Elliott M. Marcus

Higher Cortical Functions

What is a higher cortical function? As one examines the abilities of a human, one is struck by our ability to use tools and create wonderful buildings or works of art. But our ability to communicate by speaking and writing and reading we believe is the best example of a higher cortical function. These centers that are responsible for language are primarily in the dominant hemisphere. The motor type of aphasia (Broca’s area) originates from the inferior frontal gyrus, while the sensory type of aphasia originates in the superior temporal gyrus (Wernicke’s area).

Meninges, Ventricular System and Vascular System

The brain is enclosed by three membranes: the dura mater, arachnoid, and pia mater. These protective fluid-filled membranes are formed by connective tissue with embedded nerves, especially in the dura. The dura mater is the most external membrane, followed by the arachnoid and finally the pia mater, which adheres to the central nervous system (CNS).

Diencephalon with Atlas of the Thalamus

This chapter will concentrate on the dorsal thalamus or simply the thalamus. As can be seen from the terminology associated with the diencephalon, all structures are described by their spatial relationship to the thalamus, being above, below, or behind them. Glutamate is the principal transmitter in the thalamus.

Movies on the Brain

This chapter reviews movies from Hollywood that illustrate the effects of many diseases on the brain. These movies cover developmental disorders, disease in the spinal cord, brain stem, and cerebrum. The causes of these disparate injuries include congenital malformations, genetic abnormalities, trauma to the brain, vascular insufficiencies, tumors and infections. All of these selected movies are very entertaining and informative.

General Case Histories from the CNS-Problem Solving

This 53-year-old, right-handed, white housewife (Mrs. S.P.) had the onset of weakness in the lower extremities approximately 10 months prior to admission. At the same time, the patient noted twitching of the muscles of the legs, i.e., fasciculations. The weakness progressed so that the patient had difficulty in walking. Approximately 8 months prior to admission, the patient noted the onset of weakness and fasciculations in the upper extremities. This was noted most particularly with regard to the hands. The patient had had a progression of symptoms in the intervening months; approximately a 30 lb weight loss was experienced. Although the patient complained of fatigue and some lethargy, she had noted no definite change in mental status. She had not experienced any headaches or pains in the neck. She had had no diplopia or visual disturbances. No sensory symptoms were noted; no urinary or bowel symptoms were noted. Past history and family history were not remarkable.

The Cranial Nerves

There are 12 pairs of cranial nerves, and they originate from the brain and upper spinal cord and innervate the special sense organs in the head (eye, ear, nose, and taste buds), the skin over the face and neck, and muscles that permit us to speak, eat, turn our head, and produce facial expressions. These cranial nerves also provide parasympathetic innervation to the eye (III) and glands in the head and neck (VII, IX and X) and the X cranial nerve, the vagus innervates the skeletal muscles in the larynx that produce speech, and also innervate the organs of the cardiovascular system, pulmonary system, GI system, and urogenital systems.

Spinal Cord with Atlas of Spinal Cord

The spinal cord is tubular is shape, has 32 segments with the gray matter in the center and white matter on the outside. Each segment has nerve rootlets on the dorsal and ventral surface with ganglia attached to the dorsal nerve rootlets. These dorsal root ganglia contain the primary cell bodies of the general sensory systems-pain, temperature touch, and pressure.

Somatosensory Functions and the Parietal Lobe

The parietal lobe is the middle lobe of the cerebrum, is found on the lateral surface of the hemisphere, and consists of postcentral gyrusa and superior and inferior parietal lobules. In this region of the cerebrum, one finds major functional differences between the left hemisphere which is dominant for language and the right hemisphere that is important for body imagery. The pain pathway has been discussed in Chap. 3, spinal cord; Chap. 4, brain stem; and Chap. 6, diencephalon. In this chapter, we will cover the pathways subserving tactile information for (1) the extremities, the thorax and abdomen, and the posterior columns and (2) the trigeminal systems subserving tactile information from the head. The importance of these pathways is apparent when one walks in the dark, drinks, or eats.

Limbic System and the Temporal Lobe

The neurologist Paul Broca in the later half of the nineteenth century initially designated all of the structures on the medial surface of the cerebral hemisphere the “great limbic lobe.” This region, due to its strong olfactory input, was also designated the rhinencephalon. The olfactory portion of the brain (rhinencephalon, or archipallium) comprises much of the telencephalon in fish, amphibians, and most mammals. In mammals the presence of a large olfactory lobe adjacent to the hippocampus was once considered to be evidence of the important olfactory functions of these regions. However, when a comparative neuroanatomist examined the brains of sea mammals that had rudimentary olfactory apparatus, e.g., dolphins and whales, the presence of a large hippocampus suggested other than olfactory functions for this region.

Motor System II: Basal Ganglia

The caudate and putamen have the same structure (Table 12.1) and are continuous anteriorly. The globus pallidus has two sectors: a medial or inner and a lateral or outer. The substantia nigra has two components: a ventral pars reticularis which is identical in structure and function to the medial sector of the globus pallidus and a dorsal darkly staining component the pars compacta which contains large dopamine and melanin containing neurons. The nuclei of the basal ganglia may be categorized as (1) input nuclei (caudate, putamen, and accumbens), (2) intrinsic nuclei (lateral segment of the globus pallidus, subthalamic nucleus, pars compacta of the substantia nigra, and the ventral tegmental area) and (3) output nuclei (medial segment of the globus pallidus, pars reticularis of the substantia nigra, and the ventral pallium). The consideration of the chemical and pharmacological anatomy of transmitters and circuits within the system will provide an understanding of function and dysfunction within this system.