The temporal pole: From anatomy to function—A literature appraisal

International audienceHistorically, the anterior part of the temporal lobe was labelled as a unique structure named Brain Area 38 by Brodmann or Temporopolar Area TG by Von Economo, but its functions were unknown at that time. Later on, a few studies proposed to divide the temporal pole in several different subparts, based on distinct cytoarchitectural structure or connectivity patterns, while a still growing number of studies have associated the temporal pole with many cognitive functions. In this review, we provide an overview of the temporal pole anatomical and histological structure and its various functions. We performed a literature review of articles published prior to September 30, 2020 that included 112 articles. The temporal pole has thereby been associated with several high-level cognitive processes: visual processing for complex objects and face recognition, autobiographic memory, naming and word-object labelling, semantic processing in all modalities, and socio-emotional processing, as demonstrated in healthy subjects and in patients with neurological or psychiatric diseases, especially in the field of neurodegenerative disorders. A good knowledge of those functions and the symptoms associated with temporal pole lesions or dysfunctions is helpful to identify these diseases, whose diagnosis may otherwise be difficult

Ketamine reduces temporal expectation in the rhesus monkey.

Ketamine, a well-known general dissociative anesthetic agent that is a non-competitive antagonist of the N-methyl-D-aspartate receptor, perturbs the perception of elapsed time and the expectation of upcoming events. The objective of this study was to determine the influence of ketamine on temporal expectation in the rhesus monkey. Two rhesus monkeys were trained to make a saccade between a central warning stimulus and an eccentric visual target that served as imperative stimulus. The delay between the warning and the imperative stimulus could take one of four different values randomly with the same probability (variable foreperiod paradigm). During experimental sessions, a subanesthetic low dose of ketamine (0.25-0.35 mg/kg) was injected i.m. and the influence of the drug on movement latency was measured. We found that in the control conditions, saccadic latencies strongly decreased with elapsed time before the appearance of the visual target showing that temporal expectation built up during the delay period between the warning and the imperative stimulus. However, after ketamine injection, temporal expectation was significantly reduced in both subjects. In addition, ketamine also increased average movement latency but this effect could be dissociated from the reduction of temporal expectation. In conclusion, a subanesthetic dose of ketamine could have two independent effects: increasing reaction time and decreasing temporal expectation. This alteration of temporal expectation could explain cognitive deficits observed during ketamine use

Sex-related variability of white matter tracts in the whole HCP cohort

International audienceBehavioral studies have shown that men and women have many similarities, but also some specificities (1–3). Whether these are due to biological or social differences, or a combination of both, remains unclear. Many studies have examined sex differences in cortical gray matter, but few have done so for white matter tracts. We therefore conducted a sex comparison of all deep white matter tracts in a large cohort of 1065 subjects

Hallucinatory choking from slow wave sleep Choking during sleep: can it be expression of arousal disorder?

International audienceBackgroundChoking during sleep may be caused by various respiratory and non-respiratory problems.ObjectiveWe aimed at documenting a new, rare cause of hallucinatory choking.MethodsWe documented the clinical and video-polysomnographic features of 11 adult patients referred for swallowing and choking during sleep. We conducted a systematic search for similar sensations in 68 consecutive adult patients with sleepwalking/sleep terrors and in 37 patients with obstructive sleep apnea.Results.The 11 patients with sleep-related swallowing and choking were all current or former sleepwalkers. The symptoms occurred during the first third of the night. Patients consistently reported the frequent hallucinatory feeling of swallowing an unusual object (ring, nails, pebble, chewing gum, spoon, fork, electrical cables, lizard tail, needles, brush, computer, gas container) that blocked the upper airways during sleep, followed by attempts to unblock them by spitting or swallowing water. When monitored, the choking sensations were not stereotypic, and occurred exclusively during arousals from N3 sleep, despite normal airway patency and absence of epileptic activity. The patients demonstrated simultaneous intense adrenergic stimulation and emotional distress. Of the 68 sleepwalkers, 13% had occasional choking sensations and 4% once inhaled a fictitious object. In the sleep apnea group, choking was never the motive of referral, but 38% of patients had occasional choking sensations, and 5% once inhaled something fictitious.ConclusionWhile insular seizure could also be discussed, these results suggest that sleep-related swallowing and choking syndrome may be in some cases a rare, specialized variant of the arousal disorders

Temporal pole epilepsy surgery—Sparing the hippocampus

International audienceTemporal pole epilepsy (TPE) is a poorly known and difficult to individualize subtype of temporal lobe epilepsy. Consequently, in drug‐resistant TPE, there is still a debate on the need for a large surgical removal of the temporal pole and mesial temporal structures or a limited resection of the temporal pole. We reviewed all patients who underwent presurgical evaluation for drug‐resistant epilepsy over a 17‐year period, and report here 19 patients with proven drug‐resistant temporal pole epilepsy who underwent a selective temporal pole resection with respect to mesial structures. Most (15) TPE patients exhibited seizures resembling mesiotemporal seizures, whereas the others exhibited nocturnal hyperkinetic seizures or an association of both seizure types. MRI revealed a temporal pole lesion in 58% of patients. Long‐term postoperative outcome after a conservative surgery was excellent: 63% of patients were seizure‐free (International League Against Epilepsy [ILAE] 1) at 1‐year postsurgery and 78% at 5 years. These results show that TPE has no specific electroclinical features but is a distinct type of temporal lobe epilepsy allowing a conservative surgery. Respecting the mesiotemporal structures is a valid surgical approach for drug‐resistant temporal pole epilepsy

