![]() (Animal studies later elucidated the critical anatomical components of this memory system. The severity of memory impairment is exacerbated by additional damage to medial temporal lobe structures outside of the hippocampus. In humans, damage limited to the hippocampus (a structure within the medial temporal lobe) is sufficient to cause moderately severe amnesia. Well-studied cases of human amnesia and animal models of amnesia provide information about the neural connections and structures that are damaged. Specifically, left-sided damage especially affects memory for verbal material, while right-sided damage especially affects memory for nonverbal material (e.g., memory for faces and spatial layouts). Bilateral damage results in amnesia for all types of material, and unilateral damage results in material-specific amnesia. In all of these conditions, the common factor is the disruption of normal function in one of two areas of the brain - the medial aspects of the temporal lobe, and the diencephalic midline. Neurological amnesia results from a number of conditions including Alzheimer’s disease or other dementing illnesses, temporal lobe surgery, chronic alcohol abuse, encephalitis, head injury, anoxia, ischemia, infarction, and the rupture and repair of an anterior communicating artery aneurism. Functional amnesia is a psychiatric disorder, and there is no particular brain structure or region whose damage is known to underlie this condition. Functional amnesia is characterized by a profound retrograde amnesia with little or no anterograde amnesia. ![]() It presents as a different pattern of anterograde and retrograde memory impairment than neurological amnesia. Patients with neurological amnesia also typically have some difficulty remembering facts and events that were acquired before the onset of amnesia (retrograde amnesia).įunctional amnesia is rarer than neurological amnesia and can occur as the result of an emotional trauma. Neurological amnesia causes severe difficulty in learning new facts and events (anterograde amnesia). Neurological amnesia occurs following brain injury or disease that damages the medial temporal lobe or medial diencephalon. The terms explicit and implicit memory are sometimes used and have approximately the same meanings as declarative and nondeclarative, respectively. ![]() In contrast, nondeclarative memory, which refers to a collection of non-conscious knowledge systems, is largely thought to remain intact. ![]() Declarative memory refers to conscious knowledge of facts and events. Neurological amnesia is characterized by a loss of declarative memory. Squire, University of California, San Diego, CAĪmnesia (neurological amnesia and functional amnesia) refers to difficulty in learning new information or in remembering the past. Yael Shrager, Howard Hughes Medical Institute, MGH, and Harvard University, Cambridge, MA, USAĭr. ![]()
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