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It is strange that the lateral nucleus should be included among the reward areasindeed, it is one of the most potent of allbecause even stronger stimuli in this area can cause rage. But this is true in many areas, with weaker stimuli giving a sense of reward and stronger ones a sense of punishment. Less potent reward centers, which are perhaps secondary to the major ones in the hypothalamus, are found in the septum, the amygdala, certain areas of the thalamus and basal ganglia, and extending downward into the basal tegmentum of the mesencephalon. Punishment Centers The apparatus shown in Figure can also be connected so that the stimulus to the brain continues all the time except when the lever is pressed. In this case, the animal will not press the lever to turn the stimulus off when the electrode is in one of the reward areas; but when it is in certain other areas, the animal immediately learns to turn it off. Stimulation in these areas causes the animal to show all the signs of displeasure, fear, terror, pain, punishment, and even sickness. By means of this technique, the most potent areas for punishment and escape tendencies have been found in the central gray area surrounding the aqueduct of Sylvius in the mesencephalon and extending upward into the periventricular zones of the hypothalamus and thalamus. Less potent punishment areas are found in some locations in the amygdala and hippocampus. It is particularly interesting that stimulation in the punishment centers can frequently inhibit the reward and pleasure centers completely, demonstrating that punishment and fear can take precedence over pleasure and reward.

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This helps to maintain the level of excitation of the cerebral cortex or even to enhance it. This is a general mechanism of positive feedback that allows any beginning activity in the cerebral cortex to support still more activity, thus leading to an awake mind. Thalamus Is a Distribution Center That Controls Activity in Specific Regions of the Cortex. As pointed out in Chapter and shown in Figure , almost every area of the cerebral cortex connects with its own highly specific area in the thalamus. Therefore, electrical stimulation of a specific point in the thalamus generally activates its own specific small region of the cortex. Furthermore, signals regularly reverberate back and forth between the thalamus and the cerebral cortex, the thalamus exciting the cortex and the cortex then reexciting the thalamus by way of return fibers. It has been suggested that the thinking process establishes longterm memories by activating such backandforth reverberation of signals. Can the thalamus also function to call forth specific memories from the cortex or to activate specific thought processes? Proof of this is still lacking, but the thalamus does have appropriate neuronal circuitry for these purposes. A Reticular Inhibitory Area Located in the Lower Brain Stem Figure shows still another area that is important in controlling brain activity. This is the reticular inhibitory area, located medially and ventrally in the medulla. In Chapter , we learned that this area can inhibit the reticular facilitory area of the upper brain stem and thereby decrease activity in the superior portions of the brain as well.

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Yet even the association areas have their specializations. The most important association areas are the parietooccipitotemporal association area, the prefrontal association area, and the limbic association area. Following are explanations of the functions of these areas. Parietooccipitotemporal Association Area. This association area lies in the large parietal and occipital cortical space bounded by the somatosensory cortex anteriorly, the visual cortex posteriorly, and the auditory cortex laterally. As would be expected, it provides a high level of interpretative meaning for signals from all the surrounding sensory areas. However, even the parietooccipitotemporal association area has its own functional subareas, which are shown in Figure Analysis of the Spatial Coordinates of the Body. An area beginning in the posterior parietal cortex and extending into the superior occipital cortex provides continuous analysis of the spatial coordinates of all parts of the body as well as of the surroundings of the body. This area receives visual sensory information from the posterior occipital cortex and simultaneous somatosensory information from the anterior parietal cortex. From all this information, it computes the coordinates of the visual, auditory, and body surroundings. Area for Language Comprehension. The major area for language comprehension, called Wernickes area, lies behind the primary auditory cortex in the posterior part of the superior gyrus of the temporal lobe.

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For this reason, it is believed that activation of Wernickes area can call forth complicated memory patterns that involve more than one sensory modality even though most of the individual memories may be stored elsewhere. This belief is in accord with the importance of Wernickes area in interpreting the complicated meanings of different patterns of sensory experiences. Angular GyrusInterpretation of Visual Information. The angular gyrus is the most inferior portion of the posterior parietal lobe, lying immediately behind Wernickes area and fusing posteriorly into the visual areas of the occipital lobe as well. If this region is destroyed while Wernickes area in the temporal lobe is still intact, the person can still interpret auditory experiences as usual, but the stream of visual experiences passing into Wernickes area from the visual cortex is mainly blocked. Therefore , the person may be able to see words and even know that they are words but not be able to interpret their meanings. This is the condition called dyslexia, or word blindness. Let us again emphasize the global importance of Wernickes area for processing most intellectual functions of the brain. Loss of this area in an adult usually leads thereafter to a lifetime of almost demented existence. Chapter Cerebral Cortex, Intellectual Functions of the Brain, Learning and Memory Concept of the Dominant Hemisphere The general interpretative functions of Wernickes area and the angular gyrus, as well as the functions of the speech and motor control areas, are usually much more highly developed in one cerebral hemisphere than in the other.