Auditory White Noise Research Articles

Listen to the noise: noise is beneficial for cognitive performance in ADHD

Noise is typically conceived of as being detrimental to cognitive performance. However, given the mechanism of stochastic resonance, a certain amount of noise can benefit performance. We investigate cognitive performance in noisy environments in relation to a neurocomputational model of attention deficit hyperactivity disorder (ADHD) and dopamine. The Moderate Brain Arousal model (MBA; Sikström & Söderlund, 2007) suggests that dopamine levels modulate how much noise is required for optimal cognitive performance. We experimentally examine how ADHD and control children respond to different encoding conditions, providing different levels of environmental stimulation. Participants carried out self-performed mini tasks (SPT), as a high memory performance task, and a verbal task (VT), as a low memory task. These tasks were performed in the presence, or absence, of auditory white noise. Noise exerted a positive effect on cognitive performance for the ADHD group and deteriorated performance for the control group, indicating that ADHD subjects need more noise than controls for optimal cognitive performance. The positive effect of white noise is explained by the phenomenon of stochastic resonance (SR), i.e., the phenomenon that moderate noise facilitates cognitive performance. The MBA model suggests that noise in the environment, introduces internal noise into the neural system through the perceptual system. This noise induces SR in the neurotransmitter systems and makes this noise beneficial for cognitive performance. In particular, the peak of the SR curve depends on the dopamine level, so that participants with low dopamine levels (ADHD) require more noise for optimal cognitive performance compared to controls.

The perception of auditory-tactile integration

This project explores the perceptual interactions between certain auditory and tactile stimuli in an objective manner. Our hypothesis states that if the auditory and tactile systems integrate into a common pathway, the d‐prime measure of the two sensory stimuli presented simultaneously will be significantly greater than the d‐prime measure of the individual sensory stimuli. If the stimuli are judged independently, the resulting d‐prime will be close to the root‐squared sum of the individual sensory d‐primes. If the stimuli are integrated into a single percept, the d‐prime will be close to the sum of the individual d‐primes. This experiment presents 250 Hz vibratory stimuli to the fingertip and 250 Hz tones binaurally at the subject’s detection threshold. Experimental measurements of d‐prime were obtained for auditory‐alone, tactile‐alone, and combination of auditory plus tactile. All testing used auditory white noise of 50 dB SPL. Effects of relative tactile‐auditory phase and temporal asynchrony of the stimuli are explored. Preliminary data suggest that under certain conditions the two sensory stimuli integrate in a common pathway to form a single percept, that the stimuli must be synchronous for integration to occur, and that relative tactile‐auditory phase has no effect on integration. [Hertz Foundation, NIH RO1‐DC000126‐25, ROI‐DC000117.]

Auditory sensory memory for random waveforms in the Mongolian gerbil

Mongolian gerbils ( N=21) were trained to discriminate between continuous and repeated auditory white noise. While for periods up to 40 ms of the repeated noise spectral effects make this a perceptual task, longer periods require auditory sensory memory to solve the task. Short periods (20 ms) could easily be discriminated by naive gerbils (discrimination performance, i.e. hit rate minus false alarm rate >80% after 8 days of training). Discrimination was more difficult for longer periods (100 ms: discrimination performance ≈50% after 18 days of training). By long-term training (156 days) using an optimized training paradigm two further gerbils learned to discriminate up to a period length of 360 ms but could not proceed at 400 ms. While this falls short of human performance, it demonstrates for the first time sensory memory for random waveforms in animals.

Modification of sudden onset auditory ERP by involuntary attention to visual stimuli

To investigate the cross-modal nature of the exogenous attention system, we studied how involuntary attention in the visual modality affects ERPs elicited by sudden onset of events in the auditory modality. Relatively loud auditory white noise bursts were presented to subjects with random and long inter-trial intervals. The noise bursts were either presented alone, or paired with a visual stimulus with a visual to auditory onset asynchrony of 120 ms. In a third condition, the visual stimuli were shown alone. All three conditions, auditory alone, visual alone, and paired visual/auditory, were randomly inter-mixed and presented with equal probabilities. Subjects were instructed to fixate on a point in front of them without task instructions concerning either the auditory or visual stimuli. ERPs were recorded from 28 scalp sites throughout every experimental session. Compared to ERPs in the auditory alone condition, pairing the auditory noise bursts with the visual stimulus reduced the amplitude of the auditory N100 component at Cz by 40% and the auditory P200/P300 component at Cz by 25%. No significant topographical change was observed in the scalp distributions of the N100 and P200/P300. Our results suggest that involuntary attention to visual stimuli suppresses early sensory (N100) as well as late cognitive (P200/P300) processing of sudden auditory events. The activation of the exogenous attention system by sudden auditory onset can be modified by involuntary visual attention in a cross-model, passive prepulse inhibition paradigm.

