The auditory cortex occupies a strip of brain tissue along the upper surface of each temporal lobe, roughly behind and above your ears. Its primary region sits on a small ridge called Heschl’s gyrus, which is buried within the lateral sulcus (the deep fold separating the temporal lobe from the frontal and parietal lobes above it). Far from being a single uniform patch, the auditory cortex is organized into concentric zones with distinct jobs, and it communicates with regions across both hemispheres to turn raw sound vibrations into everything from spoken words to music to the creak of a floorboard at night.
Where Exactly Is the Auditory Cortex
If you placed your finger just above the top of your ear and pressed inward, you would be pointing roughly toward the auditory cortex. It lies on the superior temporal plane, the upper surface of the temporal lobe that faces the inside of the lateral sulcus. Because this surface is folded inward, the primary auditory cortex is not visible from the outside of the brain the way the visual cortex at the back of the head is. You would need to pull apart the lateral sulcus to see Heschl’s gyrus directly.
Heschl’s gyrus is the landmark neuroscientists use to find the primary auditory cortex. Most people have one or two of these small transverse ridges on each side, though the exact number and size vary from person to person. The posteromedial portion of Heschl’s gyrus, the part closest to the midline and toward the back of the brain, is where the primary auditory cortex (sometimes labeled A1) sits. Surrounding it are secondary auditory areas that spill onto the planum temporale behind Heschl’s gyrus, the planum polare in front of it, and the lateral surface of the superior temporal gyrus.
The Core-Belt-Parabelt Hierarchy
The auditory cortex is not one undifferentiated region. Research in primates, later confirmed in humans, established that it follows a three-tier layout: core, belt, and parabelt. The core corresponds roughly to the primary auditory cortex on Heschl’s gyrus. The belt wraps around the core on the anterolateral portion of Heschl’s gyrus. The parabelt lies further out on the posterolateral superior temporal gyrus. In this scheme, sound information flows in a series: the core processes the most basic acoustic features first, sends that output to the belt for more complex analysis, and the belt in turn feeds the parabelt, which handles higher-level tasks like recognizing a familiar voice or parsing a sentence.
This hierarchy was originally mapped in non-human primates, where the core directly projects to belt areas but not to parabelt, while the belt serves as the main input source for the parabelt.1PubMed Central. Functional organization of human auditory cortex: investigation of response latencies through direct recordings Human studies using combined brain-imaging techniques have confirmed that this serial organization applies to our own auditory cortex, with response timing progressively increasing from the core outward, a pattern sometimes called “chronotopy.”2PubMed. Temporal hierarchy of cortical responses reflects core-belt-parabelt organization of auditory cortex in musicians In practical terms, the core fires first and the parabelt fires last, each stage adding a layer of interpretation to the raw signal.
Before sound even reaches the cortex, it travels from the ear through the brainstem and into the thalamus, the relay station deep in the center of the brain. The main auditory relay in the thalamus, the medial geniculate body, sends signals to the cortex through two distinct pathways. One of these pathways carries sharply tuned, frequency-specific information straight to the primary auditory cortex. The other is a broader, less frequency-specific pathway that feeds into surrounding areas and plays a role in integrating sound with other senses and with certain forms of learning.3SpringerLink / Exp Brain Res. Functional organization of lemniscal and nonlemniscal auditory thalamus
How Sound Frequencies Are Mapped
One of the auditory cortex’s most striking organizational features is tonotopy: neurons are arranged according to the sound frequencies they respond to best, forming a kind of frequency map across the cortical surface. Low-frequency sounds (bass tones) activate neurons at one end of Heschl’s gyrus, while high-frequency sounds (treble) activate neurons at the other end. This layout mirrors the arrangement of the cochlea in the inner ear, where hair cells are physically sorted by the frequencies they detect. The distribution of preferred frequencies across the primary auditory cortex roughly reflects that cochlear map.4PubMed. Sound frequency representation in primary auditory cortex is level tolerant for moderately loud, complex sounds
Tonotopy matters because it is the foundation the brain uses to decompose complex sounds into their component frequencies. When you hear a chord on a guitar, different clusters of neurons along the tonotopic gradient respond to each note in the chord. This frequency decomposition is then passed up the hierarchy to belt and parabelt regions, where the brain begins to recognize the chord as a musical entity rather than a set of unrelated tones.
