Corticofugal Modulation on Both on andoff Responses in the Nonlemniscal Auditory Thalamus of the Guinea Pig

2003 ◽  
Vol 89 (1) ◽  
pp. 367-381 ◽  
Author(s):  
Jufang He
Keyword(s):  
Auditory Cortex ◽  
Inhibitory Effect ◽  
Border Region ◽  
Cortical Activation ◽  
Facilitatory Effect ◽  
Auditory Signal ◽  
Inhibitory Input ◽  
Auditory Information ◽  
Medial Geniculate ◽  
Corticofugal Modulation

Corticofugal modulation on both on andoff responses in various nuclei in the medial geniculate body (MGB) was examined by locally activating the auditory cortex and looking for effects on the neuronal responses to acoustic stimuli. In contrast with a major corticofugal facilitatory effect on theon neurons in the lemniscal nucleus of the MGB of the guinea pigs, of 132 on neurons tested in three conditions with cortical activation through each of three implanted electrodes, the majority of the tested conditions (319/396) that were sampled from the nonlemniscal nuclei of the MGB received inhibitory modulation from the activated cortex. This inhibitory effect was >50% for 99 cases while the auditory cortex was activated. Most of the offand on-off MGB neurons (44/54) showed a facilitatory effect of 111.4 ± 99.9%, and three showed a small inhibitory effect of 25.7 ± 5.8% on their off responses. Thirty neurons in the border region between the lemniscal and nonlemniscal MGB showed mainly facilitatory corticofugal effects on both on andoff responses. Meanwhile, cortical stimulation induced almost exclusive inhibitory effects on the on response and facilitatory effects on the off response in the MGcm. It is suggested that the off response is produced as a disinhibition from the inhibitory input of the auditory stimulus. The present results provide a possible explanation for selective gating of the auditory information through the lemniscal MGB while switching off other unwanted sensory signals and the interference from the limbic system, leaving the other auditory cortex prepared to process only the auditory signal.

Modulatory Effect of Cortical Activation on the Lemniscal Auditory Thalamus of the Guinea Pig

2002 ◽  
Vol 88 (2) ◽  
pp. 1040-1050 ◽  
Author(s):  
Jufang He ◽  
Yan-Qin Yu ◽  
Ying Xiong ◽  
Tsutomu Hashikawa ◽  
Ying-Shing Chan
Keyword(s):  
Guinea Pig ◽  
Auditory Cortex ◽  
Firing Pattern ◽  
Inhibitory Effect ◽  
Electrical Activation ◽  
Facilitatory Effect ◽  
Thalamic Neurons ◽  
Auditory Thalamus ◽  
Medial Geniculate ◽  
Corticofugal Modulation

In the present study, we investigated the point-to-point modulatory effects from the auditory cortex to the thalamus in the guinea pig. Corticofugal modulation on thalamic neurons was studied by electrical activation of the auditory cortex. The modulation effect was sampled along the frontal or sagittal planes of the auditory thalamus, focusing on the ventral division (MGv) of the medial geniculate body (MGB). Electrical activation was targeted at the anterior and dorsocaudal auditory fields, to which the MGv projects and from which it assumptively receives reciprocal projections. Of the 101 MGv neurons examined by activation of the auditory cortex through passing pulse trains of 100–200 μA current into one after another of the three implanted electrodes (101 neurons × 3 stimulation sites = 303 cases), 208 cases showed a facilitatory effect, 85 showed no effect, and only 10 cases (7 neurons) showed an inhibitory effect. Among the cases of facilitation, 63 cases showed a facilitatory effect >100%, and 145 cases showed a facilitatory effect from 20–100%. The corticofugal modulatory effect on the MGv of the guinea pig showed a widespread, strong facilitatory effect and very little inhibitory effect. The MGv neurons showed the greatest facilitations to stimulation by the cortical sites, with the closest correspondence in BF. Six of seven neurons showed an elevation of the rate-frequency functions when the auditory cortex was activated. The comparative results of the corticofugal modulatory effects on the MGv of the guinea pig and the cat, together with anatomical findings, hint that the strong facilitatory effect is generated through the strong corticothalamic direct connection and that the weak inhibitory effect might be mainly generated via the interneurons of the MGv. The temporal firing pattern of neuronal response to auditory stimulus was also modulated by cortical stimulation. The mean first-spike latency increased significantly from 15.7 ± 5.3 ms with only noise-burst stimulus to 18.3 ± 4.9 ms ( n = 5, P < 0.01, paired t-test), while the auditory cortex was activated with a train of 10 pulses. Taking these results together with those of previous experiments conducted on the cat, we speculate that the relatively weaker inhibitory effect compared with that in the cat could be due to the smaller number of interneurons in the guinea pig MGB. The corticofugal modulation of the firing pattern of the thalamic neurons might enable single neurons to encode more auditory information using not only the firing rate but also the firing pattern.

