摘要:

The cytoarchitecture and connections of the brain stem auditory nuclei in the marsupial native cat (Dasyurus hallucatus) were studied using Nissl material in conjunction with the retrograde transport of horseradish peroxidase injected into the inferior colliculus. Some features different from those of Eutheria include the disposition of the cochlear nuclear complex medial to the restiform body, a lack of large spherical cells in the anteroventral cochlear nucleus, a small medial superior olive, and a large superior paraolivary nucleus.

ISSN:0006-8977    

DOI:10.1159/000118668

出版商:S. Karger AG    

年代:1986

数据来源: Karger

摘要:

The representation of sound frequency was examined in the auditory cortex and inferior colliculus of anaesthetized marsupial native cats (Dasyurus hallucatus) using microelectrode mapping techniques. The tonotopic organizations of these two auditory regions are grossly similar to those described in brush-tailed possums and in Eutheria. There appears to exist a biased representation of high frequencies (> 10kHz) in native cats and a paucity of frequencies below 1 kHz. Unit threshold audiograms indicate minimum thresholds between 7 and 12kHz and high thresholds above 30kHz.

ISSN:0006-8977    

DOI:10.1159/000118669

出版商:S. Karger AG    

年代:1986

数据来源: Karger

摘要:

This paper offers a new hypothesis about how the limbic system might assist motor learning. It is proposed that interactions of limbic and sensorimotor-related systems are essential for learning what to do in a motor task (appropriate, relevant behavior) and how to do it best (motor skill). Limbic modulations of sensorimotor-related neural centers are envisaged to result from comparisons in various neural centers of converging inputs from the relevance-sensitive amygdala and from corollary, cortically-modulated recipients of amygdaloid information. Such comparisons of relatively 'raw' limbic inputs and their 'processed', corollary forms could be achieved in a side-loop manner resembling that in the cerebellum. This 'limbic comparator' hypothesis was prompted by studies of motor learning that show how monkeys develop skill only after gaining insight into appropriate, task-related behavior, and that inappropriate behavior during transition into the insightful state produces 'error' signals from the anterior cingulate cortex. Known sites of limbic projections that could serve corollary comparisons are examined with regard to their possible influence on motivation, appropriate, task-related behavior and motor skill. Anatomical and functional tests of convergence and comparison in sensorimotor-related neural centers are suggested in order to stimulate investigations of the limbic comparator hypothesis.

ISSN:0006-8977    

DOI:10.1159/000118670

出版商:S. Karger AG    

年代:1986

数据来源: Karger

摘要:

This paper offers a new hypothesis about how the limbic system might assist motor learning. It is proposed that interactions of limbic and sensorimotor-related systems are essential for learning what to do in a motor task (appropriate, relevant behavior) and how to do it best (motor skill). Limbic modulations of sensorimotor-related neural centers are envisaged to result from comparisons in various neural centers of converging inputs from the relevance-sensitive amygdala and from corollary, cortically-modulated recipients of amygdaloid information. Such comparisons of relatively 'raw' limbic inputs and their 'processed', corollary forms could be achieved in a side-loop manner resembling that in the cerebellum. This 'limbic comparator' hypothesis was prompted by studies of motor learning that show how monkeys develop skill only after gaining insight into appropriate, task-related behavior, and that inappropriate behavior during transition into the insightful state produces 'error' signals from the anterior cingulate cortex. Known sites of limbic projections that could serve corollary comparisons are examined with regard to their possible influence on motivation, appropriate, task-related behavior and motor skill. Anatomical and functional tests of convergence and comparison in sensorimotor-related neural centers are suggested in order to stimulate investigations of the limbic comparator hypothesis.

ISSN:0006-8977    

DOI:10.1159/000316007

出版商:S. Karger AG    

年代:1986

数据来源: Karger

摘要:

The topographic organization of cerebellar cortical efferent fibers from the posterior lobe of the albino rat was studied by silver impregnation methods. The corticonuclear fibers from the vermis of the posterior lobe project to the caudomedial and middle parts of the medial cerebellar nucleus (MN) with medio-lateral localization; fibers from the medial portion of the vermis project to the caudomedial part of the MN (MNcm) and those from the lateral portion project to the middle part of the MN (MNm). Corticovestibular fibers originate in the caudal vermis lateral to the area projecting to the MNcm and MNm, and terminate in the dorsal part of the lateral vestibular nucleus (LVN). The origins of corticonuclear fibers to the dorsolateral protuberance of the MN (MNdlp), the posterior interpositus nucleus (PIN) and the anterior interpositus nucleus (AIN) are located latero-medially in the intermediate cortex. Fibers from the area adjacent to the vermis and rostral to the prepyramidal fissure project to the MNdlp, while those from the area lateral to the origin of the corticovestibular fibers and caudal to the fissure project to the medial AIN. Together, these areas comprise a medial portion of the intermediate cortex. Corticonuclear fibers to the PIN and lateral AIN originate from the lateral portion of the intermediate cortex. The corticonuclear fibers to the dorsolateral hump and lateral nucleus originate from the medial and lateral portions of the lateral cortex, respectively.

