celloidin is a pure type of pyroxylin used to embed specimens which will be examined under a microscope.

Cytoarchitectonics

Cytoarchitectonics connotes the study of the cellular composition of the body's tissues under the microscope. Applied particularly to the study of the central nervous system, cytoarchitectonics is one of the ways to parse the brain (along with gross anatomy, topography, receptor-binding autoradiography, immunohistochemistry, etc.), by obtaining sections of the brain and staining them with chemical agents that reveal how nerve cell bodies (or neurons) are "stacked" into layers.

The study of the parcellation of nerve fibers (primarily axons) into layers forms the subject of myeloarchitectonics an approach complementary to cytoarchitectonics.

The birth of the cytoarchitectonics of the human cerebral cortex is credited to the Viennese psychiatrist Theodor Meynert (1833-1892), who in 1867 noticed regional variations in the histological structure of different parts of the gray matter in the cerebral hemispheres.

Einstein's brain

Einstein's brain was removed, weighed and preserved by Thomas Stoltz Harvey, the pathologist who performed the autopsy on Einstein. He claimed he hoped that cytoarchitectonics would reveal useful information.

Harvey injected 10% formalin through the internal carotid arteries and afterwards suspended the intact brain in 10% formalin. Harvey photographed the brain from many angles. He then dissected it into roughly 240 blocks (each about 10cm3) and encased the segments in a plastic-like material called celloidin.

Albert Einstein's brain

The brain of the great physicist Albert Einstein weighed 1,230 grams. This is far below the average brain weight of 1,400 grams.

Scientific studies have suggested that regions involved in speech and language are smaller, while regions involved with numerical and spatial processing are larger. Other studies have suggested an increased number of Glial cells in Einstein's brain.