Single unit extracellular recordings were obtained from non-directional and from directionally se... more Single unit extracellular recordings were obtained from non-directional and from directionally selective cells in the pigeon's optic tectum. Non-directional cells were classified according to their excitatory dynamic profiles into three classes. Class A: cells showing spatially superimposed light and dark regions in their fields. Class B: cells showing spatially separated light and dark regions in their fields. Class C: cells which responded exclusively to one sign of contrast. Most of the cells in our sample showed a suppressive region outside the excitatory area from where moving stimuli were able to reduce the units' "spontaneous" background firing. Suppressive regions were found in directionally selective as well as in non-directional cells, regardless of their dynamic excitatory profiles, with the exception of Class C cells. Evidence of spatial overlapping between the excitatory and the suppressive region was obtained with both moving and flashed stimuli. Furthermore, suppressive antagonistic effects were observed in Class B cells.
Publisher Summary A large amount of experimental data has provided direct evidence that thalamoco... more Publisher Summary A large amount of experimental data has provided direct evidence that thalamocortical (TC) cells in vitro are capable of different types of intrinsic oscillatory activities, that is, oscillations that occur in the absence of sensory and cortical inputs and of intrathalamic afferents, that is, from interneurons and cells of the nucleus reticularis thalami. This chapter describes these types of oscillation, analyzes their underlying ionic currents, and presents a biophysical model of a TC cell that accurately reproduces the intrinsic activity patterns and the transitions among these different states. In addition, the chapter also discusses how rhythmic and randomly occurring fast synaptic potentials—EPSPs and IPSPs—modulate these intrinsic oscillations, and stresses that the behavior of TC cells in both physiological and pathological conditions can be fully understood only by taking into account that they are pacemaker neurons whose activity is modulated by synaptic ...
Comptes rendus des seances de l'Academie des sciences. Serie III, Sciences de la vie, 1982
The influence of the visual telencephalic projection area (Wulst) upon directional selective cell... more The influence of the visual telencephalic projection area (Wulst) upon directional selective cells in the Pigeon's optic tectum was studied through reversible cold block of this telencephalic region. About half of the cells studied were affected during Wulst cooling. The effect was either a total loss or a marked reduction of the cell directional selectivity. These results indicate that the Wulst plays an important role in controlling the directional selectivity in the Pigeon's optic tectum.
Comptes rendus des séances de l'Académie des sciences. Série III, Sciences de la vie, Jan 3, 1982
The influence of the visual telencephalic projection area (Wulst) upon directional selective cell... more The influence of the visual telencephalic projection area (Wulst) upon directional selective cells in the Pigeon's optic tectum was studied through reversible cold block of this telencephalic region. About half of the cells studied were affected during Wulst cooling. The effect was either a total loss or a marked reduction of the cell directional selectivity. These results indicate that the Wulst plays an important role in controlling the directional selectivity in the Pigeon's optic tectum.
Gamma-aminobutyric acid (GABA) in the thalamus has mainly been associated with the inhibitory mod... more Gamma-aminobutyric acid (GABA) in the thalamus has mainly been associated with the inhibitory modulation of the sensory and cortical flow of information via a 'classical', chloride-dependent, GABAA receptor-mediated action. However, the discovery of a late, long-lasting potassium-dependent inhibitory postsynaptic potential (IPSP) mediated by GABAB receptors present on thalamocortical cells, has allowed new insights into our understanding of the physiological role of this neurotransmitter. In particular, work on the dorsal lateral geniculate nucleus indicates that together with a relatively weak inhibition, GABAB receptor-mediated IPSPs 'prepare' thalamocortical cells for burst firing by activating low-threshold calcium potentials. Thus, GABA in the thalamus can no longer be viewed only as a 'classical' inhibitory transmitter but also as a neuromodulator with a 'priming' role for burst firing excitation. This dual role of GABAB receptors in inhibition ...
