- Email: [email protected]
Brain Stimulation – The Field, and the Journal, are going ‘from strength to strength’ From the Editor-in-Chief’s Desk
Brain Stimulation 5 (2012) 173e174
Contents lists available at SciVerse ScienceDirect
Brain Stimulation journal homepage: www.brainstimjrnl.com
Editorial
Brain Stimulation e The Field, and the Journal, are going ‘from strength to strength’ From the Editor-in-Chief’s Desk
Last month I was in Oxford, England, attending the most excellent Magstim Neuroscience Conference and Workshop (known to many of us by its original name e the TMS summer school). Brain Stimulation Deputy Editor Dr. Vincent Walsh and colleagues put together several sizzling sessions of great science, blending lectures with practical hands-on workshops for newcomers to the field. At one point Conference Co-Director Dr. Charlotte Stagg mentioned the journal Brain Stimulation, and stated to the audience that it was going ‘from strength to strength.’ This phrase stuck in my brain and I have since heard it used for soccer clubs, athletes, political groups, etc. It is actually an ancient Hebrew term originally in the Bible, Psalms 84:7. Dr. Stagg was, in my opinion, spot on. This expanded issue of Brain Stimulation (Volume 5, issue 3), highlights this transition to the next phase of growth. Brain Stimulation is increasingly popular. With quick, expert and competent reviews (average 30 days to first decision), medline indexing, near real-time electronic publishing and a solid impact factor, authors are now submitting over 300 manuscripts annually, competing to be published in 4 issues containing around 30 manuscripts. One strategy some journals have taken is to increase the rejection rate, and publish articles based largely on their potential for citation. This would produce a small, slim, narrowly focused journal, with a high impact factor, and the rejected 260 manuscripts being published elsewhere, if at all. In contrast, the publisher and senior editors of Brain Stimulation have decided to remain true to its broad, multi-disciplinary original charter, and to not restrict publication to only 10% of the field. With this issue, and going into next year, Brain Stimulation will be expanding the number of printed pages, allowing the journal to grow in concert with the field. We have chosen to expand the size of the journal with full knowledge that the impact factor might decline. The acceptance rate will remain around 30e40%. This is strength to strength. But Brain Stimulation exists to serve and improve the entire broad field and not simply chase an impact factor number. In this expanded issue, readers can see clearly the growth and explosion of the field. With some trepidation, (we hate pigeonholing) we have grouped manuscripts by technology, but we encourage Brain Stimulation readers to think beyond the different methods, which will come and go, and focus on the translational neuroscience of brain stimulation. In the original aims, we wrote, ‘BRAIN STIMULATION aims to be the premiere journal for publication of original research in the field of neuromodulation.’ Mission accomplished. 1935-861X/$ e see front matter Ó 2012 Elsevier Inc. All rights reserved. http://dx.doi.org/10.1016/j.brs.2012.06.007
‘The purview extends across the entire field of brain stimulation, including noninvasive and invasive techniques, and technologies that alter brain function through the use of electrical, magnetic, radiowave, or focally targeted pharmacological stimulation.’ With the expanded pages, we can continue to meet this broad aim, and not evolve into a journal devoted largely or exclusively to only one method. For example in this issue we have research using tDCS [1e9], TMS [10e19], DBS (and epidural cortical stimulation) [20e24], VNS [25], ECT [26e28] and a new technique e caloric vestibular stimulation [29]. This is breadth. ‘BRAIN STIMULATION encourages manuscripts describing the effects of brain stimulation on basic processes, such as gene expression and other aspects of molecular biology, neurochemical regulation, functional brain activity, sensorimotor function, or cognitive and affective processes at the systems level.’ In this issue there are reports on brain stimulation effects on thermal regulation (tDCS), reading efficiency (tDCS), motor excitability (tDCS), emotional prosody (TMS), seizure quality index (ECT), and neuronal firing activity (VNS, DBS). ‘Likewise, BRAIN STIMULATION seeks the highest level of research on the biophysics and biopsychophysics of stimulation paradigms, as well as the use of these techniques as a probe to outline patterns of neural connectivity.’ This issue has articles on computational models of ECT [28], tDCS [30], and DBS [21]. There are also interesting articles combining brain stimulation with brain imaging. PenaGomez and colleagues use resting state fMRI to investigate tDCS [9], while Hubers and colleagues test whether DTI MRI can explain variations between individuals in TMS measures such as the motor threshold [13]. ‘As an equal partner with this basic emphasis, the journal encourages a strong representation of research on the therapeutic potential and adverse effects of the stimulation technologies.’ In this issue alone there are studies in depression (TMS, tDCS, ECT), schizophrenia (tDCS, TMS, vestibular stimulation), Parkinson’s Disease (DBS), Tourette’s Syndrome (TMS), and Alzheimer’s Disease (TMS, tDCS). A particularly important new area is using Brain Stimulation to help recover from stroke and there are two interesting studies in this issue on post-stroke aphasia e one using implanted cortical electrodes [20], and the other TMS [11]. Can neuromodulation make the blind see, the mute speak or the crippled walk? The discovery science over the next 5e10 years will answer these questions, and will be answered in the pages of Brain Stimulation. There are also important safety papers concerning hearing changes with TMS [19] and dermatitis after tDCS [31].
