# The Cerebrum --- The **cerebrum** is the largest and most distinctive part of the [[brain]]. It is the location of conscious thought processes and higher and complex [[intelligence|intellectual]] function. It can be divided largely up into **grey matter**, which is comprised of neuron bodies, and **white matter** which is comprised of the axons of the neurons. ![[grey and white matter.png]] ## Grey Matter The grey matter of the cerebrum is comprised of the cerebral cortex on the outside and some other structures such as the parts of the [[limbic system]], the **insula** and some of the [[basal ganglia]], which are located deep inside the white matter. ### The Cerebral Cortex The **cerebral cortex** is the outer grey matter that surrounds the rest of the cerebrum. The unique topography of the cerebral cortex can be described by the **gyri** (sing: **gyrus***)—or the ridges—and the **sulci** (sing: **sulcus**)—or the valleys between the gyri. Particularly deep sulci are called **fissures**. The formation of the gyri and sulci are surprisingly regular from person to person, and many have specific names. ![[gyri and sulci.png]] The cortex is also divided into six (pairs of) lobes, which all serve a general, relatively specialized function. They are generally bounded by specific "landmarks" of gyri. - The **frontal lobe** is located most anteriorly, right behind the forehead. It is generally the "high reasoning" area, and is the part of the brain for problem solving, judgment and reasoning, as well as speaking. - The **parietal lobe** is located most superiorly, under the crown of the skull, and it's main job is for processing [[afferent nervous system|sensory]] information. - The **temporal lobe** is located to the sides of the brain, and it is in charge of [[ears|hearing]] and [[nose|smell]]. - The **occipital lobe** is located in the very back of the brain and it is in charge of [[vision]]. ### Important Cortices The whole of the grey matter is called the "cerebral cortex", but within that cortex there are even smaller, more specialized cortices that are pretty important. A cortex in this context means any part of the grey matter that's involved in higher order functions. - The **prefrontal cortex** is located in the frontal lobe, and is the responsible for judgment and reasoning. The prefrontal cortex is virtually absent from [[infant|infants]], and is not fully developed until around age 25. The impulsivity in [[life-span development|adolescents]] is related in part to an increase in the speed of thinking (due to increased [[myelination]]) and a still-underdeveloped prefrontal cortex. It is a highly important cortex in the field of [[psychology]] - The **premotor cortex** conducts learned movements or behaviors. It's our "muscle memory", which helps us do things like ride a bike or type on a keyboard. - The **primary motor cortex** and **primary somatosensory cortex** are located in the *pre* and *post*central gyrus respectively. These are where our body maps the motor and sensory information for specific areas of the body, in structures called **homunculi**. ![[cerebral lobes.png]] ## White Matter The **white matter** makes up the bulk of the cerebrum. It has a white appearance (hence the name) because it is made up of [[myelination|myelinated]] fibers (or long cell axons). There are several different types of fibers: - **Association fibers** connect different parts of the brain together. - **Projection fibers** take [[afferent nervous system|sensory]] information received by the brain from the "post office" [[thalamus]], and sends that information to where it needs to go. - **Commissural fibers** are what make up the [[corpus callosum]], which connects the two halves of the brain. ___