Morphology, morphometry and probability mapping of the pars opercularis of the inferior frontal gyrus: an in vivo MRI analysis

Abstract

The pars opercularis occupies the posterior part of the inferior frontal gyrus. Electrical stimulation or damage of this region interferes with language production. The present study investigated the morphology and morphometry of the pars opercularis in 108 normal adult human cerebral hemispheres by means of magnetic resonance imaging. The brain images were transformed into a standardized proportional steoreotaxic space (i.e. that of Talairach and Tournoux) in order to minimize interindividual brain size variability. There was considerable variability in the shape and location of the pars opercularis across brains and between cerebral hemispheres. There was no significant difference or correlation between left and right hemisphere grey matter volumes. There was also no significant difference between sex and side of asymmetry of the pars opercularis. A probability map of the pars opercularis was constructed by averaging its location and extent in each individual normalized brain into Talairach space to aid in localization of activity changes in functional neuroimaging studies.

Functional specificity for high-level linguistic processing in the human brain

“…Nonlinguistic tasks. In experiment 1 (math), participants (n = 11) saw a number (11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22)(23)(24)(25)(26)(27)(28)(29)(30) and added three addends to it (of sizes two to four or six to eight in the easy and hard conditions, respectively). † After each trial, participants had to choose the correct sum in a two-choice forced choice question (the incorrect sum deviated by one to two).…”

“…Such findings do not suffice to demonstrate common brain regions for linguistic and nonlinguistic functions in the brain. Even when two tasks are compared in the same group of subjects, standard functional MRI group analysis methods can be deceptive: two different mental functions that activate neighboring but nonoverlapping cortical regions in every subject individually can produce overlapping activations in a group analysis, because the precise locations of these regions vary across subjects (24)(25)(26), smearing the group activations. Definitively addressing the question of neural overlap between linguistic and nonlinguistic functions requires examining overlap within individual subjects (27,28), a data analysis strategy that has almost never been applied in neuroimaging investigations of high-level linguistic processing.…”

An attempt to replicate a dissociation between syntax and semantics during sentence comprehension reported by Dapretto & Bookheimer (1999,Neuron)

“…http://dx.doi.org/10.1101/110791 doi: bioRxiv preprint first posted online Feb. 22, 2017; individual anatomical and functional variability that is rampant in the left frontal lobe (e.g., Amunts et al, 1999;Tomaiuolo et al, 1999;Juch et al, 2005;Fedorenko et al, 2012b), we were able to detect reliably greater responses to the Semantic than Syntactic condition within the orbital and triangular portions of the LIFG. However, nowhere within the LIFG were there regions that responded reliably more strongly during the processing of the Syntactic condition compared to the Semantic condition.…”

“…We then extracted the responses to the Semantic and Syntactic conditions (including effects specific to each type of construction) from the other half of the data. This analysis can help circumvent the high inter-individual variability that characterizes the mapping of function onto anatomy in human frontal lobes (e.g., Amunts et al, 1999;Tomaiuolo et al, 1999;Juch et al, 2005;Fedorenko et al, 2012b). Thus, even if the individual activation peaks for the Semantic>Syntactic and Syntactic>Semantic contrast are spatially variable enough so that group-level analyses (both whole-brain random-effects analysis and ROI-based analysis) fail to detect them, this analysis would recover these effects if they hold across participants anywhere within the LIFG.…”

An MRI study of spatial probability brain map differences between first-episode schizophrenia and normal controls

“…Accordingly, many groups have noted the importance of probabilistic atlases and have made probability maps using different modalities and different methodologies. Probability maps for subregions of normal brains have been reported (Amunts et al, 1999(Amunts et al, , 2000Kennedy et al, 1998;Leonard et al, 1998;Loftus et al, 1995;Paus et al, 1996;Penhune et al, 1996;Rademacher et al, 2001aRademacher et al, ,b, 2002Thompson et al, 1996a;Tomaiuolo et al, 1999;Varnavas and Grand, 1999;Westbury et al, 1999;White et al, 1997).…”