This research was supported by grants from the Research Foundation - Flanders (FWO, project Nr G.0420.02 and G.0443.11N), the Hercules Foundation (grant Nr AUHA0012), Concerted Research Actions (GOA funding) from the University of Antwerp, and partly sponsored by EC - FP6 project DiMI, LSHB-CT-2005-512146 and EC - FP6 project EMIL LSHC-CT-2004-503569 to A.VdL. G.DG and C.P. are Postdoctoral Fellows of the Research Foundation - Flanders (FWO).

1. Preparation of the Auditory Stimuli
<ol>
	<li>First record the sound-stimuli while being played inside the bore of the 7T MR system. The bore is a confined space that can distort the auditory stimuli resulting in enhancement of certain auditory frequencies. Figure 1 shows the frequencies enhanced and suppressed as shown by our recordings of white noise made at the location of the bird's head within the magnet bore using a fiber-optic microphone (Optimic 1160, Optoacoustics). To compensate this artificial enhancement, an equalizer function is applied to each stimulus using WaveLab software. For our particular setup, the function consists of a Gaussian kernel with the following parameters: maximum amplitude: -20dB, centered on 3,750 Hz, width: 0.05 octaves (corresponding to the range 2,500-5,000 Hz for our system).</li>
	<li>The song stimuli are composed of several individual song motifs of each bird interleaved with periods of silence. The duration of these silent periods is adjusted to keep the total amount of sound and silence identical over all stimuli. This construction conserves the natural intra-individual and inter-individual variability of song length. The total length of each stimulus is 16 sec. The intensity of each song is normalized in terms of matched root-mean-square and high-pass filtered at 400 Hz before being integrated into the complete stimulus (song and silent periods). These manipulations are done using Praat software.</li>
	<li>The experiment consists of an ON/OFF block design alternating auditory stimulation periods (ON blocks) with resting periods (OFF blocks) (Figure 2). Each block (ON and OFF) lasts 16 sec, which corresponds to the acquisition time of 2 images (see below for acquisition). Each stimulus type is presented 25 times, resulting in the acquisition of 50 images per stimulus and per subject. The presentation order of the conditions should be randomized within and between subjects. This randomized order of the stimuli can be coded into Presentation software.</li>
</ol>
2. Subject Preparation
2.1 Subject and group size
Here we present a protocol specifically adapted to the use of (adult) zebra finches. The choice of the species depends on the scientific question. However, other considerations like bird robustness to anaesthesia may also be taken into account. Zebra finches (Taeniopygia guttata) should be housed in aviaries under a 12 hr light: 12 hr dark photoperiod and have access to food and water ad libitum throughout the study. The minimal number of individuals per experiment is 15. This number takes into account the sensitivity of spin-echo fMRI and the natural inter-individual variability of biological phenomena measured in the experiment.
2.2 Installation of setup and preparation of the animal
(For specification of the used equipment, we refer to the list of specific reagents and equipment at the end of this article)
<ol>
	<li>Install the beak mask on the MRI bed of a 7T MR system and connect it to the gas controller device with plastic tubes. Open both oxygen and nitrogen gas bottles and switch on the gas controller device (flow rate oxygen: 200 cc/min; nitrogen: 400 cc/min).</li>
</ol>
As mentioned above, a 7T MR system is used in the presented setup. Other MR systems with different field strengths are also possible, but at 7T a good compromise is reached between signal-to-noise ratio and degree of susceptibility artifacts (see discussion). At higher field strengths the signal-to-noise ratio will increase together with the degree of susceptibility artifacts.
<ol start="2">
	<li>Switch on the feedback controlled system and warm airflow device.</li>
	<li>Anaesthetize the zebra finch with 3% isoflurane in a mixture of oxygen and nitrogen by introducing its beak into the mask and holding the head down until the bird is fully anesthetised. This can be verified by pulling the foot softly: when the bird is fully sedated the foot will not be retracted by the bird. In addition, the eyes of the bird will be partly closed.</li>
	<li>Introduce the cloacal temperature probe to screen the body temperature and monitor the breathing rate by placing a pneumatic sensor underneath the zebra finch belly. Close the jacket to restrain the body of the bird (Figure 3).</li>
	<li>Maintain breathing rate within the range of 40 - 100 breaths per minute and keep body temperature constant within a narrow range of 40 &plusmn; 0.5 &deg;C. When the breathing range is too low/high, adjust the level of anaesthesia (% isoflurane) accordingly. When the problem persists, the experiment should be stopped and the animal removed from the setup in order to recover.</li>
	<li>Position the non-magnetic dynamic speakers on either side of the zebra finch head and connect them to the amplifier. Make sure that the wires of the speakers are led away from the temperature probe, because it can influence the temperature reading when too close.</li>
