Corticofugal Modulation of the Tactile Response Coherence of Projecting Neurons in the Gracilis Nucleus

Abstract

Castellanos NP, Malmierca E, Nuñ ez A, Makarov VA. Corticofugal modulation of the tactile response coherence of projecting neurons in the gracilis nucleus. J Neurophysiol 98: [2537][2538][2539][2540][2541][2542][2543][2544][2545][2546][2547][2548][2549] 2007. First published August 29, 2007; doi:10.1152/jn.00815.2007. 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.

Corticofugal Modulation of Initial Sound Processing in the Brain

“…Many studies in the visual, auditory and somatosensory systems have unveiled that sensory cortices differentially modulate subcortical neuron activities in a highly specific manner (Sillito et al, 1994;Yan and Suga, 1996;Zhang et al, 1997;Jen, 2000, 2007;Yan and Ehret, 2002;Malmierca and Nuñez, 2004;Castellanos et al, 2007;Ma and Suga, 2007). In the auditory system, focal cortical activation enhances the thalamic and midbrain processing of auditory information that is encoded by activated cortical neurons .…”

Stability of Neural Firing in the Trigeminal Nuclei under Mechanical Whisker Stimulation

“…Though there was a long discussion about what type of the neural code is employed by each individual neuron or neuron group, the growing experimental evidence shows that a same neuron may use different coding schemes (see reviews in [4, 5]). The temporal correlation of multiple cell discharges has been also found important for the information transmission to the cortex and its modulation by the corticofugal feedback (see, e.g., [6–8] and references therein).…”

“…Instantaneous frequencies of various rhythmic components can exhibit complex and irregular fluctuations, that is, the nonstationarity may be associated with higher frequencies as well. Our previous results [6] showed that the Fourier analysis is hardly applicable in such conditions. An alternative is the use of the wavelet technique, which can be successfully applied for analysis of the temporal structure of the neuronal spiking in a wide range of time scales [6, 17].…”

Stability switches, oscillatory multistability, and spatio-temporal patterns of nonlinear oscillations in recurrently delay coupled neural networks

“…This may happen due to corticofugal primary excitation of inhibitory interneurons. Recent experimental findings (Castellanos et al 2007;Malmierca et al 2009) indicate that a descending feedback significantly alters (modulates) the oscillatory and information processing properties of DCN. The functional coupling between the sensory stimulus and the neural response in DCN exhibits infra-slow oscillation (about 0.07 Hz).…”