The authors would like to thank Dr. Nikola Ivanovic for reviewing the protocol and Rahma Sweedy for doing the statistical analysis.

This study received approval from the principal Institutional Review Board (E-21-5737) and was conducted following the ethical principles outlined in the Declaration of Helsinki. Data were retrospectively collected from medical records at our tertiary CI center. Due to the anonymized nature of data analysis, informed consent was not required. The study included 20 ears from patients across various age groups.
Inclusion criteria were as follows: patients with normal inner ear anatomy who received CI between 2020 and 2023, underwent both pre-&#160;and post-operative CT scans, and were implanted with CI devices from the same manufacturer, compatible with the surgical planning software used. Temporal bone CT scans are routinely performed as part of the pre-operative assessment for cochlear implant patients at our center, while post-operative CT scans are only done when medically necessary to minimize radiation exposure. Exclusion criteria included CI patients who had undergone revision surgeries or had cochlear ossification, cochlear otosclerosis, or temporal bone fractures involving the otic capsule. Details of the equipment and software are provided in the Table of Materials.
1. Uploading and measuring cochlear parameters
NOTE: The measurement protocol employed in this study comprised a series of sequential steps designed to assess the effectiveness of the pre-and post-operative CT image fusion technique in evaluating electrode location in CI recipients (Figure 1).
<img alt="Figure 1" class="xfigimg" src="/files/ftp_upload/67062/67062fig01.jpg" /> 
Figure 1: Measurement protocol comparison. This figure illustrates the protocol for measuring cochlear parameters using the Automatic Fusion method compared to the Manual method. <a href="https://jove.unicartagenaproxy.elogim.com/files/ftp_upload/67062/67062fig01large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<ol>
	<li>Press the Import button in the software&#39;s Data Management module to upload the post-operative and pre-operative CT images, and select the DICOM files.</li>
	<li>Manually define the center of&#160;modiolus, round window, and cochlear metrics, including the A-value (cochlear diameter), B-value (cochlear width), and H-value (cochlear height) in the 3D Ear-Cochlea module4 (Figure 2).</li>
	<li>Calculate the Cochlear Duct Length (CDL) using the A and B values, applying the Alexiades method to the Elliptic-Circular Approximation (ECA)2,4. 
	NOTE: The detailed steps of the post-operative analysis are described by Canfarotta et al.21. These measurements provide anatomical landmarks for CDL estimation.</li>
</ol>
<img alt="Figure 2" class="xfigimg" src="/files/ftp_upload/67062/67062fig02.jpg" /> 
Figure 2: Manual measurement of post-operative A, B, and H values. Post-operative images are imported into the software, and the A-value (marked in green), B-value (marked in blue), and H-value (marked in red) are manually measured. <a href="https://jove.unicartagenaproxy.elogim.com/files/ftp_upload/67062/67062fig02large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
2. Electrode contact identification and AID/CF calculation
<ol>
	<li>Open the Implant Assessment module. The software will automatically identify the twelve electrode contact points on the post-operative CT images.</li>
	<li>Manually adjust the detected contact points, if necessary, before confirming their positions.</li>
	<li>Allow the software to use these points, along with the pre-defined cochlear metrics, to automatically calculate the Angular Insertion Depth (based on Escude et al.22) and the Characteristic Frequency (based on Greenwood et al.23) for each contact (see Figure 3). 
	NOTE: This manual approach is considered the standard method for measuring AID and CF, and it is referred to as &#34;Manual&#34; in this study.</li>
</ol>
<img alt="Figure 3" class="xfigimg" src="/files/ftp_upload/67062/67062fig03.jpg" /> 
Figure 3: Identification of electrode contacts. This figure shows the identification of the twelve electrode contacts from the post-operative CT images. <a href="https://jove.unicartagenaproxy.elogim.com/files/ftp_upload/67062/67062fig03large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
3. Image fusion
<ol>
	<li>Press the Add icon in the user interface to import the pre-operative CT images into the Image Fusion panel.</li>
	<li>Allow the software to automatically begin registering the pre-operative CT images with the pre-uploaded post-operative CT images using the automatic fusion feature, which applies a mutual information algorithm.</li>
	<li>Access the Manual Alignment feature in the pre-operative image menu if manual adjustments to the fusion are needed. This fusion process enhances visualization and allows a more comprehensive assessment of cochlear anatomy and electrode placement with fewer artifacts. The fusion aims to improve visualization for better evaluation (see Figure 4).</li>
