Stimulation Of Auditory Cortex Research Articles

Motor, somatosensory, and executive cortical areas elicit monosynaptic and polysynaptic neuronal activity in the auditory midbrain

We recently reported that the central nucleus of the inferior colliculus (the auditory midbrain) is innervated by glutamatergic pyramidal cells originating not only in auditory cortex (AC), but also in multiple ‘non-auditory’ regions of the cerebral cortex. Here, in anaesthetised rats, we used optogenetics and electrical stimulation, combined with recording in the inferior colliculus to determine the functional influence of these descending connections. Specifically, we determined the extent of monosynaptic excitation and the influence of these descending connections on spontaneous activity in the inferior colliculus.A retrograde virus encoding both green fluorescent protein (GFP) and channelrhodopsin (ChR2) injected into the central nucleus of the inferior colliculus (ICc) resulted in GFP expression in discrete groups of cells in multiple areas of the cerebral cortex. Light stimulation of AC and primary motor cortex (M1) caused local activation of cortical neurones and increased the firing rate of neurones in ICc indicating a direct excitatory input from AC and M1 to ICc with a restricted distribution. In naïve animals, electrical stimulation at multiple different sites within M1, secondary motor, somatosensory, and prefrontal cortices increased firing rate in ICc. However, it was notable that stimulation at some adjacent sites failed to influence firing at the recording site in ICc. Responses in ICc comprised singular spikes of constant shape and size which occurred with a short, and fixed latency (∼ 5 ms) consistent with monosynaptic excitation of individual ICc units. Increasing the stimulus current decreased the latency of these spikes, suggesting more rapid depolarization of cortical neurones, and increased the number of (usually adjacent) channels on which a monosynaptic spike was seen, suggesting recruitment of increasing numbers of cortical neurons. Electrical stimulation of cortical regions also evoked longer latency, longer duration increases in firing activity, comprising multiple units with spikes occurring with significant temporal jitter, consistent with polysynaptic excitation. Increasing the stimulus current increased the number of spikes in these polysynaptic responses and increased the number of channels on which the responses were observed, although the magnitude of the responses always diminished away from the most activated channels. Together our findings indicate descending connections from motor, somatosensory and executive cortical regions directly activate small numbers of ICc neurones and that this in turn leads to extensive polysynaptic activation of local circuits within the ICc.

Neural response properties predict perceived contents and locations elicited by intracranial electrical stimulation of human auditory cortex.

Intracranial electrical stimulation (iES) of auditory cortex can elicit sound experiences with a variety of perceived contents (hallucination or illusion) and locations (contralateral or bilateral side), independent of actual acoustic inputs. However, the neural mechanisms underlying this elicitation heterogeneity remain undiscovered. Here, we collected subjective reports following iES at 3062 intracranial sites in 28 patients (both sexes) and identified 113 auditory cortical sites with iES-elicited sound experiences. We then decomposed the sound-induced intracranial electroencephalogram (iEEG) signals recorded from all 113 sites into time-frequency features. We found that the iES-elicited perceived contents can be predicted by the early high-γ features extracted from sound-induced iEEG. In contrast, the perceived locations elicited by stimulating hallucination sites and illusion sites are determined by the late high-γ and long-lasting α features, respectively. Our study unveils the crucial neural signatures of iES-elicited sound experiences in human and presents a new strategy to hearing restoration for individuals suffering from deafness.

Evoked Potentials by Tone Burst on the Auditory Cortices in Cats -Comparison of Off Responses in Awake and Anesthetized Conditions.

Auditory Brainstem Response (ABR) recording in awake is essential to detect off-responses. This study clarified whether after-termination responses on ABR were offset responses, off-responses or a mixture of the two. Evoked potentials in the auditory cortex of cats in response to tone burst stimuli were recorded, and off responses were examined with chronically implanted electrodes. When the fall time at the end of sound stimuli was 5ms or longer, the amplitude of click responses was extremely small. Under this condition, evoked potentials in response to two types of tone bursts (long and short) were recorded.By calculating the differences in evoked potentials between the two-tone bursts, off responses were separated. Off responses were generated during wakefulness by auditory cortex stimulation but were not observed under anesthesia. Pronounced off responses, which were middle latency responses exhibiting bis positive waves, were obtained in response to sound stimuli with a frequency of 2 kHz or higher. Vertex stimulation did not induce off responses either during wakefulness or under anesthesia. Off responses are derived from synchronous responses of neurons in the auditory cortex, which are generated when the neurons detect attenuation in the stimulus strength at the end of tone burst stimuli.

