The planum temporale: a systematic, quantitative review of its structural, functional and clinical significance

Asymmetry within and around the human planum temporale is sexually dimorphic and influenced by genes involved in steroid hormone receptor activity

“…Males have sometimes been reported to show a subtle mean increase in leftward lateralization of the PT relative to females (de Courten-Myers, 1999;Good et al, 2001;Shapleske et al, 1999). Consistent with this, foetal testosterone levels have been linked to gray matter volumes within some putatively, sexually dimorphic regions of the human brain, including the PT (Lombardo et al, 2012).…”

“…In most people the PT on the left side is larger than the right (Galaburda, 1993;Steinmetz, 1996), although varying definitions of the precise structure have resulted in different estimates of its asymmetry (Galaburda, 1993;Shapleske, Rossell, Woodruff, & David, 1999). The left PT overlaps with Wernicke's classically defined language region (Geschwind & Levitsky, 1968), which is part of the broadly left-lateralised speech and language network present in the majority of people.…”

“…The left PT overlaps with Wernicke's classically defined language region (Geschwind & Levitsky, 1968), which is part of the broadly left-lateralised speech and language network present in the majority of people. At least some of the PT is regarded as secondary auditory cortex in terms of cyto-architecture (Shapleske et al, 1999). The PT has been characterized as a computational hub for processing spectrotemporal variation in auditory perception (Griffiths & Warren, 2002), as well as having a role in mapping acoustic speech signals to frontal lobe articulatory networks (Hickok & Poeppel, 2007), and in auditory attention (Hirnstein, Westerhausen, & Hugdahl, 2013).…”

“…The PT has been characterized as a computational hub for processing spectrotemporal variation in auditory perception (Griffiths & Warren, 2002), as well as having a role in mapping acoustic speech signals to frontal lobe articulatory networks (Hickok & Poeppel, 2007), and in auditory attention (Hirnstein, Westerhausen, & Hugdahl, 2013). Given these important roles of the PT in speech and language, and its asymmetrical nature in the typically developed brain, there has been much interest in whether individual differences in PT asymmetry are associated with traits that involve changes in language cognition, including dyslexia, reduced verbal ability, and schizophrenia (Eckert et al, 2008;Frank & Pavlakis, 2001;Hasan et al, 2011;Kawasaki et al, 2008;McCarley et al, 2002;Oertel et al, 2010;Shapleske et al, 1999;Sommer, Ramsey, Kahn, Aleman, & Bouma, 2001). These studies have shown that alterations in PT asymmetry may be relevant to some etiological subtypes of these complex traits, although are not necessarily a universal feature of them (Bishop, 2013).…”

Enhancement of brain event-related potentials to speech sounds is associated with compensated reading skills in dyslexic children with familial risk for dyslexia

“…It has been stated that probably deviation in both directions from average on a symmetry-asymmetry scale can lead to deficient reading skills: small symmetrical brain structures would be associated with deficits in multiple domains of language and larger asymmetrical structures with more isolated phonological deficits that are compensated for until adulthood . Across studies, reduced or reversed asymmetry has been seen systematically in dyslexics and thought to be related to deviations in normal patterns of corticogenesis (Hynd, Semrud-Clikeman, Lorys, Novey, & Eliopulos, 1990;Shapleske, Rossell, Woodruff, & David, 1999). The brain symmetry in dyslexics suggests anatomical differences in areas relevant for speech and language Petersen, Fox, Posner, Mintun, & Raichle, 1988).…”