</ol>
<img alt="Figure 4" class="xfigimg" src="/files/ftp_upload/67062/67062fig04.jpg" /> 
Figure 4: Fusion of pre-&#160;and post-operative CT images. Pre-operative CT images are imported into the software and fused with post-operative CT images. The overlay is displayed in olive color, with the electrodes highlighted in bright blue. <a href="https://jove.unicartagenaproxy.elogim.com/files/ftp_upload/67062/67062fig04large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
4. Automatic cochlear parameter measurement on pre-operative image
<ol>
	<li>Re-measure the cochlear parameters on the newly imported pre-operative image within the 3D - Cochlea module.</li>
	<li>Select the Automatic option in the module menu to execute automatic cochlear parameter measurements. This feature is available only for pre-operative images without implant electrodes, as no metal artifacts exist.</li>
	<li>Use the automatic algorithm to reconstruct the inner ear anatomy in 3D. The 3D model will serve as the base for the automatic cochlear parameter measurements as described by Abari et al.24. 
	NOTE: The 3D reconstruction aids in precise measurement of cochlear parameters (see Figure 5).</li>
</ol>
<img alt="Figure 5" class="xfigimg" src="/files/ftp_upload/67062/67062fig05.jpg" /> 
Figure 5: Automated measurement of cochlear parameters. From the fused images, the software automatically measures the main cochlear parameters (indicated by green, blue, and red points), performs 3D reconstruction (cochlea in orange, internal auditory canal in green, and semicircular canals in brown), and updates the information regarding the electrode contacts. <a href="https://jove.unicartagenaproxy.elogim.com/files/ftp_upload/67062/67062fig05large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
5. Updating electrode contact points with new cochlear parameters
<ol>
	<li>Confirm the new Cochlear Duct Length (CDL) measurements obtained from the pre-operative images.</li>
	<li>Allow the previously identified electrode contact points from the post-operative images to automatically update with the new cochlear parameter information, defining the &#34;Automatic Fusion&#34; approach.</li>
	<li>Perform calculations based on the fused images (pre-operative and post-operative) for Angular Insertion Depth (AID) and Characteristic Frequency (CF), which are important for confirming electrode array placement, cochlear coverage, and building the Anatomy-Based Fitting (ABF) map (see Figure 5). 
	NOTE: AID and CF are critical for confirming electrode positioning and cochlear coverage in cochlear implant (CI) practice (see Figure 6).</li>
</ol>
<img alt="Figure 6" class="xfigimg" src="/files/ftp_upload/67062/67062fig06.jpg" /> 
Figure 6: Automatic definition of AID and CF. This figure depicts the automatic definition of the AID (Acoustic Impedance Distribution) and CF (Center Frequency) for each individual electrode contact based on the fused images. <a href="https://jove.unicartagenaproxy.elogim.com/files/ftp_upload/67062/67062fig06large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
6. Calculating the mean angular error and frequency error
<ol>
	<li>Calculate the mean angular error between the Manual and Automatic Fusion methods for each electrode contact.</li>
	<li>Calculate the frequency error in semitones between both methods (Manual and Automatic Fusion) for each electrode contact.</li>
	<li>Use these calculations to provide quantitative indicators of the difference and accuracy between the two methods. Note that semitones are the smallest musical intervals commonly used in Western music25.</li>
</ol>
7. Statistical analysis
<ol>
	<li>Feed the manually calculated cochlear parameters, Angular Insertion Depth (AID), and Characteristic Frequency (CF) from post-operative CT imaging, along with the automatically fused calculated data from the pre-and post-operative CT image fusion technique for each electrode contact, into statistical analysis software (R software).</li>
	<li>Use means and standard deviations for descriptive statistics of quantitative variables, while applying counts and percentages for categorical variables.</li>
	<li>Conduct a comparative analysis between the manually measured AID and frequencies and the automatically fused measurements using a pairwise Bonferroni-adjusted paired t-test or Wilcoxon signed rank test, depending on the normality assumption tested using the Shapiro-Wilk test. 
	NOTE: Assume that all comparisons have clinically relevant standardized effect sizes (Cohen&#39;s d)26. Consider a statistically significant P value to be less than 0.05.</li>
</ol>

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Yassin Abdelsamad and Tahir Sharif work for MED-EL with scientific roles only. The authors have no financial interests in the products described in this manuscript and have nothing else to disclose.

