FD was supported by a Young Investigator Award from the US National Alliance for Research on Schizophrenia and Depression and a CPRF Award from the Canadian Psychiatric Research Foundation.

I. Task Design, Stimuli, and Experimental Protocol 
<ol>
 <li>The basic task of this protocol is a delayed-response WM task, where novel task-irrelevant emotional and neutral distracters are presented during the delay interval between the memoranda and probes (see Figure 1 for diagram illustrating the original task). Event-related fMRI data are recorded while participants perform this task. Scrambled versions of the actual distracters can also be used as perceptual controls, which have identical basic properties (e.g., spatial frequency and luminance). </li>
</ol>
<img src="/files/ftp_upload/2434/2434fig1.jpg" alt="Figure 1" /> 
 Figure 1. General Diagram of the Delayed-Response Working Memory Task with Distraction (from 6, with permission). Three faces are used in the memoranda in order to strongly engage the dorsal executive system, and pairs of novel distracters are used in order to increase the impact of emotional distraction on WM performance and brain activity. The impact of emotional distracters can also be increased by presenting the pictures in color (not shown), and by pairing distracters with similar emotional and semantic content. In this context, careful attention should be paid to also match emotional and neutral pictures in basic properties, such as brightness and spatial frequency 15, to avoid introducing possible confounds. Participants are instructed to maintain their focus on the WM task while still processing the distracters, and to make quick and accurate responses to the probes by pressing a response button (1 = Old, 2 = New). For stimulus presentation, we used CIGAL (<a href="http://www.nitrc.org/projects/cigal/">http://www.nitrc.org/projects/cigal/</a>). The memoranda and probes can be presented in color or black &amp; white.
<ol start="2">
 <li>It is advised that the sex of the faces in the memoranda has balanced proportions of males (50%) and females (50%). Similar balanced proportion is also advised for the Old (50%) and New (50%) probes. The difficulty of the WM task can be varied by changing these proportions and/or by varying other factors - e.g., the similarity of the facial features among faces from same memorandum and their similarity with the probes, and/or by manipulating the presence/absence of extra-facial features in the memoranda (see also the movie). In addition to faces, other stimuli can also be used as memoranda and probes 9. </li>
 <li> It is recommended that 30-40 trials per condition 6, 11 be used with this design, although given its stability as a "slow-paced" design robust fMRI signal can also be obtained with fewer trials (see Supplemental Materials from 6). This allows collection of fMRI data in ~1.5-2 hrs., which is feasible to use in both healthy and clinical participants. Despite its slight disadvantage due to the relatively lower number of trials that can be involved compared to "fast-paced" designs, this design has the advantages of obtaining more stable single-trial fMRI signal and better separation of the signal associated with individual trials and within trial stimuli/phases, which are also advantageous for functional connectivity analyses. </li>
 <li> Variation of the distracters type also contributes to the versatility of this design, by adapting it according to the goals of investigations and the targeted populations. Emotional and neutral distracters in the original design 6 were selected from the International Affective Picture System 16, but similar effects can be obtained with other novel stimuli that are effective as distracters 12, and/or with manipulations that increase the sensitivity of the WM task in detecting behavioral differences (e.g., by also assessing the participants' confidence in their responses) 11. </li>
 <li> For instance, in a recent study in post-war veterans with or without post-traumatic stress disorder (PTSD) 12, the emotional IAPS pictures inducing general negative emotions were replaced with combat-related pictures. These pictures were expected to induce emotions that are more specifically linked to combat-related traumas, and thus be more effective distracters in combat-exposed cohorts, particularly in the PTSD group. Moreover, stimuli that induce specific negative emotions (e.g., anxiety) or emotionally positive stimuli may also be used as distracters. For example, faces displaying fearful expressions could induce social anxiety, and thus be effective in investigating the impact of transient anxiety-inducing distraction on WM 11. Also, similar effects can be found with positive distracters 17. </li>
 <li> Finally, in conjunction with other measures (e.g., behavioral- and personality-related) this paradigm can also be used to investigate relationships between brain activity and individual differences in various aspects that affect cognitive performance in this task 8, 10, 11. </li>
</ol>
II. Preparing the Subject for the Scan
All participants should provide written informed consent prior to running the experimental protocol, which should be approved by an Ethics Board.
Prior to Entering the Scanning Room
<ol>
 <li> On the day of scanning, participant's current affective state is assessed, to control for the effect of mood on the WM task with distraction. In conjunction with post-scanning assessments, these initial evaluations can be also used to screen for changes in mood as a result of participating in the study 11. </li>
