26
|
Michie PT, Malmierca MS, Harms L, Todd J. The neurobiology of MMN and implications for schizophrenia. Biol Psychol 2016; 116:90-7. [DOI: 10.1016/j.biopsycho.2016.01.011] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2015] [Accepted: 01/24/2016] [Indexed: 01/09/2023]
|
27
|
Ayala YA, Pérez-González D, Malmierca MS. Stimulus-specific adaptation in the inferior colliculus: The role of excitatory, inhibitory and modulatory inputs. Biol Psychol 2016; 116:10-22. [DOI: 10.1016/j.biopsycho.2015.06.016] [Citation(s) in RCA: 42] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2015] [Revised: 06/27/2015] [Accepted: 06/30/2015] [Indexed: 01/01/2023]
|
28
|
Ayala YA, Malmierca MS. Cholinergic Modulation of Stimulus-Specific Adaptation in the Inferior Colliculus. J Neurosci 2015; 35:12261-72. [PMID: 26338336 PMCID: PMC6605313 DOI: 10.1523/jneurosci.0909-15.2015] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2015] [Revised: 07/13/2015] [Accepted: 07/28/2015] [Indexed: 01/28/2023] Open
Abstract
Neural encoding of an ever-changing acoustic environment is a complex and demanding process that depends on modulation by neuroactive substances. Some neurons of the inferior colliculus (IC) exhibit "stimulus-specific adaptation" (SSA), i.e., a decrease in their response to a repetitive sound, but not to a rare one. Previous studies have demonstrated that acetylcholine (ACh) alters the frequency response areas of auditory neurons and therefore is important in the encoding of spectral information. Here, we address how microiontophoretic application of ACh modulates SSA in the IC of the anesthetized rat. We found that ACh decreased SSA in IC neurons by increasing the response to the repetitive tone. This effect was mainly mediated by muscarinic receptors. The strength of the cholinergic modulation depended on the baseline SSA level, exerting its greatest effect on neurons with intermediate SSA responses across IC subdivisions. Our data demonstrate that the increased availability of ACh exerts transient functional changes in partially adapting IC neurons, enhancing the sensory encoding of the ongoing stimulation. This effect potentially contributes to the propagation of ascending sensory-evoked afferent activity through the thalamus en route to the cortex. SIGNIFICANCE STATEMENT Neural encoding of an ever-changing acoustic environment is a complex and demanding task that may depend on the available levels of neuroactive substances. We explored how the cholinergic inputs affect the responses of neurons in the auditory midbrain that exhibit different degrees of stimulus-specific adaptation (SSA), i.e., a specific decrease in their response to a repeated sound that does not generalize to other, rare sounds. This work addresses the role of cholinergic synaptic inputs as well as the contribution of the muscarinic and nicotinic receptors on SSA. This is the first report on the role of neuromodulation on SSA, and the results contribute to our understanding of the cellular bases for processing low- and high-probability sounds.
Collapse
|
29
|
Ayala YA, Udeh A, Dutta K, Bishop D, Malmierca MS, Oliver DL. Differences in the strength of cortical and brainstem inputs to SSA and non-SSA neurons in the inferior colliculus. Sci Rep 2015; 5:10383. [PMID: 25993334 PMCID: PMC4438612 DOI: 10.1038/srep10383] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2015] [Accepted: 04/10/2015] [Indexed: 11/12/2022] Open
Abstract
In an ever changing auditory scene, change detection is an ongoing task performed by the auditory brain. Neurons in the midbrain and auditory cortex that exhibit stimulus-specific adaptation (SSA) may contribute to this process. Those neurons adapt to frequent sounds while retaining their excitability to rare sounds. Here, we test whether neurons exhibiting SSA and those without are part of the same networks in the inferior colliculus (IC). We recorded the responses to frequent and rare sounds and then marked the sites of these neurons with a retrograde tracer to correlate the source of projections with the physiological response. SSA neurons were confined to the non-lemniscal subdivisions and exhibited broad receptive fields, while the non-SSA were confined to the central nucleus and displayed narrow receptive fields. SSA neurons receive strong inputs from auditory cortical areas and very poor or even absent projections from the brainstem nuclei. On the contrary, the major sources of inputs to the neurons that lacked SSA were from the brainstem nuclei. These findings demonstrate that auditory cortical inputs are biased in favor of IC synaptic domains that are populated by SSA neurons enabling them to compare top-down signals with incoming sensory information from lower areas.