Decreased BOLD signals elicited by 40-Hz auditory stimulation of the right primary auditory cortex in bipolar disorder: An fMRI study.

BackgroundA number studies have been conducted on abnormalities in the cortical circuitry of gamma oscillations, including deficit in auditory steady-state response (ASSR) to gamma-frequency (≧ 30-Hz) stimulation, in patients with bipolar disorder (BD). In the current study, we investigated neural responses during click stimulation by blood oxygen level-dependent (BOLD) signals. We focused on Broadman 41 and 42, the main sources of ASSR.Materials and methodsWe acquired BOLD responses elicited by click trains of 80-, 40-, 30- and 20-Hz frequencies from 25 patients with BD to 27 healthy controls (HC) with normal hearing between 22 and 59 years of age assessed via a standard general linear-model-based analysis. We extracted contrast values by identifying the primary auditory cortex and Brodmann areas 41 and 42 as regions of interest (ROI)s.ResultsBD group showed significantly decreased ASSR-BOLD signals in response to 40-Hz stimuli compared to the HC group in the right Brodmann areas 41 and 42. We found significant negative correlations between the BOLD change in the right Brodmann areas 41 and 42 and Structured Interview Guide for the Hamilton Depression Rating Scale (SIGH-D) scores, also the BOLD change in the right Brodmann areas 41 and 42 and the Positive and Negative Syndrome Scale (PANSS)-Negative scores.ConclusionThe observed decrease in BOLD signal patterns in the right primary auditory cortex during 40-Hz ASSR may be a potential biomarker option for bipolar disorder.

Static magnetic stimulation of human auditory cortex: a feasibility study.

There is a growing interest about the effects of static transcranial magnetic stimulation (tSMS) over different cortical areas, being the motor cortex the most widely studied region. Previous experiments have shown that noninvasive magnetic static stimulation of the human brain may change its excitability in a reversible way for a period that outlasts the time of application of the magnetic field. However, evidence about the effects over the auditory cortex are poor and this is the purpose of the present study. Twelve voluntary subjects were studied in two different sessions, immediately before and 20 min after the placement of a magnet or a sham over the left primary auditory cortex, for 30 min. No significant effects of the magnet were observed on auditory responses, including onset and offset potentials and oscillatory responses to stimulus frequency modulation. A reduction in the amplitude of the cortical onset and offset potentials was observed after the two sessions, both with the magnet and with the false magnet (sham). No effects of unilateral static magnetic stimulation on cortical auditory responses have been observed. However, we probe the feasibility and tolerability of the protocol performed and suggest the use of different stimulation protocols.

Common fronto-temporal effective connectivity in humans and monkeys

SummaryHuman brain pathways supporting language and declarative memory are thought to have differentiated substantially during evolution. However, cross-species comparisons are missing on site-specific effective connectivity between regions important for cognition. We harnessed functional imaging to visualize the effects of direct electrical brain stimulation in macaque monkeys and human neurosurgery patients. We discovered comparable effective connectivity between caudal auditory cortex and both ventro-lateral prefrontal cortex (VLPFC, including area 44) and parahippocampal cortex in both species. Human-specific differences were clearest in the form of stronger hemispheric lateralization effects. In humans, electrical tractography revealed remarkably rapid evoked potentials in VLPFC following auditory cortex stimulation and speech sounds drove VLPFC, consistent with prior evidence in monkeys of direct auditory cortex projections to homologous vocalization-responsive regions. The results identify a common effective connectivity signature in human and nonhuman primates, which from auditory cortex appears equally direct to VLPFC and indirect to the hippocampus.Video

Transcranial Static Magnetic Field Stimulation Over the Temporal Cortex Modulating the Right Ear Advantage in Dichotic Listening

Transcranial static magnetic field stimulation (tSMS) has proposed a new, promising, and simple non-invasive brain stimulation method. While several studies gained certain evidence about tSMS effects in the motor, somatosensory, and visual domains, there is still a controversial debate about its general effectiveness. In the present study, we investigated potential tSMS effects on auditory speech processing as measured by a dichotic listening (DL) task. Fifteen healthy participants received in randomized order on three different days one session of either sham, tSMS over the left, or tSMS over the right auditory cortex (AC). Under stimulation, participants performed a standard DL task with consonant-vowel syllables. Simultaneously, we recorded electroencephalogram from central sites (Fz, Cz, Pz). TSMS over the left AC changed the behavioral performance and modulated auditory evoked potentials. Stimulation of the left AC significantly reduced the right ear advantage during the DL task and the N1 component of auditory evoked potentials in response to these syllables. The preliminary results of the present exploratory study demonstrate the ability of tSMS to modulate human brain activity on a behavioral as well as physiologic level. Furthermore, tSMS effects on acoustic processing may have clinical implications by fostering potential approaches for a treatment of speech-related pathologies associated with hyperexcitability in the AC.