	<li>Place the surface RF coil on top of the zebra finch head and position the zebra finch in the center of the magnet (and automatically the center of the transmit coil which is situated in the middle of the magnet).</li>
	<li>Reduce the anaesthesia level to 1.5% isoflurane mixed with oxygen and nitrogen.</li>
</ol>
3. Data Acquisition
<ol>
	<li>Acquire a set of 1 sagittal, 1 horizontal and 1 coronal gradient-echo (GE) scout image (tri-pilot sequence) and sets of horizontal, coronal and sagittal multi-slice images (piloting T2-weighted rapid acquisition relaxation-enhanced (RARE) SE sequence) to determine the position of the brain in the magnet (Figure 4).</li>
	<li>Decrease the noise of the gradients by increasing their ramp times to 1,000 &mu;s.</li>
	<li>Prepare the fMRI sequence: RARE T2-weighted sequence, effective TE: 60 msec, TR: 2,000 msec, RARE factor: 8, FOV: 16 mm, matrix size: 64 x 32, orientation: sagittal, slice thickness: 0.75 mm, Inter-slice gap thickness: 0.05 mm, 15 slices covering nearly the whole brain (Figure 4).</li>
	<li>Select the auditory protocol (auditory stimuli and timing of stimulus delivery) in the presentation software. This protocol consists of a sequence of commands - for the initiation of specific auditory stimuli - which are executed at a specific scan-number. At every repetition within the fMRI sequence, the scanner software will send a trigger to the auditory presentation software which in turn registers the scan number and executes the corresponding command.</li>
	<li>To ensure that the auditory presentation software does not miss any trigger from the scanner, the auditory protocol is initiated first. Once the protocol is fully loaded, the fMRI sequence is started.</li>
	<li>Each fMRI experiment is preceded by the acquisition of 12 dummy images to allow the signal attributed to the scanner noise to reach a steady state before starting auditory stimulation.</li>
	<li>After acquisition zero-fill the data to 64 x 64.</li>
	<li>Take a first (preliminary) look at the results using the Functional Tool of Paravision (option Processing/Functional Imaging). Calculate the differential BOLD response between all ON blocks and the baseline (OFF blocks). This analysis gives a first indication of the quality of the experiment. If no activation is seen in the primary auditory areas at this stage, the bird did probably not hear/processed the auditory stimuli due to technical problems with the stimulus presentation, anaesthesia level, etc. The setup should be verified and the measurement repeated.</li>
	<li>Run an anatomical 3D RARE T2-weighted sequence in the same orientation as the previous fMRI scans and with effective TE: 60 msec, TR: 2,000 msec, RARE factor: 8, FOV: 16 mm, matrix size: 256 x 128 x 64.</li>
	<li>Zero-fill the data to 256 x 256 x 256.</li>
	<li>Take the zebra finch from the MRI bed and let it recover from anaesthesia in a cage under a red lamp. Normally, the recovery of a zebra finch after isoflurane anaesthesia goes relatively fast (maximal 5 min). After only a few minutes, the birds will try to stand up and once the bird is fully recovered, it will perch on a branch instead of sitting on the bottom of the cage. The duration of anaesthesia is about 2 hr for the present experiment. The maximum time of isoflurane anaesthesia applied to zebra finches in our lab is 6 hr, after which the birds also recovered within 5 min.</li>
</ol>
4. Data Processing
<ol>
	<li>Convert the MR-data into Analyze or Nifti format.</li>
	<li>Because SPM has been developed to process fMRI data acquired in humans, that is for voxels of around 2 mm. Numerous SPM settings are adapted to this approximate voxel size. If one does not want to change all these settings, the simplest way to proceed is to artificially increase the voxel size of bird fMRI data. Adjust the voxel size in the header by multiplying the real voxel size by 10 using MRIcro. It should be noted, that such adjustment does not influence the data in itself, no resampling or any other modifications to the data is applied.</li>
</ol>
An alternative to this is the use of 'SPMMouse' which is a toolbox allowing SPM to open and analyze files of any voxel dimension. The tool allows SPM 'glass brains' to be created from any image, and automatically adjusts defaults length scales based on the headers of image files or user entered data. Hence, this toolbox works in the opposite way than what we propose. Instead of changing the voxel size of the images to fit in SPM, the default settings of SPM are changed to use images with different voxel sizes.
<ol start="3">
	<li>Realign the fMRI data. Co-register the anatomical 3D dataset to the fMRI time series. Normalize the 3D data (and the co-registered fMRI time series) to the zebra finch brain MRI atlas. Apply the transformation matrix to the fMRI dataset. This can all be done using Statistical Parametric Mapping (SPM) 8 software.</li>
	<li>Smooth the data with a 0.5-mm width Gaussian kernel using SPM8.</li>
	<li>Carry out statistical voxel-based analyses using SPM8. Model the data as a box-car (no hemodynamic response function). Estimate model parameters with the classical Restricted Maximum Likelihood algorithm. Compute the mean effect of each auditory stimulus in each subject (fixed-effect analysis) and then compute statistics as wished for group analyses (mixed-effect analyses).</li>
	<li>Project the statistical parametric map onto the zebra finch atlas (Figure 5) 9 in SPM8 to localize the functional activations (Figure 6).</li>
</ol>

