Migraine aura: retracting particle-like waves in weakly susceptible cortex

Cortical spreading depression (SD) has been suggested to underlie migraine aura. Despite a precise match in speed, the spatio-temporal patterns of SD and aura symptoms on the cortical surface ordinarily differ in aspects of size and shape. We show that this mismatch is reconciled by utilizing that both pattern types bifurcate from an instability point of generic reaction-diffusion models. To classify these spatio-temporal pattern we suggest a susceptibility scale having the value [sigma]=1 at the instability point. We predict that human cortex is only weakly susceptible to SD ([sigma]<1), and support this prediction by directly matching visual aura symptoms with anatomical landmarks using fMRI retinotopic mapping. We discuss the increased dynamical repertoire of cortical tissue close to [sigma]=1, in particular, the resulting implications on migraine pharmacology that is hitherto tested in the regime ([sigma]>>1), and potentially silent aura occurring below a second bifurcation point at [sigma]=0 on the susceptible scale

Repeatability of short-duration transient visual evoked potentials in normal subjects

To evaluate the within-session and inter-session repeatability of a new, short-duration transient visual evoked potential (SD-tVEP) device on normal individuals, we tested 30 normal subjects (20/20 visual acuity, normal 24-2 SITA Standard VF) with SD-tVEP. Ten of these subjects had their tests repeated within 1–2 months from the initial visit. Synchronized single-channel EEG was recorded using a modified Diopsys Enfant™ System (Diopsys, Inc., Pine Brook, New Jersey, USA). A checkerboard stimulus was modulated at two reversals per second. Two different contrasts of checkerboard reversal patterns were used: 85% Michelson contrast with a mean luminance of 66.25 cd/m2 and 10% Michelson contrast with a mean luminance of 112 cd/m2. Each test lasted 20 s. Both eyes, independently and together, were tested 10 times (5 times at each contrast level). The following information was identified from the filtered N75-P100-N135 complex: N75 amplitude, N75 latency, P100 amplitude, P100 latency, and Delta Amplitude (N75-P100). The median values for each eye’s five SD-tVEP parameters were calculated and grouped into two data sets based on contrast level. Mean age was 27.3 ± 5.2 years. For OD only, the median (95% confidence intervals) of Delta Amplitude (N75-P100) amplitudes at 10% and 85% contrast were 4.6 uV (4.1–5.9) and 7.1 uV (5.15–9.31). The median P100 latencies were 115.2 ms (112.0–117.7) and 104.0 ms (99.9–106.0). There was little within-session variability for any of these parameters. Intraclass correlation coefficients ranged between 0.64 and 0.98, and within subject coefficients of variation were 3–5% (P100 latency) and 15–30% (Delta Amplitude (N75-P100) amplitude). Bland–Altman plots showed good agreement between the first and fifth test sessions (85% contrast Delta Amplitude (N75-P100) delta amplitude, mean difference, 0.48 mV, 95% CI, −0.18–1.12; 85% contrast P100 latency delay, −0.82 ms, 95% CI, −3.12–1.46; 10% contrast Delta Amplitude (N75-P100) amplitude, 0.58 mV, 95% CI, −0.27–1.45; 10% contrast P100 latency delay, −2.05 mV, 95% CI, −5.12–1.01). The inter-eye correlation and agreement were significant for both SD-tVEP amplitude and P100 latency measurements. For the subset of eyes in which the inter-session repeatability was tested, the intraclass correlation coefficients ranged between 0.71 and 0.86 with good agreement shown on Bland–Altman plots. Short-duration transient VEP technology showed good within-session, inter-session repeatability, and good inter-eye correlation and agreement

HyperBrain: Pathway Quiz 18 - Limbic System (The Entorhinal-Parahippocampal Circuit)

One of eighteen quizzes on neuroanatomy accompanying the HyperBrain tutorial. The quizzes require the free Macromedia Flash player plugin. Illustrations modified from "Neuroanatomy - An Atlas of Structures, Sections, and Systems," Fourth Edition, Duane E. Haines, Ph.D., Professor and Chairman, Department of Anatomy, The University of Mississippi Medical Center, Jackson, Mississippi, Copyright 1995. With permission from Lippincott Williams & Wilkins Baltimore, Maryland, USA.Orientation: sagittalAnnotated: fals