Auditory cortex shapes sound responses in the inferior colliculus.

The extensive feedback from the auditory cortex (AC) to the inferior colliculus (IC) supports critical aspects of auditory behavior but has not been extensively characterized. Previous studies demonstrated that activity in IC is altered by focal electrical stimulation and pharmacological inactivation of AC, but these methods lack the ability to selectively manipulate projection neurons. We measured the effects of selective optogenetic modulation of cortico-collicular feedback projections on IC sound responses in mice. Activation of feedback increased spontaneous activity and decreased stimulus selectivity in IC, whereas suppression had no effect. To further understand how microcircuits in AC may control collicular activity, we optogenetically modulated the activity of different cortical neuronal subtypes, specifically parvalbumin-positive (PV) and somatostatin-positive (SST) inhibitory interneurons. We found that modulating the activity of either type of interneuron did not affect IC sound-evoked activity. Combined, our results identify that activation of excitatory projections, but not inhibition-driven changes in cortical activity, affects collicular sound responses.

Phantom Perception of Sound and the Abnormal Cortical Inhibition System: An Electroencephalography (EEG) Study.

Despite no observable external sound present, a perceived feeling of a recurrent unpleasant sound is a main complaint in the patients with chronic tinnitus. This phantom perception of sound is considered as the auditory equivalent of phantom limb pain, and altered excitability may be involved in its underlying pathology. Tinnitus-related hyper-excitation is suppressed by inhibitory repetitive transcranial magnetic stimulation (rTMS). However, the neural mechanism underlying the treatment is not fully understood, and quantifying the suppression induced by rTMS has yet to be considered. We evaluated the effect of rTMS on the cortical inhibition status following single-site stimulation over the auditory temporal cortex (T group) or dual-site stimulation over the auditory temporal and the frontal regions (TF group). These effects were also compared with outcomes following sham stimulation (S group). Subjective response was recorded using tinnitus-related handicap index (THI), and changes in the cortical inhibition status were assessed using an auditory paired-pulse suppression index (PPSI). TF group showed the greatest benefit from the treatment evidenced in the reduced PPSI and THI scores. T and S groups did not benefit much. TF group overlapped mostly with the responder group, indicating improvement in both subjective THI and objective PPSI measurements. Our results suggest that rTMS is a beneficial therapeutic treatment for chronic tinnitus patients and the dual-site treatment was the most effective in terms of both tinnitus complaint and quantitative indices. Thus, subjective reports and electrophysiological signatures may be complementary for the diagnosis/prognosis of tinnitus.

Reversible Functional Changes Evoked by Anodal Epidural Direct Current Electrical Stimulation of the Rat Auditory Cortex.

Rat auditory cortex was subjected to 0.1 mA anodal direct current in seven 10-min sessions on alternate days. Based on the well-known auditory cortex control of olivocochlear regulation through corticofugal projections, auditory brainstem responses (ABRs) were recorded as an indirect test of the effectiveness and reversibility of the multisession protocol of epidural stimulation. Increases of 20–30 dB ABR auditory thresholds shown after epidural stimulation reverted back to control levels 10 min after a single session. However, increases in thresholds revert 4 days after multisession stimulation. Less changes in wave amplitudes and threshold shifts were shown in ABR recorded contralaterally to the electrically stimulated side of the brain. To assess tissue effects of epidural electric stimulation on the brain cortex, well characterized functional anatomical markers of glial cells (GFAP/astrocytes and Iba1/microglial cells) and neurons (c-Fos) were analyzed in alternate serial sections by quantitative immunocytochemistry. Restricted astroglial and microglial reactivity was observed within the cytoarchitectural limits of the auditory cortex. However, interstitial GFAP overstaining was also observed in the ventricular surface and around blood vessels, thus supporting a potential global electrolytic stimulation of the brain. These results correlate with extensive changes in the distribution of c-Fos immunoreactive neurons among layers along sensory cortices after multisession stimulation. Quantitative immunocytochemical analysis supported this idea by showing a significant increase in the number of positive neurons in supragranular layers and a decrease in layer 6 with no quantitative changes detected in layer 5. Our data indicate that epidural stimulation of the auditory cortex induces a reversible decrease in hearing sensitivity due to local, restricted epidural stimulation. A global plastic response of the sensory cortices, also reported here, may be related to electrolytic effects of electric currents.

