Corrigendum to "Synthesis and characterization of a (+)-catechin and L-(+)-ascorbic acid cocrystal as a new functional ingredient for tea drinks" [Heliyon 5 (8) (August 2019) e02291].

[This corrects the article DOI: 10.1016/j.heliyon.2019.e02291.].

Synthesis and characterization of a (+)-catechin and L-(+)-ascorbic acid cocrystal as a new functional ingredient for tea drinks.

Tea (Camellia Sinensis) is one of the most popular drink, consumed as infusion or bottled ready to drink beverages. Although tea leaves contain many antioxidants compounds, after processing they can drastically decrease, sometimes up to a full degradation, as in the case of catechin, a very healthy flavan-3-ol. In this context, the synthesis of a cocrystal between (+)-catechin and L-(+)-ascorbic acid, was proved to be a useful strategy to make a new ingredient able to ameliorate the antioxidant profile of both infusions and bottled teas. The obtained cocrystal showed a three-fold higher solubility than (+)catechin and its formation was elucidated unambiguously by FT-IR, thermal (DSC) and diffraction (PXRD) analyses. Antioxidant characteristics of the samples were evaluated by colorimetric assays. As expected, infusions showed much better antioxidant features than ready-to-use lemon and peach teas. The same trend was confirmed after the addition of the cocrystal at two concentration levels. In particular, supplementation at concentration of 2 mg mL-1 improved the bottled tea antioxidant values to the level showed by the not-added infusion tea.

The impact of cultivar on polyphenol and biogenic amine profiles in Calabrian red grapes during winemaking.

In this study, during winemaking, was evaluated the influence of cultivar on bioactive compounds (organic acids, d-(+)-glucose, d-(-)-fructose, biogenic amines (BAs), anthocyanins, polyphenols and flavonoids) and antioxidant activity of Calabrian (Southern Italy) autochthonous grapes (Arvino, Gaglioppo, Greco Nero, Magliocco Canino, Magliocco Dolce and Nocera). Phenolic compounds increased from grapes to wine for all varieties. Arvino grapevine showed the highest DPPH radical scavenging activity, while a promising inhibition of the lipid peroxidation was observed with Greco Nero grapes. BAs were mostly formed during alcoholic fermentation and Arvino always showed the lowest BAs amounts, while Magliocco Canino generally exhibited the highest. Collectively, the results demonstrated that Calabrian autochthonous grapevines were rich in sugars, organic acids and phenolic compounds thus allowing the production of high quality wines.

Modulation of laser-evoked potentials by experimental cutaneous tonic pain.

The present study aimed to investigate whether tonic cutaneous pain exerts any effect on the cortical processing of nociceptive input and if this effect may involve only body parts in pain. Tonic cutaneous pain was obtained in nine healthy human subjects by infusion of a hypertonic saline (5%) in the s.c. tissue over the hypothenar muscles (10 ml/h for 20 min). Nociceptive cutaneous CO2 laser-evoked potentials were recorded after stimulation of the right hand dorsum, which was adjacent to the painful area, and the right perioral region, corresponding to the adjacent cortical sensory area. Laser-evoked potentials were obtained before saline injection, at the peak pain and 20 min after pain disappeared. During saline infusion, the laser-evoked pain to right hand stimulation was reduced and the vertex laser-evoked potentials (N2a-P2, mean latency 181 ms and 319 ms for the N2a and the P2 potentials, respectively), which are generated in the anterior cingulate cortex, were significantly decreased in amplitude compared with the baseline. Moreover, the topography of these potentials was modified by cutaneous pain, shifting from the central toward the parietal region. Dipolar modeling showed that the dipolar source in the anterior cingulate cortex moved backward during saline infusion. This result suggests that cutaneous pain may modify the relative activities of the anterior and posterior anterior cingulate cortex parts, which are thought to be devoted to encode different aspects of pain sensation. No laser-evoked potential change was observed after stimulation of the right perioral region, suggesting that functional changes in the nociceptive system are selective for the painful regions and not for areas with cortical proximity.

Segmental inhibition of cutaneous heat sensation and of laser-evoked potentials by experimental muscle pain.

