Engaging and disengaging recurrent inhibition coincides with sensing and unsensing of a sensory stimulus

Abstract

Even simple sensory stimuli evoke neural responses that are dynamic and complex. Are the temporally patterned neural activities important for controlling the behavioral output? Here, we investigated this issue. Our results reveal that in the insect antennal lobe, due to circuit interactions, distinct neural ensembles are activated during and immediately following the termination of every odorant. Such non-overlapping response patterns are not observed even when the stimulus intensity or identities were changed. In addition, we find that ON and OFF ensemble neural activities differ in their ability to recruit recurrent inhibition, entrain field-potential oscillations and more importantly in their relevance to behaviour (initiate versus reset conditioned responses). Notably, we find that a strikingly similar strategy is also used for encoding sound onsets and offsets in the marmoset auditory cortex. In sum, our results suggest a general approach where recurrent inhibition is associated with stimulus ‘recognition' and ‘derecognition'.

Dynamic contrast enhancement and flexible odor codes

“…Activity-dependent synaptic depression between the sensory neurons and projections neurons 46,47 , interference due to stimulus-evoked OFF responses 25 or adaptation at the level of sensory neurons 48,49 can all contribute to the results observed in this study. Lastly, while we perturbed odor-evoked neural responses using variations in stimulus histories, other factors such as ambient conditions (humidity, temperature, air flow), presence of competing odorants, plasticity in central circuits have all been shown to introduce variations different from those that were examined here.…”

“…Odor stimulation: Odor stimuli were delivered using a standard procedure 24,25,35,36 . The following odor panel was used: hexanol, geraniol, 2-octanol, isoamyl acetate, benzaldehyde, citral, and apple.…”

“…An earlier work showed that following termination of an odor pulse, a nearly nonoverlapping set of neurons are activated(OFF ensemble neural response) 25 . These odor-evoked OFF responses are stimulus-specific.…”

“…Both patterns of spiking activities distributed across an ensemble of neurons [7][8][9][10][11][12][13][14] (i.e. 'the spatial code'), and the temporal features of these neural spike trains such as their synchronicity 15,16 , relative response latencies [17][18][19] , dynamics 4,[20][21][22][23][24][25][26] (i.e. 'the temporal code') have been shown to be important for sensory coding.…”

“…The insect olfactory system has been widely used for studying odor coding 9,[14][15][16][22][23][24][25][33][34][35][36] . In this system, an odor stimulus is detected by olfactory receptor neurons (ORNs) in the antenna and the transduced electrical signals get relayed downstream to the antennal lobe (analogous to the olfactory bulb in the vertebrates).…”