Friday, May 20, 2022

Which Lobe Of The Brain Interprets Visual Stimuli

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Pain In The Occipital Brain Lobe Region

Brain and Behavior – Vision and Visual Perception I

There are many different causes of pain in this region. Some of them include:

  • Nerve tension and stress. With prolonged tension, neck and back muscle spasms and neck pain occurs. Also, pain in the occipital brain region can be localized. The patient can diminish the pain by breathing calmly and deeply. If the pain does not stop after the patient feels relaxed, a visit to a doctor is obligatory.
  • Osteochondrosis of the cervical spine. This condition results in sharp pain in the back of the head. Specialized forms of gymnastics can help. However, the patient must see a neurologist.
  • High blood pressure. This condition can cause pain with a feeling of fullness. Pressure control is essential for extending ones lifetime. Contact a neurologist if you feel pain in the occipital part of your brain and suffer from blood pressure disorders.
  • Increased intracranial pressure. This serious condition is characterized by oppressive eye pain. The pain is localized in the occipital lobe. The patient must immediately see a doctor.

The occipital lobe is located in a triangle, the apex of which is the parietal lobe and the sides of the temporal lobes of the brain. The cerebellum is positioned below the occipital lobe. This brain part has a variable structure.

Its key function is processing visual information. The visual cortex, located on both hemispheres of the occipital lobe, provides binocular vision – the world seems vast and wide to the human eye.

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How Does The Occipital Lobe Interact With Other Areas Of The Body

No part of the brain is a standalone organ that can function without information from other parts of the body. The occipital lobe is no exception. Although its primary role is to control vision, damage to other brain regions and body parts can inhibit vision. Moreover, some evidence suggests that, when the occipital lobe is damaged, nearby brain regions may be able to compensate for some of its functions. The occipital lobe is heavily dependent on:

  • The eyes, particularly the retinas, which take in and process visual information to then be further processed by the occipital lobe.
  • The frontal lobe, which contains the brain’s motor cortex. Without motor skills, the eyes cannot move or take in information from surrounding regions.
  • The temporal lobe, which helps assign meaning to visual information, in addition to encoding it into memories.

The Case For Overlapping Substrates Of Visual Working Memory And Perception

With the advent of modern functional imaging, it has been possible to measure Blood Oxygenation Level Dependent signals in humans performing perceptual and working memory tasks. One common finding is that it is possible to decode the contents of working memory from BOLD signals in early visual areas . Yet, electrophysiological studies in monkeys find little evidence of persistent firing of action potential by single neurons . These functional imaging findings have been the motivation of a popular hypothesis that proposes early sensory areas are recruited, and may be necessary, for the maintenance of working memory representations . This hypothesis is known as the sensory recruitment hypothesis, and has been a matter of debate amongst neuroscientists investigating the topic . At first glance, the sensory recruitment hypothesis does not fully match the results of electrophysiological and lesion studies in non-human primates we have reviewed above. Below, we consider a few explanations for this mismatch.

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Seeing The Patterns In Visual Signals

How does the brain coordinate such a flood of information from the eyes? This is a job for the cortexspecifically, the intermediate layers of the primary visual cortex. Signals from the optic nerve pass through the lateral geniculate to the intermediate layers of the cortex, where any given cell receives impulses from either the right or the left eye. Small groups of cells responsive to one eye or the other form a striped pattern in the cortex, which can be made visible by injecting one eye of an anesthetized animal with a radioactive amino acid, exposing it to light, and developing the emitted radiation as a photographic image. The stripes, like the cell groups that respond to a particular orientation of line, are about half a millimeter in diameter.

One Region Two Functions: Brain Cells’ Multitasking May Be A Key To Understanding Overall Brain Function

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A region of the brain known to play a key role in visual and spatial processing has a parallel function: sorting visual information into categories, according to a new study by researchers at the University of Chicago.

Primates are known to have a remarkable ability to place visual stimuli into familiar and meaningful categories, such as fruit or vegetables. They can also direct their spatial attention to different locations in a scene and make spatially-targeted movements, such as reaching.

The study, published in the March issue of Neuron, shows that these very different types of information can be simultaneously encoded within the posterior parietal cortex. The research brings scientists a step closer to understanding how the brain interprets visual stimuli and solves complex tasks.

“We found that multiple functions can be mapped onto a particular region of the brain and even onto individual brain cells in that region,” said study author David Freedman, PhD, assistant professor of neurobiology at the University of Chicago. “These functions overlap. This particular brain area, even its individual neurons, can independently encode both spatial and cognitive signals.”

Freedman studies the effects of learning on the brain and how information is stored in short-term memory, with a focus on the areas that process visual stimuli. To examine this phenomenon, he has taught monkeys to play a simple video game in which they learn to assign moving visual patterns into categories.

