Elevated neuron number in the limbic thalamus in major depression.
OBJECTIVE
The mediodorsal and anteroventral/anteromedial nuclei of the thalamus are brain regions of interest in the study of mood disorders because they connect subcortical limbic system structures such as the amygdala with the prefrontal, cingulate, and temporal cortices. Anatomical abnormalities have been observed both in the amygdala and in the aforementioned cortical regions in affective disorder patients. Neuroanatomical studies of the thalamus have rarely been conducted in patients with mood disorders.


METHODS
Postmortem tissue from the Stanley Foundation Brain Bank was obtained from subjects diagnosed with major depressive disorder, bipolar disorder, and schizophrenia as well as a nonpsychiatric comparison group (N=10-13 per group). The optical disector stereological procedure was used to count neurons in the mediodorsal and anteroventral/anteromedial nuclei of the thalamus in each brain.


RESULTS
There were significantly more neurons in the mediodorsal (37%) and anteroventral/anteromedial (26%) nuclei in subjects with major depressive disorder relative to the nonpsychiatric comparison subjects. Neuron numbers and volumes in these limbic thalamic nuclei were normal in the schizophrenia and bipolar subjects.


CONCLUSIONS
The data indicate that there is an elevation in total neuron number in the limbic thalamus that is specific for major depressive disorder. This represents the first report of a neuropsychiatric disorder being associated with an increase in total regional neuron number. The present findings, along with recent data, indicate that significant anatomical and functional abnormalities are present in limbic circuits in major depressive disorder.
Young
Keith A
KA
Neuropsychiatry Research Program (151N), Central Texas Veterans Health Care System, 1901 S. First Street, Temple, TX 76504, USA. kayoung@medicine.tamu.edu
Holcomb
Leigh A
LA
Yazdani
Umar
U
Hicks
Paul B
PB
German
Dwight C
DC
D000328:Adult; D001714:Bipolar Disorder / Q000175:diagnosis; D002452:Cell Count; D003866:Depressive Disorder / Q000175:diagnosis*; D005260:Female; D006801:Humans; D008032:Limbic System / Q000166:cytology*; D008297:Male; D020645:Mediodorsal Thalamic Nucleus / Q000166:cytology; D008875:Middle Aged; D009434:Neural Pathways / Q000166:cytology; D009474:Neurons / Q000166:cytology*; D012559:Schizophrenia / Q000175:diagnosis; D013787:Thalamic Nuclei / Q000166:cytology*; D014015:Tissue Banks; D020651:Ventral Thalamic Nuclei / Q000166:cytology