Responses of caudate neurons to direct electrical stimulation of the medial geniculate body in cats

Electrical stimulation of the auditory cortex (AC) causes both facilitatory and inhibitory effects on the medial geniculate body (MGB). The purpose of this study was to identify the corticofugal inhibitory pathway to the MGB. We assessed two potential circuits: 1) the cortico-colliculo-thalamic circuit and 2) cortico-reticulo-thalamic one. We compared intracellular responses of MGB neurons to electrical stimulation of the AC following bilateral ablation of the inferior colliculi (IC) or thalamic reticular nucleus (TRN) in anesthetized guinea pigs. Cortical stimulation with intact TRN could cause strong inhibitory effects on the MGB neurons. The corticofugal inhibition remained effective after bilateral IC ablation, but it was minimized after the TRN was lesioned with kainic acid. Synchronized TRN neuronal activity and MGB inhibitory postsynaptic potentials (IPSPs) were observed with multiple recordings. The results suggest that corticofugal inhibition traverses the corticoreticulothalamic pathway, indicating that the colliculi-geniculate inhibitory pathway is probably only for feedforward inhibition.

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The functional anatomy of middle-latency auditory evoked potentials: thalamocortical connections

Journal of Neurophysiology ◽

10.1152/jn.1992.68.2.425 ◽

1992 ◽

Vol 68 (2) ◽

pp. 425-431 ◽

Cited By ~ 41

Author(s):

S. Di ◽

D. S. Barth

Keyword(s):

Electrical Stimulation ◽

Auditory Cortex ◽

Evoked Potentials ◽

Linear Combination ◽

Evoked Potential ◽

Medial Geniculate Body ◽

Cortex Area ◽

Medial Geniculate ◽

Potential Complex ◽

Stimulation Of

1. An 8 x 8-channel microelectrode array was used to map epicortical field potentials from a 4.375 x 4.375-mm2 area in the right parietotemporal neocortex of four rats. Potentials were evoked with bilaterally presented click stimuli and with electrical stimulation of the ventral and dorsal divisions of the medial geniculate body. 2. Epicortical responses to click stimuli replicated earlier findings. The responses consisted of a positive-negative biphasic waveform (P1a and N1) in the region of primary auditory cortex (area 41) and a positive monophasic waveform (P1b) in the region of secondary auditory cortex (area 36). Two potential patterns, one at the latency of the N1 and the other at the latency of the P1b, were used to represent activation of cells within areas 41 and 36. A linear combination of these patterns was sufficient to explain from 90 to 94% of the variance of the evoked potential complex at all latencies. 3. In the same animals, epicortical responses to electrical stimulation of the ventral and dorsal divisions of the medial geniculate body were also localized to areas 41 and 36, respectively. A linear combination of potential patterns from these separate stimulation conditions was sufficient to explain from 80 to 93% of the variance of the original click-evoked potential complex at all latencies. 4. These data provide functional evidence for anatomically defined topographical thalamocortical projections to primary and secondary auditory cortex. They suggest that short-latency cortical evoked potentials (10-60 ms poststimulus) are dominated by parallel thalamocortical activation of areas 41 and 36.

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Unit responses evoked in the amygdala and striatum by electrical stimulation of the medial geniculate body

Journal of Neuroscience ◽

10.1523/jneurosci.10-04-01055.1990 ◽

1990 ◽

Vol 10 (4) ◽

pp. 1055-1061 ◽

Cited By ~ 56

Author(s):

MC Clugnet ◽

JE LeDoux ◽

SF Morrison

Keyword(s):

Electrical Stimulation ◽

Medial Geniculate Body ◽

Medial Geniculate ◽

Stimulation Of

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Changes in Prefrontal Cortex–Thalamic Circuitry after Acoustic Trauma

Biomedicines ◽

10.3390/biomedicines9010077 ◽

2021 ◽

Vol 9 (1) ◽

pp. 77

Author(s):

Kristin M. Barry ◽

Donald Robertson ◽

Wilhelmina H. A. M. Mulders

Keyword(s):

Electrical Stimulation ◽

Prefrontal Cortex ◽

Auditory System ◽

Acoustic Trauma ◽

Neuron Activity ◽

Compensatory Mechanism ◽

Efferent Connections ◽

Medial Geniculate ◽

Central Auditory Pathways ◽

Stimulation Of

In the adult auditory system, loss of input resulting from peripheral deafferentation is well known to lead to plasticity in the central nervous system, manifested as reorganization of cortical maps and altered activity throughout the central auditory pathways. The auditory system also has strong afferent and efferent connections with cortico-limbic circuitry including the prefrontal cortex and the question arises whether this circuitry is also affected by loss of peripheral input. Recent studies in our laboratory showed that PFC activation can modulate activity of the auditory thalamus or medial geniculate nucleus (MGN) in normal hearing rats. In addition, we have shown in rats that cochlear trauma resulted in altered spontaneous burst firing in MGN. However, whether the PFC influence on MGN is changed after cochlear trauma is unknown. We investigated the effects of electrical stimulation of PFC on single neuron activity in the MGN in anaesthetized Wistar rats 2 weeks after acoustic trauma or sham surgery. Electrical stimulation of PFC showed a variety of effects in MGN neurons both in sham and acoustic trauma groups but inhibitory responses were significantly larger in the acoustic trauma animals. These results suggest an alteration in functional connectivity between PFC and MGN after cochlear trauma. This change may be a compensatory mechanism increasing sensory gating after the development of altered spontaneous activity in MGN, to prevent altered activity reaching the cortex and conscious perception.

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