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Are there “local hotspots?” When concepts of cognitive psychology do not fit with physiological results. Behav Brain Sci 2016; 39:e208. [DOI: 10.1017/s0140525x1500179x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
AbstractMather and colleagues' arguments require rethinking at the mechanistic level. The arguments on the physiological effects of norepinephrine at the cortical level are inconsistent with large parts of the literature. There is no evidence that norepinephrine induces local “hotspots”: Norepinephrine mainly decreases evoked responses; facilitating effects are rare and not localized. More generally, the idea that perception benefits from “local hotspots” is hardly compatible with the fact that neural representations involve largely distributed activation of cortical and subcortical networks.
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Weinberger NM. New perspectives on the auditory cortex: learning and memory. HANDBOOK OF CLINICAL NEUROLOGY 2015; 129:117-47. [PMID: 25726266 DOI: 10.1016/b978-0-444-62630-1.00007-x] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Primary ("early") sensory cortices have been viewed as stimulus analyzers devoid of function in learning, memory, and cognition. However, studies combining sensory neurophysiology and learning protocols have revealed that associative learning systematically modifies the encoding of stimulus dimensions in the primary auditory cortex (A1) to accentuate behaviorally important sounds. This "representational plasticity" (RP) is manifest at different levels. The sensitivity and selectivity of signal tones increase near threshold, tuning above threshold shifts toward the frequency of acoustic signals, and their area of representation can increase within the tonotopic map of A1. The magnitude of area gain encodes the level of behavioral stimulus importance and serves as a substrate of memory strength. RP has the same characteristics as behavioral memory: it is associative, specific, develops rapidly, consolidates, and can last indefinitely. Pairing tone with stimulation of the cholinergic nucleus basalis induces RP and implants specific behavioral memory, while directly increasing the representational area of a tone in A1 produces matching behavioral memory. Thus, RP satisfies key criteria for serving as a substrate of auditory memory. The findings suggest a basis for posttraumatic stress disorder in abnormally augmented cortical representations and emphasize the need for a new model of the cerebral cortex.
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Affiliation(s)
- Norman M Weinberger
- Center for the Neurobiology of Learning and Memory and Department of Neurobiology and Behavior, University of California, Irvine, CA, USA.
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Edeline JM. Beyond traditional approaches to understanding the functional role of neuromodulators in sensory cortices. Front Behav Neurosci 2012; 6:45. [PMID: 22866031 PMCID: PMC3407859 DOI: 10.3389/fnbeh.2012.00045] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2012] [Accepted: 07/03/2012] [Indexed: 02/01/2023] Open
Abstract
Over the last two decades, a vast literature has described the influence of neuromodulatory systems on the responses of sensory cortex neurons (review in Gu, 2002; Edeline, 2003; Weinberger, 2003; Metherate, 2004, 2011). At the single cell level, facilitation of evoked responses, increases in signal-to-noise ratio, and improved functional properties of sensory cortex neurons have been reported in the visual, auditory, and somatosensory modality. At the map level, massive cortical reorganizations have been described when repeated activation of a neuromodulatory system are associated with a particular sensory stimulus. In reviewing our knowledge concerning the way the noradrenergic and cholinergic system control sensory cortices, I will point out that the differences between the protocols used to reveal these effects most likely reflect different assumptions concerning the role of the neuromodulators. More importantly, a gap still exists between the descriptions of neuromodulatory effects and the concepts that are currently applied to decipher the neural code operating in sensory cortices. Key examples that bring this gap into focus are the concept of cell assemblies and the role played by the spike timing precision (i.e., by the temporal organization of spike trains at the millisecond time-scale) which are now recognized as essential in sensory physiology but are rarely considered in experiments describing the role of neuromodulators in sensory cortices. Thus, I will suggest that several lines of research, particularly in the field of computational neurosciences, should help us to go beyond traditional approaches and, ultimately, to understand how neuromodulators impact on the cortical mechanisms underlying our perceptual abilities.
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Affiliation(s)
- Jean-Marc Edeline
- Centre de Neurosciences Paris-Sud, CNRS UMR 8195, Université Paris-Sud, Bâtiment Orsay Cedex, France
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Brain-generated estradiol drives long-term optimization of auditory coding to enhance the discrimination of communication signals. J Neurosci 2011; 31:3271-89. [PMID: 21368039 DOI: 10.1523/jneurosci.4355-10.2011] [Citation(s) in RCA: 74] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Auditory processing and hearing-related pathologies are heavily influenced by steroid hormones in a variety of vertebrate species, including humans. The hormone estradiol has been recently shown to directly modulate the gain of central auditory neurons, in real time, by controlling the strength of inhibitory transmission via a nongenomic mechanism. The functional relevance of this modulation, however, remains unknown. Here we show that estradiol generated in the songbird homolog of the mammalian auditory association cortex, rapidly enhances the effectiveness of the neural coding of complex, learned acoustic signals in awake zebra finches. Specifically, estradiol increases mutual information rates, coding efficiency, and the neural discrimination of songs. These effects are mediated by estradiol's modulation of both the rate and temporal coding of auditory signals. Interference with the local action or production of estradiol in the auditory forebrain of freely behaving animals disrupts behavioral responses to songs, but not to other behaviorally relevant communication signals. Our findings directly show that estradiol is a key regulator of auditory function in the adult vertebrate brain.
