The transverse temporal gyri, also called Heschl's gyri () or Heschl's convolutions, are
gyri
In neuroanatomy, a gyrus (pl. gyri) is a ridge on the cerebral cortex. It is generally surrounded by one or more sulci (depressions or furrows; sg. ''sulcus''). Gyri and sulci create the folded appearance of the brain in humans and other ma ...
found in the area of
primary auditory cortex
The auditory cortex is the part of the temporal lobe that processes auditory information in humans and many other vertebrates. It is a part of the auditory system, performing basic and higher functions in hearing, such as possible relations to ...
buried within the
lateral sulcus
In neuroanatomy, the lateral sulcus (also called Sylvian fissure, after Franciscus Sylvius, or lateral fissure) is one of the most prominent features of the human brain. The lateral sulcus is a deep fissure in each hemisphere that separates the ...
of the
human brain
The human brain is the central organ of the human nervous system, and with the spinal cord makes up the central nervous system. The brain consists of the cerebrum, the brainstem and the cerebellum. It controls most of the activities of the ...
, occupying
Brodmann areas 41 and 42
Brodmann areas 41 and 42 are parts of the primary auditory cortex.
Brodmann area 41 is also known as the anterior transverse temporal area 41 (H). It is a cytoarchitectonic division of the cerebral cortex occupying the anterior transverse tem ...
. Transverse temporal gyri are superior to and separated from the
planum temporale
The planum temporale is the cortical area just posterior to the auditory cortex (Heschl's gyrus) within the Sylvian fissure. It is a triangular region which forms the heart of Wernicke's area, one of the most important functional areas for languag ...
(cortex involved in language production) by Heschl's sulcus. Transverse temporal gyri are found in varying numbers in both the right and left hemispheres of the brain and one study found that this number is not related to the hemisphere or dominance of hemisphere studied in subjects. Transverse temporal gyri can be viewed in the sagittal plane as either an omega shape (if one gyrus is present) or a heart shape (if two gyri and a sulcus are present).
Transverse temporal gyri are the first cortical structures to process incoming auditory information. Anatomically, the transverse temporal gyri are distinct in that they run mediolaterally (toward the center of the brain), rather than front to back as all other
temporal lobe
The temporal lobe is one of the four Lobes of the brain, major lobes of the cerebral cortex in the brain of mammals. The temporal lobe is located beneath the lateral fissure on both cerebral hemispheres of the mammalian brain.
The temporal lobe ...
gyri run.
The ''Heschl's gyri'' are named after
Richard L. Heschl
Richard Ladislaus Heschl (; July 5, 1824, in WelsdorfNona.net Welsdorf (Steiermark, Austria) bei .
Processing tone
The transverse temporal gyri are active during auditory processing under
fMRI
Functional magnetic resonance imaging or functional MRI (fMRI) measures brain activity by detecting changes associated with blood flow. This technique relies on the fact that cerebral blood flow and neuronal activation are coupled. When an area o ...
for tone and semantic tasks. Transverse temporal gyri were found in one study to have significantly faster processing rates (33 Hz) in the left hemisphere compared to those in the right hemisphere (3 Hz). Additionally this difference in processing rate was found to be related to the volume of rate-related cortex in the gyri; right transverse temporal gyri were found to be more active during temporal processing, and these gyri were found to have more “rate-related cortex”. White and grey matter volumes of transverse temporal gyri were not found to relate to this processing speed, although larger white matter volumes in subjects are associated with increased sensitivity to “rapid auditory input”.
The role of transverse temporal gyri in auditory processing of tone is demonstrated by a study by Wong, Warrier et al. (2008). This study revealed the following: subjects who could successfully form an association between Mandarin Chinese “pitch patterns” and word meaning were found to have transverse temporal gyri with larger volume than subjects who had “difficulty learning these associations.” Successful completion of the previous task also was found to be associated with a “greater concentration of white matter” in the left transverse temporal gyri of the subject. In general, larger transverse temporal gyri “could be associated with more efficient processing of speech-related cues which could facilitate learning and perceiving new speech sounds.”
Inner voice
Research on the inner voice perceived by humans led to the identification of these gyri as the area of the brain activated during such dialogue with oneself. Specifically, Heschl's gyrus responded to spontaneous inner speech, while it was hypoactive during task-elicited inner speech (repeating words prompted by an experimenter).
Mismatch negativity
One of the famous
event-related potential
An event-related potential (ERP) is the measured brain response that is the direct result of a specific sense, sensory, cognition, cognitive, or motor system, motor event. More formally, it is any stereotyped electrophysiology, electrophysiologi ...
(ERP) components is mismatch negativity. This component is considered to represent a prediction error process in the brain. This ERP has probably two generators, one in the right prefrontal lobe, and the other in the primary auditory regions - the transverse temporal gyrus and the superior temporal gyrus.
Additional images
File:Transverse temporal gyrus.gif, 3D view of the transverse temporal gyrus in an average human brain
File:Transverse temporal gyrus coronal sections.gif, Transverse temporal gyrus highlighted in green on coronal T1 MRI images
File:Transverse temporal gyrus sagittal sections.gif, Transverse temporal gyrus highlighted in green on sagittal T1 MRI images
File:Transverse temporal gyrus transversal sections.gif, Transverse temporal gyrus highlighted in green on transversal T1 MRI images