174
Editorial / Brain Stimulation 5 (2012) 173e174
This fascinating new area of neuromodulation and brain stimulation has so much potential to help us understand how the brain works, how it sometimes goes awry, and then how to fix it with our new set of tools. Evolving and maturing with this exciting field, the journal Brain Stimulation is indeed moving ‘from strength to strength’ by remaining true to the initial vision, growing in size as well as reputation. References [1] Brunoni AR, Nitsche MA, Bolognini N, Bikson M, Wagner T, Merabet L, et al. Clinical research with transcranial direct current stimulation (tDCS): challenges and future directions. Brain Stimul Apr 1, 2011. [2] Raimundo RJ, Uribe CE, Brasil-Neto JP. Lack of clinically detectable acute changes on autonomic or thermoregulatory functions in healthy subjects after transcranial direct current stimulation (tDCS). Brain Stimul Apr 27, 2011. [3] Turkeltaub PE, Benson J, Hamilton RH, Datta A, Bikson M, Coslett HB. Left lateralizing transcranial direct current stimulation improves reading efficiency. Brain Stimul May 5, 2011. [4] Alonzo A, Brassil J, Taylor JL, Martin D, Loo CK. Daily transcranial direct current stimulation (tDCS) leads to greater increases in cortical excitability than second daily transcranial direct current stimulation. Brain Stimul May 20, 2011. [5] Mordillo-Mateos L, Turpin-Fenoll L, Millan-Pascual J, Nunez-Perez N, Panyavin I, Gomez-Arguelles JM, et al. Effects of simultaneous bilateral tDCS of the human motor cortex. Brain Stimul Jun 1, 2011. [6] Boggio PS, Ferrucci R, Mameli F, Martins D, Martins O, Vergari M, et al. Prolonged visual memory enhancement after direct current stimulation in Alzheimer’s disease. Brain Stimul Jul 27, 2011. [7] Javadi AH, Walsh V. Transcranial direct current stimulation (tDCS) of the left dorsolateral prefrontal cortex modulates declarative memory. Brain Stimul Jul 26, 2011. [8] Palm U, Schiller C, Fintescu Z, Obermeier M, Keeser D, Reisinger E, et al. Transcranial direct current stimulation in treatment resistant depression: a randomized double-blind, placebo-controlled study. Brain Stimul Sep 7, 2011. [9] Pena-Gomez C, Sala-Lonch R, Junque C, Clemente IC, Vidal D, Bargallo N, et al. Modulation of large-scale brain networks by transcranial direct current stimulation evidenced by resting-state functional MRI. Brain Stimul Sep 5, 2011. [10] Haffen E, Chopard G, Pretalli JB, Magnin E, Nicolier M, Monnin J, et al. A case report of daily left prefrontal repetitive transcranial magnetic stimulation (rTMS) as an adjunctive treatment for Alzheimer disease. Brain Stimul Mar 30, 2011. [11] Barwood CH, Murdoch BE, Whelan BM, Lloyd D, Riek S, O’Sullivan JD, et al. Improved receptive and expressive language abilities in nonfluent aphasic stroke patients after application of rTMS: an open protocol case series. Brain Stimul Apr 13, 2011. [12] Fitzgerald PB, Daskalakis ZJ. A practical guide to the use of repetitive transcranial magnetic stimulation in the treatment of depression. Brain Stimul Apr 17, 2011. [13] Hubers A, Klein JC, Kang JS, Hilker R, Ziemann U. The relationship between TMS measures of functional properties and DTI measures of microstructure of the corticospinal tract. Brain Stimul Apr 20, 2011. [14] Wu SW, Gilbert DL. Altered neurophysiologic response to intermittent theta burst stimulation in Tourette syndrome. Brain Stimul May 1, 2011. [15] Muller PA, Pascual-Leone A, Rotenberg A. Safety and tolerability of repetitive transcranial magnetic stimulation in patients with pathologic positive sensory phenomena: a review of literature. Brain Stimul Jun 14, 2011.
