The Neuroscience on the Web Series:
CMSD 620 Neuroanatomy of Speech, Swallowing and Language
CSU, Chico, Patrick McCaffrey, Ph.D. |
Chapter 4 Cerebral Lobes, Cerebral Cortex, and Brodmann's Areas |
The Cerebral LobesEach cerebral hemisphere is divided into four lobes; the frontal, parietal, temporal, and the occipital.The Frontal Lobe is the most anterior lobe of the brain. Its posterior boundary is the fissure of Rolando, or central sulcus, which separates it from the parietal lobe. Inferiorly, it is divided from the temporal lobe by thefissure of Sylvius which is also called the lateral fissure.This lobe deals with with higher level cognitive functions like reasoning and ...view middle of the document...
It controls the voluntary movements of skeletal muscles; cell bodies of the pyramidal tract are found on this gyrus.The amount of tissue on the precentral gyrus that is dedicated to the innervation of a particular part of the body is proportional to the amount of motor control needed by that area, not just its size. For example, much more of the motor strip is dedicated to the control of speech (tongue, lips, jaw, velum, pharynx, and larynx) than to the trunk.The premotor area or supplemental motor area is immediately anterior to the motor strip. It is responsible for the programming for motor movements. It does not, however program the motor commands for speech as these are generated in Broca's area which is also located in the frontal lobe.The most anterior part of the frontal lobe is involved in complex cognitive processes like reasoning and judgment. Collectively, these processes may be called biological intelligence. A component of biological intelligence is executive function. According to Denckla, 1996, executive function regulates and directs cognitive processes, decision making, problem solving, learning, reasoning and strategic thinking. Some characteristics of right hemisphere syndrome may be considered problems of the executive function. They include left side neglect where there is a lack of awareness of the left side of the body.The Parietal Lobe is immediately posterior to the central sulcus. It is anterior to the occipital lobe, from which it is not separated by any natural boundary. Its inferior boundary is the posterior portion of the lateral fissure which divides it from the temporal lobe.The parietal lobe is associated with sensation, including the sense of touch, kinesthesia, perception of warmth and cold, and of vibration. It is also involved in writing and in some aspects of reading.The postcentral gyrus which is also called the primary sensory area or the sensory strip is immediately posterior to the central sulcus. This area receives sensory feedback from joints and tendons in the body and is organized in the same manner as the motor strip.Like the motor strip, the sensory strip continues down into the longitudinal cerebral fissure and so has both a lateral and a medial aspect.The presensory, secondary sensory, or sensory association areas are located behind the postcentral gyrus. These areas are capable of more detailed discrimination and analysis than is the primary sensory area. They might, for example, be involved in sensing how hot or cold something is rather than simply identifying it as hot or cold. Information is first processed in the primary sensory area and is then sent to the secondary sensory areas.The angular gyrus lies near the superior edge of the temporal lobe, immediately posterior to the supramarginal gyrus. It is involved in the recognition of visual symbols. Geschwind described this area as "the most important cortical areas for speech and language" and the "association cortex of association...