Cortical efferent flow influencing unit responses of medial geniculate body to sound stimulation

Watanabe, Takeshi; Yanagisawa, Keiji; Kanzaki, Jin; Katsuki, Yasuji

doi:10.1007/bf00234776

Cited by 81 publications

(34 citation statements)

References 19 publications

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“…These corticofugal projections are organized tonotopically, such that neurons of a given frequency preference in the cortex project to neurons of similar frequency preference in the MGB and IC (hereafter, subcortical neurons) 4,5 . The effects of cortical feedback on subcortical neurons have been variously described as inhibitory [6][7][8][9] , excitatory 10,11 or both [12][13][14] . We showed previously that in the mustached bat Pteronotus parnellii, excitatory feedback serves to enhance the responses of subcortical neurons tuned to similar frequencies, whereas the inhibitory connections provide a more widespread inhibition of neurons tuned to other frequencies.…”

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confidence: 99%

Corticofugal modulation of the midbrain frequency map in the bat auditory system

1998

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The auditory system, like the visual and somatosensory systems, contains topographic maps in its central neural pathways. These maps can be modified by sensory deprivation, injury and experience in both young and adult animals. Such plasticity has been explained by changes in the divergent and convergent projections of the ascending sensory system. Another possibility, however, is that plasticity may be mediated by descending corticofugal connections. We have investigated the role of descending connections from the cortex to the inferior colliculus of the big brown bat. Electrical stimulation of the auditory cortex causes a downward shift in the preferred frequencies of collicular neurons toward that of the stimulated cortical neurons. This results in a change in the frequency map within the colliculus. Moreover, similar changes can be induced by repeated bursts of sound at moderate intensities. Thus, one role of the mammalian corticofugal system may be to modify subcortical sensory maps in response to sensory experience.

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confidence: 99%

Corticofugal modulation of the midbrain frequency map in the bat auditory system

1998

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“…Functional studies have shown that neocortical electrical stimulation elicits excitatory, andlor inhibitory, andlor complex responses of different latencies from ipsilateral IC neurons (Massopust and Ordy, 1962;Watanabe et al, 1966;Amato et al, 1970;Mitani et al, 1983;Syka and Popelar, 1984;Syka et al, 1988;Sun et al, 19891, which are best explained by varied synaptic interactions occurring within the IC. If, as was discussed above, the corticocollicular projections participate in excitatory synaptic transmission, the inhibitory and complex responses would indicate that at least a percentage of the neurons postsynaptic to neocortical endings are inhibitory and probably y-aminobutyric acid (GABA)ergic.…”

Section: Functional Implicationsmentioning

confidence: 97%

Distribution of descending projections from primary auditory neocortex to inferior colliculus mimics the topography of intracollicular projections

1996

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To ascertain whether the auditory neocortex also innervates the central nucleus of the inferior colliculus (CNIC) and not only its dorsal (DCIC) and external (ECIC) cortices, the anterograde tracers Phaseolus vulgaris-leucoagglutinin (PHA-L) and biotinylated dextran (BD) were injected into the primary auditory neocortex of albino rats (Te1), and labeled corticocollicular fibers were studied via light and electron microscopy. Axons from discrete regions of Te1 form two rostrocaudally oriented laminar plexuses of terminal fibers in the ipsilateral inferior colliculus (IC) and one in the contralateral IC. The first ipsilateral plexus, located in the medial half of the IC, has a dorsomedial to ventrolateral orientation, parallel to the isofrequency planes of the IC; is continuous through the CNIC and DCIC; and extends into the rostral ECIC. The second plexus is located in the deep layers of the lateral ECIC. These two plexuses meet caudally and ventrally, at the border between the CNIC and the lateral ECIC. The plexus in the contralateral IC is less dense and shorter than the two ipsilateral plexuses and is symmetric to the medial plexus. The thickness of the three plexuses is correlated with the size of the injection site, and their mediolateral and dorsoventral positions change as the injection site in Te1 is displaced rostrocaudally, with more caudal injections resulting in more dorsolateral medial plexuses and more dorsomedial lateral plexuses. Furthermore, the ventromedial border of the IC receives nontopographic, convergent projections from wide regions of rostral portions of Te1. The distribution of these corticocollicular plexuses mimics the topography of previously described intracollicular fibers. Electron microscopy shows that, in all three subdivisions of the ipsilateral IC, corticocollicular fibers form small boutons with features generally associated with excitatory transmission; i.e., they contain round synaptic vesicles and form asymmetric synapses with thin dendritic shafts and spines. These results demonstrate that the auditory corticocollicular projections innervate more extensive regions of the IC than were previously observed. Although peripheral regions receive the densest projection, the entire IC appears to be the target of corticofugal input.

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“…Of 20 corticofugal modulatory neurons obtained by Watanabe et al (1966), six had facilitatory effects, with a maximum increase of 57% in the number of spikes. A similar phenomenon was also observed in the cat MGv, in which interneurons accounted for one-fourth of the total population (Villa et al, 1991;He, 1997).…”

Section: Facilitatory Effectmentioning

confidence: 98%

“…Both processes have been observed in the MGB and in the inferior colliculus (IC) when the cortex was activated by electrical stimulation (Watanabe et al, 1966;Sun et al, 1989;He, 1997He, , 2003Suga et al, 1997;Zhou and Jen, 2000;He et al, 2002). The electrical activation of the auditory cortex mainly caused strong facilitation and little inhibition on the lemniscal nucleus of the MGB, although it mainly caused inhibition on the non-lemniscal MGB (Yan and Suga, 1996;He, 1997He, , 2003He et al, 2002).…”

Section: Introductionmentioning

confidence: 99%

Corticofugal Gating of Auditory Information in the Thalamus: AnIn VivoIntracellular Recording Study

Yu¹,

Xiong²,

Chan³

et al. 2004

J. Neurosci.

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In the present study, we investigated the auditory responses of the medial geniculate (MGB) neurons, through in vivo intracellular recordings of anesthetized guinea pigs, while the auditory cortex was electrically activated. Of the 63 neurons that received corticofugal modulation of the membrane potential, 30 received potentiation and 33 received hyperpolarization. The corticofugal potentiation of the membrane potential (amplitude, mean Ϯ SD, 8.6 Ϯ 5.5 mV; duration, 125.5 Ϯ 75.4 msec) facilitated the auditory responses and spontaneous firing of the MGB neurons. The hyperpolarization of Ϫ11.3 Ϯ 4.9 mV in amplitude and 210.0 Ϯ 210.1 msec in duration suppressed the auditory responses and spontaneous firing of the MGB neurons. Four of the five neurons that were histologically confirmed to be located in the lemniscal MGB received corticofugal facilitatory modulation, and all of the four neurons that were confirmed to be located in the non-lemniscal MGB received corticofugal inhibitory modulation. The present intracellular recording provides novel results on how the corticofugal projection gates the sensory information in the thalamus: via the spatially selective depolarization of lemniscal MGB neurons and hyperpolarization of non-lemniscal MGB neurons. It is speculated that the systematic selectivity of facilitation and inhibition over the lemniscal and non-lemniscal MGB is related to the attention shift within the auditory modality and across the sensory modalities.

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Cortical efferent flow influencing unit responses of medial geniculate body to sound stimulation

Cited by 81 publications

References 19 publications

Corticofugal modulation of the midbrain frequency map in the bat auditory system

Corticofugal modulation of the midbrain frequency map in the bat auditory system

Distribution of descending projections from primary auditory neocortex to inferior colliculus mimics the topography of intracollicular projections

Corticofugal Gating of Auditory Information in the Thalamus: AnIn VivoIntracellular Recording Study

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