Auditory Thalamocortical Transmission Is Reliable and Temporally Precise

Abstract

We have used the auditory thalamocortical slice to characterize thalamocortical transmission in primary auditory cortex (ACx) of the juvenile mouse. "Minimal" stimulation was used to activate medial geniculate neurons during whole cell recordings from regular-spiking (RS cells; mostly pyramidal) and fast-spiking (FS, putative inhibitory) neurons in ACx layers 3 and 4. Excitatory postsynaptic potentials (EPSPs) were considered monosynaptic (thalamocortical) if they met three criteria: low onset latency variability (jitter), little change in latency with increased stimulus intensity, and little change in latency during a high-frequency tetanus. Thalamocortical EPSPs were reliable (probability of postsynaptic responses to stimulation was approximately 1.0) as well as temporally precise (low jitter). Both RS and FS neurons received thalamocortical input, but EPSPs in FS cells had faster rise times, shorter latencies to peak amplitude, and shorter durations than EPSPs in RS cells. Thalamocortical EPSPs depressed during repetitive stimulation at rates (2-300 Hz) consistent with thalamic spike rates in vivo, but at stimulation rates > or = 40 Hz, EPSPs also summed to activate N-methyl-D-aspartate receptors and trigger long-lasting polysynaptic activity. We conclude that thalamic inputs to excitatory and inhibitory neurons in ACx activate reliable and temporally precise monosynaptic EPSPs that in vivo may contribute to the precise timing of acoustic-evoked responses.

A Spike-Timing Code for Discriminating Conspecific Vocalizations in the Thalamocortical System of Anesthetized and Awake Guinea Pigs

“…First, in vitro studies indicate that cortical neurons display temporal regularities during injection of fluctuating currents in the soma (Mainen and Sejnowski, 1995;Fellous et al, 2001), suggesting that intrinsic membrane properties support high temporal fidelity. Second, recent studies suggest that auditory thalamocortical transmission is also temporally precise: the monosynaptic EPSPs triggered by thalamic stimulation in regular spiking and fast spiking cells from layers 3/4 can follow at rates of up to 40 Hz (Rose and Metherate, 2005). Third, the precise spiking pattern of ACx cells is often viewed as resulting from the precise temporal integration of excitatory and inhibitory potentials.…”

Transformation of Temporal Properties between Auditory Midbrain and Cortex in the Awake Mongolian Gerbil

“…Indeed, certain thalamically activated neurons in layer V of rat auditory cortical slices reportedly exhibit fast inhibition Smith, 2000, 2003). Additionally, fast-spiking (presumably inhibitory) interneurons in thalamorecipient layers III/IV of mouse auditory cortex exhibit faster EPSPs than regular-spiking (presumed excitatory) neurons in the same layers (Rose and Metherate, 2005). These interneurons are well positioned to block onset responses of cells to which they project.…”

“…Indeed, there are reports that the precision of first-spike timing in AI can actually improve on the auditory nerve (Heil and Irvine, 1997). It has been proposed that such accuracy may be achieved in part by a secure and temporally precise synapse between the medial geniculate body and AI (Rose and Metherate, 2005). Additionally, precisely timed excitatory and inhibitory conductances that are cotuned for frequency and intensity can account for precise, transient responses in AI .…”

Modelo in vitro para el estudio del papel de la unión mesopontina en la generación del sueño de movimientos oculares rápidos y la vigilia

“…La neurona identificada electrofisiológi-camente como de tipo LTS, fue fotografiada (inserto arriba derecha, calibración 20 µm) y reconstruida en el dibujo de cámara clara (inserto abajo derecha, calibración 20 µm). (47) adaptados a nuestro diseño experimental: reducida variabilidad de la latencia con intensidades de estimulación submáximas ≤ 1 ms, modificación menor a 1ms con incrementos de la intensidad de estimulación y estabilidad de la latencia para frecuencias de estimulación relativamente elevadas (15Hz) (48) (49) . En conjunto, las neuronas registradas presentaron Ren de 292.17 ± 22.41 MOhm y en su mayoría (42 en 45) no mostraron descarga espontánea de potenciales de acción.…”

“…5). La estabilidad de la latencia de las respuestas en diversas condiciones de estimulación (47) conjuntamente con la obtención de IPSCs aislados farmacológicamente por bloqueo de la transmisión glutamatérgica, sugieren que la inervación no colinérgica del PnO originada en el LDT-PPT ipsilateral, involucra contactos sináp-ticos directos sobre neuronas del PnO. En virtud de la sensibilidad de las respuestas provocadas a los bloqueantes utilizados y coherentemente con hallazgos previos en la FRP de la rata (25) (26) , los EPSCs involucran la activación de receptores ionotrópicos de glutamato (NMDA y AMPA) en tanto que los IPSCs, receptores de tipo GABAA.…”