The “What” and “Where” Pathways
Beyond the core-belt-parabelt hierarchy, sound information leaving the auditory cortex splits into two broad processing streams, often compared to the well-known visual “what” and “where” pathways. An anterior stream running forward along the temporal lobe handles sound identification: what you are hearing. A posterior stream running toward the parietal lobe handles spatial information: where the sound is coming from.
This dual-stream model was first demonstrated in primates. Neurons in the anterolateral belt area showed the strongest selectivity for specific vocalizations (identifying the call), while neurons in the caudolateral belt area showed the greatest spatial selectivity (locating the caller).5PubMed. Mechanisms and streams for processing of “what” and “where” in auditory cortex Human brain-imaging experiments have confirmed the same dissociation. The anterior “what” pathway runs through the anterolateral part of Heschl’s gyrus, the anterior superior temporal gyrus, and the posterior planum polare. The posterior “where” pathway runs through the planum temporale and the posterior superior temporal gyrus. Both pathways begin processing as early as about 70 to 150 milliseconds after a sound reaches the ears.6PubMed Central. Task-modulated “what” and “where” pathways in human auditory cortex
These streams are not completely independent. They overlap and share information, particularly for complex tasks like following a conversation in a noisy room, which requires simultaneously identifying the speaker’s voice (what) and tracking their location relative to background noise (where). But the separation is real enough that damage to one pathway can impair sound identification while leaving spatial hearing intact, or vice versa.
Left Brain, Right Brain, Different Listening Strengths
The auditory cortex exists in both hemispheres, and the two sides are not identical in what they do best. A well-supported model holds that the left auditory cortex excels at fine temporal resolution, the ability to track rapid changes in sound over time, while the right auditory cortex excels at fine spectral resolution, the ability to distinguish closely spaced frequencies.7Trends in Cognitive Sciences. Spectral and temporal processing in human auditory cortex
This division has real consequences. The rapid temporal changes that distinguish one speech sound from another (the difference between “ba” and “da,” for instance, comes down to a few tens of milliseconds of timing) lean heavily on the left hemisphere. Meanwhile, the fine frequency distinctions that separate one musical note from another lean more on the right. The lateralization is relative, not absolute: both hemispheres participate in both tasks, but each side carries more of the load for its specialty.
Music, Pitch, and the Right Hemisphere
The right auditory cortex’s advantage for spectral processing shows up vividly in how the brain handles musical pitch. When people listen to tones that differ by small pitch intervals, activity in the right planum temporale (a secondary auditory area behind Heschl’s gyrus) increases in a graded, linear fashion as the pitch difference grows. The corresponding region on the left side stays relatively flat across the same range, only responding when the pitch change is large.8PubMed. Evidence for the role of the right auditory cortex in fine pitch resolution In other words, the right hemisphere is tuned to notice subtle pitch shifts that the left hemisphere essentially ignores.
People with absolute pitch, the ability to name a musical note without a reference tone, carry a particularly clear anatomical signature of this asymmetry. Gray matter volume in the right Heschl’s gyrus is strongly correlated with absolute pitch proficiency. Researchers have proposed that the right Heschl’s gyrus serves as an anatomical marker for this ability, with a right-hemisphere network handling pitch perception while the left hemisphere handles the act of attaching a verbal label to the note.9Cerebral Cortex. Increased Volume and Function of Right Auditory Cortex as a Marker for Absolute Pitch
Speech Processing and Wernicke’s Area
The auditory cortex does not process speech in isolation. Situated on the left posterior superior temporal gyrus, just behind and partially overlapping with auditory association areas, is a region historically called Wernicke’s area. This area is essential for processing both heard and read language, integrating meaning and sentence structure to support comprehension.10PubMed Central. From Sound to Meaning: Navigating Wernicke’s Area in Language Processing Modern neuroimaging has revealed dense connections between Wernicke’s area and the auditory cortex, as well as with Broca’s area in the frontal lobe, which handles speech production. Sound information flows from the primary auditory cortex through belt and parabelt regions into Wernicke’s area, where it gets matched to stored word meanings.