Collapse
|
30
|
Malmierca MS, Anderson LA, Antunes FM. The cortical modulation of stimulus-specific adaptation in the auditory midbrain and thalamus: a potential neuronal correlate for predictive coding. Front Syst Neurosci 2015; 9:19. [PMID: 25805974 PMCID: PMC4353371 DOI: 10.3389/fnsys.2015.00019] [Citation(s) in RCA: 77] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2014] [Accepted: 02/03/2015] [Indexed: 02/02/2023] Open
Abstract
To follow an ever-changing auditory scene, the auditory brain is continuously creating a representation of the past to form expectations about the future. Unexpected events will produce an error in the predictions that should “trigger” the network’s response. Indeed, neurons in the auditory midbrain, thalamus and cortex, respond to rarely occurring sounds while adapting to frequently repeated ones, i.e., they exhibit stimulus specific adaptation (SSA). SSA cannot be explained solely by intrinsic membrane properties, but likely involves the participation of the network. Thus, SSA is envisaged as a high order form of adaptation that requires the influence of cortical areas. However, present research supports the hypothesis that SSA, at least in its simplest form (i.e., to frequency deviants), can be transmitted in a bottom-up manner through the auditory pathway. Here, we briefly review the underlying neuroanatomy of the corticofugal projections before discussing state of the art studies which demonstrate that SSA present in the medial geniculate body (MGB) and inferior colliculus (IC) is not inherited from the cortex but can be modulated by the cortex via the corticofugal pathways. By modulating the gain of neurons in the thalamus and midbrain, the auditory cortex (AC) would refine SSA subcortically, preventing irrelevant information from reaching the cortex.
Collapse
|
31
|
Malmierca MS, Young ED. Inferior colliculus microcircuits. Front Neural Circuits 2014; 8:113. [PMID: 25346661 PMCID: PMC4191209 DOI: 10.3389/fncir.2014.00113] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2013] [Accepted: 08/28/2014] [Indexed: 11/15/2022] Open
|
32
|
Duque D, Malmierca MS. Stimulus-specific adaptation in the inferior colliculus of the mouse: anesthesia and spontaneous activity effects. Brain Struct Funct 2014; 220:3385-98. [PMID: 25115620 DOI: 10.1007/s00429-014-0862-1] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2014] [Accepted: 07/29/2014] [Indexed: 12/19/2022]
Abstract
Rapid behavioral responses to unexpected events in the acoustic environment are critical for survival. Stimulus-specific adaptation (SSA) is the process whereby some auditory neurons respond better to rare stimuli than to repetitive stimuli. Most experiments on SSA have been performed under anesthesia, and it is unknown if SSA sensitivity is altered by the anesthetic agent. Only a direct comparison can answer this question. Here, we recorded extracellular single units in the inferior colliculus of awake and anesthetized mice under an oddball paradigm that elicits SSA. Our results demonstrate that SSA is similar, but not identical, in the awake and anesthetized preparations. The differences are mostly due to the higher spontaneous activity observed in the awake animals, which also revealed a high incidence of inhibitory receptive fields. We conclude that SSA is not an artifact of anesthesia and that spontaneous activity modulates neuronal SSA differentially, depending on the state of arousal. Our results suggest that SSA may be especially important when nervous system activity is suppressed during sleep-like states. This may be a useful survival mechanism that allows the organism to respond to danger when sleeping.