The findings of the present study revealed comparable measurements between Manual and Automatic Fusion methods for most cochlear parameters and frequencies. While Manual measurements exhibited marginally higher values for certain parameters, such as the B value and CDL, no clinically significant differences were observed overall. This discrepancy could be attributed to artifacts in the post-operative CT, which may affect measurement accuracy. Furthermore, this study builds upon prior research by specifically evaluating A...

Cochlear implant (CI) surgery is a transformative treatment for individuals with severe-to-profound sensorineural hearing loss, offering substantial improvements in auditory function and quality of life1. A critical factor for the success of CI surgery is the accurate placement of the electrode array within the correct cochlear compartment, specifically the scala tympani, as optimal electrode positioning, is consistently linked to superior hearing outcomes2. Thus, careful pre-operative planning and assessment of cochlear anatomy are essential to ensure the electrode array is positioned appropriately. Ensuring that the electrode array is fully inserted within the scala tympani is crucial for maximizing patient benefits and achieving optimal clinical outcomes3.
Pre-operative estimation of the insertion depth angle of CI electrode arrays is considered important for effective surgical planning. This estimation relies significantly on obtaining accurate measurements of key cochlear parameters, such as cochlear duct length (CDL), from pre-operative computed tomography (CT) scans4. These measurements enable essential predictions regarding cochlear coverage and angular insertion depth during CI surgery when the electrode length is known. A major predictor of CDL is the A-value, defined as the distance between the round window and the farthest point on the basal turn. Prior studies have highlighted the crucial role of pre-operative imaging and planning in guiding surgical decisions and optimizing outcomes for CI recipients5.
Pre-operative CT imaging is standard practice in many CI clinics for evaluating inner ear anatomy and cochlear parameters before surgery. Pre-operative CT provides clear, artifact-free images that support effective planning and optimize surgical procedures6. However, pre-operative CT analysis alone has limitations in accurately predicting the actual angular insertion depth (AID) and center frequency (CF) of electrode contacts along the CI electrode array. Consequently, post-operative imaging remains necessary to confirm electrode array positioning, assess any displacement or translocation, and determine the true AID of each contact7.
Post-operative imaging confirms the accuracy of electrode placement and aids in creating individualized fitting maps tailored to each patient&#39;s unique cochlear anatomy. These fitting maps are essential for optimizing auditory performance by ensuring precise stimulation of the auditory nerve fibers. Recent studies have shown that individualized fitting maps, or anatomy-based fitting (ABF), improve speech comprehension in both quiet and noisy environments compared to standard or clinical fitting maps8,9,10,11,12,13. Additionally, recipients tend to prefer ABF maps when their electrode array achieves adequate stimulation of the cochlea&#39;s apical region8. The frequency-to-place mismatch is the discrepancy between the CF of electrode contacts based on their physical location within the cochlea and the default settings4. Mertens et al. reported that the impact of frequency-to-place mismatch decreases with prolonged device use14. Other studies have demonstrated that reducing frequency-to-place mismatch with ABF in CI recipients enhances speech perception in noisy environments without affecting understanding in quiet settings11,13.
Various imaging modalities, including X-ray15,16, cone-beam CT17, and magnetic resonance imaging (MRI)18,19, have been used to evaluate CI recipients. However, CT imaging remains the preferred method due to its high spatial resolution and ability to capture detailed cochlear anatomy. CT imaging allows for precise assessment of inner ear structures, such as the scala tympani and scala vestibuli, facilitating accurate electrode placement.
Despite the many benefits of CT imaging, certain challenges persist, particularly with low-resolution post-operative scans. Metallic electrode contacts can produce image artifacts that obscure adjacent structures, complicating the accurate measurement of critical parameters like AID and CF. Recent studies have shown that fusing pre-&#160;and post-operative CT scans enhances image clarity over standard scans, enabling more accurate assessments and improving electrode location by providing complementary information from both pre-&#160;and post-operative images20.
Currently, post-operative CT image analysis often involves manual measurements using software tools, which require substantial training, are time-intensive, and may be prone to variability and error, limiting their efficiency and broader applicability. There is limited literature on the potential of automated measurements from fused images to address these limitations and provide reliable measurements of AID for electrode contacts. This research aims to evaluate whether the fusion of pre-&#160;and post-operative CT images can effectively assess cochlear characteristics and electrode placement in CI recipients. It further investigates how image fusion could advance anatomy-based fitting (ABF) and enhance measurement accuracy for both angular insertion depth (AID) and center frequency (CF).

