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Weible AP, Yavorska I, Wehr M. A Cortico-Collicular Amplification Mechanism for Gap Detection. Cereb Cortex 2020; 30:3590-3607. [PMID: 32055848 DOI: 10.1093/cercor/bhz328] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Abstract
Auditory cortex (AC) is necessary for the detection of brief gaps in ongoing sounds, but not for the detection of longer gaps or other stimuli such as tones or noise. It remains unclear why this is so, and what is special about brief gaps in particular. Here, we used both optogenetic suppression and conventional lesions to show that the cortical dependence of brief gap detection hinges specifically on gap termination. We then identified a cortico-collicular gap detection circuit that amplifies cortical gap termination responses before projecting to inferior colliculus (IC) to impact behavior. We found that gaps evoked off-responses and on-responses in cortical neurons, which temporally overlapped for brief gaps, but not long gaps. This overlap specifically enhanced cortical responses to brief gaps, whereas IC neurons preferred longer gaps. Optogenetic suppression of AC reduced collicular responses specifically to brief gaps, indicating that under normal conditions, the enhanced cortical representation of brief gaps amplifies collicular gap responses. Together these mechanisms explain how and why AC contributes to the behavioral detection of brief gaps, which are critical cues for speech perception, perceptual grouping, and auditory scene analysis.
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Affiliation(s)
- Aldis P Weible
- Department of Psychology, Institute of Neuroscience, 1254 University of Oregon, Eugene, OR 97403, USA
| | - Iryna Yavorska
- Department of Psychology, Institute of Neuroscience, 1254 University of Oregon, Eugene, OR 97403, USA
| | - Michael Wehr
- Department of Psychology, Institute of Neuroscience, 1254 University of Oregon, Eugene, OR 97403, USA
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2
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Zurita H, Rock C, Perkins J, Apicella AJ. A Layer-specific Corticofugal Input to the Mouse Superior Colliculus. Cereb Cortex 2019; 28:2817-2833. [PMID: 29077796 DOI: 10.1093/cercor/bhx161] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2017] [Accepted: 06/08/2017] [Indexed: 12/16/2022] Open
Abstract
In the auditory cortex (AC), corticofugal projections arise from each level of the auditory system and are considered to provide feedback "loops" important to modulate the flow of ascending information. It is well established that the cortex can influence the response of neurons in the superior colliculus (SC) via descending corticofugal projections. However, little is known about the relative contribution of different pyramidal neurons to these projections in the SC. We addressed this question by taking advantage of anterograde and retrograde neuronal tracing to directly examine the laminar distribution, long-range projections, and electrophysiological properties of pyramidal neurons projecting from the AC to the SC of the mouse brain. Here we show that layer 5 cortico-superior-collicular pyramidal neurons act as bandpass filters, resonating with a broad peak at ∼3 Hz, whereas layer 6 neurons act as low-pass filters. The dissimilar subthreshold properties of layer 5 and layer 6 cortico-superior-collicular pyramidal neurons can be described by differences in the hyperpolarization-activated cyclic nucleotide-gated cation h-current (Ih). Ih also reduced the summation of short trains of artificial excitatory postsynaptic potentials injected at the soma of layer 5, but not layer 6, cortico-superior-collicular pyramidal neurons, indicating a differential dampening effect of Ih on these neurons.
