Final answer:
The primary somatosensory cortex is organized in a topographical manner, where each body part's cortical space reflects its sensory sensitivity and discrimination—represented in the sensory homunculus. The hands and face have the largest cortical representation. The motor cortex is similarly organized, with fine movement areas, like fingers, having greater representation.
Step-by-step explanation:
Organization of the Primary Somatosensory Cortex
The primary somatosensory cortex is organized topographically, meaning it maintains a sensory representation of the body. This is called a sensory homunculus. Areas 1, 2, and 3 receive tactile sensory information from the thalamus. Not all body parts are equally represented. The size of the brain representation corresponds to the sensitivity of the body region, not the body region's size. Thus, body parts with higher sensitivity and finer sensory discrimination like the hands and face have larger cortical representation, leading to a distorted human figure when represented in the sensory homunculus.
Differences in Representation
Differences in the somatosensory cortex representation arise due to the different levels of sensory input from various body parts. The parts of the body that provide more precise and detailed sensory information, such as fingertips and lips, take up more space in the somatosensory cortex. The motor cortex has a similar organization, known as the motor homunculus, where body areas requiring precise and fine motor control, like fingers and facial muscles, are overrepresented relative to the rest of the body.