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Visual Processing Isnt All One Way

This bottom-to-top processing of our visual world may seem the logical path, but it isnt the whole story. Such a ‘bottom-up‘ approach would be far too slow and laborious, but more importantly, it would render our visual world full of ambiguity and we would struggle to survive. Instead, our perception relies to a very large extent on our previous experience and other ‘top-down‘ mechanisms such as attention. QBI Professors Jason Mattingley and Stephen Williams are both studying how attention can alter visual processing, using cognitive and cellular approaches, respectively.

As an example of top-down processing, consider the image below:

Wuhazet – Henryk ychowski

Square A looks lighter, but is actually darker than square B. Clearly, our visual system is doing a terrible job at seeing reality. But that isnt its purpose. Instead, our brains are trying to make sense of what they are seeing, rather than seeking the truth.

In the case of the above image, we automatically see based on past experience light and dark squares arranged in a checkerboard fashion, with a centrally lit portion and a shadow cast around the edges. With all of this information, we interpret A as a light square in shadow, and B as a brightly lit dark square. It isnt reality, but it is the most likely explanation given all of our previous experience and the data at hand. This is how our visual system works, ultimately to help us understand the world and so promote our survival.

The Anatomy Of Attention

Positron emission tomography has done much in recent years to change general ideas about the anatomy of mental functions. In particular, PET scans have shown rather distinct localization of the mental operations involved in a task such as “work processing.” Under that general heading, it seems at first that many parts of the brain are active, but depending on the specific kind of processing required, activity appears highly focused in one or two areas. PET images of changes in blood flow to discrete areas of the brain make it clear that simply showing the experimental subject the written form of a word, and requiring no overt response, activates mainly the visual areas, in the occipital lobe. In PET imaging studies carried out by Posner and Marcus Raichle , subjects were shown groups of letters that conformed to English rules of construction but did not form a word in English these nonwords, as well as authentic English words, tended to activate a portion of the left occipital lobe that does not respond to mere strings of consonants or to strings of graphic forms that resemble letters.

From this work has emerged the finding that a shift of visual attention entails at least two steps: first disengaging the attention from one spot and then bringing it to bear on another location. It appears that the parietal lobe is important in the first step and the midbrain is more active in the second.

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The Cell Structure Of The Brain

The brain is made up of two types of cells: neurons and glial cells, also known as neuroglia or glia. The neuron is responsible for sending and receiving nerve impulses or signals. Glial cells are non-neuronal cells that provide support and nutrition, maintain homeostasis, form myelin and facilitate signal transmission in the nervous system. In the human brain, glial cells outnumber neurons by about 50 to one. Glial cells are the most common cells found in primary brain tumors.

When a person is diagnosed with a brain tumor, a biopsy may be done, in which tissue is removed from the tumor for identification purposes by a pathologist. Pathologists identify the type of cells that are present in this brain tissue, and brain tumors are named based on this association. The type of brain tumor and cells involved impact patient prognosis and treatment.

What Part Of The Brain Controls Vision

Brain and Behavior – Vision and Visual Perception II

Vision is an intricate function of the brain that extends from the front to the back of the head. To produce vision, the eyes record details and send it through the optic nerve to be processed by the occipital lobe. The brain also integrates other information, such as sensory stimuli, to result in the application of sight, such as picking up an item. Problems with vision, such as vision gaps, can result from damage to specific parts of the brain.

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Where Is The Primary Visual Cortex

Primary visual cortex .

The primary visual cortex is found in the occipital lobe in both cerebral hemispheres. It surrounds and extends into a deep sulcus called the calcarine sulcus. The primary visual cortex makes up a small portion of the visible surface of the cortex in the occipital lobe, but because it stretches into the calcarine sulcus, it makes up a significant portion of cortical surface overall. The primary visual cortex is sometimes also called the striate cortex due to the presence of a large band of myelinated axons that runs along the eges of the calcarine sulcus. These axons, referred to as the line of Gennari in reference to the first researcher who made note of their presence in the late 1700s, make the primary visual cortex appear striped .

Beta Effect And Phi Phenomenon

In the beta effect, our eyes detect motion from a series of still images, each with the object in a different place. This is the fundamental mechanism of motion pictures . In the phi phenomenon, the perception of motion is based on the momentary hiding of an image.

Beta effect: http://upload.wikimedia.org/wikipedia/commons/0/09/Phi_phenomenom_no_watermark.gif

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Which Lobe Of The Brain Interprets Visual Stimuli

Which Lobe Of The Brain Interprets Visual Stimuli. The cerebral cortex of the brain has four lobes, each with distinct functions. Which lobe of the brain interprets sensations felt in or on the body?

The temporal lobe of the brain is the site of auditory input and visual input combination. The temporal lobe also helps people understand and interpret language, so extensive temporal lobe damage may impede. It is located in the occipital lobe. The brain is divided into regions, areas, and lobes each responsible for a specific function. Visual stimuli exercise more influence on emotional perception than auditory stimuli, and there are taken together, behavioral and brain imaging techniques therefore show that visual stimuli one of the present authors knows of a young woman with cryptogenic right parietal lobe epilepsy and.

