Projections from auditory cortex to midbrain cholinergic neurons that project to the inferior colliculus.
Acetylcholine/*metabolism; Amidines; Animals; Auditory Cortex/*cytology/metabolism; Auditory Perception/physiology; Brain Mapping; Choline O-Acetyltransferase/metabolism; Cholinergic Fibers/metabolism/ultrastructure; Dextrans; Female; Functional Laterality/physiology; Guinea Pigs; Immunohistochemistry; Inferior Colliculi/*cytology/metabolism; Male; Mesencephalon/*cytology/metabolism; Neural Pathways/cytology/metabolism; Neuroanatomical Tract-Tracing Techniques; Neuronal Tract-Tracers; Neurons/*cytology/metabolism; Pedunculopontine Tegmental Nucleus/*cytology/metabolism; Rhodamines; Synaptic Transmission/physiology
We have shown that auditory cortex projects to cholinergic cells in the pedunculopontine tegmental nucleus (PPT) and laterodorsal tegmental nucleus (LDT). PPT and LDT are the sources of cholinergic projections to the inferior colliculus, but it is not known if the cortical inputs contact the cholinergic cells that project to the inferior colliculus. We injected FluoroRuby into auditory cortex in pigmented guinea pigs to label cortical projections to PPT and LDT. In the same animals, we injected Fast Blue into the left or right inferior colliculus to label PPT and LDT cells that project to the inferior colliculus. We processed the brain to identify cholinergic cells with an antibody to choline acetyltransferase, which was visualized with a green fluorescent marker distinguishable from both FluoroRuby and Fast Blue. We then examined the PPT and LDT to determine whether boutons of FluoroRuby-labeled cortical axons were in close contact with cells that were double-labeled with the retrograde tracer and the immunolabel. Apparent contacts were observed ipsilateral and, less often, contralateral to the injected cortex. On both sides, the contacts were more numerous in PPT than in LDT. The results indicate that auditory cortex projects directly to brainstem cholinergic cells that innervate the ipsilateral or contralateral inferior colliculus. This suggests that cortical projections could elicit cholinergic effects on both sides of the auditory midbrain.
Schofield B R
Neuroscience
2010
2010-03
Article information provided for research and reference use only. All rights are retained by the journal listed under publisher and/or the creator(s).
<a href="http://doi.org/10.1016/j.neuroscience.2009.12.008" target="_blank" rel="noreferrer noopener">10.1016/j.neuroscience.2009.12.008</a>
Combination-sensitive neurons in the inferior colliculus.
Acoustic Stimulation; Animals; Auditory Cortex/metabolism; Chiroptera; Doppler; Inferior Colliculi/*cytology/metabolism; Neurons/cytology/*physiology; Sound Localization; Transcranial; Ultrasonography
We examined whether neurons in the inferior colliculus of the mustached bat (Pteronotus parnellii) are combination sensitive, responding to both low- and high-frequency components of the bat's sonar signal. These neurons, previously reported in the thalamus and cortex, analyze sonar target features including distance. Of 82 single units and 36 multiple units from the 58-112 kHz representations of the inferior colliculus, most (86%) displayed sensitivity to low-frequency sounds that was tuned in the range of the fundamental biosonar component (24-31 kHz). All histologically localized units were in the central nucleus of the inferior colliculus (ICC). There were two major types of combination-sensitive influences. Many neurons were facilitated by low-frequency sounds and selective for particular delays between the low- and high-frequency components. In other neurons, the low-frequency signal was inhibitory if presented simultaneously or a few milliseconds prior to the high-frequency signal. The results indicate that mechanisms creating specialized frequency comparisons and delay sensitivity in combination-sensitive neurons operate at the ICC or below. Since combination sensitivity or multipeaked tuning curves occur in the auditory systems of many species, ICC neurons in these animals may also respond to species-specific frequency combinations.
Mittmann D H; Wenstrup J J
Hearing research
1995
1995-10
Article information provided for research and reference use only. All rights are retained by the journal listed under publisher and/or the creator(s).
<a href="http://doi.org/10.1016/0378-5955(95)00164-x" target="_blank" rel="noreferrer noopener">10.1016/0378-5955(95)00164-x</a>