A QUALITATIVE AND QUANTITATIVE-ANALYSIS OF THE ENTORHINAL CORTEX IN SCHIZOPHRENIA

The entorhinal cortex (ERC) has been implicated in schizophrenia by a number of studies. There is anatomical observation of neuronal heterot opias in the rostral ERC, which is consistent with a hypothesis of neu rodevelopmental abnormalities in this disease. In view of the signific ant cytoarchitectonic variation of the ERC throughout its rostro-cauda l extent, we performed a detailed subareal analysis of the rostral two -thirds of the entorhinal cortex (ERCr) in 14 postmortem schizophrenic brains and 14 matched controls (mean ages of 48 and 47 respectively). This systematic evaluation included both a qualitative microscopic an alysis of morphogenetic anomalies that would be consistent with neurod evelopmental pathology and quantitative measurements of total neuronal number, average neuronal density, laminar volume and laminar depth fr om the cortical surface in cytoarchitectonically matched subareas of s chizophrenic and control brains. Parcellation of the entire ERC on the basis of cytoarchitectonic criteria identified five distinct regions, similar to those described in the macaque, except that in the human b rain three of the regions were further divisible into two or three sub areas, yielding nine distinct cellular compartments. Five rostral area s, prorhinal (Pr), lateral (28L), intermediate rostral and caudal (28I r and 28Ic), and sulcal (28S), comprise the ERCr. Gross and microscopi c examination of these subdivisions throughout the ERCr failed to reve al laminar disorganization in any of the schizophrenic brains. The bra ins also did not differ significantly with respect to total neuronal n umber, total volume and neuronal density per laminar and subareal subd ivision, or laminar thickness per entorhinal subarea. However, neurona l number and density were reduced by 12-18% in Pr and 28L, suggesting that mild quantitative abnormalities may exist in the ERCr and might p ossibly be revealed in a larger sample of schizophrenic brains. We hav e failed to confirm previous reports of laminar disorganization in the ERCr in brains of patients with schizophrenia; to the extent that thi s region is implicated in schizophrenia, the structural changes are li kely to consist of more subtle cellular disturbances.