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No conflicts of interest declared.

In this report, we describe an optimized protocol for the detailed in vivo characterization of neural substrates of auditory stimulation in anaesthetized zebra finches.
In line with the presented protocol, the majority of functional brain activation studies in animals using BOLD fMRI, anaesthetize the animals during the acquisition. Training animals to accustom them to the magnet environment and the scanner noise during the study periods is also possible but rather time-consuming and ...

<table><tbody><tr><td>Isoflurane anaesthetic</td><td>Isoflo</td><td>05260-05</td><td></td></tr><tr><td>PC-Sam hardware/software</td><td>SA-Instruments</td><td></td><td>&lt;a href=&quot;http://www.i4sa.com&quot; target=&quot;_blank&quot;&gt;http://www.i4sa.com&lt;/a&gt;</td></tr><tr><td>Monitoring and gating system</td><td></td><td>1025</td><td></td></tr><tr><td>MR-compatible small rodent heater system</td><td></td><td></td><td>Model 1025 compatible</td></tr><tr><td>Rectal temperature probe</td><td></td><td>RTP-102B</td><td>7&#039;&#039;, 0.044&#039;&#039; </td></tr><tr><td>7T MR scanner</td><td>Bruker Biospin</td><td>PHS 70/16</td><td></td></tr><tr><td>Paravision software</td><td></td><td>5.1</td><td></td></tr><tr><td>Gradient Insert</td><td></td><td>BGA9S</td><td>400 mT/m, 300A, 500V</td></tr><tr><td>Gradient Amplifiers</td><td>Copley Co., USA</td><td>C256</td><td></td></tr><tr><td>Transmit resonators</td><td></td><td></td><td>Inner diameter: 72 mm, transmit only, active decoupled</td></tr><tr><td>Receiver antenna - 20 mm quadrature Mouse Head</td><td></td><td></td><td>Receive only, active decoupled</td></tr><tr><td>WaveLab software</td><td>Steinberg</td><td></td><td></td></tr><tr><td>Praat software</td><td>Paul Boersma, University of Amsterdam</td><td></td><td>&lt;a href=&quot;http://www.praat.org&quot; target=&quot;_blank&quot;&gt;http://www.praat.org&lt;/a&gt;</td></tr><tr><td>Non-magnetic dynamic speakers</td><td>Visation, Germany</td><td>HK 150</td><td></td></tr><tr><td>Fiber optic microphone</td><td>Optoacoustics,</td><td>Optimic 1160</td><td></td></tr><tr><td>Sound amplifier</td><td>Phonic corporation</td><td>MM 1002a</td><td></td></tr><tr><td>Presentation software</td><td>Neurobehavioral Systems Inc.</td><td></td><td></td></tr><tr><td>MRIcro</td><td>Chris Rorden</td><td></td><td>&lt;a href=&quot;http://www.cabiatl.com/mricro/mricro/&quot; target=&quot;_blank&quot;&gt;http://www.cabiatl.com/mricro/mricro/&lt;/a&gt;</td></tr><tr><td>Statistical Parametric Mapping (SPM)</td><td>Welcome Trust Centre for Neuroimaging</td><td>8</td><td>&lt;a href=&quot;http://www.fil.ion.ucl.ac.uk/spm/&quot; target=&quot;_blank&quot;&gt;http://www.fil.ion.ucl.ac.uk/spm/&lt;/a&gt;</td></tr></tbody></table>

functional magnetic resonance imaging (fmri) with auditory stimulation in songbirds

