167 research outputs found
Selective Interruption of Auditory Interhemispheric Cross Talk Impairs Discrimination Learning of Frequency-Modulated Tone Direction But Not Gap Detection and Discrimination
No full textFunctional hemispheric lateralization is a basic principle of brain organization. In the auditory domain, the right auditory cortex (AC) determines the pitch direction of continuous auditory stimuli whereas the left AC discriminates gaps in these stimuli. The involved functional interactions between the two sides, mediated by commissural connections, are poorly understood. Here, we selectively disrupted the interhemispheric cross talk from the left to the right primary AC and vice versa using chromophore-targeted laser-induced apoptosis of the respective projection neurons, which make up 6–17% of all AC neurons in Layers III, V, and VI. Following photolysis, male gerbils were trained in a first experimental set to discriminate between rising and falling frequency-modulated (FM) tone sweeps. The acquisition of the task was significantly delayed in lesioned animals of either lesion direction. However, the final discrimination performance and hit rate was lowest for animals with left-side lesioned commissural neurons, demonstrating that also information from the left AC is relevant for FM direction learning. Photolysis after successful learning did not affect the retrieval of the learned task, indicating that the disruption during learning was not because of a general functional impairment. In a second experimental set, the gerbil's ability to detect and discriminate small silent gaps of varying length within FM sweeps was tested. This ability was also preserved after interhemispheric disruption. Taken together, interhemispheric communication between the left and right AC is important for the acquisition of FM tone direction learning but not for its retrieval and for gap detection and gap duration discrimination. SIGNIFICANCE STATEMENT Hemispheric lateralization of neuronal functions such as speech and music processing in humans are common throughout the brain; however, the involved interhemispheric interactions are ill-defined. Here, we show that the selective photolytic disruption of auditory cortical commissural connections in rodents impairs the acquisition but not retrieval of a frequency-modulated tone direction discrimination task. The final discrimination performance and hit rate was lowest for animals with lesioned left-to-right-side projections; thus, although right auditory cortex is dominant, left auditory cortex is also relevant for learning this task. The detection and discrimination of small gaps within the tone sweeps remain intact, suggesting a pathway for the processing of these temporal structures, which could be independent from the lesioned interhemispheric cross talk
Laser-Induced Apoptosis of Corticothalamic Neurons in Layer VI of Auditory Cortex Impact on Cortical Frequency Processing
No full textCorticofugal projections outnumber subcortical input projections by far. However, the specific role for signal processing of corticofugal feedback is still less well understood in comparisonto the feedforward projection. Here, we lesioned corticothalamic (CT) neurons in layers V and/or VI of the auditory cortex of Mongolian gerbils by laser-induced photolysis to investigate their contribution to cortical activation patterns. We have used laminar current-source density (CSD) recordings of tone-evoked responses and could show that, particularly, lesion of CT neurons in layer VI affected cortical frequency processing. Specifically, we found a decreased gain of best-frequency input in thalamocortical (TC)-recipient input layers that correlated with the relative lesion of layer VI neurons, but not layer V neurons. Using cortical silencing with the GABA a -agonist muscimol and layer-specific intracortical microstimulation (ICMS), we found that direct activation of infragranular layers recruited a local recurrent cortico-thalamo-cortical loop of synaptic input. This recurrent feedback was also only interrupted when lesioning layer VI neurons, but not cells in layer V. Our study thereby shows distinct roles of these two types of CT neurons suggesting a particular impact of CT feedback from layer VI to affect the local feedforward frequency processing in auditory cortex
Secondary auditory cortex and basolateral amygdala interactions are essential during remote fear memory recall: The importance of theta rhythms
No full textBehavioral semantics of learning and crossmodal processing in auditory cortex: The semantic processor concept
No full textSequestration of infected red blood cells and reduced venous efflux precede excessive inflammatory responses in experimental cerebral malaria
No full textCerebral malaria (CM) is a complex neurological complication of severe malaria caused by Plasmodium falciparum. Sequestration of infected red blood cells to the brain vasculature and excessive inflammatory responses in the brain are the key features of CM pathogenesis. Recent imaging studies have established edema development with rise in intracranial pressure as an indicator of fatal CM outcome. However, the link between sequestration of infected red blood cells, excessive inflammation and edema development remains elusive till date. In the present study, in vivo neuroimaging techniques, SPECT/CT and MRI, followed by immunohistochemistry stainings and quantitative reverse transcription-PCR measurements were performed on the mouse model of experimental cerebral malaria (ECM) investigating the rapid progression of the disease starting from an early stage. Sequestration of infected red blood cells, especially in the regions of large draining veins, was observed as the primary event of ECM pathogenesis, present already at a neurologically asymptomatic stage. Reduction of cerebral venous efflux and impaired perfusion in the territories of large draining veins and sinuses ensued, also from the early stage, which worsened with disease progression. In comparison, activation of astrocytes, microglia, endothelial cells and accumulation of leukocytes like CD8+ T cells were observed mostly at a later stage in the neurologically sick mice. Simultaneously, a pro-inflammatory storm of cytokines and chemokines could be detected at this late phase of ECM. Also, a disturbance in rostral migratory stream was observed, from an early stage, which could lead to an impairment in neurogenesis. Severe bilateral edema developed in the white matter tracts of the fatally sick mice. Collectively, the present study suggests direct effect of infected RBC sequestration on the spatiotemporal patterns of edema development by venous efflux reduction while excessive inflammation appears at a later stag
Euchondrus adwani Eike Neubert & Zuhair Amr 2016, n. sp.