 <li> Prior to the scan, the participant is informed in detail of the scan procedures, and is given specific instructions for the behavioral task. The participant also completes a short practice session to familiarize with the task. </li>
</ol>
Entering the Scanning Room
<ol start="3">
 <li> The participant lies supine on the scanning bed, with additional cushioning for the head, to ensure comfort during the scan and minimize movement. To further minimize head movement, the non-adhesive side of a length of tape may be wrapped lightly around the subject's forehead. Subjects are given ear protection as well as isolation headphones to communicate with the experimenter during the MRI scan.</li>
 <li> The subject's right hand is positioned comfortably on the response box. Before starting data collection, it is critical to make sure that the response buttons work properly and that the subject can see the screen projection clearly for stimulus presentation. An emergency stop button is also placed nearby, so that the subject may indicate any urgent need to stop the scanner. </li>
</ol>
Following the Scanning Session
<ol start="5">
 <li> Additional tasks may be used for further behavioral assessments - e.g., to determine participants' sensitivity to the distracters, by rating the emotional valence/intensity of distracters and/or the subjectively perceived distractibility of the distracters. These ratings can be used to ensure that subjective perception of emotional stimuli used during scanning replicates previous effects shown in the literature, and individual differences in the ratings can be used to investigate their influence on the neural mechanisms mediating the detrimental effect of emotion on cognition 6, 8. </li>
 <li> Assessments of personality traits (e.g., trait anxiety, emotional reactivity) can also be made after the MRI scanning, if not performed prior to scanning 11. </li>
</ol>
III. Data Recording and Analysis
Scanning Parameters 
In the original study 6, we collected MRI data using a 4 Tesla General Electric scanner for MRI recordings, but for the more recent versions of the task we were also successful in collecting MRI data with a 1.5 T scanner 11. In the 4T scanner, series of 30 functional slices (voxel size = 4 x 4 x 4 mm) were acquired axially using an inverse-spiral pulse sequence (TR = 2000 ms; TE = 31 ms; field of view = 256 x 256mm), thus allowing for full-brain coverage. Similarly, in the 1.5 scanner, series of 28 functional slices (voxel size = 4 x 4 x 4 mm), were acquired axially using an echoplanar sequence (TR = 2000 ms; TE = 40 ms; field of view = 256 x 256 mm). High-resolution structural images were also acquired in axial orientation (in-plane resolution = 1 mm2; anatomical-functional ratio = 4:1).
Data Analysis
We use Statistical Parametric Mapping (SPM: <a href="http://www.fil.ion.ucl.ac.uk/spm/">http://www.fil.ion.ucl.ac.uk/spm/</a>) in combination with in-house Matlab-based tools. Pre-processing involves typical steps: quality assurance*, TR alignment, motion correction, co-registration, normalization, and smoothing (using a 8 x 8 x 8 mm Kernel); *basic quality assurance involved visual inspection of the data, to detect gross movements of the participants and motion-related artefacts in the data, as well as identification of volumes with unusual spikes in the MR signal. Individual and group-level statistical analyses involve comparisons of brain activity according to distracter type (emotional vs. neutral distraction). Moreover, correlations of brain imaging data with subjective or objective measures of distractibility (e.g., emotional and distractibility ratings and working memory performance)6,8,11 and/or scores indexing personality measures (e.g., trait anxiety)11 can also be performed, to investigate how brain activity co-varies with individual differences in those measures. Analyses in all of our studies using this protocol have typically focused on activity observed during the delay interval, when the distracters are presented, but activity time-locked to other events (e.g., probes) can also be investigated.
IV. Representative Results
<img src="/files/ftp_upload/2434/2434fig2.jpg" alt="Figure 2" /> 
Figure 2. Opposite Pattern of Activity in the Ventral vs. Dorsal Brain Systems in the Presence of Emotional Distraction (from 6, with permission). Emotional distracters produced enhanced activity in ventral affective brain regions (red blobs), such as the ventrolateral prefrontal cortex (vlPFC) and amygdala (not shown), while producing decreased activity in dorsal executive brain regions (blue blobs), such as dorsolateral prefrontal cortex (dlPFC) and lateral parietal cortex (LPC). The central image shows activation maps of the direct contrast between the most vs. the least distracting conditions (i.e., emotional vs. scrambled), superimposed on a high-resolution brain image displayed in a lateral view of the right hemisphere. The color horizontal bars at the bottom of the brain image indicate the gradient of t values of the activation maps. The line graphs show the time course of activity in representative dorsal and ventral brain regions (indicated by color-coded arrows). The grey rectangular boxes above the x-axes indicate the onset and duration of the memoranda, distracters, and probes, respectively. FFG = Fusiform Gyrus.