The neurobiology of birdsong, as a model for human speech, is a pronounced area of research in behavioral neuroscience. Whereas electrophysiology and molecular approaches allow the investigation of either different stimuli on few neurons, or one stimulus in large parts of the brain, blood oxygenation level dependent (BOLD) functional Magnetic Resonance Imaging (fMRI) allows combining both advantages, i.e. compare the neural activation induced by different stimuli in the entire brain at once. fMRI in songbirds is challenging because of the small size of their brains and because their bones and especially their skull comprise numerous air cavities, inducing important susceptibility artifacts. Gradient-echo (GE) BOLD fMRI has been successfully applied to songbirds 1-5 (for a review, see 6). These studies focused on the primary and secondary auditory brain areas, which are regions free of susceptibility artifacts. However, because processes of interest may occur beyond these regions, whole brain BOLD fMRI is required using an MRI sequence less susceptible to these artifacts. This can be achieved by using spin-echo (SE) BOLD fMRI 7,8 . In this article, we describe how to use this technique in zebra finches (Taeniopygia guttata), which are small songbirds with a bodyweight of 15-25 g extensively studied in behavioral neurosciences of birdsong. The main topic of fMRI studies on songbirds is song perception and song learning. The auditory nature of the stimuli combined with the weak BOLD sensitivity of SE (compared to GE) based fMRI sequences makes the implementation of this technique very challenging.

We here visually presented an optimized sequence of procedures for successful imaging of neural substrates of auditory stimuli in the zebra finch brain. Firstly, the described procedure for preparation of the auditory stimuli results in stimuli that can be incorporated into an ON/OFF block paradigm (Figure 2) and that are normalized to eliminate potential differences in sound pressure level that could evoke a differential response in the brain. After preparing the zebra finch for MRI scanning and ...

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Functional Magnetic Resonance Imaging fMRI with Auditory Stimulation in Songbirds

This article shows an optimized procedure for imaging of the neural substrates of auditory stimulation in the songbird brain using functional Magnetic Resonance Imaging (fMRI). It describes the preparation of the sound stimuli, the positioning of the subject and the acquisition and subsequent analysis of the fMRI data.

Functional Magnetic Resonance Imaging (fMRI) with Auditory Stimulation in Songbirds

The neurobiology of birdsong, as a model for human speech, is a pronounced area of research in behavioral neuroscience. Whereas electrophysiology and ...

functional-magnetic-resonance-imaging-fmri-with-auditory-stimulation

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18.1K Views.  University of Antwerp. This article shows an optimized procedure for imaging of the neural substrates of auditory stimulation in the songbird brain using functional Magnetic Resonance Imaging (fMRI). It describes the preparation of the sound stimuli, the positioning of the subject and the acquisition and subsequent analysis of the fMRI data.

Video: Functional Magnetic Resonance Imaging fMRI with Auditory Stimulation in Songbirds

Stimulating the Lip Motor Cortex with Transcranial Magnetic Stimulation

Transcranial magnetic stimulation (TMS) has proven to be a useful tool in investigating the role of the articulatory motor cortex in speech perception. Researchers have used single-pulse and repetitive TMS to stimulate the lip representation in the motor cortex. The excitability of the lip motor representation can be investigated by applying single TMS pulses over this cortical area and recording TMS-induced motor evoked potentials (MEPs) via electrodes attached to the lip muscles (electromyography; EMG). Larger MEPs reflect increased cortical excitability. Studies have shown that excitability increases during listening to speech as well as during&#160;viewing speech-related movements. TMS can be used also to disrupt the lip motor representation. A 15-min train of low-frequency sub-threshold repetitive stimulation has been shown to suppress motor excitability for a further 15-20 min. This TMS-induced disruption of the motor lip representation impairs subsequent performance in demanding speech perception tasks and modulates auditory-cortex responses to speech sounds. These findings are consistent with the suggestion that the motor cortex contributes to speech perception. This article describes how to localize the lip representation in the motor cortex and how to define the appropriate stimulation intensity for carrying out both single-pulse and repetitive TMS experiments.

Transcranial magnetic stimulation (TMS) has proven to be a useful tool in investigating the role of the articulatory motor cortex in speech perception.&#160; This article describes how to record motor evoked potentials (MEPs) from the lip muscles and how to disrupt the motor lip representation using repetitive TMS.