Selective Neuronal Activation by Cochlear Implant Stimulation in Auditory Cortex of Awake Primate.

The cochlear implant (CI) is the most successful neural prosthetic device to date and has restored hearing in hundreds of thousands of deaf individuals worldwide. However, despite its huge successes, CI users still face many perceptual limitations, and the brain mechanisms involved in hearing through CI devices remain poorly understood. By directly comparing single-neuron responses to acoustic and CI stimulation in auditory cortex of awake marmoset monkeys, we discovered that neurons unresponsive to CI stimulation were sharply tuned to frequency and sound level. Our results point out a major deficit in central auditory processing of CI stimulation and provide important insights into mechanisms underlying the poor CI user performance in a wide range of perceptual tasks.

Effects of an NMDA antagonist on the auditory mismatch negativity response to transcranial direct current stimulation.

Transcranial direct current stimulation (tDCS) is a non-invasive form of brain stimulation which uses a weak constant current to alter cortical excitability and activity temporarily. tDCS-induced increases in neuronal excitability and performance improvements have been observed following anodal stimulation of brain regions associated with visual and motor functions, but relatively little research has been conducted with respect to auditory processing. Recently, pilot study results indicate that anodal tDCS can increase auditory deviance detection, whereas cathodal tDCS decreases auditory processing, as measured by a brain-based event-related potential (ERP), mismatch negativity (MMN). As evidence has shown that tDCS lasting effects may be dependent on N-methyl-D-aspartate (NMDA) receptor activity, the current study investigated the use of dextromethorphan (DMO), an NMDA antagonist, to assess possible modulation of tDCS's effects on both MMN and working memory performance. The study, conducted in 12 healthy volunteers, involved four laboratory test sessions within a randomised, placebo and sham-controlled crossover design that compared pre- and post-anodal tDCS over the auditory cortex (2 mA for 20 minutes to excite cortical activity temporarily and locally) and sham stimulation (i.e. device is turned off) during both DMO (50 mL) and placebo administration. Anodal tDCS increased MMN amplitudes with placebo administration. Significant increases were not seen with sham stimulation or with anodal stimulation during DMO administration. With sham stimulation (i.e. no stimulation), DMO decreased MMN amplitudes. Findings from this study contribute to the understanding of underlying neurobiological mechanisms mediating tDCS sensory and memory improvements.

Repetitive transcranial magnetic stimulation induces oscillatory power changes in chronic tinnitus.

Chronic tinnitus is associated with neuroplastic changes in auditory and non-auditory cortical areas. About 10 years ago, repetitive transcranial magnetic stimulation (rTMS) of auditory and prefrontal cortex was introduced as potential treatment for tinnitus. The resulting changes in tinnitus loudness are interpreted in the context of rTMS induced activity changes (neuroplasticity). Here, we investigate the effect of single rTMS sessions on oscillatory power to probe the capacity of rTMS to interfere with tinnitus-specific cortical plasticity. We measured 20 patients with bilateral chronic tinnitus and 20 healthy controls comparable for age, sex, handedness, and hearing level with a 63-channel electroencephalography (EEG) system. Educational level, intelligence, depressivity and hyperacusis were controlled for by analysis of covariance. Different rTMS protocols were tested: Left and right temporal and left and right prefrontal cortices were each stimulated with 200 pulses at 1 Hz and with an intensity of 60% stimulator output. Stimulation of central parietal cortex with 6-fold reduced intensity (inverted passive-cooled coil) served as sham condition. Before and after each rTMS protocol 5 min of resting state EEG were recorded. The order of rTMS protocols was randomized over two sessions with 1 week interval in between. Analyses on electrode level showed that people with and without tinnitus differed in their response to left temporal and right frontal stimulation. In tinnitus patients left temporal rTMS decreased frontal theta and delta and increased beta2 power, whereas right frontal rTMS decreased right temporal beta3 and gamma power. No changes or increases were observed in the control group. Only non-systematic changes in tinnitus loudness were induced by single sessions of rTMS. This is the first study to show tinnitus-related alterations of neuroplasticity that were specific to stimulation site and oscillatory frequency. The observed effects can be interpreted within the thalamocortical dysrhythmia model assuming that slow waves represent processes of deafferentiation and that high frequencies might be indicators for tinnitus loudness. Moreover our findings confirm the role of the left temporal and the right frontal areas as relevant hubs in tinnitus related neuronal network. Our results underscore the value of combined TMS-EEG measurements for investigating disease related changes in neuroplasticity.

