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C M Müller

Publications and source records attributed to C M Müller.

41 records · Page 3Linked to original sources
PubMed1987

Differential effects of acetylcholine in the chicken auditory neostriatum and hyperstriatum ventrale--studies in vivo and in vitro.

1. The effect of acetylcholine (ACh) on the response properties of single units in the caudal auditory telencephalon was studied both in awake chickens and in an in vitro slice preparation. 2. Two types of electrophysiological behavior in response to ACh were observed: an inhibition of cell firing typical for the majority of neurons in the auditory hyperstriatum ventrale and a facilitation of neuronal responses seen predominantly in neostriatal auditory units. 3. The facilitatory effect of ACh is also present in hyperstriatal cells, but is usually dominated by an indirect inhibition. 4. ACh-induced facilitation on single unit responses could be mimicked in awake birds by applying potentially arousing sensory stimuli. 5. The effects of ACh are antagonized by the muscarinic receptor blocker scopolamine. 6. Inhibitory responses can also be antagonized by the GABA-antagonist bicuculline and thus can be attributed to an ACh-induced activation of GABAergic inhibitory interneurons. Evidence is given that the facilitatory responses result from a closure of voltage-dependent potassium channels. 7. The results are discussed with respect to a possible role of cholinergic afferents in telencephalic processing of auditory information and in comparison with the cholinergic influences in the mammalian neocortex.

Acetylcholine↗
PubMed1985

Feature extraction and tonotopic organization in the avian auditory forebrain.

In a neurophysiological study within the auditory centers of the mediocaudal telencephalon of the starling, 601 neurons were tested for auditory responses. 369 of these units responded to pure tones, noise bands, amplitude modulations (AM), or species-specific sounds. Of all the auditory neurons, 16.8% did not respond to pure tones but only to more complex stimuli (tone-unresponsive-, TU-units). The remaining auditory units were classified as tone-responsive (TR-units). In 44.3% of TR-units (i.e. 36.9% of all auditory units) differing responses to tones versus more complex stimuli were observed. Responses as they occur in TU-units and in the differing responses of TR-units can be explained by neuronal extraction of features in the time (108 out of 198 neurons) and in the spectral domain (82 out of 198 neurons). Responses to species-specific sounds usually can be explained in terms of extraction of these features. Among neurons sensitive to temporal features, exclusive responses to a narrow range of AM frequencies were observed. In those TU-units that represent spectral features some restrict their responses to noise bands with distinct bandwidths centered around a specific midfrequency. These units reject both wider and narrower noise bands. A tonotopic arrangement of auditory units is found in field L, the surrounding neostriatum (NCM), and the Hyperstriatum ventrale (HV). Isofrequency lines run as a continuum through NCM, field L, and the caudal part of HV. TU-units are integrated into the tonotopic gradient according to the midfrequency of effective stimuli (e.g. noise bands or AM). The anatomical position of auditory units is correlated to their response properties. Within one isofrequency contour an increase in response selectivity is seen from field L to the postsynaptic areas in the NCM and the HV. The results are discussed in terms of possible mechanisms of feature extraction in the avian auditory system.

Acoustic Stimulation↗
PubMed1984

2-Deoxyglucose accumulation parallels extracellularly recorded spike activity in the avian auditory neostriatum.

In a combined 2-deoxyglucose (2-DG) and electrophysiological study, the congruence between metabolic activity and extracellularly recorded spike activity patterns has been examined in the auditory cortex analogue, field L, of chicks. Using tone stimuli we demonstrate a match of stripes of 2-DG labeling to electrode tracks yielding neurons with the same best frequency. Since 2-DG activity is thought to reflect chiefly input activity of neurons there appears to be a close input-output link for tone responses in field L.

Animals↗
PubMedDate not supplied

Possible role of S-100 in glia-neuronal signalling involved in activity-dependent plasticity in the developing mammalian cortex.

Using Western blot analyses and a quantitative ELISA, we identified the presence and developmental accumulation of the astroglial S-100 protein(s) in rat and cat visual cortex. There is a steep rise in the S-100 content, comprising mainly S-100 beta, during the time period of highest cortical malleability in both species. A possible role of the astroglial S-100 protein(s) in experience-dependent plasticity of the visual cortex of kittens was tested by infusing antiserum against this protein during the critical period for cortical malleability. Following 1 week of monocular deprivation, the ocular dominance of single cells in the visual cortex was investigated. The vast majority of cells in the hemispheres infused with anti-S-100 serum maintained binocular responses. This finding suggests that extracellular S-100 protein is essential for ocular-dominance plasticity. Infusion of S-100 beta during the critical period of cortical malleability had no effect on deprivation-induced ocular-dominance plasticity, but interfered with the experience-dependent refinement of orientation selectivity of visual cortical neurons. It is suggested that S-100 beta may play an important role in the refinement of cortical circuitries by selectively affecting active or activated neuronal compartments. As S-100 beta is synthesized in astroglial cells, the effects on neuronal plasticity imply that glia-neuronal information transfer occurs during activity-dependent plasticity. Possible underlying mechanisms are discussed on the basis of current knowledge on the S-100 protein family, especially S-100 beta (Marshak, 1990).

Aging↗