Transcranial magnetic stimulation (TMS) has proven to be a useful tool in investigating the role of the articulatory motor cortex in speech perception. ...

fMRI Mapping of Brain Activity Associated with the Vocal Production of Consonant and Dissonant Intervals

The neural correlates of consonance and dissonance perception have been widely studied, but not the neural correlates of consonance and dissonance production. The most straightforward manner of musical production is singing, but, from an imaging perspective, it still presents more challenges than listening because it involves motor activity. The accurate singing of musical intervals requires integration between auditory feedback processing and vocal motor control in order to correctly produce each note. This protocol presents a method that permits the monitoring of neural activations associated with the vocal production of consonant and dissonant intervals. Four musical intervals, two consonant and two dissonant, are used as stimuli, both for an auditory discrimination test and a task that involves first listening to and then reproducing given intervals. Participants, all female vocal students at the conservatory level, were studied using functional Magnetic Resonance Imaging (fMRI) during the performance of the singing task, with the listening task serving as a control condition. In this manner, the activity of both the motor and auditory systems was observed, and a measure of vocal accuracy during the singing task was also obtained. Thus, the protocol can also be used to track activations associated with singing different types of intervals or with singing the required notes more accurately. The results indicate that singing dissonant intervals requires greater participation of the neural mechanisms responsible for the integration of external feedback from the auditory and sensorimotor systems than does singing consonant intervals.

The neural correlates of listening to consonant and dissonant intervals have been widely studied, but the neural mechanisms associated with production of consonant and dissonant intervals are less well known. In this article, behavioral tests and fMRI are combined with interval identification and singing tasks to describe these mechanisms.

The neural correlates of consonance and dissonance perception have been widely studied, but not the neural correlates of consonance and dissonance ...

Functional Neuroimaging Using Ultrasonic Blood-brain Barrier Disruption and Manganese-enhanced MRI

Although mice are the dominant model system for studying the genetic and molecular underpinnings of neuroscience, functional neuroimaging in mice remains technically challenging. One approach, Activation-Induced Manganese-enhanced MRI (AIM MRI), has been used successfully to map neuronal activity in rodents 1-5. In AIM MRI, Mn2+ acts a calcium analog and accumulates in depolarized neurons 6,7. Because Mn2+ shortens the T1 tissue property, regions of elevated neuronal activity will enhance in MRI. Furthermore, Mn2+ clears slowly from the activated regions; therefore, stimulation can be performed outside the magnet prior to imaging, enabling greater experimental flexibility. However, because Mn2+ does not readily cross the blood-brain barrier (BBB), the need to open the BBB has limited the use of AIM MRI, especially in mice.
One tool for opening the BBB is ultrasound. Though potentially damaging, if ultrasound is administered in combination with gas-filled microbubbles (i.e., ultrasound contrast agents), the acoustic pressure required for BBB opening is considerably lower. This combination of ultrasound and microbubbles can be used to reliably open the BBB without causing tissue damage 8-11.
Here, a method is presented for performing AIM MRI by using microbubbles and ultrasound to open the BBB. After an intravenous injection of perflutren microbubbles, an unfocused pulsed ultrasound beam is applied to the shaved mouse head for 3 minutes. For simplicity, we refer to this technique of BBB Opening with Microbubbles and UltraSound as BOMUS 12. Using BOMUS to open the BBB throughout both cerebral hemispheres, manganese is administered to the whole mouse brain. After experimental stimulation of the lightly sedated mice, AIM MRI is used to map the neuronal response.
To demonstrate this approach, herein BOMUS and AIM MRI are used to map unilateral mechanical stimulation of the vibrissae in lightly sedated mice 13. Because BOMUS can open the BBB throughout both hemispheres, the unstimulated side of the brain is used to control for nonspecific background stimulation. The resultant 3D activation map agrees well with published representations of the vibrissae regions of the barrel field cortex 14. The ultrasonic opening of the BBB is fast, noninvasive, and reversible; and thus this approach is suitable for high-throughput and/or longitudinal studies in awake mice.

A technique is described for broadly opening the blood-brain barrier in the mouse using microbubbles and ultrasound. Using this technique, manganese can be administered to the mouse brain. Because manganese is an MRI contrast agent that accumulates in depolarized neurons, this approach enables imaging of neuronal activity.

Although mice are the dominant model system for studying the genetic and molecular underpinnings of neuroscience, functional neuroimaging in mice remains ...