scholarly journals Modulatory Effects of Regional Cortical Activation on the Onset Responses of the Cat Medial Geniculate Neurons

1997 ◽  
Vol 77 (2) ◽  
pp. 896-908 ◽  
Author(s):  
Jufang He
Keyword(s):  
Sound Intensity ◽  
Noise Burst ◽  
Inhibitory Effect ◽  
Cortical Activation ◽  
Facilitatory Effect ◽  
Stimulation Site ◽  
Inhibitory Effects ◽  
Medial Geniculate ◽  
High Sound ◽  
Onset Responses

He, Jufang. Modulatory effects of regional cortical activation on the onset responses of the cat medial geniculate neurons. J. Neurophysiol. 77: 896–908, 1997. Corticofugal modulation on activity of the medial geniculate body (MGB) was examined by locally activating the primary auditory cortex (AI) and looking for effects on the onset responses of MGB neurons to acoustic stimuli. Of 103 MGB neurons recorded from 13 hemispheres of 11 animals, 91 neurons (88%) showed either a facilitatory or inhibitory effect or both; of these neurons, 72 showed facilitatory effects and 25 inhibitory effects. The average facilitatory effect was large, with a mean increase of 62.4%. Small inhibitory effects (mean: −16.2%) were obtained from a few neurons (6 of 103) when a pure tone stimulus was used, whereas the effect became larger and more frequent when a noise burst stimulus was used (mean: −27.3%, n = 22 of 27 neurons). Activation of an AI site having the same best frequency (BF) as the MGB neuron being recorded from produced mainly a facilitatory effect on MGB neuronal responses to pure tones. Activation of AI at a site neighboring the BF site produced inhibitory effects on the MGB response when noise burst stimuli were used. We found that the effective stimulation sites in AI that could modulate MGB activity formed patchlike maps with a diameter of 1.13 ± 0.09 (SE) mm (range 0.6–1.9 mm, n = 15) being larger than the patches of thalamocortical terminal fields. Examining the effects of sound intensities, of 18 neurons tested 9 neurons showed a larger effect for low-sound-intensity stimuli and small or no effects for high-sound-intensity stimuli. These were named low-sound-intensity effective neurons. Five neurons showed high sound intensity effectiveness and four were non-intensity specific. Most low-sound-intensity effective neurons were monotonic rate-intensity function neurons. The AI cortical modulatory effect was frequency specific, because 15 of 27 neurons showed a larger facilitatory effect when a BF stimulus was used rather than a stimulus of any other frequency. The corticothalamic connection between the recording site in MGB and the most effective stimulation site in AI was confirmed by injecting wheat germ agglutinin–horseradish peroxidase tracer at the stimulation site and producing a small lesion in the recording site. The results suggest that 1) the large facilitation effects obtained by AI activation at the region that directly projected to the MGB could be the result mainly of the direct projection terminals to the MGB relay neurons; 2) the large size patches of the effective stimulation site in AI could be due to widely ramifying corticothalamic projections; and 3) the corticofugal projection selectively gates auditory information mainly by a facilitatory effect, although there is also an inhibitory effect that depends on the sound stimulus used.

scholarly journals Visual cortex responds to transient sound changes without encoding complex auditory dynamics

2019 ◽  
Author(s):  
David Brang ◽  
John Plass ◽  
Aleksandra Sherman ◽  
William C. Stacey ◽  
Vibhangini S. Wasade ◽  
...  
Keyword(s):  
Visual Cortex ◽  
Auditory Cortex ◽  
Visual Signals ◽  
Oscillatory Activity ◽  
Auditory Signal ◽  
Auditory Information ◽  
Fine Grained ◽  
Neural Origin ◽  
Environmental Events ◽  
Visual Cortical