ISSN:0006-8977    

DOI:10.1159/000118671

出版商:S. Karger AG    

年代:1986

数据来源: Karger

摘要:

A comparison is made between the relative size of the various thalamic nuclei in man and other primates. Using data for non-human primates predictions are made as to the expected size of the nuclei for the human brain. Of the nuclear groupings five are of the size predicted but three are not. The lateral geniculate is proportionately smaller than predicted, but it is argued that this need not imply a radical change.

ISSN:0006-8977    

DOI:10.1159/000118672

出版商:S. Karger AG    

年代:1986

数据来源: Karger

摘要:

We explored coastal streams, rivers, and swamps in the Guianas of South America and found eleven species of gymnotiform fishes with pulse discharges. Each species has a characteristic electric organ discharge (EOD) waveform of 0.5-5 ms duration; at least two species appear to have a natural sex difference in their EODs which is apparent when comparing large adult males and females. Three sensory coding mechanisms are proposed to explain how electric fish might be able to determine species and sex identity from such short electrical pulses. Spectral Coding: electroreceptors tuned to different frequencies encode the spectrum of the EOD as a cross-fiber stimulation pattern. Temporal Coding: EODs are encoded as a volley of nerve spikes patterned in the time domain. Scan Sampling: a receiver detects a signaler's EOD as an amplitude modulation or 'beat' set up by the combination of its own discharge with the signaler's. The receiver uses the modulation envelope to assess the signaler's EOD waveform. To distinguish between these three coding mechanisms, we tested the ability of one pulse gymnotiform, Hypopomus beebei, to discriminate one electric waveform from another by comparing the acceleration of the discharge rate to different stimuli. Stimuli are presented under two conditions: (a) when the stimulus pulse train is free-running compared to the fish's pulse train, and (b) when the stimulus train is phase-locked to the fish's discharge pulse train. Under the former condition scan sampling may be used; under the latter it will be impossible. Hypopomus discriminates the polarity of a single period sinusoidal stimulus under scanning conditions but does not discriminate under clamped conditions. Hypopomus gives the strongest response to single period sine waves of 670 Hz and weaker responses to sinusoids of lower and higher frequencies. Free-running and phase-locked stimuli evoke similar responses. Under free-running conditions, Hypopomus discriminates a series of EOD-like stimuli that have been phase-shifted by varying amounts, but under phase-locked conditions does not. Scan sampling is presented as a possible waveform recognition mechanism for pulse-discharging gymnotiform fishes.

ISSN:0006-8977    

DOI:10.1159/000118673

出版商:S. Karger AG    

年代:1986

数据来源: Karger

摘要:

We explored coastal streams, rivers, and swamps in the Guianas of South America and found eleven species of gymnotiform fishes with pulse discharges. Each species has a characteristic electric organ discharge (EOD) waveform of 0.5-5 ms duration; at least two species appear to have a natural sex difference in their EODs which is apparent when comparing large adult males and females. Three sensory coding mechanisms are proposed to explain how electric fish might be able to determine species and sex identity from such short electrical pulses. Spectral Coding: electroreceptors tuned to different frequencies encode the spectrum of the EOD as a cross-fiber stimulation pattern. Temporal Coding: EODs are encoded as a volley of nerve spikes patterned in the time domain. Scan Sampling: a receiver detects a signaler's EOD as an amplitude modulation or 'beat' set up by the combination of its own discharge with the signaler's. The receiver uses the modulation envelope to assess the signaler's EOD waveform. To distinguish between these three coding mechanisms, we tested the ability of one pulse gymnotiform, Hypopomus beebei, to discriminate one electric waveform from another by comparing the acceleration of the discharge rate to different stimuli. Stimuli are presented under two conditions: (a) when the stimulus pulse train is free-running compared to the fish's pulse train, and (b) when the stimulus train is phase-locked to the fish's discharge pulse train. Under the former condition scan sampling may be used; under the latter it will be impossible. Hypopomus discriminates the polarity of a single period sinusoidal stimulus under scanning conditions but does not discriminate under clamped conditions. Hypopomus gives the strongest response to single period sine waves of 670 Hz and weaker responses to sinusoids of lower and higher frequencies. Free-running and phase-locked stimuli evoke similar responses. Under free-running conditions, Hypopomus discriminates a series of EOD-like stimuli that have been phase-shifted by varying amounts, but under phase-locked conditions does not. Scan sampling is presented as a possible waveform recognition mechanism for pulse-discharging gymnotiform fishes.

ISSN:0006-8977    

DOI:10.1159/000316008

出版商:S. Karger AG    

年代:1986

数据来源: Karger

摘要:

In the common European mole (Talpa europaea) the isocortex is a six-layered structure representing about 50% of the total cerebral cortex. The internal granular layer is narrow in the occipital region, however, probably reflecting a poorly developed visual system in an animal adapted to life in a subterranean environment. Golgi impregnation of projection cells and most local-circuit neurons of layers III-VI suggests a relatively well-developed isocortex in this insectivore. The presence of extraverted neurons in the so-called accentuated layer II and the amount of local-circuit neurons with very long beaded dendrites, however, probably represents primitive characteristics of the isocortex in mammals.

ISSN:0006-8977    

DOI:10.1159/000118674

出版商:S. Karger AG    

年代:1986

数据来源: Karger

ISSN:0006-8977    

DOI:10.1159/000118675

出版商:S. Karger AG    

年代:1986

数据来源: Karger