The cerebrum is the largest part of the human brain. It comprises the five cerebral lobes and all of the connections between the lobes and the rest of the brain.
The Sulci
Sulci are grooves or valleys that separate the raised gyri on the cerebral cortex. Two sulci you have to learn are the central sulcus and the lateral cerebral sulcus. The central sulcus separates the frontal lobe from the parietal lobes. The lateral cerebral sulcus (lateral sulcus) separates the temporal lobes from the frontal and parietal lobes.
The Cerebral Hemispheres
The brain has a left and a right cerebral hemisphere. For the most part, the right hemisphere controls the left side of the body and the left hemisphere controls the right side of the body. The corpus callosum is a large bridge of white matter (myelinated axons) that connects the two hemispheres so they can communicate.
The Cerebral Cortex
The cerebral cortex is a thin layer of gray matter (~3 mm) on the surface of the cerebrum whose primary functions are conscious actions. It is comprised of four superficial lobes and one deep lobe.
The Frontal Lobe
The frontal lobe is the largest cerebral lobe and is found in the front of the cerebrum – hence, its name. Its functions include, but are not limited to, conscious motor movements, problem-solving, judgment, language, memory, impulse control, and appropriate human behavior.
The Primary Motor Cortex
Its functions include, but are not limited to, conscious motor movements, problem-solving, judgment, language, memory, impulse control, and appropriate human behavior. The left motor cortex controls the muscles on the right side of the body and the right motor cortex controls the muscles on the left.
The Parietal Lobe
The parietal lobe is between the frontal and occipital lobes and is superior to the temporal lobe. It processes proprioception, visuospatial skills (map reading, understanding numbers, and knowing the location of your parked car without seeing it.
Proprioception is your ability, both consciously and unconsciously, to know where your body is in space. The parietal lobe is responsible for the conscious part, which is why you can scratch the back of your head.
The Somatic Sensory Cortex
The anterior gyrus of the parietal lobe sits directly after the central sulcus is home to the somatic sensory cortex (SSC) (also called the sensory cortex). The SSC processes conscious tactile (touch) sensations.
The Temporal Lobe
The temporal lobe is located just behind the temples, hence its name. It is separated from the lateral cerebral sulcus’s frontal and parietal lobes, the largest sulcus in the transverse plane. Its primary functions are processing auditory stimuli (hearing), facial recognition (right lobe only), memory, and language.
The Occipital Lobe
The posterior portion of the cerebral cortex is the primary visual cortex or occipital lobe. The occipital lobe receives sensory information from the optic nerve (CN #2). Vision is our most complex sense, and that is why a whole lobe is responsible for processing visual data. Color, shape, movement, and spatial visual sensations are combined in the occipital lobe to form images.
The Insula
The insula, meaning island, is a deep layer of cortex found under the lateral cerebral sulcus. The insula processes the conscious sensations of smell, taste, and balance. It allows us to perceive pain – pain is a perception, not a sensation – and our sense of self appears to originate in the insula.
The Language Centers
Language is almost exclusively a left hemisphere function. Anterior to the left posterior motor cortex is a small piece of cortex called Broca’s area. Broca’s area controls muscle movements needed for language expression and articulation. Wernicke’s area is in the posterior region of the upper left temporal lobe. It is responsible for speech comprehension – i.e., grammar, syntax.