Sounds enhance visual cortical sensitivity for co-occurring visual signals. Previous research has demonstrated that this facilitation occurs through crossmodal modulations of cortical oscillatory activity. However, the neural origin of these signals and auditory information conveyed by this mechanism remain poorly understood. Using intracranial electroencephalography (iEEG) in humans, we examined the sensitivity of visual cortex to three different forms of auditory information: rhythmic entrainment to sounds, auditory onset responses, and auditory offset responses. Subcortical auditory neurons exhibit frequency following behaviors in response to amplitude-modulated sounds, with oscillatory activity entrained at the rhythmic rate of the auditory signal. This auditory response is paralleled in the visual system by the entrainment of visual neurons to the rhythmic rate of flashing strobe lights. In contrast, ~20% of neurons in auditory cortex do not entrain to amplitude modulations but respond only to the onsets and/or offsets of auditory stimuli. In visual cortex, amplitude-modulated sounds elicited transient onset and offset responses in multiple areas, but no entrainment to the sounds’ modulations frequencies. These results suggest that auditory information conveyed to visual cortex does not include temporally fine-grained stimulus dynamics encoded by the auditory midbrain and thalamus but, rather, a temporally segmented representation of auditory events that emerges only in auditory cortex. Crossmodal responses were maximal in low-level visual cortex, potentially implicating a direct pathway for rapid interactions between low-to-mid-level auditory and visual cortices. This mechanism may facilitate perception by time-locking visual computations to environmental events marked by discontinuities in auditory input.

scholarly journals Thalamocortical Projectional Divergence Leads to Complexity in Functional Organizations in Mouse Auditory Cortex

2017 ◽  
Author(s):  
Shinpei Ohga ◽  
Hiroaki Tsukano ◽  
Masao Horie ◽  
Hiroki Terashima ◽  
Nana Nishio ◽  
...  
Keyword(s):  
Auditory Cortex ◽  
Functional Organization ◽  
Medial Geniculate Body ◽  
Primary Auditory Cortex ◽  
Higher Order ◽  
Auditory Information ◽  
Complex Behaviour ◽  
Thalamocortical Projections ◽  
Medial Geniculate ◽  
Auditory Field

AbstractFrequency-related topological projections from the ventral division of the medial geniculate body (MGv) relay the tonotopic organization found in primary auditory cortex (A1). However, relaying circuits of the functional organization to higher-order, secondary auditory field (A2) have not been identified so far. Here, using tracing, we found that A2 receives dense topological projections from MGv in mice, and that tonotopy was established in A2 even when primary fields including A1 were removed. These indicate that thalamic inputs to A2 are sufficient for generating its tonotopy. Moreover, neuronal responses in the thalamocortical recipient layer of A2 showed wider bandwidth and greater heterogeneity of the best frequency distribution than those of A1, which was attributed to larger divergence of thalamocortical projections from MGv to A2 than those from MGv to A1. The current study identifies that the functional organization in the auditory cortex can be determined by the structure of thalamocortical input.Significant StatementAlthough peripheral input patterns to the primary auditory cortex (A1) of the brain are well understood, how tonal information is relayed to higher-order regions such as the secondary auditory field (A2) remains unclear. This work revealed a new source of auditory information to A2; the tonal map in mouse A2 is primarily produced by orderly projections from the primary auditory thalamus. We also found that the complex behaviour and organization of neurons in A2 is generated by divergent projections from the primary thalamus that converge on neurons in A2. Our findings indicate that thalamocortical projections constitute a major factor that determines the regional properties and functional organization of mouse A2.

scholarly journals Spatial pattern of BOLD fMRI activation reveals cross-modal information in auditory cortex

2012 ◽  
Vol 107 (12) ◽  
pp. 3428-3432 ◽  
Author(s):  
P.-J. Hsieh ◽  
J. T. Colas ◽  
N. Kanwisher
Keyword(s):  
Auditory Cortex ◽  
Visual Information ◽  
Visual Stimulation ◽  
Auditory Signal ◽  
Visual Environment ◽  
Auditory Information ◽  
Top Down ◽  
Neural Representations ◽  
Per Se ◽  
High Level

Recent findings suggest that neural representations in early auditory cortex reflect not only the physical properties of a stimulus, but also high-level, top-down, and even cross-modal information. However, the nature of cross-modal information in auditory cortex remains poorly understood. Here, we used pattern analyses of fMRI data to ask whether early auditory cortex contains information about the visual environment. Our data show that 1) early auditory cortex contained information about a visual stimulus when there was no bottom-up auditory signal, and that 2) no influence of visual stimulation was observed in auditory cortex when visual stimuli did not provide a context relevant to audition. Our findings attest to the capacity of auditory cortex to reflect high-level, top-down, and cross-modal information and indicate that the spatial patterns of activation in auditory cortex reflect contextual/implied auditory information but not visual information per se.

scholarly journals Competition and convergence between auditory and cross-modal visual inputs to primary auditory cortical areas