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Affiliation(s)
- Hector Zurita
- Department of Biology, Neuroscience Institute, University of Texas at San Antonio, San Antonio, TX, USA
| | - Crystal Rock
- Department of Biology, Neuroscience Institute, University of Texas at San Antonio, San Antonio, TX, USA
| | - Jessica Perkins
- Department of Biology, Neuroscience Institute, University of Texas at San Antonio, San Antonio, TX, USA
| | - Alfonso Junior Apicella
- Department of Biology, Neuroscience Institute, University of Texas at San Antonio, San Antonio, TX, USA
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3
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Lohse M, Bajo VM, King AJ. Development, organization and plasticity of auditory circuits: Lessons from a cherished colleague. Eur J Neurosci 2018; 49:990-1004. [PMID: 29804304 PMCID: PMC6519211 DOI: 10.1111/ejn.13979] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2018] [Revised: 05/11/2018] [Accepted: 05/23/2018] [Indexed: 12/20/2022]
Abstract
Ray Guillery was a neuroscientist known primarily for his ground-breaking studies on the development of the visual pathways and subsequently on the nature of thalamocortical processing loops. The legacy of his work, however, extends well beyond the visual system. Thanks to Ray Guillery's pioneering anatomical studies, the ferret has become a widely used animal model for investigating the development and plasticity of sensory processing. This includes our own work on the auditory system, where experiments in ferrets have revealed the role of sensory experience during development in shaping the neural circuits responsible for sound localization, as well as the capacity of the mature brain to adapt to changes in inputs resulting from hearing loss. Our research has also built on Ray Guillery's ideas about the possible functions of the massive descending projections that link sensory areas of the cerebral cortex to the thalamus and other subcortical targets, by demonstrating a role for corticothalamic feedback in the perception of complex sounds and for corticollicular projection neurons in learning to accommodate altered auditory spatial cues. Finally, his insights into the organization and functions of transthalamic corticocortical connections have inspired a raft of research, including by our own laboratory, which has attempted to identify how information flows through the thalamus.
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Affiliation(s)
- Michael Lohse
- Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, UK
| | - Victoria M Bajo
- Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, UK
| | - Andrew J King
- Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, UK
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4
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Hammond‐Kenny A, Bajo VM, King AJ, Nodal FR. Behavioural benefits of multisensory processing in ferrets. Eur J Neurosci 2017; 45:278-289. [PMID: 27740711 PMCID: PMC5298019 DOI: 10.1111/ejn.13440] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2016] [Revised: 09/22/2016] [Accepted: 10/10/2016] [Indexed: 12/29/2022]
Abstract
Enhanced detection and discrimination, along with faster reaction times, are the most typical behavioural manifestations of the brain's capacity to integrate multisensory signals arising from the same object. In this study, we examined whether multisensory behavioural gains are observable across different components of the localization response that are potentially under the command of distinct brain regions. We measured the ability of ferrets to localize unisensory (auditory or visual) and spatiotemporally coincident auditory-visual stimuli of different durations that were presented from one of seven locations spanning the frontal hemifield. During the localization task, we recorded the head movements made following stimulus presentation, as a metric for assessing the initial orienting response of the ferrets, as well as the subsequent choice of which target location to approach to receive a reward. Head-orienting responses to auditory-visual stimuli were more accurate and faster than those made to visual but not auditory targets, suggesting that these movements were guided principally by sound alone. In contrast, approach-to-target localization responses were more accurate and faster to spatially congruent auditory-visual stimuli throughout the frontal hemifield than to either visual or auditory stimuli alone. Race model inequality analysis of head-orienting reaction times and approach-to-target response times indicates that different processes, probability summation and neural integration, respectively, are likely to be responsible for the effects of multisensory stimulation on these two measures of localization behaviour.
