Papers by Victoria M Bajo
Synapse, 2000
Intracellular recordings in slice preparations of the basolateral amygdala were used to test whic... more Intracellular recordings in slice preparations of the basolateral amygdala were used to test which excitatory amino acid receptors mediate the excitatory postsynaptic potentials due to stimulation of the external capsule. These recordings were also used to examine the action of muscarinic agonists on the evoked excitatory potentials. Intracellular recordings from amygdaloid pyramidal neurons revealed that carbachol (2-20 microM) suppressed, in a dose-dependent manner, excitatory postsynaptic responses evoked by stimulation of the external capsule (EC). This effect was blocked by atropine. The estimated effective concentration to produce half-maximal response (EC(50)) was 6.2 microM. Synaptic suppression was observed with no changes in the input resistance of the recorded cells, suggesting a presynaptic mechanism. In addition, the results obtained using the paired-pulse protocol provided additional support for a presynaptic action of carbachol. To identify which subtype of cholinergic receptors were involved in the suppression of the EPSP, four partially selective muscarinic receptor antagonists were used at different concentrations: pirenzepine, a compound with a similar high affinity for muscarinic M1 and M4 receptors; gallamine, a noncompetitive antagonist for M2; methoctramine, an antagonist for M2 and M4; and 4-diphenylacetoxy-N-methylpiperidine, a compound with similar high affinity for muscarinic receptors M1 and M3. None of them independently antagonized the suppressive effect of carbachol on the evoked EPSP completely, suggesting that more than one muscarinic receptor subtype is involved in the effect. These experiments provide evidence that in the amygdala muscarinic agonists block the excitatory synaptic response, mediated by glutamic acid, by acting on several types of presynaptic receptors.
publishes original articles on the function of the nervous system. It is published 12
Springer eBooks, 1997
A unique feature of the auditory brainstem is the divergent/convergent nature of the path- ways f... more A unique feature of the auditory brainstem is the divergent/convergent nature of the path- ways from the auditory nerve to the inferior colliculus (IC, reviewed in Irvine, 1992). Some of the projections from the cochlear nucleus complex to the IC are direct while others are indirect via the superior olivary complex and the nuclei of the lateral lemniscus (NLL). In these nuclei, sig- nificant monaural and binaural information are extracted from the auditory signal.
Frontiers in Neuroscience, Feb 1, 2023
King AJ and Nodal FR (2023) Persistence and generalization of adaptive changes in auditory locali... more King AJ and Nodal FR (2023) Persistence and generalization of adaptive changes in auditory localization behavior following unilateral conductive hearing loss.
Frontiers in Neuroscience, Aug 19, 2021
Sound information is transmitted from the ear to central auditory stations of the brain via sever... more Sound information is transmitted from the ear to central auditory stations of the brain via several nuclei. In addition to these ascending pathways there exist descending projections that can influence the information processing at each of these nuclei. A major descending pathway in the auditory system is the feedback projection from layer VI of the primary auditory cortex (A1) to the ventral division of medial geniculate body (MGBv) in the thalamus. The corticothalamic axons have small glutamatergic terminals that can modulate thalamic processing and thalamocortical information transmission. Corticothalamic neurons also provide input to GABAergic neurons of the thalamic reticular nucleus (TRN) that receives collaterals from the ascending thalamic axons. The balance of corticothalamic and TRN inputs has been shown to refine frequency tuning, firing patterns, and gating of MGBv neurons. Therefore, the thalamus is not merely a relay stage in the chain of auditory nuclei but does participate in complex aspects of sound processing that include top-down modulations. In this review, we aim (i) to examine how lemniscal corticothalamic feedback modulates responses in MGBv neurons, and (ii) to explore how the feedback contributes to auditory scene analysis, particularly on frequency and harmonic perception. Finally, we will discuss potential implications of the role of corticothalamic feedback in music and speech perception, where precise spectral and temporal processing is essential.
Frontiers in Neuroscience, 2021
For decades, the corticofugal descending projections have been anatomically well described but th... more For decades, the corticofugal descending projections have been anatomically well described but their functional role remains a puzzling question. In this review, we will first describe the contributions of neuronal networks in representing communication sounds in various types of degraded acoustic conditions from the cochlear nucleus to the primary and secondary auditory cortex. In such situations, the discrimination abilities of collicular and thalamic neurons are clearly better than those of cortical neurons although the latter remain very little affected by degraded acoustic conditions. Second, we will report the functional effects resulting from activating or inactivating corticofugal projections on functional properties of subcortical neurons. In general, modest effects have been observed in anesthetized and in awake, passively listening, animals. In contrast, in behavioral tasks including challenging conditions, behavioral performance was severely reduced by removing or transi...
Hearing Research, 1999
Previous studies performed in anesthetized animals have shown differences between the acoustic re... more Previous studies performed in anesthetized animals have shown differences between the acoustic responses of neurons recorded from the different divisions of the medial geniculate body (MGB). This study aimed at determining whether or not such differences are also expressed when neurons are recorded from awake animals. The auditory responses of 130 neurons of the auditory thalamus were determined in awake, restrained guinea pigs while the state of vigilance of the animals was continuously monitored. There were significantly more`on' phasic evoked responses and significantly fewer`non-responsive' or`labile' cells in the ventral division of the MGB (MGv) than in the other divisions. The response latencies and the variability of the latencies were smaller in the MGv than in the other divisions. The tuning of the neurons obtained from MGv and from the lateral part of the posterior complex were significantly sharper than those coming from the dorsal division of the MGB and the medial division. The mean threshold and the percentage of monotonic vs. non-monotonic intensity functions were not different in the subdivisions of the auditory thalamus. When compared with previous studies, the quantifications of the acoustic responses obtained in the present study gave values that differed from those reported under deep anesthesia, but were close to those reported under light anesthesia. Lastly, even if none of the physiological characteristic makes it possible, by itself, to determine the locus of recordings in the auditory thalamus, we conclude that the physiological characteristics of the evoked responses obtained in MGv differ from those of other divisions.