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>CI devices&#160;</td>
			<td>MED-EL, Innsbruck, Austria</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>OTOPLAN software&#160;</td>
			<td>CASCINATION, MED-EL, Innsbruck, Austria</td>
			<td>version 4 (3.0.0)&#160;</td>
			<td>Otology Planning Software</td>
		</tr>
		<tr>
			<td>R software</td>
			<td>R Foundation for Statistical Computing, Vienna, Austria</td>
			<td>version 4.2.2</td>
			<td>Language and Environment for Statistical Computing</td>
		</tr>
	</tbody>
</table>

enhancing electrode location assessment in cochlear implantation via computed tomography image fusion

This study aimed to determine whether fusing pre-&#160;and post-operative computed tomography (CT) images could help in assessing electrode placement and center frequency (CF) in cochlear implant (CI) recipients. A secondary objective was to compare automatic fusion with manual methods for measuring cochlear parameters. The study included twenty ears with CIs that underwent both pre-&#160;and post-operative CT scans. Manual measurements of cochlear parameters were initially taken from the post-operative CT images, followed by automatic detection using fused pre-&#160;and post-operative CT images with otological software (OTOPLAN). Angular insertion depth (AID) and CF of each electrode contact were calculated using both methods, and error differences were assessed. The analysis showed significant differences between the two methods for cochlear width (B-value) and cochlear duct length (CDL); however, these differences were not clinically significant. Furthermore, there was no statistically significant difference in cochlear diameter (A-value). The mean differences were 0.04 mm for the A-value, 0.21 mm for the B-value, and 0.73 mm for the CDL. The comparison of AID and CF revealed non-significant differences between manual and automatic fusion methods across all electrode contacts, except for electrode number five. According to this study, fusing pre-&#160;and post-operative CT images can be used to determine electrode positions in CI recipients. Automatic fused images can potentially measure cochlear parameters, AID, and CF with reduced human interference. Therefore, this method may serve as another basis for creating anatomy-based fitting.

This study included 20 ears from CI recipients, with 11 implants on the left side and nine on the right side. The average age of the participants was 13.3 years, comprising 55% female and 45% male. Table 1 presents a comparative analysis of manual versus automatic fusion methods for measuring cochlear parameters, revealing statistically significant differences in certain measurements. Specifically, manual measurements showed a significantly higher B value and cochlear duct length (CDL) compared to automa...

This protocol demonstrates a method for fusing pre-operative and post-operative computed tomography images for cochlear implant recipients. The approach may enhance the measurement accuracy of insertion depth and the center frequency of electrode array contacts. Additionally, this method has potential applications in anatomy-based fitting, an emerging area within the cochlear implant field.

Enhancing Electrode Location Assessment in Cochlear Implantation via Computed Tomography Image Fusion

This study aimed to determine whether fusing pre-&#160;and post-operative computed tomography (CT) images could help in assessing electrode placement and ...

enhancing-electrode-location-assessment-cochlear-implantation-via

Universidad de Cartagena UDEC

Research

JoVE Journal

Neuroscience

234 Views.  King Saud University. This protocol demonstrates a method for fusing pre-operative and post-operative computed tomography images for cochlear implant recipients. The approach may enhance the measurement accuracy of insertion depth and the center frequency of electrode array contacts. Additionally, this method has potential applications in anatomy-based fitting, an emerging area within the cochlear implant field.

