Examining the Brain’s Four Lobes: Frontal, Parietal, Temporal, and Occipital
Part of the Neuroscience For Dummies Cheat Sheet
The neocortex is divided into four major lobes: the frontal lobe, the parietal lobe, the temporal lobe, and occipital lobe. These lobes are further divided into different regions. The frontal lobes are involved with control of movement, from stimulation of individual muscles to abstract planning about what to do.
The parietal lobe processes visual, auditory and touch information. The temporal lobe is the primary area for early auditory processing and a high level visual processing area. The occipital lobe processes visual information and sends it to the parietal and temporal lobes.
The frontal lobe of the brain
The frontal lobe is concerned with executing behavior. This ranges from the control of individual muscles in the primary motor cortex to high level abstract planning about what to do. The frontal lobes are divided into different areas:
The prefrontal cortex: In humans, the prefrontal cortex takes up the majority of the frontal lobe. The prefrontal cortex is crucial for the performance of almost all skills requiring intelligence. The prefrontal cortex tends to be larger in primates than other mammals, and it’s larger in humans than in other primates. This is correlated with the amount of high level planning done by members of different species.
Most mammals operate mostly on instinct and don’t live in complexly differentiated social groups. Primates, on the other hand, have complex male and female hierarchies and may hatch plots against each other that span years of planning. Humans build tools, modify their environments for their own purposes, and have specific relationships with up to hundreds of other individuals (and this was even before Facebook).
The orbitofrontal cortex: This area is the anterior and medial part of the prefrontal cortex. The orbitofrontal cortex is essential for risk and reward assessment and for what might be called moral judgment. Patients with damage to this area may have normal or superior intelligence as assessed by IQ tests but lack even a rudimentary concept of manners or appropriate actions in social contexts; they also lose almost all risk aversion despite clear knowledge of bad consequences.
Primary motor cortex: The primary motor cortex is the strip of brain area just anterior to the central sulcus, the most posterior portion of the frontal lobe. The brain can take direct control of the muscles from the spinal cord. It does this through projections from the primary motor cortex. Neurons in the primary motor cortex travel down the spinal cord and synapse on the same motor neurons that mediate reflexes. In theory, this direct control allows far more flexibility and adaptability.
Premotor cortex: The job of the premotor cortex is to consciously monitor movement sequences, using sensory feedback. After the basal ganglia and prefrontal cortex select the goal, the premotor cortex coordinates the steps to reach that goal. Activity in the premotor cortex helps you learn what to pay attention to while you perform a complicated motor sequence and what to do when you get stuck at some particular point.
Think of the frontal cortex as polarized from anterior (front) to posterior (back). Farthest back, at the central sulcus, are neural wires going almost directly to muscles. In front of that are areas that organize and sequence movements. In front of that are abstract planning levels. At these abstract levels, for example, you select from a variety of different strategies that may involve completely different muscles, muscles sequences, or, as in the tennis shot, the decision to not move at all.
The brain's parietal lobe
The parietal lobe contains neurons that receive sensory information from the skin and tongue, and processes sensory information from the ears and eyes that are received in other lobes. The major sensory inputs from the skin (touch, temperature, and pain receptors) relay through the thalamus to parietal lobe.
The occipital lobe
The occipital lobe processes visual input that is sent to the brain from the retinas. The retinas project onto the posterior pole of the occipital lobe, called V1 (for visual area one), so that activity in different areas of V1 is related to whatever is in the image around your current point of gaze.
Subareas beyond V1 specialize in visual tasks such as color detection, depth perception, and motion detection. The sense of vision is further processed by projections from these higher occipital lobe areas to other areas in the parietal and temporal lobes, but this processing is dependent on early processing by the occipital lobe. (Researchers know this because damage to V1 causes blindness in that part of the visual field that projects there.)
The fact that the visual system gets an entire lobe for processing emphasizes the importance of high visual acuity and processing among our senses.
The temporal lobe
The brain's temporal lobe combines auditory and visual information. The superior (upper) and medial (central) aspect of the temporal lobe receives auditory input from the part of the thalamus that relays information from the ears. The inferior (lower) part of the temporal lobe does visual processing for object and pattern recognition. The medial and anterior parts of the temporal lobe are involved in very high-order visual recognition (being able to recognize faces, for example), as well as recognition depending on memory.