What the primary auditory cortex contributes specifically to speech is revealed when it is damaged. Patients with bilateral infarcts to Heschl’s gyrus can develop pure word deafness, a condition in which they can still read, write, and speak spontaneously but cannot understand spoken words. They hear the sounds, but the sounds fail to resolve into recognizable speech. Interestingly, these patients can still recognize environmental sounds like a ringing phone or a dog barking, suggesting that the primary auditory cortex is essential for the fine-grained temporal analysis that speech requires, while cruder sound recognition can be handled elsewhere.11PubMed. Pure word deafness after bilateral primary auditory cortex infarcts
What Happens When Auditory Cortex Is Destroyed
When strokes or other injuries destroy the primary auditory cortex on both sides of the brain, the result is cortical deafness: a complete inability to respond to sound despite perfectly intact ears. This is an extremely rare condition because it requires bilateral damage. A stroke affecting only one temporal lobe typically causes more subtle deficits since the opposite hemisphere can still process sound.
Case reports illustrate just how devastating bilateral damage can be. One patient who suffered ischemic infarcts in both temporal lobes was initially unresponsive to all sounds. Over ten months, some basic hearing returned, improving from complete deafness to moderate-to-severe hearing loss on standard audiometry, but speech comprehension never recovered.12PubMed Central. Cortical Deafness Due to Ischaemic Strokes in Both Temporal Lobes In another case, a young woman with bilateral temporal infarcts was initially suspected of having a psychiatric disorder because her hearing seemed normal on superficial examination. Only persistence of symptoms led to a diagnosis of cortical deafness, which partially improved over three months into a condition more like pure verbal deafness, where non-speech sounds could be perceived but spoken words remained unintelligible.13PubMed. Cortical deafness of following bilateral temporal lobe stroke
The partial recovery in these cases hints that auditory association areas and subcortical structures can take over some basic hearing functions, but the primary auditory cortex seems irreplaceable for the full resolution of complex sounds, especially speech.
Tinnitus and Cortical Reorganization
Tinnitus, the perception of ringing or buzzing in the absence of an external sound, has roots in the auditory cortex’s capacity for self-reorganization. One leading hypothesis holds that when hearing is lost at certain frequencies (from noise damage, aging, or other causes), the tonotopic map in the auditory cortex reorganizes, with neurons that once responded to the lost frequencies shifting their tuning. This shift leads to an overrepresentation of frequencies near the damage boundary, which the brain may perceive as a phantom sound.14Cerebral Cortex. Structural Brain Changes in Tinnitus
This is not just theoretical. Researchers measuring cortical responses in tinnitus patients found that the representation of the tinnitus frequency was displaced from its expected tonotopic location by an average of about 5 millimeters, compared to roughly 2.5 millimeters of normal variation in healthy controls. More strikingly, the degree of cortical reorganization strongly correlated with how loud the patient perceived their tinnitus to be.15PubMed. Reorganization of auditory cortex in tinnitus The auditory cortex, in essence, creates a signal that was never in the sound wave, and the brain interprets it as real.
How the Auditory Cortex Rewires Itself
The tinnitus findings are one example of a broader principle: the auditory cortex is highly plastic, meaning it can restructure its maps and connections in response to experience or deprivation. This plasticity is most dramatic during early development but persists to some degree throughout life.
