Cortical modulation of neuronal activity in the cat's lateral geniculate and perigeniculate nuclei: a modeling study (original) (raw)
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BMC Neuroscience, 2013
The role of cortical feedback in the thalamocortical processing loop has been extensively investigated over the last decades. With an exception of several cases, these searches focused on the cortical feedback exerted onto thalamo-cortical relay (TC) cells of the dorsal lateral geniculate nucleus (LGN). In a previous, physiological study, we showed in the cat visual system that cessation of cortical input, despite decrease of spontaneous activity of TC cells, increased spontaneous firing of their recurrent inhibitory interneurons located in the perigeniculate nucleus (PGN). To identify mechanisms underlying such functional changes we conducted a modeling study in NEURON on several networks of point neurons with varied model parameters, such as membrane properties, synaptic weights and axonal delays. We considered six network topologies of the retino-geniculo-cortical system. All models were robust against changes of axonal delays except for the delay between the LGN feed-forward interneuron and the TC cell. The best representation of physiological results was obtained with models containing reciprocally connected PGN cells driven by the cortex and with relatively slow decay of intracellular calcium. This strongly indicates that the thalamic reticular nucleus plays an essential role in the cortical influence over thalamo-cortical relay cells while the thalamic feed-forward interneurons are not essential in this process. Further, we suggest that the dependence of the activity of PGN cells on the rate of calcium removal can be one of the key factors determining individual cell response to elimination of cortical input.
Acta Neurobiologiae Experimentalis, 2012
The role of cortical feedback in the thalamocortical processing loop has been extensively investigated over the last decades. With an exception of several cases, these searches focused on the cortical feedback exerted onto thalamo-cortical relay (TC) cells of the dorsal lateral geniculate nucleus (LGN). In a previous, physiological study, we showed in the cat visual system that cessation of cortical input, despite decrease of spontaneous activity of TC cells, increased spontaneous firing of their recurrent inhibitory interneurons located in the perigeniculate nucleus (PGN). To identify mechanisms underlying such functional changes we conducted a modeling study in NEURON on several networks of point neurons with varied model parameters, such as membrane properties, synaptic weights and axonal delays. We considered six network topologies of the retino-geniculo-cortical system. All models were robust against changes of axonal delays except for the delay between the LGN feed-forward interneuron and the TC cell. The best representation of physiological results was obtained with models containing reciprocally connected PGN cells driven by the cortex and with relatively slow decay of intracellular calcium. This strongly indicates that the thalamic reticular nucleus plays an essential role in the cortical influence over thalamo-cortical relay cells while the thalamic feed-forward interneurons are not essential in this process. Further, we suggest that the dependence of the activity of PGN cells on the rate of calcium removal can be one of the key factors determining individual cell response to elimination of cortical input.
The role of cortical feedback in the thalamocortical processing loop has been extensively investigated over the last decades. With an exception of several cases, these searches focused on the cortical feedback exerted onto thalamo-cortical relay (TC) cells of the dorsal lateral geniculate nucleus (LGN). In a previous, physiological study, we showed in the cat visual system that cessation of cortical input, despite decrease of spontaneous activity of TC cells, increased spontaneous firing of their recurrent inhibitory interneurons located in the perigeniculate nucleus (PGN). To identify mechanisms underlying such functional changes we conducted a modeling study in NEURON on several networks of point neurons with varied model parameters, such as membrane properties, synaptic weights and axonal delays. We considered six network topologies of the retino-geniculo-cortical system. All models were robust against changes of axonal delays except for the delay between the LGN feed-forward interneuron and the TC cell. The best representation of physiological results was obtained with models containing reciprocally connected PGN cells driven by the cortex and with relatively slow decay of intracellular calcium. This strongly indicates that the thalamic reticular nucleus plays an essential role in the cortical influence over thalamo-cortical relay cells while the thalamic feed-forward interneurons are not essential in this process. Further, we suggest that the dependence of the activity of PGN cells on the rate of calcium removal can be one of the key factors determining individual cell response to elimination of cortical input.
Cognitive Neurodynamics, 2012
A striking feature of the organization of the early visual pathway is the significant feedback from primary visual cortex to cells in the dorsal lateral geniculate nucleus (LGN). Despite numerous experimental and modeling studies, the functional role for this feedback remains elusive. We present a new firing-rate-based model for LGN relay cells in cat, explicitly accounting for thalamocortical loop effects. The established DOG model, here assumed to account for the spatial aspects of the feedforward processing of visual stimuli, is extended to incorporate the influence of thalamocortical loops including a full set of orientation-selective cortical cell populations. Assuming a phase-reversed push-pull arrangement of ON and OFF cortical feedback as seen experimentally, this extended DOG (eDOG) model exhibits linear firing properties despite non-linear firing characteristics of the corticothalamic cells. The spatiotemporal receptive field of the eDOG model has a simple algebraic structure in Fourier space, while the real-space receptive field, as well as responses to visual stimuli, are found by evaluation of an integral. As an example application we use the eDOG model to study effects of cortical feedback on responses to flashing circular spots and patch-grating stimuli and find that the eDOG model can qualitatively account for experimental findings.
Journal of neurophysiology, 1992
1. The visual cortex receives several types ofafferents from the lateral geniculate nucleus ( LGN ) of the thalamus. In the cat, previous work studied the oN/orr and X/Y distinctions, investigating their convergence and segregation in cortex. Here we pursue the lagged/nonlagged dichotomy as it applies to simple cells in area 17 . Lagged and nonlagged cells in the A-layers of the LGN can be distinguished by the timing of their responses to sinusoidally luminance-modulated stimuli. We therefore used similar stimuli in cortex to search for signs of lagged and nonlagged inputs to cortical cells.
1. It has recently been shown that the X-and Y-cell classes in the AJayers of the cat lateral geniculate nucleus (LGN) are divisible into lagged and nonlagged types. We have characterized the visual response properties of 153 cells in the AJayers to ,l) reveal response features that are relevant to the X/Y and lagged/nonlagged classiflcation schemes, and 2) provide a systematic description ofthe properties oflagged and nonl"gged cells as a basis for understanding mechanisms that affect these two groups. Responses to flashing spots and drifting gratings were measured as the contrast and spatial and temporal modulation were varied.
Experimental Neurology, 1979
The antidromic extracellular action potentials of 470 pyramidal tract (PT) neurons were recorded after stimulation of the ipsilateral medullary pyramid in pentobarbital-anesthetized cats. The amplitude of the antidromic action potentials of PT cells was inversely related to their antidromic spike latencies. The duration of the antidromic spike was a linear function of the antidromic latency. There was a negative correlation between the amplitude of antidromic spike and its duration. Three groups were distinguished in the latency histogram, indicating that the PT neurons can be separated into three groups: group I (F-fast, large), group II (SI-intermediate, medium size), and group III (SII-very slow, small). The latencies and conduction velocities of neurons in groups I, II, and III were respectively 0.45 to 1.9 (25.26 to 106.7). 2.09 to 4.2 (11.16 to 22.97), and 4.24 to 7.95 ms (6.05 to Il. 14 m/s). Two waves were recorded from the cortical surface before insertion of the microelectrode into the cerebral cortex. Three waves appeared as the microelectrode was advanced into the cortex to the depth of 150 or 200 pm. The time course of these three waves coincided with that of three PT cell groups in each particular experiment. We suggest that cortical, spinal, and muscular motor units may be interrelated with regard to size and function.