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Affiliation(s)
- Amy Hammond‐Kenny
- Department of Physiology, Anatomy and GeneticsUniversity of OxfordOxfordOX1 3PTUK
| | - Victoria M. Bajo
- Department of Physiology, Anatomy and GeneticsUniversity of OxfordOxfordOX1 3PTUK
| | - Andrew J. King
- Department of Physiology, Anatomy and GeneticsUniversity of OxfordOxfordOX1 3PTUK
| | - Fernando R. Nodal
- Department of Physiology, Anatomy and GeneticsUniversity of OxfordOxfordOX1 3PTUK
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5
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Green DB, Ohlemacher J, Rosen MJ. Benefits of Stimulus Exposure: Developmental Learning Independent of Task Performance. Front Neurosci 2016; 10:263. [PMID: 27378837 PMCID: PMC4911416 DOI: 10.3389/fnins.2016.00263] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2015] [Accepted: 05/24/2016] [Indexed: 12/22/2022] Open
Abstract
Perceptual learning (training-induced performance improvement) can be elicited by task-irrelevant stimulus exposure in humans. In contrast, task-irrelevant stimulus exposure in animals typically disrupts perception in juveniles while causing little to no effect in adults. This may be due to the extent of exposure, which is brief in humans while chronic in animals. Here we assessed the effects of short bouts of passive stimulus exposure on learning during development in gerbils, compared with non-passive stimulus exposure (i.e., during testing). We used prepulse inhibition of the acoustic startle response, a method that can be applied at any age, to measure gap detection thresholds across four age groups, spanning development. First, we showed that both gap detection thresholds and gap detection learning across sessions displayed a long developmental trajectory, improving throughout the juvenile period. Additionally, we demonstrated larger within- and across-animal performance variability in younger animals. These results are generally consistent with results in humans, where there are extended developmental trajectories for both the perception of temporally-varying signals, and the effects of perceptual training, as well as increased variability and poorer performance consistency in children. We then chose an age (mid-juveniles) that displayed clear learning over sessions in order to assess effects of brief passive stimulus exposure on this learning. We compared learning in mid-juveniles exposed to either gap detection testing (gaps paired with startles) or equivalent gap exposure without testing (gaps alone) for three sessions. Learning was equivalent in both these groups and better than both naïve age-matched animals and controls receiving no gap exposure but only startle testing. Thus, short bouts of exposure to gaps independent of task performance is sufficient to induce learning at this age, and is as effective as gap detection testing.
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Affiliation(s)
| | | | - Merri J. Rosen
- Department of Anatomy and Neurobiology, Northeast Ohio Medical UniversityRootstown, OH, USA
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6
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Abstract
This study investigated auditory stimulus selectivity in the midbrain superior colliculus (SC) of the echolocating bat, an animal that relies on hearing to guide its orienting behaviors. Multichannel, single-unit recordings were taken across laminae of the midbrain SC of the awake, passively listening big brown bat, Eptesicus fuscus. Species-specific frequency-modulated (FM) echolocation sound sequences with dynamic spectrotemporal features served as acoustic stimuli along with artificial sound sequences matched in bandwidth, amplitude, and duration but differing in spectrotemporal structure. Neurons in dorsal sensory regions of the bat SC responded selectively to elements within the FM sound sequences, whereas neurons in ventral sensorimotor regions showed broad response profiles to natural and artificial stimuli. Moreover, a generalized linear model (GLM) constructed on responses in the dorsal SC to artificial linear FM stimuli failed to predict responses to natural sounds and vice versa, but the GLM produced accurate response predictions in ventral SC neurons. This result suggests that auditory selectivity in the dorsal extent of the bat SC arises through nonlinear mechanisms, which extract species-specific sensory information. Importantly, auditory selectivity appeared only in responses to stimuli containing the natural statistics of acoustic signals used by the bat for spatial orientation-sonar vocalizations-offering support for the hypothesis that sensory selectivity enables rapid species-specific orienting behaviors. The results of this study are the first, to our knowledge, to show auditory spectrotemporal selectivity to natural stimuli in SC neurons and serve to inform a more general understanding of mechanisms guiding sensory selectivity for natural, goal-directed orienting behaviors.