The aim of the study was to evaluate the effect of tonic muscle pain evoked by injection of 5% hypertonic saline in the right brachioradialis muscle on the somatosensory sensation of laser-evoked heat pain and laser-evoked potentials. The heat pain pathways were studied in 9 healthy human subjects by recording the scalp potentials evoked by CO(2) laser stimuli delivered on four sites: the skin above the right brachioradialis muscle (ipsilateral local pain), the wrist area where muscle pain was referred in all subjects (ipsilateral referred pain), and two areas on the left arm symmetrical to both local and referred pain (contralateral local pain and contralateral referred pain). Laser-evoked potentials were obtained from 31 scalp electrodes before saline injection, during saline infusion (bolus injection with 0.3 ml saline infused over 20 s, followed by a steady infusion rate of 30 ml/h for the next 25 min), and 20 min after muscle pain had disappeared. While the early N1/P1 component (around 130 ms and 145 ms of latency after stimulation of the skin over the brachioradialis muscle and the wrist, respectively) was not affected by muscle pain, the amplitudes of the later vertex laser-evoked potentials (N2 latency of around 175 ms and 210 ms after stimulation of the skin over the brachioradialis muscle and the wrist, respectively; P2 latency of around 305 ms and 335 ms after stimulation of the skin over the brachioradialis muscle and the wrist, respectively) evoked from ipsilateral local pain, ipsilateral referred pain, and contralateral local pain sites were significantly decreased during muscle pain compared with the baseline recording, while they recovered after pain had disappeared. At the same stimulation sites, the rating of the laser-evoked pain sensation was reduced significantly during muscle pain as compared with the baseline and it recovered after pain had disappeared. On the contrary, muscle pain did not show any effect on both laser-evoked pain and laser-evoked potential amplitude when the contralateral referred pain site was stimulated. The muscle pain inhibitory effect on both heat pain sensation and laser-evoked potential amplitude is probably mediated by an ipsilateral and contralateral segmental mechanism which acts also on the referred pain area, while more general inhibitory mechanisms, such as a distraction effect or a diffuse noxious inhibitory control, are excluded by the absence of any effect of muscle pain on laser-evoked pain and laser-evoked potentials obtained from a remote site, such as the contralateral referred pain area. Since muscle pain induced by hypertonic saline injection is very similar to clinical pain, our results can be useful in understanding the pathophysiology of the somatosensory modifications which can be observed in patients with musculoskeletal pain syndromes.

Tensor veli palatini electromyography with surface electrode applied transnasally.

A new technique is proposed for paratubal electromyography, using a surface, non-invasive, electrode applied transnasally under nasopharyngoscope guidance. This electrode records activity of the tensor veli palatini muscle during swallowing. This technique is of interest for two reasons: endoscopic guidance offers the possibility to check correct positioning of the electrode recording at tensor veli palatini muscle level. Introduction of the non-invasive surface electrode is simple and not painful.

Immunohistochemical expression of stem cell markers in pheochromocytomas/paragangliomas is associated with SDHx mutations.

OBJECTIVE: Pheochromocytomas (PCCs) are neuroendocrine tumors that occur in the adrenal medulla, whereas paragangliomas (PGLs) arise from paraganglia in the head, neck, thorax, or abdomen. In a variety of tumors, cancer cells with stem cell-like properties seem to form the basis of tumor initiation because of their ability to self-renew and proliferate. Specifically targeting this small cell population may lay the foundation for more effective therapeutic approaches. In the present study, we intended to identify stem cells in PCCs/PGLs. DESIGN: We examined the immunohistochemical expression of 11 stem cell markers (SOX2, LIN28, NGFR, THY1, PREF1, SOX17, NESTIN, CD117, OCT3/4, NANOG, and CD133) on tissue microarrays containing 208 PCCs/PGLs with different genetic backgrounds from five European centers. RESULTS: SOX2, LIN28, NGFR, and THY1 were expressed in more than 10% of tumors, and PREF1, SOX17, NESTIN, and CD117 were expressed in <10% of the samples. OCT3/4, NANOG, and CD133 were not detectable at all. Double staining for chromogranin A/SOX2 and S100/SOX2 demonstrated SOX2 immunopositivity in both tumor and adjacent sustentacular cells. The expression of SOX2, SOX17, NGFR, LIN28, PREF1, and THY1 was significantly associated with mutations in one of the succinate dehydrogenase (SDH) genes. In addition, NGFR expression was significantly correlated with metastatic disease. CONCLUSION: Immunohistochemical expression of stem cell markers was found in a subset of PCCs/PGLs. Further studies are required to validate whether some stem cell-associated markers, such as SOX2, could serve as targets for therapeutic approaches and whether NGFR expression could be utilized as a predictor of malignancy.