[16] Balconi M, Bortolotti A. Detection of the facial expression of emotion and selfreport measures in empathic situations are influenced by sensorimotor circuit inhibition by low-frequency rTMS. Brain Stimul Jun 17, 2011. [17] Barr MS, Farzan F, Tran LC, Fitzgerald PB, Daskalakis ZJ. A randomized controlled trial of sequentially bilateral prefrontal cortex repetitive transcranial magnetic stimulation in the treatment of negative symptoms in schizophrenia. Brain Stimul Jul 13, 2011. [18] Alba-Ferrara L, Ellison A, Mitchell RL. Decoding emotional prosody: resolving differences in functional neuroanatomy from fMRI and lesion studies using TMS. Brain Stimul Jul 21, 2011. [19] Tringali S, Perrot X, Collet L, Moulin A. Repetitive transcranial magnetic stimulation: hearing safety considerations. Brain Stimul Jul 26, 2011. [20] Balossier A, Etard O, Descat C, Vivien D, Emery E. Epidural electrical stimulation to improve chronic poststroke aphasia: a 5-year follow-up. Brain Stimul May 10, 2011. [21] Chaturvedi A, Foutz TJ, McIntyre CC. Current steering to activate targeted neural pathways during deep brain stimulation of the subthalamic region. Brain Stimul Jun 2, 2011. [22] Seifried C, Weise L, Hartmann R, Gasser T, Baudrexel S, Szelenyi A, et al. Intraoperative microelectrode recording for the delineation of subthalamic nucleus topography in Parkinson’s disease. Brain Stimul Jul 8, 2011. [23] Ricchi V, Zibetti M, Angrisano S, Merola A, Arduino N, Artusi CA, et al. Transient effects of 80 Hz stimulation on gait in STN DBS treated PD patients: a 15 months follow-up study. Brain Stimul Jul 31, 2011. [24] Contarino MF, Bour LJ, Bot M, van den Munckhof P, Speelman JD, Schuurman PR, et al. Tremor-specific neuronal oscillation pattern in dorsal subthalamic nucleus of parkinsonian patients. Brain Stimul Apr 27, 2011. [25] Manta S, El Mansari M, Blier P. Novel attempts to optimize vagus nerve stimulation parameters on serotonin neuronal firing activity in the rat brain. Brain Stimul May 11, 2011. [26] Chao YL, Chen HH, Chen CH. Effects of repeated electroconvulsive shock on methamphetamine-induced behavioral abnormalities in mice. Brain Stimul May 10, 2011. [27] Dinwiddie SH, Glick DB, Goldman MB. The effect of propofol-remifentanil anesthesia on selected seizure quality indices in electroconvulsive therapy. Brain Stimul Jul 26, 2011. [28] Bai S, Loo C, Al Abed A, Dokos S. A computational model of direct brain excitation induced by electroconvulsive therapy: comparison among three conventional electrode placements. Brain Stimul Aug 9, 2011. [29] Levine J, Toder D, Geller V, Kraus M, Gauchman T, Puterman M, et al. Beneficial effects of caloric vestibular stimulation on denial of illness and manic delusions in schizoaffective disorder: a case report. Brain Stimul Apr 8 2011. [30] Bikson M, Datta A. Guidelines for precise and accurate computational models of tDCS. Brain Stimul Jul 3, 2011. [31] Riedel P, Kabisch S, Ragert P, von Kriegstein K. Contact dermatitis after transcranial direct current stimulation. Brain Stimul Oct 1, 2011.
