Transcranial Magnetic Stimulation (TMS) is a noninvasive neuromodulation technique which allows experimenters to modulate the threshold for activation of proximal brain regions without the need for a surgical procedure. The TMS apparatus consists of a moving coil and two pulse generators (stimulators), which create a strong and fast-flowing electrical current that is converted into a magnetic field in the coil. The positioning of the coil over the scalp allows this magnetic pulse to generate an electrical field in subjacent cortical regions of the brain, with two possible effects: (i) axonal depolarization facilitating the excitation of nearby neural populations or networks, (ii) axonal hyperpolarization leading to the inhibition of proximal brain regions (also called a "silent period").
TMS stimulation can be utilized via single-, double- or triple-pulse application, which allows for the identification of intracortical areas and networks involved in specific cognitive, affective or behavioral processes. In addition to the anatomical circumspection used to define the area of activation, these pulses are able to measure the moment in time (with millisecond precision) in which these cortical areas process associated cognitive phenomena. Another form of TMS modulation utilizes a rapid succession of repetitive EM pulses, called repetitive TMS (rTMS), to modulate cortical excitability for a longer period of time. Studies conducted on the motor cortex have identified a pattern of cortical inhibition in low frequency rTMS (≤ 1 Hz) and increased cortical excitability in high frequency rTMS (≥ 5 Hz). It is important to note that these values may vary according to other parameters of stimulation such as the intensity and duration of stimulation. Other parameters may also affect the efficacy of TMS and rTMS, such as the screen distance, coil orientation and coil type, and the shape, intensity, and frequency of the magnetic pulse.
In our laboratory, we use TMS to investigate the cortical excitability associated with motor imagery in participants diagnosed with autism and controls, among other cognitive domains.
Transcranial Direct Current Stimulation (tDCS) is a non-invasive technique which can modulate the excitability of brain regions without the need for surgical intervention. It is considered a safe and inexpensive technique, and has consequently been widely used as a research tool in different laboratories around the world. A weak electric current (1 to 3 milliamperes) is applied to the region of interest, usually located on the scalp, by the placement of at least two electrodes of different electrical polarities, negative (cathodic) and positive (anodic). These electrodes can be placed on a different body region to the head (extraencephalic), but at least one must be placed on the scalp to allow the electric current to pass through the brain. The electrodes used in tDCS usually have a surface area of 35 cm², but other sizes can be used ranging from 9 to 40 cm². Stimulation sessions often last for 5 to 30 minutes and can be applied to the subject either in a resting condition or during the performance of cognitive tasks. The effect of tDCS is due to the alteration in the spontaneous activity of neural populations by means of variation in the polarization of the membrane of these neurons from the direct current. In addition, effects on brain plasticity can be observed in response to longer or periodic stimulations by means of long-term potentiation mechanisms (LTP).
Given its function of modulating cortical activity, tDCS has been shown to be useful in neuroscience research. This technique allows us to investigate the role of cortical regions of the brain in cognitive, affective and behavioural processes. By modulating the activity of a cortical area with this technique we can evaluate if the electrical current leads to interference in the performance of a task or activity. Based on studies with motor cortex stimulation, the standard effect observed for tDCS stimulation is increased excitability in the cortical region under the anodic electrode, and greater inhibition under the cathode electrode. However, it is important to emphasize that these effects may vary according to the parameters adopted in the application of this technique, such as: (i) intensity and duration of stimulation; (ii) size, angle and location of the electrodes; (iii) state of the subject during the application, if engaged in some activity or at rest; (iv) individual differences due to changes in brain anatomy, gender, age or hemispheric laterality.
The Cognitive and Social Neuroscience Laboratory is an internationally-renowned research centre for studies using tDCS neuromodulation, with a large number of research articles published by our laboratory and in partnership with universities around the world. The main areas of research conducted using tDCS by our group include: (i) neuropsychiatric disorders, such as depression, adicction, Alzheimer's disease, Parkinson, among others; (ii) social neuroscience, such as pain empathy; (iii) affective and cognitive aspects, such as emotion regulation, multisensory integration, attention and visual processing.