Collapse
|
33
|
Malmierca MS, Sanchez-Vives MV, Escera C, Bendixen A. Neuronal adaptation, novelty detection and regularity encoding in audition. Front Syst Neurosci 2014; 8:111. [PMID: 25009474 PMCID: PMC4068197 DOI: 10.3389/fnsys.2014.00111] [Citation(s) in RCA: 69] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2014] [Accepted: 05/24/2014] [Indexed: 11/19/2022] Open
Abstract
The ability to detect unexpected stimuli in the acoustic environment and determine their behavioral relevance to plan an appropriate reaction is critical for survival. This perspective article brings together several viewpoints and discusses current advances in understanding the mechanisms the auditory system implements to extract relevant information from incoming inputs and to identify unexpected events. This extraordinary sensitivity relies on the capacity to codify acoustic regularities, and is based on encoding properties that are present as early as the auditory midbrain. We review state-of-the-art studies on the processing of stimulus changes using non-invasive methods to record the summed electrical potentials in humans, and those that examine single-neuron responses in animal models. Human data will be based on mismatch negativity (MMN) and enhanced middle latency responses (MLR). Animal data will be based on the activity of single neurons at the cortical and subcortical levels, relating selective responses to novel stimuli to the MMN and to stimulus-specific neural adaptation (SSA). Theoretical models of the neural mechanisms that could create SSA and novelty responses will also be discussed.
Collapse
|
34
|
Pérez-González D, Malmierca MS. Adaptation in the auditory system: an overview. Front Integr Neurosci 2014; 8:19. [PMID: 24600361 PMCID: PMC3931124 DOI: 10.3389/fnint.2014.00019] [Citation(s) in RCA: 105] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2013] [Accepted: 02/05/2014] [Indexed: 11/13/2022] Open
Abstract
The early stages of the auditory system need to preserve the timing information of sounds in order to extract the basic features of acoustic stimuli. At the same time, different processes of neuronal adaptation occur at several levels to further process the auditory information. For instance, auditory nerve fiber responses already experience adaptation of their firing rates, a type of response that can be found in many other auditory nuclei and may be useful for emphasizing the onset of the stimuli. However, it is at higher levels in the auditory hierarchy where more sophisticated types of neuronal processing take place. For example, stimulus-specific adaptation, where neurons show adaptation to frequent, repetitive stimuli, but maintain their responsiveness to stimuli with different physical characteristics, thus representing a distinct kind of processing that may play a role in change and deviance detection. In the auditory cortex, adaptation takes more elaborate forms, and contributes to the processing of complex sequences, auditory scene analysis and attention. Here we review the multiple types of adaptation that occur in the auditory system, which are part of the pool of resources that the neurons employ to process the auditory scene, and are critical to a proper understanding of the neuronal mechanisms that govern auditory perception.
Collapse
|
35
|
Antunes FM, Malmierca MS. An Overview of Stimulus-Specific Adaptation in the Auditory Thalamus. Brain Topogr 2013; 27:480-99. [DOI: 10.1007/s10548-013-0342-6] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2013] [Accepted: 12/05/2013] [Indexed: 12/30/2022]
|
36
|
Escera C, Malmierca MS. The auditory novelty system: An attempt to integrate human and animal research. Psychophysiology 2013; 51:111-23. [DOI: 10.1111/psyp.12156] [Citation(s) in RCA: 106] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2013] [Accepted: 08/06/2013] [Indexed: 11/30/2022]
|
37
|
Duque D, Malmierca MS, Caspary DM. Modulation of stimulus-specific adaptation by GABA(A) receptor activation or blockade in the medial geniculate body of the anaesthetized rat. J Physiol 2013; 592:729-43. [PMID: 24099802 DOI: 10.1113/jphysiol.2013.261941] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Stimulus-specific adaptation (SSA), which describes adaptation to repeated sounds concurrent with the maintenance of responsiveness to uncommon ones, may be an important neuronal mechanism for the detection of and attendance to rare stimuli or for the detection of deviance. It is well known that GABAergic neurotransmission regulates several different response properties in central auditory system neurons and that GABA is the major inhibitory neurotransmitter acting in the medial geniculate body (MGB). The mechanisms underlying SSA are still poorly understood; therefore, the primary aim of the present study was to examine what role, if any, MGB GABAergic circuits play in the generation and/or modulation of SSA. Microiontophoretic activation of GABA(A) receptors (GABA(A)Rs) with GABA or with the selective GABA(A)R agonist gaboxadol significantly increased SSA (computed with the common SSA index, CSI) by decreasing responses to common stimuli while having a lesser effect on responses to novel stimuli. In contrast, GABA(A)R blockade using gabazine resulted in a significant decrease in SSA. In all cases, decreases in the CSI during gabazine application were accompanied by an increase in firing rate to the stimulus paradigm. The present findings, in conjunction with those of previous studies, suggest that GABA(A)-mediated inhibition does not generate the SSA response, but can regulate the level of SSA sensitivity in a gain control manner. The existence of successive hierarchical levels of processing through the auditory system suggests that the GABAergic circuits act to enhance mechanisms to reduce redundant information.
