Chapter 14 - Section 14.5 - Integrative Functions of the Brain - Before You Go On - Page 541: 23

Somatotopy refers to the organization of the primary motor area (also known as the primary motor cortex) and the primary sensory area (also known as the primary somatosensory cortex) in a way that specific body parts are represented in distinct regions of these cortical areas. Here's a description of the somatotopy in each of these areas: 1. Primary Motor Area (Primary Motor Cortex): - Location: The primary motor area is located in the precentral gyrus of the frontal lobe, just in front of the central sulcus (which separates the frontal and parietal lobes). - Somatotopy: The primary motor cortex exhibits a somatotopic organization, meaning that it is mapped in a way that specific body parts are represented along the cortex. This representation is often referred to as the "motor homunculus" or "cortical homunculus." In the motor homunculus, different body parts are mapped to specific regions of the primary motor cortex based on their relative size and complexity of movement. - Function: Neurons in the primary motor cortex control voluntary muscle movements. The size of the representation of a body part in the motor cortex corresponds to the precision and complexity of movements that can be generated by that body part. For example, the hands and fingers have a larger representation compared to less dexterous body parts like the trunk or legs. 2. Primary Sensory Area (Primary Somatosensory Cortex): - Location: The primary sensory area is located in the postcentral gyrus of the parietal lobe, just behind the central sulcus. - Somatotopy: Similar to the primary motor cortex, the primary sensory cortex also exhibits somatotopy. It has a "sensory homunculus" or "cortical homunculus" representation, where different body parts are mapped to specific regions based on their sensitivity and the density of sensory receptors. This means that the sensitivity and precision of sensory perception vary across different body parts. - Function: Neurons in the primary somatosensory cortex process tactile, proprioceptive, and nociceptive (pain) information from the body. The size of the representation of a body part in the sensory cortex corresponds to the density and sensitivity of sensory receptors in that body part. For example, the hands and face have a larger representation because they are highly sensitive to touch and other sensory stimuli. In both the primary motor area and primary sensory area, the somatotopic organization reflects the brain's ability to control and perceive different parts of the body. This organization allows for precise and coordinated movements as well as accurate sensory perception and discrimination of various tactile and proprioceptive sensations.

Somatotopy refers to the organization of the primary motor area (also known as the primary motor cortex) and the primary sensory area (also known as the primary somatosensory cortex) in a way that specific body parts are represented in distinct regions of these cortical areas. Here's a description of the somatotopy in each of these areas: 1. Primary Motor Area (Primary Motor Cortex): - Location: The primary motor area is located in the precentral gyrus of the frontal lobe, just in front of the central sulcus (which separates the frontal and parietal lobes). - Somatotopy: The primary motor cortex exhibits a somatotopic organization, meaning that it is mapped in a way that specific body parts are represented along the cortex. This representation is often referred to as the "motor homunculus" or "cortical homunculus." In the motor homunculus, different body parts are mapped to specific regions of the primary motor cortex based on their relative size and complexity of movement. - Function: Neurons in the primary motor cortex control voluntary muscle movements. The size of the representation of a body part in the motor cortex corresponds to the precision and complexity of movements that can be generated by that body part. For example, the hands and fingers have a larger representation compared to less dexterous body parts like the trunk or legs. 2. Primary Sensory Area (Primary Somatosensory Cortex): - Location: The primary sensory area is located in the postcentral gyrus of the parietal lobe, just behind the central sulcus. - Somatotopy: Similar to the primary motor cortex, the primary sensory cortex also exhibits somatotopy. It has a "sensory homunculus" or "cortical homunculus" representation, where different body parts are mapped to specific regions based on their sensitivity and the density of sensory receptors. This means that the sensitivity and precision of sensory perception vary across different body parts. - Function: Neurons in the primary somatosensory cortex process tactile, proprioceptive, and nociceptive (pain) information from the body. The size of the representation of a body part in the sensory cortex corresponds to the density and sensitivity of sensory receptors in that body part. For example, the hands and face have a larger representation because they are highly sensitive to touch and other sensory stimuli. In both the primary motor area and primary sensory area, the somatotopic organization reflects the brain's ability to control and perceive different parts of the body. This organization allows for precise and coordinated movements as well as accurate sensory perception and discrimination of various tactile and proprioceptive sensations.