Middle and Inferior Temporal Gyrus Gray Matter

Objective—Magnetic resonance imaging (MRI) studies of schizophrenia reveal temporal lobe structural brain abnormalities in the superior temporal gyrus and the amygdala-hippocampal complex. However, the middle and inferior temporal gyri have received little investigation, especially in first-episode schizophrenia. Method—High-spatial-resolution MRI was used to measure gray matter volume in the inferior, middle, and superior temporal gyri in 20 patients with first-episode schizophrenia, 20 patients with first-episode affective psychosis, and 23 healthy comparison subjects. Results—Gray matter volume in the middle temporal gyrus was smaller bilaterally in patients with first-episode schizophrenia than in comparison subjects and in patients with first-episode affective psychosis. Posterior gray matter volume in the inferior temporal gyrus was smaller bilaterally in both patient groups than in comparison subjects. Among the superior, middle, and inferior temporal gyri, the left posterior superior temporal gyrus gray matter in the schizophrenia group had the smallest volume, the greatest percentage difference, and the largest effect size in comparisons with healthy comparison subjects and with affective psychosis patients. Conclusions—Smaller gray matter volumes in the left and right middle temporal gyri and left posterior superior temporal gyrus were present in schizophrenia but not in affective psychosis at first hospitalization. In contrast, smaller bilateral posterior inferior temporal gyrus gray matter volume is present in both schizophrenia and affective psychosis at first hospitalization. These findings suggest that smaller gray matter volumes in the dorsal temporal lobe (superior and middle temporal gyri) may be specific to schizophrenia, whereas smaller posterior inferior temporal gyrus gray matter volumes may be related to pathology common to both schizophrenia and affective psychosis. Abnormalities of the temporal lobe figure prominently in our understanding of the pathology of schizophrenia, especially in the superior temporal gyrus and the amygdala-hippocampal complex (1). The middle and inferior temporal gyri, by contrast, have received far less attention. These gyri, located on the lateral surface of the temporal neocortex, are involved in cognitive Address correspondence and reprint requests to Dr. McCarley, Department of Psychiatry (116A), Boston VA Healthcare System, Brockton Division, Harvard Medical School, 940 Belmont St., Brockton, MA 02301; robert_mccarley@hms.harvard.edu. All authors report no competing interests. NIH Public Access Author Manuscript Am J Psychiatry. Author manuscript; available in PMC 2009 October 26. Published in final edited form as: Am J Psychiatry. 2006 December ; 163(12): 2103–2110. doi:10.1176/appi.ajp.163.12.2103. N IH PA Athor M anscript N IH PA Athor M anscript N IH PA Athor M anscript functions such as language, visual perception, and memory (2–4). Given this functional role, examining these gyri might contribute importantly to our understanding of the pathophysiology of schizophrenia. The superior part of the superior temporal gyrus includes both the primary and secondary auditory sensory cortex (the Heschl gyrus and planum temporale). Recent functional magnetic resonance imaging studies have shown that the superior temporal gyrus is involved in early auditory processing common to speech and nonspeech stimuli (5). The gray matter in the middle temporal gyrus and around the superior temporal sulcus (which separates the superior temporal gyrus from the middle temporal gyrus) is involved in processing the human voice (6) or audiovisual speech (7), which are complex, socially relevant stimuli. The left posterior inferior temporal gyrus is probably involved in the visual word grapheme system and in semantic processing (2,5). The middle and inferior temporal gyri are known to be importantly involved in both dorsal and ventral visual pathways (8) as well as in multimodal and higher sensory processing. Since functional deficits in language, memory (9), and visual spatial perception (10) have all been reported in schizophrenia, gray matter abnormalities in the middle and inferior temporal gyri may be an important anatomical substrate. In a postmortem study (11), smaller bilateral inferior temporal gyrus gray matter volumes were noted in schizophrenia patients compared with control subjects, although the results fell short of statistical significance. Only a small number of in vivo morphometry studies of the middle and inferior temporal gyri in schizophrenia have been conducted, perhaps because these large regions have more complicated boundaries than other temporal lobe structures. Our laboratory has reported (12) significantly smaller volumes in the left middle temporal gyrus (13%) and bilaterally in the inferior temporal gyri (10%) in male chronic schizophrenia patients compared with healthy control subjects. In contrast, Goldstein et al. (13), using an anatomic landmarkbased semiautomated program, found no significant differences in middle or inferior temporal gyrus gray matter volume in chronic schizophrenia patients compared with control subjects. In studies using voxel-based morphometry methods, findings of reduced volumes in the middle and inferior temporal gyri in schizophrenia have been inconsistent. One study reported reduced gray matter volume in the right middle temporal gyrus in schizophrenia patients compared with healthy control subjects (14), but another reported reduced gray matter volume in the left middle temporal gyrus (15). Most voxel-based morphometry studies, however, have reported no differences in the middle temporal gyrus between schizophrenia patients and healthy control subjects, and none have reported differences in the inferior temporal gyrus. There are also many potential artifacts in MR images of the inferior temporal gyrus relative to other regions, including the susceptibility effect of air in the ear and the potential segmentation confound of the nearby tentorium cerebelli. Thus it may be more difficult to detect differences between groups in the inferior temporal gyrus when using automated methods, which may be more susceptible to artifacts than are manual measures. The roles of the middle and inferior temporal gyri in the psychopathology and pathophysiology of schizophrenia are incompletely understood. It is not known to what extent abnormalities in these gyri are present at the beginning of the illness, nor whether such abnormalities are specific to schizophrenia. In this study, we sought to clarify these questions by analyzing temporal gyrus gray matter volumes in patients with first-episode psychosis; to determine the specificity of altered gray matter to schizophrenia, we included patients with both affective and schizophrenic psychoses. We analyzed high-resolution MR images with a manual segmentation method based on three-dimensional information to provide reliable segmentation. In an earlier study (16), we reported that gray matter volume in the left posterior superior temporal gyrus was smaller in first-episode schizophrenia patients than in patients Kuroki et al. Page 2 Am J Psychiatry. Author manuscript; available in PMC 2009 October 26. N IH PA Athor M anscript N IH PA Athor M anscript N IH PA Athor M anscript with affective psychosis and healthy comparison subjects. To determine whether the magnitude of the volume difference in the superior temporal gyrus gray matter differed from that of the middle or inferior temporal gyri, we compared the middle and inferior temporal gyri with the superior temporal gyrus. This study included 46 subjects from our previous study examining the superior temporal gyrus (16) and 17 new subjects—five patients with schizophrenia, four patients with affective psychosis, and eight healthy comparison subjects. Middle and inferior temporal gyrus volumes have not been reported previously for any subject in this study.