Abstract
The purpose of this study was to compare cortical brain responses evoked by amplitude modulated acoustic beats of 3 and 6 Hz in tones of 250 and 1000 Hz with those evoked by their binaural beats counterparts in unmodulated tones to indicate whether the cortical processes involved differ. Event-related potentials (ERPs) were recorded to 3- and 6-Hz acoustic and binaural beats in 2000 ms duration 250 and 1000 Hz tones presented with approximately 1 s intervals. Latency, amplitude and source current density estimates of ERP components to beats-evoked oscillations were determined and compared across beat types, beat frequencies and base (carrier) frequencies. All stimuli evoked tone-onset components followed by oscillations corresponding to the beat frequency, and a subsequent tone-offset complex. Beats-evoked oscillations were higher in amplitude in response to acoustic than to binaural beats, to 250 than to 1000 Hz base frequency and to 3 Hz than to 6 Hz beat frequency. Sources of the beats-evoked oscillations across all stimulus conditions located mostly to left temporal lobe areas. Differences between estimated sources of potentials to acoustic and binaural beats were not significant. The perceptions of binaural beats involve cortical activity that is not different than acoustic beats in distribution and in the effects of beat- and base frequency, indicating similar cortical processing.
Highlights
IntroductionWhen two sinusoids of steady amplitude but with slightly different frequencies are summated, their interference results in periodic amplitude fluctuations whose frequency corresponds to the frequency difference between the sinusoids
The oscillatory potentials evoked by the acoustic beats were a quarter of a period removed from their counterparts to binaural beats when embedded in a tone with an abrupt onset (Fig. 3)
In this study brain potentials associated with amplitude modulated tones were compared to their counterparts evoked by stimulating each ear with a slightly different tone to produce a perception of amplitude modulation
Summary
When two sinusoids of steady amplitude but with slightly different frequencies are summated, their interference results in periodic amplitude fluctuations whose frequency corresponds to the frequency difference between the sinusoids. When such a mix of tones is presented to the same ear, the percept is of amplitude modulation ‘‘beats” occurring at a rate corresponding to the frequency difference between the two tones. When a tone of one frequency and steady intensity is presented to one ear and a similar tone of slightly different frequency is presented to the other ear, sound intensity to either ear is steady, a perception of amplitude modulated ‘‘beats” that are localized to the middle of the head is experienced. The perceived beat frequency corresponds to the frequency difference between the tones presented to each
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
