Gyrus and sulcus are terms used to describe brain anatomy. Brain tissue is folded upon itself; the top of a fold is known as a gyrus and the trough is called a sulcus. The inferior frontal gyrus makes up part of the frontal lobe of the cerebrum. If a human brain is seen from the side, it could be said to roughly resemble a boxing glove or a mitten. Looking at it this way, the inferior frontal gyrus would be located in the larger portion of the "glove," immediately above the separate thumb area.
There are three anatomical areas within the inferior frontal gyrus. The Pars opercularis is the anterior or forward-most area and is roughly related to the brain mapping Brodmann area 44, also known as Broca's area. The Pars triangularis lies behind the Pars opercularis and corresponds to Brodmann area 45. Finally, the Pars orbitalis is the posterior limit of the inferior frontal gyrus and is associated with Brodmann area 47. The entire area receives its blood supply from the middle cerebral artery.
Scientists continue to discover functions of this area of the brain, many of which are related to our ability to live sociably and communicate with others. A study by Jabbi and Keysers demonstrated the involvement of the inferior frontal gyrus in our interpretations of facial expressions and a corresponding emotional response appropriate to the expression. Another study in the European Journal of Neuroscience identified damage or stimulation specific to the Pars opercularis as interfering with normal language production. Yet another experiment connected the Pars opercularis with observation and imitation of appropriate behaviors, an ability that autistic children have difficulty performing.
Some behaviors appear to be related to either the left or right inferior frontal gyrus. A study in the journal Neuroscience shows a correlation between an avoidance of risky behavior and greater excitation in the right inferior frontal gyrus. The converse also seems to be related: riskier choices and behaviors demonstrated by patients with lesions or injury on the right gyrus. Functions specific to the left inferior frontal gyrus include many language-related tasks. Part of the human ability to comprehend syntax and syntactic processing as well as overall language comprehension seems to be located in this area. Multiple studies have related overall language fluency to this area.