No full textEuchondrus adwani n. sp. (Figure 1) Material: Holotype NMBE 539263; paratype NMBE 539264 /1. Type locality: Syria, surrounding of the monastery of Deir Moussa, 34.0219°N 36.8423°E, 1300 m a.s.l., 11.iii. 2010, leg. Adwan Shehab. *Corresponding author. Email: [email protected] © 2016 Taylor & Francis Measurements (holotype): Height = 11.04 mm; diameter = 4.13 mm; peristome height = 4.03 mm; peristome diameter = 2.97 mm; number of whorls = 8. Diagnosis. Euchondrus adwani n. sp. differs from the widespread E. septemdentatus by its conical shell (broadly oval in E. septemdentatus), its flat suture and teleoconch whorls (suture deeper, whorls much more rounded in E. septemdentatus), the heavy palatal labial callus (weaker in E. septemdentatus), the bar-like subangularis (weaker in E. septemdentatus), and the keeled last whorl (rounded in E. septemdentatus). Description: Shell solid, dextral, cylindrical, upper part cylindro-conical in outline; shell pale brownish to horny yellow coloured; 8 rather flat-sided teleoconch whorls, suture flat with a distinct white sutural thread; teleoconch smooth, glossy, last whorl with fine, straight and irregularly spaced striae; aperture subtriangular, peristome strongly thickened by a labial callus, moderately reflected, with a rich dentition (description clockwise): palatum with a small suturalis followed by a conical palatalis superior and a broad infrapalatalis with the latter two denticles placed on a thick callus; columellar side with a basalis and a straight columellaris; parietum with a strong and long parietalis, bordered by a small spiralis, subangularis large, bar-like, left side of the parietum with another small denticle at the attachment site of the peristome; last teleoconch whorl dorsally compressed forming a distinct blunt ridge (arrows); umbilicus slit-like open, periomphalum large, dish-like. Remarks: This species shows some superficial similarities with E. desertorum Rochanaburananda in Forcart, 1981 (Figure 2), which is endemic to the Negev Desert (Heller, 2009). Both species have a straight conical shell, but E. desertorum is considerably larger than E. adwani n. sp. and its aperture is rounded and not subtriangular. It also differs in the formation of the dentition: in E. desertorum, the infrapalatalis is bifid (simple in E. adwani), the spiralis is large and connected to the parietalis (small and disconnected in E. adwani), and the subangularis is weaker (very strong in E. adwani). The last whorl of E. adwani displays a distinct keel with an enlarged periomphalum, while in E. desertorum the dorsum is rounded, and the periomphalum is much smaller. Etymology: This species is named in honour of Dr. Adwan Shawabi, who was a keen collector of molluscs from Syria, and a personal friend, and who was killed in February 2015 in the Syrian civil war (Amr, 2015).Published as part of Eike Neubert & Zuhair Amr, 2016, On a new species of Euchondrus Boettger, 1883 from Syria (Pulmonata: Enidae), pp. 58-60 in Zoology in the Middle East 62 on pages 58-60, DOI: 10.1080/09397140.2015.1132564, http://zenodo.org/record/88703
Der Einfluss superparamagnetischer Nanopartikel auf die neuronale Regeneration
No full textDas zentrale Nervensystem (ZNS) ist ein stark spezialisiertes Organ mit hochgradig differenziertem neuronalem Gewebe aus schlecht regenerationsfähigen, postmitotischen Zellen. Die Anzahl vorhandener Stammzellen ist gering und auf den Gyrus dentatus sowie die subventrikuläre Zone zur Regeneration von olfaktorischen Neuronen beschränkt (Bjorklund & Lindvall, 2000). Die traumatische Rückenmarkläsion ist, wie andere Läsionen im ZNS, gekennzeichnet durch einen primären, sofortigen, irreversiblen Verlust von Zellen und Nervenfasern im Bereich der Läsionszone. Stunden später kommt es zu einem sekundär auftretenden Zelltod umliegender Areale, welcher den primären Zelltod bei weitem übertrifft und für den zu erwartenden Funktionsverlust viel schwerwiegender ist (Bechmann et al., 2005). Wir wissen, dass neuronales Wachstum und Regeneration ein komplexes Zusammenspiel von intra- und extrazellulären Molekülen wie Wachstumsfaktoren, Neurotransmittern und extrazellulärer Matrix (ECM) Proteine benötigt (O ́Donnell et al., 2009). Obwohl unser Wissen bezüglich der zugrunde liegenden Mechanismen ständig zunimmt, gibt es immer noch keine effektive Therapie nach einer Querschnittslähmung (Filli & Schwab, 2012), weder um durchtrennte Bahnen wieder herzustellen, die entstehende Narbe zu hemmen oder den sekundär auftretenden Schaden zu minimieren, welcher prinzipiell reversibel sein sollte (Peng et al., 2009). Ein durchtrennter kortikospinaler Trakt im Rückenmark (RM) resultiert in der Querschnittlähmung des Patienten mit all seinen psychologischen, ökonomischen und lebensverändernden Folgen
A note on Belyi's theorem for Klein surfaces
No full textSingerman and the first named author have recently developed a real Belyi thoery, leaving open a particular case in the proof of Belyi's theorem for Klein surfaces. We answer their question affirmatively by a descent argument which turns out to extend to a much more general context
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