What Are Some Important Structures In The Temporal Lobe

Visual perception and processing

As one of just four lobes in the brain, the temporal lobe is less a discrete organ, and more of a home to numerous other structures. Some of the most important structures in the temporal lobe include:

  • Limbic lobe: This brain region actually intersects with several lobes, but interacts directly with the temporal lobe to influence the limbic system, including automatic emotional reactions such as the fight-or-flight response and the limbic system. The limbic lobe is home to key memory, learning, and attention processing structures such as the amygdala and hippocampus. This brain region also manages a number of automatic, unconscious bodily functions, as well as unconscious emotional states, such as sexual arousal and appetite.
  • Wernicke’s area: This brain region is associated with the understanding and processing of speech.
  • Broca’s area: This brain region aids in the production of speech, though some evidence suggests that, when Broca’s area is damaged, nearby regions may compensate. Together with Wernicke’s area, Broca’s area aids communication.

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The Primary Visual Cortex Is Located In And Around The Calcarine Fissure In The Occipital Lobe

First comes the cornea, the transparent, slightly convex outer surface at the centre of the eye. This brain structure is usually above the nasal cavity and below frontal lobe. Which lobe of the brain interprets sensations felt in or on the body? Visual information is received through the eyes but interpreted with the brain. Learn more about it here.

What Happens If The Occipital Lobe Is Damaged

The most obvious effect of damage to the occipital lobe is blindness, but occipital lobe damage can have other surprising effects:

  • Epilepsy: Some seizures occur in the occipital lobe, and occipital lobe damage increases vulnerability to seizures.
  • Difficulties with movement: Even if you are still able to move, changes in depth perception and vision can lead to inappropriate movements and difficulty navigating the visual field.
  • Difficulties perceiving colors, shape, dimension, and size.
  • Difficulty recognizing familiar objects or faces.
  • Hallucinations

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Pathways Of Information In The Visual System

Within the visual system, researchers seek to explain our seamless perception of a three-dimensional surround that contains color, movement, and shape, all assembled from the action of light on our two eyes. What takes place in the rest of the brain, beyond the 125 million rods and cones of each retina, to transmit nerve impulses and organize them into useful messages, recognizable forms, and meaningful scenes?

A basic organizing principle of the visual system is that of a hierarchy of information: a relatively large number of specialized cells at each stage supply information to a smaller number of cells at the next stage, which in turn have their own specialized function. The retinal rods are most attuned to dim light, the cones to bright light . Both rods and cones transmit impulses to another layer of the retina, which sends signals through the third layer to the many neuronal fibers that make up the optic nerve.

Each cell in the third layer that supplies the optic nerve already represents the confluence of signals from thousands of rods and cones over about 1 square millimeter of the retina. The square millimeter thus covered is called the receptive field of that cell. The optic nerve in turn supplies a large amount of pooled information to the lateral geniculate nucleus, which then relays signals to the primary visual cortex.

Building Our Visual World Step By Step

Visual Perception How It Works

Our visual cortex is not uniform, and can be divided into a number of distinct subregions. These subregions are arranged hierarchically, with simple visual features represented in ‘lower’ areas and more complex features represented in ‘higher’ areas.

At the bottom of the hierarchy is the primary visual cortex, or V1. This is the part of visual cortex that receives input the thalamus. Neurons in V1 are sensitive to very basic visual signals, like the orientation of a bar or the direction in which a stimulus is moving. In humans and cats , neurons sensitive to the same orientation are located in columns that span the entire thickness of the cortex.

That is, all neurons within a column would respond to a horizontal bar. In a neighbouring column, all neurons would respond to oblique but not horizontal or vertical bars . As well as this selectivity for orientation, neurons throughout most of V1 respond only to input from one of our two eyes. These neurons are also arranged in columns, although they are distinct from the orientation columns. This orderly arrangement of visual properties in the primary visual cortex was discovered by David Hubel and Torsten Wiesel in the 1960s, for which they were later awarded the Nobel Prize.

Orientation columns in primary visual cortex, as viewed from above. All neurons within a column respond preferentially to bars of a specific orientation, denoted here by colour.Crair et als/Wikimedia

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Pathology In The Attention System And Beyond

The case files of illnesses and injuries to the brain that interfere with attention systems contain many curious observations . In these kinds of cases, the symptom makes its appearance on the side opposite the brain hemisphere that is injured. The location of such injuries is often the parietal lobe, and the system most affected by them is the posterior attention system, which is sensitive to location in space.

One other system for attention seems from early evidence to involve the frontal lobe of the right hemisphere. Injury in this area appears to cause difficulty in so-called vigilance tasks: monitoring a visual field over a long time while on the lookout for rather subtle or infrequent signals. Interestingly, scanning shows that the right frontal cortex is highly active during such tasks but the anterior cingulate gyrus is quite inactivein fact, it operates below its baseline level of activity. But when the experiment is changed so that the signals become more frequent, the cingulate gyrus increases its participation. This pattern suggests to Posner and others that activity of the vigilance network might effectively inhibit the anterior cingulate gyrus, allowing targetswhen they occurto have ready access to higher levels of attention.

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