Toxicity to RAW264.7 Macrophages of Silica Nanoparticles and the E551 Food Additive, in Combination with Genotoxic Agents

International audienceSynthetic amorphous silica (SAS) is used in a plethora of applications and included in many daily products to which humans are exposed via inhalation, ingestion, or skin contact. This poses the question of their potential toxicity, particularly towards macrophages, which show specific sensitivity to this material. SAS represents an ideal candidate for the adsorption of environmental contaminants due to its large surface area and could consequently modulate their toxicity. In this study, we assessed the toxicity towards macrophages and intestinal epithelial cells of three SAS particles, either isolated SiO 2 nanoparticles (LS30) or SiO 2 particles composed of agglomerated-aggregates of fused primary particles, either food-grade (E551) or non-food-grade (Fumed silica). These particles were applied to cells either alone or in combination with genotoxic co-contaminants, i.e., benzo[a]pyrene (B[a]P) and methane methylsulfonate (MMS). We show that macrophages are much more sensitive to these toxic agents than a non-differenciated co-culture of Caco-2 and HT29-MTX cells, used here as a model of intestinal epithelium. Co-exposure to SiO 2 and MMS causes DNA damage in a synergistic way, which is not explained by the modulation of DNA repair protein mRNA expression. Together, this suggests that SiO 2 particles could adsorb genotoxic agents on their surface and, consequently, increase their DNA damaging potential

Sleep-Related Declarative Memory Consolidation and Verbal Replay during Sleep Talking in Patients with REM Sleep Behavior Disorder

<div><p>Objective</p><p>To determine if sleep talkers with REM sleep behavior disorder (RBD) would utter during REM sleep sentences learned before sleep, and to evaluate their verbal memory consolidation during sleep. </p> <p>Methods</p><p>Eighteen patients with RBD and 10 controls performed two verbal memory tasks (16 words from the Free and Cued Selective Reminding Test and a 220-263 word long modified Story Recall Test) in the evening, followed by nocturnal video-polysomnography and morning recall (night-time consolidation). In 9 patients with RBD, daytime consolidation (morning learning/recall, evening recall) was also evaluated with the modified Story Recall Test in a cross-over order. Two RBD patients with dementia were studied separately. Sleep talking was recorded using video-polysomnography, and the utterances were compared to the studied texts by two external judges. </p> <p>Results</p><p>Sleep-related verbal memory consolidation was maintained in patients with RBD (+24±36% words) as in controls (+9±18%, <i>p</i>=0.3). The two demented patients with RBD also exhibited excellent nighttime consolidation. The post-sleep performance was unrelated to the sleep measures (including continuity, stages, fragmentation and apnea-hypopnea index). Daytime consolidation (-9±19%) was worse than night-time consolidation (+29±45%, <i>p</i>=0.03) in the subgroup of 9 patients with RBD. Eleven patients with RBD spoke during REM sleep and pronounced a median of 20 words, which represented 0.0003% of sleep with spoken language. A single patient uttered a sentence that was judged to be semantically (but not literally) related to the text learned before sleep. </p> <p>Conclusion</p><p>Verbal declarative memory normally consolidates during sleep in patients with RBD. The incorporation of learned material within REM sleep-associated sleep talking in one patient (unbeknownst to himself) at the semantic level suggests a replay at a highly cognitive creative level. </p> </div

A mesoscale ex vivo macaque white matter atlas using high-performance computing global tractography

International audienceWhile global tractography offers enhanced accuracy and reliability compared to standard streamline tractography methods[1], it comes at the cost of substantial computational resources in terms of both time and memory. This approach indeed simultaneously generates and optimizes the trajectories of virtual axonal white matter (WM) fibers (represented as connected spin-glasses), considering the local orientation distribution derived from diffusion MRI (dMRI) data. Leveraging this method on extensive datasets poses significant challenges, leading to the creation of ExaTract[2], a novel High-Performance Computing (HPC) global tractography approach. In this study, we demonstrate the ability of ExaTract to reconstruct numerous brain connections and robustly identify deep WM bundles from a very high resolution (250μm) dataset in a reasonable time

A mesoscale ex vivo macaque white matter atlas using high-performance computing global tractography

International audienceWhile global tractography offers enhanced accuracy and reliability compared to standard streamline tractography methods[1], it comes at the cost of substantial computational resources in terms of both time and memory. This approach indeed simultaneously generates and optimizes the trajectories of virtual axonal white matter (WM) fibers (represented as connected spin-glasses), considering the local orientation distribution derived from diffusion MRI (dMRI) data. Leveraging this method on extensive datasets poses significant challenges, leading to the creation of ExaTract[2], a novel High-Performance Computing (HPC) global tractography approach. In this study, we demonstrate the ability of ExaTract to reconstruct numerous brain connections and robustly identify deep WM bundles from a very high resolution (250μm) dataset in a reasonable time