Corticofugal modulation of the vago-vagal motor gastric reflex

Neural mechanism of corticofugal modulation of frequency processing in bat auditory system

Neuroscience Research ◽

10.1016/j.neures.2007.06.1146 ◽

2007 ◽

Vol 58 ◽

pp. S99

Author(s):

Yoshiki Kashimori ◽

Seiichi Hirooka ◽

Kazuhisa Fujita

Keyword(s):

Auditory System ◽

Neural Mechanism ◽

Corticofugal Modulation ◽

Frequency Processing

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

Journal of Neurophysiology ◽

10.1152/jn.00593.2002 ◽

2003 ◽

Vol 89 (1) ◽

pp. 367-381 ◽

Cited By ~ 31

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.

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

Journal of Neurophysiology ◽

10.1152/jn.2002.88.2.1040 ◽

2002 ◽

Vol 88 (2) ◽

pp. 1040-1050 ◽

Cited By ~ 30

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.

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