Impact of uncertain head tissue conductivity in the optimization of transcranial direct current stimulation for an auditory target

Objective. Transcranial direct current stimulation (tDCS) is a non-invasive brain stimulation technique to modify neural excitability. Using multi-array tDCS, we investigate the influence of inter-individually varying head tissue conductivity profiles on optimal electrode configurations for an auditory cortex stimulation. Approach. In order to quantify the uncertainty of the optimal electrode configurations, multi-variate generalized polynomial chaos expansions of the model solutions are used based on uncertain conductivity profiles of the compartments skin, skull, gray matter, and white matter. Stochastic measures, probability density functions, and sensitivity of the quantities of interest are investigated for each electrode and the current density at the target with the resulting stimulation protocols visualized on the head surface. Main results. We demonstrate that the optimized stimulation protocols are only comprised of a few active electrodes, with tolerable deviations in the stimulation amplitude of the anode. However, large deviations in the order of the uncertainty in the conductivity profiles could be noted in the stimulation protocol of the compensating cathodes. Regarding these main stimulation electrodes, the stimulation protocol was most sensitive to uncertainty in skull conductivity. Finally, the probability that the current density amplitude in the auditory cortex target region is supra-threshold was below 50%. Significance. The results suggest that an uncertain conductivity profile in computational models of tDCS can have a substantial influence on the prediction of optimal stimulation protocols for stimulation of the auditory cortex. The investigations carried out in this study present a possibility to predict the probability of providing a therapeutic effect with an optimized electrode system for future auditory clinical and experimental procedures of tDCS applications.

V35. rTMS induced oscillatory power as neuroplastic marker in chronic tinnitus

Background Chronic tinnitus is associated with neuroplastic changes such as changes in spontaneous activity along the auditory pathway, tonotopic reorganization of the auditory cortex, increased activity and connectivity in specific cortical networks. Ten years ago, daily repetitive transcranial magnetic stimulation (rTMS) of auditory and prefrontal cortex was introduced as potential treatment. Here, we investigated the effect of sham-controlled single rTMS sessions on oscillatory power as elicited with electroencephalography (EEG) to probe the capacity of rTMS to interfere with tinnitus-specific cortical activity. Methods We measured 20 patients with bilateral chronic tinnitus and 20 healthy controls which were comparable for age, sex, handedness, hearing level with a 63-channel EEG system wearing earplugs. Educational level, intelligence, depressivity, hyperacusis were controlled by analysis of covariance. Left and right temporal and left and right prefrontal cortex was stimulated with 200 pulses at 1 Hz and with an intensity of 60% stimulator output. Stimulation of central parietal cortex with lower intensity (6-fold reduced intensity, not targeting the cortex) served as sham condition. Before and after each session five minutes of resting state EEG were sampled. Stimulation sessions were randomized over two sessions with one week interval in between. Results Sensor-based analyses showed that left temporal stimulation induced shamcontrolled, baseline-corrected (post minus pre measurement) tinnitus-related decreases in frontal theta and delta power and increases in frontal beta2 power. Right frontal stimulation showed decreases in the oscillatory power of the right temporal beta3 and gamma band. Discussion Short sessions of low-frequency rTMS were capable to show neuroplastic effects specific for stimulation site and frequency band at specific recording sites. Mechanism of action might be based on long-range connectivity. These findings show the feasibility of combined TMS-EEG to probe neuroplastic alterations specific for tinnitus.