Video: Enhancing Electrode Location Assessment in Cochlear Implantation via Computed Tomography Image Fusion

Electrode Fabrication and Implantation in Aplysia californica for Multi-channel Neural and Muscular Recordings in Intact, Freely Behaving Animals

Recording from key nerves and muscles of Aplysia during feeding behavior allows us to study the patterns of neural control in an intact animal. Simultaneously recording from multiple nerves and muscles gives us precise information about the timing of neural activity. Previous recording methods have worked for two electrodes, but the study of additional nerves or muscles required combining and averaging the recordings of multiple animals, which made it difficult to determine fine details of timing and phasing, because of variability from response to response, and from animal to animal. Implanting four individual electrodes has a very low success rate due to the formation of adhesions that prevent animals from performing normal feeding movements. We developed a new method of electrode fabrication that reduces the bulk of the electrodes inside the animal allowing for normal feeding movements. Using a combination of glues to attach the electrodes results in a more reliable insulation of the electrode which lasts longer, making it possible to record for periods as long as a week. The fabrication technique that we describe could be extended to incorporate several additional electrodes, and would be applicable to vertebrate animals.

Electrode Fabrication and Implantation in Aplysia californica for Multi-channel Neural and Muscular Recordings in Intact, Freely Behaving Animals

A technique is described for implanting four in vivo electrodes to monitor the neuromuscular control of feeding behavior in Aplysia californica.

Recording from key nerves and muscles of Aplysia during feeding behavior allows us to study the patterns of neural control in an intact animal.  ...

Brain Imaging Investigation of the Memory-Enhancing Effect of Emotion

Emotional events tend to be better remembered than non-emotional events1,2. One goal of cognitive and affective neuroscientists is 
to understand the neural mechanisms underlying this enhancing effect of emotion on memory. A method that has proven particularly influential in the 
investigation of the memory-enhancing effect of emotion is the so-called subsequent memory paradigm (SMP). This method was originally used to investigate the 
neural correlates of non-emotional memories3, and more recently we and others also applied it successfully to studies of emotional memory (reviewed in4, 5-7). 
Here, we describe a protocol that allows investigation of the neural correlates of the memory-enhancing effect of emotion using the SMP in conjunction with 
event-related functional magnetic resonance imaging (fMRI). An important feature of the SMP is that it allows separation of brain activity specifically 
associated with memory from more general activity associated with perception. Moreover, in the context of investigating the impact of emotional stimuli, 
SMP allows identification of brain regions whose activity is susceptible to emotional modulation of both general/perceptual and memory-specific processing. 
This protocol can be used in healthy subjects8-15, as well as in clinical patients where there are alterations in the neural correlates of emotion perception 
and biases in remembering emotional events, such as those suffering from depression and post-traumatic stress disorder (PTSD)16, 17.

We present a protocol that uses functional magnetic resonance imaging to investigate the neural correlates of the memory-enhancing effect of emotion. This protocol allows identification of brain activity specifically linked to memory-related processing, contrary to more general perceptual processing, and can be used with healthy and clinical populations.

Emotional events tend to be better remembered than non-emotional events1,2. One goal of cognitive and affective neuroscientists is 
to understand the ...

Electrode Positioning and Montage in Transcranial Direct Current Stimulation

Transcranial direct current stimulation (tDCS) is a technique that has been intensively investigated in the past decade as this method offers a non-invasive and safe alternative to change cortical excitability2. The effects of one session of tDCS can last for several minutes, and its effects depend on polarity of stimulation, such as that cathodal stimulation induces a decrease in cortical excitability, and anodal stimulation induces an increase in cortical excitability that may last beyond the duration of stimulation6. These effects have been explored in cognitive neuroscience and also clinically in a variety of neuropsychiatric disorders &#x2013; especially when applied over several consecutive sessions4. One area that has been attracting attention of neuroscientists and clinicians is the use of tDCS for modulation of pain-related neural networks3,5. Modulation of two main cortical areas in pain research has been explored: primary motor cortex and dorsolateral prefrontal cortex7. Due to the critical role of electrode montage, in this article, we show different alternatives for electrode placement for tDCS clinical trials on pain; discussing advantages and disadvantages of each method of stimulation.