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Gold JR, Nodal FR, Peters F, King AJ, Bajo VM. Auditory gap-in-noise detection behavior in ferrets and humans. Behav Neurosci 2015; 129:473-90. [PMID: 26052794 PMCID: PMC4516322 DOI: 10.1037/bne0000065] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2014] [Revised: 03/06/2015] [Accepted: 04/10/2015] [Indexed: 12/24/2022]
Abstract
The precise encoding of temporal features of auditory stimuli by the mammalian auditory system is critical to the perception of biologically important sounds, including vocalizations, speech, and music. In this study, auditory gap-detection behavior was evaluated in adult pigmented ferrets (Mustelid putorius furo) using bandpassed stimuli designed to widely sample the ferret's behavioral and physiological audiogram. Animals were tested under positive operant conditioning, with psychometric functions constructed in response to gap-in-noise lengths ranging from 3 to 270 ms. Using a modified version of this gap-detection task, with the same stimulus frequency parameters, we also tested a cohort of normal-hearing human subjects. Gap-detection thresholds were computed from psychometric curves transformed according to signal detection theory, revealing that for both ferrets and humans, detection sensitivity was worse for silent gaps embedded within low-frequency noise compared with high-frequency or broadband stimuli. Additional psychometric function analysis of ferret behavior indicated effects of stimulus spectral content on aspects of behavioral performance related to decision-making processes, with animals displaying improved sensitivity for broadband gap-in-noise detection. Reaction times derived from unconditioned head-orienting data and the time from stimulus onset to reward spout activation varied with the stimulus frequency content and gap length, as well as the approach-to-target choice and reward location. The present study represents a comprehensive evaluation of gap-detection behavior in ferrets, while similarities in performance with our human subjects confirm the use of the ferret as an appropriate model of temporal processing.
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Affiliation(s)
- Joshua R Gold
- Department of Physiology, Anatomy, and Genetics, University of Oxford
| | - Fernando R Nodal
- Department of Physiology, Anatomy, and Genetics, University of Oxford
| | - Fabian Peters
- Department of Physiology, Anatomy, and Genetics, University of Oxford
| | - Andrew J King
- Department of Physiology, Anatomy, and Genetics, University of Oxford
| | - Victoria M Bajo
- Department of Physiology, Anatomy, and Genetics, University of Oxford
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8
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Wolf AB, Lintz MJ, Costabile JD, Thompson JA, Stubblefield EA, Felsen G. An integrative role for the superior colliculus in selecting targets for movements. J Neurophysiol 2015. [PMID: 26203103 DOI: 10.1152/jn.00262.2015] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
A fundamental goal of systems neuroscience is to understand the neural mechanisms underlying decision making. The midbrain superior colliculus (SC) is known to be central to the selection of one among many potential spatial targets for movements, which represents an important form of decision making that is tractable to rigorous experimental investigation. In this review, we first discuss data from mammalian models-including primates, cats, and rodents-that inform our understanding of how neural activity in the SC underlies the selection of targets for movements. We then examine the anatomy and physiology of inputs to the SC from three key regions that are themselves implicated in motor decisions-the basal ganglia, parabrachial region, and neocortex-and discuss how they may influence SC activity related to target selection. Finally, we discuss the potential for methodological advances to further our understanding of the neural bases of target selection. Our overarching goal is to synthesize what is known about how the SC and its inputs act together to mediate the selection of targets for movements, to highlight open questions about this process, and to spur future studies addressing these questions.