Mark S. George* Medical University of South Carolina, Psychiatry, 502 N, IOP, 67 President St., Charleston, SC 29425 * Corresponding author. Tel.: (843) 876-5142; fax: (843) 792-5702. E-mail address: [email protected] Available online 9 July 2012
Contents lists available at SciVerse ScienceDirect
Brain Stimulation journal homepage: www.brainstimjrnl.com
Editorial
Brain Stimulation e The Field, and the Journal, are going ‘from strength to strength’ From the Editor-in-Chief’s Desk
Last month I was in Oxford, England, attending the most excellent Magstim Neuroscience Conference and Workshop (known to many of us by its original name e the TMS summer school). Brain Stimulation Deputy Editor Dr. Vincent Walsh and colleagues put together several sizzling sessions of great science, blending lectures with practical hands-on workshops for newcomers to the field. At one point Conference Co-Director Dr. Charlotte Stagg mentioned the journal Brain Stimulation, and stated to the audience that it was going ‘from strength to strength.’ This phrase stuck in my brain and I have since heard it used for soccer clubs, athletes, political groups, etc. It is actually an ancient Hebrew term originally in the Bible, Psalms 84:7. Dr. Stagg was, in my opinion, spot on. This expanded issue of Brain Stimulation (Volume 5, issue 3), highlights this transition to the next phase of growth. Brain Stimulation is increasingly popular. With quick, expert and competent reviews (average 30 days to first decision), medline indexing, near real-time electronic publishing and a solid impact factor, authors are now submitting over 300 manuscripts annually, competing to be published in 4 issues containing around 30 manuscripts. One strategy some journals have taken is to increase the rejection rate, and publish articles based largely on their potential for citation. This would produce a small, slim, narrowly focused journal, with a high impact factor, and the rejected 260 manuscripts being published elsewhere, if at all. In contrast, the publisher and senior editors of Brain Stimulation have decided to remain true to its broad, multi-disciplinary original charter, and to not restrict publication to only 10% of the field. With this issue, and going into next year, Brain Stimulation will be expanding the number of printed pages, allowing the journal to grow in concert with the field. We have chosen to expand the size of the journal with full knowledge that the impact factor might decline. The acceptance rate will remain around 30e40%. This is strength to strength. But Brain Stimulation exists to serve and improve the entire broad field and not simply chase an impact factor number. In this expanded issue, readers can see clearly the growth and explosion of the field. With some trepidation, (we hate pigeonholing) we have grouped manuscripts by technology, but we encourage Brain Stimulation readers to think beyond the different methods, which will come and go, and focus on the translational neuroscience of brain stimulation. In the original aims, we wrote, ‘BRAIN STIMULATION aims to be the premiere journal for publication of original research in the field of neuromodulation.’ Mission accomplished. 1935-861X/$ e see front matter Ó 2012 Elsevier Inc. All rights reserved. http://dx.doi.org/10.1016/j.brs.2012.06.007
‘The purview extends across the entire field of brain stimulation, including noninvasive and invasive techniques, and technologies that alter brain function through the use of electrical, magnetic, radiowave, or focally targeted pharmacological stimulation.’ With the expanded pages, we can continue to meet this broad aim, and not evolve into a journal devoted largely or exclusively to only one method. For example in this issue we have research using tDCS [1e9], TMS [10e19], DBS (and epidural cortical stimulation) [20e24], VNS [25], ECT [26e28] and a new technique e caloric vestibular stimulation [29]. This is breadth. ‘BRAIN STIMULATION encourages manuscripts describing the effects of brain stimulation on basic processes, such as gene expression and other aspects of molecular biology, neurochemical regulation, functional brain activity, sensorimotor function, or cognitive and affective processes at the systems level.’ In this issue there are reports on brain stimulation effects on thermal regulation (tDCS), reading efficiency (tDCS), motor excitability (tDCS), emotional prosody (TMS), seizure quality index (ECT), and neuronal firing activity (VNS, DBS). ‘Likewise, BRAIN STIMULATION seeks the highest level of research on the biophysics and biopsychophysics of stimulation paradigms, as well as the use of these techniques as a probe to outline patterns of neural connectivity.’ This issue has articles on computational models of ECT [28], tDCS [30], and DBS [21]. There are also interesting articles combining brain stimulation with brain imaging. PenaGomez and colleagues use resting state fMRI to investigate tDCS [9], while Hubers and colleagues test whether DTI MRI can explain variations between individuals in TMS measures such as the motor threshold [13]. ‘As an equal partner with this basic emphasis, the journal encourages a strong representation of research on the therapeutic potential and adverse effects of the stimulation technologies.’ In this issue alone there are studies in depression (TMS, tDCS, ECT), schizophrenia (tDCS, TMS, vestibular stimulation), Parkinson’s Disease (DBS), Tourette’s Syndrome (TMS), and Alzheimer’s Disease (TMS, tDCS). A particularly important new area is using Brain Stimulation to help recover from stroke and there are two interesting studies in this issue on post-stroke aphasia e one using implanted cortical electrodes [20], and the other TMS [11]. Can neuromodulation make the blind see, the mute speak or the crippled walk? The discovery science over the next 5e10 years will answer these questions, and will be answered in the pages of Brain Stimulation. There are also important safety papers concerning hearing changes with TMS [19] and dermatitis after tDCS [31].
