Corticothalamic Pathways in Auditory Processing: Recent Advances and Insights From Other Sensory Systems

The corticothalamic (CT) pathways emanate from either Layer 5 (L5) or 6 (L6) of the neocortex and largely outnumber the ascending, thalamocortical pathways. The CT pathways provide the anatomical foundations for an intricate, bidirectional communication between thalamus and cortex. They act as dynamic circuits of information transfer with the ability to modulate or even drive the response properties of target neurons at each synaptic node of the circuit. L6 CT feedback pathways enable the cortex to shape the nature of its driving inputs, by directly modulating the sensory message arriving at the thalamus. L5 CT pathways can drive the postsynaptic neurons and initiate a transthalamic corticocortical circuit by which cortical areas communicate with each other. For this reason, L5 CT pathways place the thalamus at the heart of information transfer through the cortical hierarchy. Recent evidence goes even further to suggest that the thalamus via CT pathways regulates functional connectivity within and across cortical regions, and might be engaged in cognition, behavior, and perceptual inference. As descending pathways that enable reciprocal and context-dependent communication between thalamus and cortex, we venture that CT projections are particularly interesting in the context of hierarchical perceptual inference formulations such as those contemplated in predictive processing schemes, which so far heavily rely on cortical implementations. We discuss recent proposals suggesting that the thalamus, and particularly higher order thalamus via transthalamic pathways, could coordinate and contextualize hierarchical inference in cortical hierarchies. We will explore these ideas with a focus on the auditory system.This work was supported by the Spanish Agencia Estatal de Investigación [(AEI), PID2019-104570RB- I00] and Junta de Castilla y León, (SA252P20) to MSM. FMA held a postdoctoral fellowship from the University of Salamanca (Contratos Postdoctorales, USAL, Programa II)

Stimulus-Specific Adaptation in the Auditory Thalamus of the Anesthetized Rat

The specific adaptation of neuronal responses to a repeated stimulus (Stimulus-specific adaptation, SSA), which does not fully generalize to other stimuli, provides a mechanism for emphasizing rare and potentially interesting sensory events. Previous studies have demonstrated that neurons in the auditory cortex and inferior colliculus show SSA. However, the contribution of the medial geniculate body (MGB) and its main subdivisions to SSA and detection of rare sounds remains poorly characterized. We recorded from single neurons in the MGB of anaesthetized rats while presenting a sequence composed of a rare tone presented in the context of a common tone (oddball sequences). We demonstrate that a significant percentage of neurons in MGB adapt in a stimulus-specific manner. Neurons in the medial and dorsal subdivisions showed the strongest SSA, linking this property to the non-lemniscal pathway. Some neurons in the non-lemniscal regions showed strong SSA even under extreme testing conditions (e.g., a frequency interval of 0.14 octaves combined with a stimulus onset asynchrony of 2000 ms). Some of these neurons were able to discriminate between two very close frequencies (frequency interval of 0.057 octaves), revealing evidence of hyperacuity in neurons at a subcortical level. Thus, SSA is expressed strongly in the rat auditory thalamus and contribute significantly to auditory change detection

GABAA-Mediated Inhibition Modulates Stimulus-Specific Adaptation in the Inferior Colliculus

The ability to detect novel sounds in a complex acoustic context is crucial for survival. Neurons from midbrain through cortical levels adapt to repetitive stimuli, while maintaining responsiveness to rare stimuli, a phenomenon called stimulus-specific adaptation (SSA). The site of origin and mechanism of SSA are currently unknown. We used microiontophoretic application of gabazine to examine the role of GABAA-mediated inhibition in SSA in the inferior colliculus, the midbrain center for auditory processing. We found that gabazine slowed down the process of adaptation to high probability stimuli but did not abolish it, with response magnitude and latency still depending on the probability of the stimulus. Blocking GABAA receptors increased the firing rate to high and low probability stimuli, but did not completely equalize the responses. Together, these findings suggest that GABAA-mediated inhibition acts as a gain control mechanism that enhances SSA by modifying the responsiveness of the neuron

Los mayores y las nuevas tecnologías de la comunicación

[Resumen] Fundamentos: En una sociedad envejecida es necesario establecer nuevas alternativas que de alguna manera traten de satisfacer las necesidades de las personas mayores, a la vez que incrementen su calidad de vida percibida. En este sentido, las nuevas tecnologías, como la informática, se han convertido en una herramienta básica de nuestra sociedad, de la que los mayores, sin ninguna duda, podrán beneficiarse. El objetivo del presente trabajo es conocer la opinión de los mayores acerca de temas relacionados con la informática e Internet, así como su capacidad de acceso a las nuevas tecnologías y los conocimientos con los que cuentan. Métodos: Se realiza una entrevista estandarizada, de diseño propio, a una muestra de 105 personas mayores con una edad media de 73 años, residentes en la ciudad de A Coruña. Resultados: De los resultados obtenidos se constata que aunque la mayoría de las personas mayores no cuenta con ordenador personal ni ha trabajado con aplicaciones informáticas, les gustaría aprender más sobre este campo. Además, cuando se conectan a Internet lo hacen desde centros sociales y/o educativos, no encontrando excesivos problemas en su manejo y navegación. Conclusiones: Es necesario fomentar el uso de la informática por parte de los mayores, ya que en un futuro puede constituir una herramienta imprescindible en la intervención sobre problemas inherentes al envejecimiento como son el aislamiento o la soledad entre otros.[Abstract] new alternatives, that somehow try to satisfy the needs of elderly people and that at the same time increase their quality of life. On this sense, the new technologies, such as computer science, have become a basic tool of our society, and the elderly, without no doubt will be able to benefit from it. The objective of the present work is to know what the elderly think about themes related to computer science and internet, as well as their capacity of accessing to new technologies, and the knowledge that they have about them. Methods: A standarized interview has been made, it´s self designed, to a sample of 105 elderly people living in the city of A Coruña. Results: Although most elderly people don´t have a personal computer neither have worked with a computer application, would like to learn more about this field. When they are connected to internet they do it from social and/or educative centres, not having great problems neither in its handling or navigation. Conclusions: It´s necessary to promote the use of computer science on the elderly people, since in a future it can constitute an essential tool in the intervention on inherent problems to aging such as isolation or loneliness among others

