Large-scale, high-resolution neurophysiological maps underlying FMRI of macaque temporal lobe.

Maps obtained by functional magnetic resonance imaging (fMRI) are thought to reflect the underlying spatial layout of neural activity. However, previous studies have not been able to directly compare fMRI maps to high-resolution neurophysiological maps, particularly in higher level visual areas. Here, we used a novel stereo microfocal x-ray system to localize thousands of neural recordings across monkey inferior temporal cortex (IT), construct large-scale maps of neuronal object selectivity at subvoxel resolution, and compare those neurophysiology maps with fMRI maps from the same subjects. While neurophysiology maps contained reliable structure at the sub-millimeter scale, fMRI maps of object selectivity contained information at larger scales (>2.5 mm) and were only partly correlated with raw neurophysiology maps collected in the same subjects. However, spatial smoothing of neurophysiology maps more than doubled that correlation, while a variety of alternative transforms led to no significant improvement. Furthermore, raw spiking signals, once spatially smoothed, were as predictive of fMRI maps as local field potential signals. Thus, fMRI of the inferior temporal lobe reflects a spatially low-passed version of neurophysiology signals. These findings strongly validate the widespread use of fMRI for detecting large (>2.5 mm) neuronal domains of object selectivity but show that a complete understanding of even the most pure domains (e.g., faces vs nonface objects) requires investigation at fine scales that can currently only be obtained with invasive neurophysiological methods.

Treatment of Super-Refractory Status Epilepticus: A Review.

PURPOSE: Super-refractory status epilepticus (SRSE) presents management challenges due to the absence of randomized controlled trials and a plethora of potential medical therapies. The literature on treatment options for SRSE reports variable success and quality of evidence. This review is a sequel to the 2020 American Epilepsy Society (AES) comprehensive review of the treatment of convulsive refractory status epilepticus (RSE). METHODS: We sought to determine the effectiveness of treatment options for SRSE. We performed a structured literature search (MEDLINE, Embase, CENTRAL, CINAHL) for studies on reported treatments of SRSE. We excluded antiseizure medications (ASMs) covered in the 2016 AES guideline on the treatment of established SE and the convulsive RSE comprehensive review of the 2020 AES. Literature was reviewed on the effectiveness of vagus nerve stimulation, ketogenic diet (KD), lidocaine, inhalation anesthetics, brain surgery, therapeutic hypothermia, perampanel, pregabalin (PGB), and topiramate in the treatment of SRSE. Two authors reviewed each therapeutic intervention. We graded the level of the evidence according to the 2017 classification scheme of the American Academy of Neurology. RESULTS: For SRSE (level U; 39 class IV studies total), insufficient evidence exists to support that perampanel, PGB, lidocaine, or acute vagus nerve stimulation (VNS) is effective. For children and adults with SRSE, insufficient evidence exists to support that the KD is effective (level U; 5 class IV studies). For adults with SRSE, insufficient evidence exists that brain surgery is effective (level U, 7 class IV studies). For adults with SRSE insufficient, evidence exists that therapeutic hypothermia is effective (level C, 1 class II and 4 class IV studies). For neonates with hypoxic-ischemic encephalopathy, insufficient evidence exists that therapeutic hypothermia reduces seizure burden (level U; 1 class IV study). For adults with SRSE, insufficient evidence exists that inhalation anesthetics are effective (level U, 1 class IV study) and that there is a potential risk of neurotoxicity. CONCLUSION: For patients with SRSE insufficient, evidence exists that any of the ASMs reviewed, inhalational anesthetics, ketogenic diet, acute VNS, brain surgery, and therapeutic hypothermia are effective treatments. Data supporting the use of these treatments for SRSE are scarce and limited mainly to small case series and case reports and are confounded by differences in patients' population, and comedications, among other factors.

Fine-scale spatial organization of face and object selectivity in the temporal lobe: do functional magnetic resonance imaging, optical imaging, and electrophysiology agree?

The spatial organization of the brain's object and face representations in the temporal lobe is critical for understanding high-level vision and cognition but is poorly understood. Recently, exciting progress has been made using advanced imaging and physiology methods in humans and nonhuman primates, and the combination of such methods may be particularly powerful. Studies applying these methods help us to understand how neuronal activity, optical imaging, and functional magnetic resonance imaging signals are related within the temporal lobe, and to uncover the fine-grained and large-scale spatial organization of object and face representations in the primate brain.

Adult-onset Rasmussen's Syndrome with associated cortical dysplasia.