HyperBrain: Pathway Quiz 12 - Dorsal Spinocerebellar Tract

One of eighteen quizzes on neuroanatomy accompanying the HyperBrain tutorial. The quizzes require the free Macromedia Flash player plugin. Illustrations modified from "Neuroanatomy - An Atlas of Structures, Sections, and Systems," Fourth Edition, Duane E. Haines, Ph.D., Professor and Chairman, Department of Anatomy, The University of Mississippi Medical Center, Jackson, Mississippi, Copyright 1995. With permission from Lippincott Williams & Wilkins Baltimore, Maryland, USA.Orientation: coronalAnnotated: fals

HyperBrain: Pathway Quiz 9 - Corticospinal Tract

One of eighteen quizzes on neuroanatomy accompanying the HyperBrain tutorial. The quizzes require the free Macromedia Flash player plugin. Illustrations modified from "Neuroanatomy - An Atlas of Structures, Sections, and Systems," Fourth Edition, Duane E. Haines, Ph.D., Professor and Chairman, Department of Anatomy, The University of Mississippi Medical Center, Jackson, Mississippi, Copyright 1995. With permission from Lippincott Williams & Wilkins Baltimore, Maryland, USA.Orientation: coronalAnnotated: fals

HyperBrain: Pathway Quiz 6 - Visual System

One of eighteen quizzes on neuroanatomy accompanying the HyperBrain tutorial. The quizzes require the free Macromedia Flash player plugin. Illustrations modified from "Neuroanatomy - An Atlas of Structures, Sections, and Systems," Fourth Edition, Duane E. Haines, Ph.D., Professor and Chairman, Department of Anatomy, The University of Mississippi Medical Center, Jackson, Mississippi, Copyright 1995. With permission from Lippincott Williams & Wilkins Baltimore, Maryland, USA.Orientation: transverseAnnotated: fals

HyperBrain: Pathway Quiz 15 - Hypothalamus

One of eighteen quizzes on neuroanatomy accompanying the HyperBrain tutorial. The quizzes require the free Macromedia Flash player plugin. Illustrations modified from "Neuroanatomy - An Atlas of Structures, Sections, and Systems," Fourth Edition, Duane E. Haines, Ph.D., Professor and Chairman, Department of Anatomy, The University of Mississippi Medical Center, Jackson, Mississippi, Copyright 1995. With permission from Lippincott Williams & Wilkins Baltimore, Maryland, USA.Orientation: axialAnnotated: fals

HyperBrain: Pathway Quiz 11 - Vestibulospinal Tract

One of eighteen quizzes on neuroanatomy accompanying the HyperBrain tutorial. The quizzes require the free Macromedia Flash player plugin. Illustrations modified from "Neuroanatomy - An Atlas of Structures, Sections, and Systems," Fourth Edition, Duane E. Haines, Ph.D., Professor and Chairman, Department of Anatomy, The University of Mississippi Medical Center, Jackson, Mississippi, Copyright 1995. With permission from Lippincott Williams & Wilkins Baltimore, Maryland, USA.Orientation: coronalAnnotated: fals

HyperBrain: Pathway Quiz 16 - Olfactory System

One of eighteen quizzes on neuroanatomy accompanying the HyperBrain tutorial. The quizzes require the free Macromedia Flash player plugin. Illustrations modified from "Neuroanatomy - An Atlas of Structures, Sections, and Systems," Fourth Edition, Duane E. Haines, Ph.D., Professor and Chairman, Department of Anatomy, The University of Mississippi Medical Center, Jackson, Mississippi, Copyright 1995. With permission from Lippincott Williams & Wilkins Baltimore, Maryland, USA.Orientation: sagittalAnnotated: fals

HyperBrain: Pathway Quiz 5 - Visceral Sensation and Taste

One of eighteen quizzes on neuroanatomy accompanying the HyperBrain tutorial. The quizzes require the free Macromedia Flash player plugin. Illustrations modified from "Neuroanatomy - An Atlas of Structures, Sections, and Systems," Fourth Edition, Duane E. Haines, Ph.D., Professor and Chairman, Department of Anatomy, The University of Mississippi Medical Center, Jackson, Mississippi, Copyright 1995. With permission from Lippincott Williams & Wilkins Baltimore, Maryland, USA.Orientation: coronalAnnotated: fals