Sound localization in the horizontal plane is the auditory system’s remarkable ability to determine the direction of sound sources in a left-right dimension. This process primarily depends on binaural auditory cues that the brain processes to enable accurate spatial hearing.

Key Mechanisms of Horizontal Sound Localization

1. Interaural Time Difference (ITD)

When a sound originates from one side, it reaches the nearer ear slightly before the far ear, creating a time difference known as the interaural time difference (ITD). The human auditory system can detect differences as small as microseconds, making ITD a critical cue especially for low-frequency sounds.biologyinsights+1

2. Interaural Phase Difference

For periodic sounds, the auditory system can also rely on the difference in phase of the sound waves between the two ears (interaural phase difference), which provides additional spatial information about the azimuthal location of the sound source.pmc.ncbi.nlm.nih

3. Interaural Level Difference and Tuning Curves

Apart from timing and phase, interaural level difference (ILD) is a cue based on the difference in loudness of sounds reaching each ear, mainly effective for high-frequency sounds due to the head’s acoustic shadow.

Tuning curves of auditory nerves relate to frequency sensitivity rather than spatial localization directly; thus differences in tuning curves between two auditory nerves do not primarily explain horizontal localization.auditoryneuroscience+1

4. Neural Pathways Involved

• The superior olivary nucleus, especially its medial and lateral parts, is a key brainstem site that processes ITD and ILD cues, playing a central role in horizontal sound localization.

• The auditory cortex is also involved in higher-order processing of sound location and interpretation.

Evaluating the Statements

• A. The difference in time between the arrival of stimulus in two ears: Correct; ITD is a fundamental localization cue.

• B. The difference in phase of the sound waves on two ears: Correct; phase difference is important for certain types of sounds.

• C. The difference in tuning curves of two auditory nerves: Incorrect; tuning curves relate to frequency selectivity, not localization.

• D. The activity of neurons in superior olivary nucleus, but not by the neuronal activity of auditory cortex: Incorrect; auditory cortex activity also contributes to spatial hearing.

Which Statements Are NOT Correct?

Statements C and D are not correct.

Final Answer

The option indicating which statements are NOT correct is:

(4) C and D