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Non-sensory cortical and subcortical connections of the primary auditory cortex in Mongolian gerbils: bottom-up and top-down processing of neuronal information via field AI. Brain Res 2007; 1220:2-32. [PMID: 17964556 DOI: 10.1016/j.brainres.2007.07.084] [Citation(s) in RCA: 87] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2007] [Revised: 07/04/2007] [Accepted: 07/05/2007] [Indexed: 11/24/2022]
Abstract
In the present study, we will provide further anatomical evidence that the primary auditory cortex (field AI) is not only involved in sensory processing of its own modality, but also in complex bottom-up and top-down processing of multimodal information. We have recently shown that AI in the Mongolian gerbil (Meriones unguiculatus) has substantial connections with non-auditory sensory and multisensory brain structures [Budinger, E., Heil, P., Hess, A., Scheich, H., 2006. Multisensory processing via early cortical stages: Connections of the primary auditory cortical field with other sensory systems. Neuroscience 143, 1065-1083]. Here we will report about the direct connections of AI with non-sensory cortical areas and subcortical structures. We approached this issue by means of the axonal transport of the sensitive bidirectional neuronal tracers fluorescein-labelled (FD) and tetramethylrhodamine-labelled dextran (TMRD), which were simultaneously injected into different frequency regions of the gerbil's AI. Of the total number of retrogradely labelled cell bodies found in non-sensory brain areas, which identify cells of origin of direct projections to AI, approximately 24% were in cortical areas and 76% in subcortical structures. Of the cell bodies in the cortical areas, about 4.4% were located in the orbital, 11.1% in the infralimbic medial prefrontal (areas DPC, IL), 18.2% in the cingulate (3.2% in CG1, 2.9% in CG2, 12.1% in CG3), 9.5% in the frontal association (area Fr2), 12.0% in the insular (areas AI, DI), 10.8% in the retrosplenial, and 34.0% in the perirhinal cortex. The cortical regions with retrogradely labelled cells, as well as the entorhinal cortex, also contained anterogradely labelled axons and their terminations, which means that they are also target areas of direct projections from AI. The laminar pattern of corticocortical connections indicates that AI receives primarily cortical feedback-type inputs and projects in a feedforward manner to its target areas. The high number of double-labelled somata, the non-topographic distribution of single FD- and TMRD-labelled somata, and the overlapping spatial distribution of FD- and TMRD-labelled axonal elements suggest rather non-tonotopic connections between AI and the multimodal cortices. Of the labelled cell bodies in the subcortical structures, about 38.8% were located in the ipsilateral basal forebrain (10.6% in the lateral amygdala LA, 11.5% in the globus pallidus GP, 3.7% in the ventral pallidum VPa, 13.0% in the nucleus basalis NB), 13.1% in the ipsi- and contralateral diencephalon (6.4% in the posterior paraventricular thalamic nuclei, 6.7% in the hypothalamic area), and 48.1% in the midbrain (20.0% in the ipsilateral substantia nigra, 9.8% in the ipsi- and contralateral ventral tegmental area, 5.0% in the ipsi- and contralateral locus coeruleus, 13.3% the ipsi- and contralateral dorsal raphe nuclei). Thus, the majority of subcortical inputs to AI was related to different neurotransmitter systems. Anterograde labelling was only found in some ipsilateral basal forebrain structures, namely, the LA, basolateral amygdala, GP, VPa, and NB. As for the cortex, the proportion and spatial distribution of single FD-, TMRD-, and double-labelled neuronal elements suggests rather non-tonotopic connections between AI and the neuromodulatory subcortical structures.
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Edeline JM. The thalamo-cortical auditory receptive fields: regulation by the states of vigilance, learning and the neuromodulatory systems. Exp Brain Res 2003; 153:554-72. [PMID: 14517594 DOI: 10.1007/s00221-003-1608-0] [Citation(s) in RCA: 98] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2002] [Accepted: 06/14/2003] [Indexed: 11/26/2022]
Abstract
The goal of this review is twofold. First, it aims to describe the dynamic regulation that constantly shapes the receptive fields (RFs) and maps in the thalamo-cortical sensory systems of undrugged animals. Second, it aims to discuss several important issues that remain unresolved at the intersection between behavioral neurosciences and sensory physiology. A first section presents the RF modulations observed when an undrugged animal spontaneously shifts from waking to slow-wave sleep or to paradoxical sleep (also called REM sleep). A second section shows that, in contrast with the general changes described in the first section, behavioral training can induce selective effects which favor the stimulus that has acquired significance during learning. A third section reviews the effects triggered by two major neuromodulators of the thalamo-cortical system--acetylcholine and noradrenaline--which are traditionally involved both in the switch of vigilance states and in learning experiences. The conclusion argues that because the receptive fields and maps of an awake animal are continuously modulated from minute to minute, learning-induced sensory plasticity can be viewed as a "crystallization" of the receptive fields and maps in one of the multiple possible states. Studying the interplays between neuromodulators can help understanding the neurobiological foundations of this dynamic regulation.
