Parahippocampal region

A Short-term group B Long-term group 

The dramatic difference between the density of BrdU+ cells in postischemic PHR and the density in neighboring regions such as CA1 or IT was evident when low-magnification micrographs were evaluated in control and postischemic monkeys. A dense band of positive cells in postischemic CA1 contrasted the dispersed single 

Investigating the phenotype of BrdU+ in PHR we did not observe differences between control and postischemic brains. A proportion of BrdU+ cells (up to 15%) expressed the phenotype of either microglia or astroglia (Fig. 30A), and some vascular cells incorporated BrdU as well. BrdU+ oligodendrocytes or cells with a neuronal phenotype were not observed (Fig. 30B). Thus, over 75% of the BrdU+ cells in the PHR were of an unknown phenotype. 

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Functional neuroimaging studies suggest that frontal and occipital brain areas are integral to the anxiety response. Patients with panic disorder may have abnormal activation of the parahippocampal region and prefrontal cortex at rest. Panic anxiety is associated with activation of brain stem and basal ganglia regions. GAD patients have an abnormal increase in cortical... 

Lawrence et al, (2002) 15 14 4.5 4.7 RVIP In smokers, nicotine improved task performance and increased neural activity in the parietal and occipital cortices, the thalamus and caudate, and decreased activity in left frontal, anterior and posterior cingulate, insula, and left parahippocampal regions. 

Lawrence and colleagues (2002) explored the neural substrates of nicotine effects on sustained attention using the rapid visual information processing (RVIP) task. Smokers (n = 15) received either placebo or 21-mg transdermal nicotine patch prior to testing. Matched nonsmokers (n = 14) were tested under similar conditions, but did not receive a nicotine patch. Relative to the placebo condition, the smokers in the nicotine condition demonstrated improved task performance and increased neural activity in the parietal and occipital cortices, the thalamus and caudate, and decreased activity in left frontal, anterior and posterior cingulate, insula, and left parahippocampal regions (see Fig. 3). As noted by the authors, previous studies... 

The medial and caudal portions of the midbody of the CC contain interhemispheric projections from the auditory cortices, posterior cingulate, retrosplenial cortex, and insula, and somatosensory and visual cortices to a lesser extent. It also includes connections from the inferior parietal lobe to the contralateral superior temporal sulcus, cingulate, and parahippocampal gyrus (Pandya and Seltzer, 1986). Several of the regions with interhemispheric projections through the medial and caudal portions of the midbody of the CC are involved in the processing of emotional stimuli and various memory functions—core disturbances frequently observed in children with a history of early trauma. 

We do not yet know if the left-right differences in cortical activation (measured in the waking EEG by Davidson) will persist, or be nullified, or even reversed in REM sleep, but we do know that compared to waking, the amygdala and its directly adjacent cortical areas, the parahippocampal and anterior cingulate regions, are selectively activated in REM sleep and, as discussed in the previous section, that this preferential limbic activation is reciprocal to deactivation of both dorsolateral prefrontal cortices. 

Finally, the hippocampus is not the only brain region that is smaller in schizophrenia (Honea et al., 2005 Steen et al., 2006 Velakoulis et al., 2006 Vita et al., 2006). Especially those brain regions that are closely connected with the hippocampus (i.e., amygdala, ERC, perirhinal cortex (PRC), and parahippocampal cortex (PHC)) appear to be affected similarly in schizophrenia (Wright et al., 2000 Sim et al., 2006) ( Figure 3.1-1). 

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