Brain lobes were originally a purely anatomical classification, but they have been shown to also be related to different brain functions. The telencephalon (cerebrum)—the largest portion of the human brain—is divided into lobes, similarly to the cerebellum. If not specified, the expression "lobes of the brain" refers to the telencephalon. There are four uncontested lobes of the telencephalon (Figure 1):
- Frontal lobe: conscious thought; damage can result in mood changes, personality differences, and difficulty planning. The frontal lobes are the most uniquely human of all the brain structures
- Parietal lobe: plays important roles in integrating sensory information from various senses, and in the manipulation of objects; portions of the parietal lobe are involved with visuospatial processing
- Occipital lobe: sense of sight; lesions can produce hallucinations
- Temporal lobe: senses of smell and sound, as well as processing of complex stimuli like faces and scenes
The Frontal Lobe
The frontal lobe is an area in the brain of mammals, located at the front of each cerebral hemisphere and positioned anterior to (in front of) the parietal lobe and superior and anterior to the temporal lobes. It is separated from the parietal lobe by a space between tissues called the central sulcus; it is separated from the temporal lobe by a deep fold called the lateral (Sylvian) sulcus. The precentral gyrus, forming the posterior border of the frontal lobe, contains the primary motor cortex, which controls voluntary movements of specific body parts.
The frontal lobe contains most of the dopamine-sensitive neurons in the cerebral cortex. The dopamine system is associated with reward, attention, short-term memory tasks, planning, and motivation. Dopamine tends to limit and select sensory information the thalamus sends to the fore-brain. A report from the National Institute of Mental Health says a gene variant that reduces dopamine activity in the prefrontal cortex is related to poorer performance that region during memory tasks; this gene variant is also related to slightly increased risk for schizophrenia.
The Parietal Lobe
The parietal lobe is a part of the brain positioned above (superior to) the occipital lobe and behind (posterior to) the frontal lobe. The parietal lobe integrates sensory information from different modalities, particularly determining spatial sense and navigation. For example, it comprises somatosensory cortex and the dorsal stream of the visual system. This enables regions of the parietal cortex to map objects perceived visually into body coordinate positions. Several portions of the parietal lobe are also important in language processing.
The Occipital Lobe
The two occipital lobes are the smallest of four paired lobes in the human cerebral cortex. Located in the rearmost portion of the skull, the occipital lobes are part of the forebrain. The cortical lobes are not defined by any internal structural features, but rather by the bones of the skull that overlie them. Thus, the occipital lobe is defined as the part of the cerebral cortex that lies underneath the occipital bone. The lobes rest on the tentorium cerebelli—a process of dura mater that separates the cerebrum from the cerebellum. They are structurally isolated in their respective cerebral hemispheres, separated by the cerebral fissure. At the front edge of the occipital there are several lateral occipital gyri separated by lateral occipital sulci.
The Temporal Lobe
The temporal lobe is a region of the cerebral cortex located beneath the lateral fissure on both cerebral hemispheres of the mammalian brain. The temporal lobes are involved in many different functions such as the retention of visual memories, processing sensory input, comprehending language, storing new memories, emotion, and deriving meaning. The temporal lobe contains the hippocampus and plays a key role in the formation of explicit long-term memory, modulated by the amygdala.
Adjacent areas in the superior, posterior, and lateral parts of the temporal lobes are involved in high-level auditory processing. The temporal lobe is involved in primary auditory perception, such as hearing and holds the primary auditory cortex. The superior temporal gyrus includes an area where auditory signals from the ear first reach the cerebral cortex and are processed by (primary auditory cortex) in the left temporal lobe. The areas associated with vision in the temporal lobe interpret the meaning of visual stimuli and establish object recognition. The underside (ventral) part of the temporal cortices appear to be involved in high-level visual processing of complex stimuli such as faces (fusiform gyrus) and scenes (parahippocampal gyrus). Anterior parts of this ventral stream for visual processing are involved in object perception and recognition.