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Affiliation(s)
- Jean-Marc Edeline
- Laboratoire de Neurobiologie de l'Apprentissage de la Mémoire et de la Communication, Université Paris-Sud, UMR 8620, Bat 446, 91405 Orsay, France.
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Ego-Stengel V, Bringuier V, Shulz DE. Noradrenergic modulation of functional selectivity in the cat visual cortex: an in vivo extracellular and intracellular study. Neuroscience 2002; 111:275-89. [PMID: 11983314 DOI: 10.1016/s0306-4522(02)00011-8] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
In vitro intracellular studies have shown that norepinephrine modulates cellular excitability and synaptic transmission in the cortex. Based on these effects, norepinephrine has been proposed to enhance the signal-to-noise ratio and to improve functional selectivity by potentiating strong synaptic responses and reducing weak ones. Here we have studied the functional effects of iontophoretic applications of norepinephrine during in vivo extracellular and intracellular recordings from neurons of the primary visual cortex of kittens and adult cats. Analysis of extracellular data concentrated on norepinephrine-induced changes in spontaneous and evoked activities, in signal-to-noise ratio, and in orientation and direction selectivity. Analysis of the intracellular data concentrated on actions of norepinephrine on spike firing accommodation, which has been shown to be reduced by norepinephrine in vitro, and on synaptic responses. Application of norepinephrine resulted in a depression of both spontaneous and evoked spiking activity. However, no systematic change in signal-to-noise ratio was observed. The suppressive effect of norepinephrine was exerted with no significant sharpening of direction or orientation selectivity tuning. The overall reduction in visual activity by norepinephrine affected the orientation tuning curves in a way compatible with a divisive effect, that is a normalization or gain control with no change in tuning width. Norepinephrine applied during intracellular recordings reduced the visually evoked depolarizing potentials whereas no change in the responsiveness of the cell to current-induced depolarizations was observed. In conditions of optimal visual stimulation which produced large depolarizations of several hundreds of milliseconds and sustained repetitive firing comparable to that obtained by direct current injection, we were unable to observe a facilitation of the evoked responses by norepinephrine as it would be expected from the well-documented increase in excitability induced by norepinephrine in vitro. In conclusion, from these results we suggest that norepinephrine released in the primary visual cortex primarily reduces the level of cortical activation by afferent signals, without affecting the cortical functional selectivity nor increasing the signal-to-noise ratio.
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Affiliation(s)
- V Ego-Stengel
- Unité de Neurosciences Intégratives et Computationnelles, Institut de Neurobiologie Alfred Fessard, Centre National de la Recherche Scientifique, 1, Avenue de la Terrasse, 91198 Gif sur Yvette, France
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Mercado E, Myers CE, Gluck MA. A computational model of mechanisms controlling experience-dependent reorganization of representational maps in auditory cortex. COGNITIVE, AFFECTIVE & BEHAVIORAL NEUROSCIENCE 2001; 1:37-55. [PMID: 12467102 DOI: 10.3758/cabn.1.1.37] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Cortical representations of sound can be modified by repeatedly pairing presentation of a pure tone with electrical stimulation of neuromodulatory neurons located in the basal forebrain (Bakin & Weinberger, 1996; Kilgard & Merzenich, 1998a). We developed a computational model to investigate the possible effects of basal forebrain modulation on map reorganization in the auditory cortex. The model is a self-organizing map with acoustic response characteristics mimicking those observed in the mammalian auditory cortex. We simulated the effects of basal forebrain modulation, using parameters intrinsic to the self-organizing map, such as the learning rate (controlling the adaptability of map nodes) and the neighborhood function (controlling the excitability of map nodes). Previous research has suggested that both parameters can be useful for characterizing the effects of neuromodulation on plasticity (Kohonen, 1993; Myers et al., 1996; Myers, Ermita, Hasselmo, & Gluck, 1998). The model successfully accounts for experimentally observed effects of pairing basal forebrain stimulation with the presentation of a single tone, but not of two tones, suggesting that auditory cortical plasticity is constrained in ways not accounted for by current theories. Despite this limitation, the model provides a useful framework for describing experience-induced changes in auditory representations and for relating such changes to variations in the excitability and adaptability of cortical neurons produced by neuromodulation.
