Hippocampal abnormalities in depression

A quantitative magnetic resonance imaging study of regional brain TI spin-lattice relaxation times in 29 normal volunteers and in 20 patients with major depression revealed significantly shortened Ti relaxation times for the hip pocam pus in depressed patients. These differences were particularly prominent in elderly depressed patients. Ti relaxation times are reflective of the content and macromolecular environment of tissue water protons; shorter hip pocam pal Ti values may reflect differences in the content or organizational pro perties of hippocampal water protons. These findings are consistent with several lines of evidence that have implicated a role for the hip pocam pus in the regulation of mood and in the pathophysiology of the stress response, and they suggest that major depression may be associated with biophysical tissue changes in the aging hippocam pus. (The Journal of Neuropsychiatry and Clinical Neurosciences 1991; 3:387-391) T he hippocampus, along with structures located in the medial aspect of the temporal lobe (such as the amygdaloid complex and parahippocampal gyms) and in the basal forebrain (septal nucleus, substantia innominata, and nucleus accumbens), represent an anatomical and functional circuit widely believed to play an important role in the behavioral expression of emotion.’ In addition, the hippocampus has been reported to play an important role in the mediation of the neuroendocrine alterations observed after stress in aging.2 These two factors led us to investigate the possible role of hippocampal dysfunction in patients with major depression. The development of magnetic resonance imaging (MIil) has permitted multiplanar visualization of the hippocampus with high resolution and has allowed for the in vivo detection of hippocampal atrophy in patients with amnesia5 and schizophrenia.6 MRI also can reveal biophysical water proton tissue changes in histologically discrete areas of the brain (such as cerebral gray and white matter). In addition, spin-lattice relaxation time (Ti) as measured by MRT has been shown to be sensitive to the content and macromolecular organizational environment of tissue water.79 Changes in water composition can lead to demonstrable changes in TI relaxation times,