Neuroscience

A Lightweight, Headphones-based System for Manipulating Auditory Feedback in Songbirds

Experimental manipulations of sensory feedback during complex behavior have provided valuable insights into the computations underlying motor control and sensorimotor plasticity1. Consistent sensory perturbations result in compensatory changes in motor output, reflecting changes in feedforward motor control that reduce the experienced feedback error. By quantifying how different sensory feedback errors affect human behavior, prior studies have explored how visual signals are used to recalibrate arm movements2,3 and auditory feedback is used to modify speech production4-7. The strength of this approach rests on the ability to mimic naturalistic errors in behavior, allowing the experimenter to observe how experienced errors in production are used to recalibrate motor output.
Songbirds provide an excellent animal model for investigating the neural basis of sensorimotor control and plasticity8,9. The songbird brain provides a well-defined circuit in which the areas necessary for song learning are spatially separated from those required for song production, and neural recording and lesion studies have made significant advances in understanding how different brain areas contribute to vocal behavior9-12. However, the lack of a naturalistic error-correction paradigm - in which a known acoustic parameter is perturbed by the experimenter and then corrected by the songbird - has made it difficult to understand the computations underlying vocal learning or how different elements of the neural circuit contribute to the correction of vocal errors13.
The technique described here gives the experimenter precise control over auditory feedback errors in singing birds, allowing the introduction of arbitrary sensory errors that can be used to drive vocal learning. Online sound-processing equipment is used to introduce a known perturbation to the acoustics of song, and a miniaturized headphones apparatus is used to replace a songbird's natural auditory feedback with the perturbed signal in real time. We have used this paradigm to perturb the fundamental frequency (pitch) of auditory feedback in adult songbirds, providing the first demonstration that adult birds maintain vocal performance using error correction14. The present protocol can be used to implement a wide range of sensory feedback perturbations (including but not limited to pitch shifts) to investigate the computational and neurophysiological basis of vocal learning.

We describe the design and assembly of miniaturized headphones suitable for replacing a songbird&#x2019;s natural auditory feedback with a manipulated acoustic signal. Online sound processing hardware is used to manipulate song output, introduce real-time errors in auditory feedback via the headphones, and drive vocal motor learning.

Experimental manipulations of sensory feedback during complex behavior have provided valuable insights into the computations underlying motor control and ...

Functional Imaging of Auditory Cortex in Adult Cats using High-field fMRI

Current knowledge of sensory processing in the mammalian auditory system is mainly derived from electrophysiological studies in a variety of animal models, including monkeys, ferrets, bats, rodents, and cats. In order to draw suitable parallels between human and animal models of auditory function, it is important to establish a bridge between human functional imaging studies and animal electrophysiological studies. Functional magnetic resonance imaging (fMRI) is an established, minimally invasive method of measuring broad patterns of hemodynamic activity across different regions of the cerebral cortex. This technique is widely used to probe sensory function in the human brain, is a useful tool in linking studies of auditory processing in both humans and animals and has been successfully used to investigate auditory function in monkeys and rodents. The following protocol describes an experimental procedure for investigating auditory function in anesthetized adult cats by measuring stimulus-evoked hemodynamic changes in auditory cortex using fMRI. This method facilitates comparison of the hemodynamic responses across different models of auditory function thus leading to a better understanding of species-independent features of the mammalian auditory cortex.

Functional studies of the auditory system in mammals have traditionally been conducted using spatially-focused techniques such as electrophysiological recordings. The following protocol describes a method of visualizing large-scale patterns of evoked hemodynamic activity in the cat auditory cortex using functional magnetic resonance imaging.

Current knowledge of sensory processing in the mammalian auditory system is mainly derived from electrophysiological studies in a variety of animal ...

Optogenetic Stimulation of the Auditory Nerve

Direct electrical stimulation of spiral ganglion neurons (SGNs) by cochlear implants (CIs) enables open speech comprehension in the majority of implanted deaf subjects1-6. Nonetheless, sound coding with current CIs has poor frequency and intensity resolution due to broad current spread from each electrode contact activating a large number of SGNs along the tonotopic axis of the cochlea7-9. Optical stimulation is proposed as an alternative to electrical stimulation that promises spatially more confined activation of SGNs and, hence, higher frequency resolution of coding. In recent years, direct infrared illumination of&#160;the cochlea has been used to evoke responses in the auditory nerve10. Nevertheless it requires higher energies than electrical stimulation10,11 and uncertainty remains as to the underlying mechanism12. Here we describe a method based on optogenetics to stimulate SGNs with low intensity blue light, using transgenic mice with neuronal expression of channelrhodopsin 2 (ChR2)13 or virus-mediated expression of the ChR2-variant CatCh14. We used micro-light emitting diodes (&#181;LEDs) and fiber-coupled lasers to stimulate ChR2-expressing SGNs through a small artificial opening (cochleostomy) or the round window. We assayed the responses by scalp recordings of light-evoked potentials (optogenetic auditory brainstem response: oABR) or by microelectrode recordings from the auditory pathway and compared them with acoustic and electrical stimulation.