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Affiliation(s)
- E Mercado
- Center for Molecular and Behavioral Neuroscience, Rutgers University, 197 University Ave., Newark, NJ 07102, USA.
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9
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Roberts TF, Cookson KK, Heaton KJ, Hall WS, Brauth SE. Distribution of tyrosine hydroxylase-containing neurons and fibers in the brain of the budgerigar (Melopsittacus undulatus): general patterns and labeling in vocal control nuclei. J Comp Neurol 2001; 429:436-54. [PMID: 11116230 DOI: 10.1002/1096-9861(20010115)429:3<436::aid-cne6>3.0.co;2-h] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
The distribution of tyrosine hydroxylase (TH) was mapped out in cells and fibers of the budgerigar (Melopsittacus undulatus) brain. Special attention was given to vocal control and auditory nuclei because budgerigars are a psittacine species in which both males and females are capable of lifelong vocal learning (Farabaugh et al. [1994] J. Comp. Psychol 108:81-92). The results show that TH staining in the central nucleus of the anterior archistriatum (AAc) resembled that of surrounding archistriatal fields, except for portions of the ventral archistriatum, which exhibited substantially more TH+ fibers. Fewer fibers and fiber baskets are present in the central nucleus of the lateral neostriatum (NLc) than in surrounding fields. Both the oval nuclei of the ventral hyperstriatum (HVo) and anterior neostriatum (NAo) exhibit less fiber staining than surrounding fields whereas fiber staining in the medial NAo (NAom) and magnicellular nucleus of the parolfactory lobe (LPOm) resemble that of surrounding fields. Staining in primary telencephalic auditory nuclei was extremely low. The only sex difference observed was slightly increased TH staining in LPOm of females compared with surrounding fields on some tissue sections. These findings are in contrast to previous findings in zebra finch (Poephila guttata), a close ended vocal learning songbird in which TH staining in vocal nuclei increases during development and remains greater than surrounding fields throughout adulthood. The present results therefore support the view that catecholamines act to inhibit vocal plasticity in adult vocal learning species. Several unique features of TH-immunoreactive (ir) cell groups were observed in the brainstem including sparsely scattered TH-ir somata immediately adjacent to the third ventricle, within the tectum, basal forebrain, archistriatum, and caudal neostriatum, and in the hippocampus. These latter populations have not been described in other avian species and resemble features of the catecholamine system generally found in either reptiles or mammals.
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Affiliation(s)
- T F Roberts
- Department of Psychology, University of Maryland, College Park, Maryland 20742, USA.
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10
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Cotillon N, Edeline JM. Tone-evoked oscillations in the rat auditory cortex result from interactions between the thalamus and reticular nucleus. Eur J Neurosci 2000; 12:3637-50. [PMID: 11029634 DOI: 10.1046/j.1460-9568.2000.00254.x] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
This study investigates the origins of tone-evoked oscillations (5-13 Hz) in the thalamo-cortical auditory system of anaesthetized rats. In three separate experiments, the auditory sector of the reticular nucleus (RE), the auditory cortex and the auditory thalamus were inactivated by local applications of muscimol (1 mg/mL). To assess the efficacy of this procedure, recordings were performed in the inactivated structure in each experiment; and to determine the extent of the drug diffusion autoradiographic experiments were carried out. The evolution of the strength of the oscillations was followed using power spectra during the whole recording session. In the first experiment, muscimol injection in the auditory RE totally suppressed the tone-evoked oscillations in the auditory thalamus and cortex. In the second experiment, inactivation of the auditory cortex did not interfere with the presence of tone-evoked oscillations in the auditory RE. In the third experiment, inactivation of the auditory thalamus impaired the oscillations produced by cortical stimulation in the auditory RE. From these results, it appears that both the auditory thalamus and the auditory sector of the RE, but not the auditory cortex, are involved in the generation of stimulus-evoked oscillations in the thalamo-cortical auditory system.
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Affiliation(s)
- N Cotillon
- Laboratoire de Neurobiologie de l'Apprentissage, de la Mémoire et de la Communication, CNRS UMR 8620, Université Paris-Sud, Bât 446, 91405 Orsay, France
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Waterhouse BD, Mouradian R, Sessler FM, Lin RC. Differential modulatory effects of norepinephrine on synaptically driven responses of layer V barrel field cortical neurons. Brain Res 2000; 868:39-47. [PMID: 10841886 DOI: 10.1016/s0006-8993(00)02261-7] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
The effects of norepinephrine (NE) and the alpha-1 agonist phenylephrine (PE) on synaptically evoked responses of electrophysiologically identified pyramidal neurons in layer V of rat somatosensory cortex were studied in brain slices using intracellular recording techniques. When added to the bathing medium NE (10 microM) tended to increase the synaptic responsiveness of regular spiking neurons and decrease the responsiveness of intrinsic burst neurons. NE had mixed effects on layer V cells which were characterized as intermediate types between regular spiking and intrinsic burst neurons. PE exerted a similar spectrum of actions on layer V cortical neurons. For both adrenergic agents the greatest facilitating effect was observed on responses to low intensity synaptic stimulation. These results suggest that NE exerts different modulatory actions on different electrophysiologically-defined classes of layer V sensory cortical neurons.
