Potentials evoked by the sinusoidal modulation of the amplitude or frequency of a tone

Abstract

Steady state responses to the sinusoidal modulation of the amplitude or frequency of a tone were recorded from the human scalp. For both amplitude modulation (AM) and frequency modulation (FM), the responses were most consistent at modulation frequencies between 30 and 50 Hz. However, reliable responses could also be recorded at lower frequencies, particularly at 2-5 Hz for AM and at 3-7 Hz for FM. With increasing modulation depth at 40 Hz, both the AM and FM response increased in amplitude, but the AM response tended to saturate at large modulation depths. Neither response showed any significant change in phase with changes in modulation depth. Both responses increased in amplitude and decreased in phase delay with increasing intensity of the carrier tone, the FM response showing some saturation of amplitude at high intensities. Both responses could be recorded at modulation depths close to the subjective threshold for detecting the modulation and at intensities close to the subjective threshold for hearing the stimulus. The responses were variable but did not consistently adapt over periods of 10 min. The 40-Hz AM and FM responses appear to originate in the same generator, this generator being activated by separate auditory systems that detect changes in either amplitude or frequency.

Concurrent Encoding of Frequency and Amplitude Modulation in Human Auditory Cortex: MEG Evidence

“…Direct FM-generated aSSR, i.e., at the frequencies of ƒ FM (2.1-30 Hz), were also observed, in agreement with previous findings (Dimitrijevic et al 2001;Luo et al 2006;Picton et al 1987). For example, the stimulus with ƒ FM of 8 Hz elicited an aSSR response peak at 8 Hz, and the stimulus with ƒ FM of 30 Hz elicited an aSSR response peak at 30 Hz, in addition to any sidebands around the AM generated SSR.…”

“…This 40-Hz oscillatory activity has been proposed to result from the resonant properties of the thalamocortical system (Llinas 2000) and interactions between excitatory and inhibitory neurons (Freeman 2000). It has also been suggested that the elicited aSSRs reflect the resetting of this 40-Hz brain rhythm by transients in the sensory input, which could also explain the maximum aSSR for modulation frequency ϳ40 Hz across various stimulus types (Picton et al 1987;Rees et al 1986;Regan 1989;Ross et al 2000;Stapells et al 1984). A study of the aSSR to pure AM sound (Ross et al 2000) systematically examined the effects of stimulus properties (modulation frequency, carrier frequency) on the aSSR (amplitude and phase).…”

Mechanisms underlying cortical resonant states: implications for levodopa-induced dyskinesia

“…The ASSR is an oscillation in auditory cortex evoked by repetitive auditory stimulation at a fixed frequency. The response is most consistent around 40 Hz (Picton et al, 1987), suggesting that the neural network has a resonance at this particular frequency, which is also consistent with other experimental and theoretical data (Wang and Buzs á ki, 1996;Cardin et al, 2009). As discussed above, previous studies suggest that the 40-Hz oscillation is primarily driven by mutually connected inhibitory interneurons.…”

Age-related differences in sensitivity to small changes in frequency assessed with cortical evoked potentials

“…Similar results were reported for the frequency modulated following response (FMFR), a steady-state evoked response thought to be related to frequency discrimination. Boettcher et al (2002) reported that FMFR response amplitudes increased as a function of modulation depth over depths of 0-40%, then reached a plateau , whereas Picton et al (1987) reported a relatively linear increase in response amplitude for modulation depths of 10-70%, with increases in amplitude tapering off at higher modulation depths . Additionally, increases in response amplitudes and latencies elicited by a change in frequency were comparable to changes in response amplitudes and latencies elicited by increases in intensity, such that responses to small changes in intensity have longer latencies and smaller amplitudes than responses to larger changes in intensity (Harris et al, 2007).…”