@article {49119, title = {Dynamic cues for whisker-based object localization: An analytical solution to vibration during active whisker touch.}, journal = {PLoS Computational Biology}, volume = {14}, year = {2018}, month = {2018 Mar 27}, pages = {e1006032}, abstract = {

Vibrations are important cues for tactile perception across species. Whisker-based sensation in mice is a powerful model system for investigating mechanisms of tactile perception. However, the role vibration plays in whisker-based sensation remains unsettled, in part due to difficulties in modeling the vibration of whiskers. Here, we develop an analytical approach to calculate the vibrations of whiskers striking objects. We use this approach to quantify vibration forces during active whisker touch at a range of locations along the whisker. The frequency and amplitude of vibrations evoked by contact are strongly dependent on the position of contact along the whisker. The magnitude of vibrational shear force and bending moment is comparable to quasi-static forces. The fundamental vibration frequencies are in a detectable range for mechanoreceptor properties and below the maximum spike rates of primary sensory afferents. These results suggest two dynamic cues exist that rodents can use for object localization: vibration frequency and comparison of vibrational to quasi-static force magnitude. These complement the use of quasi-static force angle as a distance cue, particularly for touches close to the follicle, where whiskers are stiff and force angles hardly change during touch. Our approach also provides a general solution to calculation of whisker vibrations in other sensing tasks.

}, issn = {1553-7358}, doi = {10.1371/journal.pcbi.1006032}, author = {Vaxenburg, Roman and Wyche, Isis and Svoboda, Karel and Efros, Alexander L and Hires, Samuel Andrew} } @article {48560, title = {Mechanisms underlying a thalamocortical transformation during active tactile sensation.}, journal = {PLoS Computational Biology}, volume = {13}, year = {2017}, month = {2017 Jun 07}, pages = {e1005576}, abstract = {

During active somatosensation, neural signals expected from movement of the sensors are suppressed in the cortex, whereas information related to touch is enhanced. This tactile suppression underlies low-noise encoding of relevant tactile features and the brain{\textquoteright}s ability to make fine tactile discriminations. Layer (L) 4 excitatory neurons in the barrel cortex, the major target of the somatosensory thalamus (VPM), respond to touch, but have low spike rates and low sensitivity to the movement of whiskers. Most neurons in VPM respond to touch and also show an increase in spike rate with whisker movement. Therefore, signals related to self-movement are suppressed in L4. Fast-spiking (FS) interneurons in L4 show similar dynamics to VPM neurons. Stimulation of halorhodopsin in FS interneurons causes a reduction in FS neuron activity and an increase in L4 excitatory neuron activity. This decrease of activity of L4 FS neurons contradicts the "paradoxical effect" predicted in networks stabilized by inhibition and in strongly-coupled networks. To explain these observations, we constructed a model of the L4 circuit, with connectivity constrained by in vitro measurements. The model explores the various synaptic conductance strengths for which L4 FS neurons actively suppress baseline and movement-related activity in layer 4 excitatory neurons. Feedforward inhibition, in concert with recurrent intracortical circuitry, produces tactile suppression. Synaptic delays in feedforward inhibition allow transmission of temporally brief volleys of activity associated with touch. Our model provides a mechanistic explanation of a behavior-related computation implemented by the thalamocortical circuit.

}, issn = {1553-7358}, doi = {10.1371/journal.pcbi.1005576}, author = {Gutnisky, Diego Adrian and Yu, Jianing and Hires, Samuel Andrew and To, Minh-Son and Bale, Michael and Svoboda, Karel and Golomb, David} } @article {6268, title = {Aβ induces astrocytic glutamate release, extrasynaptic NMDA receptor activation, and synaptic loss.}, journal = {Proceedings of the National Academy of Sciences of the United States of America}, volume = {110}, year = {2013}, month = {2013 Jul 2}, pages = {E2518-27}, abstract = {

Synaptic loss is the cardinal feature linking neuropathology to cognitive decline in Alzheimer{\textquoteright}s disease (AD). However, the mechanism of synaptic damage remains incompletely understood. Here, using FRET-based glutamate sensor imaging, we show that amyloid-β peptide (Aβ) engages α7 nicotinic acetylcholine receptors to induce release of astrocytic glutamate, which in turn activates extrasynaptic NMDA receptors (eNMDARs) on neurons. In hippocampal autapses, this eNMDAR activity is followed by reduction in evoked and miniature excitatory postsynaptic currents (mEPSCs). Decreased mEPSC frequency may reflect early synaptic injury because of concurrent eNMDAR-mediated NO production, tau phosphorylation, and caspase-3 activation, each of which is implicated in spine loss. In hippocampal slices, oligomeric Aβ induces eNMDAR-mediated synaptic depression. In AD-transgenic mice compared with wild type, whole-cell recordings revealed excessive tonic eNMDAR activity accompanied by eNMDAR-sensitive loss of mEPSCs. Importantly, the improved NMDAR antagonist NitroMemantine, which selectively inhibits extrasynaptic over physiological synaptic NMDAR activity, protects synapses from Aβ-induced damage both in vitro and in vivo.

}, issn = {1091-6490}, doi = {10.1073/pnas.1306832110}, author = {Talantova, Maria and Sanz-Blasco, Sara and Zhang, Xiaofei and Xia, Peng and Akhtar, Mohd Waseem and Okamoto, Shu-ichi and Dziewczapolski, Gustavo and Nakamura, Tomohiro and Cao, Gang and Pratt, Alexander E and Kang, Yeon-Joo and Tu, Shichun and Molokanova, Elena and McKercher, Scott R and Hires, Samuel Andrew and Sason, Hagit and Stouffer, David G and Buczynski, Matthew W and Solomon, James P and Michael, Sarah and Powers, Evan T and Kelly, Jeffery W and Roberts, Amanda and Tong, Gary and Fang-Newmeyer, Traci and Parker, James and Holland, Emily A and Zhang, Dongxian and Nakanishi, Nobuki and Chen, H-S Vincent and Wolosker, Herman and Wang, Yuqiang and Parsons, Loren H and Ambasudhan, Rajesh and Masliah, Eliezer and Heinemann, Stephen F and Pi{\~n}a-Crespo, Juan C and Lipton, Stuart A} } @article {6889, title = {Tapered whiskers are required for active tactile sensation.}, journal = {eLife}, volume = {2}, year = {2013}, month = {2013 Nov 19}, pages = {e01350}, abstract = {

Many mammals forage and burrow in dark constrained spaces. Touch through facial whiskers is important during these activities, but the close quarters makes whisker deployment challenging. The diverse shapes of facial whiskers reflect distinct ecological niches. Rodent whiskers are conical, often with a remarkably linear taper. Here we use theoretical and experimental methods to analyze interactions of mouse whiskers with objects. When pushed into objects, conical whiskers suddenly slip at a critical angle. In contrast, cylindrical whiskers do not slip for biologically plausible movements. Conical whiskers sweep across objects and textures in characteristic sequences of brief sticks and slips, which provide information about the tactile world. In contrast, cylindrical whiskers stick and remain stuck, even when sweeping across fine textures. Thus the conical whisker structure is adaptive for sensor mobility in constrained environments and in feature extraction during active haptic exploration of objects and surfaces. DOI: http://dx.doi.org/10.7554/eLife.01350.001.

}, issn = {2050-084X}, doi = {10.7554/eLife.01350}, author = {Hires, Samuel Andrew and Pammer, Lorenz and Svoboda, Karel and Golomb, David} }