We describe a 23-year-old woman with previous right temporal lobe surgeries for underlying cortical dysplasia, presenting with drug-resistant right hemispheric seizures and epilepsia partialis continua (EPC). After anti-seizure medication adjustments, she developed focal status epilepticus with progressive EEG and neuroimaging changes. Cerebrospinal fluid and serum autoimmune panels were negative except for an elevated serum acetylcholine-receptor antibody titer, but she underwent immunosuppressive therapy. Stereotactic-EEG evaluation demonstrated multifocal independent ictal patterns in the right hemisphere. Rasmussen's Syndrome was confirmed by brain biopsy, and a hemispherectomy was performed. This patient demonstrates the rare association of adult-onset EPC with cortical dysplasia, precipitously evolving into Rasmussen's Syndrome.

Cardiac changes in epileptic baboons with high-frequency microburst VNS therapy: A pilot study.

The epileptic baboon provides a natural model of idiopathic generalized epilepsy and sudden unexpected death in epilepsy (SUDEP). We sought to evaluate autonomic differences, including heart rate (HR), heart rate variability (HRV) and corrected QT-duration (QTc) between two epileptic (EB1, EB2) and one control (CB) baboon, and the autonomic effects of high-frequency (HF) microburst Vagal Nerve Stimulation (VNS) Therapy in the epileptic baboons. At baseline, EB2's HR was increased over both EB1 and CB, and EB1's HRV was decreased compared to the others. QTc-intervals were significantly prolonged in both epileptic baboons. EB1 became free of generalized tonic-clonic seizures (GTCS) with VNS therapy, whereas EB2's GTCS were reduced by a third. HR decreased in both epileptic baboons, but while HRV improved in EB1, it decreased in EB2. EB2 succumbed to SUDEP after 9 months. This pilot study demonstrates abnormalities in HR, HRV and QTc-intervals in epileptic baboons. HF VNS Therapy demonstrated different effects on HRV in the two epileptic baboons, which, in addition to persistent GTCS and elevated HR, may have contributed to SUDEP risk in EB2. Future studies are needed to establish normative values for HRV and determine variability of HR, HRV and QTc-intervals in epileptic baboons.

Ictal laughter and crying: Should they be classified as automatisms?

Gelastic seizures (GS) describe ictal laughter and are associated with hypothalamic lesions, as well as other cortical areas. Dacrystic seizures (DS), characterized by ictal crying, also have been reported in hypothalamic lesions and focal epilepsy. We describe a young girl with drug resistant focal dyscognitive seizures associated with gelastic and dacrystic features. However, neither laughter nor crying was correlated with a stereotyped electroencephalographic (EEG) pattern or involvement of a particular brain region. Additionally, based on the variety of epileptogenic foci associated with GS and DS in the literature, laughter and crying appear to represent ictal or peri-ictal automatisms.

Local application of the cannabinoid receptor agonist, WIN 55,212-2, to spinal trigeminal nucleus caudalis differentially affects nociceptive and non-nociceptive neurons.

Cannabinoid receptor agonists produce analgesia for pains of non-cranial origin. However, their effectiveness for craniofacial pains is currently unclear. In the present study, the cannabinoid CB1/CB2 receptor agonist, WIN 55,212-2 (WIN), was bath applied to the brainstem while activity of spinal trigeminal nucleus caudalis (Vc) neurons evoked by transcutaneous electrical stimulation was recorded in isoflurane anesthetized rats. Neurons were characterized using mechanical and electrical stimulation of the face, and were classified as either low-threshold mechanoreceptive (LTM) or wide dynamic range (WDR). LTM neurons responded to light brushing of the receptive field and received only Abeta primary afferent fiber input. WDR neurons showed a graded response to mechanical stimulation, responding maximally to noxious stimuli, and demonstrated both A- and C-fiber evoked activity. In addition, WDR neurons displayed longer latency, C-fiber mediated post-discharge (PDC) activity after repetitive stimulation. Local bath application of 2.0 mg/ml WIN significantly reduced PDC activity (3+/-1% control, P<0.01), C-fiber evoked activity (58+/-9% control, P<0.01), and Abeta evoked activity (57+/-10% control, P<0.01) in WDR neurons. In contrast, LTM Abeta-fiber evoked activity increased after local administration of WIN (204+/-52% control, P<0.01). SR141716A, a CB1 receptor antagonist, prevented the effects of WIN on WDR PDC and LTM Abeta evoked activity. These results indicate that cannabinoid receptor agonists may be effective agents for craniofacial pain. Furthermore, the particular sensitivity of PDC activity, a measure of neuronal hyperexcitability, to cannabinoid receptor agonists may be relevant to the treatment of persistent craniofacial pain.