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No conflicts of interest declared.

This experimental design provided initial brain imaging evidence that the detrimental effect of emotional distraction on the ongoing cognitive processes entails reciprocal modulations between the HotEmo ventral neural system and the ColdEx dorsal system. This dorso-ventral dissociation was linked to impaired WM performance in the presence of emotional distraction 6, has been systematically replicated in normal 8-11, clinical 12-14, and other altered conditions, such as s...

brain imaging investigation of the impairing effect of emotion on cognition

Emotions can impact cognition by exerting both enhancing (e.g., better memory for emotional events) and impairing (e.g., increased emotional distractibility) effects (reviewed in 1). Complementing our recent protocol 2 describing a method that allows investigation of the neural correlates of the memory-enhancing effect of emotion (see also 1, 3-5), here we present a protocol that allows investigation of the neural correlates of the detrimental impact of emotion on cognition. The main feature of this method is that it allows identification of reciprocal modulations between activity in a ventral neural system, involved in 'hot' emotion processing (HotEmo system), and a dorsal system, involved in higher-level 'cold' cognitive/executive processing (ColdEx system), which are linked to cognitive performance and to individual variations in behavior (reviewed in 1). Since its initial introduction 6, this design has proven particularly versatile and influential in the elucidation of various aspects concerning the neural correlates of the detrimental impact of emotional distraction on cognition, with a focus on working memory (WM), and of coping with such distraction 7,11, in both healthy 8-11 and clinical participants 12-14.

Watch this Scientific Journal Video about Brain Imaging Investigation of the Impairing Effect of Emotion on Cognition at JoVE.com

Brain Imaging Investigation of the Impairing Effect of Emotion on Cognition

We present a protocol that allows investigation of the neural mechanisms mediating the detrimental impact of emotion on cognition, using functional magnetic resonance imaging. This protocol can be used with both healthy and clinical participants.

Emotions can impact cognition by exerting both enhancing (e.g., better memory for emotional events) and impairing (e.g., increased emotional ...

