It is

It is a type of negative memory that causes the neuronal circuit to lose its response to repeated events that are insignificant. Conversely, if a noxious stimulus excites the facilitator terminal at the same time that the sensory terminal is stimulated, then instead of the transmitted signal into the postsynaptic neuron becoming progressively weaker, the ease of transmission becomes stronger and stronger; and it will remain strong for minutes, hours, days, or, with more intense training, up to about weeks even without further stimulation of the facilitator terminal. Thus, the noxious stimulus causes the memory pathway through the sensory terminal to become facilitated for days or weeks thereafter. It is especially interesting that even after habituation has occurred, this pathway can be converted back to a facilitated pathway with only a few noxious stimuli. Molecular Mechanism of Intermediate Memory Mechanism for Habituation. At the molecular level, the habituation effect in the sensory terminal results from progressive closure of calcium channels through the terminal membrane, though the cause of this calcium channel closure is not fully known. Nevertheless, much smaller than normal amounts of calcium ions can diffuse into the habituated terminal, and much less sensory terminal transmitter is therefore released because calcium entry is the principal stimulus for transmitter release as was discussed in Chapter Chapter Cerebral Cortex, Intellectual Functions of the Brain, Learning and Memory Mechanism for Facilitation.

These functions

These functions of the nervous system are performed mainly by the basal regions of the brain, which together are loosely called the limbic system, meaning the border system. ActivatingDriving Systems of the Brain Without continuous transmission of nerve signals from the lower brain into the cerebrum, the cerebrum becomes useless. In fact, severe compression of the brain stem at the juncture between the mesencephalon and cerebrum, as sometimes results from a pineal tumor, often causes the person to go into unremitting coma lasting for the remainder of his or her life. Nerve signals in the brain stem activate the cerebral part of the brain in two ways: by directly stimulating a background level of neuronal activity in wide areas of the brain and by activating neurohormonal systems that release specific facilitory or inhibitory hormonelike neurotransmitter substances into selected areas of the brain. Control of Cerebral Activity by Continuous Excitatory Signals from the Brain Stem Reticular Excitatory Area of the Brain Stem Figure shows a general system for controlling the level of activity of the brain. The central driving component of this system is an excitatory area located in the reticular substance of the pons and mesencephalon. This area is also known by the name bulboreticular facilitory area. We also discuss this area in Chapter because it is the same brain stem reticular area that transmits facilitory signals downward to the spinal cord to maintain tone in the antigravity muscles and to control levels of activity of the spinal cord reflexes.

It is

It is here that plans and motor patterns for expressing individual words or even short phrases are initiated and executed. This area also works in close association with Wernickes language comprehension center in the temporal association cortex, as we discuss more fully later in the chapter. An especially interesting discovery is the following: When a person has already learned one language and then learns a new language, the area in the brain where the new language is stored is slightly removed from the storage area for the first language. If both languages are learned simultaneously, they are stored together in the same area of the brain. Limbic Association Area. Figures and show still another association area called the limbic association area. This area is found in the anterior pole of the temporal lobe, in the ventral portion of the frontal lobe, and in the cingulate gyrus lying deep in the longitudinal fissure on the midsurface of each cerebral hemisphere. It is concerned primarily with behavior, emotions, and motivation. We will learn in Chapter that the limbic cortex is part of a much more extensive system, the limbic system, that includes a complex set of neuronal structures in the midbasal regions of the brain. This limbic system provides most of the emotional drives for activating other areas of the brain and even provides motivational drive for the process of learning itself. Area for Recognition of Faces An interesting type of brain abnormality called prosophenosia is inability to recognize faces.

For instance,

For instance, the role of the hypothalamus to help regulate arterial pressure is discussed in Chapter , thirst and water conservation in Chapter , temperature regulation in Chapter , and endocrine control in Chapter To illustrate the organization of the hypothalamus as a functional unit, let us summarize the more important of its vegetative and endocrine functions here as well. Figures and show enlarged sagittal and coronal views of the hypothalamus, which represents only a small area in Figure Take a few minutes to study these diagrams, especially to see in Figure the multiple activities that are excited or inhibited when respective hypothalamic nuclei are stimulated. In addition to the centers shown in Figure , a large lateral hypothalamic area shown in Figure is present on each side of the hypothalamus. The lateral areas are especially important in controlling thirst, hunger, and many of the emotional drives. A word of caution must be issued for studying these diagrams because the areas that cause specific activities are not nearly as accurately localized as suggested in the figures. Also, it is not known whether the effects noted in the figures result from stimulation of specific control nuclei or whether they result merely from Thalamus Figure Coronal view of the hypothalamus, showing the mediolateral positions of the respective hypothalamic nuclei. activation of fiber tracts leading from or to control nuclei located elsewhere.With this caution in mind, we can give the following general description of the vegetative and control functions of the hypothalamus.