The non-lemniscal auditory cortex in ferrets: convergence of
Brain Communications
Sensory disconnection from the environment is a hallmark of sleep and is crucial for sleep mainte... more Sensory disconnection from the environment is a hallmark of sleep and is crucial for sleep maintenance. It remains unclear, however, whether internally generated percepts—phantom percepts—may overcome such disconnection and, in turn, how sleep and its effect on sensory processing and brain plasticity may affect the function of the specific neural networks underlying such phenomena. A major hurdle in addressing this relationship is the methodological difficulty to study sensory phantoms, due to their subjective nature and lack of control over the parameters or neural activity underlying that percept. Here, we explore the most prevalent phantom percept, subjective tinnitus—or tinnitus for short—as a model to investigate this. Tinnitus is the permanent perception of a sound with no identifiable corresponding acoustic source. This review offers a novel perspective on the functional interaction between brain activity across the sleep–wake cycle and tinnitus. We discuss characteristic fea...
bioRxiv, 2020
To form a coherent representation of the environment, the brain must integrate information across... more To form a coherent representation of the environment, the brain must integrate information across different senses. Such multisensory convergence is widespread at the level of the cortex, where it is thought to arise primarily from corticocortical connections. Much less is known about the role of subcortical circuits in shaping the multisensory properties of cortical neurons. We show that sound-evoked activity in the mouse auditory cortex is widely suppressed by whisker stimulation. This suppression depends on the primary somatosensory cortex (S1), but surprisingly is implemented through a circuit linking S1 and the auditory thalamocortical system via the auditory midbrain. We also show that an additional, direct pathway exists from S1 to the medial sector of auditory thalamus, which facilitates auditory responses in neurons that do not project to the auditory cortex. The thalamus thus occupies a pivotal role in integrating multisensory signals by somatosensory top-down control of a...
Neural adaptation enables sensory information to be represented optimally in the brain despite la... more Neural adaptation enables sensory information to be represented optimally in the brain despite large fluctuations over time in the statistics of the environment. Auditory contrast gain control represents an important example, which is thought to arise primarily from cortical processing. We find, however, that neurons in both the auditory thalamus and midbrain of mice show robust contrast gain control, and that this is implemented independently of cortical activity. Although neurons at each level exhibit contrast gain control to similar degrees, adaptation time constants become longer at later stages of the processing hierarchy, resulting in progressively more stable representations. We also show that auditory discrimination thresholds in human listeners compensate for changes in contrast, and that the strength of this perceptual adaptation can be predicted from physiological measurements. Contrast adaptation is therefore a robust property of both the subcortical and cortical auditor...
doi: 10.3389/fncir.2013.00029 Patterns of convergence in the central nucleus of the inferior coll... more doi: 10.3389/fncir.2013.00029 Patterns of convergence in the central nucleus of the inferior colliculus of the Mongolian gerbil: organization of inputs from the superior olivary complex in the low frequency representation
doi: 10.3389/fnsys.2014.00188 Descending projections from auditory cortex to excitatory and inhib... more doi: 10.3389/fnsys.2014.00188 Descending projections from auditory cortex to excitatory and inhibitory cells in the nucleus of the brachium of the inferior colliculus
Los nucleos del lemnisco lateral (lln) son los nucleos menos conocidos de la via auditiva. Para c... more Los nucleos del lemnisco lateral (lln) son los nucleos menos conocidos de la via auditiva. Para conocer los limites de los lln, asi como su morfologia neuronal, hemos utilizado en 10 ratas albinas, el metodo de nisal y posterior analisis morfometrico. En los lln distinguimos un nucleo dorsal (dll) y un nucleo ventral (vll). El limite entre ambos lo constituye la lamina de los lln, zona donde se produce un entrecruzamiento de fibras del ll, en lln describimos 6 tipos neuronales morfologica y estadisticamente diferentes. Hemos inyectado iontoforeticamente el trazador anterogrado pha-l, en los lln de 15 ratas para conocer las proyecciones referentes de estos nucleos. Asi, dll proyecta al dll contralateral a traves de la comisura de probst, al nucleo central y corteza externa del coliculo inferior (ic) bilateralmente (bl), a la corteza dorsal del ic ipsilateral (il), e ipsilateralmente al coliculo superior (sc), a la division medial del cuerpo geniculado medial (mg), y al complejo oliva...
The Journal of Neuroscience, 2019
I also wish to draw your attention on the Nutrients website to our Editorial Board and also to th... more I also wish to draw your attention on the Nutrients website to our Editorial Board and also to the guest editors of our expanding list of special issues who have devoted their time and expertise to achieving rapid growth in the quantity and quality of published manuscripts. My special thanks also to Associate Editor, Jon Buckley, and members of the editorial office for their dedication to the journal.
Journal of Global Oncology, 2018
It is with great appreciation that we acknowledge the following reviewers who have served our res... more It is with great appreciation that we acknowledge the following reviewers who have served our research community by reviewing manuscripts for Nutrients in 2011.
Uploads
Papers by Victoria M Bajo