The arcuate fasciculus is the neural pathway

Neural pathway

A neural pathway, neural tract, or neural face, connects one part of the nervous system with another and usually consists of bundles of elongated, myelin-insulated neurons, known collectively as white matter...

 connecting the posterior part of the temporoparietal junction

Temporoparietal junction

The temporoparietal junction is an area of the brain where the temporal and parietal lobes meet, at the posterior end of the Sylvian fissure...

 with the frontal cortex in the brain

Brain

The brain is the center of the nervous system in all vertebrate and most invertebrate animals—only a few primitive invertebrates such as sponges, jellyfish, sea squirts and starfishes do not have one. It is located in the head, usually close to primary sensory apparatus such as vision, hearing,...

 and is now considered as part of the superior longitudinal fasciculus

Superior longitudinal fasciculus

The superior longitudinal fasciculus is a pair of long bi-directional bundles of neurons connecting the front and the back of the cerebrum. Each association fiber bundle is lateral to the centrum ovale of a cerebral hemisphere and connects the frontal, occipital, parietal, and temporal lobes...

..

Neuroanatomy

While previously thought to connect Wernicke's area

Wernicke's area

Wernicke's area is one of the two parts of the cerebral cortex linked since the late nineteenth century to speech . It is involved in the understanding of written and spoken language...

 and Broca's area

Broca's area

Broca's area is a region of the hominid brain with functions linked to speech production.The production of language has been linked to the Broca’s area since Pierre Paul Broca reported impairments in two patients. They had lost the ability to speak after injury to the posterior inferior frontal...

, new research demonstrates that the arcuate fasciculus instead connects posterior receptive areas with premotor/motor areas, and not to Broca's area.

Although the regions the arcuate fasciculus connects to is still in debate, the "connectivity" of the arcuate has been shown to correspond to various functional areas within the temporal, parietal, and frontal lobes As fractional anisotropy of the acruate increases, cortical thickness increases in corresponding areas. These findings thus suggest that particular components of white matter microstructure and regional increases in cortical thickness benefit aspects of language processing. Furthermore, the topographical relationships between independent measures of white matter and gray matter integrity suggest that rich developmental or environmental interactions influence brain structure and function where the presence and strength of such associations may elucidate pathophysiological processes influencing language systems.

The function of the arcuate fasciculus in the nondominant hemisphere is not well studied.

Pathology

Damage to this pathway can cause a form of aphasia

Aphasia

Aphasia is an impairment of language ability. This class of language disorder ranges from having difficulty remembering words to being completely unable to speak, read, or write....

 known as conduction aphasia

Conduction aphasia

Conduction aphasia, also called associative aphasia, is a relatively rare form of aphasia. An acquired language disorder, it is characterized by intact auditory comprehension, fluent speech production, but poor speech repetition. Patients will display frequent errors during spontaneous speech,...

, where auditory comprehension and speech articulation are preserved, but people find it difficult to repeat heard speech.

In nine of ten tone deafness

Tone deafness

Tone deafness is the lack of relative pitch, or the inability to distinguish between musical notes that is not due to the lack of musical training or education...

 people, the superior arcuate fasciculus

Arcuate fasciculus

The arcuate fasciculus is the neural pathway connecting the posterior part of the temporoparietal junction with the frontal cortex in the brain and is now considered as part of the superior longitudinal fasciculus..-Neuroanatomy:...

in the right hemisphere could not be detected, suggesting a disconnection between the posterior superior temporal gyrus and the posterior inferior frontal gyrus. Researchers suggested the posterior superior temporal gyrus was the origin of the disorder.

External links

• http://www.lib.mcg.edu/edu/eshuphysio/program/section8/8ch15/s8c15_14.htm
• http://thebrain.mcgill.ca/flash/d/d_10/d_10_cr/d_10_cr_lan/d_10_cr_lan.html
• http://brain.oxfordjournals.org/cgi/reprint/awh622v1.pdf