Caza, domesticación y pastoreo de camélidos en la Puna argentina

El proceso de domesticación de los camélidos y el origen y estabilización de la estrategia pastoril ha sido un tema de crucial importancia en los estudios arqueológicos andinos. El objetivo de este trabajo es el análisis de este tema en Susques (Puna Argentina). Se plantea la existencia de un proceso de domesticación independiente al de los Andes Centrales y un desarrollo posterior del pastoreo. Nuestra investigación se basó en la delimitación de un sector de 1500 km2 donde se localizaron 38 sitios arqueológicos de los cuales 14 forman parte de la muestra analizada aquí y abarcan un rango temporal desde los 3550 años A. P. hasta los 260 años A.P. Distintas líneas de evidencia han permitido establecer la presencia de animales domesticados (Lama glama) desde el momento más temprano, intensificándose su presencia a lo largo del tiempo como lo evidencian no sólo los restos óseos, sino también las manufacturas textiles. La estabilización de la estrategia pastoril se registra hacia los 2040A. P. Se destaca la importancia de la caza de camélidos silvestres y el consumo de roedores que determinan la existencia de un sistema pastoril-cazador hasta momentos tardío.Sociedad Argentina de Antropologí

Respuesta

En primer lugar queremos agradecer a Willie Mengoni y Penny Dransart los comentarios a nuestro trabajo que lo han enriquecido de una manera enorme. Los mismos subrayan varios temas de interés general tanto teóricos como metodológicos y algunas cuestiones puntuales referidas, más que nada, a aspectos metodológicos. Comenzaremos por los puntos generales. (Párrafo extraído del texto a modo de resumen)Sociedad Argentina de Antropologí

Caza, domesticación y pastoreo de camélidos en la Puna argentina

El proceso de domesticación de los camélidos y el origen y estabilización de la estrategia pastoril ha sido un tema de crucial importancia en los estudios arqueológicos andinos. El objetivo de este trabajo es el análisis de este tema en Susques (Puna Argentina). Se plantea la existencia de un proceso de domesticación independiente al de los Andes Centrales y un desarrollo posterior del pastoreo. Nuestra investigación se basó en la delimitación de un sector de 1500 km2 donde se localizaron 38 sitios arqueológicos de los cuales 14 forman parte de la muestra analizada aquí y abarcan un rango temporal desde los 3550 años A. P. hasta los 260 años A.P. Distintas líneas de evidencia han permitido establecer la presencia de animales domesticados (Lama glama) desde el momento más temprano, intensificándose su presencia a lo largo del tiempo como lo evidencian no sólo los restos óseos, sino también las manufacturas textiles. La estabilización de la estrategia pastoril se registra hacia los 2040A. P. Se destaca la importancia de la caza de camélidos silvestres y el consumo de roedores que determinan la existencia de un sistema pastoril-cazador hasta momentos tardío.Sociedad Argentina de Antropologí

Fast Detection of Unexpected Sound Intensity Decrements as Revealed by Human Evoked Potentials

The detection of deviant sounds is a crucial function of the auditory system and is reflected by the automatically elicited mismatch negativity (MMN), an auditory evoked potential at 100 to 250 ms from stimulus onset. It has recently been shown that rarely occurring frequency and location deviants in an oddball paradigm trigger a more negative response than standard sounds at very early latencies in the middle latency response of the human auditory evoked potential. This fast and early ability of the auditory system is corroborated by the finding of neurons in the animal auditory cortex and subcortical structures, which restore their adapted responsiveness to standard sounds, when a rare change in a sound feature occurs. In this study, we investigated whether the detection of intensity deviants is also reflected at shorter latencies than those of the MMN. Auditory evoked potentials in response to click sounds were analyzed regarding the auditory brain stem response, the middle latency response (MLR) and the MMN. Rare stimuli with a lower intensity level than standard stimuli elicited (in addition to an MMN) a more negative potential in the MLR at the transition from the Na to the Pa component at circa 24 ms from stimulus onset. This finding, together with the studies about frequency and location changes, suggests that the early automatic detection of deviant sounds in an oddball paradigm is a general property of the auditory system

Structure of the Afferent Terminals in Terminal Ganglion of a Cricket and Persistent Homology

We use topological data analysis to investigate the three dimensional spatial structure of the locus of afferent neuron terminals in crickets Acheta domesticus. Each afferent neuron innervates a filiform hair positioned on a cercus: a protruding appendage at the rear of the animal. The hairs transduce air motion to the neuron signal that is used by a cricket to respond to the environment. We stratify the hairs (and the corresponding afferent terminals) into classes depending on hair length, along with position. Our analysis uncovers significant structure in the relative position of these terminal classes and suggests the functional relevance of this structure. Our method is very robust to the presence of significant experimental and developmental noise. It can be used to analyze a wide range of other point cloud data sets