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16.0K ビュー.  University of Alberta. 我々は、機能的磁気共鳴画像法を用いて、認知の感情の有害な影響を媒介する神経機構の調査を可能にするプロトコルを示す。このプロトコルは、健康と臨床の両方の参加者と一緒に使用することができます。

ビデオ: Brain Imaging Investigation of the Impairing Effect of Emotion on Cognition

State-Dependency Effects on TMS:  A Look at Motive Phosphene Behavior

Transcranial magnetic stimulation (TMS) is a non-invasive neurostimulatory and neuromodulatory technique that can transiently or lastingly modulate cortical excitability (either increasing or decreasing it) via the application of localized magnetic field pulses.1,2 Within the field of TMS, the term state dependency refers to the initial, baseline condition of the particular neural region targeted for stimulation. As can be inferred, the effects of TMS can (and do) vary according to this primary susceptibility and responsiveness of the targeted cortical area.3,4,5

In this experiment, we will examine this concept of state dependency through the elicitation and subjective experience of motive phosphenes. Phosphenes are visually perceived flashes of small lights triggered by electromagnetic pulses to the visual cortex. These small lights can assume varied characteristics depending upon which type of visual cortex is being stimulated. In this particular study, we will be targeting motive phosphenes as elicited through the stimulation of V1/V2 and the V5/MT+ complex visual regions.6

In this article, we examine the effects of visually relevant state dependency on TMS induced motive phosphenic presentations.

Transcranial magnetic stimulation (TMS) is a non-invasive neurostimulatory and neuromodulatory technique that can transiently or lastingly modulate ...

Brain Imaging Investigation of the Neural Correlates of Observing Virtual Social Interactions

The ability to gauge social interactions is crucial in the assessment of others&#x2019; intentions. Factors such as facial expressions and body language affect our decisions in personal and professional life alike 1. These "friend or foe" judgements are often based on first impressions, which in turn may affect our decisions to "approach or avoid". Previous studies investigating the neural correlates of social cognition tended to use static facial stimuli 2. Here, we illustrate an experimental design in which whole-body animated characters were used in conjunction with functional magnetic resonance imaging (fMRI) recordings. Fifteen participants were presented with short movie-clips of guest-host interactions in a business setting, while fMRI data were recorded; at the end of each movie, participants also provided ratings of the host behaviour. This design mimics more closely real-life situations, and hence may contribute to better understanding of the neural mechanisms of social interactions in healthy behaviour, and to gaining insight into possible causes of deficits in social behaviour in such clinical conditions as social anxiety and autism 3.

This article demonstrates an experimental design in which whole-body animated characters are used in conjunction with functional magnetic resonance imaging (fMRI) to investigate the neural correlates of observing virtual social interactions.

The ability to gauge social interactions is crucial in the assessment of others&#x2019; intentions. Factors such as facial expressions and body language ...

Brain Imaging Investigation of the Neural Correlates of Emotional Autobiographical Recollection

Recollection of emotional autobiographical memories (AMs) is important to healthy cognitive and affective functioning 1 - remembering positive AMs is associated with increased personal well-being and self-esteem 2, whereas remembering and ruminating on negative AMs may lead to affective disorders 3. Although significant progress has been made in understanding the brain mechanisms underlying AM retrieval in general (reviewed in 4, 5), less is known about the effect of emotion on the subjective re-experience of AMs and the associated neural correlates. This is in part due to the fact that, unlike the investigations of the emotion effect on memory for laboratory-based microevents (reviewed in 6, 7-9), often times AM studies do not have a clear focus on the emotional aspects of remembering personal events (but see 10). Here, we present a protocol that allows investigation of the neural correlates of recollecting emotional AMs using functional magnetic resonance imaging (fMRI). Cues for these memories are collected prior to scanning by means of an autobiographical memory questionnaire (AMQ), therefore allowing for proper selection of emotional AMs based on their phenomenological properties (i.e., intensity, vividness, personal significance). This protocol can be used in healthy and clinical populations alike.

We present a protocol that allows investigation of the neural correlates of recollecting emotional autobiographical memories, using functional magnetic resonance imaging. This protocol can be used with both healthy and clinical participants.

Recollection of emotional autobiographical memories (AMs) is important to healthy cognitive and affective functioning 1 - remembering positive AMs is ...

