The superior temporal gyrus is a ridge of cortex running along the upper edge of each temporal lobe, and it serves as the brain’s primary hub for hearing, speech comprehension, voice recognition, and several forms of social perception. If you trace a line just above your ear and slightly backward, you are roughly following its path beneath the skull. Although it is sometimes reduced to “the hearing part of the brain,” the STG does far more than register sound: it transforms raw acoustic signals into meaningful speech, merges what you hear with what you see, helps you recognize who is speaking, and even participates in reading other people’s intentions from their body language and eye gaze.
Where It Sits and What It Looks Like
The superior temporal gyrus is the topmost of the three horizontal ridges that make up the temporal lobe on each side of the brain. It is bounded above by the lateral sulcus (also called the Sylvian fissure), which separates the temporal lobe from the frontal and parietal lobes, and below by the superior temporal sulcus, a deep groove that divides it from the middle temporal gyrus. The gyrus stretches from the temporal pole at the front to the junction with the parietal lobe at the back, giving it a roughly finger-shaped footprint on the brain’s lateral surface.
Hidden on the upper surface of the STG, tucked inside the lateral sulcus where you cannot see it from the outside, sits Heschl’s gyrus, a small transverse ridge that houses the primary auditory cortex. Heschl’s gyrus is where sound first arrives in the cortex after traveling up from the brainstem, and it processes basic acoustic features before passing information outward to the rest of the STG for more complex analysis.1PubMed Central. Functional characterization of human Heschl’s gyrus in response to natural speech The lateral surface of the gyrus, visible when you look at the brain from the side, has historically been labeled Brodmann area 22. However, detailed mapping using both cell-structure analysis and receptor-density profiling has identified a distinct cortical zone called Te3 that occupies only the lateral bulge of the STG and does not extend as far onto the upper and lower banks of the gyrus as Brodmann’s original area 22 implied.2PubMed. Multimodal architectonic mapping of human superior temporal gyrus In practical terms, the STG is not one uniform sheet of cortex but a patchwork of subregions with different cellular architecture and different jobs.
Auditory Processing and the Tonotopic Map
The most fundamental role of the STG is hearing. Sound enters the cortex at Heschl’s gyrus, which is organized tonotopically, meaning different parts of it respond best to different pitches. Imaging studies have identified two mirror-image frequency gradients running along Heschl’s gyrus: one stretching toward the back of the brain and another toward the front, with a zone on the lateral aspect of the gyrus that responds preferentially to lower frequencies and zones anterior and posterior to it that prefer higher frequencies.3PubMed Central. Tonotopic organization of human auditory cortex Studies using frequency-swept stimuli have identified at least six separate tonotopic progressions across the superior temporal plane, suggesting the auditory cortex contains multiple distinct maps of pitch rather than a single gradient.4PubMed. Tonotopic organization in human auditory cortex revealed by progressions of frequency sensitivity These frequency preferences in and around Heschl’s gyrus match current models of how primary auditory cortex is organized, and the pattern of narrow frequency selectivity observed aligns with findings from brain-imaging research.5Frontiers in Neuroscience. Mapping tonotopic organization in human temporal cortex: representational similarity analysis in EMEG source space
Once these basic pitch-and-timing features are extracted in Heschl’s gyrus, the signal fans out across the lateral STG and the superior temporal sulcus, where increasingly complex features are assembled. This is where raw sound starts becoming something recognizable: a voice, a word, a melody. The transformation from simple acoustic features to complex ones happens in a graded way along the auditory hierarchy, not as a single dramatic leap.1PubMed Central. Functional characterization of human Heschl’s gyrus in response to natural speech
Language and Speech Perception
The posterior portion of the left STG has long been called Wernicke’s area, traditionally described as the brain’s center for understanding spoken language. The real picture is more nuanced. Modern imaging and lesion studies converge on the finding that this region plays a larger role in speech production than the classical textbook model suggested, and that word and sentence comprehension depend on the middle STG and middle-posterior superior temporal sulcus rather than the posterior STG alone.6PubMed Central. The Wernicke area: Modern evidence and a reinterpretation Lesion-mapping work in patients with brain damage has largely agreed with the classical idea that this stretch of cortex supports both word and sentence comprehension, while also pointing to a supporting role for the temporal pole, the forward tip of the temporal lobe.7Brain. The Wernicke conundrum revisited: evidence from connectome-based lesion-symptom mapping
An important caveat: much of what we know about Wernicke’s area comes from stroke patients, whose damage tends to destroy deep white-matter tracts along with the cortex itself and causes widespread network disruption in the acute phase. Studies of patients with progressive neurodegenerative diseases, where cortical thinning happens gradually without the same white-matter devastation, have sometimes told a different story about which parts of the temporal cortex are truly essential for comprehension.8PubMed Central. Word comprehension in temporal cortex and Wernicke area: A PPA perspective The upshot is that “Wernicke’s area” remains a useful shorthand, but the borders and functions it points to are fuzzier than most textbooks admit.
