primary auditory cortex

Examples of primary auditory cortex in the following topics:

• Sensory Areas

  • Parts of the cortex that receive sensory inputs from the thalamus are called primary sensory areas.
  • The primary somatosensory cortex, located across the central sulcus and behind the primary motor cortex, is configured to generally correspond with the arrangement of nearby motor cells related to specific body parts.
  • The primary auditory cortex is located on the transverse gyri that lie on the back of the superior temporal convolution of the temporal lobes.
  • 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.

• Human Language and the Brain

  • Wernicke's area, located in the cerebral cortex, is the part of the brain involved in understanding written and spoken language.
  • The primary auditory cortex, located in the temporal lobe and connected to the auditory system, is organized so that it responds to neighboring frequencies in the other cells of the cortex.
  • The areas of the brain necessary for processing language: Broca's area, Wernicke's area, the primary motor cortex, the posterior middle temporal gyrus, and the middle and posterior superior temporal gyrus.

• 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.
  • Adjacent areas in the superior, posterior, and lateral parts of the temporal lobes are involved in high-level auditory processing.
  • The temporal lobe is involved in primary auditory perception such as hearing and holds the primary auditory cortex.
  • The superior temporal gyrus includes an area where auditory signals from the ear first reach the cerebral cortex and are processed by the primary auditory cortex in the left temporal lobe.

• Thalamus

  • 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.
  • Similarly, the medial geniculate nucleus acts as a key auditory relay between the inferior colliculus of the midbrain and the primary auditory cortex.
  • The ventral posterior nucleus is a key somatosensory relay, which sends touch and proprioceptive information to the primary somatosensory cortex.

• Cerebral Hemispheres and Lobes of the Brain

  • It processes sensory input including auditory information, language comprehension, and naming.
  • The left temporal lobe holds the primary auditory cortex, which is important for processing the semantics of speech.
  • The visual cortex receives raw sensory information through sensors in the retina of the eyes, which is then conveyed through the optic tracts to the visual cortex.
  • Damage to the primary visual cortex (located on the surface of the posterior occipital lobe) can cause blindness, due to the holes in the visual map on the surface of the cortex caused by the lesions.
  • The parietal lobe is comprised of the somatosensory cortex and part of the visual system.

• Transduction of Sound

  • The inner hair cells are the primary auditory receptors and exist in a single row, numbering approximately 3,500.
  • Their bending results in action potentials in the hair cells, and auditory information travels along the neural endings of the bipolar neurons of the hair cells (collectively, the auditory nerve) to the brain.
  • The auditory system is very refined, and there is some modulation or “sharpening” built in.
  • The inner hair cells are most important for conveying auditory information to the brain.
  • The afferent, bipolar neurons that convey auditory information travel from the cochlea to the medulla, through the pons and midbrain in the brainstem, finally reaching the primary auditory cortex in the temporal lobe.

• Motor Areas

  • The motor areas of the brain are located in both hemispheres of the cortex.
  • Primary motor cortex: Main contributor to the generation of neural impulses that control the execution of movement.
  • Premotor cortex: Located anterior to the primary motor cortex and responsible for some aspects of motor control.
  • It is located on the midline surface of the hemisphere anterior to the primary motor cortex.
  • $$Topography of the human motor cortex, including the premotor cortex, SMA, primary motor cortex, primary somatosensory cortex, and posterior parietal cortex.

• Parts of the Cerebellum

  • 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).
  • 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.

• Visual Processing

  • When visual signals leave the thalamus, they travel to the primary visual cortex at the rear of the brain.
  • From the visual cortex, the visual signals travel in two directions.
  • Another important visual route is a pathway from the retina to the superior colliculus in the midbrain, where eye movements are coordinated and integrated with auditory information.

• 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 inferior portion of the primary motor cortex may be involved in controlled exhalation.
  • 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.