Corticofugal modulation of the tactile response coherence of projecting neurons in the gracilis nucleus



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Makarov, Valeri A. and Castellanos, Nazareth P. and Malmierca, Eduardo and Nuñez, Ángel (2007) Corticofugal modulation of the tactile response coherence of projecting neurons in the gracilis nucleus. Journal of Neurophysiology, 98 (5). pp. 2537-2549. ISSN 0022-3077

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Precise and reproducible spike timing is one of the alternatives of the sensory stimulus encoding. We test coherence (repeatability) of the response patterns elicited in projecting gracile neurons by tactile stimulation and its modulation provoked by electrical stimulation of the corticofugal feedback from the somatosensory (SI) cortex. To gain the temporal structure we adopt the wavelet-based approach for quantification of the functional stimulus-neural response coupling. We show that the spontaneous firing patterns (when they exist) are essentially random. Tactile stimulation of the neuron receptive field strongly increases the spectral power in the stimulus and 5- to 15-Hz frequency bands. However, the functional coupling (coherence) between the sensory stimulus and the neural response exhibits ultraslow oscillation (0.07 Hz). During this oscillation the stimulus coherence can temporarily fall below the statistically significant level, i.e., the functional stimulus-response coupling may be temporarily lost for a single neuron. We further demonstrate that electrical stimulation of the SI cortex increases the stimulus coherence for about 60% of cells. We find no significant correlation between the increment of the firing rate and the stimulus coherence, but we show that there is a positive correlation with the amplitude of the peristimulus time histogram. The latter argues that the observed facilitation of the neural response by the corticofugal pathway, at least in part, may be mediated through an appropriate ordering of the stimulus-evoked firing pattern, and the coherence enhancement is more relevant in gracilis nucleus than an increase of the number of spikes elicited by the tactile stimulus.

Item Type:Article
Uncontrolled Keywords:Dorsal column nuclei; Rat cuneate nucleus; Somatosensory cortex; Wavelet coherence; Sensorimotor cortex; Behaving monkeys; Brain signals; Spike trains; Time-series; In-vitro
Subjects:Medical sciences > Veterinary > Animal behavior
ID Code:16656
Deposited On:09 Oct 2012 09:37
Last Modified:12 Dec 2018 15:07

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