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Affiliation(s)
- Andrew B Wolf
- Department of Physiology and Biophysics, University of Colorado School of Medicine, Aurora, Colorado; Neuroscience Program, University of Colorado School of Medicine, Aurora, Colorado; Medical Scientist Training Program, University of Colorado School of Medicine, Aurora, Colorado; and
| | - Mario J Lintz
- Department of Physiology and Biophysics, University of Colorado School of Medicine, Aurora, Colorado; Neuroscience Program, University of Colorado School of Medicine, Aurora, Colorado; Medical Scientist Training Program, University of Colorado School of Medicine, Aurora, Colorado; and
| | - Jamie D Costabile
- Department of Physiology and Biophysics, University of Colorado School of Medicine, Aurora, Colorado
| | - John A Thompson
- Department of Neurosurgery, University of Colorado School of Medicine, Aurora, Colorado
| | - Elizabeth A Stubblefield
- Department of Physiology and Biophysics, University of Colorado School of Medicine, Aurora, Colorado
| | - Gidon Felsen
- Department of Physiology and Biophysics, University of Colorado School of Medicine, Aurora, Colorado; Neuroscience Program, University of Colorado School of Medicine, Aurora, Colorado; Medical Scientist Training Program, University of Colorado School of Medicine, Aurora, Colorado; and
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9
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Bizley JK, Bajo VM, Nodal FR, King AJ. Cortico-Cortical Connectivity Within Ferret Auditory Cortex. J Comp Neurol 2015; 523:2187-210. [PMID: 25845831 PMCID: PMC4737260 DOI: 10.1002/cne.23784] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2014] [Revised: 03/29/2015] [Accepted: 04/01/2015] [Indexed: 12/29/2022]
Abstract
Despite numerous studies of auditory cortical processing in the ferret (Mustela putorius), very little is known about the connections between the different regions of the auditory cortex that have been characterized cytoarchitectonically and physiologically. We examined the distribution of retrograde and anterograde labeling after injecting tracers into one or more regions of ferret auditory cortex. Injections of different tracers at frequency‐matched locations in the core areas, the primary auditory cortex (A1) and anterior auditory field (AAF), of the same animal revealed the presence of reciprocal connections with overlapping projections to and from discrete regions within the posterior pseudosylvian and suprasylvian fields (PPF and PSF), suggesting that these connections are frequency specific. In contrast, projections from the primary areas to the anterior dorsal field (ADF) on the anterior ectosylvian gyrus were scattered and non‐overlapping, consistent with the non‐tonotopic organization of this field. The relative strength of the projections originating in each of the primary fields differed, with A1 predominantly targeting the posterior bank fields PPF and PSF, which in turn project to the ventral posterior field, whereas AAF projects more heavily to the ADF, which then projects to the anteroventral field and the pseudosylvian sulcal cortex. These findings suggest that parallel anterior and posterior processing networks may exist, although the connections between different areas often overlap and interactions were present at all levels. J. Comp. Neurol. 523:2187–2210, 2015. © 2015 Wiley Periodicals, Inc.
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Affiliation(s)
- Jennifer K Bizley
- Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, OX1 3PT, United Kingdom.,Ear Institute, University College London, London, WC1X 8EE, United Kingdom
| | - Victoria M Bajo
- Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, OX1 3PT, United Kingdom
| | | | - Andrew J King
- Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, OX1 3PT, United Kingdom
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10
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Lee CC. Two types of auditory glutamatergic synapses and their implications for repairing damaged central auditory pathways. Neural Regen Res 2014; 9:1000-2. [PMID: 25206751 PMCID: PMC4146298 DOI: 10.4103/1673-5374.133158] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/24/2014] [Indexed: 11/04/2022] Open
Affiliation(s)
- Charles C Lee
- Department of Comparative Biomedical Sciences, School of Veterinary Medicine, Louisiana State University, Baton Rouge, LA 70803, USA
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11
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Foxworthy WA, Clemo HR, Meredith MA. Laminar and connectional organization of a multisensory cortex. J Comp Neurol 2013; 521:1867-90. [PMID: 23172137 DOI: 10.1002/cne.23264] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2012] [Revised: 08/07/2012] [Accepted: 11/06/2012] [Indexed: 11/07/2022]
Abstract
The transformation of sensory signals as they pass through cortical circuits has been revealed almost exclusively through studies of the primary sensory cortices, for which principles of laminar organization, local connectivity, and parallel processing have been elucidated. In contrast, almost nothing is known about the circuitry or laminar features of multisensory processing in higher order, multisensory cortex. Therefore, using the ferret higher order multisensory rostral posterior parietal (PPr) cortex, the present investigation employed a combination of multichannel recording and neuroanatomical techniques to elucidate the laminar basis of multisensory cortical processing. The proportion of multisensory neurons, the share of neurons showing multisensory integration, and the magnitude of multisensory integration were all found to differ by layer in a way that matched the functional or connectional characteristics of the PPr. Specifically, the supragranular layers (L2/3) demonstrated among the highest proportions of multisensory neurons and the highest incidence of multisensory response enhancement, while also receiving the highest levels of extrinsic inputs, exhibiting the highest dendritic spine densities, and providing a major source of local connectivity. In contrast, layer 6 showed the highest proportion of unisensory neurons while receiving the fewest external and local projections and exhibiting the lowest dendritic spine densities. Coupled with a lack of input from principal thalamic nuclei and a minimal layer 4, these observations indicate that this higher level multisensory cortex shows functional and organizational modifications from the well-known patterns identified for primary sensory cortical regions.