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Affiliation(s)
- B D Waterhouse
- Department of Neurobiology and Anatomy, MCP-Hahnemann University, 3200 Henry Avenue, Philadelphia, PA 19129, USA.
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Cotillon N, Nafati M, Edeline JM. Characteristics of reliable tone-evoked oscillations in the rat thalamo-cortical auditory system. Hear Res 2000; 142:113-30. [PMID: 10748334 DOI: 10.1016/s0378-5955(00)00016-2] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Tone-evoked oscillations were studied from simultaneous recordings collected in the auditory cortex, auditory thalamus and auditory sector of the reticular nucleus in urethane anesthetized rats. These oscillations were precisely time-locked to tone onset and were easily observed on peristimulus time histograms (PSTHs). Visual inspection of PSTHs and rasters led us to distinguish between 'reliable' oscillations (which exhibited oscillatory patterns in more than 50% of the trials) and 'labile' oscillations (which exhibited oscillations in less than 50% of the trials). Systematic quantification of oscillations based on several indices derived from power spectra confirmed this distinction. 'Reliable' stimulus-locked oscillations were observed in 51/184 (28%) of the recordings from auditory cortex, 9/55 (17%) of the recordings from auditory thalamus and 11/26 (42%) of the recordings from the auditory sector of the reticular nucleus. The frequency range of these oscillations was the same in the three structures (5-14 Hz). Within the same animal, when one electrode exhibited oscillations, there was a high probability of detecting similar oscillations from electrodes located in the same structure, but not from electrodes located in the other structures. These oscillations were observed for pure tone frequency (or for clicks) whatever the tone duration (1 s, 100 ms, 10 ms). The inter-tone interval (ITI) was found to be the critical factor controlling the occurrence of these oscillations: they were present for ITIs of 2 s or longer, but were absent for ITIs of 1 s or less. In contrast, the occurrence of the oscillations was a function neither of the strength of the 'on' evoked response nor of the animal's temperature. However, lowering the animal's temperature from 37-38 degrees C to 35-36 degrees C systematically led to a decrease in the frequency and an increase in the duration of the tone-evoked oscillations. These results suggest that, even in well defined conditions (temperature, EEG, ITI, level of anesthesia), the oscillations triggered by presentation of the same stimulus can be stable or unstable. This temporal instability of stimulus-evoked oscillations has to be taken into account before stating percentages of oscillations in a given brain structure. They also suggest that some general factors such as the animals temperature or the inter-stimulus interval can considerably affect their characteristics and/or their occurrence.
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Affiliation(s)
- N Cotillon
- Laboratoire de Neurobiologie de l'Apprentissage, de la Mémoire et de la Communication, CNRS UMR 8620, Université Paris-Sud, Bât. 446, 91405, Orsay, France
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Manunta Y, Edeline JM. Effects of noradrenaline on frequency tuning of auditory cortex neurons during wakefulness and slow-wave sleep. Eur J Neurosci 1999; 11:2134-50. [PMID: 10336682 DOI: 10.1046/j.1460-9568.1999.00633.x] [Citation(s) in RCA: 76] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
This study shows the effects of noradrenaline (NA) on receptive fields of auditory cortex neurons in awake animals; it is the first one to describe the effects of NA on neurons in sensory cortex, in different natural states of vigilance. The frequency receptive field of 250 auditory cortex neurons was determined before, during and after ionophoretic application of NA while recording the state of vigilance of unanaesthetized guinea-pigs. When NA significantly changed the spontaneous activity (85 out of 250 cells), the dominant effect was a decrease (61 out of 85 cells, 72%). When NA significantly changed the evoked activity (107 out of 250 cells), the dominant effect was also a decrease (84 out of 107 cells, 78%). During and after NA application, the signal-to-noise ratio (S/N, i.e. evoked/spontaneous activity) was unchanged, but the selectivity for pure-tone frequencies was enhanced. When the effects occurring in wakefulness and in slow-wave sleep (SWS) were compared, it appeared that the predominantly inhibitory effect of NA on spontaneous and evoked activity was present in both states. The S/N ratio was unchanged and the selectivity was increased in both states. However, during SWS, the percentage of cells inhibited by NA was lower, and the effects on the frequency selectivity were smaller than in wakefulness. In contrast, GABA produced similar inhibitory effects on spontaneous and on evoked activity during wakefulness and SWS. Comparisons with previous data obtained using the same protocol in urethane anaesthetized animals (Manunta & Edeline 1997) indicate that the effects of NA were qualitatively the same. Based on these results, we suggest that any hypothesis concerning the role of NA in cortical plasticity should take into account the fact that the predominantly inhibitory effects of NA lead to decrease the size of the receptive field.
