Handbook of Forensic Neuropsychology
Conversely, the posterior hypothalamus regulates sympathetic activity, or stress response, often referred to as fight or flight.
Located in the center of the brain, just superior to the hypothalamus, the thalamus is an ovoid structure of gray matter found deep in the white matter of cerebrum. The thalamus is made up of two large, symmetrical nuclei, with one nucleous situated on each side of the midline of the brain. The nuclei are situated around the third ventricle, and help to form its lateral walls. The thalamus contains a number of nerve endings and, like the hypothalamus, the nuclei of the thalamus are highly interconnected with most of the other parts of the central nervous system.
Most information that reaches the cortex is processed at some point in the thalamus.
THE HANDBOOK OF FORENSIC NEUROPSYCHOLOGY
Many pathways carrying information from the brain stem to the cortex relay their information through the thalamic nuclei. In addition, the thalamus is important as the pathway for primary sensory and motor impulses to and from the cerebral hemisphere. With the exception of the olfactory sense, axons from all other sensory systems use the thalamus as the last relay site before the information reaches the cerebral cortex. As with the hypothalamus, damage to the thalamus can have various functional consequences. Common symptoms associated with brain injuries involving the thalamus include problems with short-term memory, attention, and concentration.
Lesions to the thalamus also have been associated with areas that would be implicated in the interruption of the relay of essential information between the cerebral cortex and other areas of the brain, including marked deficits in gross areas of sensory or motor function, depressed scores on cognitive verbal tests, and problems associated with spatial ability, facial recognition, and perception of music. As the processing center of the cerebral cortex, the thalamus coordinates and regulates all functional activity of the cortex via the integration of the afferent input to the cortex except olfaction.
Its contribution to effectual expression is clear, as is its ability to alter levels of consciousness. Damage to this area may affect the above, as well as cause the loss of perception and a relatively rare disorder known as thalamic syndrome, which is seen as an acute pain on the opposite side of the body.
Handbook of Forensic Psychology
Telencephalon The telencephalon is the most anterior portion of the forebrain. It consists of the cerebral hemispheres, the limbic system, and the basal ganglia. The telencephalon the cerebral hemispheres is the largest of the divisions of the human brain, and it is what subserves languageat least those aspects of language that are of interest to linguistics. In fact, the same can be said of just the cerebral cortex, which is only one of the four parts of the telencephalon according to the traditional divisions given previously.
Of the subcortical and interior portions of the telencephalon, the basal ganglia, which partially surround the diencephalon, participate in motor functions, including articulation of speech, whereas the hippocampus and the amygdaloid nucleus, which lie deep within the lower part of the cortex, are very important in emotional expression. Present analyses of the telencephalon using a multiple approach have demonstrated, among other features, the presence of a ventral pallidal region, a striatopallidal subdivision in the basal ganglia, and three main components of the amygdaloid complex.
Therefore, in spite of its apparently simple organization, within the telencephalon of urodeles it is possible to identify most of the features observed in amniotes and anurans that are only revealed with the use of combined modern techniques in neuroanatomy. The hippocampus is actually a paleocortical structure thus part of the cortex deeply embedded within the lower temporal lobe of either hemisphere.
It is important for remembering events of ones personal history and other kinds of what are known as declarative memory, and so it looms large in linguistic activity, as the linguistic system clearly has access to this kind of information. More than that, it appears that the hippocampus, since it plays an important role in declarative memory along with higher cortical levels , is of great importance in language learning of the kind commonly done in high schools and colleges, which is quite different from that done by children, who automatically use lower levels of their cerebral cortices, acquiring their native language skills as procedural knowledge rather than declarative knowledge.
That difference is directly correlated with the great skill and fluency of people using their native languages as opposed to the clumsiness with which they attempt to navigate their way in a foreign country with the aid of a school-taught second language. With recent research showing hitherto unthought-of subcortical features in cognitive functioning, this area of the brain has become of special interest. The Limbic System The structures most often associated with the limbic system include the fornix, the mammillary bodies of the hypothalamus, the cingulate cortex, the amygdala, the hippocampus, and the septum.
As with the structures of the diencephalon, the complex associations of the limbic system with various areas of the nervous system comprise a maze of interconnectivity that makes a one-to-one, structurefunction relationship difficult to outline. A good deal of data suggests that the.
Also, due to its placement, the limbic system plays a role in the integration of recent memory and control of biological rhythms. Hippocampus One of the most studied components of the limbic system is the hippocampus. In humans there are two hippocampal structures, one in each hemisphere of the brain. The hippocampal formation has been associated with memory acquisition and spatial navigation.
Bilateral injury of the hippocampus often involves an inability to learn new, declarative memories. In contrast, memories for skills, such as riding a bicycle, or memories for procedures are often unaffected by hippocampal damage. Recent evidence implicates the hippocampus in the processing and storage of spatial information Ekstrom et al. Damage to the hippocampus may lead to an inability to remember where one is or how to get to a destination.
