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The occipital lobe is the center for visual processing in the human brain. It is the smallest of the four lobes in the cerebral cortex and is located in the posterior region of the cerebral cortex. The occipital lobe is responsible for visuospatial processing and interpreting conscious visual percepts (Canevin et al). The purpose of this paper is to investigate any pathological diseases or damage that may affect the brain area, along with identifying the major neurotransmitters, and the different connections the occipital lobe has with other brain regions. Additionally, this paper will discuss the functional aspects of the occipital lobe.
The occipital lobe is not particularly vulnerable to injury due to its location at the back of the brain. Although, when damage does occur it presents a variety of symptoms ranging from hallucinations, illusions, the loss of vision, and the inability to recognize faces and objects.
Visual illusions often take the form of objects appearing larger or smaller than they really are. This is usually the first sign that there is an abnormality in the occipital region. Often patients experience more severe symptoms such as, visual hallucinations. Complex visual hallucinations are associated with right occipital injuries, tumors, seizures, and other abnormalities ( Benizky, 2001). Visual hallucinations may accompany many neurological and psychiatric disorders. Determining whether hallucinations are the result of damage to the occipital lobe or due to a psychiatric disorder requires an extensive assessment of the individuals past history. Further investigation provides insight into the subjective nature of visual hallucinations, and provides new theories of perception and recall.
Patients who have suffered damage to their occipital lobe due to a stroke may not experience any problems other than difficulties with their vision. Some of the symptoms include problems recognizing objects, loss of hand eye coordination, and visual reduction. Some patients
may recognize the sound of something but not the sight. For instances, a patient can recognize a bell ringing by hearing it only, and not by visually seeing it.
To function properly the occipital lobe utilizes various neurotransmitters from a variety of brain regions. Many neurotransmitters are needed to accurately identify a potential threat and execute a reaction. The main neurotransmitter involved in the occipital lobe is serotonin. The functions of serotonin are numerous and appear to involve the control of appetite, sleep, memory, and learning. (Canevin et al). Numerous brain regions become activated when the occipital lobe sends visual information. Most important is the activation of the frontal lobe, which allows an individual to logically process the information. The neurotransmitter most associated with the frontal lobe is dopamine. Dopamine is responsible for motivation, cognition, punishment and reward. It is easy to see the relationship dopamine has on visual input (Anderson and Rizzo, 1994).The neurotransmitter dopamine plays a crucial role in positive reinforcement. Organisms are rewarded for behaviors and visual stimuli they perceive as positive. Positive reinforcement is the basis for all learning.
Because the occipital lobe is the visual processing center of the brain, it provides mental representations of reality, which is then processed and sent to other brain regions. For example, when a person sees a train coming at them, the occipital lobe interprets this information and sends it to the frontal lobe. The frontal lobe processes the information and motivates the person to react. Once this is accomplished, the information is sent to the cerebellum which produces the reaction to get out of the way.
The functions of the occipital lobe are numerous and extensive. First and foremost, the occipital lobe is the visual processing center of the brain, It creates a mental representation of visual stimuli. In addition, it regulates our sleep and synchronizes all the cerebral lobes. The occipital lobe produces delta brain waves and the neurotransmitter serotonin. Moreover, the occipital lobe is involved with the brain's ability to recognize objects. The occipital lobe is not only responsible for visual recognition of objects but it also helps us differentiate between shapes. Identifying and interpreting different shapes such would be much harder if the occipital lobe did not function as it does.
Furthermore, the occipital lobe contains the primary visual cortex which is highly specialized in processing visouspatial information. The occipital lobe is divided into four extrastriate visual cortical areas which are identified as V1, V2, V3, and V4. Neurons in this area respond very well to visual stimuli within their field. Studies have shown that this area is responsible for conscious perception (Canevin et al). Each visual cortical area transmits information in two ways; the dorsal route and the ventral route. The dorsal pathway is associated with motion and object location. The ventral route is most associated with the storage of long term memory.
In conclusion, the occipital lobe is one of the most important structures of the cerebral cortex. It is highly specialized in recognizing shapes, faces, objects, and colors. The extremely complex interaction between the occipital lobe and other brain regions emphasizes the elaborate relationship that is required for visual processing. Without such a system it would be impossible to perceive reality in any meaningful way.
- Anderson SW, Rizzo M (1994). Hallucinations following occipital lobe damage. The pathological activation of visual representations. J Clin Exp Nueropsychology ,16, 651-653.
- Caveni, MP., Saeti, Sw (2001) Visuoperceptive Impairment in Adults with Occipital Lobe Epilepsy. Epilepsy and Behavior, 205-206.
- Benzky, S., Ker, S.(2002) Complex Hallucination Following Occipital Lobe Damage. European journal of nuerology, 9, 175-176