N24 spinal response to tibial nerve stimulation and magnetic resonance imaging in lesions of the lumbosacral spinal cord.

We studied tibial nerve somatosensory evoked potentials (SEPs) in 22 patients with progressive clinical signs of sensory and motor involvement of the lower limbs. Magnetic resonance imaging (MRI) in 21 patients revealed lesions of the thoracolumbar cord in 18 and of the cauda equina in the remaining three. SEP recordings enabled us to clearly differentiate the response generated by the dorsal horns of the lumbosacral cord from the activity generated in the cauda equina dorsal roots. Neurophysiologic findings strongly correlated with the lesion site demonstrated by the MRI (cauda equina, lumbosacral cord, or thoracic cord immediately above the lumbar enlargement). The N24 cord potential was absent with a normal cauda equina response in 10 of 12 patients with MRI signs of lumbosacral cord lesions. Clinical examination often failed to localize the spinal cord as the lesion site, suggesting pure peripheral involvement in six of the 12 patients with MRI signs of lumbosacral cord lesions.

Segmental dysfunction of the cervical cord revealed by abnormalities of the spinal N13 potential in cervical spondylotic myelopathy.

We studied somatosensory potentials (SEPs) evoked by stimulation of radial, median, and ulnar nerves in 11 patients with MRI evidence of cervical spondylosis. All patients presented with progressive spastic paraparesis that was either isolated or associated with lower motor neuron signs in the upper limbs, with preserved joint, touch, pain, and temperature sensations in the four limbs. In all patients, scalp SEPs reflecting the activity of the dorsal column system up to the parietal cortex were normal while segmental cervical cord dysfunction was manifested by an abnormal spinal N13 potential in 95% of radial, 90% of median, and 54% of ulnar nerve SEPs. These subclinical abnormalities of the spinal N13 SEP probably result from reduced blood supply due to compression of the anterior spinal artery in patients with cervical spondylotic myelopathy.

Spinal responses to median and tibial nerve stimulation and magnetic resonance imaging in intramedullary cord lesions.

We recorded median and tibial nerve somatosensory evoked potentials (SEPs) in 18 patients with intramedullary lesions of the cord (intramedullary tumors in 14 patients and syringomyelia cavitations in 4). Patients were divided into four groups on the basis of the longitudinal extension of the lesions as revealed by magnetic resonance imaging. The lesions involved the cervical cord in nine patients (group 1), both cervical and lumbar cord ("holocord" lesion) in two (group 2), the dorsal cord in one (group 3), and the lumbar cord in six (group 4). The recording technique enabled us to analyze clearly the spinal SEPs, labeled for the median nerve as N13, and for the tibial nerve as N24. Both spinal responses are probably generated by the activation of dorsal horn cells and proved useful in revealing focal lesions of the cervical or lumbar cords. Median nerve N13 was abnormal in all group 1 and group 2 patients; in three patients, this was the only median SEP abnormality, suggesting that the dysfunction was limited to the cervical grey matter. Tibial nerve N24 was abnormal in all group 2 and group 4 patients. The abnormality of both cervical and lumbar segmental responses in patients with holocord lesions strongly suggested that both the cervical and lumbar cords were involved. The SEP study was often more effective than the clinical examination in revealing cord involvement and the actual extension of damage. The recording of the spinal SEPs is thus highly sensitive in assessing cord dysfunction in intramedullary lesions, providing that specific recording techniques are used.

Preliminary clinical observations on a new trigeminal reflex: the trigemino-cervical reflex.

Short latency trigemino-cervical reflexes can be recorded from sternocleidomastoid muscle after stimulation of the infraorbital branch of the trigeminal nerve. We studied the trigemino-cervical reflexes and the conventional blink reflex in three patients with an isolated lesion in the medulla oblongata, eight patients with multiple sclerosis, and two patients with supratentorial ischemic lesion. The trigemino-cervical response was abnormal in the patients with an isolated lesion in the medulla oblongata and in all multiple sclerosis patients, whereas both components of the blink reflex were preserved in the patients with a lesion in the medulla oblongata and in half of the patients with multiple sclerosis. The trigemino-cervical reflex was preserved in patients with supratentorial lesions, whereas the late component of the blink reflex was abnormal. These findings suggest that central pathways generating the trigemino-cervical reflex are confined to the medulla oblongata and that they are independent from those generating the long latency (R2) component of the blink reflex. The trigemino-cervical reflex may help in disclosing and localizing brainstem lesions.