Collapse
|
38
|
Ayala YA, Malmierca MS. Stimulus-specific adaptation and deviance detection in the inferior colliculus. Front Neural Circuits 2013; 6:89. [PMID: 23335883 PMCID: PMC3547232 DOI: 10.3389/fncir.2012.00089] [Citation(s) in RCA: 66] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2012] [Accepted: 11/02/2012] [Indexed: 11/26/2022] Open
Abstract
Deviancy detection in the continuous flow of sensory information into the central nervous system is of vital importance for animals. The task requires neuronal mechanisms that allow for an efficient representation of the environment by removing statistically redundant signals. Recently, the neuronal principles of auditory deviance detection have been approached by studying the phenomenon of stimulus-specific adaptation (SSA). SSA is a reduction in the responsiveness of a neuron to a common or repetitive sound while the neuron remains highly sensitive to rare sounds (Ulanovsky et al., 2003). This phenomenon could enhance the saliency of unexpected, deviant stimuli against a background of repetitive signals. SSA shares many similarities with the evoked potential known as the “mismatch negativity,” (MMN) and it has been linked to cognitive process such as auditory memory and scene analysis (Winkler et al., 2009) as well as to behavioral habituation (Netser et al., 2011). Neurons exhibiting SSA can be found at several levels of the auditory pathway, from the inferior colliculus (IC) up to the auditory cortex (AC). In this review, we offer an account of the state-of-the art of SSA studies in the IC with the aim of contributing to the growing interest in the single-neuron electrophysiology of auditory deviance detection. The dependence of neuronal SSA on various stimulus features, e.g., probability of the deviant stimulus and repetition rate, and the roles of the AC and inhibition in shaping SSA at the level of the IC are addressed.
Collapse
|
39
|
Ayala YA, Pérez-González D, Duque D, Nelken I, Malmierca MS. Frequency discrimination and stimulus deviance in the inferior colliculus and cochlear nucleus. Front Neural Circuits 2013; 6:119. [PMID: 23335885 PMCID: PMC3544151 DOI: 10.3389/fncir.2012.00119] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2012] [Accepted: 12/19/2012] [Indexed: 11/17/2022] Open
Abstract
Auditory neurons that exhibit stimulus-specific adaptation (SSA) decrease their response to common tones while retaining responsiveness to rare ones. We recorded single-unit responses from the inferior colliculus (IC) where SSA is known to occur and we explored for the first time SSA in the cochlear nucleus (CN) of rats. We assessed an important functional outcome of SSA, the extent to which frequency discriminability depends on sensory context. For this purpose, pure tones were presented in an oddball sequence as standard (high probability of occurrence) or deviant (low probability of occurrence) stimuli. To study frequency discriminability under different probability contexts, we varied the probability of occurrence and the frequency separation between tones. The neuronal sensitivity was estimated in terms of spike-count probability using signal detection theory. We reproduced the finding that many neurons in the IC exhibited SSA, but we did not observe significant SSA in our CN sample. We concluded that strong SSA is not a ubiquitous phenomenon in the CN. As predicted, frequency discriminability was enhanced in IC when stimuli were presented in an oddball context, and this enhancement was correlated with the degree of SSA shown by the neurons. In contrast, frequency discrimination by CN neurons was independent of stimulus context. Our results demonstrated that SSA is not widespread along the entire auditory pathway, and suggest that SSA increases frequency discriminability of single neurons beyond that expected from their tuning curves.