174
Editorial / Brain Stimulation 5 (2012) 173e174
This fascinating new area of neuromodulation and brain stimulation has so much potential to help us understand how the brain works, how it sometimes goes awry, and then how to fix it with our new set of tools. Evolving and maturing with this exciting field, the journal Brain Stimulation is indeed moving ‘from strength to strength’ by remaining true to the initial vision, growing in size as well as reputation. References [1] Brunoni AR, Nitsche MA, Bolognini N, Bikson M, Wagner T, Merabet L, et al. Clinical research with transcranial direct current stimulation (tDCS): challenges and future directions. Brain Stimul Apr 1, 2011. [2] Raimundo RJ, Uribe CE, Brasil-Neto JP. Lack of clinically detectable acute changes on autonomic or thermoregulatory functions in healthy subjects after transcranial direct current stimulation (tDCS). Brain Stimul Apr 27, 2011. [3] Turkeltaub PE, Benson J, Hamilton RH, Datta A, Bikson M, Coslett HB. Left lateralizing transcranial direct current stimulation improves reading efficiency. Brain Stimul May 5, 2011. [4] Alonzo A, Brassil J, Taylor JL, Martin D, Loo CK. Daily transcranial direct current stimulation (tDCS) leads to greater increases in cortical excitability than second daily transcranial direct current stimulation. Brain Stimul May 20, 2011. [5] Mordillo-Mateos L, Turpin-Fenoll L, Millan-Pascual J, Nunez-Perez N, Panyavin I, Gomez-Arguelles JM, et al. Effects of simultaneous bilateral tDCS of the human motor cortex. Brain Stimul Jun 1, 2011. [6] Boggio PS, Ferrucci R, Mameli F, Martins D, Martins O, Vergari M, et al. Prolonged visual memory enhancement after direct current stimulation in Alzheimer’s disease. Brain Stimul Jul 27, 2011. [7] Javadi AH, Walsh V. Transcranial direct current stimulation (tDCS) of the left dorsolateral prefrontal cortex modulates declarative memory. Brain Stimul Jul 26, 2011. [8] Palm U, Schiller C, Fintescu Z, Obermeier M, Keeser D, Reisinger E, et al. Transcranial direct current stimulation in treatment resistant depression: a randomized double-blind, placebo-controlled study. Brain Stimul Sep 7, 2011. [9] Pena-Gomez C, Sala-Lonch R, Junque C, Clemente IC, Vidal D, Bargallo N, et al. Modulation of large-scale brain networks by transcranial direct current stimulation evidenced by resting-state functional MRI. Brain Stimul Sep 5, 2011. [10] Haffen E, Chopard G, Pretalli JB, Magnin E, Nicolier M, Monnin J, et al. A case report of daily left prefrontal repetitive transcranial magnetic stimulation (rTMS) as an adjunctive treatment for Alzheimer disease. Brain Stimul Mar 30, 2011. [11] Barwood CH, Murdoch BE, Whelan BM, Lloyd D, Riek S, O’Sullivan JD, et al. Improved receptive and expressive language abilities in nonfluent aphasic stroke patients after application of rTMS: an open protocol case series. Brain Stimul Apr 13, 2011. [12] Fitzgerald PB, Daskalakis ZJ. A practical guide to the use of repetitive transcranial magnetic stimulation in the treatment of depression. Brain Stimul Apr 17, 2011. [13] Hubers A, Klein JC, Kang JS, Hilker R, Ziemann U. The relationship between TMS measures of functional properties and DTI measures of microstructure of the corticospinal tract. Brain Stimul Apr 20, 2011. [14] Wu SW, Gilbert DL. Altered neurophysiologic response to intermittent theta burst stimulation in Tourette syndrome. Brain Stimul May 1, 2011. [15] Muller PA, Pascual-Leone A, Rotenberg A. Safety and tolerability of repetitive transcranial magnetic stimulation in patients with pathologic positive sensory phenomena: a review of literature. Brain Stimul Jun 14, 2011.
