Abstract
BackgroundVisual neurons respond essentially to luminance variations occurring within their receptive fields. In primary visual cortex, each neuron is a filter for stimulus features such as orientation, motion direction and velocity, with the appropriate combination of features eliciting maximal firing rate. Temporal correlation of spike trains was proposed as a potential code for linking the neuronal responses evoked by various features of a same object. In the present study, synchrony strength was measured between cells following an adaptation protocol (prolonged exposure to a non-preferred stimulus) which induce plasticity of neurons' orientation preference.ResultsMulti-unit activity from area 17 of anesthetized adult cats was recorded. Single cells were sorted out and (1) orientation tuning curves were measured before and following 12 min adaptation and 60 min after adaptation (2) pairwise synchrony was measured by an index that was normalized in relation to the cells' firing rate. We first observed that the prolonged presentation of a non-preferred stimulus produces attractive (58%) and repulsive (42%) shifts of cell's tuning curves. It follows that the adaptation-induced plasticity leads to changes in preferred orientation difference, i.e. increase or decrease in tuning properties between neurons. We report here that, after adaptation, the neuron pairs that shared closer tuning properties display a significant increase of synchronization. Recovery from adaptation was accompanied by a return to the initial synchrony level.ConclusionWe conclude that synchrony reflects the similarity in neurons' response properties, and varies accordingly when these properties change.
Highlights
Visual neurons respond essentially to luminance variations occurring within their receptive fields
This unit's response for the adapting orientation doubled, while its response for the initially preferred orientation (0°) decreased 4-fold. These changes resulted in an apparent slide of the whole tuning curve toward the adapting orientation, an effect that will be referred to as adaptation-induced shift, or occasionally in a more concise manner, as shift
An attractive shift occurs when the peak of the tuning curve moves toward the adapting orientation, while a change in the opposite direction is defined as a repulsive shift
Summary
Visual neurons respond essentially to luminance variations occurring within their receptive fields. Synchrony strength was measured between cells following an adaptation protocol (prolonged exposure to a non-preferred stimulus) which induce plasticity of neurons' orientation preference. More than 90% of V1 neurons are well tuned to stimulus orientation [4] Such orientation selectivity is generally considered a fairly "hard-wired" property acquired before or at the time of eye opening and maintained by patterned visual experience [5]. It was reported in the adult cat that V1 neurons could temporarily shift their preferred orientation following prolonged exposure (adaptation) to a non-preferred (page number not for citation purposes). We took advantage of this phenomenon to examine how orientation tuning plasticity is related to time-correlated activity in V1 neuron pairs
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