Collapse
|
40
|
Pérez-González D, Malmierca MS. Variability of the time course of stimulus-specific adaptation in the inferior colliculus. Front Neural Circuits 2012; 6:107. [PMID: 23293586 PMCID: PMC3530767 DOI: 10.3389/fncir.2012.00107] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2012] [Accepted: 12/03/2012] [Indexed: 01/25/2023] Open
Abstract
Stimulus-specific adaptation (SSA) is the ability of some neurons to respond better to rare than to frequent, repetitive stimuli. In the auditory system, SSA has been found at the level of the midbrain, thalamus, and cortex. While previous studies have used the whole overall neuronal response to characterize SSA, here we present a detailed analysis on the variations within the time course of the evoked responses. The extracellular activity of well isolated single neurons from the inferior colliculus (IC) was recorded during stimulation using an oddball paradigm, which is able to elicit SSA. At the same time, these responses were evaluated before, during, and after the microiontophoretic application of gabazine, a specific antagonist of GABA(A) receptors, to study the contribution of inhibition to the responses of these neurons. We then analyzed the difference signal (DS), which is the difference in the PSTH in response to rare and frequent stimuli. We found that, even in a sample of neurons showing strong SSA (i.e., showing larger preference for rare stimuli), the DS was variable and one third of the neurons contained portions that responded significantly better to the frequent stimuli than to the rare. This variability is not observed when averaging the responses of multiple cells. Furthermore, the blockade of GABA(A) receptors increased the number of neurons showing portions that responded better to the frequent stimuli, indicating that inhibition in the IC refines and sharpens SSA in the neural responses.
Collapse
|
41
|
Pérez-González D, Hernández O, Covey E, Malmierca MS. GABA(A)-mediated inhibition modulates stimulus-specific adaptation in the inferior colliculus. PLoS One 2012; 7:e34297. [PMID: 22479591 PMCID: PMC3315508 DOI: 10.1371/journal.pone.0034297] [Citation(s) in RCA: 69] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2011] [Accepted: 02/28/2012] [Indexed: 01/27/2023] Open
Abstract
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 GABA(A)-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 GABA(A) receptors increased the firing rate to high and low probability stimuli, but did not completely equalize the responses. Together, these findings suggest that GABA(A)-mediated inhibition acts as a gain control mechanism that enhances SSA by modifying the responsiveness of the neuron.
Collapse
|
42
|
Oliver DL, Izquierdo MA, Malmierca MS. Persistent effects of early augmented acoustic environment on the auditory brainstem. Neuroscience 2011; 184:75-87. [PMID: 21496479 DOI: 10.1016/j.neuroscience.2011.04.001] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2010] [Revised: 03/31/2011] [Accepted: 04/01/2011] [Indexed: 10/18/2022]
Abstract
Acoustic experiences significantly shape the functional organization of the auditory cortex during postnatal "critical periods." Here, we investigate the effects of a non-traumatic augmented acoustic environment (AAE) on the central nucleus of the inferior colliculus (ICC) and lower brainstem nuclei in rat during the critical period. Our results show that an AAE during P9-P28 had a persistent effect on the evoked auditory brainstem responses leading to a decreased latency and an increased amplitude of the response at and above the frequency of the stimulus used for the AAE. These findings are correlated with increased numbers of sites in the ICC that responded to the AAE frequency and show higher thresholds. There also were persistent effects in neurons with a best frequency higher than the AAE stimulus. These neurons showed decreased activity at low sound levels in the low frequency tail of the frequency response area. This was at, below and above the AAE stimulus frequency. Less often, increased activity at higher sound levels also was seen. Together, these findings suggest multifaceted interactions between activity-dependent plasticity, homeostasis, and development in the brainstem during the initial stages of hearing. A neonate exposed to an altered auditory environment may experience long-lasting change over the entire network of the auditory system.
Collapse
|
43
|
Malmierca MS, Blackstad TW, Osen KK. Computer-assisted 3-D reconstructions of Golgi-impregnated neurons in the cortical regions of the inferior colliculus of rat. Hear Res 2011; 274:13-26. [DOI: 10.1016/j.heares.2010.06.011] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/13/2010] [Revised: 06/09/2010] [Accepted: 06/14/2010] [Indexed: 10/19/2022]
|
44
|
Antunes FM, Nelken I, Covey E, Malmierca MS. Stimulus-specific adaptation in the auditory thalamus of the anesthetized rat. PLoS One 2010; 5:e14071. [PMID: 21124913 PMCID: PMC2988819 DOI: 10.1371/journal.pone.0014071] [Citation(s) in RCA: 179] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2010] [Accepted: 10/29/2010] [Indexed: 11/18/2022] Open
Abstract
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.