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Affiliation(s)
- Y Manunta
- Laboratoire de Neurobiologie de l'Apprentissage et de la Mémoire, CNRS URA 1491, Université Paris-Sud, Orsay, France
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Winer JA, Sally SL, Larue DT, Kelly JB. Origins of medial geniculate body projections to physiologically defined zones of rat primary auditory cortex. Hear Res 1999; 130:42-61. [PMID: 10320098 DOI: 10.1016/s0378-5955(98)00217-2] [Citation(s) in RCA: 86] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Medial geniculate body neurons projecting to physiologically identified subregions of rat primary auditory cortex (area 41, Te1) were labeled with horseradish peroxidase in adult rats. The goals were to determine the type(s) of projection neuron and the spatial arrangement of these cells with respect to thalamic subdivisions. Maps of best frequency were made with single neuron or unit cluster extracellular recording at depths of 500-800 microm, which correspond to layers III-IV in Nissl preparations. Tracer injections were made in different cortical isofrequency regions (2, 11, 22, or 38 kHz, respectively). Labeled neurons were plotted on representative sections upon which the architectonic subdivisions were drawn independently. Most of the cells of origin lay in the ventral division in every experiment. Injections at low frequencies labeled bands of neurons laterally in the ventral division; progressively more rostral deposits at higher frequencies labeled bands or clusters more medially in the ventral division, and through most of its caudo-rostral extent. Medial division labeling was variable. Labeled cells were always in the lateral half of the nucleus and were often scattered. There were few labeled cells in the dorsal division. Seven types of thalamocortical neuron were identified: ventral division cells had a tufted branching pattern, while medial division neurons have heterogeneous shapes and sizes and were larger. Dorsal division neurons had a radiate branching pattern. The size range of labeled neurons spanned that of Nissl stained neuronal somata. Area 41 may receive two types of thalamic projection: ventral division input is strongly convergent, highly topographic, spatially focal, and restricted to one type of neuron only, while the medial division projection is more divergent, coarsely topographical, involves multiple cortical areas, and has several varieties of projection neuron. Despite species differences in local circuitry, many facets of thalamocortical organization are conserved in phylogeny.
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Affiliation(s)
- J A Winer
- Department of Molecular and Cell Biology, University of California at Berkeley, 94720-3200, USA.
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15
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Edeline JM. Learning-induced physiological plasticity in the thalamo-cortical sensory systems: a critical evaluation of receptive field plasticity, map changes and their potential mechanisms. Prog Neurobiol 1999; 57:165-224. [PMID: 9987805 DOI: 10.1016/s0301-0082(98)00042-2] [Citation(s) in RCA: 159] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The goal of this review is to give a detailed description of the main results obtained in the field of learning-induced plasticity. The review is focused on receptive field and map changes observed in the auditory, somatosensory and visual thalamo-cortical system as a result of an associative training performed in waking animals. Receptive field (RF) plasticity, 2DG and map changes obtained in the auditory and somatosensory system are reviewed. In the visual system, as there is no RF and map analysis during learning per se, the evidence presented are from increased neuronal responsiveness, and from the effects of perceptual learning in human and non human primates. Across sensory modalities, the re-tuning of neurons to a significant stimulus or map reorganizations in favour of the significant stimuli were observed at the thalamic and/or cortical level. The analysis of the literature in each sensory modality indicates that relationships between learning-induced sensory plasticity and behavioural performance can, or cannot, be found depending on the tasks that were used. The involvement (i) of Hebbian synaptic plasticity in the described neuronal changes and (ii) of neuromodulators as "gating" factors of the neuronal changes, is evaluated. The weakness of the Hebbian schema to explain learning-induced changes and the need to better define what the word "learning" means are stressed. It is suggested that future research should focus on the dynamic of information processing in sensory systems, and the concept of "effective connectivity" should be useful in that matter.
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Affiliation(s)
- J M Edeline
- NAMC, URA CNRS 1491, Université Paris-Sud, Orsay, France.
