Belen Lafon's research while affiliated with City College of New York and other places

Publications (17)

Preprint
Full-text available
There is evidence that transcranial direct current stimulation can boost learning performance. Arguably, this boost is related to synaptic plasticity. However, the precise effects on synaptic plasticity and its underlying mechanisms are not known. We hypothesized that direct current stimulation modulates endogenous Hebbian plasticity mechanisms due...
Article
Full-text available
It has come to our attention that we did not specify whether the stimulation magnitudes we report in this Article are peak amplitudes or peak-to-peak. All references to intensity given in mA in the manuscript refer to peak-to-peak amplitudes, except in Fig. 2, where the model is calibrated to 1 mA peak amplitude, as stated. In the original version...
Article
Full-text available
Transcranial electrical stimulation has widespread clinical and research applications, yet its effect on ongoing neural activity in humans is not well established. Previous reports argue that transcranial alternating current stimulation (tACS) can entrain and enhance neural rhythms related to memory, but the evidence from non-invasive recordings ha...
Poster
Transcranial electric stimulation aims to stimulate the brain by applying weak electrical currents at the scalp. However, the magnitude and spatial distribution of electric fields in the human brain are unknown. Here we measure electric potentials intracranially in ten epilepsy patients and estimate electric fields across the entire brain by levera...
Article
Key points: Direct current stimulation (DCS) polarity specifically modulates synaptic efficacy during a continuous train of presynaptic inputs, despite synaptic depression. DCS polarizes afferent axons and postsynaptic neurons, boosting cooperativity between synaptic inputs. Polarization of afferent neurons in upstream brain regions may modulate a...
Article
Full-text available
Transcranial direct current stimulation (tDCS) is an emerging non-invasive neuromodulation technique that applies mA currents at the scalp to modulate cortical excitability. Here, we present a novel magnetic resonance imaging (MRI) technique, which detects magnetic fields induced by tDCS currents. This technique is based on Ampere’s law and exploit...
Article
The objective of this review is to summarize the contribution of animal research using direct current stimulation (DCS) to our understanding of the physiological effects of transcranial direct current stimulation (tDCS). We comprehensively address experimental methodology in animal studies, broadly classified as: 1) transcranial stimulation; 2) dir...
Article
Since 2000, there has been rapid acceleration in the use of tDCS in both clinical and cognitive neuroscience research, encouraged by the simplicity of the technique (two electrodes and a battery powered stimulator) and the perception that tDCS protocols can be simply designed by placing the anode over the cortex to "excite," and the cathode over co...
Article
Background The importance of slow-wave sleep (SWS), hallmarked by the occurrence of sleep slow oscillations (SO), for the consolidation of hippocampus-dependent memories has been shown in numerous studies. Previously, the application of transcranial direct current stimulation, oscillating at the frequency of endogenous slow oscillations, during SWS...
Article
Functional magnetic resonance imaging (fMRI) of brain activation during transcranial electrical stimulation is used to provide insight into the mechanisms of neuromodulation and targeting of particular brain structures. However, the passage of current through the body may interfere with the concurrent detection of blood oxygen level dependent (BOLD...