2011 ◽  
Vol 105 (4) ◽  
pp. 1558-1573 ◽  
Author(s):  
Yu-Ting Mao ◽  
Tian-Miao Hua ◽  
Sarah L. Pallas
Keyword(s):  
Auditory Cortex ◽  
Multisensory Processing ◽  
Sensory Deprivation ◽  
Target Space ◽  
Target Cells ◽  
Auditory Input ◽  
Visual Neurons ◽  
Cortical Areas ◽  
Visual Inputs ◽  
Medial Geniculate

Sensory neocortex is capable of considerable plasticity after sensory deprivation or damage to input pathways, especially early in development. Although plasticity can often be restorative, sometimes novel, ectopic inputs invade the affected cortical area. Invading inputs from other sensory modalities may compromise the original function or even take over, imposing a new function and preventing recovery. Using ferrets whose retinal axons were rerouted into auditory thalamus at birth, we were able to examine the effect of varying the degree of ectopic, cross-modal input on reorganization of developing auditory cortex. In particular, we assayed whether the invading visual inputs and the existing auditory inputs competed for or shared postsynaptic targets and whether the convergence of input modalities would induce multisensory processing. We demonstrate that although the cross-modal inputs create new visual neurons in auditory cortex, some auditory processing remains. The degree of damage to auditory input to the medial geniculate nucleus was directly related to the proportion of visual neurons in auditory cortex, suggesting that the visual and residual auditory inputs compete for cortical territory. Visual neurons were not segregated from auditory neurons but shared target space even on individual target cells, substantially increasing the proportion of multisensory neurons. Thus spatial convergence of visual and auditory input modalities may be sufficient to expand multisensory representations. Together these findings argue that early, patterned visual activity does not drive segregation of visual and auditory afferents and suggest that auditory function might be compromised by converging visual inputs. These results indicate possible ways in which multisensory cortical areas may form during development and evolution. They also suggest that rehabilitative strategies designed to promote recovery of function after sensory deprivation or damage need to take into account that sensory cortex may become substantially more multisensory after alteration of its input during development.

scholarly journals Stimulus-specific adaptation in auditory thalamus of young and aged awake rats

2013 ◽  
Vol 110 (8) ◽  
pp. 1892-1902 ◽  
Author(s):  
Ben D. Richardson ◽  
Kenneth E. Hancock ◽  
Donald M. Caspary
Keyword(s):  
Young Adult ◽  
Auditory Cortex ◽  
Brown Norway ◽  
Oddball Paradigm ◽  
Adult Rats ◽  
Specific Adaptation ◽  
Auditory Thalamus ◽  
Gating Mechanism ◽  
Medial Geniculate ◽  
Awake Rats

Novel stimulus detection by single neurons in the auditory system, known as stimulus-specific adaptation (SSA), appears to function as a real-time filtering/gating mechanism in processing acoustic information. Particular stimulus paradigms allowing for quantification of a neuron's ability to detect novel or deviant stimuli have been used to examine SSA in the inferior colliculus, medial geniculate body (MGB), and auditory cortex of anesthetized rodents. However, the study of SSA in awake animals is limited to auditory cortex. The present study used individually advanceable tetrodes to record single-unit responses from auditory thalamus (MGB) of awake young adult and aged Fischer Brown Norway (FBN) rats to 1) examine the presence of SSA in the MGB of awake rats and 2) determine whether SSA is altered by aging in MGB. MGB single units in awake FBN rats displayed SSA in response to two stimulus paradigms: the oddball paradigm and a random blocked/interleaved presentation of a set of frequencies. SSA levels were modestly, but nonsignificantly, increased in the nonlemniscal regions of the MGB and at lower stimulus intensities, where 27 of 57 (47%) young adult MGB units displayed SSA. The present findings provide the initial description of SSA in the MGB of awake rats and support SSA as being qualitatively independent of arousal level or anesthetized state. Finally, contrary to previous studies in auditory cortex of anesthetized rats, MGB units in aged rats showed SSA levels indistinguishable from SSA levels in young adult rats, suggesting that SSA in MGB was not impacted by aging in an awake preparation.

A neural model of medial geniculate body and auditory cortex detecting target distance independently of target velocity in echolocation

2000 ◽  
Vol 32-33 ◽  
pp. 833-841 ◽  
Author(s):  
Satoru Inoue ◽  
Manabu Kimyou ◽  
Yoshiki Kashimori ◽  
Osamu Hoshino ◽  
Takeshi Kambara
Keyword(s):  
Auditory Cortex ◽  
Medial Geniculate Body ◽  
Neural Model ◽  
Target Distance ◽  
Target Velocity ◽  
Medial Geniculate
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