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16
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Wang X, Robertson D. Substance P-induced inward current in identified auditory efferent neurons in rat brain stem slices. J Neurophysiol 1998; 80:218-29. [PMID: 9658043 DOI: 10.1152/jn.1998.80.1.218] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023] Open
Abstract
The effects of substance P (SP) on whole cell currents were studied in neurons of the medial olivocochlear efferent system (MOCS) in the ventral nucleus of the trapezoid body (VNTB) of brain stem slices from neonatal rats. Each neuron was identified by retrograde labeling with Fast Blue injected into the cochlea. Bath application of SP (0.1-10 microM) reversibly induced an apparent inward current in 49 of 63 labeled neurons when voltage clamped at near resting voltages. This apparent inward current was consistent with the SP-induced membrane depolarization observed in current-clamp mode. The SP-induced change in current was dose dependent with a half-maximal response dose of 200 nM. It was mimicked by [Cys3,6, Tyr8, Pro9]-SP, a neurokinin (NK1) receptor selective agonist, whereas [Succinyl-Asp6, MePhe8]-SP 6-11 (Senktide), a NK3 receptor agonist, had no detectable effect. The SP effect was not blocked by 10(-6) M tetrodotoxin (TTX) and persisted when the perfusate contained 30 mM tetraethylammonium (TEA) or 100 microM Cd2+ or was in a 0-Ca solution. In a TTX-containing solution, SP caused a voltage-dependent decrease of membrane conductance, and the SP-evoked current reversed at a potential at around -105 mV. The predicted K+ equilibrium potential was -93.8 mV under the experimental conditions. The SP-induced inward current was attenuated by 66% when the perfusate contained 3 mM Cs+. We conclude that the apparent inward current is partly caused by SP decreasing an outward current normally maintained by the inward rectifier K+ channels in these cells. In the presence of Cs solution in the recording pipette and with a perfusate containing 3 mM Cs+, 0.1 mM Cd2+ and 10(-6) M TTX, a residual SP-induced inward current was observed at test voltages ranging from -120 to 40 mV. This subcomponent reversed its polarity at approximately 20 mV. This inward current was reduced substantially (but not abolished) when all NaCl in the external solution was replaced by TEA-Cl. The results indicate that SP also opens an unknown cation channel, which the available data suggests may be relatively nonselective. The results suggest that MOCS neurons are subject to modulation by SP, which depolarizes the cell membrane by decreasing the activity of inward rectifier K+ channels as well as concurrently activating a separate cation conductance. It also was found that in MOCS neurons responsive to both SP and norepinephrine, the norepinephrine effect was abolished by TTX, suggesting that an interneuronal population excited by norepinephrine converges selectively onto SP-sensitive MOCS neurons in the VNTB.
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Affiliation(s)
- X Wang
- Department of Physiology, The Auditory Laboratory, The University of Western Australia, Nedlands, Western Australia 6907, Australia
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Cransac H, Cottet-Emard JM, Hellström S, Peyrin L. Specific sound-induced noradrenergic and serotonergic activation in central auditory structures. Hear Res 1998; 118:151-6. [PMID: 9606070 DOI: 10.1016/s0378-5955(98)00031-8] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
We have studied the noradrenergic and serotonergic changes induced by white noise stimulation at 70, 90 or 110 dB SPL for 45 min, in cochlear nuclei, inferior colliculus (IC), primary auditory cortex (PAC) and as a comparison in locus coeruleus (LC) and raphe dorsalis using HPLC. Both noradrenergic and serotonergic pathways were activated in the dorsal+posteroventral cochlear nuclei (DCN+PVCN) without changes in the anteroventral cochlear nucleus (AVCN) and IC. In the DCN+PVCN the noradrenergic activation was restricted to animals exposed to 70 dB SPL whereas the increase of serotonin content was intensity-dependent. In PAC serotonergic activation was observed only after 70 dB SPL exposure. These data suggest that in physiological conditions (70 dB SPL) noradrenergic and serotonergic regulation of the processing of auditory information occurs specifically in the dorsal cochlear nucleus where the control of incoming information to higher auditory structures takes place (i.e. IC and PAC). We suggest that the serotonergic activation in the primary auditory cortex for 70 dB SPL sound stimulation could be related to the fact that low-intensity white noise stimulation could be the most plastic-demanding processing in the auditory cortex.
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Affiliation(s)
- H Cransac
- UPRESA CNRS 5020, Hôpital Edouard Herriot, Lyon, France.