Brain Imaging Investigation of the Neural Correlates of Emotion Regulation

The ability to control/regulate emotions is an important coping mechanism in the face of emotionally stressful situations. Although significant progress has been made in understanding conscious/deliberate emotion regulation (ER), less is known about non-conscious/automatic ER and the associated neural correlates. This is in part due to the problems inherent in the unitary concepts of automatic and conscious processing1. Here, we present a protocol that allows investigation of the neural correlates of both deliberate and automatic ER using functional magnetic resonance imaging (fMRI). This protocol allows new avenues of inquiry into various aspects of ER. For instance, the experimental design allows manipulation of the goal to regulate emotion (conscious vs. non-conscious), as well as the intensity of the emotional challenge (high vs. low). Moreover, it allows investigation of both immediate (emotion perception) and long-term effects (emotional memory) of ER strategies on emotion processing. Therefore, this protocol may contribute to better understanding of the neural mechanisms of emotion regulation in healthy behaviour, and to gaining insight into possible causes of deficits in depression and anxiety disorders in which emotion dysregulation is often among the core debilitating features.

We present a protocol that allows investigation of the neural correlates of deliberate and automatic emotion regulation, using functional magnetic resonance imaging. This protocol can be used in healthy participants, both young and older, as well as in clinical patients.

The ability to control/regulate emotions is an important coping mechanism in the face of emotionally stressful situations. Although significant progress ...

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 ...

Enabling High Grayscale Resolution Displays and Accurate Response Time Measurements on Conventional Computers

Display systems based on conventional computer graphics cards are capable of generating images with 8-bit gray level resolution. However, most experiments in vision research require displays with more than 12 bits of luminance resolution. Several solutions are available. Bit++ 1 and DataPixx 2 use the Digital Visual Interface (DVI) output from graphics cards and high resolution (14 or 16-bit) digital-to-analog converters to drive analog display devices. The VideoSwitcher 3 described here combines analog video signals from the red and blue channels of graphics cards with different weights using a passive resister network 4 and an active circuit to deliver identical video signals to the three channels of color monitors. The method provides an inexpensive way to enable high-resolution monochromatic displays using conventional graphics cards and analog monitors. It can also provide trigger signals that can be used to mark stimulus onsets, making it easy to synchronize visual displays with physiological recordings or response time measurements.
Although computer keyboards and mice are frequently used in measuring response times (RT), the accuracy of these measurements is quite low. The RTbox is a specialized hardware and software solution for accurate RT measurements. Connected to the host computer through a USB connection, the driver of the RTbox is compatible with all conventional operating systems. It uses a microprocessor and high-resolution clock to record the identities and timing of button events, which are buffered until the host computer retrieves them. The recorded button events are not affected by potential timing uncertainties or biases associated with data transmission and processing in the host computer. The asynchronous storage greatly simplifies the design of user programs. Several methods are available to synchronize the clocks of the RTbox and the host computer. The RTbox can also receive external triggers and be used to measure RT with respect to external events. 
Both VideoSwitcher and RTbox are available for users to purchase. The relevant information and many demonstration programs can be found at <a href="http://lobes.usc.edu/">http://lobes.usc.edu/</a>.

Conventional computer hardware can not generate visual stimuli with sufficiently high grayscale resolution and measure response times with sufficient accuracy. We describe how to use the VideoSwitcher to produce high-resolution monochromatic displays, and the RTbox to measure response times with high accuracy on conventional computer hardware.

Display systems based on conventional computer graphics cards are capable of generating images with 8-bit gray level resolution. However, most experiments ...