Collapse
|
45
|
Malmierca MS, Hernández O, Antunes FM, Rees A. Divergent and point-to-point connections in the commissural pathway between the inferior colliculi. J Comp Neurol 2009; 514:226-39. [PMID: 19296464 PMCID: PMC2771101 DOI: 10.1002/cne.21997] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
The commissure of the inferior colliculus interconnects the left and right sides of the auditory midbrain and provides the final opportunity for interaction between the two sides of the auditory pathway at the subcortical level. Although the functional properties of the commissure are beginning to be revealed, the topographical organization of its connections is unknown. A combination of neuroanatomical tracing studies, 3D reconstruction, and neuronal density maps was used to study the commissural connections in rat. The results demonstrate that commissural neurons in the central nucleus of the inferior colliculus send a divergent projection to the equivalent frequency-band laminae in the central nucleus and dorsal and lateral cortices on the opposite side. The density of this projection, however, is weighted toward a point that matches the position of the tracer injection; consistent with a point-to-point emphasis in the wiring pattern. In the dorsal cortex of the inferior colliculus there may be two populations of neurons that project across the commissure, one projecting exclusively to the frequency-band laminae in the central nucleus and the other projecting diffusely to the dorsal cortex. Neurons in the lateral cortex of the inferior colliculus make only a very weak contribution to the commissural pathway. The point-to-point pattern of connections permits interactions between specific regions of corresponding frequency-band laminae, whereas the divergent projection pattern could subserve integration across the lamina. J. Comp. Neurol. 514:226–239, 2009. © 2009 Wiley-Liss, Inc.
Collapse
|
46
|
Izquierdo MA, Oliver DL, Malmierca MS. [Functional and activity-dependent plasticity mechanisms in the adult and developing auditory brain]. Rev Neurol 2009; 48:421-429. [PMID: 19340783 PMCID: PMC2916753] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
INTRODUCTION AND DEVELOPMENT Sensory systems show a topographic representation of the sensory epithelium in the central nervous system. In the auditory system this representation originates tonotopic maps. For the last four decades these changes in tonotopic maps have been widely studied either after peripheral mechanical lesions or by exposing animals to an augmented acoustic environment. These sensory manipulations induce plastic reorganizations in the tonotopic map of the auditory cortex. By contrast, acoustic trauma does not seem to induce functional plasticity at subcortical nuclei. Mechanisms that generate these changes differ in their molecular basis and temporal course and we can distinguish two different mechanisms: those involving an active reorganization process, and those that show a simple reflection of the loss of peripheral afferences. Only the former involve a genuine process of plastic reorganization. Neuronal plasticity is critical for the normal development and function of the adult auditory system, as well as for the rehabilitation needed after the implantation of auditory prostheses. However, development of plasticity can also generate abnormal sensation like tinnitus. Recently, a new concept in neurobiology so-called ‘neuronal stability’ has emerged and its implications and conceptual basis could help to improve the treatments of hearing loss. CONCLUSION A combination of neuronal plasticity and stability is suggested as a powerful and promising future strategy in the design of new treatments of hearing loss.
Collapse
|
47
|
Tolnai S, Hernandez O, Englitz B, Rübsamen R, Malmierca MS. The medial nucleus of the trapezoid body in rat: spectral and temporal properties vary with anatomical location of the units. Eur J Neurosci 2008; 27:2587-98. [DOI: 10.1111/j.1460-9568.2008.06228.x] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
|
48
|
Kopp-Scheinpflug C, Tolnai S, Malmierca MS, Rübsamen R. The medial nucleus of the trapezoid body: comparative physiology. Neuroscience 2008; 154:160-70. [PMID: 18436383 DOI: 10.1016/j.neuroscience.2008.01.088] [Citation(s) in RCA: 90] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2007] [Revised: 01/31/2008] [Accepted: 01/31/2008] [Indexed: 11/26/2022]
Abstract
Principal cells of the medial nucleus of the trapezoid body (MNTB) receive their excitatory input through large somatic terminals, the calyces of Held, which arise from axons of globular bushy cells located in the contralateral ventral cochlear nucleus. Discharges of MNTB neurons are characterized by high stimulus evoked firing rates, temporally precise onset responses, and a high degree of phase-locking to either pure tones or stimulus envelopes. Since the calyx of Held synapse is accessible to in vitro and to in vivo recordings, it serves as one of the most elaborate models for studying synaptic transmission in the mammalian brain. Although in such studies, the major emphasis is on synaptic physiology, the interpretation of the data will benefit from an understanding of the MNTB's contribution to auditory signal processing, including possible functional differences in different species. This implies the consideration of possible functional differences in different species. Here, we compare single unit recordings from MNTB principal cells in vivo in three different rodent species: gerbil, mouse and rat. Because of their good low-frequency hearing gerbils are often used in in vivo preparations, while mice and rats are predominantly used in slice preparations. We show that MNTB units in all three species exhibit high firing rates and precise onset-timing. Still there are species-specific specializations that might suggest the preferential use of one species over the others, depending on the scope of the respective investigation.
