The frontal lobe sits at the very front of the brain, directly behind your forehead. It’s the largest of the brain’s four main lobes, making up an estimated 25% to 40% of the cerebral cortex. That wide range exists because the brain doesn’t have sharp dividing lines between regions, so researchers draw the boundaries slightly differently depending on the study.
Exact Position and Boundaries
Each hemisphere of the brain has its own frontal lobe, one on the left and one on the right. They occupy the most forward (anterior) portion of each hemisphere. Two major grooves in the brain’s surface define where the frontal lobe ends and neighboring lobes begin. The central sulcus, a deep fold running roughly from ear to ear across the top of the brain, separates the frontal lobe from the parietal lobe behind it. The lateral sulcus (sometimes called the Sylvian fissure), a prominent groove along the side of the brain, separates the frontal lobe from the temporal lobe below it.
If you placed your hand on your forehead and slid it back toward the crown of your head, you’d be tracing the general territory of the frontal lobe underneath the skull. It extends from the very front of the brain all the way back to roughly the midpoint of the top of your head.
Key Regions Inside the Frontal Lobe
The frontal lobe isn’t one uniform structure. It contains several distinct areas, each handling different jobs. Moving from back to front, the major zones are:
- Primary motor cortex: A strip of tissue running along the back edge of the frontal lobe, right in front of the central sulcus. This is where your brain sends signals to move specific muscles throughout your body. Different spots along this strip control different body parts.
- Premotor cortex and supplementary motor area: Sitting just in front of the primary motor cortex, these regions help plan and coordinate movements before you execute them. They’re involved in sequencing complex actions like reaching for a cup or playing an instrument.
- Prefrontal cortex: The large region at the very front of the frontal lobe, behind the forehead. This is the area most associated with personality, decision-making, problem-solving, impulse control, and working memory. It sends instructions back to the motor areas when you decide to act on a plan.
- Orbitofrontal cortex: Located on the underside of the frontal lobe, just above the eye sockets (orbits). This area processes reward and punishment signals. It integrates taste, smell, touch, and visual information to help you evaluate whether something is pleasant or unpleasant, and it plays a role in adjusting your behavior when circumstances change. Damage here can make it difficult to correct responses that are no longer appropriate, affecting social behavior and emotional regulation.
Broca’s Area and Language
One of the most well-known regions in the frontal lobe is Broca’s area, located in the lower part of the left frontal lobe in about 95% of people. It sits just in front of the motor cortex that controls the mouth and tongue. Broca’s area occupies two small ridges of the inferior frontal gyrus and is critical for producing speech. When this area is damaged, typically by a stroke, people can often understand language but struggle to form words and sentences fluently. Interestingly, the corresponding spot in the left hemisphere is physically larger than its mirror region on the right side, reflecting this specialization for language.
Blood Supply to the Frontal Lobe
The frontal lobe receives blood from two major arteries. The middle cerebral artery supplies most of the outer (lateral) and lower surfaces, feeding areas like Broca’s area, the frontal eye fields (which control deliberate eye movements toward the opposite side), and parts of the motor and sensory cortex for the face and arm. The anterior cerebral artery supplies the inner (medial) surfaces, including portions of the prefrontal cortex and the motor areas for the legs.
This is why strokes affecting different arteries produce very different symptoms. A blockage in the middle cerebral artery can cause difficulty speaking and weakness on one side of the face or arm, while a blockage in the anterior cerebral artery more often affects leg movement and aspects of personality or motivation.
What Frontal Lobe Location Means for Function
The frontal lobe’s position at the front of the skull makes it particularly vulnerable to head injuries, especially from falls and car accidents where the brain slams forward against the inside of the skull. Because the prefrontal cortex and orbitofrontal cortex sit right behind the forehead and above the bony ridges of the eye sockets, even moderate impacts can affect personality, judgment, and emotional control.
The frontal lobe is also the last part of the brain to fully mature. While researchers define the exact timeline differently, the prefrontal cortex continues developing well into a person’s mid-20s. This extended development helps explain why teenagers and young adults are more prone to impulsive decisions and risk-taking: the region responsible for weighing consequences and reining in impulses is still being fine-tuned.