Electroencephalography (EEG) is one of the oldest and most widely-recognised techniques in neuroscience. Developed in the first half of the twentieth century, this non-invasive technique allows for the recording of electrical activity through electrodes placed on the scalp, corresponding to variations over a specific time period in local-field potentials arising from synchronous neural activity in different brain regions. A typical EEG set-up consists of a series of electrodes arranged over a "cap", which capture an electrophysiological signal, and an amplifier connected to a computer that amplify and register the signal received from the electrodes. Free recording of EEG signal is often useful for investigating typical electrophysiological patterns in clinical disorders such as sleep disorder or epilepsy. However, research in cognitive neuroscience often employs analytical techniques that separate the raw EEG signal into distinct markers of cognitive or neural characteristics. The main technique used in our laboratory is the analysis of Event-Related Potentials (ERPs). However, other techniques can be used, such as frequency analysis techniques (spectrography), and spatial localization techniques, such as low resolution electromagnetic tomography (LORETA).
ERP analysis can allows us to track how external stimuli such as sounds or images are processed by the brain with millisecond precision. By averaging and filtering raw EEG data, we can obtain a wave which is assumed to be composed of different components.
Each component of the wave represents the activity of one or more regions of the brain, and from the size of its peak and latency we can infer whether two or more population samples process information from the environment in a similar or different way. Examples of the application of this technique include comparing how groups varying by age, ethnicity, gender, or developmental disorder process socially-relevant stimuli.
Several publications from our laboratory have used EEG to evaluate the electrophysiological activity of clinical and healthy participants in response to social, cognitive and affective phenomena such as: social decision-making, semantic processing and irony, motor mentalization, and visual and attentional processes.
Eye tracking usually employs a non-intrusive device to continually emit infrared or near-infrared light, creating a reflection in the cornea of the participant. The corneal reflection is captured by a camera in the eye tracking device and allows the recording software to calculate a vector formed by the angle between the corneal reflection and the centre of the pupil. The relative distance between each of these features, together with some other features of the reflection enable the recording software to calculate the gaze direction. For the software to be fully capable of capturing eye movements, a calibration procedure is required, where the subject normally follows a simple stimulus such as a dot moving to different points on the monitor screen, while the device continually snapshots the eye regions (with the corneal reflection) to better estimate the spatial coordinates of gaze locations as well as the temporal sequence of the participant’s gaze (Hansen & Ji, 2010). These procedures provide two main measures of eye movement: fixations and saccades, when the eye rests on a particular location and when it moves between locations, respectively. The Social and Cognitive Neuroscience lab has a wide selection of eye tracking devices including the SMI RED500 device, the SMI ETG2 Wireless glasses running the iView software package, and the LC Eyegaze Edge running the Nyan software package. Current projects employing an eye tracking design include research into deficits of face processing in schizophrenia, research into the visual processing in the reading of sentences with ambiguity, research studying the cognitive effort in memory tests, and the effects of social stereotypes and cognitive strategies on academic performance in and mathematical tasks.
Peripheral measures record real-time physiological data derived from activity in the peripheral nervous system (PNS). They include research tools such as electrocardiography (ECG), electrodermal activity (EDA), and electromyography (EMG). Peripheral measurement techniques are important instruments for research in cognitive, affective and social neuroscience as they are low-cost and are relatively easy to apply and analyze.
Electrocardiography, widely used in medical settings for monitoring a patient’s cardiac response, is often employed as an auxiliary measure in experimental psychology or neuroscience, where it allows the experimenter to make inferences about changes in autonomic activity to a specific task (tonic analysis) or stimulus (phasic analysis). Typically, the ECG signal is obtained by means of electrodes positioned on the thorax, wrists and legs, ranging between three and twelve electrode sites. This initial signal is then processed by filtering artifacts and removing noise due to background electrical activity, before starting data analysis. The main ECG analysis technique used in our laboratory is calculation of the inter-beat interval (IBI). However, other techniques can be used such as heart rate (HR), and heart rate variability. Recently, we have chosen to prioritize IBI analysis, since it allows us to understand the frequency of cardiac activity in relation to a given stimulus, by deriving the exact value of the inter-beat interval at different points (ex. at 1000 ms or 500 ms). This allows for a more precise measurement than HR response where a single value is computed every few seconds to estimate the average number of beats per minute (bpm). Our most recent studies using IBI analysis were conducted on the effects of neuromodulation and of meditation training on emotional regulation.