Losing ones way is a common symptom in amnesia, and may be related to hippocampal damage. In addition, the hippocampal function seems to be lateralized.
While damage to the left hippocampal gyrus tends to cause problems with long-term verbal memory, right hippocampal damage tends to result in greater impairment of long-term spatial memory. Other disorders are secondary with hormonal imbalances, such as malignant hypothermia and inability to control core temperature. Results also have resulted in agitation disorders, and loss of control of emotion and elements of recent memory. Patients report a loss of the sense of smell. Amygdala Another noteworthy element of the limbic system is the amygdala.
The amygdalae are a pair of small, almond-shaped collections of nuclei located deep in the brain, adjacent to the hippocampus and medial to the hypothalamus. The amygdalae have both ascending and descending connections with the cerebral cortex, the thalamus, the hippocampus, and the spinal cord. At present, the amygdalae are believed to play an important role in the strength of stored memory, especially for episodic memories in which emotions play a role Phelps, In addition, the amygdalae have been implicated as the center for the mediation of the autonomic fear response, a fundamental self-preservation mechanism that triggers the fight or flight response in circumstances of danger.
Damage to the amygdala and its interconnections has been shown to have implications in severe emotional disturbances, including episodes of extreme violence and aggression. Humans with marked lesions in the amygdala lose the affective meaning of the perception of information, they are able to name a person, but unable to recall emotional features. In general, this limbic formation is responsible in part for emotions, sex, rage, and fear, as well as the integration of recent memory and biological rhythms.
Basal Ganglia The basal ganglia, also termed the basal nuclei, are a collection of symmetric nuclei found deep in the telencephalon, and are enclosed by the cerebral cortex and white matter.
These gray matter structures partially surround the thalamus. The current understanding of the structure of the basal ganglia indicates three major, interconnected structures: the caudate nucleus, the putamen, and the globus pallidus. These structures are primarily connected to the cerebral cortex through the thalamus, the reticular formation, and the midbrain.
Researchers currently believe that the primary function of the basal ganglia is voluntary motor control, specifically related to the planning and initiating of motor behavior, maintaining muscular readiness to respond, and establishing posture. Together with the cerebral cortex in the midbrain and the cerebellum, the basal ganglia have been proposed as the area responsible for stereotyped postural and reflexive motor behavior extrapyramidal motor system.
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Damage to the basal ganglia, as in disorders such as Huntington disease or Wilson disease, often results in involuntary, jerking movements of the arm or leg and spasmodic movement of facial muscles. Patients with lesions in the basal ganglia may have difficulty initiating, sustaining, or ceasing motor movement, agitation, or loss of control of emotion and recent memory.
Tremors, slowing of movement, facial and motor tics, difficulty walking, rigidity, and motor-related speech problems may all occur subsequent to head trauma affecting the basal ganglia. Comprising subcortical gray matter nuclei, the basal ganglia provide a processing link between thalamus and motor cortex and are responsible for the initiation and direction of voluntary movement, as well as balance inhibitory movement and postural reflexes that are part of the extrapyramidal system of regulation of automatic movement.
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Disorders of movement such as Parkinsons, chorea, tremors at rest and with initiation of movement, abnormal increases in muscle tone, and difficulty initiating movement reside in this area. Cerebral Cortex The cerebral cortex is the largest, most evolutionarily advanced part of the brain. This structure consists of two large cerebral hemispheres, separated by a deep longitudinal fissure. The two hemispheres are structurally and functionally coupled by a number of interconnections, most notably by the prominent bundle of intercerebral axons called the corpus callosum.
The corpus callosum makes direct communication between the two hemispheres possible. The surface of the cerebrum, which is covered in gray matter consisting of neuronal cell bodies, dendrites, and interconnecting axons of neurons, is convoluted by both deep and shallow grooves sulci and fissures, respectively and ridges gyri.
Just underneath the cortex is white matter, millions of axonal pathways that link the neurons of the cortex with those found within the rest of the brain and central nervous system. Three areas of the cerebral cortex receive information from sensory organs. Visual information is analyzed and processed in the primary visual cortex, an area located on the upper and lower banks of the calcarine fissure situated on the inner surfaces of the cerebral hemispheres.
The primary auditory cortex is located on the lower surface of the lateral fissure, a deep groove that runs along the side of the brain. The primary somatosensory cortex, a vertical strip of cortex just caudal to the central sulcus, receives information from the body senses. Different regions of the primary somatosensory cortex receive information from different regions of the body.
The base of the somatosensory cortex and a portion. The primary motor cortex, located just in front of the primary somatosensory cortex, is directly involved in the control of movement and directs the output through motor processing. Neurons in the primary motor cortex are connected to muscles in different parts of the body. Other areas of the cerebral cortex are responsible for those elements of organization of higher cognitive functions, perceiving, learning, remembering, planning, and acting.
These processes take place in the associated areas of the cerebral cortex.