visual cortex

Examples of visual cortex in the following topics:

• Sensory Areas

  • Most sensory information is routed to the cerebral cortex via the thalamus.
  • The visual area is located on the calcarine sulcus deep within the inside folds of the occipital lobe.
  • For example, the right primary somatosensory cortex receives information from the left limbs, and the right visual cortex receives information from the left eye.
  • Neighboring points in the primary visual cortex, for example, correspond to neighboring points in the retina.
  • Similarly, there is a tonotopic map in the primary auditory cortex and a somatotopic map in the primary sensory cortex.

• Optic (II) Nerve

  • The optic nerve (cranial nerve II) receives visual information from photoreceptors in the retina and transmits it to the brain.
  • It transmits visual information from the retina to the brain.
  • Most of the axons of the optic nerve terminate in the lateral geniculate nucleus (where information is relayed to the visual cortex), while other axons terminate in the pretectal nucleus and are involved in reflexive eye movements.
  • The optic nerve transmits all visual information including brightness perception, color perception, and contrast.
  • It also conducts the visual impulses that are responsible for two important neurological reflexes: the light reflex and the accommodation reflex.

• Thalamus

  • Its functions include relaying sensory and motor signals to the cerebral cortex and regulating consciousness, sleep, and alertness.
  • It is generally believed to act as a relay between a variety of subcortical areas and the cerebral cortex.
  • For the visual system, for example, inputs from the retina are sent to the lateral geniculate nucleus of the thalamus, which in turn projects to the primary visual cortex in the occipital lobe.
  • Each of the primary sensory relay areas receives strong back projections from the cerebral cortex.
  • The ventral posterior nucleus is a key somatosensory relay, which sends touch and proprioceptive information to the primary somatosensory cortex.

• Cerebral Lobes

  • The cortex is divided into four main lobes: frontal, parietal, occipital, temporal.
  • For example, it comprises the somatosensory cortex and the dorsal stream of the visual system.
  • This enables regions of the parietal cortex to map objects perceived visually into body coordinate positions.
  • The areas associated with vision in the temporal lobe interpret the meaning of visual stimuli and establish object recognition.
  • Anterior parts of this ventral stream for visual processing are involved in object perception and recognition.

• Parts of the Cerebellum

  • The surface of the cerebellum is covered with finely spaced parallel grooves, in striking contrast to the broad irregular convolutions of the cerebral cortex.
  • Like the cerebral cortex, the cerebellum is divided into two hemispheres.
  • Its primary connections are with the vestibular nuclei, although it also receives visual and other sensory input.
  • It receives proprioception input from the dorsal columns of the spinal cord (including the spinocerebellar tract) and from the trigeminal nerve, as well as from visual and auditory systems.
  • It receives input exclusively from the cerebral cortex (especially the parietal lobe) via the pontine nuclei (forming corticopontocerebellar pathways), and sends output mainly to the ventrolateral thalamus (in turn connected to motor areas of the premotor cortex and primary motor area of the cerebral cortex) and to the red nucleus.

• Overview of the Cerebrum

  • It is primarily involved in vision: seeing, recognizing, and identifying the visual world.
  • Damage to motor areas of cortex can lead to certain types of motor neuron disease.
  • Speech and language are mainly attributed to parts of the cerebral cortex.
  • The cerebral cortex is the outer layer depicted in dark violet.
  • Notice the folded structure of the cortex: the "valleys" of the cortex are known as sulci.

• Mapping the Primary Somatosensory Area

  • It is a visual representation of the concept of the body within the brain—that one's hand or face exists as much as a series of nerve structures or a neuron concept as it does in a physical form.
  • Each one shows a representation of how much of its respective cortex innervates certain body parts.
  • The primary somesthetic cortex (sensory) pertains to the signals within the postcentral gyrus coming from the thalamus, and the primary motor cortex pertains to signals within the precentral gyrus coming from the premotor area of the frontal lobes.
  • Typically, the area of the body corresponds to a point on the primary somatosensory cortex (postcentral gyrus).
  • Areas such as the appendages, digits, and face can draw their sensory locations upon the somatosensory cortex.

• Motor Areas

  • The motor areas of the brain are located in both hemispheres of the cortex.
  • Premotor cortex: Located anterior to the primary motor cortex and responsible for some aspects of motor control.
  • Posterior parietal cortex – Guides planned movements, spatial reasoning, and attention.
  • Various experiments examining the motor cortex map showed that each point in motor cortex influences a range of muscles and joints, indicating significant overlapping in the map.
  • $$Topography of the human motor cortex, including the premotor cortex, SMA, primary motor cortex, primary somatosensory cortex, and posterior parietal cortex.

• White Matter of the Cerebrum

  • White matter is composed of myelinated axons and glia and connects distinct areas of the cortex.
  • Other projection tracts carry signals upward to the cerebral cortex.
  • Superior to the brainstem, such tracts form a broad, dense sheet called the internal capsule between the thalamus and basal nuclei, then radiate in a diverging, fanlike array to specific areas of the cortex.
  • The corpus callosum (Latin: "tough body"), also known as the colossal commissure, is a wide, flat bundle of neural fibers beneath the cortex in the eutherian brain at the longitudinal fissure.
  • Other possible symptoms include impairments in mental and physical development, hand-eye coordination, and visual and auditory memory.

• Neural Mechanisms (Cortex)

  • The primary motor cortex is the neural center for voluntary respiratory control.
  • More broadly, the motor cortex is responsible for initiating any voluntary muscular movement.
  • Different parts of the cerebral cortex control different forms of voluntary respiration.
  • Topography of the primary motor cortex, on an outline drawing of the human brain.
  • Each part of the primary motor cortex controls a different part of the body.