Pairing broadband noise with cortical stimulation induces extensive suppression of ascending sensory activity

Objective. The corticofugal system can alter coding along the ascending sensory pathway. Within the auditory system, electrical stimulation of the auditory cortex (AC) paired with a pure tone can cause egocentric shifts in the tuning of auditory neurons, making them more sensitive to the pure tone frequency. Since tinnitus has been linked with hyperactivity across auditory neurons, we sought to develop a new neuromodulation approach that could suppress a wide range of neurons rather than enhance specific frequency-tuned neurons. Approach. We performed experiments in the guinea pig to assess the effects of cortical stimulation paired with broadband noise (PN-Stim) on ascending auditory activity within the central nucleus of the inferior colliculus (CNIC), a widely studied region for AC stimulation paradigms. Main results. All eight stimulated AC subregions induced extensive suppression of activity across the CNIC that was not possible with noise stimulation alone. This suppression built up over time and remained after the PN-Stim paradigm. Significance. We propose that the corticofugal system is designed to decrease the brain’s input gain to irrelevant stimuli and PN-Stim is able to artificially amplify this effect to suppress neural firing across the auditory system. The PN-Stim concept may have potential for treating tinnitus and other neurological disorders.

Targeting the parahippocampal area by auditory cortex stimulation in tinnitus.

The final common pathway in tinnitus generation is considered to be synchronized auditory oscillatory hyperactivity. Intracranial auditory cortex stimulation (iACS) via implanted electrodes has been developed to treat severe cases of intractable tinnitus targeting this final common pathway, in the hope of being a panacea for tinnitus. However, not everybody responds to this treatment. The electrical brain activity and functional connectivity at rest might determine who is going to respond or not to iACS and might shed light on the pathophysiology of auditory phantom sound generation. The resting state electrical brain activity of 5 patients who responded and 5 patients who did not respond to auditory cortex implantation are compared using source localized spectral activity (Z-score of log transformed current density) and lagged phase synchronization. sLORETA source localization reveals significant differences between responders vs non-responders for beta3 in left posterior parahippocampal, hippocampal and amygdala area extending into left insula. Gamma band differences exist in the posterior parahippocampal areas and BA10. Functional connectivity between the auditory cortex and the hippocampal area is increased for beta2, delta and theta2 in responders, as well as between the parahippocampal area and auditory cortex for beta3. The resting state functional connectivity and activity between the auditory cortex and parahippocampus might determine whether a tinnitus patient will respond to a cortical implant. The auditory cortex may only be a functional entrance into a larger parahippocampal based tinnitus network.

Pathways

Pathways

Tonotopic and localized pathways from primary auditory cortex to the central nucleus of the inferior colliculus

Descending projections from the cortex to subcortical structures are critical for auditory plasticity, including the ability for central neurons to adjust their frequency tuning to relevant and meaningful stimuli. We show that focal electrical stimulation of primary auditory cortex in guinea pigs produces excitatory responses in the central nucleus of the inferior colliculus (CNIC) with two tonotopic patterns: a narrow tuned pattern that is consistent with previous findings showing direct frequency-aligned projections; and a broad tuned pattern in which the auditory cortex can influence multiple frequency regions. Moreover, excitatory responses could be elicited in the caudomedial portion along the isofrequency laminae of the CNIC but not in the rostrolateral portion. This descending organization may underlie or contribute to the ability of the auditory cortex to induce changes in frequency tuning of subcortical neurons as shown extensively in previous studies.

Electroencephalographic Changes Following Direct Current Deep Brain Stimulation of Auditory Cortex

Although deep brain (DBS) and transcranial direct current stimulation (tDCS) are used as investigative tools and therapies for a variety of neurological and psychiatric conditions, their mechanisms of action remain poorly understood. Therefore, there is a need for new animal models of neuromodulation. To introduce and validate a direct current DBS (DC-DBS) model that will use the anatomic precision of intracranial electrodes, as used in DBS, to apply direct current, as used in tDCS, over primary auditory cortex (A1) and induce electroencephalographic (EEG) changes. Twenty-four mice were assigned to 1 of 2 stimulation groups or a sham group and were implanted with electrodes in A1. Stimulation groups underwent DC-DBS stimulation for 20 minutes at 20 μA. Auditory EEG was recorded before stimulation and at 1 hour, 1 week, and 2 weeks poststimulation. EEG was analyzed for changes in N1 (N100 in humans, N40 in mice) amplitude and latency as well as delta and theta power. DC-DBS led to significant EEG changes (all P values < .05). Among the stimulated animals, there were durable reductions in delta and theta power. There were no differences within the sham group, and neither N40 latencies nor amplitudes changed across time. Our results show DC-DBS-induced reductions in slow-wave activity consistent with recent tDCS studies. We propose that this model will provide a means to explore basic mechanisms of neuromodulation and could facilitate future application of DC-DBS in humans.