Co-analysis of Brain Structure and Function using fMRI and Diffusion-weighted Imaging

The study of complex computational systems is facilitated by network maps, such as circuit diagrams. Such mapping is particularly informative when studying the brain, as the functional role that a brain area fulfills may be largely defined by its connections to other brain areas. In this report, we describe a novel, non-invasive approach for relating brain structure and function using magnetic resonance imaging (MRI). This approach, a combination of structural imaging of long-range fiber connections and functional imaging data, is illustrated in two distinct cognitive domains, visual attention and face perception. Structural imaging is performed with diffusion-weighted imaging (DWI) and fiber tractography, which track the diffusion of water molecules along white-matter fiber tracts in the brain (Figure 1). By visualizing these fiber tracts, we are able to investigate the long-range connective architecture of the brain. The results compare favorably with one of the most widely-used techniques in DWI, diffusion tensor imaging (DTI). DTI is unable to resolve complex configurations of fiber tracts, limiting its utility for constructing detailed, anatomically-informed models of brain function. In contrast, our analyses reproduce known neuroanatomy with precision and accuracy. This advantage is partly due to data acquisition procedures: while many DTI protocols measure diffusion in a small number of directions (e.g., 6 or 12), we employ a diffusion spectrum imaging (DSI)1, 2 protocol which assesses diffusion in 257 directions and at a range of magnetic gradient strengths. Moreover, DSI data allow us to use more sophisticated methods for reconstructing acquired data. In two experiments (visual attention and face perception), tractography reveals that co-active areas of the human brain are anatomically connected, supporting extant hypotheses that they form functional networks. DWI allows us to create a "circuit diagram" and reproduce it on an individual-subject basis, for the purpose of monitoring task-relevant brain activity in networks of interest.

We describe a novel approach for simultaneous analysis of brain function and structure using magnetic resonance imaging (MRI). We assess brain structure with high-resolution diffusion-weighted imaging and white-matter fiber tractography. Unlike standard structural MRI, these techniques allow us to directly relate anatomical connectivity to functional properties of brain networks.

The study of complex computational systems is facilitated by network maps, such as circuit diagrams. Such mapping is particularly informative when ...

In Vivo Two-photon Imaging Of Experience-dependent Molecular Changes In Cortical Neurons

The brain's ability to change in response to experience is essential for healthy brain function, and abnormalities in this process contribute to a variety of brain disorders1,2. To better understand the mechanisms by which brain circuits react to an animal's experience requires the ability to monitor the experience-dependent molecular changes in a given set of neurons, over a prolonged period of time, in the live animal. While experience and associated neural activity is known to trigger gene expression changes in neurons1,2, most of the methods to detect such changes do not allow repeated observation of the same neurons over multiple days or do not have sufficient resolution to observe individual neurons3,4. Here, we describe a method that combines in vivo two-photon microscopy with a genetically encoded fluorescent reporter to track experience-dependent gene expression changes in individual cortical neurons over the course of day-to-day experience. 
One of the well-established experience-dependent genes is Activity-regulated cytoskeletal associated protein (Arc)5,6. The transcription of Arc is rapidly and highly induced by intensified neuronal activity3, and its protein product regulates the endocytosis of glutamate receptors and long-term synaptic plasticity7. The expression of Arc has been widely used as a molecular marker to map neuronal circuits involved in specific behaviors3. In most of those studies, Arc expression was detected by in situ hybridization or immunohistochemistry in fixed brain sections. Although those methods revealed that the expression of Arc was localized to a subset of excitatory neurons after behavioral experience, how the cellular patterns of Arc expression might change with multiple episodes of repeated or distinctive experiences over days was not investigated. 
In vivo two-photon microscopy offers a powerful way to examine experience-dependent cellular changes in the living brain8,9. To enable the examination of Arc expression in live neurons by two-photon microscopy, we previously generated a knock-in mouse line in which a GFP reporter is placed under the control of the endogenous Arc promoter10. This protocol describes the surgical preparations and imaging procedures for tracking experience-dependent Arc-GFP expression patterns in neuronal ensembles in the live animal. In this method, chronic cranial windows were first implanted in Arc-GFP mice over the cortical regions of interest. Those animals were then repeatedly imaged by two-photon microscopy after desired behavioral paradigms over the course of several days. This method may be generally applicable to animals carrying other fluorescent reporters of experience-dependent molecular changes4.