Transcranial direct current stimulation (tDCS) is an established technique to modulate cortical excitability1,2. It has been used as an investigative tool in neuroscience due to its effects on cortical plasticity, easy operation, and safe profile. One area that tDCS has been showing encouraging results is pain alleviation 3-5.

Transcranial direct current stimulation (tDCS) is a technique that has been intensively investigated in the past decade as this method offers a ...

Multi-electrode Array Recordings of Neuronal Avalanches in Organotypic Cultures

The cortex is spontaneously active, even in the absence of any particular input or motor output. During development, this activity is important for the migration and differentiation of cortex cell types and the formation of neuronal connections1. In the mature animal, ongoing activity reflects the past and the present state of an animal into which sensory stimuli are seamlessly integrated to compute future actions. Thus, a clear understanding of the organization of ongoing i.e. spontaneous activity is a prerequisite to understand cortex function. 
Numerous recording techniques revealed that ongoing activity in cortex is comprised of many neurons whose individual activities transiently sum to larger events that can be detected in the local field potential (LFP) with extracellular microelectrodes, or in the electroencephalogram (EEG), the magnetoencephalogram (MEG), and the BOLD signal from functional magnetic resonance imaging (fMRI). The LFP is currently the method of choice when studying neuronal population activity with high temporal and spatial resolution at the mesoscopic scale (several thousands of neurons). At the extracellular microelectrode, locally synchronized activities of spatially neighbored neurons result in rapid deflections in the LFP up to several hundreds of microvolts. When using an array of microelectrodes, the organizations of such deflections can be conveniently monitored in space and time. 
Neuronal avalanches describe the scale-invariant spatiotemporal organization of ongoing neuronal activity in the brain2,3. They are specific to the superficial layers of cortex as established in vitro4,5, in vivo in the anesthetized rat 6, and in the awake monkey7. Importantly, both theoretical and empirical studies2,8-10 suggest that neuronal avalanches indicate an exquisitely balanced critical state dynamics of cortex that optimizes information transfer and information processing.
In order to study the mechanisms of neuronal avalanche development, maintenance, and regulation, in vitro preparations are highly beneficial, as they allow for stable recordings of avalanche activity under precisely controlled conditions. The current protocol describes how to study neuronal avalanches in vitro by taking advantage of superficial layer development in organotypic cortex cultures, i.e. slice cultures, grown on planar, integrated microelectrode arrays (MEA; see also 11-14).

A robust way to study neuronal avalanches, i.e. scale-invariant spatio-temporal activity bursts, indicative of critical state dynamics in cortex. Avalanches emerge spontaneously in developing superficial layers of cultured cortex which allows for long-term measurements of the activity with planar integrated multi-electrode arrays (MEA) under precisely controlled conditions.

The cortex is spontaneously active, even in the absence of any particular input or motor output.  During development, this activity is important for the ...

Long-term Time Lapse Imaging of Mouse Cochlear Explants

Here we present a method for long-term time-lapse imaging of live embryonic mouse cochlear explants. The developmental program responsible for building the highly ordered, complex structure of the mammalian cochlea proceeds for around ten days. In order to study changes in gene expression over this period and their response to pharmaceutical or genetic manipulation, long-term imaging is necessary. Previously, live imaging has typically been limited by the viability of explanted tissue in a humidified chamber atop a standard microscope. Difficulty in maintaining optimal conditions for culture growth with regard to humidity and temperature has placed limits on the length of imaging experiments. A microscope integrated into a modified tissue culture incubator provides an excellent environment for long term-live imaging. In this method we demonstrate how to establish embryonic mouse cochlear explants and how to use an incubator microscope to conduct time lapse imaging using both bright field and fluorescent microscopy to examine the behavior of a typical embryonic day (E) 13 cochlear explant and Sox2, a marker of the prosensory cells of the cochlea, over 5 days.