Single unit extracellular recordings were obtained from non-directional and from directionally se... more Single unit extracellular recordings were obtained from non-directional and from directionally selective cells in the pigeon's optic tectum. Non-directional cells were classified according to their excitatory dynamic profiles into three classes. Class A: cells showing spatially superimposed light and dark regions in their fields. Class B: cells showing spatially separated light and dark regions in their fields. Class C: cells which responded exclusively to one sign of contrast. Most of the cells in our sample showed a suppressive region outside the excitatory area from where moving stimuli were able to reduce the units' "spontaneous" background firing. Suppressive regions were found in directionally selective as well as in non-directional cells, regardless of their dynamic excitatory profiles, with the exception of Class C cells. Evidence of spatial overlapping between the excitatory and the suppressive region was obtained with both moving and flashed stimuli. Furthermore, suppressive antagonistic effects were observed in Class B cells.
Publisher Summary A large amount of experimental data has provided direct evidence that thalamoco... more Publisher Summary A large amount of experimental data has provided direct evidence that thalamocortical (TC) cells in vitro are capable of different types of intrinsic oscillatory activities, that is, oscillations that occur in the absence of sensory and cortical inputs and of intrathalamic afferents, that is, from interneurons and cells of the nucleus reticularis thalami. This chapter describes these types of oscillation, analyzes their underlying ionic currents, and presents a biophysical model of a TC cell that accurately reproduces the intrinsic activity patterns and the transitions among these different states. In addition, the chapter also discusses how rhythmic and randomly occurring fast synaptic potentials—EPSPs and IPSPs—modulate these intrinsic oscillations, and stresses that the behavior of TC cells in both physiological and pathological conditions can be fully understood only by taking into account that they are pacemaker neurons whose activity is modulated by synaptic ...
Comptes rendus des seances de l'Academie des sciences. Serie III, Sciences de la vie, 1982
The influence of the visual telencephalic projection area (Wulst) upon directional selective cell... more The influence of the visual telencephalic projection area (Wulst) upon directional selective cells in the Pigeon's optic tectum was studied through reversible cold block of this telencephalic region. About half of the cells studied were affected during Wulst cooling. The effect was either a total loss or a marked reduction of the cell directional selectivity. These results indicate that the Wulst plays an important role in controlling the directional selectivity in the Pigeon's optic tectum.
Comptes rendus des séances de l'Académie des sciences. Série III, Sciences de la vie, Jan 3, 1982
The influence of the visual telencephalic projection area (Wulst) upon directional selective cell... more The influence of the visual telencephalic projection area (Wulst) upon directional selective cells in the Pigeon's optic tectum was studied through reversible cold block of this telencephalic region. About half of the cells studied were affected during Wulst cooling. The effect was either a total loss or a marked reduction of the cell directional selectivity. These results indicate that the Wulst plays an important role in controlling the directional selectivity in the Pigeon's optic tectum.
Gamma-aminobutyric acid (GABA) in the thalamus has mainly been associated with the inhibitory mod... more Gamma-aminobutyric acid (GABA) in the thalamus has mainly been associated with the inhibitory modulation of the sensory and cortical flow of information via a 'classical', chloride-dependent, GABAA receptor-mediated action. However, the discovery of a late, long-lasting potassium-dependent inhibitory postsynaptic potential (IPSP) mediated by GABAB receptors present on thalamocortical cells, has allowed new insights into our understanding of the physiological role of this neurotransmitter. In particular, work on the dorsal lateral geniculate nucleus indicates that together with a relatively weak inhibition, GABAB receptor-mediated IPSPs 'prepare' thalamocortical cells for burst firing by activating low-threshold calcium potentials. Thus, GABA in the thalamus can no longer be viewed only as a 'classical' inhibitory transmitter but also as a neuromodulator with a 'priming' role for burst firing excitation. This dual role of GABAB receptors in inhibition ...
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