Citations

... Both learning specificity and increased associativity, as implicated networks become more communicative in the future due to coincidental pre-and postsynaptic firing, have been demonstrated during tDCS. By interacting with cell membrane polarization, tDCS augments traditional Hebbian learning where anodal tDCS can increase the coincidence rate of pre-and postsynaptic firing, and thus potentially enhance long-term potentiation (LTP) and decrease long-term depression (LTD; Kronberg et al., 2017Kronberg et al., , 2019Rahman et al., 2017). Increases in firing in coactive regions through a process called "spreading activation" during the application of tDCS may then promote interregion connectivity, particularly through the recruitment of axons or the release of TNF-α by astrocytes (Monai et al., 2016;Stellwagen & Malenka, 2006). ...
... Some of the commonly used PoC instruments are mass spectrometers [80,81], spectroscopes [82,83], smart wearable devices [84][85][86], imagers [87,88] and transcranial electric stimulation (TES) [89,90]. Moreover, nextgeneration PoC devices such as paper-based diagnostic tools, novel assay formats, and lab-on-a-chip platforms are imminent [91]. ...
... The current in vivo estimations of E-fields that are induced by tDCS and tACS in the human brain mainly come from recordings that have been conducted on animals (NHPs) and subjects undergoing neurosurgery (see Figures 1-3 and Tables 1-3). Therefore, the available results need to be carefully considered because: (I) although NHPs are similar to humans, they still present remarkable differences [12,30] (see Section 5); (II) a diseased subject might present aberrant networks or an altered anatomy as a result of the conditions [24,31,32] or the treatments that they are undergoing [33]; (III) the presence of metallic implants and surgical procedures may interfere with the recordings [27] (see Section 5); (IV) heterogeneous stimulation protocols were applied (see Table 4); (V) tentative recording set-ups, that were typically designed for recording neural activity or local field potentials [34], were used (see Section 3). However, taken together, the results represent a first step towards an in vivo characterization of tDCS-and tACS-induced Efields, potentially suggesting also a role of these techniques in the novel field of noninvasive deep brain stimulation (NDBS), with optimized protocols already being proposed [35]. ...
... physiological effects in neurons (Huang et al., 2017;Jefferys et al., 2003;Ozen et al., 2010), and with this montage, the electric field between the sites can be negligible even in the antiphase condition. ...
... For EF magnitudes below 40 V/m, every 1 V/m of stimulation intensity will typically induce a membrane polarization of about 0.12 V/m in pyramidal cells (Bikson et al., 2004). While the underlying mechanisms of DC fields in epileptiform bursts suppression appear to be represented by membrane hyperpolarization (Ghai et al., 2000;Rahman et al., 2017), the mechanisms underlying AC effects would be more complex (Bikson et al., 2001;Lian et al., 2003). Indeed, AC stimulation induces an increase (2.5 mM ± 0.5, n = 5) in extracellular K+ concentration lasting for the whole stimulus duration and related to burst suppression (Lian et al., 2003). ...
... in the brain is expected due to the smaller head size and thinner scalp of younger subjects. At present there are no published validations of high-resolution E-field models with direct measurements in the same subjects , although an ongoing effort in this direction has been an- nounced [71]. Other approaches to validate the accuracy of the FEM forward models have been indirect, for example by comparing to scalp potential [69] or neurophysiological measure- ments [12, 13] . ...
... Both approaches share the finite element method for mathematical calculation of the electric field, and the opportunity for freely setting the stimulation parameters (electrode size and position, and current intensity). For validation of the models, electric field predictions from computational modeling have been compared with empirical measurements in a few studies [57], including direct in vivo measures of the tDCS-induced electric field by intracranial recordings [44,58], and indirect neuroimaging approaches [59]. Intracranial measurements have shown the importance of some stimulation parameters, such as electrode placement [57], and the precision of tissue conductivity values of simulations [44], for the accuracy of electric field calculations. ...
... They have, for example, suggested the presence of maximal E-fields nearby the electrodes [16], or the role of cerebrospinal fluid and ventricular space in spreading the E-field to the deep structures [17]. Also, they have predicted intracerebral E-fields of no more than about 0.5 mV/mm for every 1 mA applied, but only in targeted regions [18][19][20][21], with weaker amplitudes being recorded across the brain [22]. However, computational simulations require a modelling process that includes remarkable caveats, such as in choosing the set of tissue conductivities [11,23]. ...
... The direction of current with respect to the orientation of the somatodendritic axes of neurons being stimulated is a primary determinant of the physiological impact of tDCS [21][22][23][24][25][26][27]. Current flowing parallel to the somatodendritic axis -hereon referred to as 'radial' orientation -can cause somatic depolarisation or hyperpolarisation: current flowing inward from dendrite to soma causes depolarisation, whereas current flowing outward from soma to dendrite causes hyperpolarisation ( Figure 1). ...
... The direction of current with respect to the orientation of the somatodendritic axes of neurons being stimulated is a primary determinant of the physiological impact of tDCS [21][22][23][24][25][26][27]. Current flowing parallel to the somatodendritic axis -hereon referred to as 'radial' orientation -can cause somatic depolarisation or hyperpolarisation: current flowing inward from dendrite to soma causes depolarisation, whereas current flowing outward from soma to dendrite causes hyperpolarisation ( Figure 1). ...