Inferior frontal gyrus of the brain: its characteristics and functions.

A summary of the characteristics and functions of the inferior frontal gyrus, a fold of the brain.

The brain contains numerous folds and convolutions that make up different anatomical structures, among which is the inferior frontal gyrus, which we will discuss in this article. the inferior frontal gyrus, which we will discuss in this article..

This brain region is part of the prefrontal cortex, and houses such important areas as Broca's, essential in the production of language.

Below we explain what the inferior frontal gyrus is and where it is located, what functions it performs and what are the main disorders associated with lesions in this area of the brain.

Inferior frontal gyrus: definition, structure and anatomical location.

The inferior frontal gyrus is one of the many convolutions contained in the human brain.The gyrus of the cerebral cortex, the folds that form the characteristic relief of this organ and give it the wrinkled appearance of its outer surface, the cerebral cortex.

This gyrus is located below the inferior frontal sulcus, and extends forward from the inferior part of the precentral sulcus. It is bounded anteriorly by the lateral or Sylvian fissure. Up to three distinct parts can be identified in the inferior frontal gyrus: the pars opercularis, behind the anterior ascending branch; the pars triangularis, between the ascending and horizontal branches; and the pars orbitalis, below the anterior horizontal branch of the cisura.

The caudal limit of the pars opercularis is the inferior precentral sulcus and its rostral limit is the anterior ascending branch of the lateral cisura.. Occasionally, an additional sulcus is often identified: the diagonal sulcus, within the pars opercularis. When present, it may remain separate or may be mixed with the ascending sulcus.

On the other hand, there are authors who have divided the inferior frontal gyrus into a posterior and an anterior part. While it may be said that this sulcus may continue, ventrally, almost to the lateral margin of the orbital frontal region, this may result in a false impression as a result of the fusion of the anterior part of the inferior frontal sulcus with a different sulcus that often forms the anterior end of the triangular pair: the pretriangular sulcus.

Functions

The inferior frontal gyrus is one of the component parts of the prefrontal cortex of the brain, whose main functions have to do with executive control and planning of complex behaviors, decision making or management and matching behavior to social norms..

In recent years, research has focused on the role of the inferior frontal gyrus in a specific aspect of executive control: behavioral inhibition or response inhibition.. This can be broadly defined as the ability to control and withhold responses to routine or predominant internal or external stimuli that arise during task performance.

Tasks that examine response inhibition typically involve the development of a routine response, followed by the cancellation of the response when an infrequent para signal is detected. For example, with the Go/No go task, in which there are two starting conditions, and on some trials one must respond to the stimuli (Go trial) and on others one must not respond (No go), so that the examiner can then measure the individual's ability to inhibit his or her responses.

Another function in which the inferior frontal gyrus is involved is attentional control. In order to measure the attentional capacity of a subject, "Stop signal" tasks are usually used, an experimental test that serves to measure the inhibitory processes and the automaticity of the subjects' responses, and which also uses Go/No Go tasks.

The latest findings based on functional MRI studies confirm that the inferior frontal gyrus also plays a general role in the control of inhibitory processes and the automaticity of subjects' responses. also plays a general role in attentional control as a necessary structure for the person to as a structure necessary for the person to adapt and respond to relevant stimuli and to be inhibited by non-relevant or distracting stimuli.

The role of the inferior frontal gyrus in language processing should also be noted, since Broca's area is part of this gyrus. This brain region, located in the left hemisphere, is essential in the expression of language and speech production, as it is responsible for planning the sequence of movements necessary for us to articulate the words we pronounce.

Mirror neurons

Mirror neurons are a special class of neurons that are activated both by observing the behavior of others and by performing it ourselves. They are called mirror neurons because they allow us to deduce what others think and feel, and are closely related to aspects such as empathy, imitation or social behavior.

There is evidence that mirror neurons exist in several brain regions, among them: the pars opercularis of the inferior frontal gyrus and the inferior parietal lobe, although it is also suggested that there could be nuclei of these neurons in other areas such as the insula, the anterior cingulate and the superior temporal gyrus.

Studies conducted with people with autism spectrum disorder (ASD) show the existence of alterations in the activity of their mirror neurons, specifically in the inferior frontal gyrus, the insula and the cingulate cortex. These alterations would explain the inability of these people to grasp the intentions of others and to experience empathy, as people do.as people without ASD do.

Related disorders

Research on patients with prefrontal lobe lesions involving the inferior frontal gyrus has revealed that they tend to show a deficit in response inhibition. It has been suggested that there is a centrally located inhibitory mechanism that suppresses irrelevant responses, and that this inhibition is mainly located in the right inferior frontal gyrus.

On the other hand, the same mechanism of inhibitory control seems to be altered in patients with obsessive-compulsive disorder (OCD).. In a study in which healthy subjects were compared with individuals with OCD, significant alterations in structural connectivity were found, probably associated with a lack of myelination and axonal problems in the inferior frontal gyrus of OCD patients.

Finally, lesions in Broca's area, corresponding to Brodmann's area 44 and area 45 (opercular pair and triangular pair of the inferior frontal gyrus in the left hemisphere, respectively) have been found to imply linguistic difficulties such as those presented below:

• Problems in generating and extracting meaning from actions.
• Difficulties in sequencing motor and expressive elements.
• Semantic and syntactic problems.
• Language impoverishment. In extreme cases there may be akinetic mutism or hypolalia (decrease or delay in verbal expression).
• Decreased verbal fluency, both in phonological and semantic tasks.
• Inability to understand sayings or set phrases.