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11.8A: Sensory Areas

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    7638
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    Sensory areas of the brain receive and process sensory information, including sight, touch, taste, smell, and hearing.

     

    LEARNING OBJECTIVES

     

    Describe the sensory areas of the cerebral cortex

     

    KEY TAKEAWAYS

    Key Points

     

    • The cortex can be divided into three functionally distinct areas: sensory, motor, and associative.
    • The main sensory areas of the brain include the primary auditory cortex, primary somatosensory cortex, and primary visual cortex.
    • In general, the two hemispheres receive information from the opposite side of the body. For example, the right primary somatosensory cortex receives information from the left limbs, and the right visual cortex receives information from the left eye.
    • Sensory areas are often represented in a manner that makes topographical sense.

     

    Key Terms

     

    • calcarine sulcus: An anatomical landmark located at the caudal end of the medial surface of the brain.
    • primary somatosensory cortex: The main sensory receptive area for the sense of touch.
    • primary auditory cortex: A region of the brain that processes sound and thereby contributes to our ability to hear.
    • primary visual cortex: Located in the posterior pole of the occipital cortex, the simplest, earliest cortical visual area. It is highly specialized for processing information about static and moving objects and is excellent in pattern recognition.

    Sensory areas are the areas of the brain that receive and process sensory information. The cerebral cortex is connected to various subcortical structures such as the thalamus and the basal ganglia. Most sensory information is routed to the cerebral cortex via the thalamus. Olfactory information, however, passes through the olfactory bulb to the olfactory cortex, bypassing the thalamus. The cortex is commonly described as composed of three parts: sensory, motor, and association areas. Parts of the cortex that receive sensory inputs from the thalamus are called primary sensory areas. Each of the five senses relates to specific groups of brain cells that categorize and integrate sensory information.

    The Five Sensory Modalities

    The five commonly recognized sensory modalities, including sight, hearing, taste, touch, and smell, are processed as follows:

    Somatosensory System

    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.

    Taste

    The primary gustatory area is near the face representation within the postcentral gyrus.

    Olfaction

    The olfactory cortex is located in the uncus, found along the ventral surface of the temporal lobe. Olfaction is the only sensory system that is not routed through the thalamus.

    Vision

    The visual area is located on the calcarine sulcus deep within the inside folds of the occipital lobe.

    Hearing

    The primary auditory cortex is located on the transverse gyri that lie on the back of the superior temporal convolution of the temporal lobes.

    Organization of Sensory Maps

    In general, each brain hemisphere receives information from the opposite side of the body. For example, the right primary somatosensory cortex receives information from the left limbs, and the right visual cortex receives information from the left eye. The organization of sensory maps in the cortex reflects that of the corresponding sensing organ, in what is known as a topographic map. Neighboring points in the primary visual cortex, for example, correspond to neighboring points in the retina. This topographic map is called a retinotopic map.

    Similarly, there is a tonotopic map in the primary auditory cortex and a somatotopic map in the primary sensory cortex. This somatotopic map has commonly been illustrated as a deformed human representation, the somatosensory homunculus, in which the size of different body parts reflects the relative density of their innervation.

    A cortical homunculus is a physical representation of the human body located within the brain. This neurological map of the anatomical divisions of the body depicts the portion of the human brain directly associated with the activity of a particular body part. Simply put, it is the view of the body from the brain’s perspective. Areas with lots of sensory innervation, such as the fingertips and the lips, require more cortical area to process finer sensation.

    This depiction of the sensory homunculus illustrates the cortical areas that are mapped to the genitals, foot, toes, hip, leg, trunk, neck, head, shoulder, arm, elbow, forearm, wrist, hand, fingers, eye, nose, face, lips, teeth, gums, jaw, tongue, and pharynx.

    Sensory Homunculus: Cortical Homunculus: A depiction of the human brain areas directly associated with the activity of a particular body part.