In animal studies, rat pups raised in continuous moderate-level noise showed delayed maturation of their primary auditory cortex. The normal emergence of orderly tonotopic maps and sharply tuned neuronal responses was pushed far beyond typical developmental timelines. Remarkably, when those noise-reared rats were later exposed to specific tones, the cortex rapidly reorganized in a way characteristic of the critical period, suggesting that the early noise exposure had essentially kept the critical-period window of plasticity open well past its normal closing point.16PubMed. Environmental noise retards auditory cortical development
In deaf humans, the plasticity takes a different form. Because the auditory cortex receives no sound input, it gets recruited by other senses. Visual tasks, for instance, robustly activate the auditory cortex in deaf individuals, with peak activation in the posterior-lateral part of high-level auditory areas. The fascinating detail is that the cortex appears to preserve its computational role even while switching input channels: the same areas that would normally process a particular type of auditory pattern end up processing an analogous type of visual pattern.17PubMed Central. Task-specific reorganization of the auditory cortex in deaf humans This cross-modal takeover is part of the reason why cochlear implant outcomes vary: if the auditory cortex has been extensively repurposed for vision, reintroducing sound may compete with well-established visual processing.
Aging and the Auditory Cortex
Plasticity can also work against you as you age. Age-related hearing loss, particularly the common pattern of losing high-frequency sensitivity, leaves a measurable structural footprint in the brain. Imaging studies have found that gray matter volume in a specific subregion of the primary auditory cortex (known as Te1.0) decreases in proportion to the severity of high-frequency hearing loss. Elevated cerebrospinal fluid in the same area suggests that brain tissue is actually atrophying, not just becoming less active.18PubMed Central. Auditory cortex signs of age-related hearing loss This finding underscores why hearing loss is not just an ear problem: the brain itself changes in ways that may make rehabilitation harder the longer hearing loss goes unaddressed.
Multisensory Integration
Despite its name, the auditory cortex does not deal exclusively in sound. It participates in combining information from multiple senses, particularly during speech perception. When you watch someone’s face while they talk, visual information about lip movements reaches the auditory cortex and changes how it responds. Adding congruent visual speech to auditory speech produces a measurable increase in signal amplitude in auditory cortex, meaning the cortex fires more strongly when it can see the speaker’s mouth than when it hears the voice alone.19PLOS ONE. An fMRI Study of Audiovisual Speech Perception Reveals Multisensory Interactions in Auditory Cortex
When visual and auditory speech signals conflict (as in the famous McGurk illusion, where a voice saying one syllable is paired with lips mouthing a different one), a wider network of brain regions is recruited to try to resolve the mismatch. A meta-analysis of audiovisual speech studies found that conflicting signals activated dorsal-stream regions across the frontal, parietal, and temporal lobes, while the bilateral posterior superior and middle temporal cortex showed consistent activity across all types of audiovisual speech contrasts, whether the signals agreed, disagreed, or produced a fused percept.20PubMed Central. An ALE meta-analysis on the audiovisual integration of speech signals
Auditory Hallucinations
If the auditory cortex can generate phantom sounds in tinnitus, it should come as little surprise that it is also implicated in auditory hallucinations, the “voices” experienced by many people with schizophrenia and some other conditions. Auditory hallucinations appear to originate from abnormal spontaneous activation within speech-related areas of the temporal lobe. One model describes them as initiated by hyper-activation of temporal lobe neurons, drawing attention inward, combined with reduced inhibition from the frontal lobe that would normally keep such activity in check.21PubMed Central. Auditory hallucinations: A review of the ERC “VOICE” project
A coordinate-based meta-analysis of brain-imaging studies confirmed that during auditory verbal hallucinations, patients show increased activation across a bilateral network that includes the middle and superior temporal gyri (auditory cortex territory), Broca’s area, the anterior insula, and the hippocampal region, among other areas.22PubMed. Cortical activations during auditory verbal hallucinations in schizophrenia: a coordinate-based meta-analysis The involvement of both speech-production and speech-perception areas suggests that hallucinated voices share neural circuitry with actual speech processing, which helps explain why they sound so convincingly real to the person experiencing them.