In Vivo Two-photon Imaging Of Experience-dependent Molecular Changes In Cortical Neurons

Experience-dependent molecular changes in neurons are essential for the brain's ability to adapt in response to behavioral challenges. An in vivo two-photon imaging method is described here that allows the tracking of such molecular changes in individual cortical neurons through genetically encoded reporters.

The brain's ability to change in response to experience is essential for healthy brain function, and abnormalities in this process contribute to a variety ...

A Dual Tracer PET-MRI Protocol for the Quantitative Measure of Regional Brain Energy Substrates Uptake in the Rat

We present a method for comparing the uptake of the brain&#39;s two key energy substrates: glucose and ketones (acetoacetate [AcAc] in this case) in the rat. The developed method is a small-animal positron emission tomography (PET) protocol, in which&#160;11C-AcAc and 18F-fluorodeoxyglucose (18F-FDG) are injected sequentially in each animal. This dual tracer PET acquisition is possible because of the short half-life of 11C (20.4 min). The rats also undergo a magnetic resonance imaging (MRI) acquisition seven days before the PET protocol. Prior to image analysis, PET and MRI images are coregistered to allow the measurement of regional cerebral uptake (cortex, hippocampus, striatum, and cerebellum). A quantitative measure of 11C-AcAc and 18F-FDG brain uptake (cerebral metabolic rate; &#956;mol/100 g/min) is determined by kinetic modeling using the image-derived input function (IDIF) method. Our new dual tracer PET protocol is robust and flexible; the two tracers used can be replaced by different radiotracers to evaluate other processes in the brain. Moreover, our protocol is applicable to the study of brain fuel supply in multiple conditions such as normal aging and neurodegenerative pathologies such as Alzheimer&#39;s and Parkinson&#39;s diseases.

Small-animal positron emission tomography enables the assessment of the brain&#39;s two main energy substrates:&#160;glucose and ketones. In the present method, 11C-acetoacetate and 18F-fluorodeoxyglucose are injected sequentially in each animal, and their uptake is measured quantitatively in specific brain regions determined from the magnetic resonance images.

We present a method for comparing the uptake of the brain&#39;s two key energy substrates: glucose and ketones (acetoacetate [AcAc] in this case) in the ...

Effects of Transcranial Alternating Current Stimulation on the Primary Motor Cortex by Online Combined Approach with Transcranial Magnetic Stimulation

Transcranial Alternating Current Stimulation (tACS) is a neuromodulatory technique able to act through sinusoidal electrical waveforms in a specific frequency and in turn modulate ongoing cortical oscillatory activity. This neurotool allows the establishment of a causal link between endogenous oscillatory activity and behavior. Most of the tACS studies have shown online effects of tACS. However, little is known about the underlying action mechanisms of this technique because of the AC-induced artifacts on Electroencephalography (EEG) signals. Here we show a unique approach to investigate online physiological frequency-specific effects of tACS of the primary motor cortex (M1) by using single pulse Transcranial Magnetic Stimulation (TMS) to probe cortical excitability changes. In our setup, the TMS coil is placed over the tACS electrode while Motor Evoked Potentials (MEPs) are collected to test the effects of the ongoing M1-tACS. So far, this approach has mainly been used to study the visual and motor systems. However, the current tACS-TMS setup can pave the way for future investigations of cognitive functions. Therefore, we provide a step-by-step manual and video guidelines for the procedure.

Transcranial Alternating Current Stimulation (tACS) allows the modulation of cortical excitability in a frequency-specific fashion. Here we show a unique approach which combines online tACS with single pulse Transcranial Magnetic Stimulation (TMS) in order to "probe" cortical excitability by means of Motor Evoked Potentials.

Transcranial Alternating Current Stimulation (tACS) is a neuromodulatory technique able to act through sinusoidal electrical waveforms in a specific ...