Neurophysiologic follow-up of long-term dietary treatment in adult-onset adrenoleukodystrophy.

OBJECTIVE: To monitor the effects of dietary treatment in adult-onset adrenoleukodystrophy (ALD) by means of somatosensory evoked potentials (SEPs) and motor evoked potentials (MEPs). BACKGROUND: SEPs and MEPs have proved useful in revealing signs of progressively severe, central dying-back axonopathy in early stages of adult-onset ALD. METHODS: Eight patients with adult-onset ALD underwent clinical examination, brain and spine MRI, and SEP and MEP studies before and after 3 years of Lorenzo's oil dietary therapy. RESULTS: Before treatment, brain MRI was normal in five patients. Three of these patients had pure spinal SEP abnormalities and in the remaining two patients SEPs showed signs of involvement of both the spinal and cerebral somatosensory tracts. After treatment, the three patients with pure spinal abnormalities showed clinical and neurophysiologic worsening, whereas the two patients with a more advanced stage of disease (exhibited by SEPs) showed substantially unchanged clinical and neurophysiologic features. The patients with abnormal brain MRI at the onset of treatment showed clinical and neurophysiologic worsening. CONCLUSIONS: Lorenzo's oil therapy had no effect on patients with evidence of inflammatory brain lesions. Moreover, in patients without clear signs of inflammatory damage, this treatment does not modify significantly the natural course of the disease. However, because effective treatments should begin before the onset of severe neurologic symptoms, SEPs and MEPs should be considered to evaluate the effectiveness of other experimental treatments in the patient with a negative brain MRI.

Reduced habituation to experimental pain in migraine patients: a CO(2) laser evoked potential study.

The habituation to sensory stimuli of different modalities is reduced in migraine patients. However, the habituation to pain has never been evaluated. Our aim was to assess the nociceptive pathway function and the habituation to experimental pain in patients with migraine. Scalp potentials were evoked by CO(2) laser stimulation (laser evoked potentials, LEPs) of the hand and facial skin in 24 patients with migraine without aura (MO), 19 patients with chronic tension-type headache (CTTH), and 28 control subjects (CS). The habituation was studied by measuring the changes of LEP amplitudes across three consecutive repetitions of 30 trials each (the repetitions lasted 5 min and were separated by 5-min intervals). The slope of the regression line between LEP amplitude and number of repetitions was taken as an index of habituation. The LEPs consisted of middle-latency, low-amplitude responses (N1, contralateral temporal region, and P1, frontal region) followed by a late, high-amplitude, negative-positive complex (N2/P2, vertex). The latency and amplitude of these responses were similar in both patients and controls. While CS and CTTH patients showed a significant habituation of the N2/P2 response, in MO patients this LEP component did not develop any habituation at all after face stimulation and showed a significantly lower habituation than in CS after hand stimulation. The habituation index of the vertex N2/P2 complex exceeded the normal limits in 13 out of the 24 MO patients and in none of the 19 CTTH patients (P<0.0001; Fisher's exact test). Moreover, while the N1-P1 amplitude showed a significant habituation in CS after hand stimulation, it did not change across repetitions in MO patients. In conclusion, no functional impairment of the nociceptive pathways, including the trigeminal pathways, was found in either MO or CTTH patients. But patients with migraine had a reduced habituation, which probably reflects an abnormal excitability of the cortical areas involved in pain processing.

Cisplatin neuropathy: clinical course and neurophysiological findings.

Sixteen patients treated with cisplatin (CDDP) 40 mg/m2 on days 1-5 every 4 weeks for three courses (cumulative dose 600 mg/m2) were clinically and neurophysiologically tested before, during and 1, 3, 6, 9 and 12 months after CDDP administration. The first symptoms of polyneuropathy occurred in 4 of 9 patients after the second course (cumulative dose 400 mg/m2). One month after treatment 1 of 9 patients was asymptomatic, 5 complained of symptoms and 3 showed clinical and neurophysiological signs of polyneuropathy. Three months after CDDP all patients were affected. Clinical and neurophysiological signs of severity progression were noted up to 6 months after treatment with CDDP.