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Affiliation(s)
- W Alex Foxworthy
- Department of Anatomy and Neurobiology, Virginia Commonwealth University School of Medicine, Richmond, Virginia 23298, USA
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12
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Aparicio MA, Saldaña E. The dorsal tectal longitudinal column (TLCd): a second longitudinal column in the paramedian region of the midbrain tectum. Brain Struct Funct 2013; 219:607-30. [PMID: 23468089 PMCID: PMC3933748 DOI: 10.1007/s00429-013-0522-x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2012] [Accepted: 02/08/2013] [Indexed: 11/03/2022]
Abstract
The tectal longitudinal column (TLC) is a longitudinally oriented, long and narrow nucleus that spans the paramedian region of the midbrain tectum of a large variety of mammals (Saldaña et al. in J Neurosci 27:13108–13116, 2007). Recent analysis of the organization of this region revealed another novel nucleus located immediately dorsal, and parallel, to the TLC. Because the name “tectal longitudinal column” also seems appropriate for this novel nucleus, we suggest the TLC described in 2007 be renamed the “ventral tectal longitudinal column (TLCv)”, and the newly discovered nucleus termed the “dorsal tectal longitudinal column (TLCd)”. This work represents the first characterization of the rat TLCd. A constellation of anatomical techniques was used to demonstrate that the TLCd differs from its surrounding structures (TLCv and superior colliculus) cytoarchitecturally, myeloarchitecturally, neurochemically and hodologically. The distinct expression of vesicular amino acid transporters suggests that TLCd neurons are GABAergic. The TLCd receives major projections from various areas of the cerebral cortex (secondary visual mediomedial area, and granular and dysgranular retrosplenial cortices) and from the medial pretectal nucleus. It densely innervates the ipsilateral lateral posterior and laterodorsal nuclei of the thalamus. Thus, the TLCd is connected with vision-related neural centers. The TLCd may be unique as it constitutes the only known nucleus made of GABAergic neurons dedicated to providing massive inhibition to higher order thalamic nuclei of a specific sensory modality.
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Affiliation(s)
- M-Auxiliadora Aparicio
- Department of Cell Biology and Pathology, Medical School, University of Salamanca, 37007, Salamanca, Spain
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13
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Bajo VM, King AJ. Cortical modulation of auditory processing in the midbrain. Front Neural Circuits 2013; 6:114. [PMID: 23316140 PMCID: PMC3539853 DOI: 10.3389/fncir.2012.00114] [Citation(s) in RCA: 78] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2012] [Accepted: 12/11/2012] [Indexed: 11/13/2022] Open
Abstract
In addition to their ascending pathways that originate at the receptor cells, all sensory systems are characterized by extensive descending projections. Although the size of these connections often outweighs those that carry information in the ascending auditory pathway, we still have a relatively poor understanding of the role they play in sensory processing. In the auditory system one of the main corticofugal projections links layer V pyramidal neurons with the inferior colliculus (IC) in the midbrain. All auditory cortical fields contribute to this projection, with the primary areas providing the largest outputs to the IC. In addition to medium and large pyramidal cells in layer V, a variety of cell types in layer VI make a small contribution to the ipsilateral corticocollicular projection. Cortical neurons innervate the three IC subdivisions bilaterally, although the contralateral projection is relatively small. The dorsal and lateral cortices of the IC are the principal targets of corticocollicular axons, but input to the central nucleus has also been described in some studies and is distinctive in its laminar topographic organization. Focal electrical stimulation and inactivation studies have shown that the auditory cortex can modify almost every aspect of the response properties of IC neurons, including their sensitivity to sound frequency, intensity, and location. Along with other descending pathways in the auditory system, the corticocollicular projection appears to continually modulate the processing of acoustical signals at subcortical levels. In particular, there is growing evidence that these circuits play a critical role in the plasticity of neural processing that underlies the effects of learning and experience on auditory perception by enabling changes in cortical response properties to spread to subcortical nuclei.
