The temporal gyrus represents a prominent fold of tissue located on the surface of the temporal lobe, one of the four major divisions of the brain. This structure is a fundamental part of the cerebrum, positioned behind the temples and beneath the lateral fissure. It serves as a highly organized hub for processing sensory input and transforming it into meaningful perception. This collective area is deeply intertwined with complex cognitive functions, such as language comprehension, memory formation, and the recognition of objects.
Anatomical Mapping of the Temporal Gyri
The lateral surface of the temporal lobe is organized into three distinct, roughly parallel horizontal folds separated by shallow grooves called sulci. These three major folds are the Superior Temporal Gyrus (STG), the Middle Temporal Gyrus (MTG), and the Inferior Temporal Gyrus (ITG). The STG is positioned highest, bordering the lateral sulcus, which separates the temporal lobe from the frontal and parietal lobes. The MTG lies immediately below the STG, situated between the superior and inferior temporal sulci, while the ITG is the lowest of the three, extending around the inferior edge of the hemisphere. Neuroscientists have mapped specific cortical fields, known as Brodmann areas, onto these structures. The STG contains areas 22, 41, and 42, the MTG corresponds to area 21, and the ITG to area 20.
Core Functions: Auditory Processing and Language Comprehension
The Superior Temporal Gyrus (STG) processes and interprets auditory information. Heschl’s gyrus, located within the STG, contains the Primary Auditory Cortex, the first cortical region to receive sound input from the ears. This area is organized tonotopically, meaning specific sound frequencies map precisely onto distinct locations, allowing for the basic perception of pitch and loudness.
The posterior portion of the STG houses Wernicke’s Area, which is typically located in the left hemisphere and is fundamental for language comprehension. This region (Brodmann Area 22) interprets the meaning of spoken language by decoding phonemes and matching them to known word patterns. Damage to this area can impair a person’s ability to understand speech, even if their hearing remains intact.
The Role in Memory and Recognition
The Middle and Inferior Temporal Gyri (MTG and ITG) integrate sensory information with stored knowledge for recognition and memory. The ITG acts as a high-level processing station at the end of the ventral visual stream, often called the “What” pathway. This pathway processes complex visual features, such as shape, color, and texture, necessary for identifying and categorizing objects, including highly specific stimuli like faces.
The MTG is a major contributor to semantic memory, the repository for factual knowledge, concepts, and the meaning of words. These gyri maintain strong connections with medial temporal lobe structures, including the hippocampus, which facilitates the storage and retrieval of long-term declarative memories.
When the Temporal Gyrus is Disrupted
Damage to the temporal gyrus, often caused by stroke, trauma, or neurodegenerative disease, results in deficits reflecting the compromised area’s function. Injury to Wernicke’s Area in the posterior Superior Temporal Gyrus can lead to receptive aphasia, a condition where individuals struggle to comprehend spoken language, often speaking fluently but without meaning. Disruption to the Primary Auditory Cortex can cause auditory agnosia, meaning a person can hear sounds but cannot recognize or distinguish them, such as identifying a ringing phone or a siren.
Damage affecting the Inferior Temporal Gyrus and the ventral visual pathway can result in visual agnosia. This makes it difficult to recognize familiar objects, people, or pictures, even though vision itself is unimpaired. The temporal lobe is also a common site for the onset of seizures in Temporal Lobe Epilepsy (TLE), where abnormal electrical activity temporarily impairs memory and language function. Repeated seizures in TLE can sometimes cause atrophy of the hippocampus, contributing to chronic memory problems.