Live imaging of the embryonic mammalian cochlea is challenging because the developmental processes at hand operate on a temporal gradient over ten days. Here we present a method for culturing and then imaging embryonic cochlear explant tissue taken from a fluorescent reporter mouse over five days.

Here we present a method for long-term time-lapse imaging of live embryonic mouse cochlear explants. The developmental program responsible for building ...

The Power of Interstimulus Interval for the Assessment of Temporal Processing in Rodents

Temporal processing deficits have been implicated as a potential elemental dimension of higher-level cognitive processes, commonly observed in neurocognitive disorders. Despite the popularization of prepulse inhibition (PPI) in recent years, many current protocols promote using a percent of control measure, thereby precluding the assessment of temporal processing. The present study used cross-modal PPI and gap prepulse inhibition (gap-PPI) to demonstrate the benefits of employing a range of interstimulus intervals (ISIs) to delineate effects of sensory modality, psychostimulant exposure, and age. Assessment of sensory modality, psychostimulant exposure, and age reveals the utility of an approach varying the interstimulus interval (ISI) to establish the shape of the ISI function, including increases (sharper curve inflections) or decreases (flattening of the response amplitude curve) in startle amplitude. Additionally, shifts in peak response inhibition, suggestive of a differential sensitivity to the manipulation of ISI, are often revealed. Thus, the systematic manipulation of ISI affords a critical opportunity to evaluate temporal processing, which may reveal the underlying neural mechanisms involved in neurocognitive disorders.

Temporal processing, a preattentive process, may underlie deficits in higher-level cognitive processes, including attention, commonly observed in neurocognitive disorders. Using prepulse inhibition as an exemplar paradigm, we present a protocol for manipulating interstimulus interval (ISI) to establish the shape of the ISI function to provide an assessment of temporal processing.

Temporal processing deficits have been implicated as a potential elemental dimension of higher-level cognitive processes, commonly observed in ...

Chronic Implantation of Multiple Flexible Polymer Electrode Arrays

Simultaneous recordings from large populations of individual neurons across distributed brain regions over months to years will enable new avenues of scientific and clinical development. The use of flexible polymer electrode arrays can support long-lasting recording, but the same mechanical properties that allow for longevity of recording make multiple insertions and integration into a chronic implant a challenge. Here is a methodology by which multiple polymer electrode arrays can be targeted to a relatively spatially unconstrained set of brain areas.
The method utilizes thin-film polymer devices, selected for their biocompatibility and capability to achieve long-term and stable&#160;electrophysiologic recording interfaces. The resultant implant allows accurate and flexible targeting of anatomically distant regions, physical stability for months, and robustness to electrical noise. The methodology supports up to sixteen serially inserted devices across eight different anatomic targets. As previously demonstrated, the methodology is capable of recording from 1024 channels. Of these, the 512 channels in this demonstration used for single neuron recording yielded 375 single units distributed across six recording sites. Importantly, this method also can record single units for at least 160 days.
This implantation strategy, including temporarily bracing each device with a retractable silicon insertion shuttle, involves tethering of devices at their target depths to a skull-adhered plastic base piece that is custom-designed for each set of recording targets, and stabilization/protection of the devices within a silicone-filled, custom-designed plastic case. Also covered is the preparation of devices for implantation, and design principles that should guide adaptation to different combinations of brain areas or array designs.

Described below is a method for implantation of multiple polymer electrode arrays across anatomically distant brain regions for chronic electrophysiological recording in freely moving rats. Preparation and surgical implantation are described in detail, with emphasis on design principles to guide adaptation of these methods for use in other species.

Simultaneous recordings from large populations of individual neurons across distributed brain regions over months to years will enable new avenues of ...