Why the Left Side Matters More for Speech
Language processing in the STG is heavily lateralized to the left hemisphere in most people. A brain-stimulation study used targeted magnetic pulses to briefly disrupt different parts of the STG while participants listened to speech. Disrupting the left anterior STG significantly worsened accuracy in perceiving speech, while disrupting the right anterior STG did not produce a comparable drop. The difference between left anterior and left posterior STG stimulation did not reach statistical significance, but the left-versus-right contrast was clear, providing causal evidence that the left anterior STG plays a necessary role in speech perception.9PubMed. The role of left vs. right superior temporal gyrus in speech perception: An fMRI-guided TMS study
Children, interestingly, rely on the STG differently than adults do. During spoken-word processing, children show stronger functional connectivity in Heschl’s gyrus, the STG, and subcortical areas compared to adults, whose processing has shifted toward more specialized dorsal and ventral pathways for handling the sounds and meanings of words separately.10PubMed. Developmental differences of large-scale functional brain networks for spoken word processing In other words, the STG starts out doing heavy lifting for language in childhood, and over development, some of that work gets distributed to other networks.
Voice Recognition and Social Perception
Beyond decoding the words someone says, the STG and its neighbor the superior temporal sulcus help you figure out who is saying them and what they might be feeling. Voice selectivity increases as signals move along the auditory hierarchy from the upper surface of the temporal lobe outward to the STG and the sulcus below it. Recordings from human auditory cortex show that the STG and STS can accurately distinguish human vocalizations from other sounds even when no linguistic content is present, and that neural responses in these areas are best explained by a combination of voice category and acoustic features rather than acoustics alone.11PubMed Central. Voice coding in human superior temporal cortex
Familiarity matters, too. When people listen to voices they know, the temporal lobes produce stronger activation than for unfamiliar voices, with activation clusters lining up along the upper and lower banks of the superior temporal sulcus. Named, recognizable voices evoke a stronger blood-oxygen signal than voices that are merely somewhat familiar, which in turn produce a stronger response than completely unknown voices.12PLOS ONE. The Temporal Lobes Differentiate between the Voices of Famous and Unknown People: An Event-Related fMRI Study on Speaker Recognition The STG region essentially acts as a graded identity detector for voices, scaling its response with how well you know the speaker.
The superior temporal sulcus, which runs just below the STG, is also deeply involved in broader social cognition, from perceiving biological motion and tracking eye gaze to interpreting more complex social signals.13PubMed. Social cognition and the superior temporal sulcus: implications in autism Because the STG and STS work so closely together, damage or atypical development in this region can ripple into difficulties with social understanding, a pattern that shows up in autism research.
Merging What You Hear With What You See
You might not think of the STG as a visual area, but it plays a central role in audiovisual integration, the process of combining sounds and sights into a unified perception. A large coordinate-based meta-analysis pooling over 120 studies found that audiovisual integration consistently converges on the bilateral STG, among other sites including the middle temporal gyrus, occipital regions, frontal areas, and the insula.14Cerebral Cortex. Audiovisual integration in the human brain: a coordinate-based meta-analysis In everyday life, this is what lets you understand someone more easily in a noisy room when you can see their lips moving.