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Affiliation(s)
- Victoria M. Bajo
- Department of Physiology, Anatomy and Genetics, University of OxfordOxford, UK
| | - Andrew J. King
- Department of Physiology, Anatomy and Genetics, University of OxfordOxford, UK
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14
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Merchán MA, Saldaña E, Oliver DL. Auditory neuroanatomy: a sound foundation for sound processing. Front Neuroanat 2012; 6:48. [PMID: 23230396 PMCID: PMC3515782 DOI: 10.3389/fnana.2012.00048] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2012] [Accepted: 11/21/2012] [Indexed: 11/30/2022] Open
Affiliation(s)
- Miguel A Merchán
- Laboratory 6, Neuroscience Institute of Castilla y León, Universidad de Salamanca Salamanca, Spain
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15
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Nodal FR, Bajo VM, King AJ. Plasticity of spatial hearing: behavioural effects of cortical inactivation. J Physiol 2012; 590:3965-86. [PMID: 22547635 PMCID: PMC3464400 DOI: 10.1113/jphysiol.2011.222828] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
The contribution of auditory cortex to spatial information processing was explored behaviourally in adult ferrets by reversibly deactivating different cortical areas by subdural placement of a polymer that released the GABAA agonist muscimol over a period of weeks. The spatial extent and time course of cortical inactivation were determined electrophysiologically. Muscimol-Elvax was placed bilaterally over the anterior (AEG), middle (MEG) or posterior ectosylvian gyrus (PEG), so that different regions of the auditory cortex could be deactivated in different cases. Sound localization accuracy in the horizontal plane was assessed by measuring both the initial head orienting and approach-to-target responses made by the animals. Head orienting behaviour was unaffected by silencing any region of the auditory cortex, whereas the accuracy of approach-to-target responses to brief sounds (40 ms noise bursts) was reduced by muscimol-Elvax but not by drug-free implants. Modest but significant localization impairments were observed after deactivating the MEG, AEG or PEG, although the largest deficits were produced in animals in which the MEG, where the primary auditory fields are located, was silenced. We also examined experience-induced spatial plasticity by reversibly plugging one ear. In control animals, localization accuracy for both approach-to-target and head orienting responses was initially impaired by monaural occlusion, but recovered with training over the next few days. Deactivating any part of the auditory cortex resulted in less complete recovery than in controls, with the largest deficits observed after silencing the higher-level cortical areas in the AEG and PEG. Although suggesting that each region of auditory cortex contributes to spatial learning, differences in the localization deficits and degree of adaptation between groups imply a regional specialization in the processing of spatial information across the auditory cortex.
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Affiliation(s)
- Fernando R Nodal
- Department of Physiology, Anatomy and Genetics, Sherrington Building, University of Oxford, Parks Road, Oxford OX1 3PT, UK.
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16
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Paulussen M, Arckens L. Striking neuronal thymosin beta 4 expression in the deep layers of the mouse superior colliculus after monocular deprivation. Brain Struct Funct 2011; 217:81-91. [DOI: 10.1007/s00429-011-0330-0] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2011] [Accepted: 05/11/2011] [Indexed: 11/30/2022]
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