Cochlear implants (CIs) enable hearing by direct electrical stimulation of the auditory nerve. However, poor frequency and intensity resolution limits the quality of hearing with CIs. Here we describe optogenetic stimulation of the auditory nerve in mice as an alternative strategy for auditory research and developing future CIs.

Direct electrical stimulation of spiral ganglion neurons (SGNs) by cochlear implants (CIs) enables open speech comprehension in the majority of implanted ...

Mapping the After-effects of Theta Burst Stimulation on the Human Auditory Cortex with Functional Imaging

Auditory cortex pertains to the processing of sound, which is at the basis of speech or music-related processing1. However, despite considerable recent progress, the functional properties and lateralization of the human auditory cortex are far from being fully understood. Transcranial Magnetic Stimulation (TMS) is a non-invasive technique that can transiently or lastingly modulate cortical excitability via the application of localized magnetic field pulses, and represents a unique method of exploring plasticity and connectivity. It has only recently begun to be applied to understand auditory cortical function 2. 
An important issue in using TMS is that the physiological consequences of the stimulation are difficult to establish. Although many TMS studies make the implicit assumption that the area targeted by the coil is the area affected, this need not be the case, particularly for complex cognitive functions which depend on interactions across many brain regions 3. One solution to this problem is to combine TMS with functional Magnetic resonance imaging (fMRI). The idea here is that fMRI will provide an index of changes in brain activity associated with TMS. Thus, fMRI would give an independent means of assessing which areas are affected by TMS and how they are modulated 4. In addition, fMRI allows the assessment of functional connectivity, which represents a measure of the temporal coupling between distant regions. It can thus be useful not only to measure the net activity modulation induced by TMS in given locations, but also the degree to which the network properties are affected by TMS, via any observed changes in functional connectivity.
Different approaches exist to combine TMS and functional imaging according to the temporal order of the methods. Functional MRI can be applied before, during, after, or both before and after TMS. Recently, some studies interleaved TMS and fMRI in order to provide online mapping of the functional changes induced by TMS 5-7. However, this online combination has many technical problems, including the static artifacts resulting from the presence of the TMS coil in the scanner room, or the effects of TMS pulses on the process of MR image formation. But more importantly, the loud acoustic noise induced by TMS (increased compared with standard use because of the resonance of the scanner bore) and the increased TMS coil vibrations (caused by the strong mechanical forces due to the static magnetic field of the MR scanner) constitute a crucial problem when studying auditory processing. 
This is one reason why fMRI was carried out before and after TMS in the present study. Similar approaches have been used to target the motor cortex 8,9, premotor cortex 10, primary somatosensory cortex 11,12 and language-related areas 13, but so far no combined TMS-fMRI study has investigated the auditory cortex. The purpose of this article is to provide details concerning the protocol and considerations necessary to successfully combine these two neuroscientific tools to investigate auditory processing. 
Previously we showed that repetitive TMS (rTMS) at high and low frequencies (resp. 10 Hz and 1 Hz) applied over the auditory cortex modulated response time (RT) in a melody discrimination task 2. We also showed that RT modulation was correlated with functional connectivity in the auditory network assessed using fMRI: the higher the functional connectivity between left and right auditory cortices during task performance, the higher the facilitatory effect (i.e. decreased RT) observed with rTMS. However those findings were mainly correlational, as fMRI was performed before rTMS. Here, fMRI was carried out before and immediately after TMS to provide direct measures of the functional organization of the auditory cortex, and more specifically of the plastic reorganization of the auditory neural network occurring after the neural intervention provided by TMS. 
Combined fMRI and TMS applied over the auditory cortex should enable a better understanding of brain mechanisms of auditory processing, providing physiological information about functional effects of TMS. This knowledge could be useful for many cognitive neuroscience applications, as well as for optimizing therapeutic applications of TMS, particularly in auditory-related disorders.

Auditory processing is the basis of speech and music-related processing. Transcranial Magnetic Stimulation (TMS) has been used successfully to study cognitive, sensory and motor systems but has rarely been applied to audition. Here we investigated TMS combined with functional Magnetic Resonance Imaging to understand the functional organization of auditory cortex.

Auditory cortex pertains to the processing of sound, which is at the basis of speech or music-related processing1. However, despite considerable recent ...

