Describe The Location And Functionality Of The Limic System

MIDLANDS STATE UNIVERSITY
FACULTY OF SOCIAL SCENCES

Name WILFRED NYARUGWE
Reg R115625Q
Module PSYCHOBIOLOGY (PSY109)
Level 1.1
Lecturer MR MUPEDZISWA

QUESTION
1) a) With the aid of diagrams describe the location and functionality of the lobes of the brain include in your discussion the effects of damage and anatomical malfunctioning.

b) Write an account of the functionality of the limbic system.

a)
1. THE FRONTAL LOBE
Biederam, et al. (2000) defines the frontal lobe as the part of the brain that controls important cognitive skills in humans. It is located in the front of the brain deep to the frontal bone of the skull. It plays an integral role for example the following functions that is memory formation, emotions, decision making/reasoning, personality, conscious thought, behaviour, planning, organizing, problem solving. The frontal lobe is the most uniquely human of all the brain structures. It is also responsible for primary motor function, or our ability to consciously move our muscles, and the two key areas related to speech, including Broca’s area. The frontal lobe is larger and more developed in humans than in any other organism. As its name indicates, the frontal lobe is at the front of the brain. The right hemisphere of the frontal lobe controls the left part of the body, and vice versa. The frontal lobe is also the most common place for brain injury to occur. Goossens etal (2007) postulates that damage to the frontal lobe can create changes in personality, limited facial expressions, and difficulty in interpreting one’s environment, such as not being able to adequately assess risk and danger. The frontal lobe of the human brain is both relatively large in mass and less restricted in movement than the posterior portion of the brain.
Ressler & Mayberg (2007) goes on to say, following a frontal lobe injury, an individual’s abilities to make good choices and recognize consequences are often impaired. Memory impairment is another common effect associated with frontal lobe injuries, but this effect is less documented and may or may not be the result of flawed testing. Damage to the frontal lobe can cause increased irritability, which may include a change in mood and an inability to regulate behaviour. Particularly, an injury of the frontal lobe could lead to deficits in executive function, such as anticipation, goal selection, planning, initiation, sequencing, monitoring (detecting errors), and self-correction (initiating novel responses). A widely reported case of frontal lobe injury was that of Phineas Gage, a railroad worker whose left frontal lobe was destroyed by a large iron rod in 1848 (though Gage's subsequent personality changes are almost always grossly exaggerated).
2. THE PARIETAL LOBE
The Parietal Lobe of the brain is located in the middle top of the brain deep to the Parietal Bone of the skull. It plays a major role in the following functions/actions: Senses and integrates sensation(s), Spatial awareness and perception, (Proprioception - Awareness of body/ body parts in space and in relation to each other), arithmetic, spelling, and manipulation of objects.
The parietal lobe is one of the four major lobes of the cerebral cortex in the brain. The parietal lobe is positioned above the occipital lobe and behind the frontal lobe and central sulcus. The parietal lobe integrates sensory information among various modalities, including spatial sense and navigation (proprioception), the main sensory receptive area for the sense of touch (mechanoreception) in the somatosensory cortex which is just posterior to the central sulcus in the postcentral gyrus, and the dorsal stream of the visual system. The major sensory inputs from the skin (touch, temperature, and pain receptors), relay through the thalamus to the parietal lobe. Several areas of the parietal lobe are important in language processing. The somatosensory cortex can be illustrated as a distorted figure — the homunculus (Latin: "little man"), in which the body parts are rendered according to how much of the somato-sensory cortex is devoted to them. The superior parietal lobule and inferior parietal lobule are the primary areas of body or spatial awareness. A lesion commonly in the right superior or inferior parietal lobule leads to hemi-neglect. The name comes from the overlying parietal bone, which is named from the Latin paries-, "wall".
The parietal lobe is defined by three anatomical boundaries: The central sulcus separates the parietal lobe from the frontal lobe; the parieto-occipital sulcus separates the parietal and occipital lobes; the lateral sulcus (sylvian fissure) is the most lateral boundary, separating it from the temporal lobe; and the medial longitudinal fissure divides the two hemispheres. Within each hemisphere, the somatosensory cortex represents the skin area on the contra lateral surface of the body.
Immediately posterior to the central sulcus, and the most anterior part of the parietal lobe, is the postcentral gyrus (Brodmann area 3), the primary somatosensory cortical area. Dividing this and the posterior parietal cortex is the postcentral sulcus. The Cortical functions of the parietal lobe are:
Two point discrimination through touch alone without other sensory input (i.e., visual)
Graphesthesia - recognizing writing on skin by touch alone
Touch localization (bilateral simultaneous stimulation)
The parietal lobe plays important roles in integrating sensory information from various parts of the body, knowledge of numbers and their relations, and in the manipulation of objects. Its function also includes processing information relating to the sense of touch. Portions of the parietal lobe are involved with visuospatial processing. Although multisensory in nature, the posterior parietal cortex is often referred to by vision scientists as the dorsal stream of vision (as opposed to the ventral stream in the temporal lobe). This dorsal stream has been called both the "where" stream (as in spatial vision) and the "how" stream (as in vision for action). The posterior parietal cortex (PPC) receives somatosensory and/or visual input, which then, through motor signals, controls movement of the arm, hand, as well as eye movements.
More recent FMRI studies have shown that humans have similar functional regions in and around the intraparietal sulcus and parietal-occipital junction. The human "parietal eye fields" and "parietal reach region", equivalent to LIP and MIP in the monkey, also appear to be organized in gaze-centred coordinates so that their goal-related activity is "remapped" when the eyes move. Both the left and right parietal systems play a determining role in self transcendence, the personality trait measuring predisposition to spirituality.
3. THE TEMPORAL LOBES