Scalp distribution of the earliest cortical somatosensory evoked potential to tibial nerve stimulation: proposal of a new recording montage.

OBJECTIVE: To investigate the most reliable method to record the earliest cortical somatosensory evoked potential (SEP) after tibial nerve stimulation. The 'gating' phenomenon was used to dissociate the overlapping cortical SEP components. METHODS: In 11 subjects we recorded the scalp SEPs at rest, during the voluntary (active gating) and passive (passive gating) foot movement and during the isometric calf muscle contraction (isometric gating). RESULTS: At the vertex the P40 amplitude was reduced in all the gating conditions. Instead, both the P40 response recorded in the parietal region ipsilateral to the stimulation (indicated as P40par) and the fronto-temporal N37 potential were reduced in amplitude only during the passive foot movement. CONCLUSIONS: The same behaviour of the N37 and P40par potentials suggests that they can represent the opposite counterparts of the same dipolar generator. Instead, the real P40 amplitude, which is affected in all the gating conditions, is recorded at the vertex and might be generated by a different source. We conclude that the montage obtained by referring a temporal electrode contralateral to the stimulation to an ipsilateral parietal lead can reliably record the earliest cortical component (N37/P40par) after tibial nerve stimulation.

Parietal generators of low- and high-frequency MN (median nerve) SEPs: data from intracortical human recordings.

OBJECTIVE: To identify low and high-frequency median nerve (MN) somatosensory evoked potential (SEP) generators by means of chronically implanted electrodes in the parietal lobe (SI and neighbouring areas) of two epileptic patients. METHODS: Wide-pass short-latency and long-latency SEPs to electrical MN stimulation were recorded in two epileptic patients by stereotactically chronically implanted electrodes in the parietal lobe (SI and neighbouring areas). To study high-frequency responses (HFOs) an off-line digital filtering of depth short-latency SEPs was performed (500-800 Hz, 24 dB roll-off). Spectral analysis was performed by fast Fourier transform. RESULTS: In both patients we recorded a N20/P30 potential followed by a biphasic N50/P70 response. A little negative response in the 100 ms latency range was the last detectable wide-pass SEP in both patients. Two HFOs components (called iP1 and iP2) were detected by mere visual analysis and spectral analysis, and were supposed to be originated within the parietal cortex. CONCLUSIONS: This was the very first study that recorded wide bandpass and high frequency SEPs by electrodes, exploring both the lateral and the mesial part of the parietal lobe and particularly that of the post-central gyrus.

Unmasking of an early laser evoked potential by a point localization task.

OBJECTIVES: The investigation of the CO(2) laser evoked potential (LEP) modifications following a point localization task. METHODS: LEPs were recorded from 10 healthy subjects in two different conditions. (1) Task condition: laser stimuli were shifted among 3 different locations on the right hand dorsum, and the subjects were asked to identify the stimulated area. The mean error rate in point localization was 4.5%. (2) Non-task condition: laser pulses were delivered on the first intermetacarpal space, and the subject was asked to count the number of stimuli. The mean error rate in counting was 5.8%. RESULTS: In the task condition, the temporal traces contralateral to the stimulation showed an early positive component (eP, mean peak latency 83 ms) preceding the N1 negativity (mean peak latency 144 ms). At the eP peak latency, topographic maps showed a positivity highly focused on the contralateral temporal region. In the non-task recordings no reliable response was identifiable before the N1 potential. CONCLUSIONS: While no LEP component earlier than the middle-latency N1 potential can be recorded in the non-task condition, a positive response (eP) preceding the N1 component is identifiable in the contralateral temporal region during the spatial localization of painful stimuli. The eP scalp distribution is compatible with its origin from a radial source in the second somatosensory (or insular) area, thus suggesting that the opercular cortex is involved not only in the middle-latency (N1 potential), but also in early pain processing.

Contribution of GABAergic cortical circuitry in shaping somatosensory evoked scalp responses: specific changes after single-dose administration of tiagabine.

