Biology subjects

Upton, A. L.

Publications and source records attributed to Upton, A. L..

2 recordsLinked to original sources

bioRxiv2019

Complementary roles for parvalbumin and somatostatin interneurons in the generation of hippocampal gamma oscillations

Gamma-frequency oscillations (30-120 Hz) can be separated into fast (>60 Hz) and slow oscillations, with different roles in neuronal encoding and information transfer. While synaptic inhibition is important for synchronization across the gamma-frequency range, the role of distinct interneuronal subtypes in fast and slow gamma states remains unclear. Here, we used optogenetics to examine the involvement of parvalbumin (PV+) and somatostatin (SST+) expressing interneurons in gamma oscillations in the mouse hippocampal CA3 ex vivo. Disrupting either PV+ or STT+ interneuron activity, via either photo-inhibition or photo-excitation, led to a decrease in the power of cholinergically-induced slow gamma oscillations. Furthermore, photo-excitation of SST+ interneurons induced fast gamma oscillations, which depended on both synaptic excitation and inhibition. Our findings support a critical role for both PV+ and SST+ interneurons in slow hippocampal gamma oscillations, and further suggest that STT+ interneurons are capable of switching the network between slow and fast gamma states.

neuroscience↗

bioRxiv2018

Motor cortex can modulate somatosensory processing via cortico-thalamo-cortical pathway

The somatosensory and motor systems are intricately linked, providing several routes for the sensorimotor interactions necessary for haptic processing. Here, we used electrical and optogenetic stimulation to study the circuits that enable primary motor cortex (M1) to exert top-down modulation of whisker-evoked responses, at the levels of brain stem, thalamus and somatosensory cortex (S1). We find that activation of M1 drives somatosensory responsive cells at all levels, and that this excitation is followed by a period of tactile suppression, which gradually increases in strength along the ascending somatosensory pathway. Using optogenetic stimulation in the layer-specific Cre driver lines, we find that activation of layer VI cortico-thalamic neurons is sufficient to drive spiking in higher order thalamus, and that this is reliably followed by excitation of S1, suggesting a cross-modal cortico-thalamo-cortical pathway. Cortico-thalamic excitation predicts the degree of subsequent tactile suppression, consistent with a strong role for thalamic circuits in the expression of inhibitory sensorimotor interactions. These results provide evidence of a role for M1 in dynamic modulation of S1, largely under cortico-thalamic control.

neuroscience↗