The Temporal Lobes are located on the sides of the brain, in the temple regions deep to the Temporal Bones of the skull.
They play an integral role in the following functions: Organization/ Comprehension of language, Information Retrieval (Memory and Memory Formation), Senses of smell and sound, as well as processing of complex stimuli like faces and scenes, memory and understanding language. The primary auditory cortex is responsible for hearing and primary olfactory cortex is responsible for interpreting the sense of smell once it reaches the cortex via the olfactory bulbs. (Not visible on the superficial
cortex)
Wernicke’s Area – Language comprehension. Located on the Left Temporal Lobe.
Wernicke’s Aphasia – Language comprehension is inhibited. Words and sentences are not clearly understood, and sentence formation may be inhibited or non-sensical.

4. OCCIPITAL LOBE
The Occipital Lobe of the Brain is located in the extreme back of the brain, deep to the Occipital Bone of the Skull. Its primary function is the processing, integration, interpretation, etc. of vision and visual stimuli. Our occipital lobes are at the very back of our brain, farthest from our eyes. A significant functional aspect of the occipital lobe is that it contains the primary visual cortex. This is somewhat anti-intuitive since one of the major functions of this lobe is to interpret messages from our eyes in our visual cortex. Impulses from the retinas in our eyes are sent to the visual cortex to be interpreted. Impulses from the right half of each retina are processed in the visual cortex in the right occipital lobe. Impulses from the left part of each retina are sent to the visual cortex in our left occipital lobe. Recent studies have shown that specific neurological findings have had an impact on idiopathic occipital lobe epilepsies. Occipital lobe seizures are triggered by a flash, or a visual image that contains multiple colours. These are called flicker stimulation (usually through TV) these seizures are referred to as photo-sensitivity seizures. Patients having experienced occipital seizures described their seizures as featuring bright colours, and severely blurring their vision (vomiting was also apparent in some patients). Occipital seizures are triggered mainly during the day, through television, video games or any flicker stimulatory system. Occipital seizures originate from an epileptic focus confined within the occipital lobes. They may be spontaneous or triggered by external visual stimuli. Occipital lobe epilepsies are etiologically idiopathic, symptomatic, or cryptogenic. Symptomatic occipital seizures can start at any age, as well as any stage after or during the course of the underlying causative disorder. Idiopathic occipital epilepsy usually starts in childhood. Occipital epilepsies account for approximately 5% to 10% of all epilepsies.

b) Write an account of the functionality of the limbic system.
There is currently no consensus in the field concerning the exact definition of what neural structures constitute the limbic system (Kotter & Meyer, 1992; LeDoux, 2000).
As aptly stated by Ledoux, “after half a century of debate and discussion, there are still no agreed upon criteria that can be used to decide which areas of the brain belong to the limbic system.” (Ledoux, 2000:158). Rather than argue for or against the inclusion of a particular brain region, I will define the limbic system as a set of highly interconnected brain regions situated within the medial portion of the brain. This liberal definition encompasses all the cortical regions located along the medial fringe of the cortical mantle (Broca, 1878), as well as other adjacent cortical and subcortical structures that have been added to the limbic system over the years by several prominent investigators (Heimer & Van Hoesen, 2006; Maclean, 1952; Mesulam & Mufson, 1982; Papez, 1937; Yakovlev, 1972). The limbic system is a group of structures in the brain associated with emotions and drives. It is made up of four main structures: the amygdala, the hippocampus, regions of the limbic cortex, and the septal area. These structures form connections between the limbic system and the hypothalamus, thalamus, and cerebral cortex. The hippocampus is important in memory and learning, while the limbic system itself is central in the control of emotional
responses.
The limbic system is associated with a number of functions including the sense of smell, behavior, learning, long-term memory, emotions, and drives. The word limbic comes from the Latin word limbus, which roughly means "belt" or "border." This system is shaped somewhat like a doughnut and forms an inner border to the cortex.
The limbic system influences other systems including the autonomic nervous system and the endocrine system. It is also linked to the prefrontal cortext and the brain's pleasure center. A 1954 study by Olds and Milner inserted electrodes into areas of the limbic system of rats. These areas were stimulated whenever the rats pressed on a lever. Researchers found that the rats would actually ignore food and drink in preference of pressing the lever repeatedly, causing the animals to eventually die from exhaustion.

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