Local field potential sharp waves with diversified impact on cortical neuronal encoding of haptic input

In cortical sensory processing, internal activity substantially impact the cortical response to any given input. But controlling for that internal activity is difficult since the thalamocortical network is high-dimensional, perpetually active and its state can change at a high pace. Here we report on a type of spontaneous local field potential sharp wave (LFP-SPW) in the somatosensory cortex (S1) and explore its impact on spiking responses evoked in S1 neurons by tactile stimulation. LFP-SPWs that preceded the tactile input could have major impacts, depressing the tactile responses in some neurons and enhancing them in others. In spontaneous data, in contrast, LFP-SPW events triggered short-lasting but massive neuronal activation in all neurons recorded with a subset of neurons initiating their activation up to 20 ms before the LFP-SPW onset. LFP-SPWs often coincided with ECoG-SPWs recorded at the cortical surface 2 mm away from the patch electrode, suggesting that the LFP-SPWs could be part of a more global cortical signal with a variable extent. When LFP-SPWs and ECoG-SPWs coincided, the impact of the LFP-SPW on the neuronal tactile response could change substantially, including inverting the impact to its opposite. Such diversified impacts of the SPWs on different S1 neurons are well in line with previous observations of cortical neurons displaying diverse, complementary, response types to given sensory inputs. These cortical SPWs had similar overall activity patterns as reported for hippocampal SPWs and may be a marker for a particular type of state change that possibly involves both hippocampus and neocortex.