Electrodermal activity, also referred to as skin conductance response and galvanic skin response, is measured by applying an electrical potential between two points on the skin and calculating the electrical current generated. The voltage recorded is greatly affected by the production of sweat, which increases the conductance between the two points. EDA, together with EMG, plays a prominent role in the study of emotional processing, with several thousand studies published employing this method to investigate emotional response. Its widespread use is mainly due to its low-cost, ease of use, non-invasiveness, and flexibility in combining it with the parallel measurement of other techniques such as electroencephalography (EEG), near-infrared spectroscopy (NIRS), and neuromodulation, derived from activity in the central nervous system. Recently, we have employed an EDA design with topics such as emotional regulation, empathy for pain, social pain and decision-making.
If you are interested in participating in some of the research mentioned above and/or participate in future studies in our lab using one of the techniques mentioned above, please click here.
Near infrared spectroscopy (fNIRS) is a technique that uses light emission at specific frequencies on a person's scalp. These light frequencies specifically reflect oxygenated (oxyhemoglobin) and non-oxygenated (deoxyhemoglobin) hemoglobin molecules, thus indicating a change in the concentration of these molecules in the cerebral cortex – a measure similar to that investigated in functional magnetic resonance imaging (fMRI) – making it possible to verify which areas were used in a task. The main advantages of using fNIRS are that it allows the participant greater freedom of movement, and it allows experimenters to conduct experiments in conditions more similar to real life while tracking hemodynamic changes in cortical regions, due to its stream-lined and portable features (Ferrari & Quaresima, 2012). Another advantage of this technique is its ability to distinguish signal noise due to movement from genuine hemodynamic changes. In addition, it is a relatively direct measure of brain activation and has a temporal resolution measured in millisecond intervals, with a spatial resolution equal or superior to similar neuroimaging techniques (Franceschini & Boas, 2004).
The Social and Cognitive Neuroscience lab (SCN Lab) actively employs the Brainsight NIRS machine from Rogue Resolutions LTD, as part of our ongoing research (supported by MackPesquisa). The equipment consists of four bays, each with four light-emitting optodes at two frequencies (685 and 830 nm), eight detectors and four proximity optics, totaling sixteen emitters and thirty-two detectors, allowing for the monitoring of more than seventy-two possible channels on the scalp. It is compatible with transcranial magnetic stimulation, transcranial direct- or alternating-current stimulation, and EEG/MEG. Each channel records relative levels of oxy- and deoxyhemoglobin in the corresponding cortical region, which serves as an indirect measure of neural activation in the region of interest. The signal can be acquired up to a maximum frequency of 100 Hz.
Recent studies employing fNIRS at the SCN lab seek to understand the modulatory effect of oxytocin on cortical activation in intraparietal and ventral pre-motor cortex during the rubber hand illusion conducted with healthy individuals. Other ongoing research is being conducted on clinical disorders such as autism, seeking to more closely map behavioral deficits to possible multisensory changes and underlying neural structures in individuals with autism, and to investigate links between oxytocin modulation and multisensory integration in autism.
Our laboratory is equipped with the BIOPAC MP150 system to assess facial electromyography (EMG), which records facial muscle activity in the face of participants. We are using surface electrodes for these purposes to avoid any harm to participants. Facial muscle activity can give hints regarding affect or cognitive processes present in participants and is thus a useful research tool in social, cognitive, and affective sciences. We are conducting studies using facial EMG to tackle questions in the fields of morality, emotion processing, and attractiveness. Recently, we started to explore the effects of touch on emotion processing.