Brain temporal lobe

Complex partial seizures manifest themselves as bizarre behaviours which are also known as psychomotor or temporal lobe epilepsy, since a lesion (focus) is often found in that brain area. Repetitive and apparently purposeful movements vary from simple hand clenching or rubbing to more bizarre hand movements and walking. These can last a few minutes, often disrupt other ongoing activity or speech and the patient has no subsequent memory of them. Complex seizures may develop from simple ones. 

There have been a number of observations which show increased excitation and/or reduced inhibition in slices prepared from human epileptic brain tissue. Thus burst discharges can be evoked with stimuli that would not do so in normal animal tissue and these can be blocked by NMD A receptor antagonists. The inhibitory postsynaptic currents (IPSCs) in hippocampal dentate granule cells in slices prepared from temporal lobe epileptic tissue are in fact reduced by stimulation that activates NMDA currents (Isokawa 1996), which are more prolonged than usual and show changes in slope conductance. 

Compared to the Category Test, SSP and SRT results show a relatively mixed performance profile. This profile is indicative of temporal lobe impairment and may explain the idiosyncratic character of PCP-induced brain dysfunction. Other HRB subtest data suggest that parietal lobe-mediated functions are less influenced by PCP abuse, since approximately 30 percent of this sample had error-free performances on a test sensitive to finger agnosia. 

Mesial temporal lobe epilepsy (MTLE) A type of epilepsy that consists of partial seizures arising from the mesial temporal lobe of the brain. Often this type of epilepsy is associated with an anatomic change described as hippocampal sclerosis. Patients with this type of epilepsy often have excellent outcomes with surgery for epilepsy. 

Named for the bones of the cranium under which they lie, the lobes are conspicuously defined by prominent sulci of the cortex, which have a relatively constant position in human brains. Each lobe is specialized for different activities (see Figure 6.3). Located in the anterior portions of the hemispheres, the frontal lobes are responsible for voluntary motor activity, speaking ability, and higher intellectual activities. The parietal lobes, which are posterior to the frontal lobes, process and integrate sensory information. The occipital lobes, located in the posterior-most aspects of the cerebrum, process visual information, and the temporal lobes, located laterally, process auditory information. 

H. M. was the first human case in which specific amnesia could be linked to selective regions of the brain. Since then, many patients have been identified as having selective lesions to the temporal lobe system, especially within the hippocampus. They have exhibited amnesias similar to H. M. s. For example, amnesic patient, R. B, who had a specific lesion in the CA1 region of hippocampus, showed profound loss of ability to form new memories of people, places, and events [5]. R. B. also lost memories regarding public and personal events that he had experienced two... 

FIGURE 53-1 Illustrative drawing of the temporal lobe system in the human brain. (A) Anatomical sites, marked by black dots, within the temporal lobe where electrical stimulation evoked experiential responses in Penfield s patients. (B) The location of the hippocampus and amygdala inside the temporal lobe. 

Although magnetic resonance imaging is very useful (especially imaging of the temporal lobes), computed tomography typically is not helpful except in the initial evaluation for a brain tumor or cerebral bleeding. 

CNS disorders (brain tumor, strokes, head injuries, subdural hematoma, multiple sclerosis, systemic lupus erythematosus, temporal lobe seizures, Huntington s disease)... 

Rieder CR, Parsons RB, Fitch NJ, Williams AC, Ramsden DB. 2000. Human brain cytochrome P450 IBl immunohisto-chemical localization in human temporal lobe and induction by dimethylbenz(a)anthracene in astrocytoma cell line (MOG-G-CCM). Neurosci Lett 278 177-180. 

Dementias due to trauma usually do not progress in this manner. The injury damages the brain and causes dementia, but further deterioration does not occur. In contrast, a few dementias can be rapidly progressive. This includes most dementias due to infection (although syphilis and AlDS-related dementias are usually slowly progressive) as well as Pick s disease, a dementia associated with a relatively early age of onset, characterized by massive degeneration of frontal and temporal lobe tissue. 

Brain imaging (preferably MRI) to look for evidence of structural damage is essential after TBI. MRI, while more expensive and time-consuming, can sometimes detect small brain lesions that are missed by CT, especially in the frontal and temporal lobes that are common sources of psychiatric complications after TBI. In addition, an electroencephalogram (EEG) can detect seizure activity or other signs of abnormal brain function. Although they are not yet part of the routine post-TBI evaluation, the so-called functional brain imaging techniques such as positron emis-... 

Temporal lobe brain structures, in particular the hippocampal formation, appear to play a pivotal yet transient role in the formation of new explicit memories. This chapter focuses on possible neurochemical mechanisms underlying the encoding of new information in the hippocampus and the modulation of memory function by different neurotransmitter systems in the brain. 

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