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18
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Wang X, Robertson D. Two types of actions of norepinephrine on identified auditory efferent neurons in rat brain stem slices. J Neurophysiol 1997; 78:1800-10. [PMID: 9325349 DOI: 10.1152/jn.1997.78.4.1800] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Whole cell voltage-clamp recordings were performed on auditory olivocochlear neurons in the ventral nucleus of the trapezoid body (VNTB) of brain stem slices from neonatal rats. Each neuron was identified by retrograde labeling with Fast Blue injected into the cochlea. Bath application of norepinephrine (NE; 1-10 microM) reversibly induced an inward current in 26 of 38 labeled neurons that were voltage clamped at -75 mV. This was responsible for the membrane depolarization to NE observed in current-clamp mode. The NE-induced inward current appeared to be more prominent at -55 mV than at -75 mV and reversed at around -100 mV. It was attenuated but not prevented by 20 mM tetraethylammonium, and it persisted when the perfusate contained 2 mM Cs+ or 100 microM Cd2+. However, the NE-induced inward current was attenuated to varying degrees in a zero-Ca2+ solution. Current-voltage plots revealed that NE caused a decrease in membrane K+ conductance. A suppression of voltage-gated Ca2+ currents by NE was also observed. The excitatory action of NE was blocked by the alpha-adrenoreceptor antagonist phentolamine. The alpha1-adrenoreceptor agonist phenylephrine had an effect similar to that of NE. In 6 of 38 labeled neurons, an inhibitory action of NE (1-10 microM) was observed that appeared to be due to an activation of an inwardly rectified K+ current, which caused hyperpolarization of resting membrane potentials in current-clamp mode. This inhibitory response was independent of external Ca2+ and was abolished by 2-5 mM Cs+ or 0.5 mM Ba2+ applied in the perfusate. The receptors involved in the inhibitory actions of NE are not clear. The effect was partially and reversibly blocked by propranolol (10 microM), a beta-adrenoreceptor antagonist. However, isoprenaline (10 microM), a beta-adrenoreceptor agonist, failed to induce any effect. On the other hand, the inhibitory effect was irreversibly blocked by pretreatment with phentolamine (5-10 microM). Phenylephrine (5-10 microM) had no effect.
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Affiliation(s)
- X Wang
- The Auditory Laboratory, Department of Physiology, The University of Western Australia, Nedlands, Western Australia 6907, Australia
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Abstract
The selectivity of rat auditory cortex neurons for pure tone frequency was studied during and after ionophoretic application (5-40 nA) of noradrenaline in urethane-anaesthetized rats. The dominant effect induced by noradrenaline was a significant decrease in spontaneous (93/268 cells) and evoked activity (133/268 cells) which outlasted the application. In the whole population of cells (n = 268) the signal-to-noise ratio, computed using as the signal either the mean evoked response or the response at the best frequency, was unchanged during noradrenaline application. It was significantly increased only for cells showing significantly decreased spontaneous activity, and was significantly decreased for cells showing increased spontaneous activity. Frequency selectivity was significantly increased for the whole population during and after noradrenaline application. It was also significantly increased for cells showing significantly decreased evoked activity, and was significantly decreased for cells showing increased evoked activity. The noradrenaline-induced inhibition was not blocked by propranolol (beta antagonist); it was blocked by prazosin (alpha1 antagonist) and partly mimicked by phenylephrine (alpha1 agonist). GABA, which also inhibited spontaneous and evoked activity, slightly increased the signal-to-noise ratio and significant increased frequency selectivity. However, when noradrenaline was ejected in the presence of bicuculline at doses that were able to block GABAergic inhibition, the inhibitory effects of noradrenaline on spontaneous and evoked activity were still observed. The possible function of noradrenaline-induced inhibitions in sensory cortices is briefly discussed.
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Affiliation(s)
- Y Manunta
- Laboratoire de Neurobiologie de l'Apprentissage et de la Mémoire, CNRSURA 1491, Université Paris-Sud, Orsay, France
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Cransac H, Peyrin L, Cottet-Emard JM, Farhat F, Pequignot JM, Reber A. Aging effects on monoamines in rat medial vestibular and cochlear nuclei. Hear Res 1996; 100:150-6. [PMID: 8922989 DOI: 10.1016/0378-5955(96)00116-5] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Noradrenaline (NA), dopamine (DA); serotonin (5-HT) and their metabolites-3-methoxy, 4-hydroxyphenylglycol (MHPG), 3,4-dihydroxyphenylacetic acid (DOPAC) and 5-hydroxyindoleacetic acid (5-HIAA)-were determined using HPLC in medial vestibular nucleus (MVN), anteroventral cochlear nucleus (AVCN), dorsal+posteroventral cochlear nucleus (DCN+PVCN), locus coeruleus (LC) and raphe dorsalis of Dark Agouti-Hanovre (DA-HAN) rats aged 4, 21 and 24 months. In older rats, the main noradrenergic changes were a decrease of NA content with an increase of the MHPG/NA ratio in MVN and a selective NA increase in AVCN. 5-HT and 5-HIAA levels were increased in all the brainstem nuclei except raphe dorsalis. DA and DOPAC remained unchanged. These data show that noradrenergic neurons in sensory nuclei are differently affected by aging whereas serotonergic activation occurs in most of them possibly as a compensatory response to dysfunction of sensory input and processing. The increase of NA stores in the AVCN of aged rats is in line with the elevated auditory brainstem threshold reported in old rats and could improve the signal-to-noise ratio. Noradrenergic neurons in the MVN seem to be more sensitive to age effect than cochlear nuclei; however, even if neuronal loss occurs, NA synthesis and/or metabolism increase to ensure normal or increased noradrenergic activity.
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Affiliation(s)
- H Cransac
- URA CNRS 1447, Faculté de Médecine Grange-Blanche, Lyon, France
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