Biology

Translational Brain Mapping at the University of Rochester Medical Center: Preserving the Mind Through Personalized Brain Mapping

The Translational Brain Mapping Program at the University of Rochester is an interdisciplinary effort that integrates cognitive science, neurophysiology, neuroanesthesia, and neurosurgery. Patients who have tumors or epileptogenic tissue in eloquent brain areas are studied preoperatively with functional and structural MRI, and intraoperatively with direct electrical stimulation mapping. Post-operative neural and cognitive outcome measures fuel basic science studies about the factors that mediate good versus poor outcome after surgery, and how brain mapping can be further optimized to ensure the best outcome for future patients. In this article, we describe the interdisciplinary workflow that allows our team to meet the synergistic goals of optimizing patient outcome and advancing scientific understanding of the human brain.

This article provides an overview of a multi-modal brain mapping program designed to identify regions of the brain that support critical cognitive functions in individual neurosurgery patients.

The Translational Brain Mapping Program at the University of Rochester is an interdisciplinary effort that integrates cognitive science, neurophysiology, ...

Noninvasive EEG for Comparative Studies of Vocal Perception in Marmosets

Electroencephalography Measurements in Awake Marmosets Listening to Conspecific Vocalizations

Vocal communication plays a crucial role in the social interactions of primates, particularly in survival and social organization. Humans have developed a unique and advanced vocal communication strategy in the form of language. To study the evolution of human language, it is necessary to investigate the neural mechanisms underlying vocal processing in humans, as well as to understand how brain mechanisms have evolved by comparing them with those in nonhuman primates. Herein, we developed a method to noninvasively measure the electroencephalography (EEG) of awake nonhuman primates. This recording method allows for long-term studies without harming the animals, and, importantly, allows us to directly compare nonhuman primate EEG data with human data, providing insights into the evolution of human language. In the current study, we used the scalp EEG recording method to investigate brain activity in response to species-specific vocalizations in marmosets. This study provides novel insights by using scalp EEG to capture widespread neural representations in marmosets during vocal perception, filling gaps in existing knowledge.

Author Spotlight: Investigating Vocal Information Representation in Small Primates and Its Alteration by Psychiatric Disorders Using Noninvasive EEG

To study the evolution of language, comparing brain mechanisms in humans with those in nonhuman primates is important. We developed a method to noninvasively measure the electroencephalography (EEG) of awake animals. It allows us to directly compare EEG data between humans and animals for the long term without harming them.

Vocal communication plays a crucial role in the social interactions of primates, particularly in survival and social organization. Humans have developed a ...

Decoding Auditory Imagery with Multivoxel Pattern Analysis

Source: Laboratories of Jonas T. Kaplan and Sarah I. Gimbel&#8212;University of Southern California
Imagine the sound of a bell ringing. What is happening in the brain when we conjure up a sound like this in the "mind's ear?" There is growing evidence that the brain uses the same mechanisms for imagination that it uses for perception.1 For example, when imagining visual images, the visual cortex becomes activated, and when imagining sounds, the auditory cortex is engaged. However, to what extent are these activations of sensory cortices specific to the content of our imaginations? 
One technique that can help to answer this question is multivoxel pattern analysis (MPVA), in which functional brain images are analyzed using machine-learning techniques.2-3 In an MPVA experiment, we train a machine-learning algorithm to distinguish among the various patterns of activity evoked by different stimuli. For example, we might ask if imagining the sound of a bell produces different patterns of activity in auditory cortex compared with imagining the sound of a chainsaw, or the sound of a violin. If our classifier learns to tell apart the brain activity patterns produced by these three stimuli, then we can conclude that the auditory cortex is activated in a distinct way by each stimulus. One way to think of this kind of experiment is that instead of asking a question simply about the activity of a brain region, we ask a question about the information content of that region. 
In this experiment, based on Meyer et al., 2010,4 we will cue participants to imagine several sounds by presenting them with silent videos that are likely to evoke auditory imagery. Since we are interested in measuring the subtle patterns evoked by imagination in auditory cortex, it is preferable if the stimuli are presented in complete silence, without interference from the loud noises made by the fMRI scanner. To achieve this, we will use a special kind of functional MRI sequence known as sparse temporal sampling. In this approach, a single fMRI volume is acquired 4-5 s after each stimulus, timed to capture the peak of the hemodynamic response.

Source: Laboratories of Jonas T. Kaplan and Sarah I. Gimbel&#8212;University of Southern California
Imagine the sound of a bell ringing. What is happening ...