OBJECTIVES: To determine whether conventional as well as high-frequency somatosensory evoked potentials (SEPs) to upper limb stimulation are influenced by GABAergic intracortical circuitry. METHODS: We recorded SEPs from 6 healthy volunteers before and after a single-oral administration of tiagabine. Conventional low-frequency SEPs have been obtained after stimulation of the median nerve, as well as after stimulation of the first phalanx of the thumb, which selectively involves cutaneous finger inputs. Median nerve SEPs have been further analyzed after digital narrow-bandpass filtering, to selectively examine high-frequency responses. Lastly, in order to explain scalp SEP distribution before and after tiagabine administration, we performed the brain electrical source analysis (BESA) of raw data. RESULTS: After tiagabine administration, conventional scalp SEPs showed a significant amplitude increase of parietal P24, frontal N24 and central P22 components. Similarly, BESA showed a significant strength increase of the second peak of activation of the first two perirolandic dipoles, which are likely to correspond to the N24/P24 and P22 generators. By contrast, no significant changes of high-frequency SEPs were induced by drug intake. CONCLUSIONS: Our findings support the view that both N24/P24 and P22 SEP components are probably generated by deep spiny cell hyperpolarization, which is strongly increased by inhibitory inputs from GABAergic interneurons. By considering the clear influence of inhibitory circuitry in shaping these SEP components, conventional scalp SEP recording could be useful in the functional assessment of the somatosensory cortex in different physiological and pathological conditions. By contrast, intrinsic firing properties of the cell population generating high-frequency SEP responses are unaffected by the increase of recurrent GABAergic inhibition.

Sources of cortical responses to painful CO(2) laser skin stimulation of the hand and foot in the human brain.

OBJECTIVES: To investigate whether the same dipolar model could explain the scalp CO(2) laser evoked potential (LEP) distribution after either hand or foot skin stimulation. METHODS: LEPs were recorded in 14 healthy subjects after hand and foot skin stimulation and brain electrical source analysis of responses obtained in each individual was performed. RESULTS: A 5 dipolar sources model explained the scalp LEP topography after both hand and foot stimulation. In particular, we showed that the co-ordinates of the two earliest activated dipoles were compatible with source locations in the upper bank of the Sylvian fissure on both sides. These sources did not change their location when the stimulation site was moved from the upper to the lower limb. The other 3 dipoles of our model were activated in the late LEP latency range with a biphasic profile and a location compatible with activation of the cingulate gyrus and deep temporo-insular structures. CONCLUSIONS: The dipolar model previously proposed for the hand stimulation LEPs can also satisfactorily explain the LEP distribution obtained after foot stimulation. The earliest activated Sylvian dipolar sources did not change their location when the upper or lower limb was stimulated, as expected from the close projections of hand and foot in the second somatosensory area. No source in the primary somatosensory area was necessary to model the scalp topography of LEPs to hand and foot stimulation.

Source generators of the early somatosensory evoked potentials to tibial nerve stimulation: an intracerebral and scalp recording study.

OBJECTIVE: To investigate the location of the cerebral generators of the early scalp somatosensory evoked potentials (SEPs) after tibial nerve stimulation. METHODS: Tibial nerve SEPs were recorded in 15 patients, suffering from Parkinson's disease, who underwent implantation of intracerebral (IC) electrodes in the subthalamic nucleus, in the globus pallidum or in the thalamic ventralis intermediate nucleus. SEPs were recorded both from the scalp surface and from the IC leads. RESULTS: The lemniscal P30 response was recorded by all the electrodes. The IC waveforms included a negative N40IC response, followed by a positive (P50IC) and a negative (N60IC) potential. The N40IC, the P50IC and the N60IC potentials did not differ in latency from the P40, the N50 and the P60 responses recorded by the Cz electrode. In 6 patients, in which SEPs were recorded also during the voluntary movement of the stimulated foot (active gating), an amplitude reduction of the SEP components following the P30 potential was observed during movement at the vertex and in the IC traces. Instead, in the contralateral temporal traces the SEP components (N40temp and P50temp) were not modified by active gating, and in the ipsilateral parietal traces only the positive potentials at about 60ms of latency was decreased. CONCLUSIONS: Two differently oriented generators are active in the contralateral hemisphere at both 40 and 50ms of latency after tibial nerve stimulation. One source is oriented perpendicularly to the mesial hemispheric surface and generates the potentials recorded by the contralateral temporal and the ipsilateral parietal leads; the other dipolar source is radial to the hemispheric convexity, and generates the potentials at the vertex and those recorded by the IC electrodes.