Deviance Detection and Predictive Coding
One of the auditory cortex’s most useful tricks is its ability to detect when a sound breaks an expected pattern. If you hear a repeated tone, your auditory cortex quickly builds a prediction that the next sound will be the same. When an unexpected sound arrives instead, the cortex generates a strong response known as the mismatch negativity, an electrical signature that can be measured through scalp electrodes. At the level of individual neurons, a related phenomenon called stimulus-specific adaptation causes cells to gradually reduce their response to a repeated sound while remaining fully responsive to a novel one. These two phenomena, one measured at the macroscopic level and one at the microscopic level, are increasingly viewed as different scales of the same underlying mechanism: the auditory cortex acting as a prediction engine, continuously matching incoming sounds against an internal model and flagging deviations.23PubMed Central. The Neuronal Basis of Predictive Coding Along the Auditory Pathway: From the Subcortical Roots to Cortical Deviance Detection
This deviance-detection system is what lets you ignore the steady hum of an air conditioner but snap to attention when it suddenly stops. It also underlies the ability to pick out a friend’s voice in a crowded room: the brain predicts the ambient noise and highlights whatever does not match the prediction.
How Humans and Other Primates Compare
The basic architecture of the auditory cortex, its core-belt-parabelt layout and its dual “what” and “where” pathways, is shared across primates. The monkey auditory cortex looks in many ways like a smaller version of the human one, with a ventral stream for sound identification and a dorsal stream for spatial processing that closely parallel the human versions.24PubMed Central. Where did language come from? Precursor mechanisms in nonhuman primates
But the resemblance has limits. High-resolution diffusion MRI comparing marmosets, macaques, and humans found that the ventral (what) pathway is well conserved across all three species but extends to more anterior temporal regions in humans. The dorsal (where) pathway, by contrast, showed clear divergence between monkeys and humans, with human-specific expansions that may support the neural networks underlying speech and language.25PubMed Central. Evolutionary continuity and divergence of auditory dorsal and ventral pathways in primates revealed by ultra-high field diffusion MRI There is also a temporal-processing difference: human primary auditory cortex appears tuned to longer time windows than macaque primary auditory cortex, a shift that may reflect evolutionary pressure toward processing speech, which unfolds over slower timescales than the brief vocalizations most other primates use.26PubMed. Evidence for evolutionary divergence in temporal integration windows between human and monkey auditory cortex
How Scientists Map the Auditory Cortex in Living People
Much of what we know about auditory cortex function in humans comes from a handful of complementary techniques. Functional MRI detects changes in blood flow that indicate which brain areas are active during a listening task, and it provides good spatial resolution but relatively slow time resolution. Electroencephalography (EEG) and magnetoencephalography (MEG) offer much finer time resolution, on the order of milliseconds, but are less precise about exactly where in the brain the signal originates.
A uniquely powerful approach comes from patients undergoing surgery for drug-resistant epilepsy. Before the operation, electrodes are implanted directly on or within the brain to locate seizure foci. While those electrodes are in place, researchers can play sounds and record the cortical response with spatial and temporal precision unmatched by any non-invasive method.27PubMed Central. Auditory processing in the human cortex: An intracranial electrophysiology perspective These direct recordings have been instrumental in confirming the core-belt-parabelt hierarchy in living humans and in mapping fine details like pitch processing. In one study, local field potentials recorded from depth electrodes in Heschl’s gyrus and grid electrodes over the lateral superior temporal gyrus showed pitch-related responses across both core and non-core auditory regions, with onset latencies of roughly 70 milliseconds.28PubMed Central. Direct electrophysiological mapping of human pitch-related processing in auditory cortex Such recordings are rare, since they require a clinical justification for the electrode placement, but they remain the gold standard for understanding what auditory cortex neurons actually do in humans.