Stimulation Location Determination using a 3D Digitizer with High-Definition Transcranial Direct Current Stimulation

The abundance of neuroimaging data and rapid development of machine learning has made it possible to investigate brain activation patterns. However, causal evidence of brain area activation leading to a behavior is often left missing. Transcranial direct current stimulation (tDCS), which can temporarily alter brain cortical excitability and activity, is a noninvasive neurophysiological tool used to study causal relationships in the human brain. High-definition transcranial direct current stimulation (HD-tDCS) is a noninvasive brain stimulation (NIBS) technique that produces a more focal current compared to conventional tDCS. Traditionally, the stimulation location has been roughly determined through the 10-20 EEG system, because determining precise stimulation points can be difficult. This protocol uses a 3D digitizer with HD-tDCS to increase accuracy in determination of stimulation points. The method is demonstrated using a 3D digitizer for more accurate localization of stimulation points in the right temporo-parietal junction (rTPJ).

Presented here is a protocol to achieve higher accuracy in determination of stimulation location combining a 3D digitizer with high-definition transcranial direct current stimulation.

The abundance of neuroimaging data and rapid development of machine learning has made it possible to investigate brain activation patterns. However, ...

Cochlear Surface Preparation in the Adult Mouse

Auditory processing in the cochlea depends on the integrity of the mechanosensory hair cells. Over a lifetime, hearing loss can be acquired from numerous etiologies such as exposure to excessive noise, the use of ototoxic medications, bacterial or viral ear infections, head injuries, and the aging process. Loss of sensory hair cells is a common pathological feature of the varieties of acquired hearing loss. Additionally, the inner hair cell synapse can be damaged by mild insults. Therefore, surface preparations of cochlear epithelia, in combination with immunolabeling techniques and confocal imagery, are a very useful tool for the investigation of cochlear pathologies, including losses of ribbon synapses and sensory hair cells, changes in protein levels in hair cells and supporting cells, hair cell regeneration, and determination of report gene expression (i.e., GFP) for verification of successful transduction and identification of transduced cell types. The cochlea, a bony spiral-shaped structure in the inner ear, holds the auditory sensory end organ, the organ of Corti (OC). Sensory hair cells and surrounding supporting cells in the OC are contained in the cochlear duct and rest on the basilar membrane, organized in a tonotopic fashion with high-frequency detection occurring in the base and low-frequency in the apex. With the availability of molecular and genetic information and the ability to manipulate genes by knockout and knock-in techniques, mice have been widely used in biological research, including in hearing science. However, the adult mouse cochlea is miniscule, and the cochlear epithelium is encapsulated in a bony labyrinth, making microdissection difficult. Although dissection techniques have been developed and used in many laboratories, this modified microdissection method using cell and tissue adhesive is easier and more convenient. It can be used in all types of adult mouse cochleae following decalcification.

This article presents a modified cochlear surface preparation method that requires decalcification and use of a cell and tissue adhesive to adhere the pieces of cochlear epithelia to 10 mm round cover slips for immunohistochemistry in adult mouse cochleae.

Auditory processing in the cochlea depends on the integrity of the mechanosensory hair cells. Over a lifetime, hearing loss can be acquired from numerous ...

A Benchtop Approach to the Location Specific Blood Brain Barrier Opening using Focused Ultrasound in a Rat Model

Stereotaxic surgery is the gold standard for localized drug and gene delivery to the rodent brain. This technique has many advantages over systemic delivery including precise localization to a target brain region and reduction of off target side effects. However, stereotaxic surgery is highly invasive which limits its translational efficacy, requires long recovery times, and provides challenges when targeting multiple brain regions. Focused ultrasound (FUS) can be used in combination with circulating microbubbles to transiently open the blood brain barrier (BBB) in millimeter sized regions. This allows intracranial localization of systemically delivered agents that cannot normally cross the BBB. This technique provides a noninvasive alternative to stereotaxic surgery. However, to date this technique has yet to be widely adopted in neuroscience laboratories due to the limited access to equipment and standardized methods. The overall goal of this protocol is to provide a benchtop approach to FUS BBB opening (BBBO) that is affordable and reproducible and can therefore be easily adopted by any laboratory.

Focused ultrasound with microbubble agents can open the blood brain barrier focally and transiently. This technique has been used to deliver a wide range of agents across the blood brain barrier. This article provides a detailed protocol for the localized delivery to the rodent brain with or without MRI guidance.

Stereotaxic surgery is the gold standard for localized drug and gene delivery to the rodent brain. This technique has many advantages over systemic ...