Collapse
|
49
|
Loftus WC, Malmierca MS, Bishop DC, Oliver DL. The cytoarchitecture of the inferior colliculus revisited: a common organization of the lateral cortex in rat and cat. Neuroscience 2008; 154:196-205. [PMID: 18313229 DOI: 10.1016/j.neuroscience.2008.01.019] [Citation(s) in RCA: 95] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2007] [Revised: 12/27/2007] [Accepted: 01/02/2008] [Indexed: 11/19/2022]
Abstract
The inferior colliculus (IC) is the major component of the auditory midbrain and contains three major subdivisions: a central nucleus, a dorsal cortex, and a lateral cortex (LC). Discrepancies in the nomenclature and parcellation of the LC in the rat and cat seem to imply different, species-specific functions for this region. To establish a comparable parcellation of the LC for both rat and cat, we investigated its histochemistry and inputs. In both species, the deep lateral cortex is marked by a transition between the nicotinamide adenine dinucleotide phosphate-diaphorase (NADPH-d) rich superficial cortex and a cytochrome oxidase (CO) rich central nucleus. In both species, focal injections of anterograde tracers in the cochlear nucleus at sites of known best frequency produced bands of labeled inputs in two different subdivisions of the IC. A medial band of axons terminated in the central nucleus, while shorter bands were located laterally and oriented nearly perpendicularly to the medial bands. In the rat, these lateral bands were located in the third, deepest layer of the lateral (external) cortex. In the cat, the bands were located in a region that was previously ascribed to the central nucleus, but now considered to belong to the third, deepest layer of the LC, the ventrolateral nucleus. In both species, the LC inputs had a tonotopic organization. In view of this parallel organization, we propose a common parcellation of the IC for rat and cat with a new nomenclature. The deep layer of the LC, previously referred to as layer 3 in the rat, is designated as the 'ventrolateral nucleus' of the LC, making it clear that this region is thought to be homologous with the ventrolateral nucleus in the cat. The similar organization of the LC implies that this subdivision of the IC has similar functions in cats and rats.
Collapse
|
50
|
Pérez-González D, Covey E, Malmierca MS. [Detection of novel sounds. Multiple manifestations of the same phenomenon?]. Rev Neurol 2008; 46:102-108. [PMID: 18247282] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
INTRODUCTION Detection of novel sounds must be a basic function of the auditory system, but the underlying neuronal mechanisms are largely unknown. DEVELOPMENT During repetitive stimulation or a monotonous auditory scene, many auditory neurons show a decrease in their response, presumably due to adaptation. However, these neurons are able to recover and respond again any time there is a change in the stimuli. This process is known as stimulus-specific adaptation (SSA), and could be the basis of the neuronal mechanism for change detection. Neurons showing SSA have been reported both in auditory cortex and subcortical regions, such as the inferior colliculus. Neurons that experience SSA at all levels could be involved in a change detection circuit, but the relationship between neurons in different areas is still unclear. SSA, as found in these neurons, shares a number of characteristics with mismatch negativity (MMN), a component of evoked potentials related to the detection of context novelty, and linked to some processes that involve memory and attention. CONCLUSIONS The responses to changes in sounds can be observed in multiple ways, ranging from the activity of single neurons to evoked potential recordings. The phenomena observed using these different approaches appear to be manifestations of the same underlying sensory process, which would involve both cortical and subcortical auditory nuclei, and could have its basis in stimulus-specific neuronal adaptation.
Collapse
|