posterior parietal cortex

Examples of posterior parietal cortex in the following topics:

• 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.

• Association Areas

  • Associative areas of the cortex integrate current states with past states to predict proper responses based on sets of stimuli.
  • The parietal, temporal, and occipital lobes, all located in the posterior part of the cortex, organize sensory information into a coherent perceptual model of our environment centered on our body image.
  • The association areas are organized as distributed networks, and each network connects areas distributed across widely spaced regions of the cortex.
  • For example, a patient with a lesion in the parietal-temporal-occipital association area has an agraphia, which means he is unable to write although he has no deficits in motor skills.

• Cerebral Lobes

  • The cortex is divided into four main lobes: frontal, parietal, occipital, temporal.
  • The precentral gyrus, forming the posterior border of the frontal lobe, contains the primary motor cortex, which controls voluntary movements of specific body parts.
  • The parietal lobe is a part of the brain positioned above (superior to) the occipital lobe and behind (posterior to) the frontal lobe.
  • This enables regions of the parietal cortex to map objects perceived visually into body coordinate positions.
  • Distinguish between the frontal, temporal, parietal, and occipital lobes of the cerebral cortex

• 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.
  • Based on surface appearance, three lobes can be distinguished in the cerebellum: the flocculonodular lobe, anterior lobe (above the primary fissure), and the posterior lobe (below the primary fissure).
  • The medial zone of the anterior and posterior lobes constitutes the spinocerebellum, also known as the paleocerebellum.
  • 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.

• Somatic Sensory Pathways

  • In the case of touch and certain types of pain, the third neuron has its cell body in the ventral posterior nucleus of the thalamus and ends in the postcentral gyrus of the parietal lobe.
  • One major target within the brain is the postcentral gyrus in the cerebral cortex.
  • The primary somatosensory area in the human cortex is located in the postcentral gyrus of the parietal lobe.
  • For example, there is a large area of cortex devoted to sensation in the hands, while the back has a much smaller area.
  • This is a pictorial representation of the anatomical divisions of the primary motor cortex and the primary somatosensory cortex; namely, the portion of the human brain directly responsible for the movement and exchange of sensory and motor information of the body.

• Fontanels

  • The cranium of a newborn consists of five main bones: two frontal bones, two parietal bones, and one occipital bone.
  • At birth, the skull features a small posterior fontanelle (an open area covered by a tough membrane) where the two parietal bones adjoin the occipital bone (at the lambda).
  • The much larger, diamond-shaped anterior fontanelle—where the two frontal and two parietal bones join—generally remains open until a child is about two years old.
  • The more anterior one is the sphenoidal (between the sphenoid, parietal, temporal, and frontal bones), while the more posterior one is the mastoid (between the temporal, occipital, and parietal bones) .
  • This image shows the location of the anterior (frontal) and posterior fontanelles.

• Neural Mechanisms (Cortex)

  • The primary motor cortex is the neural center for voluntary respiratory control.
  • The center for diaphragm control is posterior to the location of thoracic control (within the superior portion of the primary motor cortex).
  • The posterior thoracic nerves: These nerves stimulate the intercostal muscles located around the pleura.
  • 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.

• Overview of the Cerebrum

  • Each hemisphere of the mammalian cerebral cortex can be broken down into four functionally and spatially defined lobes: frontal, parietal, temporal, and occipital.
  • Two of the parietal lobe's main functions are processing somatosensation (touch sensations such as pressure, pain, heat, cold) and proprioception (the sense of how parts of the body are oriented in space).
  • Speech comprehension is attributed to Wernicke's area, at the temporal-parietal lobe junction.
  • 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.

• The Brain

  • As a rule, the smaller the cerebrum, the less convoluted the cortex.
  • The cortex of a rat or mouse is almost completely smooth.
  • The cortex of a dolphin or whale, on the other hand, is more convoluted than the cortex of a human.
  • Anatomists conventionally divide each hemisphere into four lobes: the frontal (control of specialized motor control, learning, planning, and speech), parietal (control of somatic sensory functions), occipital (control of vision), and temporal lobes (control of hearing and some speech).
  • The only exception is the border between the frontal and parietal lobes, which is shifted backward from the corresponding suture to the central sulcus.

• General Organization of the Somatosensory System

  • Tertiary neurons have cell bodies in the thalamus and project to the postcentral gyrus of the parietal lobe, forming a sensory homunculus in the case of touch.
  • The primary somatosensory area of the human cortex is located in the postcentral gyrus of the parietal lobe.
  • The surface area of cortex dedicated to a body part correlates with the amount of somatosensory input from that area.
  • Brain: The postcentral gyrus contains Brodmann areas (BA) 3a, 3b, 1, and 2 that make up the somatosensory cortex.
  • The surface area of cortex dedicated to a body part correlates with the amount of somatosensory input from that area.