The lingual gyrus, also known as the ''medial'' occipitotemporal gyrus, is a brain structure that is linked to processing vision, especially related to letters. It is thought to also play a role in analysis of logical conditions (i.e., logical order of events) and encoding visual memories. It is named after its shape, which is somewhat similar to a tongue. Contrary to the name, the region has little to do with speech. It is believed that a hypermetabolism of the lingual gyrus is associated with

visual snow Visual snow syndrome (VSS) is an uncommon neurological condition in which the primary symptom is that affected individuals see persistent flickering white, black, transparent, or coloured dots across the whole visual field. Other common symptom ...

Location

The lingual gyrus of the

occipital lobe The occipital lobe is one of the four major lobes of the cerebral cortex in the brain of mammals. The name derives from its position at the back of the head, from the Latin ''ob'', "behind", and ''caput'', "head". The occipital lobe is the vi ...

lies between the

calcarine sulcus The calcarine sulcus (or calcarine fissure) is an anatomical landmark located at the caudal end of the medial surface of the brain of humans and other primates. Its name comes from the Latin "calcar" meaning "spur". It is very deep, and known ...

and the posterior part of the

collateral sulcus The collateral fissure (or sulcus) is on the tentorial surface of the hemisphere and extends from near the occipital pole to within a short distance of the temporal pole. Behind, it lies below and lateral to the calcarine fissure, from which it ...

; behind, it reaches the occipital pole; in front, it is continued on to the tentorial surface of the

temporal lobe The temporal lobe is one of the four 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 is involved in pro ...

, and joins the parahippocampal gyrus.

Function

Role in vision

This region is believed to play an important role in vision and dreaming. Visual memory dysfunction and visuo-

limbic The limbic system, also known as the paleomammalian cortex, is a set of brain structures located on both sides of the thalamus, immediately beneath the medial temporal lobe of the cerebrum primarily in the forebrain.Schacter, Daniel L. 2012. ''Ps ...

disconnection have been shown in cases where the lingual gyrus has been damaged (due to stroke or other traumatic brain injuries). Further, impaired visual memory is related to either damage to the region or disconnections between the gyrus and other brain structures. Hypermetabolism in the lingual gyrus has been associated with

syndrome. Lingual gyrus activation has been linked to encoding of complex images. Subjects were scanned using fMRI while looking at pictures. The images were emotionally neutral, with no people in close-up. Subjects were tasked with memorizing the images for recognition at a later date. Data from the fMRI showed activation in several structures, notably the lingual gyrus. Similar activation was recorded during the recollection several weeks later. It has also been shown that activation of the ventral occipitotemporal cortex, including the lingual gyrus, is related to the processing of visual information about parts of human faces. Furthermore, the left lingual gyrus activates during memorizing and maintaining images of human faces in working memory. Activation of the lingual gyrus has been shown in selective visual attention studies. Subjects were tasked with memorizing symbols in certain visual fields while ignoring those in others. In some subjects, the lingual gyrus was activated. The hemispheric activation of the structure was dependent on which visual field the subject was focused on. Hemispheric-dependent gyrus activation has also been shown by isolating visual fields rather than by diverting focus.

Role in word processing

The lingual gyrus is a structure in the

visual cortex The visual cortex of the brain is the area of the cerebral cortex that processes visual information. It is located in the occipital lobe. Sensory input originating from the eyes travels through the lateral geniculate nucleus in the thalamus and ...

that plays an important role in the identification and recognition of words.Mechelli. A.. Humphreys. G. W.. Mayall. K.. Olson. A.. 8. Price. C. J. (2000). Differential effects of word length and visual contrast in the fusiform and lingual gyri during reading. Proc Biol Sci. 267(1455). 1909-1913. Studies have implicated the lingual gyrus as being involved in modulating visual stimuli (especially letters) but not whether or not the stimulus was a word. Further, the gyrus is related to the naming of stimuli. Furthermore, the gyrus has shown significant activation when moving from high to low contrast words as well as a correlation between word length and regional activation. In addition to recognition of letters, the region has been linked to semantic processing. Subjects with

aphasia Aphasia is an inability to comprehend or formulate language because of damage to specific brain regions. The major causes are stroke and head trauma; prevalence is hard to determine but aphasia due to stroke is estimated to be 0.1–0.4% in t ...

were tested with a variety of aphasia tests while undergoing fMRI to determine which areas were affected. Repetition of stimuli led to modulation in the lingual gyrus in subjects not afflicted, while those with aphasia showed significantly less modulation. Similarly, the region is activated by non-verbal, logic-based conditions. Subjects tasked with attributing intentions to characters in comic strips showed activation in the gyrus when comparing physical logic with and without characters. For example: if a subject was intended to determine what a character will do, the region will activate. Conversely, if the comic depicted a physical event without characters, the region was relatively dormant. Additional studies have shown a relationship between memorization and activation in the gyrus. When subjects were tasked with pairing abstract nouns with either visual imagery or sentence generation, many areas in the occipital lobe – namely the lingual gyrus – showed task-selective memory effects. This effect was primarily linked to visual imagery, as there were no significant effects associated with sentence generation. This link between memory and the gyrus extends to retrieval fluency in children, as well. Studies have shown elevated signals in the lingual gyrus when subjects were tasked with retrieval of facts while problem solving. Control samples show the activation is not linked to the problem solving itself, rather the recollection. This suggests a potential link between the lingual gyrus and

hippocampal The hippocampus (via Latin from Greek , 'seahorse') is a major component of the brain of humans and other vertebrates. Humans and other mammals have two hippocampi, one in each side of the brain. The hippocampus is part of the limbic system, an ...

regions in the brain. Furthermore, the gyrus is potentially linked to the

amygdala The amygdala (; plural: amygdalae or amygdalas; also '; Latin from Greek, , ', 'almond', 'tonsil') is one of two almond-shaped clusters of nuclei located deep and medially within the temporal lobes of the brain's cerebrum in complex verte ...

. Gyrus activation was observed when subjects were tasked with verbalizing high-emotion words in contrast to neutral-emotion words. A second study linked the regions with high-emotion images. When subjects were shown emotional images, the amygdala and lingual gyrus both activated significantly more when compared to neutral-emotion images.Kehoe, E. G., Toomey, J. M., Balsters, J. H., & Bokde, A. L. (2012). Healthy aging is associated with increased neural processing of positive valence but attenuated processing of emotional arousal: an fMRI study. Neurobiol Aging. doi: 10.1016/j.neurobiolaging.2012.07.006

Additional images

File:Lingual gyrus animation small.gif, Position of lingual gyrus (shown in red). File:OccCaptsMedial.png, Gyri and sulci of occipital and temporal lobe. File:Slide3ZEN.JPG, Medial surface of cerebral hemisphere. Medial view. Deep dissection. File:Inner Lingual - DK ATLAS.png, Inner lingual gyrus, shown in the right cerebral hemisphere. File:Lingual gyrus sagittal sections.gif, Lingual gyrus highlighted in green on sagittal T1 MRI images File:Lingual gyrus coronal sections.gif, Lingual gyrus highlighted in green on coronal T1 MRI images File:Lingual gyrus transversal sections.gif, Lingual gyrus highlighted in green on transversal T1 MRI images

References