Spatiotemporal Characteristics of Neuronal Sensory Integration in the Barrel Cortex of the Rat

Abstract

. Spatiotemporal characteristics of neuronal sensory integration in the barrel cortex of the rat. J Neurophysiol 93: 1450 -1467, 2005. First published October 20, 2004 doi:10.1152/ jn.00912.2004. In primary sensory cortices, neuronal responses to a stimulus presented as part of a rapid sequence often differ from responses to an isolated stimulus. It has been reported that sequential stimulation of two whiskers produces facilitatory modulations of barrel cortex neuronal responses. These results are at odds with the well-known suppressive interaction that has been usually described. Herein, we have examined the dependency of response modulation on the spatiotemporal pattern of stimulation by varying the spatial arrangement of the deflected vibrissae, the temporal frequency of stimulation, and the time interval between whisker deflections. Extracellular recordings were made from primary somatosensory cortex of anesthetized rats. Two contralateral whiskers were stimulated at 0.5 and 8 Hz at intervals ranging from 0 to Ϯ30 ms. Response interactions were assessed during stimulation of the principal and adjacent whiskers, first from the same row and second from the same arc. When tested at 0.5 Hz, 59% of single units showed a statistically significant suppressive interaction, whereas response facilitation was found in only 6% of cells. In contrast, at 8 Hz, a significant supralinear summation was observed in 19% of the cells, particularly for stimulations along an arc rather than along a row. Multi-unit recordings showed similar results. These observations indicate that most of the interactions in the barrel cortex during two-whisker stimulation are suppressive. However, facilitation can be revealed when stimuli are applied at a physiological frequency and could be the basis for internal representations of the spatiotemporal pattern of the stimulus.

Cross-Whisker Adaptation of Neurons in the Rat Barrel Cortex

“…Others have shown that layer 4 neurons adapt less than neurons of layer 2/3 Ego-Stengel et al, 2005). Based on the RI of the PW response only, we found here that layer 4 cells (Fig.…”

“…If diverging thalamic inputs are responsible for the AW response and unless the kinetics of short-term synaptic depression of the AW thalamocortical synapse differ from the kinetics for the PW inputs, we would expect, in contrast to our findings (Figs. 3, 4) and those of a recent extracellular study (Ego-Stengel et al, 2005), that the rates of adaptation to PW and AW stimulation would be similar. An additional synapse along the pathway and nonlinearity of the spike threshold would speed up adaptation at higher stages (Boudreau and Ferster, 2005).…”

Sensory integration across space and in time for decision making in the somatosensory system of rodents

“…During sensory stimulus perception, both processes take place concurrently to encode ''what'' information is available ''where'' within the array of sensory receptors. Previous studies in the somatosensory system showed that when multiple sensory receptors are nearsimultaneously (less than Ϸ80 ms) occupied to encode sensory information, stimulus-evoked activity is integrated sublinearly (2)(3)(4)(5)(6)(7)(8)(9). Such nonlinear interaction between sensory inputs is not unique to the somatosensory modality (10,11); nonetheless, its contribution to sensory perception and decision making is unknown.…”

“…The integration of the sensory information on this array is performed in many stages of the somatosensory axis (2,3,6,7) and has been shown to modulate the expression of plasticity (13)(14)(15)(16)(17). Moreover, the cortical readout of the incoming sensory information is necessary for active sensation (18)(19)(20) and has been suggested to be depressing with increasing number of simultaneously deflected whiskers (5) and with single-whisker (SW) deflections delivered with short delays (6,8,21). Considering the predominantly suppressive interaction between different whisker deflections across the whisker pad and time, it could be argued that because of the reduction in stimulus-evoked response after the first whisker deflection, secondary whisker deflections should minimally contribute to the performance of the animal.…”

Ce que les vibrisses disent au cerveau tactile

“…Cependant, lorsque les 25 vibrisses sont corrélées, la réponse informations en provenance de plusieurs vibrisses simultanément ou en léger décalage temporel. Ainsi, les neurones du cortex à tonneaux répondent préférentiellement à certaines séquences spatio-temporelles de stimulations multivibrissales impliquant de nombreuses vibrisses en s'écartant fortement des prédictions d'un simple modèle linéaire [7,[16][17][18].…”