Possible confounding effects of strobe “clicks” on flash evoked potentials in rats

Flash evoked potentials (FEPs) undergo within-and between-session changes and are modified by auditory white noise (26). We examined whether an auditory potential produced by the “click” associated with the strobe discharge could be recorded, and if alterations in an auditory response could explain the within- and between-session changes in FEPs. We also examined differences between a frontal cortex or a nasal reference electrode location on FEPs and auditory potentials. An auditory potential associated with the strobe discharge could be clearly recorded. This response was eliminated by the presence of 80 dB SPL masking white noise. However, the within- and between-session changes in FEPs could not be explained by modifications of the auditory potential. Animals whose ear drums were ruptured did not exhibit an auditory response, and their FEPs were similar to those of controls tested in the presence of masking white noise. A nasal reference electrode decreased the impact of auditory potentials on FEPs, but may allow visual potentials (electroretinogram and optic tract activity) to influence FEPs. The data show that auditory potentials associated with the strobe discharge can be recorded from the visual cortex of rats, and that these auditory responses represent a possible confounding factor in the interpretation of toxicological studies employing FEPs.

Reflex responses to periodontal and auditory stimulation in human masseter

An investigation was made of the reflex responses evoked in the human masseter by periodontal mechanoreceptors. Weak taps were applied to the labial surface of a central incisor tooth by an electromechanical stimulator with a flexible probe (von Frey hair). Forces as low as 0.2 N evoked inhibitory reflex responses in the surface electromyograms of both masseter muscles. These reflexes were modulated to markedly different extents in different subjects by auditory white noise, which always reduced the amplitude of the inhibition. The reflexes were abolished when local anaesthesia was infiltrated around the stimulated tooth and white noise was played into the ears. Evidence is presented that the sound of the tap on the tooth, transmitted through the air, is in itself sufficient to evoke an inhibitory reflex in masseter which is qualitatively similar to that from the periodontal receptors. Thus, in the absence of auditory masking, the total reflex evoked by tooth taps is the result of the summation of the inputs from both periodontal mechanoreceptors and auditory receptors.

Within-session changes in peak N160 amplitude of flash evoked potentials in rats

The negative peak occurring approximately 160 ms after stimulation (peak N160) of flash evoked potentials (FEPs) of rats changes with repeated testing. Habituation, sensitization, and arousal have all been invoked to explain these changes, but few studies have directly tested these explanations. We examined within-session changes in peak N160 amplitude with repeated testing, and the modulatory effects of stimulus intensity and auditory white noise. Peak N160 amplitude increased with daily testing (between-session changes), and was larger at greater stimulus intensities. In contrast, peak N160 amplitude underwent within-session increases on early days and within-session decreases on later days. The within-session changes were not affected by stimulus intensity. In rats previously tested in a quiet environment, exposure to acoustic white noise increased motor activity and transiently decreased peak N160 amplitude, which then increased and subsequently decreased with continued photic and acoustic stimulation. Repeated testing in the presence of noise did not alter the within-session changes in peak N160 amplitude. Heart rate showed both within- and between-session decreases, but was unaffected by noise. The data suggest that the within-session changes in peak N160 amplitude may reflect a habituation-like response to the test environment.

前歯へのタッピング刺激により誘発された咬筋の抑制反射

An investigation was made of the reflex responses evoked in the human masseter by periodontal mechanoreceptors. Weak taps were applied to the labial surface of a central incisor tooth by an electromechanical stimulator with a flexible probe. Forces as low as 0.2N evoked inhibitory reflex responses in the surface electromyograms of both masseter muscles. These reflexes were modulated to markedly different extents in different subjects by auditory white noise, which always reduced the amplitude of the inhibition. The periodontal origin of the reflexes was confirmed by the abolition of the reflexes when local anaesthesia was infiltrated around the stimulated tooth, and white noise was played into the ears. Our evidence suggests that the auditory modulation of the inhibitory responses was due to bony conduction of a shock wave and also due to the sound of the tap entering the ear.

Auditory fatigue and white noise; an attempt at working out a predictive test.

Auditory fatigue and white noise; an attempt at working out a predictive test.