The STG’s role in audiovisual speech integration is clinically relevant. Fluent readers show greater STG activation for combined audiovisual speech compared to audio-only or visual-only stimuli, and this integration process appears to be disrupted in people with dyslexia.15PubMed. Audiovisual speech integration in the superior temporal region is dysfunctional in dyslexia At a finer level, seeing a speaker’s lip movements sharpens the STG’s ability to distinguish individual speech sounds. Congruent audiovisual speech improves the brain’s decoding of phonemes, speeds up the timing of successful decoding, and produces the biggest boost for the consonants at the beginnings of words rather than the vowel portions.16PubMed Central. Visual speech enhances phoneme separability in human superior temporal gyrus
White-Matter Connections
The STG does not work in isolation. It is connected to distant cortical regions by long-range white-matter fiber bundles. Diffusion-based tractography has shown that the most posterior part of the STG sends fibers arching around the back of the Sylvian fissure to reach the caudal dorsolateral frontal cortex, a pathway confirmed in the majority of subjects examined and consistent with what has been found in non-human primate anatomy.17Journal of Neuroscience. Dissociating the Human Language Pathways with High Angular Resolution Diffusion Fiber Tractography This connection is part of the dorsal language stream, which links auditory representations with articulatory motor plans for speech.
Resting-state imaging shows that the STG is functionally linked to multiple large-scale brain networks. In both hearing and deaf individuals, the STG shows positive connectivity with bilateral superior temporal regions, the insula, the Rolandic operculum, pre- and postcentral gyri, the dorsal anterior cingulate cortex, and the dorsolateral prefrontal cortex, spanning auditory, salience, and sensorimotor networks.18Scientific Reports. Enhanced spontaneous functional connectivity of the superior temporal gyrus in early deafness This broad connectivity profile helps explain why the STG participates in such a wide range of functions beyond simple hearing.
Schizophrenia and Auditory Hallucinations
The STG has been one of the most consistently implicated brain regions in schizophrenia, particularly in connection with auditory hallucinations, the experience of hearing voices that are not there. Early MRI work demonstrated that young patients with schizophrenia had smaller left superior temporal gyral volume, and the degree of shrinkage was strongly and selectively correlated with how severe their auditory hallucinations were.19PubMed. Auditory hallucinations and smaller superior temporal gyral volume in schizophrenia
Subsequent meta-analyses have reinforced and refined this finding. One meta-analysis reported that the severity of auditory verbal hallucinations was associated with decreased gray matter volume in the left STG and left posterior insula, with the structural atrophy concentrated in circuits involved in generating and perceiving speech as well as processing auditory signals.20PubMed Central. Hearing voices in the head: Two meta-analyses on structural correlates of auditory hallucinations in schizophrenia A separate meta-analysis found a similar relationship between hallucination severity and reduced gray matter in the left insula and right STG, suggesting both hemispheres may contribute through somewhat different mechanisms.21PubMed. Structural correlates of auditory hallucinations in schizophrenia: a meta-analysis
Beyond structure, the STG also shows disrupted functional connectivity in schizophrenia. A meta-analysis of resting-state connectivity studies found reduced connections between seed regions and the right superior temporal cortex, among other areas, in patients compared to healthy controls.22Frontiers in Psychiatry. Dysconnectivity of Multiple Brain Networks in Schizophrenia: A Meta-Analysis of Resting-State Functional Connectivity The picture that emerges is one of an auditory-language hub that is both structurally smaller and functionally disconnected in people who experience persistent voice-hearing.
Autism and the STG
The STG also shows atypical development in autism spectrum disorder, though the pattern differs from schizophrenia. Rather than being smaller, the right STG has been found to be significantly larger in children and adolescents with autism compared to controls, with the increase concentrated in the right posterior portion of the gyrus even after accounting for overall brain size.23PubMed Central. Enlarged Right Superior Temporal Gyrus in Children and Adolescents with Autism When growth trajectories are plotted by age, the STG appears to follow a different developmental path in autism, with findings suggesting a possible failure in left-hemisphere lateralization of language function involving this region.24PubMed. Superior temporal gyrus, language function, and autism
Functional connectivity studies in children with autism have found decreased outgoing connectivity from the right STG during social tasks, alongside increased connectivity in the right cingulate gyrus.25Frontiers in Neuroscience. Impaired effective functional connectivity in the social preference of children with autism spectrum disorder Given the STG and neighboring sulcus’s role in processing biological motion, eye gaze, and voice identity, disrupted connectivity here could contribute to the social-communication difficulties that define the condition.
What Happens When Hearing Is Lost
One of the most striking demonstrations of what the STG can do comes from studying people who have been deaf since birth or early childhood. In the absence of auditory input, the STG does not simply go silent. Instead, it gets repurposed. A meta-analysis of 47 studies found that deaf participants consistently showed greater activation than hearing participants in bilateral temporal cortex spanning anterior to posterior STG, regions that would normally process sound.26iScience. Differential cross-modal plasticity of the superior temporal gyrus in deaf individuals: A coordinate-based meta-analysis This cross-modal plasticity means the STG starts responding to visual and tactile stimuli instead.