[16] Balconi M, Bortolotti A. Detection of the facial expression of emotion and selfreport measures in empathic situations are influenced by sensorimotor circuit inhibition by low-frequency rTMS. Brain Stimul Jun 17, 2011. [17] Barr MS, Farzan F, Tran LC, Fitzgerald PB, Daskalakis ZJ. A randomized controlled trial of sequentially bilateral prefrontal cortex repetitive transcranial magnetic stimulation in the treatment of negative symptoms in schizophrenia. Brain Stimul Jul 13, 2011. [18] Alba-Ferrara L, Ellison A, Mitchell RL. Decoding emotional prosody: resolving differences in functional neuroanatomy from fMRI and lesion studies using TMS. Brain Stimul Jul 21, 2011. [19] Tringali S, Perrot X, Collet L, Moulin A. Repetitive transcranial magnetic stimulation: hearing safety considerations. Brain Stimul Jul 26, 2011. [20] Balossier A, Etard O, Descat C, Vivien D, Emery E. Epidural electrical stimulation to improve chronic poststroke aphasia: a 5-year follow-up. Brain Stimul May 10, 2011. [21] Chaturvedi A, Foutz TJ, McIntyre CC. Current steering to activate targeted neural pathways during deep brain stimulation of the subthalamic region. Brain Stimul Jun 2, 2011. [22] Seifried C, Weise L, Hartmann R, Gasser T, Baudrexel S, Szelenyi A, et al. Intraoperative microelectrode recording for the delineation of subthalamic nucleus topography in Parkinson’s disease. Brain Stimul Jul 8, 2011. [23] Ricchi V, Zibetti M, Angrisano S, Merola A, Arduino N, Artusi CA, et al. Transient effects of 80 Hz stimulation on gait in STN DBS treated PD patients: a 15 months follow-up study. Brain Stimul Jul 31, 2011. [24] Contarino MF, Bour LJ, Bot M, van den Munckhof P, Speelman JD, Schuurman PR, et al. Tremor-specific neuronal oscillation pattern in dorsal subthalamic nucleus of parkinsonian patients. Brain Stimul Apr 27, 2011. [25] Manta S, El Mansari M, Blier P. Novel attempts to optimize vagus nerve stimulation parameters on serotonin neuronal firing activity in the rat brain. Brain Stimul May 11, 2011. [26] Chao YL, Chen HH, Chen CH. Effects of repeated electroconvulsive shock on methamphetamine-induced behavioral abnormalities in mice. Brain Stimul May 10, 2011. [27] Dinwiddie SH, Glick DB, Goldman MB. The effect of propofol-remifentanil anesthesia on selected seizure quality indices in electroconvulsive therapy. Brain Stimul Jul 26, 2011. [28] Bai S, Loo C, Al Abed A, Dokos S. A computational model of direct brain excitation induced by electroconvulsive therapy: comparison among three conventional electrode placements. Brain Stimul Aug 9, 2011. [29] Levine J, Toder D, Geller V, Kraus M, Gauchman T, Puterman M, et al. Beneficial effects of caloric vestibular stimulation on denial of illness and manic delusions in schizoaffective disorder: a case report. Brain Stimul Apr 8 2011. [30] Bikson M, Datta A. Guidelines for precise and accurate computational models of tDCS. Brain Stimul Jul 3, 2011. [31] Riedel P, Kabisch S, Ragert P, von Kriegstein K. Contact dermatitis after transcranial direct current stimulation. Brain Stimul Oct 1, 2011.
Mark S. George* Medical University of South Carolina, Psychiatry, 502 N, IOP, 67 President St., Charleston, SC 29425 * Corresponding author. Tel.: (843) 876-5142; fax: (843) 792-5702. E-mail address: [email protected] Available online 9 July 2012