The right planum temporale, a region on the upper surface of the STG normally involved in higher-order auditory processing, reorganizes in deaf individuals to become sensitive to visual motion, and the degree of white-matter structural integrity in this area correlates with how well a deaf person detects visual motion.27PubMed. White matter structure in the right planum temporale region correlates with visual motion detection thresholds in deaf people Meanwhile, in deaf adults processing nonverbal communication such as sign language, the left STG shows convergent activation, indicating that the auditory cortex is being recruited for visual-spatial language processing.28PubMed Central. Nonverbal Communication Processing in Deaf Adults: An Activation Likelihood Estimation Meta-Analysis Even the resting-state connectivity of the STG changes in early deafness, with enhanced connections to visual and other non-auditory networks.18Scientific Reports. Enhanced spontaneous functional connectivity of the superior temporal gyrus in early deafness
This plasticity has practical implications for cochlear implant candidates. If the STG has been extensively remapped to serve vision, restoring auditory input later in life may not produce the same outcomes as implantation in early childhood, when the cortex is still awaiting its “expected” auditory input.
An Evolutionary Perspective
The STG is not unique to humans, but its connectivity has undergone significant modification across primate evolution. Comparative tractography shows that the main longitudinal fiber bundles connecting the temporal lobe exist in macaques, great apes, and humans, but with important differences at each stage. In chimpanzees and humans, the inferior longitudinal fasciculus separates into subcomponents not observed in macaques. Most strikingly, the arcuate fasciculus, the bundle most associated with language, extends deeply into the temporal cortex only in humans; this expansion was not found in chimpanzees or gorillas.29PLOS Biology. Longitudinal connections and the organization of the temporal cortex in macaques, great apes, and humans The differences between monkey and human temporal cortex did not arise from a single evolutionary event but from a series of changes in white-matter architecture accumulated across lineages.
Volumetric comparisons tell a complementary story. Apes and monkeys scale along different trajectories when temporal lobe structures are plotted against total brain volume. Humans have significantly larger temporal lobe volume, surface area, and white matter than predicted even by ape regression lines, suggesting an expansion above and beyond what overall brain enlargement would explain.30PubMed. A quantitative morphometric comparative analysis of the primate temporal lobe This outsized temporal lobe, and the unique white-matter connections within it, likely provided the neural substrate that made human-level language and social cognition possible.
Music Perception and Amusia
The STG’s auditory prowess extends to music. The right STG in particular is involved in processing pitch changes and tonal memory, both foundational to perceiving melody. In congenital amusia, a condition where people are unable to recognize or enjoy music despite having normal hearing, the right STG’s role is debated: some imaging studies show normal pitch processing in this region while others show abnormalities. The current evidence points to a breakdown not within the STG itself but in the connection between the right STG and the right inferior frontal gyrus, a pathway needed for conscious analysis of musical pitch.31Handbook of Clinical Neurology. Amusia Damage to the posterior left STG, meanwhile, can produce a different kind of musical loss: patients have reported that musical tones all sound identical and that songs sound like screaming.32Austin Journal of Clinical Neurology. Musical Processing in the Brain: A Neuropsychological Approach through Cases with Amusia
Brain-Computer Interfaces and the STG
The STG’s detailed representation of speech sounds has made it a prime target for brain-computer interface research aimed at restoring communication to people who have lost the ability to speak. Neural speech decoding is a relatively young field, but researchers have demonstrated that electrodes placed directly on the cortical surface over the STG and neighboring areas can decode phonemes continuously from the high-gamma-band power of local field potentials, working toward systems with arbitrary vocabulary sizes rather than pre-set word lists.33Journal of Neural Engineering. Neural speech recognition: continuous phoneme decoding using spatiotemporal representations of human cortical activity Chronic electrocorticography over the STG has shown promise for auditory and articulatory decoding, raising the prospect of devices that could translate a paralyzed person’s intended speech into text or synthesized audio in real time.34PubMed Central. The Potential for a Speech Brain-Computer Interface Using Chronic Electrocorticography The STG’s fine-grained, phoneme-level encoding of speech makes it an unusually information-rich recording site for this kind of technology.